TOWN OF ATHERTON
2023 – 2031 HOUSING ELEMENT AND ZONING
CODE UPDATES
INITIAL STUDY/MITIGATED NEGATIVE DECLARATION
LEAD AGENCY:
TOWN OF ATHERTON
PLANNING DEPARTMENT
80 FAIR OAKS LANE
ATHERTON, CA 94027
CONTACT:
BRITTANY BENDIX, CONTRACT TOWN PLANNER
PREPARED BY:
METROPOLITAN PLANNING GROUP
1475 S. BASCOM AVENUE, SUITE 210 CAMPBELL, CA 95008
JULY 2024
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Town of Atherton
2023 – 2031 Housing Element and Zonning Code Updates i Initial Study/Mitigated Negative Declaration 2474551.1 14537.003
2023 – 2031 HOUSING ELEMENT AND ZONING CODE UPDATES
CEQA ENVIRONMENTAL CHECKLIST AND INITIAL STUDY
Initial Study Checklist
Project Title: 2023 – 2031 Housing Element and Zoning Code Update Lead agency name and
address:
Town of Atherton, Planning Department
80 Fair Oaks Lane
Atherton, CA 94027
Contact person and phone
number:
Brittany Bendix, Contract Town Planner
408-688-2432
[email protected]
Project Location: Townwide 6th Cycle Housing Sites:
Town of Atherton, California
San Mateo County
Project Sponsor/Owner: Town of Atherton, Planning Department 80 Fair Oaks Lane
Atherton, CA 94027
General Plan Designations: Townwide 6th Cycle Housing Sites: Single Family Residential Low Density; Parks and Open Space; Public, Quasi-Public and Educational.
Zoning: Townwide 6th Cycle Housing Sites: Single Family Residential (R-1A); Single Family Residential (R-1B); Public Facilities and Schools (PFS); and Park and Open Space (POS) districts.
Description of project: The proposed project is adoption of the 6th Cycle of the Town of Atherton’s Housing Element, a Zoning Ordinance Amendment to implement the policies and programs of the Housing Element, including adoption of objective design standards and development standards for multifamily housing (density, height, setbacks and parking, etc.), and adoption of an Inclusionary Housing Ordinance (collectively, the “Project Description”).
Surrounding land uses and
setting:
The Housing Element and Zoning Code updates encompasses the entire Town of Atherton, which is bounded by the cities of Menlo Park, Redwood City, Woodside, and unincorporated portions of San Mateo County. The Town’s primary existing land use is low-density residential development. The housing sites identified in the 2023 – 2031 Housing Element are surrounded by properties with General Plan designations of either Single Family Residential Low Density, Public Facilities and Schools, or Parks and Open Space.
Other public agencies whose
approval is required:
California Department of Housing and Community Development (HCD) California Native American
tribes traditionally and
culturally affiliated with the
project area that have
requested consultation:
The Town of Atherton carried out notification to the Amah Mutsun Tribal Band of Mission San Juan Bautista, Costanoan Rumsen Carmel Tribe, Indian Canyon Mutsun Band of Coastanoan, the Ohlone Indian Tribe, Wuksachi Indian Tribe/Eshom Valley Band, and the Tamien Nation in accordance with AB 52 and SB 18. None of the tribes requested consultation during the notification period.
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Town of Atherton
2023 – 2031 Housing Element and Zonning Code Updates iii Initial Study/Mitigated Negative Declaration 2474551.1 14537.003
2023 – 2031 6th CYCLE HOUSING ELEMENT UPDATE AND ZONING CODE UPDATE
CEQA ENVIRONMENTAL CHECKLIST AND INITIAL STUDY
TABLE OF CONTENTS PAGE #
1. INTRODUCTION ............................................................................................................................ 1
1.1. EXECUTIVE SUMMARY ............................................................................................................................... 1
1.2. PURPOSE AND INTENT .............................................................................................................................. 1
1.3. PUBLIC REVIEW ........................................................................................................................................ 2
2. PROJECT DESCRIPTION ................................................................................................................. 3
3. ENVIRONMENTAL FACTORS POTENTIALLY AFFECTED ............................................................ 23
4. DETERMINATION (TO BE COMPLETED BY LEAD AGENCY) ....................................................... 23
5. EVALUATION OF ENVIRONMENTAL IMPACTS .......................................................................... 25
5.1. AESTHETICS ........................................................................................................................................... 25
5.2. AGRICULTURAL AND FORESTRY RESOURCES ............................................................................................. 30
5.3. AIR QUALITY .......................................................................................................................................... 34
5.4. BIOLOGICAL RESOURCES ........................................................................................................................ 40
5.5. CULTURAL RESOURCES ........................................................................................................................... 52
5.6. ENERGY ................................................................................................................................................. 56
5.7. GEOLOGY AND SOILS .............................................................................................................................. 60
5.8. GREENHOUSE GAS EMISSIONS ................................................................................................................ 66
5.9. HAZARDS/HAZARDOUS MATERIALS ......................................................................................................... 71
5.10. HYDROLOGY AND WATER QUALITY .......................................................................................................... 77
5.11. LAND USE AND PLANNING ...................................................................................................................... 85
5.12. MINERAL RESOURCES ............................................................................................................................. 90
5.13. NOISE ................................................................................................................................................... 91
5.14. POPULATION AND HOUSING ................................................................................................................... 96
5.15. PUBLIC SERVICES .................................................................................................................................... 99
5.16. RECREATION ........................................................................................................................................ 103
5.17. TRANSPORTATION AND CIRCULATION .................................................................................................... 106
5.18. TRIBAL CULTURAL RESOURCES .............................................................................................................. 113
5.19. UTILITIES AND SERVICE SYSTEMS ........................................................................................................... 116
5.20. WILDFIRE ............................................................................................................................................. 121
5.21. MANDATORY FINDINGS OF SIGNIFICANCE (CAL. PUB. RES. CODE §15065) .............................................. 126
6. REFERENCE DOCUMENTS ......................................................................................................... 128 Town of Atherton
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LIST OF FIGURES
FIGURE 1: ATHERTON REGIONAL LOCATION MAP ...................................................................................... 13 FIGURE 2: GENERAL PLAN LAND USE DESIGNATIONS ................................................................................ 14 FIGURE 3: HOUSING ELEMENT UPDATE 6TH CYCLE SITES (1 OF 4) ............................................................. 15 FIGURE 4: HOUSING ELEMENT UPDATE 6TH CYCLE SITES (2 OF 4) ............................................................. 16 FIGURE 5: HOUSING ELEMENT UPDATE 6TH CYCLE SITES (3 OF 4) ............................................................. 17 FIGURE 6: HOUSING ELEMENT UPDATE 6TH CYCLE SITES (4 OF 4) ............................................................. 18 FIGURE 7: 6TH CYCLE SITES LAND USE DESIGNATIONS ............................................................................... 19 FIGURE 8: 6TH CYCLE SITES ZONING ............................................................................................................... 20 FIGURE 9: ZONING DESIGNATION.................................................................................................................. 21
LIST OF TABLES
TABLE 1: RHNA ALLOCATION ............................................................................................................................ 5 TABLE 2: NET RHNA – PROJECTED DWELLING UNITS .................................................................................... 6 TABLE 3: VACANT SITES ..................................................................................................................................... 7 TABLE 4: ADDITIONAL MULTI-FAMILY RESIDENTIAL OPPORTUNITY SITES ................................................ 8 Town of Atherton
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LIST OF ACRONYMS
ASSEMBLY BILL AB
ABOVE MEAN SEA LEVEL AMSL
BAY AREA AIR QUALITY MANAGEMENT DISTRICT BAAQMD
BEST MANAGEMENT PRACTICES BMP
BRITISH THERMAL UNIT BTU
CALIFORNIA AIR RESOURCES BOARD CARB
CALIFORNIA DEPARTMENT OF FISH AND WILDLIFE CDFW
CALIFORNIA DEPARTMENT OF FORESTRY AND FIRE PROTECTION CAL FIRE
CALIFORNIA DEPARTMENT OF TOXIC SUBSTANCES CONTROL DTSC
CALIFORNIA EMISSIONS ESTIMATOR MODEL CALEEMOD
CALIFORNIA ENDANGERED SPECIES ACT CESA
CALIFORNIA ENERGY COMMISSION CEC
CALIFORNIA ENVIRONMENTAL PROTECTION AGENCY ACAL-EPA
CALIFORNIA ENVIRONMENTAL QUALITY ACT CEQA
CALIFORNIA NATURAL DIVERSITY DATABASE CNDDB
CALIFORNIA REGISTER OF HISTORICAL RESOURCE CRHR
CALIFORNIA SURFACE MINING AND RECLAMATION ACT SMARMA
CARBON DIOXIDE EQUIVALENT CO2E
CARBON MONOXIDE CO
CLEAN WATER ACT CWA
COMMUNITY NOISE EQUIVALENT LEVEL CNEL
EMERGENCY VEHICLE ACCESS EVA
ENVIRONMENTAL IMPACT REPORT EIR
ENVIRONMENTAL SITE ASSESSMENT ESA
EXECUTIVE ORDER EO
FEDERAL EMERGENCY MANAGEMENT AGENCY FEMA
FEDERAL ENDANGERED SPECIES ACT FESA
FIRE HAZARD SEVERITY ZONES FHSZ
FLOOD INSURANCE RATE MAPS FIRM
GREENHOUSE GASES GHG
HISTORICALLY RECOGNIZED ENVIRONMENTAL CONDITIONS HREC
INITIAL STUDY IS
INSTITUTE OF TRANSPORTATION ENGINEERS ITE
LEAKING UNDERGROUND STORAGE TANK LUST
LEVEL OF SERVICE LOS
LOW IMPACT DEVELOPMENT LID
MEGAWATT HOURS MWH
METHANE CH3
METRIC TONS MT
MIGRATORY BIRD TREATY ACT MBTA
Town of Atherton
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MILLION GALLONS PER DAY MGD
MITIGATED NEGATIVE DECLARATION MND
MITIGATION MONITORING AND REPORTING PROGRAM MMRP
MOST LIKELY DESCENDENT MLD
NATIONAL POLLUTION DISCHARGE ELIMINATION SYSTEM NPDES
NATIONAL REGISTER OF HISTORIC PLACES NRHP
NATIVE AMERICAN HERITAGE COMMISSION NAHC
NITROGEN OXIDES NOX
NORTHWEST INFORMATION CENTER NWIC
NOTICE OF INTENT NOI
OFFICE OF PLANNING AND RESEARCH OPR
PARTICULATE MATTER PM
PEAK PARTICLE VELOCITY PPV
POUNDS PER DAY LBS/DAY
PUBLIC RESOURCES CODE PRC
REACTIVE ORGANIC GASES ROG
RECOGNIZED ENVIRONMENTAL CONDITIONS REC
REGIONAL TRANSPORTATION PLANNING AUTHORITY RTPA
REGIONAL WATER QUALITY CONTROL BOARD RWQCB
SENATE BILL SB
STATE OFFICE OF EMERGENCY SERVICES OES
STATE RESPONSIBILITY AREA SRA
STATEWIDE INTEGRATED TRAFFIC RECORDS SYSTEM SWITRS
STORMWATER POLLUTION PREVENTION PLAN SWPPP
TOXIC AIR CONTAMINANTS TAC
TRAFFIC ANALYSIS ZONE TAZ
TRAFFIC IMPACT STUDY TIS
TRANSPORTATION DEMAND MANAGEMENT TDM
TRIBAL CULTURAL RESOURCES TCR
UNITED STATES DEPARTMENT OF AGRICULTURE USDA
UNITED STATES FISH AND WILDLIFE SERVICE USFWS
UNREINFORCED MASONRY URM
VEHICLE MILES TRAVELED VMT
WILDLAND-URBAN INTERFACE WUI
Town of Atherton
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1. INTRODUCTION
1.1. EXECUTIVE SUMMARY
State Housing Element statutes (California Government Code [CGC] Sections 65580–65589.9) mandate that local governments adequately plan to meet the existing and projected housing needs of all economic segments of the community. The Town of Atherton 6th Cycle Housing Element Update 2023 – 2031 has been prepared to comply with these state statutes within the context of the physical and socio-economic conditions unique to Atherton and spans the eight-year planning period from 2023 – 2031. Furthermore, the Town of Atherton will update the Zoning Ordinance to implement the policies and programs contained in the 2023-2031 Housing Element. The Town is also considering adoption of an Inclusionary Housing Ordinance to effectuate the programs and policies. This environmental document analyzes those impacts should the Town wish to adopt that ordinance.
1.2. PURPOSE AND INTENT
This Initial Study has been prepared in conformance with CEQA (California Public Resources Code [PRC] Section 21000 et seq.); CEQA Guidelines (California Code of Regulations [CCR], Title 14, Division 6, Chapter 3, Section 15000 et seq.); and the rules, regulations, and procedures for implementation of CEQA, as adopted by the Town of Atherton.
In accordance with CEQA Guidelines Sections 15051 and 15367, the Town of Atherton is identified as the Lead Agency for the proposed project. Under CEQA (Public Resource Code Sections 21000-21177) and pursuant to CEQA Guidelines Section 15063, the Town is required to undertake the preparation of an Initial Study to determine if the proposed project would have a significant environmental impact.
This Initial Study/Mitigated Negative Declaration (IS/MND) for the Town of Atherton 6th Cycle Housing Element 2023 – 2031 and Zoning Code Update/Inclusionary Ordinance (hereinafter collectively referred to as the “project”) has been prepared by the Town of Atherton in full accordance with the procedural and substantive requirements of the California Environmental Quality Act (CEQA) and the CEQA Guidelines.
This IS/MND is intended to inform Town decision-makers, responsible agencies, interested parties and the general public of potential environmental impacts associated with adoption and implementation of the 2023 – 2031 Housing Element. This IS/MND is also intended to provide the CEQA-required environmental documents for all town, regional, and state approvals or permits that might be required to implement the proposed project.
CEQA Guidelines Section 15063(c) lists the following purposes of an Initial Study:
1. Provide the Lead Agency with information to use as the basis for deciding whether to prepare an Environmental Impact Report (EIR) or a Negative Declaration.
2. Enable an Applicant or Lead Agency to modify a project, mitigating adverse impacts before an EIR is prepared, thereby possibly enabling the project to qualify for a Negative Declaration.
3. Assist in the preparation of an EIR, if one is required.
4. Facilitate environmental assessment early in the design of a project.
5. Provide documentation of the factual basis for the finding in a Negative Declaration that a project will not have a significant effect on the environment.
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6. Eliminate unnecessary EIRs.
7. Determine whether a previously prepared EIR could be used with the project.
The Town of Atherton, as the lead agency, has conducted an Initial Study to determine the level of environmental review necessary for the proposed project. Consistent with Section 15070(b) of the CEQA Guidelines, the Initial Study identified potentially significant impacts, however, with implementation of mitigation measures identified herein, all potentially significant impacts would be reduced to less than significant. Based on the Environmental Checklist form and supporting environmental analysis contained herein, the proposed project’s impacts on the following issue areas would be less than significant with the implementation of mitigation: Air Quality, Biological Resources, Cultural Resources, Green House Gas, Noise, Transportation and Circulation, and Tribal Cultural Resources. As stated previously, all impacts would be less than significant after mitigation, and as such, the Town of Atherton as the lead agency has determined that a Mitigated Negative Declaration is the appropriate level of environmental review.
1.3. PUBLIC REVIEW
In accordance with CEQA and the state CEQA Guidelines, a 30-day public review period for the project begins on May 10, 2024 and will conclude on June 10, 2024. This IS/MND has been distributed to interested or involved public agencies, organizations, and private individuals for review. In addition, the IS/MND has been made available for general public review at the following location:
Town of Atherton
Planning Department
80 Fair Oaks Lane
Atherton, CA 94027
Planning Counter Hours: 8:00 am to 11:00 am, 1:00 pm to 4:00 pm, Tuesday/Thursday The document was also made available on the Town’s website at:
https://www.ci.atherton.ca.us/627/Housing-Element-Update During the public review period, the public also has the opportunity to provide written comments on the information contained within this IS/MND.
In reviewing the IS/MND and as articulated in Section 15204(a) of the CEQA Guidelines, affected public agencies and interested members of the public should focus on the sufficiency of the document in identifying and analyzing potential impacts on the environment from the proposed project, and ways in which the significant effects of the project can be avoided or mitigated. Pursuant to Section 15204(b) of the CEQA Guidelines, public agencies and persons should focus on the proposed finding that the project will not have a significant effect on the environment. If a public agency or person believes that the proposed project may have a significant effect, they should:
1. Identify the specific effect;
2. Explain why they believe the effect would occur; and
3. Explain why they believe the effect would be significant.
Finally, per Section 105204(c), reviewers should explain the basis for their comments, and should submit data or references offering facts, reasonable assumptions based on facts, or expert opinion supported by facts.
Town of Atherton
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Comments on the IS/MND should be submitted in writing and received by the Town of Atherton prior to the end of the 30-day public review period on June 10, 2024. Written comments should be submitted to:
Brittany Bendix, Contract Town Planner
Town of Atherton
Planning Department
80 Fair Oaks Lane
Atherton, CA. 94027
Phone: 408-688-2432
Email: [email protected]
2. PROJECT DESCRIPTION
The proposed Project consists of a comprehensive update to the Housing Element and Zoning Code Update/Inclusionary Housing Ordinance to implement the Housing Element programs.
State Housing Element Requirements
Since 1969, California has required that all cities and counties adequately plan to meet the housing needs of the community. These requirements are promulgated in Government Code Section 65580 et seq., which establish the State’s housing policies and identifies the responsibilities of a municipality to facilitate the improvement and development of housing to make adequate provisions for the housing needs of all economic segments of the community. These State policies establish the contents and process that local governments must follow in preparing their housing elements. Pursuant to Government Code Section 65583, the housing element must include:
1. Analysis of demographic, social, and housing characteristics, current and future housing needs due to population growth and change, and other factors affecting housing need;
2. Analysis of governmental and nongovernmental constraints that affect the development, maintenance, and improvement of housing for all income groups and people with disabilities;
3. Inventory of resources available to address the Town’s housing needs, including available land for housing, as well as the financial resources and administrative capacity to manage housing programs; and
4. Specific actions or programs to address the development, improvement, and conservation of housing to meet current and future needs. This includes goals, policies, and specific housing programs.
It is the State Department of Housing and Community Development's responsibility to administer and ensure local government compliance with Housing Element Law.
Project Location
The Town of Atherton is an incorporated town in San Mateo County, as shown Figure 1 Atherton Regional Location Map. Atherton is bounded by portions of unincorporated San Mateo County and the jurisdictions of Redwood City on the north, Menlo Park on the east and south, and Woodside on the west.
Existing Land Uses
The Town has an area of approximately 3,600 acres or 5.6 square miles; 89% of which is residential, 5% parks and open space, and 6% public and private schools and municipal facilities. The Town has been primarily developed with lower density residential uses, with no commercial or industrial uses. The Town of Atherton has minimal vacant available land for development.
Town of Atherton
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General Plan and Zoning Designations
The Town of Atherton contains three land use categories:
1. Single Family, Low Density
2. Parks and Open Space
3. Public, Quasi-Public, and Educational
The Single Family Residential Low Density General Plan designation is applied to all residential areas within the Town of Atherton and allows either one (1) or three (3) units per net acre. This land use designation allows a conventional single-family detached home with the additional use of an accessory dwelling unit (ADU), junior accessory dwelling unit (JADU), and other uses identified in the Town’s Municipal Code. The Town’s land use diagram is shown in Figure 2 Land Use Designations.
The corresponding zones to the Town’s General Plan land use designations are: Residential District R-1A and R-1B (single family residential), Park and Open Space District (POS), and Public Facilities and Schools District (PFS).
Description of Project
The project is the adoption and implementation of the Town of Atherton’s Housing Element and Zoning Code updates, and Inclusionary Housing Ordinance (“Project”). The 2023 – 2031 Housing Element update includes the following components, however, CEQA focuses on what aspect of the Housing Element will or could result in impacts on the environment:
Introduction: An introduction and overview of the 2023-2031 Housing Element purpose, process, definitions, RHNA Allocation and relationship to other elements. Assessment of Housing Needs: A discussion of the Town’s demographic and economic characteristics, housing and household descriptions including sales and rental prices, and special housing needs.
Fair Housing Assessment: This section provides an overview of Assembly Bill (AB) 686, a law designed to enforce fair housing throughout the state, an assessment of fair housing issues in the region, access to opportunities, disparate housing needs, a site inventory analysis, and findings of contributing factors to fair housing issues and implementation actions. Housing Resources: This section provides an inventory of sites suitable for residential development, an analysis of zoning that encourages and facilitates a variety of housing types, and adequate sites for emergency shelters, transitional and supportive housing, and farm worker housing. Constraints on Housing: This section identifies governmental and non-governmental constraints on housing in the Town of Atherton.
Review of the 2015-2022 Housing Element: This section reviews the effectiveness of the 5th Cycle Housing Element, progress in implementing it, and future opportunities for housing. Housing Goals, Quantified Objectives, and Policies: This section identifies the goals, objectives, and policies of the Housing Element.
Housing Programs: This section includes a list of the programs that will help achieve these goals and policies, and a summary of objectives with general timeframes in which those objectives might Town of Atherton
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be achieved, along with the agency responsible for implementing the program. Some programs of the Housing Element require implementation through Zoning Code modifications and are considered in this study.
Community Engagement: This section describes the efforts to engage the community in preparing the Housing Element update. During this planning period, the Town held several public meetings to discuss the proposed strategies with the community and solicit public input. The Town also partnered with 21 Elements and the Let’s Talk Housing effort to engage with current and potential beneficiaries of housing programs and services and their advocates. Appendices: The appendices summarize the 21 Elements survey analysis, ABAG/MTC Housing Needs Data Reports, AFFH Atherton Map, San Mateo County-wide housing needs, housing element site inventory form, Menlo College Faculty and Staff Housing Considerations, and correspondence from an interested property owner.
Regional Housing Needs Allocation (RHNA)
In accordance with Government Code §65584, projected housing needs for each city and county in the San Francisco Bay area region are prepared by the Association of Bay Area Governments (ABAG) and the Metropolitan Transportation Commission (MTC) under a process known as the Regional Housing Needs Assessment (RHNA). The RHNA allocates regional housing needs by income level among member jurisdictions.
California law established the planning period for the current RHNA from 2023 to 2031. ABAG’s RHNA allocation for Atherton during this period is 348 units. The 348 units for Atherton are out of the anticipated construction need of 441,176 additional housing units in the ABAG region. Atherton’s 348 units are distributed into Very Low Income, Low Income, Moderate Income, and Above Moderate-Income categories.
Each category is defined by households falling into a certain percentage of the Area Median Income (AMI) as shown in Table 1 RHNA Allocation.
TABLE 1: RHNA ALLOCATION
Income Category 6
th Cycle RHNA 10% Buffer Units Total Units Percent
Extremely Low / Very Low 94 9 103 26%
Low 54 5 59 16%
Moderate 56 6 62 18%
Above Moderate 144 14 158 40%
Total 348 34 382 100%
Comparison of Site Inventory and RHNA
In addition to the proposed goals, objectives, policies, and programs to meet its RHNA, Atherton factored in programs including, but not limited to, a Residential Medium overlay zone (RM-10) at 10 dwelling units per acre (du/ac) at eight sites within the R1-A zone (23 Oakwood, as included in the adopted Housing Element, and seven additional sites located at 999 Ringwood Avenue; 352, 318, and 296 Bay Road; and 175, 185 and 197 Ravenswood Avenue). The 2023-2031 Housing Element, as adopted, also includes programs to encourage development of vacant sites, accessory dwelling units (ADUs), lot splits (under the 2022 state law for urban lot splits; SB 9) and application of RM-20 and RM-40 overlay zones to private schools within the PFS zone, facilitating development at densities of 20 du/ac and 40 du/ac, respectively. Additional updates to the Housing Element and included in the Project, apply an RM-10 overlay on developed portions of sites within the POS zone, including the California Water Service site, the Circus Club, and the Gilmore House. The Town of Atherton
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total amount of projected net new housing units and their anticipated affordability levels are summarized in Table 2 Net RHNA Projected Dwelling Units.
TABLE 2: NET RHNA – PROJECTED DWELLING UNITS
Very Low
& Low Moderate Above Moderate Total New
Housing Units 0-80% AMI 81-120% AMI >120% AMI
Projected Dwelling Units
ADUs 168 84 28 280
Lot Splits (SB 9) 0 0 48 48
Vacant Sites 0 0 9 9
RM 10 (23 Oakwood) 4 0 12 16
PFS (Private Schools) 96 95 0 191
Multi-Family Residential
Opportunity Sites 17 34 34 85
Dwelling Unit Total 229 185 215 629
Total Net New Units Above or
below RHNA +81 +129 +71 +281
Anticipated Accessory Dwelling Units (ADUs)
The 2016 through 2020 updates to State law – Assembly Bill (AB) 2299 (2016), Senate Bill (SB) 1069 (2016), AB 494 (2017), SB 229 (2017), AB 68 (2019), AB 881 (2019), AB 587 (2019), SB 13 (2019), AB 670 (2019), AB 671 (2019), and AB 3182 (2020) – included changes pertaining to the allowed size of ADUs, permitting ADUs by right in at least some areas of a jurisdiction, and limits on parking requirements related to ADUs. More recent bills reduce the time to review and approve ADU applications to 60 days, remove lot size and replacement parking space requirements, and require local jurisdictions to permit junior ADUs (JADUs). On March 20, 2024, the Town adopted an ordinance to implement these laws along with local regulation that offer property owners the option to build ADUs that are subject to state law restrictions or build larger units if the developer provides greater setbacks and complies with additional requirements.
In 2021 and 2022, the Town of Atherton experienced the construction of 44 new ADUs. Based on this trend, the Town projects an average of 35 new ADUs per year over the next eight (8) years. The Housing Element includes programs to amend the zoning code to facilitate ADU and JADU construction. This IS/MND analyzes the environmental impacts of updating the Zoning Code to facilitate ADU and JADU construction as an approach to providing greater housing options available to low and very low-income households.
SB 9
Senate Bill 9 (SB 9) waives discretionary review and public hearings for building two homes on a parcel in a single-family zone and subdividing a lot into two that can be smaller than the previously required minimum size. In early 2022, the Town adopted an implementing ordinance consistent with state law to provide property owners clarity for the development opportunities under SB 9. The ordinance allows new lots to be created under the provisions of SB 9 to utilize the existing development standards for the base zoning district. A new residence built on a lot created through an SB 9 lot split can use the same setbacks, floor area ratio, building heights and other standards as provided for any existing lot in the same zoning district.
Town of Atherton
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It is projected that approximately 48 new above moderate-income housing units will result from lot splits and new housing development facilitated by the 2021 SB 9 State law (GC section 65852.21) during the 2023- 2031 Planning Period. There are 606 lots of an acre or greater in size, and Atherton received six (6) applications in 2022 and an additional six (6) inquiries that would result in a total of 23 new dwelling units.
There were 33 inquiries in 2023. Since September 2023 six SB 9 applications have been approved and recorded, and two additional applications are under review.
Vacant Sites
The Town of Atherton surveyed all Town parcels to determine adequate sites for housing. There is little vacant developable land in the Town, and most of the Town's land acreage is developed at existing General Plan densities. However, the Town did identify eight (8) undeveloped sites that it expects would provide single-family housing at the above-moderate income level. These sites are listed in Table 3 Vacant Sites.
TABLE 3: VACANT SITES
Site
ID
Lot
Acres APN Address Current Zoning
Max. Primary
Units under
current Zoning
Potential Net
New Primary
Units under SB-9
Reason not selected
as Opportunity Site
V1 1.42 070-343-100 97 Santiago Ave. R-1A 1 4
SB-9 application filed.
City Council decision
on 7/19/23.
V2 2.12 070-012-270 Polhemus Ave. R1-A 2 4
City Council decision
on 7/19/23. Discussed
as part of 290
Polhemus Ave.
V3 1.13 070-180-400 95 Faxon Road R1-A 1 4
Not fully vacant.
Improved with tennis
court, landscaping &
walkways. Serves as
extended rear yard of
adjacent property.
V4 0.95 070-180-340 12 Faxon Forest
Road R1-A 1 4
Not located on major
road or near public &
private services.
V5 0.85 070-180-350 16 Faxon Forest
Road R1-A 1 4
Not located on major
road or near public &
private services.
V6 1.00 070-180-290
No Address
(Located between 7 &
11 Faxon Forest Rd.)
R1-A 1 4
Not located on major
road or near public &
private services.
V7 1.78 070-131-010 15 Monte Vista Ave. R1-A 1 4
Not fully vacant.
Portion occupied by
existing house. Part of
a larger estate, approx.
12.6 acres.
V8 0.98 070-180-020 25 Monte Vista Ave. R1-A 1 4
Not fully vacant.
Portion occupied by
existing house. Part of
a larger estate, approx.
12.6 acres.
TOTAL PRIMARY HOUSING UNITS 9 32
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Residential Sites Inventory
An important component of the Town of Atherton Housing Element is the identification of sites for future housing development, and an evaluation of the adequacy of those sites in fulfilling the Town’s share of regional housing needs. To accomplish this, all town parcels were surveyed to determine their development capacity. Due to limited vacant and underutilized sites in Atherton, the Town has selected candidate sites for rezoning. Each site was analyzed in light of the development standards for its proposed zoning designation and standards identified in the Housing Element Update. All parcels in Atherton were evaluated through a process of elimination based on required criteria set by the State (HCD).
Multi-Family Residential Opportunity Sites
The Town has identified an additional seven (7) sites as multi-family residential opportunity sites within the R1-A zone and the three (3) sites zoned as POS for inclusion in the Housing Element update. These sites are in addition to the multi-family sites already included in the Atherton Housing Element adopted on January 31, 2023. The Town is proposing to either rezone or adopt an overlay zone on these seven additional properties to facilitate multi-family housing at a density of up to 10 dwelling units per acre (du/ac). The Housing Element does not institute the rezoning or zoning overlay, but rather these are recommended legislative actions that would be implemented after adoption and certification of the Housing Element update. This document analyzes the impact on the environment should those additional sites be developed at their maximum allowable capacity. A list of sites for multi-family residential opportunities is identified in Table 4. Potential units were calculated and would yield a total of 85 units on approximately 8.54 acres of land. The Zoning Code changes necessary to facilitate development of these additional multi-family residential sites and the sites included in the adopted housing element are discussed in the next section.
TABLE 4: ADDITIONAL MULTI-FAMILY RESIDENTIAL OPPORTUNITY SITES Site ID Address Lot
Acres Existing Zoning Proposed Zoning Overlay
Proposed Net Residential
Units from Zoning Overlay
MFO-1 999 Ringwood Ave. 0.90 R-1A RM-10 9
MFO-2 352 Bay Rd. 0.92 R-1A RM-10 9
MFO-3 318 Bay Rd. 0.94 R-1A RM-10 9
MFO-4 296 Bay Rd. 0.93 R-1A RM-10 9
MFO-5 175 Ravenswood 1.1 R-1A RM-10 11
MFO-6 185 Ravenswood 1.1 R-1A RM-10 11
MFO-7 197 Ravenswood 1 R-1A RM-10 10
MFO-8 Gilmore House 0.90 POS RM-10 9
MFO-9 Circus Club 0.50 POS RM-10 5
MFO-10 Cal Water 0.25 POS RM-10 3
TOTALS 8.54 85
Zoning Code Changes
Implementation of the Housing Element as previously adopted and including updates would effectuate the following zoning changes to the Atherton Zoning Code:
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Ministerial Review. The Project will facilitate ministerial review and approval for all housing sites, unless they otherwise require discretionary actions.1 Pursuant to CEQA Guidelines Section 15268, ministerial projects are exempt from the requirements of CEQA. In the event that a project that is facilitated by the Housing Element and Zoning Code updates is eligible for ministerial review, any mitigation measures identified in this Initial Study will not apply. Additionally, if the site remains privately owned, the Town cannot conduct mitigation on its own. In an effort to ensure baseline mitigations, the Town may consider incorporating broad mitigations into the Zoning Code or other Town policies. For example, Mitigation Measure AQ-1 as included in this study applies Best Management Practices established by the Bay Area Air Quality Management District (BAAQMD) for construction activities to all sites.
RM-10 Overlay Zones. Implementation of the Housing Element would institute an overlay zone on three sites located within the Public Open Space (POS) zone and eight sites within the Residential District R1-A zone:
o Public Open Space (POS) Sites: The Project proposes an amendment to the Town’s Zoning Code of an RM-10 overlay to permit multifamily residential uses in the developed areas of properties in the Public Open Space (POS) zone. This includes the following: approximately
0.9 acres of Holbrook Palmer Park, occupied by the Gilmore House (MFO-8); approximately
0.5 acres of developed portions of the Circus Club (MFO-9); and approximately 0.25 acres of portions of the California Water Service site (MFO-10) at Bear Gulch Reservoir that are currently developed with offices or an ancillary off-street parking area.
The existing standards for development in the POS zone include a height limit of 34 feet, maximum lot coverage of 20 percent gross lot area, minimum front and rear yard setbacks of 60 feet and minimum side yard setbacks that range according to lot width from 10 to 50 feet. Caretaker housing is permitted with approval of a conditional use permit. o 23 Oakwood: The adopted Housing Element proposes an amendment to the Town’s Zoning Code of an RM-10 overlay zone to permit multifamily residential uses at 23 Oakwood Boulevard, a site in the R1-A zone.
The existing standards for development in the R1-A zone include a height limit of 34 feet, maximum floor area ratio of 18 percent, minimum front and rear yard setbacks of 60 feet and minimum side yard setbacks that range according to lot width from 10 to 50 feet. Multifamily housing is not permitted in R1-A zone. o Additional R-1 Sites: As described above, the Town has identified seven (7) additional sites as multi-family residential opportunity sites for inclusion in the Housing Element Update.
The Town is proposing to either rezone or adopt an overlay zone on these seven additional properties to facilitate multi-family housing at a density of up to 10 dwelling units per acre (du/ac). All seven sites are within the R1-A zone.
RM-10 Zoning Code updates would facilitate ministerial approval for on-site multifamily in-fill development at a maximum density of 10 du/ac, a maximum building height of up to 4 stories or 40 feet, and minimum setbacks no less than 10 feet to accommodate the 10 du/ac density and 1 If a project that is facilitated by the Housing Element and Zoning Code updates requires discretionary actions, it may be an indication that the project requires further CEQA analysis and exceeds the scope of impacts analyzed in this Initial Study. This determination will be made upon submittal of the project and preliminary review.
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accessory buildings, structures and parking. The Project also includes adoption of Objective Design Standards. Additional landscaping standards are included to supplement the Town’s existing landscaping requirements and the perception of the building mass from scenic vistas. RM-20 and RM-40 Overlay Zones: Implementation of the Housing Element would institute an overlay zone on six sites located within the Public Facilities and Schools District (PFS) zone:
o Menlo College – 1000 El Camino Real; Site 1: The existing O’Brien surface parking lot at the southwest corner of El Camino Real and Alejandra Avenue is approximately 75,000 square feet (1.7 acres) in area. The site is level and currently contains a paved parking lot. The College has expressed interest in developing 60 dwelling units at this site. The lot is surrounded by mature vegetation. Development anticipated by the Town’s adopted Housing Element includes the construction of a multi-family housing building with podium parking at ground level and three-stories of housing above, or below grade parking. Parking provided by the existing surface parking lot would be replaced to meet the needs of the college. o Menlo College – 1000 El Camino Real; Site 2: There are four residences located on the campus in World War II era houses that are currently utilized for faculty housing (Apartment 8B). Demolition of these residences would accommodate 30 apartment units, resulting in a net increase of 26 multifamily housing units.
o Menlo College – 1000 El Camino Real; Site 3: The College has identified a site that is viable for a multi-story multi-family development of approximately 40 units. The site, near the Administration Building, is currently used as parking. The school has indicated that additional parking could be developed near the entry to the College, off El Camino Real. o Menlo School – 50 Valparaiso Avenue; Site 1: A surface parking located at the southwest corner of the campus with frontage on Valparaiso Avenue and the school entry drive, approximately 56,000 square feet (sf.) would have an overlay zone that permits 20 dwelling units per acre with objective design standards. This site would yield 25 dwelling units. o Menlo School – 50 Valparaiso Avenue; Site 2: An approximately 44,000 sf. surface parking lot located at the southeast corner of the campus, with a frontage on Valparaiso Avenue and the school entry drive. With an overlay zone that permits 20 dwelling units per acre with objective design standards, this site could yield approximately 20 dwelling units. o Sacred Heart – 150 Valparaiso Avenue: There are currently five (5) apartment units on the campus and housing for retired Nuns at Oakwood. The school anticipates this facility being renovated in the future to accommodate faculty housing which would be allowed under the PFS Zoning with an amendment for a density of 20 units per acre. The site would yield approximately 20 units.
Existing PFS zone development standards require multi-family residential uses that can accommodate housing for very low- and low-income households associated with the primary nonresidential use of property on the same site. Where a master plan for a private school has been prepared and filed with the Town for public record that includes multifamily residential uses, such uses shall be subject to Planning Commission public hearing and review of the location, size, proximity to heritage trees and environmental aspects of the project; but shall not result in the denial of the use. The Atherton General Plan and Zoning Code do not have a stated allowed density Town of Atherton
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for PFS sites, and require a maximum height of 34 feet, minimum 60-foot setbacks from the front and rear property lines, and minimum side yard setbacks of no less than 50 feet.
Zoning Code amendments necessary to facilitate ministerial multifamily development at the PFS sites include establishment of overlays that facilitate densities of 20 du/ac and 40 du/ac.
Development standards would allow a maximum height of 48 feet or 4 stories and require setbacks from adjacent properties no less than 20 feet for main buildings. The Project also includes adoption of Objective Design Standards. Additional landscaping standards are included to supplement the Town’s existing landscaping requirements and the perception of the building mass from scenic vistas, parks and open spaces.
On-Site Parking: The Town does not have on-site parking requirements; therefore, the Town must adopt on-site parking standards to accommodate potential multifamily developments. Analysis of increased trips attributed to multifamily housing is addressed in Section 5.17 Transportation and Circulation of this report.
Additional Housing Programs: Implementation of the Housing Element and Zoning Code updates result in broader housing options and choices within the Town. The following programs address additional state programmatic updates to Affirmatively Further Fair Housing and address environmental injustices:
o Allowing Permanent Supportive Housing by-right in use zones where multi-family and mixed-uses are permitted; and a by-right allowance for 100% affordable housing that has 25%, or 12 units, of permanent supportive housing where multi-family or mixed-use housing is permitted.
o Permitting Low Barrier Navigation Centers in zones where multi-family and mixed uses are permitted.
o Permitting mobile homes and manufactured housing on a permanent foundation under the same manner as single-family homes.
o Allowing group homes for seven (7) or more residents in any district where residential uses are permitted.
o Permitting shelters, and amending their parking requirements, without discretionary action. General Plan Alignment: The Project includes an update to the Zoning Code and Subdivision Ordinance to align with General Plan’s stated minimum lot area per dwelling of 13,500 square feet (0.31 acres) in the R1-B zone.
Inclusionary Housing Ordinance
Implementation of the Housing Element includes the adoption of an inclusionary housing ordinance that would require the construction of affordable housing units or payments of an in-lieu fee. For multifamily housing developments, the program would require either a minimum of 20 percent of the new units included in the development to be affordable to lower-income households or payment of an in-lieu fee. For new single-family developments, the program would require either construction of an affordable deedrestricted ADU or JADU, or payment of an in-lieu fee. The collection of impact fees related to the inclusionary housing program would support development of affordable housing opportunities within the Town.
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General Plan Amendment
The Housing Element update is an amendment to the Town’s General Plan. However, to implement the suggested height limits within the Zoning Code update, the Project includes an amendment to Policy LU-1.4:
Structure higher than 34 feet shall be prohibited. As described above, the maximum height limit included in the Project facilitates a building of 48 feet tall in the PFS zone.
Additional Sites
In the event additional sites are considered for multi-family development, the appropriate environmental document will be prepared and circulated for public review prior to re-zoning and/or amendments to the Housing Element being considered or approved by the Town.
Required Discretionary Actions
Adoption of the 2023 – 2031 Housing Element, Zoning Code Amendments (including objective design standards and development standards for multifamily housing) and an Inclusionary Housing Ordinance.
Other Public Agency Review
Approval of the Housing Element by the California Department of Housing and Community Development (HCD).
California Native American Tribal Consultation
In accordance with AB 52 (PRC Section 21084.2), lead agencies are required to initiate consultation with a tribe with traditional and/or cultural affiliations in the geographic area where a subject project is located if a project may cause a substantial adverse change in the significance of a tribal cultural resource. Should the tribe respond requesting formal consultation, the lead agency must work with the tribe or representative thereof to identify potential impacts and develop avoidance or mitigation measures to reduce potential impacts to tribal cultural resources.
In addition, SB 18 (GC Section 65352.3) requires lead agencies to contact and consult with California Native American tribes prior to amending or adopting any general plan, specific plan, or designating land as open space. In accordance with AB 52 and SB 18, notification of the proposed project was mailed to the following tribes on June 20, 2023:
Amah Mutsun Tribal Band of Mission San Juan Bautista
Costanoan Rumsen Carmel Tribe
Indian Canyon Mutsun Band of Costanoan
The Ohlone Indian Tribe
Wuksachi Indian Tribe/Eshom Valley Band
Tamien Nation
No responses to the notification or requests to consult on the project were received.
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FIGURE 1: ATHERTON REGIONAL LOCATION MAP
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FIGURE 2: GENERAL PLAN LAND USE DESIGNATIONS
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FIGURE 3: HOUSING ELEMENT UPDATE 6
TH CYCLE SITES (1 OF 4)
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FIGURE 4: HOUSING ELEMENT UPDATE 6
TH CYCLE SITES (2 OF 4)
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FIGURE 5: HOUSING ELEMENT UPDATE 6
TH CYCLE SITES (3 OF 4)
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FIGURE 6: HOUSING ELEMENT UPDATE 6
TH CYCLE SITES (4 OF 4)
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FIGURE 7: 6
TH CYCLE SITES LAND USE DESIGNATIONS
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FIGURE 8: 6
TH CYCLE SITES ZONING
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FIGURE 9: ZONING DESIGNATION
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3. ENVIRONMENTAL FACTORS POTENTIALLY AFFECTED
The environmental factors checked below would be potentially affected by this project, involving at least one impact that is a "Potentially Significant Impact Unless Mitigation is Incorporated" as indicated by the checklist on the following pages.
Aesthetics Hazards & Hazardous Materials Recreation
Agricultural & Forestry Hydrology / Water Quality Transportation / Traffic X Air Quality X Land Use / Planning Tribal Cultural Resources X Biological Resources X Mineral Resources Utilities / Service Systems Cultural Resources X Noise X Wildfires
Geology / Soils Population / Housing Mandatory Findings of Greenhouse Gases X Public Services Significance
4. DETERMINATION (TO BE COMPLETED BY LEAD AGENCY)
The CEQA Initial Study (IS) Checklist and written explanations are provided in Section 4 below. The Initial Study Checklist and narrative indicate the level of significance of the potential environmental effects of the proposed project upon each of the noted environmental resources. On the basis of this initial evaluation:
I find that the proposed project COULD NOT have a significant effect on the environment. A NEGATIVE DECLARATION will be prepared.
I find that although the proposed project could have a significant effect on the environment, there will not be a significant effect in this case because revisions in the project have been made by or agreed to by the project proponent. A MITIGATED NEGATIVE DECLARATION will be prepared.
X
I find that the proposed project MAY have a significant effect on the environment, and an ENVIRONMENTAL IMPACT REPORT is required.
I find that the proposed project MAY have a "potentially significant impact" or "potentially significant unless mitigated" impact on the environment, but at least one effect 1) has been adequately analyzed in an earlier document pursuant to applicable legal standards, and 2) has been addressed by mitigation measures based on the earlier analysis as described on attached sheets. An ENVIRONMENTAL IMPACT REPORT is required, but it must analyze only the effects that remain to be addressed.
I find that although the proposed project could have a significant effect on the environment, because all potentially significant effects (a) have been analyzed adequately in an earlier EIR or NEGATIVE DECLARATION pursuant to applicable standards, and (b) have been avoided or mitigated pursuant to that earlier EIR or NEGATIVE DECLARATION, including revisions or mitigation measures that are imposed upon the proposed project, nothing further is required. 7/17/24
Brittany Bendix, Contract Town Planner Date
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5. EVALUATION OF ENVIRONMENTAL IMPACTS
The following discussion addresses the potential level of impact relating to each aspect of the environment.
5.1. AESTHETICS
Would the project:
Potentially
Significant
Impact
Less Than
Significant
with
Mitigation
Less than
Significant
Impact
No
Impact
a) Have a substantial adverse effect on a scenic
vista?
b) Substantially damage scenic resources, including,
but not limited to, trees, rock outcroppings, and
historic buildings within a state scenic highway?
c) In non-urbanized area, substantially degrade the
existing visual character or quality of public views
of the site and its surroundings? (Public views are
those that are experienced from publicly
accessible vantage point). If the project is in an
urbanized area, would the project conflict with
applicable zoning and other regulations governing
scenic quality?
d) Create a new source of substantial light or glare
which would adversely affect day or nighttime
views in the area?
Sources: Town of Atherton General Plan 2019; Town of Atherton General Plan 2019 Update Project, Draft Initial Study/ Mitigated Negative Declaration; Town of Atherton Green Infrastructure Plan, September 18, 2019; and Santa Cruz Mountains Bioregional Council website; City of Menlo Park’s 2016 General Plan Aesthetics Setting
The Town of Atherton is situated in the San Francisco “Peninsula” region and bounded by the Redwood City to the north, Menlo Park to the east and south, and Woodside to the west. The Town of Atherton is relatively level, except for areas that are west of Alameda de las Pulgas. The Santa Cruz Mountains are situated west of Atherton, reaching a height greater than 3,000 feet. The Atherton Channel is the primary waterway throughout the Town that flows eastward to Marsh Road, where it eventually combines with the Bayfront Canal.
As described in the Town’s General Plan, Atherton has evolved from country estates into residential communities consisting of lots from one-third of an acre and larger. Atherton’s character maintains a semi-rural environment in which streets are limited to two lanes maximum, except for El Camino Real. Important visual features are the tree lined streets that are found throughout the Town.
Atherton’s native trees, particularly the heritage oak trees, are preserved and maintained with high priority.
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The Junipero Serra Freeway (Interstate 280) is a formally designated State Scenic Highway, but it is located west of the Town limits. According to the Circulation Element, it is the Town’s policy to designate all streets and highways located in the Town as scenic routes. The Housing Element Update includes multifamily sites with frontage onto Ravenswood Avenue, Ringwood Avenue, and Bay Road, all of which are streets within the boundary of the City of Menlo Park. The City of Menlo Park’s 2016 General Plan does not identify these streets as scenic or vista corridors.
Applicable General Plan Goals, Objectives and Policies
The Town of Atherton’s General Plan sets forth goals, objectives, and policies intended to improve and enhance aesthetics, those particularly relevant to the 2023 – 2031 Housing Element Update include the following:
Land Use Element
Goal LU-1: To preserve the Town’s character as a scenic, semi-rural, thickly-wooded residential area with abundant open space.
Objective LU-1.2: To limit the nature of land uses to those which are compatible with the overall land use planning goal LU-1.
Objective LU-1.3: To retain the quality of life, character and existing in the Town’s residential neighborhoods.
Policy LU-1.2 The development of high density and/or high-rise residential structures or commercial uses of any kind would destroy the scenic, semi-rural and open space character of the Town, and is, therefore, prohibited.
Policy LU-1.3 Minimum new lot sizes in hillside areas (defined as areas with average cross slopes greater than 20 percent) shall be related to the slope and shall not be less than:
0 – 19% cross slope is a minimum lot size of 1 acre
20 – 34.9% average cross slope is a minimum lot size of 2 acres 35% + average cross slope is a minimum lot size of 5 acres. Policy LU-1.4 Structures higher than 34 feet shall be prohibited. Policy LU-1.5 Proposed residential subdivisions as well as proposals to replace existing homes, shall adhere to the following design criteria:
A. Maintenance of existing neighborhood environments shall be promoted by the design of the subdivision and subdivision improvements. Designs shall be visually harmonious and compatible with neighborhood character.
B. Adequate drainage and off-street parking shall be provided. Street lighting shall be kept to a minimum. Temporary or guest on-street parking areas shall be minimized.
C. Uniformity of lot design should be avoided by using such techniques as meandering streets.
D. Trees shall be preserved to the maximum extent feasible while allowing for construction within established parameters for setbacks and lot coverage in accordance with the Municipal Code chapter regulating removal of and damage to heritage trees.
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E. Residential land uses shall be designed in accordance with the density, floor area ratio, height, bulk and other standards established by the Town.
F. All utilities installed in conjunction with new subdivisions shall be placed underground.
G. Residential land uses shall be consistent with the goals, objectives and policies of the Atherton General Plan Housing Element.
H. Accessory dwelling units are permitted when consistent with adopted standards.
I. Privacy is a factor which shall be incorporated into subdivision, subdivision improvements and home design.
J. The Town allows minimum lot size subdivisions only where such minimum lot sizes do not significantly degrade established levels of privacy, wooded areas, and/or the open space environment.
K. Residential improvements shall follow the model policies developed for the San Mateo Countrywide Stormwater Pollution Prevention Program and the Town’s Green Infrastructure Plan 6 to minimize the discharge of pollutants into the waterways. Policy LU-1.6 The Town shall continue to preserve the open space characteristics of existing schools, churches, and park facilities.
Policy LU-1.7 Land uses which diminish the open space character of the Town, such as commercial and high-density residential uses, shall be prohibited. Policy LU-1.8 Maximize preservation of heritage trees and existing trees within a development site to the greatest degree feasible, consistent with the Heritage Tree Ordinance and Tree Preservation Standards and Specifications. Require new development to comply with the Town’s requirements for tree protection, removal, and replacement.
Policy LU-1.9 Identify and implement green infrastructure opportunities for stormwater management including those recognized in the Town’s Green Infrastructure Plan. Green infrastructure facilities should reflect the Town’s visual semi-rural character.
Goal LU-3: Assure development of private schools continue to reflect the Town’s character as a scenic, semi-rural, thickly-wooded residential area.
Circulation Element
Objective CIR-1.2: To preserve the streets of Atherton as scenic routes. Policy CIR-1.9 All streets and highways in the Town of Atherton shall be preserved as scenic routes.
Open Space and Conservation Element
Goal OSC-1: Protect both publicly and privately held open space lands from deterioration of their semi-rural charm, scenic value, and environmental equilibrium.
Objective OSC-1.1: Preserve presently existing open space, wildlife, and vegetation.
Objective OSC 1.2: Prevent developmental encroachment on open space and sensitive environmental resources.
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Policy OSC-1.1 The Town shall endeavor to protect scenic resources, significant stands of natural vegetation, wildlife habitat, public safety, and significant archaeological resources, both publicly and privately held.
Aesthetics Impact Discussion
5.1(a, c) (Effect a Scenic Vista, Degrade Scenic Quality) Less Than Significant Impact: The Housing Element Update would not result in direct construction of housing, but the Zoning Code amendments would facilitate future housing development on undeveloped, developed, and infill sites in the incorporated Town limits. Future development of sites identified in the 2023 – 2031 Housing Element would occur in developed areas of the Town and have the potential to change the surrounding visual character by introducing new structures, landscaping, paved surfaces, frontage improvements, as well as through removal of existing vegetation and trees.
Town-recognized scenic resources adjacent to sites identified in the Housing Element include roads, trees, and open space areas. The Town’s General Plan does not identify designated scenic vistas, but it designates roads and highways as scenic routes. The Scenic Roadways section of the Circulation Element generally describes scenic corridors as “the visual land area outside the road right-of-way” and the “view from the road.”
To protect these scenic qualities, the Town General Plan and Municipal Code include design criteria to minimize impacts to these scenic resources. Specifically, the Zoning Code requires a maximum height of 34 feet and a minimum front setback of 60 feet for main buildings in all zoning districts.
Additionally, the Town’s Heritage Tree Ordinance has the stated purpose of preserving the scenic beauty of the Town and provides requirements for the removal or replacement of trees of a certain maturity. Although the Town also has landscaping screening requirements for new construction, the Town does not currently require landscaping within the front yard along street frontages. Therefore, existing standards provide for the visibility of development from the road.
The Project includes Zoning Code modifications that allow for the development of buildings at a maximum height of 48 feet, with minimum setbacks from property line frontages of 10 feet, and that require landscape screening along all property lines, including the street frontage. The height and front setback requirements of the Zoning Code modifications will result in a closer and taller building form visible from the road; however, the application of landscape screening standards along the property frontage will mitigate the changes to have less than a significant impact.
The Project does not include amendments to the Town’s Heritage Tree ordinance to facilitate housing production, except for ADUs permitted explicitly by state law. Pursuant to State law, the Town cannot deny an ADU of 800 square feet or less, that removes a heritage tree or provides no setback from the street frontage. However, to incentive ADU development that complies with the Town’s setbacks for accessory buildings and maintain its scenic corridors, the Project allows for larger ADUs, up to 1,200 square feet, and ADUs located above detached garages. The Town has also updated its Master Fee Schedule to waive fees for ADUs that comply with the Town’s local development standards.
5.1(b) (Scenic Resources from Designated Scenic Highway) No Impact: The proposed future developments will not damage scenic resources including, but not limited to, trees, rock outcroppings, and historic buildings within a designated state scenic highway. Though Junipero Serra Freeway (Interstate 280) is a formally designated scenic highway located west of the Town of Atherton, none of the identified housing sites are adjacent to the Junipero Serra Freeway. Therefore, Town of Atherton
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the identified sites are not within distances to substantially damage scenic resources, including, but not limited to, trees, rock outcroppings, and historic buildings within a state scenic highway. Thus, the 2023 – 2031 Housing Element Update would result in no impact related to scenic resources within a designated state scenic highway.
5.1(d) (Light and Glare) Less Than Significant Impact: The housing sites identified in the 2023 – 2031 Housing Element Update are located in areas of existing residential development, public facilities, and schools that contribute sources of light within the Town. Outdoor lighting introduced by future development on properties with two or more dwelling unit would be required to comply with Section 17.53.060(B)(3) of the Municipal Code which states, “Exterior building and landscape lighting shall be directed downward, have a shielded light source and be designed so that the light is not directed off site. Up-lighting of trees and permanent lighting within trees is prohibited.” With implementation of the Atherton Municipal Code objective building and design standards, impacts resulting from a new source of substantial light or glare, which would adversely affect day or nighttime views in the area, will be less than significant.
Mitigation Measure(s): None Required.
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5.2. AGRICULTURAL AND FORESTRY RESOURCES
Would the project:
Potentially
Significant
Impact
Less Than
Significant
with
Mitigation
Less Than
Significant
Impact
No Impact
a) Convert Prime Farmland, Unique
Farmland, or Farmland of Statewide
Importance (Farmland), as shown on the
maps prepared pursuant to the Farmland
Mapping and Monitoring Program of the
California Resources Agency, to nonagricultural use?
b) Conflict with existing zoning for
agricultural use, or a Williamson Act
contract?
c) Conflict with existing zoning for, or cause
rezoning of, forest land (as defined in
Public Resources Code section 12220(g)),
timberland (as defined by Public Resources
Code section 4526), or timberland zoned
Timberland Production (as defined by
Government Code section 51104(g))?
d) Result in the loss of forest land or
conversion of forest land to non-forest
use?
e) Involve other changes in the existing
environment which, due to their location
or nature, could result in conversion of
Farmland, to non-agricultural use or
conversion of forest land to non-forest
use?
Sources: Town of Atherton General Plan 2019; Town of Atherton General Plan 2019 Update Project, Draft Initial Study/ Mitigated Negative Declaration; California Department of Conservation Farmland Mapping and Monitoring Program; and, San Mateo County Important Farmland Map, 2018.
Agricultural and Forestry Resources Setting
Atherton’s land uses comprise of residences, parks and open spaces, school facilities, and municipal uses. The Town does not contain agricultural land uses. According to the 2019 General Plan Land Use Element, the Town has no identified zones of agriculture, forest land, timberland, or timberland zoned Timberland Production. Accordingly, the Town of Atherton does not have Prime Farmland, Unique Farmland, or Farmland of Statewide Importance.
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Pursuant to California Public Resources Code (PRC) Section 12220(g), forest land is land that can support, under natural conditions, 10 percent native tree cover of any species, including hardwoods, and that allows for the management of forest-related resources such as timber, aesthetic value, fish and wildlife, biodiversity, water quality, recreation, and other public benefits. Timberland, as defined by PRC Section 4526 is land, other than land owned by the federal government and land designated by the board (State Board of Forestry and Fire Protection) as experimental forest land, which is available for, and capable of, growing a crop of trees of a commercial species used to produce lumber and other forest projects, including Christmas trees.
Trees in Atherton comprise an urban forest that is located on properties containing residential, parks and open spaces, areas around the Bear Gulch Reservoir, schools, and municipals land uses and along roadways.
Applicable General Plan Objectives and Policies
The Town of Atherton does not have agricultural uses in the Town. The Town of Atherton General Plan 2019 identifies goals, objectives, and policies intended to protect and enhance the thickly wooded nature of the Town. Those particularly relevant to the 2023 -2031 Housing Element Update include the following:
Land Use Element
Goal LU-1.1: To preserve the Town’s character as a scenic, semi-rural, thickly-wooded residential area with abundant open space.
Policy LU-1.5 Proposed residential subdivisions as well as proposals to replace existing homes, shall adhere to the following design criteria:
Trees shall be preserved to the maximum extent feasible while allowing for construction within established parameters for setbacks and lot coverage in accordance with the Municipal Code chapter regulating removal of and damage to heritage trees.
The Town allows minimum lot size subdivisions only where such minimum lot sizes do not significantly degrade established levels of privacy, wooded areas, and/or the open space environment.
Policy LU-1.8 Maximize preservation of heritage trees and existing trees within a development site to the greatest degree feasible, consistent with the Heritage Tree Ordinance and Tree Preservation Standards and Specifications. Require new development to comply with the Town’s requirements for tree protection, removal, and replacement.
Open Space and Conservation Element
Goal OSC-1: Protect both publicly and privately held open space lands from deterioration of their semi-rural charm, scenic value, and environmental equilibrium.
Objective OSC-1.1: Preserve presently existing open space, wildlife, and vegetation.
Objective OSC-1.2: Prevent developmental encroachment on open space and sensitive environmental resources.
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Policy OSC-1.1 The Town shall endeavor to protect scenic resources, significant stands of natural vegetation, wildlife habitat, public safety, and significant archaeological resources, both publicly and privately held.
Goal OSC-2: Protect and enhance the existing Coastal Oak Woodland character of the Town. Policy OSC-2.1 Trees shall be preserved wherever practical. This policy shall be explicitly considered during the development and subdivision process. Policy OSC-2.2 Wherever possible, drought tolerant native species trees shall be used for new and replacement planting and be tolerant of seasonal water inundation where used in or adjacent to green infrastructure facilities. Policy OSC-2.3 Enforce the Heritage Tree Ordinance and Tree Preservation Guidelines and Standards, or equal document.
Agricultural and Forestry Resources Impact Discussion
5.2 (a-c, and e) (Farmland Conversion, Williamson Act, Timberland and Other Conversions) No Impact: The sites in the Housing Element Update are not classified as Prime Farmland, Unique Farmland, or Farmland of Statewide Importance as mapped pursuant to the Farmland Mapping and Monitoring Program (FMMP) and none of the sites are located on parcels currently under Williamson Act contract because the Town of Atherton does not have agricultural land uses. Further, there are no properties zoned for agricultural use in the Town of Atherton. Therefore, there will be no impacts from the Housing Element Update to farmland, the conversion of farmland, conflicts with Williamson Act Contracts, and/or conflicts with zoning for agricultural uses.
All housing sites are designated Urban and Built-Up and Other Land, pursuant to FMMP.
Implementation of the 2023 – 2031 Housing Element would not introduce residential uses tangential to existing farmland and forest land because no such land use exists tangential to the housing sites and housing would be located on previously disturbed areas. Therefore, the proposed housing sites would not result in the conversion of farmlands or forestlands because of adoption and implementation of the 2023 – 2031 Housing Element and would have no impact on farmland and forestland resources.
There are no sites in the Housing Element Update that meet the definition of timberland pursuant to PRC Section 4526. Further, there are no properties zoned for timberland production in the Town of Atherton pursuant to California Government Code Section 51104(g). Therefore, there will be no impact from the Housing Element Update to timberland or timberland production zones.
5.2 (d) (Forestland) Less Than Significant Impact: PRC Section 12220(g) defines forest land as land that can support, under natural conditions, 10 percent native tree cover of any species, including hardwoods, and that allows for the management of forest-related resources such as timber, aesthetic value, fish and wildlife, biodiversity, water quality, recreation, and other public benefits.
The sites being considered under the Housing Element Update are on properties that either contain existing developed properties or are vacant properties zoned for residential uses in residential areas, which minimizes the areas for forests. While Atherton is considered a thickly wooded community, the Town’s natural condition is residential, and is therefore not forestland. Further, the thickly wooded nature of the Town does not afford the management of forest-related resources, and the Town of Atherton’s Heritage Tree Ordinance and Tree Preservation Guidelines and Standards provides for the protection of mature trees and requires replacement for removal of Town of Atherton
2023 – 2031 Housing Element 33 Initial Study/Mitigated Negative Declaration 2474551.1 14537.003
protected trees, which would ensure that aesthetic values of existing trees are maintained as a result of housing emanating from the Housing Element Update. Therefore, adoption and implementation of the 2023 – 2031 Housing Element would have a less than significant impact to forestland and timberlands.
Mitigation Measure(s): None Required.
Town of Atherton
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5.3. AIR QUALITY
Would the project:
Potentially
Significant
Impact
Less Than
Significant
with
Mitigation
Less Than
Significant
Impact
No Impact
a) Conflict with or obstruct
implementation of the applicable air
quality plan?
b) Result in a cumulatively considerable
net increase of any criteria pollutant for
which the project region is nonattainment under an applicable federal or state ambient air quality standard?
c) Exposure of sensitive receptors to
substantial pollutant concentrations?
d) Result in other emissions (such as
those leading to odors adversely affecting
a substantial number of people?
Sources: Town of Atherton General Plan 2019; Town of Atherton General Plan 2019 Update Project, Draft Initial Study/ Mitigated Negative Declaration; Town of Atherton Climate Action Plan; Air Quality and Greenhouse Gas Assessment, March 7, 2024; BAAQMD 2017 Bay Area Clean Air Plan; BAAQMD Justification Report: and CEQA Thresholds for Evaluating the Significance of Climate Impacts from Land Use Projects and Plans, April 2022.
Air Quality Setting
The Town of Atherton is located within the San Francisco Bay Area Air Basin (SFBAAB) regulated by the Bay Area Air Quality Management District (BAAQMD). Air quality within the Bay Area Air Basin is influenced by natural geographical and meteorological conditions as well as human activities such as construction and development, operation of vehicles, industry and manufacturing, and other anthropogenic emission sources. The Federal Clean Air Act and the California Clean Air Act establish national and state ambient air quality standards respectively.
The BAAQMD is responsible for planning, implementing, and enforcing air quality standards within the SFBAAB, including the Town of Atherton. The BAAQMD operates monitoring stations throughout the district and records pollutant concentration levels for carbon monoxide (CO), Nitrogen Dioxide (NO2), Ozone (O3), and Particulate Matter (PM). The BAAQMD Compliance and Enforcement Division routinely conducts inspections and audits of potential polluting sites to ensure compliance with applicable federal, state, and BAAQMD regulations.
The Bay Area Air Basin is designated as non-attainment for both the one-hour and eight-hour state ozone standards; 0.09 parts per million (ppm) and 0.070 ppm, respectively. Put differently, these are the levels at which the air district has determined that an individual project's contribution to the cumulative impact (non-attainment) is cumulatively considerable. The Bay Area Air Basin is also in non-attainment for the PM10 and PM2.5 state standards, which require an annual arithmetic mean (AAM) of less than 20 µg/m3 for PM10 and less than 12 µg/m3 for fine particulate matter (PM2.5). In Town of Atherton
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addition, the Basin is designated as non-attainment for the national 24-hour PM2.5 standard although the EPA recognized the Air District as achieving the attainment in 2013. 2 The nearest BAAQMD air monitoring station is in Redwood City, at a one-story commercial building located at 897 Barron Avenue. As of 2022, the monitoring station in Redwood City has maintained an annual average PM2.5 level of 6.8 µg/m3, which is less than the state air ambient quality standard of 12 µg/m3.
Applicable General Plan Goals, Objectives, and Policies The Town of Atherton General Plan sets forth goals, objectives, and policies intended to improve and enhance air quality, those particularly relevant to the 2023 -2031 Housing Element Update include the following:
Circulation Element
Goal CIR-7: Support the goals, policies and programs embodied in the adopted Atherton Climate Action Plan.
Open Space and Conservation Element
Goal OSC-5: Implement the GHG programs in the Atherton Climate Action Plan related to energy efficiency, community waste generation, and reduced water consumption.
Air Quality Impact Discussion
5.3(a) (Conflict with Applicable Air Quality Plan) Less Than Significant Impact with Mitigation:
The BAAQMD adopted the 2017 Bay Area Clean Air Plan (CAP) on April 19, 2017, to comply with state air quality planning requirements set forth in the California Health & Safety Code. The 2017 CAP includes a wide range of control measures designed to decrease emissions of the air pollutants most harmful to Bay Area residents and which include particulate matter (PM), ozone (O3), and toxic air contaminants (TACs). The CAP further endeavors to reduce emissions of methane and other “super-greenhouse gases (GHGs)” that are potent climate pollutants in the near-term and to decrease emissions of carbon dioxide by reducing fossil fuel combustion.
The proposed control strategy for the 2017 CAP consists of 85 distinct reduction measures targeting a variety of local, regional, and global pollutants. The CAP includes control measures for stationary sources, transportation, energy, buildings, and agriculture, natural and working lands, waste management, water, and super-GHG pollutants. Implementation of some of the control measures could involve retrofitting, replacing, or installing new air pollution control equipment, changes in product formulations, or construction of infrastructure that have the potential to create air quality impacts.
2 In January 2013, the US EPA issued a final determination recognizing the BAAQMD achieved the 24-hour PM2.5 national standard which effectively suspended the requirements for the region to submit EPA national ambient air quality documentation. So as long as the district meets the 2006 24-hour PM2.5 NAAQS, the District is not required to submit an attainment demonstration, reasonably available control measures, a reasonable further progress (RFP) plan, and contingency plans for failure to meet RFP and attainment deadlines. The ruling is effective February 8, 2013, and continues to through the latest available fine particulate matter measurements through 2016. The BAAQMD will continue to be designated as “non-attainment” for the national 24-hour PM2.5 standard until the Air District submits and “resignation request” and “maintenance plan” to EPA, and EPA approves the district’s resignation proposal.
Town of Atherton
2023 – 2031 Housing Element 36 Initial Study/Mitigated Negative Declaration 2474551.1 14537.003
In general, a project is considered to be consistent with the 2017 Bay Area Clean Air Plan if a) the project supports the primary goals of the CAP, b) includes control measures, and c) does not interfere with implementation of the CAP measures. The Project would have a less than significant impact due to the its alignment with the 2017 Bay Area Clean Air Plan since, a) it supports the goals of the CAP in that it limits sprawl by providing opportunities for housing development in the Town limits; b) includes control measures to protect air quality during construction by implementing best management practices set forth by BAAQMD, included below in Mitigation Measure AQ-1 and is consistent with the Town’s General Plan and Climate Action Plan that include goals, objectives, policies, and actions intended to reduce energy use and greenhouse gas emissions in new residential development; and, c) does not interfere with implementation of the CAP measures as the Project is a plan for infill development in an area served by local and regional transit and located near a mix of uses that include employment and services located in adjacent jurisdictions. As such, adoption and implementation of the 2023 – 2031 Housing Element will not conflict with or obstruct implementation of the 2017 CAP and impacts will be less than significant with mitigation.
5.3(b) (Violate Air Quality Emission Standards) Less than Significant with Mitigation: Air quality emissions associated with development facilitated by the 2023 – 2031 Housing Element would result from short-term construction activities and ongoing operation.
Construction
Construction activities, particularly during site preparation and grading, would temporarily generate fugitive dust in the form of PM10 and PM2.5. As detailed in the BAAQMD April 2022 Justification Report, there is no established threshold for construction-related climate impacts as emissions associated with construction represent a minimal part of overall emissions. However, BAAQMD has established best management practices (BMPs) to control for fugitive dust, for which the Bay Area Air Basin is designated non-attainment. Consistent with BAAQMD BMPs, future development that will occur under the 2023 – 2031 Housing Element shall be required to implement Mitigation Measure AQ-1, which provides for a variety of dust control measures during construction activities including watering the project site, covering haul loads, limiting idling time, and temporarily halting construction when winds are greater than 15 miles per hour. With implementation of measure AQ-1, construction activities will have a less than significant impact to air quality.
Operation
Operation of future housing sites will result in air quality emissions associated with stationary and mobile sources. Although there would be no stationary “point sources” (large emitters such as manufacturing plants) associated with housing development under the Housing Element, operation of future residences would result in area source emissions from the use of natural gas, consumer products such as solvents, cleaners, and paints, and landscaping maintenance equipment while most of the operational emissions will result from the operation of vehicles traveling to and from the project site (residents, deliveries, etc.).
The BAAQMD CEQA Guidelines have project-level screening sizes for operation emissions. The development of individual residential projects affected by the proposed Project does not exceed the screening levels. Therefore, emissions of operational related air pollutants would be less than significant.
5.3(c) (Sensitive Receptors) Less than Significant with Mitigation: The BAAQMD defines sensitive receptors as “facilities or land uses that include members of the population that are particularly Town of Atherton
2023 – 2031 Housing Element 37 Initial Study/Mitigated Negative Declaration 2474551.1 14537.003
sensitive to the effects of air pollutants, such as children, the elderly and people with illnesses.” Residential areas and schools are considered sensitive receptors because people are often at home/school for extended periods of time. Examples of sensitive receptors include places where people live, play, or convalesce and include schools, day care centers, hospitals, residential areas, and recreation facilities.
Construction
Sensitive receptors within proximity of sites identified in the Housing Element primarily consist of existing residents which may be exposed to health risks from construction exhaust emissions generated during future construction. As previously discussed, Mitigation Measures AQ-1 requires implementation of BAAQMD BMPs throughout the course of all future construction activities.
The Air Quality and Greenhouse Gas Assessment, prepared by Illingworth and Rodkin and dated March 7, 2024, includes a health risk assessment for the multifamily developments within the PFS zone to model the health risks from the construction of residential projects. The model evaluated a 20-unit development (Menlo School Site 2) and a 60-unit development (Menlo College Site 1) as they are the smallest and largest developments proposed in the PFS. CalEEMod was used to develop construction emissions of TACs and PM2.5 for each size project using the model’s default construction assumptions. The model found that the unmitigated maximum cancer risks from construction activities at the most impacted off-site receptors would exceed the single-source significance threshold at both the 60-unit and 20-unit development. However, with the incorporation of Mitigation Measure AQ-1 and the preparation of a Health Risk Assessment for specific sites as required by Mitigation Measure AQ-2, the mitigated risks would no longer exceed the significance threshold.
Operation
The Project may result in the introduction of new sensitive receptors (i.e. residents) that may be exposed to substantial levels of air pollutants of TACs. BAAQMD provides screening level TAC exposures for roadways, train lines, and stationary sources. Major TAC sources within the Town are identified in the Air Quality and Greenhouse Gas Assessment, prepared by Illingworth and Rodkin and dated March 7, 2024, using BAAQMD screening tools. The primary large volume roadway in Atherton is El Camino Real. There are also stationary sources identified within the Town limits using the BAAQMD’s stationary source GIS mapping tool. Sites potentially affected based on screening distances from existing air pollutant and TAC sources are as follows: Menlo College (proximity to El Camino Real); Cal Water (proximity to a gas dispensing facility and generic source); and 15 and 25 Monte Vista Avenue, Sacred Hearth, the Circus Club, Menlo School, and 175, 185, and 197 Ravenswood Avenue (proximity to a generator and/or generic source) Future development of sites identified in the Housing Element and affected by TAC sources must comply with Mitigation Measure AQ-3, which requires that the projects perform a project-specific Health Risk Assessment.
5.3(d) (Other Emissions) Less Than Significant Impact: Localized odors associated with future development of sites identified in the 2023 – 2031 Housing Element may result from operation of construction equipment, paving, and the application of architectural coatings. Adoption of the 2023 – 2031 Housing Element would not result in physical development, but rather will facilitate future development of these sites. As such, future construction at sites identified in the Housing Element Update may generate temporary odor. Such odors would be temporary and would be limited to the Town of Atherton
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immediate area of the construction zone and, therefore, are not considered significant. Odors are not typically associated with the operation of residential uses and, therefore, operational impacts would also be less than significant. Therefore, impacts related to other emissions, including odors that can adversely impact a substantial number of people, will be less than significant.
Mitigation Measure(s):
AQ-1: During all construction activities associated with future development facilitated by the 2023 – 2031 Housing Element, the contractor shall implement the latest BAAQMD recommended Best Management Practices (BMPs) to control for fugitive dust and exhaust as follows:
1. All exposed surfaces (e.g., parking areas, staging areas, soil piles, graded areas, and unpaved access roads) shall be watered two times per day.
2. All haul trucks transporting soil, sand, or other loose material shall be covered.
3. All visible mud and dirt track-out onto adjacent public roads shall be removed using wet power vacuum street sweepers at least once per day. The use of dry power sweeping is prohibited.
4. All vehicle speeds on unpaved roads shall be limited to 15 miles per hour (mph).
5. All roadways, driveways, and sidewalks to be paved shall be completed as soon as practicable. Building pads shall be laid as soon as practicable after grading unless seeding or soil binders are used.
6. All excavation, grading, and/or demolition activities shall be suspended when average wind speeds exceed 20 mph.
7. All trucks and equipment, including their tires, shall be washed off prior to leaving the site.
8. Unpaved roads providing access to sites located 100 feet or further from a paved road shall be treated with a 6- to 12-inch layer of compacted layer of wood chips, mulch, or gravel.
9. A publicly-visible sign with the telephone number and person to contact at the Lead Agency regarding dust complaints shall be posted on the project site prior to the initiation of construction activities. This person shall respond and take corrective action within 48 hours. The Air District’s phone number shall also be visible to ensure compliance with applicable regulations.
AQ-2: Require multi-unit residential projects, larger than 10 units, and within 1,000 feet of existing sensitive receptors, as defined by BAAQMD to prepare a project-specific construction health risk assessment (HRA). If the HRA demonstrates, to the satisfaction of the Town, that the health risk exposures for adjacent receptors will be less than BAAQMD project-level thresholds, then additional mitigation would be unnecessary. However, if the HRA demonstrates that health risks would exceed BAAQMD project level thresholds, additional feasible mitigation shall be analyzed and adopted to further reduce risks below the BAAQMD project-level thresholds. Measures to avoid significant construction health risks impacts that could be included in projects, depending on the results of an HRA could include the following:
Town of Atherton
2023 – 2031 Housing Element 39 Initial Study/Mitigated Negative Declaration 2474551.1 14537.003
1. Use Tier 4 engines for all off-road equipment greater than 50 horsepower (hp) and operating for more than 20 total hours over the entire duration of construction activities.
2. Use diesel trucks with 2010 or later compliant model year engines during construction.
3. Use renewable diesel during construction.
4. Implement enhanced measures to control dust emissions, as recommended by BAAQMD.
5. Use portable electrical equipment where commercially available and practicable to complete construction. Construction contractors shall utilize electrical grid power instead of diesel generators when: (1) grid power is available at the construction site; (2) when construction of temporary power lines are not necessary in order to provide power to portions of the site distant from existing utility lines; (3) when use of portable extension lines is practicable given construction safety and operational limitations; and (4) when use of electrical grid power does not compromise the construction schedule.
AQ-3: Prior to commencing construction activities on sites identified for residential development in the 2023 – 2031 Housing Element, the applicant/contractor shall prepare a site-specific Health Risk Assessment (HRA) for projects affected by Toxic Air Contaminant (TAC) sources. If the HRA demonstrates to the satisfaction of the Town, that the health risk exposures for sensitive receptors will be less than BAAQMD project-level thresholds, then additional mitigation would be unnecessary.
However, if the HRA demonstrates that health risks would exceed BAAQMD project level thresholds, additional feasible on- and off-site mitigation shall be analyzed by the applicant and adopted to help reduce risks below the BAAQMD project-level threshold. Such measures to be evaluated may include enhanced ventilation systems with filtration capable of reducing TAC exposure such that health risks are reduced to acceptable levels.
Town of Atherton
2023 – 2031 Housing Element 40 Initial Study/Mitigated Negative Declaration 2474551.1 14537.003
5.4. BIOLOGICAL RESOURCES
Would the project:
Potentially
Significant
Impact
Less Than
Significant
with
Mitigation
Less Than
Significant
Impact
No
Impact
a) Have a substantial adverse effect, either directly
or through habitat modifications, on any species
identified as a candidate, sensitive, or special status species in local or regional plans, policies, or
regulations, or by the California Department of Fish
and Wildlife (Formerly Fish and Game) or U.S. Fish
and Wildlife Service?
b) Have a substantial adverse effect on any riparian
habitat or other sensitive natural community
identified in local or regional plans, policies,
regulations or by the California Department of Fish
and Wildlife (formerly Fish and Game) or U.S. Fish
and Wildlife Service?
c) Have a substantial adverse effect on state or
federally protected wetlands (including, but not
limited to, marsh, vernal pool, coastal, etc.) through
direct removal, filling, hydrological interruption, or
other means?
d) Interfere substantially with the movement of any
native resident or migratory fish or wildlife species
or with established native resident or migratory
wildlife corridors, or impede the use of native
wildlife nursery sites?
e) Conflict with any local policies or ordinances
protecting biological resources, such as a tree
preservation policy or ordinance?
f) Conflict with the provisions of an adopted Habitat
Conservation Plan, Natural Community
Conservation Plan, or other approved local,
regional, or state habitat conservation plan?
Sources: Town of Atherton General Plan 2019; Town of Atherton General Plan 2019 Update Project, Draft Initial Study/ Mitigated Negative Declaration; Biological Constraints Analysis Report, November 30, 2023; Town of Atherton Municipal Code; and Town of Atherton’s Tree Preservation Guidelines and Standards.
Town of Atherton
2023 – 2031 Housing Element 41 Initial Study/Mitigated Negative Declaration 2474551.1 14537.003
Biological Resources Setting
Biological resources are protected by state and federal statutes including the Federal Endangered Species Act (FESA), the California Endangered Species Act (CESA), the Clean Water Act (CWA), the Migratory Bird Treaty Act (MBTA), and the California Fish and Game Code. These regulations provide the legal protection for plant and animal species of concern and their habitat at the state and federal level.
For purposes of this analysis, special-status species are plants and animals that are legally protected under the California and Federal Endangered Species Acts (CESA and FESA, respectively) or other regulations, and species that are considered rare by the scientific community, for example by the California Native Plant Society (CNPS). Special status species are defined as:
Plants and animals that are listed or proposed for listing, that are candidates for possible future listing as threatened or endangered under the CESA or the FESA. Plants and animals that meet the definition of endangered, rare, or threatened under CEQA that may include species not found on either CESA or FESA lists. Plants occurring on Ranks 1A, 1B, 2A, 2B, 3, and 4 of the CNPS’ electronic Inventory (CNPS 2001). The California Department of Fish and Wildlife (CDFW) recognizes that Ranks 1A, 1B, 2A and 2B of the CNPS inventory contain plants that, in the majority of cases, would qualify for State listing, and the CDFW requests their inclusion in EIRs. Migratory nongame birds of management concern listed by the United States Fish and Wildlife Service (USFWS).
Animals that are designated as "species of special concern" by the CDFW. Animal species that are “fully protected” in California. Bat species that are designated on the Western Bat Working Group’s (WBWG) Regional Bat Species Priority Matrix as, “RED OR HIGH.”
A Biological Constraints Analysis Report was prepared specifically for the proposed project to assess the housing opportunity site conditions and sensitive biological resources. Results from the Biological Report informed the biological resources impact discussion below.
There are 24 special-status plant species that are known for their occurrence within five (5) miles of the Atherton town limits. Most of these plants occur in specialized habitats such as serpentinite, chaparral, coastal dunes, vernal pools, and alkaline soil grasslands which are not present on any of these urban infill sites. However, of these special-status plants seven (7) have a low probability of occurring on project sites because the sites provide suitable habitat. These species include the congdon’s tarplant (Centromadia parryi ssp. congdonii), crystal springs lessingia (Lessingia arachnoidea), small-flowered monolopia (Monolopia gracilens), white-rayed pentachaeta (Pentachaeta bellidiflora), fragrant fritillary (Fritillaria liliacea), San Francisco collinsia (Collinsia multicolor), and western leatherwood (Dirca occidentalis). The rest of the special-status plant species in the five (5) mile radius of the planning area do not have a probability of occurring on project sites. The following is additional information on the special-status plant species that have a low probability of occurring on Housing Element sites:
Congdon’s Tarplant
Congdon’s tarplant is a CNPS Rank 1B.1 species. It has no state or federal status. The only CNDDB occurrence of this species within 5 miles of Atherton’s Town limits documents 17 plants observed in 2001 in a flat, ruderal grassland area roughly 4.2 miles northeast of subject Town of Atherton
2023 – 2031 Housing Element 42 Initial Study/Mitigated Negative Declaration 2474551.1 14537.003
parcel V1 (97 Santiago). The annual herbaceous/grassland habitats at 23 Oakwood Boulevard, MFO-10 (Cal Water), V1 (97 Santiago Avenue), and V3-V8 (Faxon Road, Faxon Forest Road and Monte Vista Avenue sites) could serve as suitable habitat for this species if alkaline soil conditions are present.
Crystal Springs Lessingia
Crystal Springs lessingia is a CNPS Rank 1B.2 species. Crystal Springs lessingia is a species with no federal or state status that was observed in 2001 west of the Edgewood County Park and south of the junction of Edgewood Road and I-280. Considering that the Cal Water site (MFO10) is roughly at an elevation of 185 feet, this parcel has the potential to provide habitat for the crystal Springs lessingia species, which is primarily identified in elevations between 195 and 655 feet.
Small-Flowered Monolopia
Small-flowered monolopia is a CNPS Rank 1B.2 species. The small-flowered monolopia has no state or federal status. Within the last 30 years, this species was identified roughly 3.8 miles northwest of the Cal Water site (MFO-10) in serpentine chaparral and gravelly soils. White-Rayed Pentachaeta
White-rayed pentachaeta is a federal and state listed endangered species. It is also a CNPS List 1B.1 species. This species was last identified in 2004 in a rocky and bare habitat with serpentine soils roughly four miles northwest of the subject parcel MFO-10 (Cal Water). The annual grassland areas at MFO-10 (Cal Water), V1 (97 Santiago Avenue), and V3-V8 (Faxon Road, Faxon Forest Road and Monte Vista Avenue sites) could provide suitable habitat for this species if there are rocky exposed areas that are not choked by annual grasses. Fragrant Fritillary
Fragrant fritillary is a plant species with no federal or state status and a CNPS Rank of 1B.2.
This species was observed in 2015 in a serpentine grassland habitat roughly 2.2 miles northwest of the subject parcel MFO-10 (Cal Water). This species is typically identified in serpentine soils; however, annual grassland habitat located on MFO-10 (Cal Water), V1 (97 Santiago Avenue), and V3-V8 (Faxon Road, Faxon Forest Road and Monte Vista Avenue sites) could provide suitable habitat for the species.
San Francisco collinsia
San Francisco collinsia is a CNPS List 1B.2 species. It has no federal or state status. This annual plant is found in moist, shady scrub and forest habitats, sometimes in serpentine soils. The nearest CNDDB occurrence of this species documents roughly 300 plants observed in 2015 in mixed foothill woodland and broadleaf forest on a steep slope roughly 4.3 miles west of subject parcel MFO-10 (Cal Water). Potentially suitable habitat for this species is present on the annual grassland areas on MFO-10 (Cal Water), V1 (97 Santiago Avenue), and V3-V8 (Faxon Road, Faxon Forest Road and Monte Vista Avenue sites) its presence cannot be dismissed without conducting formal special status plant surveys.
Town of Atherton
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Western leatherwood
Western leatherwood is not a federally or California state listed species. It is a CNPS List 1B.2 species. This plant can be found in chaparral, cismontane woodlands, riparian woodlands, closed cone coniferous forest, north coast coniferous forest, riparian forests, and broad-leafed upland forest. The nearest CNDDB occurrence of this species documents 12-50 plants observed in 2020 in thin, rocky, moist soil between foothill woodland and chaparral habitat roughly 1.5 miles south of subject parcel MFO-10 (Cal Water). The woodland/forest habitats on MFO-10 (Cal Water), and V3-V8 (Faxon Road, Faxon Forest Road and Monte Vista Avenue sites) may provide suitable habitat for this species.
There are 30 special-status wildlife species that are known for their occurrence within five (5) miles of the Atherton town limits and only four specific species can possibly occur on the proposed housing opportunity sites. Such species include the western burrowing owl (Athene cunicularia hypugaea), white-tailed kite (Elanus caeruleus), pallid bat (Antrozous pallidus), and the San Francisco dusky-footed woodrat (Neotoma fuscipes annectens). Additionally, nesting birds, including raptors such as the white-tailed kite, red-tailed hawk, and red-shouldered hawk, have the potential to occur on the proposed housing opportunity sites. However, no special-status wildlife has been recorded on or adjacent to any of the proposed housing opportunity sites. The following are special-status animal species that have a low probability of occurring on Housing Element sites:
Western Burrowing Owl
The Western Burrowing Owl is a California species of special concern. Its nest, eggs, and young are also protected under California Fish and Game Code (§3503, §3503.5 and §3513). The Burrowing Owl is also protected from direct take under the Migratory Bird Treaty Act. Finally, based upon this species’ rarity status, any unmitigated impacts to rare species would be considered a “significant effect on the environment” pursuant to §21068 of the CEQA Statutes and §15382 of the CEQA Guidelines. The nearest CNDDB record of this species documents one adult observed in winter of 2000 and 2003 above a trail through the restored San Mateo landfill area in San Mateo Shoreline Park approximately three miles east of subject parcel MFO-10 (Cal Water). The annual grassland habitat at the north end of MFO-10 (Cal Water) could provide suitable wintering or breeding burrows for this species. White-Tailed Kite
The White-tailed Kite is a “Fully Protected” species under the California Fish and Game Code (§3511). It is also protected under the federal Migratory Bird Treaty Act (50 CFR 10.13) and its eggs and young are protected under California Fish and Game Code (§3503, 3503.5). The White-tailed Kite is typically found foraging in grassland, marsh, or cultivated fields where there are dense-topped trees or shrubs for nesting and perching. The nearest CNDDB record for this species is located approximately 4.0 miles northwest of the subject parcel MFO-3 (318 Bay Road). This species could be encountered on any of the subject parcels that have suitable nesting trees in proximity to food and water sources.
Pallid Bat
The pallid bat is a California “species of special concern.” It has no federal status. The “species of special concern” status designation does not provide any special legally mandated protection for this bat species. However, this status designation could meet the definition of Town of Atherton
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“rare” pursuant to CEQA. The closest known CNDDB record for the pallid bat documents one male adult collected in woodland habitat approximately 1.7 miles west of subject parcel MFO10 (Cal Water). Abandoned tree and buildings also provide suitable roosting habitat for this species.
San Francisco Dusky-Footed Woodrat
The closest known CNDDB record for this species documents seven (7) nesting adult woodrats captured and relocated in riparian and ruderal grassland habitat along a drainage channel roughly 3.4 miles south of subject parcel V6 (Faxon Forest Road property). The wooded habitats on subject parcels V4, V5, and V6 (Faxon Forest Road properties) could provide suitable nesting habitat for this rodent species.
Nesting Birds
Passerine birds (songbirds) and raptors (i.e., birds of prey), their active nests, eggs, and young are protected under California Fish and Game Code. These species roost in trees that are located on project sites.
Applicable General Plan Objectives and Policies
The Town of Atherton’s General Plan sets forth goals, objectives, and policies intended to protect biological resources. Those particularly relevant to the 2023 -2031 Housing Element Update include the following:
Land Use Element
Goal LU-1.1: To preserve the Town’s character as a scenic, semi-rural, thickly-wooded residential area with abundant open space.
Policy LU-1.8 Maximize preservation of heritage trees and existing trees within a development site to the greatest degree feasible, consistent with the Heritage Tree Ordinance and Tree Preservation Standards and Specifications. Require new development to comply with the Town’s requirements for tree protection, removal, and replacement.
Open Space and Conservation Element
Goal OSC-1: Protect both publicly and privately held open space lands from deterioration of their semi-rural charm, scenic value and environmental equilibrium. Objective OSC-1.1: Preserve presently existing open space, wildlife, and vegetation. Objective OSC-1.2: Prevent developmental encroachment on open space and sensitive environmental resources.
Policy OSC-1.1 The Town shall endeavor to protect scenic resources, significant stands of natural vegetation, wildlife habitat, public safety, and significant archaeological resources, both publicly and privately held.
Goal OSC-2: Protect and enhance the existing Coastal Oak Woodland character of the Town. Policy OSC-2.1 Trees shall be preserved wherever practical. This policy shall be explicitly considered during the development and subdivision process.
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Policy OSC-2.3 Enforce the Heritage Tree Ordinance and Tree Preservation Guidelines and Standards, or equal document.
In addition to policies in the General Plan that protect biological resources in the Planning Area, the Town of Atherton’s Heritage Tree Ordinance and Tree Preservation Guidelines and Standards provide for the protection of mature trees and require replacement for removal of protected trees.
Atherton Municipal Code Section 8.10.020 identifies the following as heritage trees:
An oak tree (Quercus lobata, Quercus agrifolia or Quercus douglasii) located anywhere on a lot, that has a minimum trunk circumference of forty-eight (48) inches or diameter of fifteen and two-tenths (15.2) inches, as measured at fifty-four (54) inches above the Natural Grade. A tree located outside the Main Buildable Area, that has a minimum trunk circumference of forty-eight (48) inches or diameter of fifteen and two-tenths (15.2) inches, as measured at fifty-four (54) inches above the Natural Grade.
A split trunk or low-branching tree located outside the Main Buildable Area, that has a minimum trunk circumference of forty-eight (48) inches or diameter of fifteen and twotenths (15.2) inches, as measured at fifty-four (54) inches above the Natural Grade. If the trunk branches or splits below this point, the smallest circumference or diameter below the lowest branch shall be measured.
A multi-stemmed tree located outside the Main Buildable Area, that has a total trunk circumference of forty-eight (48) inches or total diameter of fifteen and two tenths (15.2) inches when calculated as follows: considering at all the branches at fifty-four (54) inches above Natural Grade, add the measurement of the largest branch to one-half the measurement of each additional branch. Reference the Guide for Plant Appraisal authored by representatives to the Council of Tree and Landscape Appraisers.
Biological Resources Impact Discussion
5.4(a-b) (Adverse Effects to Sensitive Species and Habitats) Less Than Significant with Mitigation: Adoption of the 2023 – 2031 Housing Element would not directly result in the physical development of identified housing sites, but rather will facilitate future development of these sites.
Most of these special-status plant species tend to occur in specialized habitats that include serpentinite, chaparral, coastal dunes, vernal pools, and alkaline soil grasslands, which are not found on housing opportunity sites. However, no plant surveys have been conducted to determine the presence or absence of special-status plant species on Housing Element site. Therefore, there is a potential that the project could result in a substantial adverse impact to sensitive species and habitats.
Special-Status Plant Species
Congdon’s Tarplant
The annual herbaceous/grassland habitats at 23 Oakwood Boulevard, MFO-10 (Cal Water), V1 (97 Santiago Avenue), and V3-V8 (Faxon Road, Faxon Forest Road and Monte Vista Avenue sites) could serve as suitable habitat for this species if alkaline soil conditions are present. If this species is identified on the subject Housing Element Update sites, construction activities could result in potentially significant impacts through disturbance and removal. To avoid potential impacts, future development of the above-mentioned housing sites shall comply with Mitigation Measure BIO-1.
With implementation of Mitigation Measure BIO-1, impacts to the congdon’s tarplant as anticipated by the Housing Element Update will be reduced to less than significant.
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Crystal Springs Lessingia
The MFO-10 (Cal Water) site is at roughly 185 feet of elevation but all the other subject parcels with annual grassland or woodland habitats are below 150 feet. If this species is identified on MFO-10, construction activities could result in potentially significant impacts through disturbance and removal. To avoid potential impacts, future development of MFO-10 shall comply with Mitigation Measure BIO-1. With implementation of Mitigation Measure BIO-1, impacts to the Crystal Springs lessingia species as anticipated by the Housing Element Update will be reduced to less than significant.
Small-Flowered Monolopia
The annual grassland habitat located on site MFO-10 (Cal Water) could potentially provide suitable habitat for the small-flowered monolopia species. If this species is identified on the subject parcel MFO-10, construction activities could result in potentially significant impacts through disturbance or removal. To avoid potential impacts, future development on MFO-10 shall comply with Mitigation Measure BIO-1. With implementation of Mitigation Measure BIO-1, impacts to the small-flowered monolopia species as anticipated by the Housing Element Update will be reduced to less than significant.
White-Rayed Pentachaeta
The annual grassland habitat located at MFO-10 (Cal Water), V1 (97 Santiago Avenue), and V3-V8 (Faxon Road, Faxon Forest Road and Monte Vista Avenue sites) could potentially provide suitable habitat for the white-rayed pentachaeta species, if there are rocky exposed areas present. If this species is identified on these subject parcels, construction activities could result in potentially significant impacts. To avoid potential impacts, future development on these subject parcels shall comply with Mitigation Measure BIO-1. With implementation of Mitigation Measure BIO-1, impacts to the white-rayed pentachaeta as anticipated by the Housing Element Update will be reduced to less than significant.
Fragrant Fritillary
Though this species is typically found in serpentine soils, the annual grassland habitat on MFO-10 (Cal Water), V1 (97 Santiago Avenue), and V3-V8 (Faxon Road, Faxon Forest Road and Monte Vista Avenue sites) could provide marginally suitable habitat for this species. If this species is identified on these subject parcels, construction activities could result in potentially significant impacts. To avoid potential impacts, future development on these subject parcels shall comply with Mitigation Measure BIO-1. With implementation of Mitigation Measure BIO-1, impacts to the Fragrant fritillary as anticipated by the Housing Element Update will be reduced to less than significant.
San Francisco Collinsia
Potentially suitable habitat for this species is present on the annual grassland areas on MFO-10 (Cal Water), V1 (97 Santiago Avenue), and V3-V8 (Faxon Road, Faxon Forest Road and Monte Vista Avenue sites) ; its presence cannot be dismissed without conducting formal special status plant surveys. To avoid potential impacts, future development on these subject parcels shall comply with Mitigation Measure BIO-1. With implementation of Mitigation Measure BIO-1, impacts to the San Francisco Collinsia as anticipated by the Housing Element Update will be reduced to less than significant.
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Western Leatherwood
The woodland/forest habitats on MFO-10 (Cal Water), and V3-V8 (Faxon Road, Faxon Forest Road and Monte Vista Avenue sites)may provide suitable habitat for this species. construction activities could result in potentially significant impacts. To avoid potential impacts, future development on these subject parcels shall comply with Mitigation Measure BIO-1. With implementation of Mitigation Measure BIO-1, impacts to the Western leatherwood as anticipated by the Housing Element Update will be reduced to less than significant.
Special-Status Wildlife Species
San Francisco Dusky-Footed Woodrat
If the San Francisco dusky-footed woodrat species is present on these subject parcels, construction activities could result in potentially significant impacts through disturbance and habitat removal. To avoid potential impacts, future development on these subject parcels shall comply with Mitigation Measure BIO-2, which requires the completion of pre-construction surveys for dusky-footed woodrats and the implementation of protective controls, if the species is present. With implementation of BIO-2, potential impacts to dusky-footed woodrats will be less than significant.
Western Burrowing Owl
If special status western burrowing owls are present on a parcel, construction activities could result in potentially significant impacts through disturbance and habitat removal. To avoid potential impacts, future development on this subject parcel shall comply with Mitigation Measure BIO-3, which requires the completion of pre-construction surveys for Burrowing Owls and the implementation of protective controls, if the species is present. With implementation of BIO-3, potential impacts to special status burrowing owls will be less than significant.
White-tailed kite and Other Nesting birds
Sites identified in the Housing Element contain individual trees that may have the potential to provide nesting habitat for raptors and passerines, including the white-tailed kite, which are protected under the California Fish and Game Code and the Federal Migratory Bird Treaty Act. Since most birds can fly out of harm’s way, future development of sites would not be expected to harm adult birds. Nonetheless, nesting birds are susceptible to disturbance that harms eggs or young birds, defined as a “take”. Activities associated with future development of sites identified in the Housing Element could include removal of trees as well as ground-disturbing construction activities that may result in impacts to nesting birds, if present onsite or in the immediate vicinity. To provide protection to nesting birds, their eggs, and their young, future development of sites identified in the Housing Element shall be required to comply with Mitigation Measure BIO-4 which restricts the timing of construction activities to occur outside of the bird nesting season or if the bird nesting season cannot be avoided requires pre-construction nesting bird surveys and controls to protect active nests, if present. With implementation of measure BIO-4, impacts to nesting birds will be less than significant.
Pallid bat
In addition to nesting birds, trees found on any of the subject Housing Element Update sites may provide suitable roosting habitat for special status bats, including the pallid bat. In the event that special status bats are present on any Housing Element Update sites, future construction activities Town of Atherton
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could result in potentially significant impacts through disturbance and habitat removal. To avoid potential impacts, future development of sites identified in the Housing Element shall comply with Mitigation Measure BIO-5, which requires completion of pre-construction bat surveys. If bats are identified, measure BIO-5 provides that removal and exclusion be conducted by a qualified biologist in conjunction with the CDFW. With implementation of BIO-5, potential impacts to special status bats will be less than significant.
5.4(c) (Adverse Effects to Jurisdictional Waters) No Impact: According to the Biological Constraints Report prepared for the project, there are no wetlands (including, but not limited to, marsh, vernal pool, coastal, etc.) or aquatic resources of any kind on the proposed Housing Element Update sites. Therefore, implementation of the Housing Element Update would have no impact on state or federally protected wetlands (including, but not limited to, marsh, vernal pool, coastal, etc.) or any other jurisdictional waters.
5.4(d) (Adverse Effect to Wildlife Movement) Less Than Significant Impact with Mitigation:
Given the developed surrounding of sites identified for future development under the Housing Element, impacts to wildlife movement through the introduction of structures, fences, and other improvements impassible by wildlife are less likely to occur. Consistent with Mitigation Measure BIO-1 and BIO-2, site specific assessments shall identify the suitability of sites to serve as movement corridors and shall identify measures to offset potential impacts, as necessary. With implementation of measure BIO-1, future development of sites identified in the Housing Element will have a less than significant impact to wildlife corridors and species movements.
5.4(e) (Conflict with Local Ordinances) Less Than Significant Impact: Development of sites identified in the Housing Element may require removal of trees to accommodate buildings, infrastructure, landscaping, and other associated site improvements. However, the Town of Atherton’s Tree Ordinance (Section 8.10 of the Municipal Code) contains provisions to preserve and protect “heritage trees” within the Town.
The Project does not include amendments to the Town’s Heritage Tree ordinance to facilitate housing production, except for ADUs permitted explicitly by state law. Pursuant to State law, the Town cannot deny an ADU of 800 square feet or less, that removes a heritage tree or is built beyond the Town’s setbacks for Accessory Buildings. To incentive ADU development that complies with the Town’s setbacks for accessory buildings and preserves heritage trees within required setbacks, the Project allows for larger ADUs, up to 1,200 square feet, and ADUs located above detached garages.
The Town has also updated its Master Fee Schedule to waive fees for ADUs that comply with the Town’s local development standards.
For ADUs and all other housing sites, compliance with the Town’s Heritage Tree Ordinance and General Plan goals, objectives, and policies will reduce impacts to trees as a result of project construction. Therefore, the project will not conflict with a local ordinance and impacts will be less than significant.
5.4(f) (Conflicts with Habitat Conservation Plans) No Impact: No Habitat Conservation Plan, Natural Community Conservation Plan, or other approved local, regional, or state Habitat Conservation Plan exists for the Town of Atherton. Therefore, future development under the 2023 – 2031 Housing Element will not conflict with the provisions of an adopted Habitat Conservation Plan, or any other Natural Community Conservation Plan approved by a local, regional or state body.
Town of Atherton
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Mitigation Measure(s):
BIO-1: Prior to the Town of Atherton’s approval of development on the proposed Housing Element Update sites, special-status plant surveys shall be conducted by a qualified botanist in appropriate habitats during the appropriate period (congdon’s tarplant’s blooming period is from May through November; crystal springs lessingia’s blooming period is from July through October; small-flowered monolopia’s blooming period is from March through July; white-rayed pentachaeta’s blooming period is from March through May; and fragrant fritillary’s blooming period is from February through April) in which the species are most identifiable. Project construction shall not be initiated until all special-status plant surveys are completed and subsequent mitigation, if deemed necessary by the qualified botanist, is implemented. If the special-status plant species are identified in these surveys, those individuals or populations shall be avoided to the maximum extent possible. If avoidance is not possible, then other suitable measures and mitigations shall be developed in consultation with agencies that are responsible for the protection of the subject plant species, based on its protection status [i.e., Town of Atherton (for plants protected by CEQA), CDFW (plants protected by California law/regulation) or USFWS (protected by federal law regulation)]. Appropriate mitigation prescriptions for impacts on special-status plants shall be included as conditions of project approval.
BIO-2: Unless otherwise recommended in site-specific biological assessments prepared for future development of sites identified in the Housing Element, to avoid impacts to the San Francisco dusky-footed woodrat, a species of special concern, a survey prior to the commencement of ground disturbing activities or vegetation removal on subject parcels with suitable vegetation. Since woodrats use their nests year-round, surveys for the rodent species can be conducted at any time of the year. If the woodrat nests are identified, they shall be flagged and delineated on project site maps.
If any woodrat nests are identified, then CDFW shall be contacted immediately to coordinate mitigation. A qualified biologist shall conduct a pre-construction survey for the San Francisco dusky-footed woodrat nests no more than 30 days prior to the onset of site grubbing/grading or construction activities within 50 feet of construction zones. The identified nests shall be avoided, where possible. If avoidance is not possible, the nest(s) should be manually deconstructed when helpless young are not present, typically during the non-breeding season which is October through January. If it is determined that young may be present during the pre-construction survey, a suitable buffer, depending on the type of impact, nest location, and topography of the nest location, shall be established by the qualified biologist. The non-disturbance buffer typically ranges from 20 to 50 feet. This buffer shall remain in place around the nest until the young are independent enough to successfully move from the nest.
BIO-3: Unless otherwise recommended in site-specific biological assessments prepared for future development of the Cal Water site identified in the Housing Element, to avoid impacts to burrowing owls protected under the Migratory Bird Treaty Act and Fish and Game Code (§3503, §3503.5 and §3513), a preconstruction survey for burrowing Owls shall be conducted at the Cal Water site (MFO-10) 14 days prior to ground disturbance. Since burrowing owls can recolonize a site only after a few days, time lapses between project activities trigger subsequent take avoidance surveys, including but not limited to a final survey conducted within 24 hours prior to ground disturbance to ensure that the species is not present.
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Between April 1st and October 15th, low disturbance and medium disturbance activities should have a 200-meter buffer while high disturbance activities should have a 500-meter buffer from occupied nests. Between October 16th and March 31st, low disturbance activities should have a 50-meter buffer, medium disturbance activities should have a 100-meter buffer from occupied nests, and high disturbance activities should have a 500-meter buffer from occupied nests. No earth-moving activities or other disturbances within the aforementioned buffer zones of occupied burrows. These buffer zones shall be fenced as well. If burrowing owls are present on the proposed project area, then a qualified biologist would need to delineate the extent of the western burrowing owl habitat on the site.
BIO-4: Unless otherwise recommended in site-specific biological assessments prepared for future development of sites identified in the Housing Element, to avoid impacts to birds protected under the Migratory Bird Treaty Act and Fish and Game Code (Section 3514), construction activities, including the removal of trees, should occur outside of the birdnesting season between September 2nd and January 31st. If work occurs between February 1 st and September 1st, a pre-construction bird nesting survey shall be conducted within seven days prior to any proposed ground disturbance or vegetation removal on subject parcels that require nesting bird surveys. The bird nesting survey shall include an examination of all buildings onsite, and trees and shrubs onsite and within 200 feet of the subject parcel (i.e., within a zone of influence of nesting birds), not just trees slated for removal. The zone of influence includes areas outside of the project site where birds could be potentially disturbed by earth-moving vibrations and/or other construction-related noises. If any active bird nests are identified onsite or within a zone of influence, then a qualified ornithologist or biologist shall establish a temporary protective construction buffer around the nest(s), conduct a survey to establish behavioral baseline of birds using each nest, and conduct monitoring to ensure it is not disturbed. The nest buffer will be staked or fenced with orange construction fencing to establish a construction exclusion perimeter and shall be adjusted by a qualified biologist as needed to avoid disturbance. The buffer shall be of sufficient size to protect the nesting site from construction-related disturbance. Typically, adequate nesting buffers are 50 feet from the nest site or nest tree dripline for small birds and up to 300 feet for sensitive raptors. Upon completion of nesting surveys, if nesting birds are identified a qualified ornithologist/biologist shall prescribe adequate nesting buffers to protect the nesting birds from harm while the project is being constructed. If continuous monitoring is not feasible, conservative no-disturbance buffer(s) should be established, with the buffer distance based on the tolerance level of the nesting species.
No construction or earth-moving activity shall occur within any established nest protection buffer prior to September 1st unless determined by a qualified ornithologist/biologist responsible for monitoring nesting behavior that the young have left the nest and have attained sufficient flight skills to avoid construction zones, or that the nesting cycle is otherwise completed. At the end of the nesting cycle and the fledging from the bird nest, as determined by a qualified biologist, temporary nesting buffers may be removed, and construction may commence in established nesting buffers without further regard for the nest site.
The biologist/ornithologist conducting the surveys shall provide the Town of Atherton with a report detailing the results of the survey and any recommendations required for Town of Atherton
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establishment of protective buffers, if vegetation removal or any ground disturbance occurs between February 1st and September 1st.
BIO-5: Unless otherwise recommended in site-specific biological assessments prepared for future development of sites identified in the Housing Element, to avoid impacts to roosting pallid bats or other special-status bat species, building or tree removal shall only be conducted during seasonal periods of bat activity, between August 31 and October 15, when bats would be able to fly and feed independently, and between March 1 and April 1 to avoid hibernating bats, and prior to the formation of maternity colonies. A biologist with at least two years of experience surveying for bats, shall conduct a pre-construction survey of all buildings and trees that would be impacted within 14 days prior to removal or commencement of site improvement activities. If no special-status bats are found during the surveys, then the biologist shall provide a memo summarizing the results of the survey to the Town, and construction activities may commence. If bat roosts are found, then a plan shall be developed by the qualified biologist for removal and exclusion, when there are not dependent young present, in conjunction with the CDFW.
If building or tree removal must occur outside the seasonal activity periods (i.e., between October 16 and the end of February, or between April 2 and August 30), then a qualified biologist, shall conduct pre-construction surveys within 14 days of removal, and determine if there are young present (i.e., the biologist will determine if there are maternal roosts). If a maternity site is found, impacts to the maternity site shall be avoided by establishment of a fenced, non-disturbance buffer until the young have reached independence (i.e., are flying and feeding on their own) as determined by a qualified biologist. The size of the buffer zone shall be determined by a qualified biologist at the time of the surveys. If the qualified biologist finds evidence of roosting bats but not a maternity site with young, then a plan shall be developed for removal and exclusion, in conjunction with the CDFW. The biologist shall provide the Town with a report detailing the results of the survey and any recommendations, as warranted, required for establishment of protective buffers for bat roosts, if identified.
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5.5. CULTURAL RESOURCES
Would the project:
Potentially
Significant
Impact
Less Than
Significant
with
Mitigation
Less Than
Significant
Impact
No Impact
a) Cause a substantial adverse change
in the significance of a historical
resource pursuant to § 15064.5?
b) Cause a substantial adverse change
in the significance of an archaeological
resource pursuant to § 15064.5?
c) Disturb any human remains, including
those interred outside of formal
cemeteries?
Sources: Town of Atherton General Plan 2019; Town of Atherton General Plan 2019 Update Project, Draft Initial Study/ Mitigated Negative Declaration; Historic Resource Evaluation of Faculty Housing Apartment 8B on Menlo College, Memorandum on the Preliminary Evaluation of Housing Element Site, and Archaeological Record Search and Report of Findings for the Town of Atherton Housing Element and Zoning Code Update.
Cultural Resources Setting
In 1923, the Town of Atherton was incorporated within the County of San Mateo. The Town of Atherton contains cultural resources that contribute to the understanding of the region's history and influence the community’s identity. Atherton has a policy for protecting and preserving cultural resources such as historically significant buildings, structures, and artifacts.
Historic Resources
Historic resources include historic structures, sites and areas that played important roles in local history. Older buildings may hold historic value in their design attributes that provide insight into architectural styles and values of the past. The Town of Atherton recognizes these historic and potentially historic resources as worthy of preservation both for their aesthetic and cultural value.
In 2006, a survey of potential historical artifacts resulted in a list known as the Atherton Historical Artifact Inventory. According to the General Plan, the Town has eight historically significant buildings and structures that are publicly and privately owned. These include: the Watkins/Cartan House, the water tower at Holbrook-Palmer Park, the Gen Merrill Carriage House, the Sacred Heart Schools main building, the Menlo School Stent Family Hall, the Perry Stable, the Caltrain Station at the Town Center, and the Town Hall.
Applicable General Plan Goals, Objectives, and Policies The Town of Atherton’s General Plan sets forth goals, objectives, and policies intended to protect cultural resources. Those particularly relevant to the 2023 -2031 Housing Element Update include the following:
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Open Space and Conservation Element
Goal OSC-1: Protect both publicly and privately held open space lands from deterioration of their semi-rural charm, scenic value and environmental equilibrium. Policy OSC-1.1 The Town shall endeavor to protect scenic resources, significant stands of natural vegetation, wildlife habitat, public safety and significant archaeological resources, both publicly and privately held.
Goal OSC-4: Protect both publicly and privately held cultural resources from deterioration and/or destruction.
Policy OSC-4.1 Encourage the preservation of both private and public historical resources and artifacts for the benefit of future generations. Policy OSC-4.2 The Town will comply with minimum State requirements in the event archaeological or paleontological resources are discovered during construction.
Cultural Resources Impact Discussion
5.5(a) (Historic Resources) Less Than Significant Impact: Adoption of the 2023 – 2031 Housing Element and Zoning Code updates would not result in physical development, but rather facilitates future development of identified sites. None of the housing sites identified in the proposed Housing Element Update are listed in local, state or national registers as parcels containing potentially significant historic resources nor are any of the sites within a potential historic district boundary. To address potential eligibility, a preliminary evaluation for qualification as a historical resource in accordance with Article 5, §15064.5 of the California Environmental Quality Act (CEQA) Guidelines and the local criteria was conducted for 9 subject properties: 999 Ringwood Avenue (APN 061091080); 352 Bay Road (APN 061091070); 318 Bay Road (APN 061091060); 296 Bay Road (APN 061091050); 175 Ravenswood Avenue (APN 061281050); 185 Ravenswood Avenue (APN 061281060); 197 Ravenswood Avenue (APN 061281150); 23 Oakwood Boulevard (APN 059153080); and 150 Valparaiso Avenue (APN 070390010).
The preliminary evaluation includes a recommendation for the multi-family development site located on the Sacred Heart campus (Nun Residence). The recommendation advises for additional review to address the site’s development because of its proximity to the Menlo Circus Club, a site listed in the Town of Atherton’s Inventory for Open Space Lands. The RM-20 overlay applied to the subject site as a Zoning Code update would allow a maximum height of 48 feet or 4 stories and require setbacks from adjacent properties no less than 20 feet for main buildings. Additional landscaping standards are also included and will supplement the Town’s existing landscaping requirements and screen the perception of the building mass from scenic road vistas, parks and open spaces.
For the purpose of identifying historic resources, the preliminary evaluation found, including the recommendation for the Nun Residence, that the subject structures do not possess historical significance, are not a strong example of the Ranch, Spanish-Ranch, and Split-Level architectural styles, were not designed by a master architect or builder, and are not associated with important events or persons.
Separate from the preliminary evaluation, a full Historic Resource Evaluation (HRE) was prepared for the Faculty Housing Apartments 8B at Menlo College to address potential historic eligibility of the structure. The HRE found that the structure does not possess historical significance, is not a strong Town of Atherton
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example of the Contemporary style, was not designed by a master architect or builder, and is not associated with important events or persons. It is the professional opinion of the evaluator that the structure (1) is not individually eligible for the California Register of Historical Resources, (2) is not individually eligible for the California Register of Historical Resources, (3) does not qualify individually as a historical resource under CEQA Guidelines §15064.5(a)(3), and (4) is not eligible for individual historic designation under Atherton Municipal Code, Chapter 8.15.200, Criteria for designating a historic building. Based on the lack of existing historic resources on sites identified in the proposed Housing Element Update impacts to historic resources resulting from adoption and implementation of the 2023 – 2031 Housing Element will be less than significant.
5.5(b) (Archaeological Resources) Less Than Significant with Mitigation: Adoption of the proposed Housing Element Update will facilitate future development of undeveloped sites that have been identified to accommodate residential development in the city. Though physical development will not occur as a direct result of adoption of the Housing Element, future development of these sites is reasonably foreseeable. Based on the undeveloped condition of sites identified in the Housing Element, there is a potential that unrecorded prehistoric era archaeological deposits may be encountered during ground-disturbing activities including grading, trenching, and digging.
Consistent with adopted General Plan policies, site-specific development proposals shall comply with Mitigation Measure CUL-1, which requires an assessment of archaeological resources by a qualified professional, including potential adverse impacts to cultural resources and recommendations to avoid or reduce such impacts. Furthermore, CUL-1 requires that any archaeological resources identified shall either be preserved in place or adequately documented, cataloged, and recorded. With implementation of measure CUL-1 potential impacts due to a change in the significance of archeological resources if present on identified Housing Element site will be reduced to less than significant.
5.5(c) (Discovery of Human Remains) Less Than Significant with Mitigation: Adoption of the proposed Housing Element Update will facilitate future development of some developed and vacant sites that have been identified to accommodate residential development within the Town. As such, it is possible, through the future development of proposed housing sites, that human remains could be discovered during ground-disturbing activities. Consistent with California Health and Safety Code Section 7050.5, future development of sites identified in the Housing Element shall comply with Mitigation Measure CUL-2, which identifies procedures to follow in the event that human remains or archaeological deposits are discovered. With implementation of CUL-2, Section 7050.5 of the California Health and Safety Code, and Sections 5097.94, 5097.98 and 5097.99 of the California Public Resources Code, as required under state law, potential impacts resulting from accidental discovery of Native American remains associated with future housing development will be less than significant.
Mitigation Measures:
CUL-1: Upon submittal of site-specific development proposals for housing opportunity sites identified in the 2023 – 2031 Housing Element, a project-specific archaeological study should be undertaken for each development project proposed within the Subject Properties. An archaeological study should consist of a record search at the NWIC/CHRIS, a literature review, a pedestrian field survey, a site-specific assessment of the potential for subsurface archaeological resources to be present, and preparation of a report with project-specific recommendations. A geophysical survey and/or subsurface testing should be required for properties that have a high potential for buried archaeological resources, including Property Town of Atherton
2023 – 2031 Housing Element 55 Initial Study/Mitigated Negative Declaration 2474551.1 14537.003
V2, which is adjacent to the previously recorded Native American archaeological resource P41-000278.
CUL-2 If an archaeological deposit is encountered during ground-disturbing activities, all work within 50 feet of the discovery shall be redirected until a Secretary of Interior-qualified Archaeologist assesses the find, consults with agencies and Native American tribes as appropriate, and makes recommendations for the treatment of the discovery. If avoidance of the archaeological deposit is not feasible, the archaeological deposit shall be evaluated for its eligibility for listing in the CRHR or as a unique archaeological resource. If the deposit is found to be eligible, all efforts should be made to avoid impacts to the resource. If avoidance is not feasible, adverse impacts shall be mitigated. Mitigation may include excavation of the archaeological deposit in accordance with the Secretary of Interior’s Standards and Guidelines for Archaeological Documentation that may include data recovery using standard archaeological field methods and procedures; laboratory and technical analyses of recovered archaeological materials; preparation of a report detailing the methods, findings, and significance of the archaeological site and associated materials; and accessioning of archaeological materials and a technical data recovery report at a curation facility. Upon completion of the assessment, the archaeologist shall prepare a report to document the methods and results of the assessment. The report shall be submitted to the NWIC/CHRIS upon completion of the resource assessment.
CUL-3 In the event that human skeletal remains are uncovered during ground-disturbing activities, all work shall immediately halt and the San Mateo County Coroner shall be contacted to evaluate the remains and following the procedures and protocols pursuant to Section 15064.5 (e)(1) of the CEQA Guidelines. If the County Coroner determines that the remains are Native American, the Coroner shall contact the NAHC, pursuant to subdivision (c) of Section 7050.5 of the Health and Safety Code, and all excavation activities shall cease within a 50-foot radius of the find until appropriate arrangements are made. A Secretary of Interiorqualified Archaeologist should also evaluate the historical significance of the discovery, the potential for additional human remains to be present, and provide further recommendations for treatment of the resource in accordance with the MLD recommendations and the Secretary of Interior Standards for the Treatment of Historic Properties. Adherence to CUL-3 would ensure that development carried out under the proposed Project would have a less than significant impact from potential disturbance of human remains, specifically those interred outside of formal cemeteries.
Town of Atherton
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5.6. ENERGY
Would the project:
Potentially
Significant
Impact
Less Than
Significant
with
Mitigation
Less than
Significant
Impact
No
Impact
a) Result in a potentially significant environmental
impact due to wasteful, inefficient, or unnecessary
consumption of energy, or wasteful use of energy
resources, during project construction or
operation?
b) Conflict with or obstruct a state or local plan for
renewable energy or energy efficiency?
Sources: Town of Atherton General Plan 2019; Town of Atherton General Plan 2019 Update Project, Draft Initial Study/ Mitigated Negative Declaration; Town of Atherton Climate Action Plan, November 2016; California Energy Commission website; California Energy Commission, 2019 California Energy Efficiency Action Plan.
Energy Setting
Energy resources include electricity, natural gas, and other fuels. The production of electricity requires the consumption or conversion of energy resources, including water, wind, oil, gas, coal, solar, geothermal, and nuclear resources, into energy. Energy production and energy use both result in the depletion of nonrenewable resources (e.g., oil, natural gas, coal, etc.) and emission of pollutants.
Within the Town, the building sector is the primary contributor to Greenhouse Gas (GHG) emissions.
The transportation sector is the second highest GHG emissions contributor within the Town limits.
The Town adopted Climate Action Plan (CAP) identifies methods that can be used by the Town and the community to reduce GHG emissions.
California Energy Consumption
According to the California Energy Commission (CEC), total system electric generation for California in 2021 was 277,764 gigawatt-hours (GWh).3 California’s non-CO2 emitting electric generation categories (nuclear, large hydroelectric, and renewable generation) accounted for approximately 49 percent of total in-state generation for 2021. Total in-state renewable energy generation increased by 3.5 percent in 2021 from 2020.
According to the CEC, approximately 50.2% percent of natural gas was generated in-state, totaling 97,431 GWh. Natural gas is used to generate electricity for cooking and heating and serves as an alternative transportation fuel.4
3 California Energy Commission, Total System Electric Generation (2021) https://www.energy.ca.gov/data-reports/energyalmanac/california-electricity-data/2020-total-system-electric-generation, accessed December 11, 2023. 4 California Energy Commission, Supply and Demand of Natural Gas in California, https://www.energy.ca.gov/datareports/energy-almanac/californias-natural-gas-market/supply-and-demand-natural-gas-california, accessed December 11, 2023.
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2023 – 2031 Housing Element 57 Initial Study/Mitigated Negative Declaration 2474551.1 14537.003
The CEC has developed an energy efficiency action plan to be updated every three years. The latest plan, the 2019 California Energy Efficiency Action Plan, contains three goals for driving energy efficiency: doubling energy efficiency savings by 2030, removing and reducing barriers to energy efficiency in low-income and disadvantaged communities, and reducing greenhouse gas emissions from the building sector. Per the Plan, the state contains approximately nine million single-family residences, of which nearly half were constructed before 1970 and about 80 percent before 1990.5 Due to existing infrastructure being constructed prior to the approved energy standards, there are opportunities to increase energy efficiency through building envelope and other weatherization measures. However, implementation of retrofits presents challenges such as lack of available financing, and consumer awareness and motivation.
Energy consumption in new development is regulated through the California’s Energy Code, Title 24, Part 6 and 11 of the California Code of Regulations. The CEC updates Building Energy Efficiency Standards every three years. The 2019 Building Energy Efficiency Standards became effective as of January 1, 2020. On August 11, 2021, the CEC adopted the 2022 Energy Code, which became effective on January 1, 2023. New construction is required to comply with energy efficiency standards in effect through the current building code.
Town of Atherton Energy Sources
Households and other operators within the Town of Atherton rely on a variety of energy resources (fuels, photovoltaic, natural gas, oil, coal, etc.) to provide energy for lighting, cooking, heating, cooling, and to operate vehicles.
The Town’s energy resources are produced by Peninsula Clean Energy (PCE) and conveyed by Pacific Gas and Electric (PG&E). While PCE provides electric generation, PG&E continues to deliver electricity through its facilities, and handles maintenance, repairs, and billing services.
Applicable General Plan Goals, Objectives, and Policies The Town of Atherton’s General Plan sets forth goals, objectives, and policies intended to improve and enhance energy efficiency in the town, those particularly relevant to the 2023 -2031 Housing Element Update include the following:
Open Space and Conservation Element
Goal OSC-5: Implement the GHG programs in the Atherton Climate Action Plan related to energy efficiency, community waste generation, and reduced water consumption.
In addition to the General Plan goals, objectives, and policies, the Town of Atherton adopted the California Green Building Code that regulates the improvement of public health, safety and general welfare through the design and construction of buildings. The California Green Building Code implements building concepts that can reduce negative impacts or support positive environmental impacts for all buildings and structures.
5 California Energy Commission, 2019 California Energy Efficiency Action Plan. https://www.energy.ca.gov/programs-andtopics/programs/energy-efficiency-existing-buildings Town of Atherton
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Energy Impact Discussion
5.6 (a) (Wasteful, Inefficient, Unnecessary Consumption of Energy) Less than Significant Impact: The adoption of the 2023 – 2031 Housing Element will not result in direct physical construction. However, the future development of identified housing sites will involve the use of energy during construction activities and at operation.
Construction
During the future development of the proposed sites, activities such as site preparation, grading, paving, and building construction will consume energy in the form of gasoline and diesel fuel through the operation of heavy off-road equipment, trucks, and worker vehicles. Such energy consumption would be temporary and would cease upon the completion of construction. As stated in Section 5.3 Air Quality, the Town of Atherton will implement the BAAQMD best management practices through Mitigation Measure AQ-1, which will reduce idling times and require the proper maintenance of construction equipment in tune with manufacturer’s specifications. Future construction activities would have a limited duration and scale and as such implementation of the Housing Element (e.g., construction of residential development on identified housing sites) would not result in the inefficient, wasteful, and unnecessary consumption of energy during construction and resulting impacts will be less than significant.
Operation
The operational energy use associated with future residential development consists of lighting, electronics, heating, air conditioning, cooking, refrigeration, and energy consumption related to conveyance and treatment of water and wastewater, and fuel consumption associated with vehicular use. The California Energy Commission (CEC) updates the Energy Code every three years.
In August 2021, the CEC adopted the 2022 Energy Code, which was approved by the California Building Standards Commission for inclusion into the California Building Standards Code in December 2021. The 2022 Energy Code encourages efficient electric heat pumps, establishes electric-ready requirements for new homes, and expands solar photovoltaic and battery storage standards. The 2022 Energy Code went into effect on January 1, 2023, therefore, building permits submitted for sites identified in the Housing Element will be required to comply with the energy requirements established by the 2022 Building Code or latest adopted Building Code. The CEC plans to adopt the 2025 Energy Code which will set new requirements for heat pump baselines and solar photovoltaic systems. Future building permits submitted for residential developments on identified sites will be required to comply with the anticipated 2025 Energy Code.
In addition, energy efficiency will be achieved through landscape design that will comply with the State Water Efficient Landscape Ordinance requirements. Landscaping plans submitted for sitespecific development will be required to adhere to California’s model water efficient landscape regulations that include drought-resistant, low water usage species, and irrigation system requirements. Water conservation efforts achieve energy efficiency by minimizing water use and the corresponding energy demand required for water treatment and conveyance.
While foreseeable development of sites identified in the 2023 – 2031 Housing Element would result in increased energy consumption compared to existing conditions, site-specific development proposals will be required to incorporate energy efficiency standards in compliance with the building code in effect at the time, which will minimize energy consumption. Furthermore, these sites have been anticipated to support housing by the Town of Atherton in the General Plan and Town of Atherton
2023 – 2031 Housing Element 59 Initial Study/Mitigated Negative Declaration 2474551.1 14537.003
prior Housing Elements. Therefore, operation of residential uses facilitated by implementation of the Housing Element will not result in the wasteful, inefficient, and unnecessary consumption of energy and impacts will be less than significant.
5.6 (b) (Conflict with State or Local Plan) Less Than Significant Impact: In December 2007, the CEC prepared the State Alternative Fuels Plan in partnership with the California Air Resources Board (CARB) and other state, federal, and local agencies. The plan presents strategies and actions California must take to increase the use of alternative non-petroleum fuels in a manner that minimizes costs to California and maximizes the economic benefits of in-state production. The plan assesses various alternative fuels and develops fuel portfolios to meet California’s goals to reduce petroleum consumption, increase alternative fuels use, reduce greenhouse gas emissions, and increase in-state production of biofuels without causing a significant degradation of public health and environmental quality.
The Town adopted a Climate Action Plan (CAP) in November 2016 that provides policies and measures that will guide the Town to exceed the greenhouse gas emission reduction goals of AB 32.
The CAP identified programs and measures to increase residential energy efficiency that emphasize education, outreach, the green building code, PG&E energy efficiency, and other implementable measures.
The Town also developed a Bicycle and Pedestrian Master Plan in July 2014 that outlines goals and objectives that will promote increased safety and levels of non-motorized activity. The Bicycle and Pedestrian Master Plan is intended to improve the walking and biking opportunities within the Town, while improving the overall connectivity between adjacent communities. Implementation of the Bicycle and Pedestrian Master Plan will reduce energy consumption.
The 2022 California Green Building Standards Code, identified in the California Code of Regulations as Title 24, Part 11, is adopted as the green building code of the Town. The Green Building Standards Code serves to improve public health through the enhancement of design and construction of buildings that will result in a reduced negative impact or positive environmental impact. The building requirements outlined in the code must be implemented upon the review and permit process of foreseeable developments. Compliance with such requirements would ensure that the reasonably foreseeable developments would not conflict with the energy efficiency goals and objectives outlined in Town plans.
Development of sites identified in the 2023 – 2031 Housing Element will be required to comply with the latest state and local plans. Residential development facilitated by adoption of the Housing Element will implement energy efficiency features as required by California Building Code, including the Green Building Standards Code and Energy Efficiency Code. As such, implementation of the Housing Element will not conflict with or obstruct implementation of state or local plans for renewable energy or energy efficiency. Therefore, impacts associated with adoption and implementation of the 2023 – 2031 Housing Element will be less than significant.
Mitigation Measure(s): None Required.
Town of Atherton
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5.7. GEOLOGY AND SOILS
Would the project:
Potentially
Significant
Impact
Less Than
Significant with
Mitigation
Less Than
Significant
Impact
No
Impact
a) Directly or indirectly cause potential
substantial adverse effects, including the risk
of loss, injury, or death involving:
i. Rupture of a known earthquake fault,
as delineated on the most recent
Alquist-Priolo Earthquake Fault Zoning
Map issued by the State Geologist for
the area or based on other substantial
evidence of a known fault? Refer to
ii. Strong Seismic ground shaking?
iii. Seismic-related ground failure,
including liquefaction?
iv. Landslides?
b) Result in substantial soil erosion or the loss
of topsoil?
c) Be located on a geologic unit or soil that is
unstable, or that would become unstable as a
result of the project, and potentially result in
on or off-site landslide, lateral spreading,
subsidence, liquefaction or collapse?
d) Be located on expansive soil, as defined in
California Building Code, creating substantial
direct or indirect risks to life or property?
e) Have soils incapable of adequately
supporting the use of septic tanks or
alternative waste water disposal systems
where sewers are not available for the
disposal of waste water?
f) Directly or indirectly destroy a unique
paleontological resource or site or unique
geologic feature?
Sources: Town of Atherton General Plan 2019; Town of Atherton General Plan 2019 Update Project, Draft Initial Study/ Mitigated Negative Declaration; Natural Resources Conservation Service Web Soil Survey website; Department of Conservation, Seismic Hazard Zone Report 111, 2006; MTC/ABAG Hazard Viewer Map, Earthquake Liquefaction Susceptibility, Landslide Hazard (Rainfall Induced); Town of Atherton Heritage Tree Preservation Standards and Specifications, December 2019; and California Building Code 2022.
Town of Atherton
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Geology and Soils Setting
The San Francisco Peninsula, in which Atherton is located, lies within the Coast Ranges geomorphic province, a region characterized by northwest-trending valleys and mountain ranges. This alignment of valleys and ridges has developed in response to folding and faulting along the San Andreas fault system, which includes several fault strands.6 Generally, the Town has clay loams soils that drain well.7
The San Andreas fault system is 44 miles wide and extends throughout much of the North Bay Area.
The San Andreas fault is the primary seismic threat to the Town of Atherton. Alquist-Priolo Earthquake Fault Zones are regulatory zones in which site-specific geologic studies are required to identify and avoid fault rupture hazards prior to land subdivision and/or construction of structures for human occupancy. The nearest Alquist-Priolo Fault Zones to Atherton include the San Andreas Fault Zone southwest of I-280 and the Hayward Fault Zone and Calaveras Fault Zone in the East Bay.
No active faults or Alquist-Priolo fault zones directly traverse the Town or any of the sites identified in the 2023 – 2031 Housing Element.
According to the MTC/ABAG Hazard Viewer Map, Probabilistic Earthquake Shaking Hazard, developed in conjunction with the United States Geological Survey (USGS) and the California Geological Survey (CGS), the Town of Atherton and surrounding areas are subject to severe shaking and violent shaking in the event of an earthquake occurring along regionally active faults. The probabilistic shaking scenario represents a composite shaking hazard for the Bay Area based on the probability of many different possible earthquake scenarios. The data presented represents a 10 percent in 50-year map, meaning the shaking level has a 10 percent chance of being exceeded over the next 50 years. In addition to seismic shaking hazards, liquefaction induced by seismic events is moderate in many areas of the town except for areas along the Atherton Channel, where susceptibility is identified as very high.
Applicable General Plan Objectives and Policies
The Town of Atherton’s General Plan sets forth goals, objectives, and policies intended to improve and enhance safety of new development with regard to geologic hazards, those particularly relevant to the 2023 -2031 Housing Element Update include the following:
Open Space and Conservation Element
Goal OSC-1: Protect both publicly and privately held open space lands from deterioration of their semi-rural charm, scenic value and environmental equilibrium.
Objective OSC-1.3: Endeavor to prevent soil erosion and the potential loss of topsoil through the development review process.
Policy OSC-1.1 The Town shall endeavor to protect scenic resources, significant stands of natural vegetation, wildlife habitat, public safety and significant archaeological resources, both publicly and privately held.
Goal OSC-4: Protect both publicly and privately held cultural resources from deterioration and/or destruction.
6 https://filerequest.conservation.ca.gov/?q=SHZR_111_Palo_Alto.pdf 7 Web Soil Survey https://websoilsurvey.nrcs.usda.gov/app/WebSoilSurvey.aspx Town of Atherton
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Policy OSC-4.1 Encourage the preservation of both private and public historical resources and artifacts for the benefit of future generations. Policy OSC-4.2 The Town will comply with minimum State requirements in the event archaeological or paleontological resources are discovered during construction.
Community Safety Element
Goal CS-1: The Town recognizes the potential danger to public safety that may result from natural or man-made causes and seeks to minimize the public risks in such hazards.
Goal CS-2: Reduce the risk of injury, structure and property damage from exposure to seismic activity.
Policy CS-2.1 Support the Goals, Objectives and Policies contained in adopted Atherton local hazard mitigation plans and Emergency Operations Plans. Policy CS-2.2 Public education, research and information dissemination on seismic hazards and emergency response shall be encouraged.
Policy CS-2.3 The Town shall seek to improve interjurisdictional cooperation with other agencies for geotechnical safety in land use planning, hazard prevention and emergency response.
Geology and Soils Impact Discussion
5.7(a. i) (Fault Zones) Less Than Significant Impact: Fault rupture occurs when the ground surface fractures because of fault movement during an earthquake and almost always follows preexisting fault traces, which are zones of weakness. In a seismically active region such as Northern California, there is a possibility for future faulting. However, historical occurrences of surface faulting have generally closely followed the trace of active faults (i.e., faults experiencing surface rupture in the past 11,000 years). While the San Andreas Fault Zone is less than two miles away from the Town, there are no known active faults or Alquist-Priolo fault zones that directly traverse the Town of Atherton, including sites identified in the 2023 – 2031 Housing Element.8 Further, the Town’s Community Safety Element has goals and policies that address geologic hazards to reduce the risk of injury, structure damage, and property damage. The Town adopted the California Building Code, which requires compliance with construction provisions in areas subject to seismic activity.
Therefore, impacts from future development including the risk of loss, injury, or death involving the rupture of an earthquake fault will be less than significant.
5.7(a. ii) (Ground-Shaking) Less Than Significant Impact: Based on the proximity of the Town to the San Andreas Fault, Hayward Fault, and Calaveras Fault, all of which are active faults, development within Atherton is susceptible to very strong and severe shaking associated with seismic events occurring along these active faults. As such, development of sites identified in the 2023 – 2031 Housing Element has the potential to expose people or structures to substantial adverse effects resulting from earthquake shaking and related ground failure. The resulting vibrations would likely cause primary damage to the proposed housing developments as well as secondary effects including ground failures in loose alluvium or poorly compacted fill. Both primary and secondary effects pose a potential risk of loss of life or property. 8 Atherton General Plan 2019
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The intensity of earthquake motion depends on the characteristics of the generating fault, distance to the fault, earthquake magnitude and duration, and site-specific geologic conditions. Since no physical development is proposed at this time, no site-specific soils investigations have been prepared for sites identified in the Housing Element. Upon submittal of site-specific development plans, a design level geotechnical analysis will be required in compliance with the California Building Code (CBC). Conformance with standards set forth in site-specific analyses, the Building Code of Regulations, Title 24, Part 2 (the California Building Code 3.7-20 Chapter 3: Setting, Impacts, and Mitigation Measures [CBC]) and the California Public Resources Code, Division 2, Chapter 7.8 (the Seismic Hazards Mapping Act) are required to address risks associated with seismic shaking. Design specifications in the CBC ensure that structures and improvements associated with development do not expose people or structures to substantial adverse effects, including the risk of loss, injury, or death because of seismic activity or liquefaction. With the compliance of applicable standards and codes, impacts associated with ground shaking and ground failure adversely impacted future housing development will be less than significant.
5.7 (a. iii) (Seismic-Related Ground Failure/Liquefaction) Less Than Significant Impact:
Liquefaction is a phenomenon associated with fine-grained, loosely packed sands and gravels subjected to ground shaking as a result of seismic activity. Liquefaction can lead to total and/or differential settlement and is largely dependent upon the intensity of ground shaking and response of soils underlying the site. The Association of Bay Area Governments (ABAG) Hazard Viewer Map9 indicates that the Town’s earthquake liquefaction susceptibility ranges from very low to very high.
Though a narrow area along the Atherton Channel has “very high susceptibility,” sites identified in the Housing Element Update are not located along the channel. Sites identified in the 2023 – 2031 Housing Element are in areas with very low to moderate susceptibility to seismically induced liquefaction.
Upon submittal of a building permit application for site-specific development, compliance with the California Building Code and the Atherton Municipal Code will be required, which requires preparation of a site-specific geotechnical investigation to identify site-specific geotechnical conditions, including risks of liquefaction, and conclusions and recommendations addressing grading procedures, soil stabilization, and foundation design. In addition to recommendations provided in the site-specific analyses, the foundation and structural design for future development will be required to meet the latest CBC regulations as well as state and local standards for seismic safety. Compliance with the California Building Code and Atherton Municipal Code will ensure potential impacts from future housing development including the risk of loss, injury, or death involving seismic-related ground failure and liquefaction will be less than significant.
5.7(a. iv) (Landslide) Less Than Significant Impact: The risk of landslide is dictated by several factors including precipitation, soil type, steepness of slope, vegetation, seismic conditions, and level of human disturbance. When certain conditions are present, landslides can be triggered as a result of seismic activity. According to the ABAG Hazard Viewer Map10, the area surrounding the Bear Gulch Reservoir has smaller, more scattered landslides. However, other areas within the Town are considered “flat land” and are unlikely to have a landslide event. The General Plan Community Safety Diagram indicates that there is earthquake induced landslide zones west of Alameda de las Pulgas.
Sites identified in the Housing Element for future development that are in the southwest area of the 9 Accessed on August 3, 2023
10 Accessed August 3, 2023
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Town are subject to landslide risk. However, future development of sites identified in the 2023 – 2031 Housing Element would require a geotechnical investigation per the California Building Code (CBC) and the Atherton Municipal Code. The geotechnical investigation would assess site-specific geologic hazards and would provide recommendations that would be required for project compliance11. Therefore, impacts due to loss of structures or life from landslides occurring on sites identified in the proposed Housing Element Update will be less than significant.
5.7(b) (Soil Erosion) Less Than Significant Impact: Construction associated with future development of sites identified in the proposed Housing Element may include tree removal and grading to achieve a uniform distribution of soil across individual sites. These ground disturbing activities have the potential to result in soil erosion or the loss of topsoil if not properly controlled.
Soil erosion will be controlled through implementation of best management practices (BMPs) and adherence to a Storm Water Pollution Prevention Plan (SWPPP) or Erosion/Pollution Control Plan throughout site preparation and construction activities, as further discussed in Section 5.10 Hydrology/Water Quality. Prior to issuance of a grading and drainage permit for development of sites identified in the 2023 – 2031 Housing Element, an erosion control plan is required to be submitted to the Town. The erosion control plan will detail erosion control measures such as site watering, sediment capture, equipment staging, and other erosion control measures to be implemented during construction activities. All earthwork, grading, trenching, backfilling, and compaction operations shall be conducted in accordance with the Town of Atherton’s Grading, Erosion, and Sediment Control Ordinance contained in Chapter 8.54 of the Atherton Municipal Code.
Additionally, tree removal or protection during construction shall be operated in accordance with the Removal of and Damage to Heritage Trees Ordinance in Chapter 8.10 of the Atherton Municipal Code. The Town Heritage Tree Preservation Standards and Specifications outline required measures to prevent erosion of topsoil.12 Compliance with Town regulations and the grading and drainage permit requirements, as part of the future housing development review process, will avoid potentially significant adverse effects from erosion and loss of topsoil and will ensure that impacts are less than significant.
5.7(c) (Unstable Geologic Unit) Less Than Significant Impact: Lateral spreading, lurching, and associated ground failure can occur during strong ground shaking on certain soil substrate typically on slopes. Lurching generally occurs along the tops of slopes where stiff soils are underlain by soft deposits or along steep channel banks whereas lateral spreading generally occurs where liquefiable deposits flow towards a “free face,” such as channel banks, during an earthquake. Though most sites identified for development in the proposed Housing Element are generally level and lack steep channel banks and slopes, sites located west of Alameda de las Pulgas have steep slopes and are subject to slope instability. However, future development of sites identified in the 2023 – 2031 Housing Element would require a geotechnical investigation per the California Building Code (CBC) and the Atherton Municipal Code. The geotechnical investigation would assess site-specific geologic hazards and would provide recommendations that would be required for project compliance.13 Further, development on sites west of Alameda de las Pulgas would occur on existing graded properties, with level ground. Therefore, potential impacts related to lateral spreading, lurching, and 11 https://www.ci.atherton.ca.us/DocumentCenter/View/6354/GPU-IS_MND-Final-Draft-4419 12 https://www.ci.atherton.ca.us/DocumentCenter/View/7516/HTO-Standards-and-Specs-2021-REV?bidId= 13 https://www.ci.atherton.ca.us/DocumentCenter/View/6354/GPU-IS_MND-Final-Draft-4419 Town of Atherton
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associated ground failure from future housing development on identified sites will be less than significant.
5.7(d) (Expansive Soils) Less Than Significant Impact: Expansive soils are naturally occurring and often found in low-lying regions and valley flood plains. Expansive soils, such as clay, tend to swell with increases in soil moisture and shrink as the soil moisture decreases. Changes in soil moisture content can compromise the integrity of foundations, retaining walls, and slab–on-grade improvements because of differential movements (settlement or heave). Most of the Town is underlain by alluvial soils that have low to moderately low expansion. The area west of Alameda de las Pulgas is underlain by bedrock that typically has a thin cover of soil with low to moderately low expansion potential.14 Prior to the issuance of a building permit for development proposals on housing sites identified in the 2023 – 2031 Housing Element, a design level geotechnical investigation shall be prepared. The investigation shall include an analysis of site-specific geotechnical conditions including soil composition and expansive soils. Upon the reporting of such investigations, recommendations for special design and construction provisions shall be included in order to mitigate effects of expansive soils.15 Future development projects on sites identified in the 2023 – 2031 Housing Element would be required to comply with site-specific recommendations.
Compliance with the California Building Code (CBC) and the Atherton Municipal Code will ensure that potential direct or indirect impacts to life or property due to the presence of expansive soils are minimized through design and soil treatment procedures and impacts resulting from implementation of the 2023 – 2031 Housing Element will be less than significant.
5.7(e) (Septic Tanks) Less Than Significant Impact: Sites identified for housing development in the 2023 – 2031 Housing Element are within incorporated town limits where adequate wastewater disposal systems are available. Most sites identified in the Housing Element Update are already developed and would connect to the existing sewer system. Though some sites identified for development are currently undeveloped, future development would install new sewer laterals that connect to the existing disposal system. Housing sites located on the Cal Water property could be in a rural area that lacks connection to the Town’s sewer disposal system, which would then require an individual septic system. However, San Mateo County inspection staff would be required to observe soil testing for the proposed septic system location prior to installation. Therefore, impacts resulting from soils incapable of adequately supporting the use of septic tanks or alternative wastewater disposal systems for identified sites in the 2023 – 2031 Housing Element Update would be less than significant.
5.7(f) (Paleontological Resource): Less Than Significant Impact: The Atherton General Plan does not identify the presence of any paleontological or unique geological resources within the Town.
Nevertheless, the potential remains for the inadvertent discovery of buried paleontological resources. According to the General Plan, the Town will comply with the minimum state requirements in the event that paleontological resources are found during construction activities. In compliance with state requirements, potential impacts to paleontological resources from future housing development as identified in the proposed 2023 – 2031 Housing Element Update will be less than significant.
Mitigation Measure(s): None required.
14 https://www.ci.atherton.ca.us/DocumentCenter/View/6354/GPU-IS_MND-Final-Draft-4419 15 California Building Code
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5.8. GREENHOUSE GAS EMISSIONS
Would the project:
Potentially
Significant
Impact
Less Than
Significant
with
Mitigation
Less Than
Significant
Impact
No Impact
a) Generate greenhouse gas emissions,
either directly or indirectly, that may have
a significant impact on the environment?
b) Conflict with an applicable plan, policy or
regulation adopted for the purpose of
reducing the emissions of greenhouse
gases?
Sources: Town of Atherton General Plan 2019; Town of Atherton General Plan 2019 Update Project, Draft Initial Study/ Mitigated Negative Declaration; Air Quality and Greenhouse Gas Assessment, March 7, 2024; BAAQMD 2017 Bay Area Clean Air Plan; BAAQMD Justification Report: CEQA Thresholds for Evaluating the Significance of Climate Impacts from Land Use Projects and Plans, April 2022.
Greenhouse Gas Setting
Greenhouse gases (GHGs) are generated from natural geological and biological processes and through human activities including the combustion of fossil fuels and industrial and agricultural processes. GHGs include carbon dioxide (CO2), nitrous oxide (N2O), methane (CH3), chlorofluorocarbons, hydrofluorocarbons and perfluorocarbons.
While GHGs are emitted locally, they have global implications. GHGs trap heat in the atmosphere, which warms up the surface of the Earth. This concept is known as global warming and is contributing to climate change. Changing climatic conditions pose several potential adverse impacts including sea level rise, increased risk of wildfires, degraded ecological systems, deteriorated public health, and decreased water supplies.
To address GHGs at the State level, the California legislature passed the California Global Warming Solutions Act in 2006 (Assembly Bill 32), which requires that statewide GHG emissions be reduced to 1990 levels by 2020. Executive Order S-3-05 provides the California Environmental Protection Agency with the regulatory authority to coordinate the State’s effort to achieve GHG reduction targets. S-3- 05 goes beyond AB 32 and calls for an 80 percent reduction below 1990 levels by 2050. SB 32 and Executive Order B-30-15 extended the goals of AB 32, setting GHG reduction target at 40 percent of 1990 levels by 2030. Senate Bill 375 has also been adopted, which seeks to curb GHGs by reducing urban sprawl and vehicle miles traveled.
The Air District Board of Directors adopted proposed CEQA Thresholds for Evaluating the Significance of Climate Impacts from Land Use Projects in April 2022 (Guidelines). In determining significance of a project’s impacts under CEQA, the updated guidelines state that a project would be considered to have a less than significant impact related to GHG emissions so long as it contributes its “fair share” toward achieving long-term climate goals including achieving carbon neutrality by 2045. As detailed in the Guidelines document, determining a project’s fair share analysis should focus on design elements that will help to achieve carbon neutrality by 2045. GHG emissions from the land use sector are primarily generated from building energy use and transportation, and as Town of Atherton
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such these areas need to be evaluated to ensure that the project can and will be carbon neutral.
With respect to building energy use, replacing natural gas with electric power, and eliminating inefficient or wasteful energy usage can help to achieve GHG reductions as it supports California’s transition away from fossil fuel–based energy sources and reduces the project’s building energy GHG emissions to zero, becoming 100 percent carbon free. With regard to transportation related GHG emissions, projects need to be designed to reduce project-generated VMT to the recommended 15-percent reduction below existing as well as provide sufficient electric vehicle (EV) charging infrastructure to support the shift to EVs.
The updated Guidelines do not include thresholds of significance for construction related GHG impacts as impacts from construction represent a nominal portion of a project’s lifetime GHG emissions. Thresholds for land use projects are designed to address operational GHG emissions which represent the majority of project related GHG emissions. As such, projects that incorporate design elements that contribute a fair share toward achieving long-term climate goals, or project’s that are consistent with a locally adopted GHG reduction strategy can be determined to have a less than significant GHG impact.
As such, new land use development projects are encouraged to incorporate the design elements identified in (A) to implement the State’s goals of achieving carbon neutrality by 2045, or must comply with a local GHG reduction strategy as noted in (B):
A. Projects must include, at a minimum, the following project design elements:
1. Buildings
a. The project must include electric appliances or electric plumbing, in addition to natural gas appliances or natural gas plumbing (in both residential and nonresidential development).
b. The project will not result in any wasteful, inefficient, or unnecessary energy usage as determined by the analysis required under CEQA Section 21100(b)(3) and Section 15126.2(b) of the State CEQA Guidelines.
2. Transportation
b. Achieve a reduction in project-generated vehicle miles traveled (VMT) below the regional average consistent with the current version of the California Climate Change Scoping Plan (currently 15 percent) or meet a locally adopted Senate Bill 743 VMT target, reflecting the recommendations provided in the Governor’s Office of Planning and Research's Technical Advisory on Evaluating Transportation Impacts in CEQA:
ii. Residential projects: 15 percent below the existing VMT per capita iii. Office projects: 15 percent below the existing VMT per employee iv. Retail projects: no net increase in existing VMT
c. Achieve compliance with off-street electric vehicle requirements in the most recently adopted version of CALGreen Tier 2.
B. Projects must be consistent with a local GHG reduction strategy that meets the criteria under State CEQA Guidelines Section 15183.5(b).
Atherton Climate Action Plan
The Town of Atherton Climate Action Plan, adopted by the City Council on October 19, 2016, seeks to mitigate greenhouse gas (GHG) emissions actions implementable at the local level. The Town’s Climate Action Plan identifies various emission reduction measures within different topic areas Town of Atherton
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including energy and water, transportation and land use, and solid waste. Measures set forth in the Town’s Climate Action Plan that are applicable to the 2023 – 2031 Housing Element include:
Measure EC-1: Voluntary residential green building ordinance for new construction Measure EC-2: Incorporate available Energy Upgrade programs and similar rebate Measure EC-3: Implement program for residential shade trees Measure EC-6: Community Choice Aggregation (CCA)
WTRC-1: Water conservation incentives
WTRC-2: Water conservation ordinance
WTRC-3: Voluntary water conservation programs
WC-1: Set higher community waste diversion goal
WC-3: Promotion of recycling/diversion of yard waste
In addition to the Town’s adopted Climate Action Plan, Atherton continues to require compliance with Title 24 of the California Code of Regulations, known as the 2022 California Green Building Standards Code (CALGreen). CALGreen implements an all-electric reach standard for newly constructed buildings, ADUs, guest houses, and pool houses, which is intended to reduce the generation of GHG emissions.
Applicable General Plan Goals, Objectives, and Policies The Town of Atherton’s General Plan sets forth goals, objectives, and policies intended to improve and reduce GHG emissions associated with new development, those particularly relevant to the 2023-2031 Housing Element Update include the following:
Open Space and Conservation Element
Goal OSC-3: Minimize the impacts of flooding on health, safety and property damage. Policy OSC-3.2 The Town will assure that opportunities for green infrastructure are routinely considered by all Town departments.
Goal OSC-5: Implement the GHG programs in the Atherton Climate Action Plan related to energy efficiency, community waste generation, and reduced water consumption.
Greenhouse Gas Emissions Impacts Discussion
5.8(a-b) (Significant GHG Emissions and Conflict with GHG Plan) Less Than Significant Impact with Mitigation: Though adoption of the 2023 – 2031 Housing Element and Zoning Code updates will not directly result in physical development, it is reasonably foreseeable that housing development will result from adoption of the Housing Element. GHG emissions will be generated during construction and operation of sites identified in the Housing Element. Construction will result in short-term GHG emissions from heavy-duty construction equipment, worker trips, and material delivery and hauling. GHG emissions generated during operation will primarily result from vehicular emissions associated with travel to and from the project site.
Construction
As discussed in Section 5.3 Air Quality, there is no established threshold for construction related GHG emissions as these represent a minimal part of overall emissions. However, BAAQMD has established construction BMPs to reduce GHG emissions during construction. Future development that will occur under the 2023 – 2031 Housing Element shall be required to implement Mitigation Town of Atherton
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Measure AQ-1, which would minimize GHG emission during construction. With implementation of measure AQ-1, impacts resulting from GHG emissions during construction activities of future housing development as anticipated by the Housing Element will be less than significant.
Operation
The BAAQMD thresholds for land use projects are designed to address operational GHG emissions by incorporating design elements that contribute a fair share toward achieving long-term climate goals. As stated in the Justification Report, a land use project would be considered to contribute its fair share if it would serve California’s need for housing and related infrastructure in a manner that supports the state’s goals of achieving carbon neutrality by 2045. The city’s adopted CAP does not contain projected emissions beyond 2020 and therefore, cannot be relied upon to conclude that development of housing under the 2023 – 2031 Housing Element will have a less than significant impact resulting from GHG emissions.
The Air Quality and Greenhouse Gas Assessment, prepared by Illingworth and Rodkin and dated March 7, 2024, used CalEEMod with vehicle trip generation rates and VMT to predict daily GHG emissions assuming full build-out of the projects under the Housing Element and Zoning Code updates. In terms of GHG per capita emissions, the model found there would be a decrease.
Plan Consistency
The Project would allow the addition of more housing that must meet BAAQMD project-level significance thresholds or meet the State’s goals to reduce emissions to 40 percent below 1990 levels by 2030 and carbon neutrality by 2045. As the Town has not adopted a GHG reduction strategy that is consistent with current State goals or that meets the criteria under State CEQA Guidelines Section 15183.5(b), the Air Quality and Green House Gas Assessment recommends the following measures:
1. Require all new or remodeled housing to use all-electric appliances and have no natural gas infrastructure.
2. Require all new housing to include electric vehicle charging infrastructure that meets or exceeds current Building Code CALGreen Tier 2 compliance.
3. Implement the VMT Mitigation measure for proposed projects in the “high-VMT area” that do not meet other screening requirements (i.e., generate less than 110 trips per day or located within a high-quality transit corridor). The TDM measure is described in the Atherton HEU Transportation Analysis, prepared by Hexagon, dated February 13, 2024.
However, pursuant to Section 1.3 of the Guidelines, the thresholds may not be appropriate for all projects and lead agencies may develop an alternative approach that would be more appropriate.
Further, the Guidelines note that California’s regulatory and policy response to the science of climate change are constantly evolving. An example of that continual evolution is a January 2024 decision by the 9th District Court preventing local jurisdictions from mandating new or remodeled housing to use all-electric appliances and have no natural gas infrastructure. As a result of this ruling the Town is modifying the first measure as follows and incorporating it into Mitigation Measure GHG-1:
1. Require all new or remodeled housing to include all-electric appliances and electric plumbing, in addition to any natural gas infrastructure.
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With the implementation of measure GHG-1, residential units resulting from the Project will conform to the BAAQMD project-level significance thresholds impacts, therefore leading to a less than significant GHG impact with mitigation.
Mitigation Measure(s):
GHG-1 If the Town has not adopted a GHG reduction strategy that is consistent with current State goals or that meets the criteria under State CEQA Guidelines Section 15183.5(b), then Town shall take the following actions:
1. Require all new or remodeled housing to include all-electric appliances and electric plumbing, in addition to any natural gas infrastructure.
2. Require all new housing to include electric vehicle charging infrastructure that meets or exceeds current Building Code CALGreen Tier 2 compliance.
3. Implement the VMT Mitigation measure for proposed projects in the “high-VMT area” that do not meet other screening requirements (i.e., generate less than 110 trips per day or located within a high-quality transit corridor). The TDM measure is described in the Atherton HEU Transportation Analysis, prepared by Hexagon, dated February 13, 2024.
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5.9. HAZARDS/HAZARDOUS MATERIALS
Would the project:
Potentially
Significant
Impact
Less Than
Significant
with
Mitigation
Less Than
Significant
Impact
No Impact
a) Create a significant hazard to the public or
environment through the routine transport,
use, or disposal of hazardous materials?
b) Create a significant hazard to the public or
the environment through reasonably
foreseeable upset and accident conditions
involving the release of hazardous materials
into the environment?
c) Emit hazardous emissions or handle
hazardous or acutely hazardous materials,
substances, or waste within one-quarter mile
of an existing or proposed school?
d) Be located on a site that is included on a
list of hazardous materials sites compiled
pursuant to Government Code Section
65962.5 and, as a result, would create a
significant hazard to the public or the
environment?
e) For a project located within an airport land
use plan or, where such a plan has not been
adopted, within two miles of a public airport
of public use airport, would the project result
in a safety hazard or excessive noise for
people residing or working in the project site?
f) Impair implementation of or physically
interfere with an adopted emergency
response plan or emergency evacuation
plan?
g) Expose people or structures, either directly
or indirectly, to a significant risk of loss, injury
or death involving wildland fires?
Sources: Town of Atherton General Plan 2019; Town of Atherton General Plan 2019 Update Project, Draft Initial Study/ Mitigated Negative Declaration; EnviroStor and GeoTracker Databases, Accessed August 10, 2023; County of San Mateo, Emergency Operations Plan Basic Plan; Town of Atherton Emergency Operations Plan; and Menlo Park Fire Protection District Staff Report, Consider for Adoption a Resolution Adopting the Primary Emergency Response Routes for the Menlo Park Fire Protection District, August 16, 2011.
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Hazardous Material Setting
The California Department of Toxic Substances Control (DTSC) defines a hazardous material as: “a substance or combination of substances that, because of its quantity, concentration or physical, chemical, or infectious characteristics, may either: 1) cause, or significantly contribute to an increase in mortality or an increase in serious, irreversible, or incapacitating illness; or 2) pose a substantial present or potential hazard to human health or the environment when improperly treated, stored, transported, disposed of, or otherwise managed.” Regulations governing the use, management, handling, transportation and disposal of hazardous waste and materials are administered by Federal, State and local governmental agencies. Pursuant to the Planning and Zoning Law, DTSC maintains a hazardous waste and substances site list, also known as the “Cortese List.” Title 22 of the California Code of Regulations (CCR), Division 4.5 Environmental Health Standards for the Management of Hazardous Waste, defines hazardous and special waste, identifies federal and state hazardous waste criteria, and regulates the storage, transportation, and disposal of waste. Title 22 was created to regulate the hazardous wastes generated by factories or similar sources, but soil excavated during construction may also be regulated.
Title 23 of the CCR, Division 3 State Water Resources Control Board (SWRCB) and Regional Water Quality Control Board (RWQCB), Chapter 16 California Underground Storage Tank Regulations, contains design, construction, and monitoring requirements for new underground storage tanks.
The California Department of Industrial Relations, Division of Occupational Safety and Health (DOSH) (formerly known as Cal/OSHA) is charged with enforcement of state regulation and the supervision of workplaces in California that are not under direct federal jurisdiction. State worker health and safety regulation applicable to construction workers include training requirements for hazardous waste operation and emergency response.
The 2002 Brownfields Amendments to the Comprehensive Environmental Response Compensation and Liability Act (CERCLA) requires an evaluation be performed by an environmental professional to assess a property’s liability for hazardous substances. Federal Code 40 CFR § 312.21 requires the environmental professional’s opinion to identify conditions that indicate the presence of hazardous substances on, at, in or to the subject property and identify information gaps that limit a comprehensive assessment of the extent of substance release.
Applicable General Plan Goals, Objectives, and Policies The Town of Atherton’s General Plan sets forth goals, objectives, and policies intended to minimize exposure to hazards associated with new development, those particularly relevant to the 2023-2031 Housing Element Update include the following:
Noise Element
Goal N-1: To maintain the serene atmosphere of the Town by minimizing the intrusion of noisegenerating activities. Policy N-1.1 To protect the peace, health and safety of Atherton citizens from unnecessary and unreasonable noise produced by any person, machine, animal or device.
Policy N-1.7 Recognizing that aircraft and any associated issues thereto are federally regulated, the Town will work with nearby communities and other interested agencies to Town of Atherton
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bring about a reduction of noise levels by private, military, public and commercial airplanes and helicopters.
Community Safety Element
Goal CS-1: The Town recognizes the potential danger to public safety that may result from natural or man-made causes and seeks to minimize the public risks in such hazards.
Goal CS-5: Prevent and reduce risks to property and protect residents from urban and wildland fire hazards.
Goal CS-6: Support the Town’s ability to respond effectively to natural and human-caused emergencies.
Policy CS-6.1 Support the preparation, implementation and regular update of local preparedness and evacuation plans, training and education; and multijurisdictional cooperation and communication for emergency situations. Policy CS-6.2 Continue to participate in regional emergency planning efforts. Policy CS-6.3 The emergency evacuation routes established in this General Plan Element are El Camino Real, Middlefield Road, Marsh Road, Alameda de las Pulgas, Atherton Avenue/Fair Oaks Lane, Stockbridge Avenue, Valparaiso Avenue, Glenwood Avenue, Encinal Avenue, Watkins Avenue and Ringwood Avenue.
Hazards/Hazardous Materials Impact Discussion
5.9(a, b) (Routine Transport, Upset and Accidental Release) Less Than Significant Impact:
Though adoption of the 2023 – 2031 Housing Element and Zoning Code updates will not directly result in physical development, the reasonably foreseeable development of sites identified for future development of housing will result in excavation and grading activities that could expose construction workers and the public to unknown hazardous materials present in soil or groundwater. A review of GeoTracker and Envirostor demonstrates that none of the housing sites identified in the 2023 – 2031 Housing Element are located on a cleanup site.16 Future development proposals will be individually evaluated for whether a Phase I Environmental Site Assessment (ESA), prepared in accordance with the latest ASTM protocol will be required, including a site remediation demonstrating compliance with appropriate environmental screening levels (ESL) as established by the RWQCB be completed for contamination prior to the issuance of occupancy. However, the likelihood of encountering hazardous materials is low given that development primarily includes ADUs and is located on existing residential, public services and facilities, and open space zoned properties, which are not associated with uses that involve hazardous materials.
In addition to potentially hazardous materials present in soil or groundwater, construction activities associated with development of sites identified in the Housing Element will result in the temporary presence of potentially hazardous materials including, but not limited to fuels and lubricants, paints, solvents, insulation, electrical wiring, and other construction-related materials. Although these potentially hazardous materials may be present onsite during future construction of individual housing sites, handling of such materials will be required to comply with all existing federal, state, 16 Accessed August 10, 2023
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and local safety regulations governing the transportation, use, handling, storage, and disposal of potentially hazardous materials. Additionally, prior to commencing with site preparation, a Storm Water Pollution Prevention Plan (SWPPP) or Erosion/Pollution Control Plan that identifies Best Management Practices (BMPs) will be prepared and implemented during all construction activities in accordance with the Town’s grading and drainage permit requirements. BMPs include measures to prevent spills and require onsite materials for cleanup. Furthermore, compliance with all federal and state regulations as overseen by San Mateo County’s Certified Unified Program Agency (CUPA) will also be required. With implementation of BMPs as well as compliance with applicable regulations, impacts resulting from routine transport, use, or disposal of hazardous materials during future construction of sites identified in the Housing Element will be less than significant.
Operation of residential uses facilitated through adoption of the 2023 – 2031 Housing Element may include storage and use of certain chemicals typical of household uses. These may include cleaning solvents for household maintenance, fuels and chemicals for automobile maintenance, and pesticides for landscaping purposes. These household chemicals are routinely used by residential properties and would not present a significant hazard. Therefore, use of household products at operation will be less than significant.
5.8(c) (Emit or Handle Hazardous Materials Within ¼ Mile of School) Less Than Significant Impact: Some sites identified in the Project are located on local schools such as Menlo College, Menlo School and Sacred Heart. Additionally, some sites are within 0.25 mile of an existing school.
Development resulting from implementation of the 2023 – 2031 Housing Element and Zoning Code update includes residential uses, which are not associated with production, storage, and handling of hazardous materials and waste at operation. During future construction of sites identified in the Housing Element, hazardous materials such as paints, fuels, solvents, and other construction materials may be present on a temporary basis. However, compliance with all existing federal, state, and local safety regulations governing the transportation, use, handling, storage, and disposal of potentially hazardous materials will be required. There are no activities associated with the anticipated development under the proposed Housing Element that would pose a threat to schools from the release or handling of hazardous materials. Therefore, impacts related to the emission or handling of hazardous materials within a quarter mile of a school would be less than significant.
5.9(d) (Existing Hazardous Material Sites) Less Than Significant Impact: The California Environmental Protection Agency (CAL-EPA) annually updates the California Hazardous Waste and Substances Site List (also known as the “Cortese List”). A review of GeoTracker demonstrates that none of the sites identified in the 2023 – 2031 Housing Element update are located on a cleanup site. Similarly, a review of EnviroStor, shows that none of the sites identified in the Housing Element are listed as cleanup sites. Therefore, impacts associated with existing hazardous materials sites will be less than significant.
5.9(e) (Airport Land Use Plans) No Impact: None of the sites identified for future development in the 2023 – 2031 Housing Element are located within the boundaries of an airport land use plan or in proximity to a private airstrip. The nearest operational airports are the San Carlos Airport and Palo Alto Airport located well over two miles from the Town of Atherton. Therefore, impacts associated with airport-related hazards will be less than significant.
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5.9(f) (Impair Emergency Response Plan and Emergency Evacuation Plan) Less Than Significant Impact: Implementation of the 2023 – 2031 Housing Element would not impair implementation of, or physically interfere with, an adopted emergency response plan or emergency evacuation plan.
California has developed an emergency response plan to coordinate emergency services by federal, state, and local governments, including responding to hazardous materials incidents. The State Office of Emergency Services employs a Hazardous Materials Division, which enforces multiple programs that address hazardous materials. The Town Emergency Operating Plan has emergency operating procedures for different hazards and hazardous materials. Additionally, San Mateo County has prepared the Emergency Operations Plan (EOP) which established policies and procedures to effectively manage emergency operations within the San Mateo County Operational Area (SMOA). The EOP organizes departments and agencies into emergency functions (EF) which serve to plan and coordinate effective emergency response and recovery for emergencies, including hazardous materials.17 The proposed project would not impair implementation of or physically interfere with these plans because the development that would occur is on existing parcels, is primarily low intensity in nature, and is located along existing transportation corridors that are served by low intensity residential development.
The western area of the Town has a forested and mountainous nature that presents difficulties in the event of a wildland interface fire, due to access complications. Some housing sites identified in the 2023 – 2031 Housing Element are in the western area of the Town. Though some housing sites are within this area of the Town, the Town has established an Emergency Evacuation Plan that provides emergency response information and coordination for first responders and contributing agencies. There are no aspects of the 2023 – 2031 Housing Element that will interfere with adopted emergency or evacuation plans because the development that would occur is on existing parcels, is primarily low intensity in nature, and is located along existing transportation corridors that are served by low intensity residential development. Therefore, impacts resulting from a conflict with emergency response and evacuation will be less than significant.
5.9(g) (Wildland Fire Hazards) Less Than Significant Impact: Wildland fires are of concern particularly in areas of expansive native vegetation, brush, woodland, or grassland. The Association of Bay Area Governments (ABAG) Hazard Viewer Map indicates that the Town of Atherton is not within a moderate to very high fire hazard severity zone. The western area of the Town has a hilly and forested nature that creates a greater susceptibility to wildland interface fires, with natural landscapes that present difficulty for first responders to gain control of large wildland interface fires.18 However, housing would predominantly be located in areas of existing residential development. Housing in the western area of the Town would be located on properties that are served by the Menlo Park Fire Protection District.
The Menlo Park Fire Protection District (MPFPD) is responsible for protecting life, property, and the environment from fire within the Town. The Fire Department responds to calls including structural, wildland, and other fires. The District has a five-station network that serves all areas of the Town, including all of the 2023 – 2031 Housing Element sites. The MPFPD has established primary response routes that support timely deployment of emergency resources in the event of a fire.19 Additionally, the Town has established an Emergency Evacuation Plan to increase preparedness, 17 https://hsd.smcsheriff.com/sites/default/files/downloadables/1%20-%20Emergency%20Operations%20Plan.pdf 18 https://www.ci.atherton.ca.us/DocumentCenter/View/113/Atherton-EOP-2022?bidId= 19 Menlo Park Fire Protection District Primary Response Routes Staff Report Town of Atherton
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reduce response times, and facilitate rapid evacuation in the event of a wildland interface fire or other emergency events. For these reasons, development of sites identified in the Housing Element will not increase risk of exposure due to wildland fire hazards. Therefore, impacts related to the exposure of people or structures to a significant risk of loss, injury or death involving wildland fires will be less than significant.
Mitigation Measure(s): None required.
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5.10. HYDROLOGY AND WATER QUALITY
Would the project:
Potentially
Significant
Impact
Less Than
Significant
with
Mitigation
Less Than
Significant
Impact
No
Impact
a) Violate any water quality standards or waste
discharge requirements or otherwise substantially
degrade surface or ground water quality?
b) Substantially decrease groundwater supplies or
interfere substantially with groundwater recharge
such that the project may impede sustainable
groundwater management of the basin?
c) Substantially alter the existing drainage pattern on the site or area, including through the alteration of the course of a stream or river, or through the addition of impervious surfaces, in a manner which would:
i. Result in substantial erosion or siltation on- or
off-site;
ii. substantially increase the rate or amount of
surface runoff in a manner which would result
in flooding on- or offsite;
iii. create or contribute runoff water which would
exceed the capacity of existing or planned
stormwater drainage systems or provide
substantial additional sources of polluted
runoff; or
iv. impede or redirect flood flows?
d) In flood hazard, tsunami, or seiche zones, risk
release of pollutants due to project inundation?
e) Conflict with or obstruct implementation of a water
quality control plan or sustainable groundwater
management plan?
Sources: Town of Atherton General Plan 2019; Town of Atherton General Plan 2019 Update Project, Draft Initial Study/ Mitigated Negative Declaration; San Mateo Plain Groundwater Basin Assessment, July 2018; Redwood City Bayfront Canal and Atherton Channel Flood Improvement and Habitat Restoration Project Feasibility Study; Town of Atherton Drainage Criteria, January 2, 2013; San Mateo County Water Pollution Prevention Program C.3 Regulated Projects Guide, January 2020; FEMA’s National Flood Hazard Layer (NFHL) Viewer, Accessed August 1, 2023; California Department of Conservation, San Mateo County Tsunami Hazard Areas, Accessed August 1, 2023; Department of Water Resources, Dam Breach Inundation Map, Accessed August 1, 2023; County of San Mateo Office of Sustainability website; and State Water Resources Control Board website.
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Hydrology and Water Quality Setting
The Town of Atherton is located within the Atherton Channel watershed. The Atherton Channel headwaters originate in the Town of Woodside in the hillside area west of Interstate 280. Near Marsh Road, the Bayfront Canal and the Atherton channel merge and then outlet into Flood Slough.20
Flooding
The San Mateo County Flood and Sea Level Rise Resiliency District, also known as OneShoreline, is a county-wide agency that addresses sea level rise, flooding, coastal erosion, and the region’s stormwater infrastructure. The District is responsible for working with cities and developers to plan infrastructure that can withstand future climate conditions and support regional protection efforts.
The District works with cities to update their General Plans, Specific Plans, and zoning ordinances so that these documents can guide the region’s resiliency to climate change. The Town of Atherton disaster council has powers and duties in the process of adopting emergency and mutual aid agreements under Title 2 (Administration and Personnel) of the Municipal Code.
The Federal Emergency Management Agency’s (FEMA’s) National Flood Insurance Program is intended to encourage State and local governments to adopt responsible floodplain management programs and flood measures. As part of the program, FEMA defines floodplain and floodway boundaries that are shown on the Flood Insurance Rate Maps (FIRMs).
Water Quality
Surface water quality is regulated by the San Francisco Bay RWQCB (Region 2) via the Water Quality Control Plan for the San Francisco Bay Region (Basin Plan). The RWQCB is responsible for implementing Section 401 of the Clean Water Act through the issuance of a Clean Water Certification when development includes potential impacts to jurisdictional areas such as creeks, wetlands, or other Waters of the State.
Dischargers whose projects disturb one or more acres of soil, or whose projects disturb less than one acre, but are part of a larger common plan of development that in total disturbs one or more acres, are required to obtain coverage under the General Permit for Discharges of Storm Water Associated with Construction Activity, Construction General Permit Order 2009-0009-DWQ from the State Water Resources Control Board.21 Construction activity subject to this permit includes clearing, grading, and disturbances to the ground such as stockpiling, or excavation. The Construction General Permit requires development of a Storm Water Pollution Prevention Plan (SWPPP). The SWPPP includes specifications for Best Management Practices (BMPs) to be implemented during construction activities to control potential discharge of pollutants from the construction area.
Additionally, a SWPPP describes measures to prevent pollutants in runoff during project operation and includes a plan for inspection and maintenance of the project facilities to ensure proper operation and maintenance continues throughout the life of the project. 20 DRAFT_Appendix-D-Bayfront-Vista-Grande-Canal-Projects.pdf 21 State Water Resources Control Board, Construction General Permit Order 2009-0009-DWQ, as amended by Order 2010- 0014-DWQ, and order 2012-00060DWQ NPDES General Permit No. CAS000002. http://www.waterboards.ca.gov/water_issues/programs/stormwater/construction.shtml, Accessed February 10, 2020.
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Groundwater
Atherton is situated in the San Mateo Plain Groundwater Subbasin as identified by the California Department of Water Resources. The State of California adopted the Sustainable Groundwater Management Act (SGMA) in 2014 which called for the creation of local Groundwater Sustainability Agencies (GSAs), who are charged with development and implementation of Groundwater Sustainability Plans to address long-term management of healthy and functioning groundwater resources. According to the County of San Mateo Office of Sustainability website, all nine basins within the County are considered a Very Low Priority and are not required to comply with SGMA. In 2018, the San Mateo County Office of Sustainability and Environmental Health Services completed the San Mateo Plain Groundwater Basin Assessment (Project). The groundwater basin assessment evaluated the groundwater resources and the subbasin’s condition. The primary objectives of the assessment are to increase public knowledge, evaluate hydrogeological and groundwater conditions, identify potential impacts, evaluate potential impacts to groundwater quality and quantity, and develop potential groundwater management strategies.22 Stormwater Runoff
The Town’s Storm Water Management and Discharge Control (Chapter 8.50 of the Municipal Code) regulates stormwater runoff. Section 8.50.020 (E)(3) (C) of the Municipal Code addresses best management practices for new developments and redevelopment activities. Best Management Practices (BMPs) requirements minimize the discharge and transport of pollutants in stormwater runoff. New development is required to mimic pre-developed conditions, protect water quality, and retain runoff from impervious surfaces onsite and discharge in a manner consistent with historic flow rates.
Applicable General Plan Goals, Objectives, and Policies The Town of Atherton General Plan identifies goals, objectives, and policies intended to limit impacts of development on hydrology and flooding, particularly addressing areas located within or adjacent to a designated floodplain (e.g., areas adjacent to the Atherton Channel) or areas at risk of being flooded in the event of dam failure. As shown in Figure SC-1 (Community Safety Diagram) of the General Plan, housing sites identified in the 2023 – 2031 Housing Element may be subject to inundation in the event that the Bear Gulch Reservoir undergoes a dam failure. The Town’s General Plan goals, objectives, and policies related to hydrology and water quality, those particularly relevant to the 2023-2031 Housing Element Update include the following:
Land Use Element
Goal LU-1: To preserve the Town’s character as a scenic, semi-rural, thickly-wooded residential area with abundant open space.
Objective LU-1.3: To retain the quality of life, character and existing in the Town’s residential neighborhoods.
Policy LU-1.5 Proposed residential subdivisions as well as proposals to replace existing homes, shall adhere to the following design criteria:
Adequate drainage and off-street parking shall be provided. 22 San Mateo Plain Subbasin Groundwater Assessment
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Residential improvements shall follow the model policies developed for the San Mateo Countrywide Stormwater Pollution Prevention Program and the Town’s Green Infrastructure Plan to minimize the discharge of pollutants into the waterways.
Policy LU-1.9 Identify and implement green infrastructure opportunities for stormwater management including those recognized in the Town’s Green Infrastructure Plan. Green infrastructure facilities should reflect the Town’s visual semi-rural character.
Open Space and Conservation Element
Goal OSC-3: Minimize the impacts of flooding on health, safety and property damage. Policy OSC-3.1 New development shall provide detention volume to attenuate any increase in stormwater runoff caused by increased imperviousness created by the proposed development.
Policy OSC-3.2 The Town will assure that opportunities for green infrastructure are routinely considered by all Town departments.
Community Safety Element
Goal CS-1: The Town recognizes the potential danger to public safety that may result from natural or man-made causes and seeks to minimize the public risks in such hazards.
Goal CS-3: Reduce hazards related to natural flooding and potential inundation from failure of the Bear Gulch Reservoir Dam.
Goal CS-4: Support any Town Green Infrastructure programs that address stormwater infrastructure that may use natural processes to manage water and create healthier urban environments.
Hydrology and Water Quality Impact Discussion
5.10(a) (Violations of Water Quality Standards) Less Than Significant Impact: Though adoption of the 2023 – 2031 Housing Element and Zoning Code updates will not directly result in physical development, construction activities associated with future development of sites identified for housing development have the potential to result in runoff containing sediment and other pollutants that could degrade water quality if not properly controlled. Sources of potential pollution associated with construction include fuel, grease, oil and other fluids, concrete, sediment, and litter.
These pollutants have the potential to result in impacts due to chemical contamination from the use of construction equipment and materials that could pose a hazard to the environment or degrade water quality if not properly managed. Additionally, if not properly designed, stormwater runoff at operation also has the potential to violate water quality standards.
Construction
To ensure that proper controls and treatment are in place to prevent runoff of stormwater, future development of sites identified in the Housing Element, with a ground disturbance area greater than one acre, will be required to adhere to NPDES requirements including preparation and implementation of a SWPPP and compliance with the RWQCB Waste Discharge Requirements. The purpose of the SWPPP is to identify potential sediment sources and other pollutants and prescribe Best Management Practices (BMPs) to ensure that potential adverse erosion, siltation, and contamination impacts would not occur during construction activities. The Town’s ordinance Storm Town of Atherton
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Water Management and Discharge Control (Chapter 8.50 of the Town’s Municipal Code) provides guidance to ensure future health, safety and general welfare of town citizens pursuant to and consistent with the Clean Water Act. Section 8.50.20 (E)(3) of the ordinance would require each housing site development to comply with BMPs that would minimize discharge and the transport of pollutants from construction sites.
The RWQCB has adopted water quality objectives in its Stormwater Quality Management Plan, which is designed to ensure that stormwater achieves compliance with receiving water limitations. The Town has adopted a Grading, Erosion and Sediment Control ordinance (Chapter 8.54 of the Town’s Municipal Code) to ensure new development complies with the Stormwater Quality Management Plan. Consistent with the Municipal Code, the project is subject to a grading and drainage permit application prior to project implementation. The application requires the inclusion of a work schedule that outlines the installation of interim and permanent erosion and sediment control devices where required. For housing sites with future development that results in less than 1 acre of disturbance, an Erosion/Pollution Control Plan (EPCP) is required for submittal as part of the grading and drainage permit review.23 Further, all future development will be subject to General Plan goals, objectives, and policies that will ensure water quality and waste discharge will not substantially degrade surface and/or ground water quality during construction activities. With implementation of a SWPPP, ECPC, conformance with the General Plan, and compliance with the Town’s Municipal Code, potential violations of water quality standards associated with construction activities of sites identified in the Housing Element Update will be less than significant.
Operation
Development of sites identified in the 2023 – 2031 Housing Element and Zoning Code update will contribute typical, urban, nonpoint-source pollutants to the stormwater system at operation. Some future housing developments on sites identified in the 2023 – 2031 Housing Element Update could create and/or replace 10,000 or more square feet of impervious surfaces and thus would be subject to Provision C.3 of the Municipal Regional Stormwater Permit (MRP).24 Under Provision C.3, projects are required to implement pollutant source controls, site design measures, stormwater treatment and hydromodification management (HM) that will effectively control stormwater. Further, all future development will be subject to General Plan goals, objectives, and policies that will ensure water quality and waste discharge will not substantially degrade surface and/or ground water quality as a result of their operations. With implementation of Operation and Maintenance requirements of Provision C.3, as well as consistency with the Town’s General Plan, potential impacts to water quality resulting from ongoing operation of housing sites identified in the 2023 – 2031 Housing Element will be less than significant.
5.10(b) (Groundwater Supply and Recharge) Less Than Significant Impact: Though adoption of the 2023 – 2031 Housing Element and Zoning Code updates will not result in direct physical development; adoption will facilitate future development on identified sites. Future development of sites identified in the Housing Element will receive water from the City and County of San Francisco Hetch Hetchy System. The Town General Plan addresses that the groundwater is a sub-regional resource used for irrigation purposes by some properties within the Town. There are concerns regarding the reliance of local groundwater for landscape irrigation due to a history of drought and 23 https://www.ci.atherton.ca.us/DocumentCenter/View/281/DrainageCriteria_000?bidId= 24 https://www.flowstobay.org/wp-content/uploads/2020/03/SMCWPPP-C.3-Regulated-Project-Guide-High-Res_021220_0.pdf Town of Atherton
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the increased installation of wells. However, the General Plan includes policies that implement Green Infrastructure, which at a project site level would help soak, infiltrate, and store water.
Additionally, Chapter 8.32 of the Municipal Code requires that one applies for and obtains a groundwater use permit prior to operating a well within the Town. Section 8.32.060 outlines requirements for the groundwater use permit which includes an annual record of water usage to the Town unless it is not requested. As such, impacts resulting from use of groundwater supply will be less than significant.
According to the General Plan, the Town is primarily built-out and therefore future residential development would not result in a substantial increase in impervious surfaces. There are stormwater control measures in place if sites identified for development introduce impervious surfaces. Where applicable, C.3 requirements will implement stormwater control measures, also known as permanent post-construction stormwater controls.25 Consistent with the C.3 Regulated Projects Guide26, post-construction stormwater management requires use of Low Impact Development (LID) strategies, which aim to mimic pre-development conditions including recharge to groundwater. With compliance of Provision C.3, impacts to groundwater recharge from future housing development on sites identified in the House Element Update will be less than significant.
5.10(ci-iv) (Drainage Pattern, Runoff and Storm Drain Capacity) Less Than Significant Impact:
Adoption of the 2023 – 2031 Housing Element and Zoning Code updates will not directly result in physical development of housing, but rather will facilitate future development of sites identified in the Housing Element Update. As described, the Town is primarily built-out and therefore future residential development would not result in a substantial increase in impervious surfaces. Upon review of a grading and drainage permit, site-specific development for sites identified in the Housing Element Update shall provide a SWPPP or EPCP. The SWPPP or EPCP would include effective BMPs to control erosion, sediment and runoff.27 While future development may introduce impervious surfaces, stormwater management plans and compliance with General Plan goals, objectives, and policies would ensure that future development under the Housing Element will not substantially alter existing drainage patterns such that on- or off-site erosion, siltation, or flooding would occur.
General Plan goals, objectives and policies are designed to prevent the creation or contribution of runoff water which would exceed the capacity of existing or planned stormwater drainage systems, provide substantial additional sources of polluted runoff, and prevent the degradation of water quality. Therefore, the proposed Project would result in less-than-significant impacts to existing or planned stormwater drainage systems, would not result in substantial additional sources of polluted runoff, and would not result in substantial degradation of water quality.
The general direction and pattern of drainage following future development of sites identified in the 2023 – 2031 Housing Element will be required to match pre-development conditions. Additionally, stormwater management plans will be required to demonstrate that runoff resulting from development of sites identified in the Housing Element will not exceed the capacity of stormwater drainage systems, contribute sources of polluted runoff, or impede or redirect flood flows. With implementation of the Town’s grading regulations and permit requirements, impacts to the existing drainage pattern will be less than significant.
25 https://www.flowstobay.org/wp-content/uploads/2020/03/SMCWPPP-C.3-Regulated-Project-Guide-High-Res_021220_0.pdf 26 https://www.flowstobay.org/wp-content/uploads/2020/03/SMCWPPP-C.3-Regulated-Project-Guide-High-Res_021220_0.pdf 27 https://www.ci.atherton.ca.us/DocumentCenter/View/281/DrainageCriteria_000?bidId= Town of Atherton
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5.9(d) (Flood Hazard, Seiche, Tsunami, Mudflow) Less Than Significant Impact: Sites identified in the 2023 – 2031 Housing Element are in FEMA Zone X, Other Areas, which are defined as areas outside the 100- and 500-year floodplain, representing minimal flood hazard risks.28 As such, future development facilitated by adoption of the Housing Element will not construct housing within a 100- year floodplain and therefore there will be a less than significant impact resulting from flood hazards that could risk release of pollutants due to inundation.
Sites identified in the 2023 – 2031 Housing Element are not located within areas that could be affected by seiche, tsunami, or mudflow. Furthermore, according to the California Department of Conservation, no portion of the Town of Atherton is within a tsunami hazard area.29 Therefore, there will be no impact resulting from location within a seiche, tsunami, or mudflow zone that could risk release of pollutants due to inundation.
The failure of Bear Gulch Reservoir Dam risks temporary inundation within the Town of Atherton.
Though some of the identified sites in the 2023 – 2031 Housing Element are located within the Department of Water Resources’ projected Bear Gulch Reservoir Dam inundation area30, the California Division of Safety of Dams (DSOD) routinely inspects the dam performance and potential problems. In the event of potential dam failure, the dam owner takes mitigating actions in its Emergency Action Plan, which includes the reduction of the water level to minimize water loss. As a result, there will be a less than significant impact resulting from location within a dam inundation zone that could risk release of pollutants due to inundation.
5.10(e) (Conflict with Water Quality or Groundwater Plan) Less Than Significant Impact:
Implementation of the 2023 – 2031 Housing Element and Zoning Code updates will not conflict with a water quality control plan. As described above, implementation of SWPPPs and EPCPs will prevent water quality impacts throughout all stages of construction. Therefore, impacts due to a conflict with a water quality control plan will be less than significant.
The Town of Atherton is within the San Mateo Plain Subbasin, which is considered a very low priority and therefore not required to comply with the Sustainable Groundwater Management Act (SGMA).31 The adoption of the 2023 – 2031 Housing Element would not result in the physical development of housing. However, future development of sites identified in the 2023 – 2031 Housing Element would be subject to the groundwater regulations outlined in the Water Wells Ordinance (Chapter 8.32 of the Municipal Code). Local groundwater use in the Town is for landscape irrigation; therefore, construction activities would not deplete groundwater resources. While the Town is primarily builtout, and most identified sites in the 2023 – 2031 Housing Element would be located on properties with existing uses, the small-scale nature and location of housing on existing impervious surfaces would not prohibit the infiltration of water to the ground water supply. Further, sites are subject to Provision C.3 of the MRP, where applicable, which requires the implementation of LID strategies that aim to mimic pre-development conditions including recharge to groundwater. Therefore, impacts 28 FEMA, FEMA’s National Flood Hazard Layer (NFHL) Viewer, https://hazardsfema.maps.arcgis.com/apps/webappviewer/index.html?id=8b0adb51996444d4879338b5529aa9cd&extent=- 123.2922265703618,36.48226663934735,-121.50969483208144,37.578551061715665, Accessed August 1, 2023 29 California Department of Conservation, San Mateo County Tsunami Hazard Areas, https://www.conservation.ca.gov/cgs/tsunami/maps/san-mateo, Accessed August 1, 2023 30 Department of Water Resources, Dam Breach Inundation Map, https://fmds.water.ca.gov/webgis/?appid=dam_prototype_v2, Accessed August 1, 2023 31 https://www.smcsustainability.org/water/groundwater/ Town of Atherton
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resulting from a conflict or obstruction with a sustainable groundwater management plan will be less than significant.
Mitigation Measure(s): None Required.
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5.11. LAND USE AND PLANNING
Would the project:
Potentially
Significant
Impact
Less Than
Significant
with
Mitigation
Less Than
Significant
Impact
No Impact
a) Physically divide an established
community?
b) Cause a significant environmental
impact due to a conflict with any land
use plan, policy, or regulation adopted
for the purpose of avoiding or mitigating
an environmental effect?
Sources: Town of Atherton General Plan 2019; Town of Atherton General Plan 2019 Update Project, Draft Initial Study/ Mitigated Negative Declaration; California Department of Housing and Community Development: Affirmatively Furthering Fair Housing (April 2021)
Land Use and Planning Setting
The Town of Atherton covers a total of approximately 5.6 square miles. As shown in Figure LU-1 of the Land Use Element of the General Plan, land uses in the Town are comprised primarily of singlefamily residential (89%), parks and open space (5%) and public and private schools and municipal facilities (6%).32
In 2016, California adopted SB 1000 which requires cities and counties to adopt Environmental Justice Elements in their general plans if they are updating two or more major sections of their general plan at the same time, and have at least one community vulnerable and/or exposed to high levels of pollution. Although the Town is pursuing the Project analyzed in this Initial Study, while also initiating an update to the Town’s Safety Element; the Town does not have any communities that are vulnerable and/or exposed to high levels of pollution. The Department of Housing and Community Development (HCD) identifies the Town as a ‘Racially Concentrated Area of Affluence’ (RCAA) because it has a population that is more than 80 percent white and a median household income that is $125,000 or greater (slightly more than double the national median household income in 2016). HCD’s 2021 Affirmatively Further Fair Housing memo identifies RCAAs as an indication of segregation, with polarity between race, poverty, and affluence, which can be a product of policies such as restrictive low-density zoning. Local jurisdictions are encouraged to use this designation to understand trends, patterns, policies, practices and conditions in the AFFH analysis of Housing Elements.
Applicable General Plan Objectives and Policies
The Town of Atherton’s General Plan sets forth goals, objectives, and policies related to land use, those particularly relevant to the 2023 -2031 Housing Element Update include the following:
32 Town of Atherton General Plan
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Land Use Element
Goal LU-1: To preserve the Town’s character as a scenic, semi-rural, thickly-wooded residential area with abundant open space.
Objective LU-1.2: To limit the nature of land uses to those which are compatible with the overall land use planning goal LU-1.
Objective LU-1.3: To retain the quality of life, character and existing in the Town’s residential neighborhoods.
Policy LU-1.1 Future plans for residential development or redevelopment are severely limited due to the fact that the Town is almost entirely developed. Policy LU-1.2 The development of high density and/or high-rise residential structures or commercial uses of any kind would destroy the scenic, semi-rural and open space character of the Town, and is, therefore, prohibited.
Policy LU-1.3 Minimum new lot sizes in hillside areas (defined as areas with average cross slopes greater than 20 percent) shall be related to the slope and shall not be less than:
0 – 19% cross slope is a minimum lot size of 1 acre
20 – 34.9% average cross slope is a minimum lot size of 2 acres 35% + average cross slope is a minimum lot size of 5 acres Policy LU-1.4 Structures higher than 34 feet shall be prohibited. Policy LU-1.5 Proposed residential subdivisions as well as proposals to replace existing homes, shall adhere to the following design criteria:
Maintenance of existing neighborhood environments shall be promoted by the design of the subdivision and subdivision improvements. Designs shall be visually harmonious and compatible with neighborhood character.
Adequate drainage and off-street parking shall be provided. Street lighting shall be kept to a minimum. Temporary or guest on-street parking areas shall be minimized.
Land Use Element – January 2020 IV LU-15
Uniformity of lot design should be avoided by using such techniques as meandering streets.
Trees shall be preserved to the maximum extent feasible while allowing for construction within established parameters for setbacks and lot coverage in accordance with the Municipal Code chapter regulating removal of and damage to heritage trees.
Residential land uses shall be designed in accordance with the density, floor area ratio, height, bulk and other standards established by the Town. All utilities installed in conjunction with new subdivisions shall be placed underground.
Residential land uses shall be consistent with the goals, objectives and policies of the Atherton General Plan Housing Element.
Accessory dwelling units are permitted when consistent with adopted standards. Privacy is a factor which shall be incorporated into subdivision, subdivision improvements and home design.
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The Town allows minimum lot size subdivisions only where such minimum lot sizes do not significantly degrade established levels of privacy, wooded areas, and/or the open space environment.
Residential improvements shall follow the model policies developed for the San Mateo Countrywide Stormwater Pollution Prevention Program and the Town’s Green Infrastructure Plan 6 to minimize the discharge of pollutants into the waterways.
Policy LU-1.7 Land uses which diminish the open space character of the Town, such as commercial and high-density residential uses, shall be prohibited. Policy LU-1.8 Maximize preservation of heritage trees and existing trees within a development site to the greatest degree feasible, consistent with the Heritage Tree Ordinance and Tree Preservation Standards and Specifications. Require new development to comply with the Town’s requirements for tree protection, removal, and replacement.
Policy LU-1.9: Identify and implement green infrastructure opportunities for stormwater management including those recognized in the Town’s Green Infrastructure Plan. Green infrastructure facilities should reflect the Town’s visual semi-rural character.
Noise Element
Goal N-1: To maintain the serene atmosphere of the Town by minimizing the intrusion of noisegenerating activities. Policy N-1.2 Noise contours have been prepared in accordance with Section 65302(f) of the government Code and accompanies this Element. The noise contours shall be used as a tool for land use decision making.
Open Space and Conservation Element
Goal OSC-1: Protect both publicly and privately held open space lands from deterioration of their semi-rural charm, scenic value and environmental equilibrium.
Objective OSC-1.1 Preserve presently existing open space, wildlife and vegetation.
Objective OSC-1.2 Prevent developmental encroachment on open space and sensitive environmental resources.
Policy OSC-1.3 Holbrook-Palmer Park shall serve as the Town’s primary outdoor recreational facility subject to the following conditions:
The property shall not be used, occupied or operated for commercial or housing purposes except those which are strictly incidental and appropriate to its use as a public recreational park.
Policy OSC-1.2 The Town seeks to preserve the open space characteristics of existing public and private schools, churches, the Menlo Circus Club, the Bear Gulch Reservoir property and the public parks.
Land Use and Planning Impact Discussion
5.10(a) (Divide an Established Community) No Impact: Division of an established community typically occurs when a new physical feature, such as an interstate, railroad, or similar feature Town of Atherton
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physically transects an area, thereby removing mobility and access within an established community. The division of an established community can also occur through the removal of an existing road or pathway, which would reduce or remove access between a community and outlying areas.
Adoption of the 2023 – 2031 Housing Element, Zoning Code updates, and the Inclusionary Housing Ordinance will facilitate residential development on vacant and developed sites within Town limits in a dispersed manner. Development of sites identified in the Housing Element will not physically divide an established community. Rather, the expansion of housing typologies facilitated by the Project will provide for greater housing choices and options consistent with AFFH and environmental justice polices enacted by the State. Future development will also be consistent with the Town’s existing and planned development patterns because development would not include the removal or addition of a physical feature (e.g., interstate, railroad, or similar feature). Therefore, the adoption and implementation of the 2023 – 2031 Housing Element and Zoning Code updates will result in no impact due to the physical division of an established community.
5.10(b) (Land Use Plan, Policy, Regulation Conflict) Less Than Significant Impact: As discussed in detail throughout this document, the 2023 – 2031 Housing Element, Zoning Code updates and Inclusionary Housing Ordinance are consistent with the Atherton General Plan, Zoning Ordinance as proposed to be amended, Climate Action Plan, and other applicable planning documents. Adoption of the proposed Housing Element will involve density increases to the existing land use designations to facilitate housing in the Town. However, these amendments are consistent with the Town of Atherton’s General Plan. Proposed housing on land designated as Park and Open Space will be confined to existing, paved, developed areas, thereby preserving all existing park and open space areas. The proposed zoning overlays up to RM-40 will facilitate higher intensity attached single family housing and lower density multi-family units. These zoning changes are consistent with Policy LU-1.7 because the densities are not typical of those required for higher intensity multi-family developments. Modifications to LU-1.4 to allow for building heights within the Town facilitate infill development at higher densities to achieve the Town’s housing goals. Zoning code updates also retain building setbacks from the road and require landscape screening to protect the scenic vistas on the Town’s roadways. As documented in this IS/MND, these changes will not have a significant impact because any housing development proposed will be evaluated for and consistent with the General Plan, which reduces environmental impacts to less than significant levels.
The adoption of the inclusionary housing ordinance would require the construction of affordable housing units or payments of an in-lieu fee that would finance development of affordable housing within the town. The construction of affordable units that are financed through the inclusionary program would conform to the objective design standards and zoning requirements established through implementation of the Project and would not result in a new impact.
The Project will facilitate ministerial review and approval for all housing sites, as permitted by state law, unless they otherwise require discretionary actions.33 Pursuant to CEQA Guidelines Section 15268, ministerial projects are exempt from the requirements of CEQA. In the event that a project that is facilitated by the Housing Element and Zoning Code updates is eligible for ministerial review, 33 If a project that is facilitated by the Housing Element and Zoning Code updates requires discretionary actions, it may be an indication that the project requires further CEQA analysis and exceeds the scope of impacts analyzed in this Initial Study. This determination will be made upon submittal of the project and preliminary review.
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any mitigation measures identified in this Initial Study will not apply. Additionally, if the site remains privately owned, the Town cannot conduct mitigation on its own.
The 2023 – 2031 Housing Element includes housing sites that have been identified to accommodate housing development to meet the City’s RHNA allocation. As previously stated, adoption of the Housing Element will not result in direct housing construction but will facilitate future housing development. Future housing development facilitated by the Housing Element will occur as market conditions allow and at individual property owner discretion. Upon submittal of site-specific development proposals, compliance with mitigation measures set forth herein will be required.
Mitigation measures have been identified to ensure consistency with applicable federal, state, regional, and local policies and regulations including those intended to avoid or mitigate environmental impacts. Furthermore, the Housing Element is required to comply with applicable State Housing laws. As such, adoption and implementation of the 2023 – 2031 Housing Element will be consistent with applicable land use and planning policies at the federal, state, regional, and local levels, including consistency with the General Plan. Future housing development facilitated by the 2023 – 2031 Housing Element will therefore be consistent with all applicable land use and planning policies and regulations intended to minimize environmental effects and impacts will be less than significant.
Mitigation Measure(s): None Required.
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5.12. MINERAL RESOURCES
Would the project:
Potentially
Significant
Impact
Less Than
Significant
with
Mitigation
Less Than
Significant
Impact
No Impact
a) Result in the loss of availability of a
known mineral resource that would be of
value to the region and the residents of
the state?
b) Result in the loss of availability of a
locally-important mineral resource
recovery site delineated on a local general
plan, specific plan or other land use plan?
Sources: Town of Atherton General Plan 2019; Town of Atherton General Plan 2019 Update Project, Draft Initial Study/ Mitigated Negative Declaration
Mineral Resources Setting
According to the Town’s General Plan, there are no known mineral resources within the Town.
Additionally, there are no locally important mineral resource recovery sites within the Town, nor are any such sites delineated on the Town’s General Plan.
Applicable General Plan Goals, Objectives, and Policies The Town of Atherton is in an urban area with no known mineral resources or other similar natural resources. Therefore, the Town’s General Plan does not set forth goals, objectives, or policies related to mineral resources.
Mineral Resources Impact Discussion
5.12(a-b) (Mineral Resources or Resource Plans) No Impact: The housing sites identified in the 2023 – 2031 Housing Element have not been delineated as locally important mineral resource recovery sites on the General Plan or other plans. The Atherton Municipal Code does not include ordinances that regulate the conservation or use of mineral resources in the Town because there are no mineral resources in the Town of Atherton that are of value to the region, residents, or state.
Therefore, the proposed housing sites would not result in the lack of availability of valued mineral resources or locally-important mineral resource recovery sites a result of adoption and implementation of the 2023 – 2031 Housing Element and would have no impact on mineral resources.
Mitigation Measure(s): None Required.
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5.13. NOISE
Would the project result in:
Potentially
Significant
Impact
Less Than
Significant
with
Mitigation
Less Than
Significant
Impact
No Impact
a) Generation of a substantial temporary
or permanent increase in ambient noise
levels in the vicinity of the project in
excess of standards established in the
local general plan or noise ordinance, or
applicable standards of other agencies?
b) Generation of excessive groundborne
vibration or groundborne noise levels?
c) For a project located within the vicinity
of a private airstrip or an airport land use
plan or, where such a plan has not been
adopted, within two miles of a public
airport or public use airport, would the
project expose people residing or working
in the project site to excessive noise
levels?
Sources: Town of Atherton General Plan 2019; Town of Atherton General Plan 2019 Update Project, Draft Initial Study/ Mitigated Negative Declaration; Noise and Vibration Assessment: 2023-2031 Housing Element, prepared by Illingworth and Rodkin, Inc., January 18, 2024; City/County Association of Governments of San Mateo County, Comprehensive Airport Land Use Compatibility Plan for the Environs of San Carlos Airport, October 2015; and Transit Noise and Vibration Impact Assessment Manual, prepared by the Federal Transit Administration, September 2018.
Noise Setting
Noise is generally defined as unwanted sound. It is characterized by various parameters that include the rate of oscillation of sound waves (frequency), the speed of propagation, and the pressure level or energy content (amplitude). The sound pressure level is the most common descriptor used to characterize the loudness of an ambient (existing) sound level. The decibel (dB) scale is used to quantify sound intensity but given that the human ear is not equally sensitive to all frequencies in the entire spectrum, noise measurements are weighted more heavily for frequencies to which humans are sensitive in a process called “A-weighting,” written as “dBA” and referred to as “Aweighted decibels”. In general, humans typically cannot perceive the change in level of 1 dB, a change of 3 dB is just noticeable, a change of 5 dB is clearly noticeable, and a change of 10 dB is perceived as doubling the sound level.
The primary source of community noise in Atherton derives from transportation sources.34 Traffic noise exists in varying degrees throughout the community. Other localized sources of noise include the Caltrain Railroad and noises from the flights to and from San Francisco International, San Carlos, 34 Atherton General Plan
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and Palo Alto Airports are noticeable within the Town of Atherton. Atherton is generally a quiet community, consisting of primarily residential areas. To retain the semi-rural and quiet character of the community, the Town will use land use compatibility guidelines during the planning and development decision-making.
Section 15.40.120 of the Atherton Municipal Code limits professional construction activities within the Town to 8:00 a.m. to 5:00 p.m. Monday through Friday. As shown in the Town of Atherton General Plan, Table N-2 Land Use Compatibility for Community Environments, low-density, singlefamily homes are considered normally acceptable in areas with exterior noise levels of up to 60 dB and conditionally acceptable in areas with exterior noise levels of up to 65 dBA. It is normally unacceptable for low density, single family residential use in areas with exterior noise levels between 65 to 75 dBA. This residential land use is considered unacceptable in areas with an exterior noise level above 75 dBA.
In 2016, the Atherton Fair Oaks Quiet Zone was established, which designated quiet zones for portions of a rail line that contains one or more consecutive public highway-rail grade crossings. At these zones, locomotive horns are not routinely sounded, unless there is an emergency. The Fair Oaks Lane Quiet Zone was extended in 2022.
The existing noise level during a typical weekday afternoon range from 40 – 57 dBA, as shown on L90 measurements. Areas surrounding El Camino Real and Caltrain Railroad right-of-way are primary areas where noise levels reach between 60 – 70 decibels. Traffic found on Interstate 280 and US 101 contributes to the noise levels in the Atherton community. Occasionally, when flying at lower elevation, flights from and to San Carlos and Palo Alto Airports can disturb Atherton residents.
Between 2013 and 2018, a small private airline had flights that landed in San Carlos Airport and became a source of many noise complaints. Aircraft noise levels were measured in 2015 and 2018 and the maximum noise level measurements reached between Lmax 61 and 73 dBA. By 2018, the number of daily flights from the small private airline reduced significantly.
Applicable General Plan Goals, Objectives, and Policies Noise Element
Goal N-1: To maintain the serene atmosphere of the Town by minimizing the intrusion of noisegenerating activities. Policy N-1.1 To protect the peace, health and safety of Atherton citizens from unnecessary and unreasonable noise produced by any person, machine, animal or device.
Policy N-1.2 Noise contours have been prepared in accordance with Section 65302(f) of the government Code and accompanies this Element. The noise contours shall be used as a tool for land use decision making.
Policy N-1.3 If complaints about noise increase in the future, procedures for dealing with complaints in the community will be established.
Policy N-1.4 Minimum Contents of Acoustical Reports – Site specific reports should contain a brief description of the project and the sensitivity of the land use type to noise, an accurate map describing the setting with surrounding uses and noise sources identified, and a quantitative description of the noise environment. For multi-story structures, the report should discuss noise effects for the upper floors. Field noise Town of Atherton
2023 – 2031 Housing Element 93 Initial Study/Mitigated Negative Declaration 2474551.1 14537.003
sample measurements should be taken over several days and the average Ldn calculated should be based on daytime, evening and nighttime readings. If the project is located within the vicinity of a previously collected measurement, as shown on the contour map, a measurement should also be duplicated at that point for purposes of updating the Community Noise Level Contour Map.
Policy N-1.5 Qualifications for Preparing an Acoustical Report – Noise reports should be prepared by an acoustical engineer holding a degree in engineering, architecture, physics or allied discipline able to demonstrate a minimum of two years of experience in the following areas of acoustics: transportation noise forecasting, building acoustics, field measurement of noise and noise mitigation.
Policy N-1.6 Consider requiring noise mitigation for a project that results in Ldn increases that are:
5 dBA or greater and the future Ldn is less than 60 dBA, or 3 dBA or greater and the future Ldn is 60 dBA or greater and less than 65 dBA, or 1.5 dBA or greater and the future Ldn is 65 dBA or greater. Policy N-1.7 Recognizing that aircraft and any associated issues thereto are federally regulated, the Town will work with nearby communities and other interested agencies to bring about a reduction of noise levels by private, military, public and commercial airplanes and helicopters.
Noise Impact Discussion
5.13(a) (Noise Standards, Temporary or Permanent Noise Increase) Less Than Significant Impact with Mitigation: Adoption of the 2023 – 2031 Housing Element will not result in physical development, but rather will facilitate development of housing at sites identified in the Housing Element. Construction and operation of residential land uses at sites identified in the Housing Element could result in increases in the ambient noise environment during construction and at operation. A Noise and Vibration Assessment, prepared by Illingworth and Rodkin, Inc., evaluated the potential noise impacts related to activities at all sites. The Assessment found that permanent noise increases from Project related traffic would not result in a substantial permanent increase to noise levels in the community and is less than a significant impact.
Construction
Future construction of sites identified in the Housing Element will result in temporary and intermittent noise increases in the vicinity as a result of construction activities including site preparation and grading and associated use of heavy equipment, truck traffic for material delivery, and off-haul of materials. The Assessment found that with the application of Mitigation Measure NOI-1, construction noise levels at each project site will be reduced to the extent feasible, in a less than significant impact.
5.13(b) (Groundborne Vibration and Noise) Less Than Significant Impact with Mitigation:
Though adoption of the 2023 – 2031 Housing Element will not result directly in physical development, future housing development facilitated by adoption of the Housing Element Update may result in operation of heavy construction equipment that can create ground vibration near sensitive receptors. Varying geology and distance will result in different levels of vibration, Town of Atherton
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containing different frequencies and displacements. In all cases, vibration amplitudes decrease with increasing distance.
Perceptible groundborne vibration is generally limited to areas within a few hundred feet of construction activities. Given that parcels in Atherton generally exceed one-third acre in size, construction vibration of ADUs and other smaller scale housing on existing residential properties will not result in groundborne vibration impacts to sensitive receptors. However, construction on PFS properties at a higher intensity may expose sensitive receptors to groundborne vibration. As seismic waves travel outward from a vibration source, they excite the particles of rock and soil through which they pass and cause them to oscillate. The rate or velocity (in inches per second) at which these particles move is the commonly accepted descriptor of the vibration amplitude, referred to as the peak particle velocity (PPV). Though no physical construction will occur as a result of adoption of the Housing Element, construction activities, including the type of equipment used for site-specific development is not known at this time for those parcels subject to an RM-10 and above zone change. As such, with implementation of Mitigation Measure NOI-2, short-term construction activities would not expose persons to excessive vibration levels, resulting in a less than significant impact.
5.13(c) (Airport Noise) Less Than Significant Impact: All proposed housing sites are located outside of the 55 and 60dB CNEL noise contours for both the Palo Alto Airport and San Carlos Airport. All other airports are located further away from the Town of Atherton. Thus, the project would have a less than significant impact as aircraft noise exposure would be considered compatible with proposed housing sites.
Mitigation Measure(s):
NOI-1: The following best management practices shall be implemented to reduce noise from construction activities near sensitive receptors:
Pursuant to Municipal Code, restrict noise generating activities at the construction site or in areas adjacent to the construction site to the hours between 8:00 a.m. and 5:00 p.m., Monday through Friday and prohibit construction activities on Saturday, and Sunday and State, Federal or Local Holidays.
Consider temporary noise barriers during construction phases involving earth moving equipment (e.g. grading operations) where they would be effective in reducing the construction noise impact, when directly adjoining sensitive receptors. Utilize ‘quiet’ models of air compressors and other stationary noise sources where technology exists.
Equip all internal combustion engine-driven equipment with mufflers that are in good condition and appropriate for the equipment.
Locate all stationary noise-generating equipment such as air compressors and portable power generators as far away from adjacent receptors.
Acoustically shield stationary equipment located near adjacent receptors with temporary noise barriers.
Town of Atherton
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Locate staging areas and construction material as far away as possible from adjacent receptors.
Prohibit all unnecessary idling of internal combustion engines. Route all construction traffic to and from the project site via designated truck routes and prohibit construction related heavy truck traffic in residential areas where feasible. Control noise from construction workers’ radios to the point where they are not audible at existing residences that border the project site.
Notify all adjacent receptors of the construction schedule in writing. Designate a “disturbance coordinator” who will be responsible for responding to any local complaints about construction noise. The disturbance coordinator will determine the cause of the noise complaint (e.g., starting too early, bad muffler, etc.) and will require that reasonable measures warranted to correct the problem be implemented. Conspicuously post a telephone number for the disturbance coordinator at the construction site and include it in the notice sent to neighbors regarding the construction.
NOI-2: Prior to the approval of site-specific development of housing on properties with the RM-10, RM-20 and RM-40 overlay zones and identified in the 2023 – 2031 Housing Element, groundborne vibration shall be prepared by qualified professionals in accordance with industry-accepted methodology where heavy construction activities involving significant site grading, underground, or foundation work will occur within 25 feet of residential or other vibration sensitive uses. The industry-accepted methodologies include the recommended vibration assessment procedure and thresholds provided by public agencies such as Caltrans or the Federal Highway Administration. The studies should identify necessary construction vibration controls to reduce both human annoyance and the possibility of cosmetic damage. Controls shall include, but not be limited to, the following measures:
A list of all heavy construction equipment to be used for this project known to produce high vibration levels (tracked vehicles, vibratory compaction, jackhammers, hoe rams, etc.) shall be submitted to the Town by the contractor. This list shall be used to identify equipment and activities that would potentially generate substantial vibration and to define the level of effort for reducing vibration levels below the thresholds. Place operating equipment on the construction site as far as possible from vibrationsensitive receptors. Use smaller equipment to minimize vibration levels below the limits. Avoid using vibratory rollers and tampers near sensitive areas. Select demolition methods not involving impact tools. Modify/design or identify alternative construction methods to reduce vibration levels below the limits.
Avoid dropping heavy objects or materials.
Town of Atherton
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5.14. POPULATION AND HOUSING
Would the project:
Potentially
Significant
Impact
Less Than
Significant
with
Mitigation
Less Than
Significant
Impact
No Impact
a) Induce substantial unplanned growth in
an area, either directly (for example, by
proposing new homes and businesses) or
indirectly (for example, through extension
of roads or other infrastructure)?
b) Displace substantial numbers of
existing people or housing, necessitating
the construction of replacement housing
elsewhere?
Sources: Town of Atherton General Plan 2019; Town of Atherton General Plan 2019 Update Project, Draft Initial Study/ Mitigated Negative Declaration; and California Department of Finance Population and Housing Estimates for Cities, Counties, and the State – January 1, 2022 and 2023.
Population and Housing Setting
The Town of Atherton has 2,547 housing units and a population of approximately 6,678 people.35 The 2014 Housing Element identified a need for 93 residential units to meet the Town’s Regional Housing Needs Allocation (RHNA) by 2022. The Housing Element Development Site Inventory (in the 5 th cycle) identified opportunity sites within the Town with a total development potential of approximately 240 units. As previously stated, the RHNA for the 5th Cycle Housing Element was 93 housing units comprised of 35 very low, 26 low, 29 moderate, and 3 above moderate-income units.
During the housing element’s planning period, 2015 to 2022, the Town met and exceeded the RHNA based on built and entitled housing projects.
To fulfill the 2023-2031 RHNA requirements, the 6th Cycle Housing Element must accommodate a minimum of 348 housing units, comprised of 94 very low, 54 low, 56 moderate, and 144 above moderate-income units. In addition to the 348 units allocated by the State, the Housing Element includes a 25% buffer, as recommended by HCD. The housing element projects a net of 10 additional single-family homes in the above-moderate income category will be constructed, during the 2023-2031 planning period, on vacant sites. It is projected that 48 new above moderate-income housing units will be constructed from lot splits. The property owner at 23 Oakwood is interested in potentially developing 16 housing units, in which 4 units will be under the very low to low-income category and 12 units will be under the above-moderate income category. The Town projects that 112 very low to low-income and 56 moderate-income accessory dwelling units (ADUs) will be produced during the planning period. The Housing Element Update proposes the construction of 80 new affordable multifamily housing units on private and public-school properties within the very low- to moderate-income category during the 2023-2031 planning period. To expand available 35 Department of Finance. Population and Housing Estimates for Cities, Counties, and the State – January 1, 2022 and 2023.
Estimates-E1 | Department of Finance (ca.gov)
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housing options and choice, the Project facilitates development of an additional 85 units of multifamily housing at seven properties within the R1-A zone and all properties within the POS zone.
Applicable General Plan Goals, Objectives, and Policies The Town of Atherton’s General Plan sets forth goals, objectives, and policies related to population and housing, those particularly relevant to the 2023 -2031 Housing Element Update include the following:
Land Use Element
Goal LU-1: To preserve the Town’s character as a scenic, semi-rural, thickly-wooded residential area with abundant open space.
Objective LU-1.2: To limit the nature of land uses to those which are compatible with the overall land use planning goal LU-1.
Objective LU-1.3: To retain the quality of life, character and existing in the Town’s residential neighborhoods.
Policy LU-1.1 Future plans for residential development or redevelopment are severely limited due to the fact that the Town is almost entirely developed. Policy LU-1.2 The development of high density and/or high-rise residential structures or commercial uses of any kind would destroy the scenic, semi-rural and open space character of the Town, and is, therefore, prohibited.
Policy LU-1.5 Proposed residential subdivisions as well as proposals to replace existing homes, shall adhere to the following design criteria:
Residential land uses shall be designed in accordance with the density, floor area ratio, height, bulk and other standards established by the Town. Residential land uses shall be consistent with the goals, objectives and policies of the Atherton General Plan Housing Element.
Accessory dwelling units are permitted when consistent with adopted standards. The Town allows minimum lot size subdivisions only where such minimum lot sizes do not significantly degrade established levels of privacy, wooded areas, and/or the open space environment.
Policy LU-1.7 Land uses which diminish the open space character of the Town, such as commercial and high-density residential uses, shall be prohibited.
Population and Housing Impact Discussion
5.14(a) (Substantial Growth) Less Than Significant Impact: Adoption of the 2023 – 2031 Housing Element will facilitate future housing development at identified sites that may result in an increase in population. As detailed in the General Plan, the Town is primarily built out and thus the only feasible residential developments would be smaller scale in intensity on residential properties, small portions of developed open space and school and public facilities sites. These smaller scale developments would not result in substantial unplanned population growth because the Housing Element Update plans for and anticipates said growth. Further, the update to the Town’s Housing Element will not result in indirect population growth because it does not propose the extension of Town of Atherton
2023 – 2031 Housing Element 98 Initial Study/Mitigated Negative Declaration 2474551.1 14537.003
utilities or roadways. As such, the 2023 – 2031 Housing Element will not substantially induce population growth either directly and/or indirectly and impacts will be less than significant.
5.14(b-c) (Substantial Housing or Person Displacement) Less Than Significant Impact: Sites identified in the 2023 – 2031 Housing Element are mostly developed, with few vacant sites. The housing planned for consists primarily of ADUs on existing properties zones for single-family use, vacant sites, and infill sites dispersed in the community. Therefore, adoption and implementation of the 2023 – 2031 Housing Element would not substantially displace residents or existing housing so that construction of replacement housing would be required elsewhere and resulting impacts would be less than significant.
Mitigation Measure(s): None Required.
Town of Atherton
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5.15. PUBLIC SERVICES
Would the Project:
Potentially
Significant
Impact
Less Than
Significant
with
Mitigation
Less Than
Significant
Impact
No Impact
Would the project result in substantial
adverse physical impacts associated with
the provision of new or physically altered
governmental facilities, need for new or
physically altered governmental facilities,
the construction of which could cause
significant environmental impacts, in order
to maintain acceptable service ratios,
response times or other performance
objectives for any of the public services:
a) Fire protection?
b) Police protection?
c) Schools?
d) Parks?
e) Other public facilities?
Sources: Town of Atherton General Plan 2019; Town of Atherton General Plan 2019 Update Project, Draft Initial Study/ Mitigated Negative Declaration; Atherton Resident Handbook, February 2023; Town of Atherton Fire Service Fiscal Review website; Athertonian Newsletter, Receive Resident Input and Review Fire Service Options, March 5, 2020; Sequoia Union High School District website; Menlo Park Fire Protection District Fire Unit Performance Data, 2023.
Public Services Setting
The Town of Atherton is well served by established public services including police protection, schools, and recreational amenities. Menlo Park Fire Protection District is an independent special district that provides emergency services to the Town of Atherton at Station 3. In addition to Station 3, Atherton is also served partially by Stations 1, 4, 5, and 6.
Station 3 in the Menlo Park Fire Protection District is located at 32 Almendral Avenue and the Police station is located at 80 Fair Oaks Lane. The Fire District service area covers about 30 square miles inclusive of communities in Atherton, East Palo Alto, Menlo Park, and other areas of unincorporated San Mateo County36. According to information provided on the Town of Atherton’s website, the Fire District serves approximately 7,207 residents within the Town, which represents 8% of the District’s total service population. In 2019, the Fire District had 9,347 service calls, which consisted of approximately 9-10% of service calls to Atherton residents. As detailed on the Menlo Park Fire Protection District website, Station 3 is staffed by one Captain and three firefighters. Within the 36 Town of Atherton Fire Service Fiscal Review https://www.ci.atherton.ca.us/460/Fire-Services-Fiscal-Review Town of Atherton
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Town boundaries, the Menlo Park Fire Protection District maintains three-to-ten-minute response times for all fire units, within the 90th percentile.37 Based on the Town’s website, the Atherton Police Department is staffed with one chief, one commander, two sergeants, three motor officers, one training manager and one detective. Within Town limits, the Police Department maintains an average emergency response time of approximately three minutes or less.38
According to information contained on the Town of Atherton website, the Town is served by four different districts including Las Lomitas Elementary School District, Menlo Park City School District, Redwood City School District, and Sequoia Union High School District.
The Town’s Public Works Department operates, manages, and maintains town-owned indoor and outdoor recreational facilities. Town-owned recreational facilities include opportunities for passive and active recreation and include Holbrook-Palmer Park, Town Center Park, and Menlo Circus Park.
Other recreational facilities include Las Lomitas Elementary School, Selby Lane Elementary School, Encinal Elementary School, Sacred Heart Schools, Menlo School, Menlo-Atherton High School, Laurel Elementary School, and Menlo College.
To offset the cost of improving or expanding Town services to accommodate the demand generated by new development, the Town charges one-time impact fees on new development. Impact fees are used to finance public service improvements and pay for new development's fair share of the costs necessary to maintain acceptable services. New development is also required to pay school impact fees to the local school district to assist with ongoing maintenance and expansion of facilities.
Applicable General Plan Goals, Objectives, and Policies The Town of Atherton’s General Plan sets forth goals, objectives, and policies related to public services, those particularly relevant to the 2023 -2031 Housing Element Update include the following:
Open Space and Conservation Element
Goal OSC-1: Protect both publicly and privately held open space lands from deterioration of their semi-rural charm, scenic value and environmental equilibrium.
Goal OSC-3: Minimize the impacts of flooding on health, safety and property damage. Policy OSC-3.2 The Town will assure that opportunities for green infrastructure are routinely considered by all Town departments.
Community Safety Element
Goal CS-2: Reduce the risk of injury, structure and property damage from exposure to seismic activity.
Policy CS-2.1 Support the Goals, Objectives and Policies contained in adopted Atherton local hazard mitigation plans and Emergency Operations Plans. 37 Menlo Park Fire Protection District Fire Unit Performance Data (2023) 38 Atherton Handbook https://www.ci.atherton.ca.us/DocumentCenter/View/57/Atherton-Resident--handbook--2023?bidId= Town of Atherton
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Policy CS-2.3 The Town shall seek to improve interjurisdictional cooperation with other agencies for geotechnical safety in land use planning, hazard prevention and emergency response.
Goal CS-2: Support the Town’s ability to respond effectively to natural and human-caused emergencies.
Policy CS-6.1 Support the preparation, implementation and regular update of local preparedness and evacuation plans, training and education; and multijurisdictional cooperation and communication for emergency situations. Policy CS-6.2 Continue to participate in regional emergency planning efforts.
Public Services Impact Discussion
5.15(a-b) (Fire & Police Protection) Less Than Significant Impact:
Adoption of the 2023 – 2031 Housing Element would not result in physical development of housing, but rather would facilitate future residential development at sites identified in the Housing Element which could result in impacts to fire and police protection.
Fire protection services are provided to the Town of Atherton by the Menlo Park Fire Protection District, which consists of a five-station response network that is tangential to housing sites identified in the 2023 – 2031 Housing Element. The future development of sites identified in the 2023 – 2031 Housing Element could increase the demand for fire protection services. The increase in demand for fire protection services would be offset by property taxes collected by the future developments proposed in the 2023 – 2031 Housing Element Update. In 2019, the entire MPFPD service area received 9,347 service calls and the Town represents 9-10% of the total calls. Most of the Town’s calls were related to medical emergencies which often prompted an outside ambulance service.39 Further, all future development would be reviewed by the Menlo Park Fire Protection District and be design consistent with building and fire codes, which would minimize impacts associated with fire services. Given the low demand for fire protection services and consistency with of future development with building and fire codes, impacts resulting from the implementation and adoption of the 2023 – 2031 Housing Element to fire protection services would be less than significant.
Law enforcement services within the Town of Atherton are provided by the Atherton Police Department, located at 80 Fair Oaks Lane. Sites identified in the 2023 – 2031 Housing Element are within the Police Department’s service area. The adoption and implementation of the 2023 – 2031 Housing Element could increase the demand of law enforcement services. However, the increased demand for law enforcement services would be offset by tax revenue generated from the proposed housing developments in the 2023 – 2031 Housing Element Update. Therefore, anticipated development in the 2023 – 2031 Housing Element would not increase the demand for police protection services to the extent that will require new police protection facilities.
Given that the anticipated development of the 2023 – 2031 Housing Element is required to comply with the General Plan, applicable codes and regulations, potential impacts to fire and police services resulting from adoption and implementation of the 2023 – 2031 Housing Element will be less than significant.
39 https://www.ci.atherton.ca.us/DocumentCenter/View/7543/Fire-Services-Athertonian Town of Atherton
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5.15(c-d) (Schools & Parks) Less Than Significant Impact: Adoption of the 2023 – 2031 Housing Element would not result in physical development of housing, but rather would facilitate future residential development at sites identified in the Housing Element which could result in impacts to schools and parks.
Residential development, including development facilitated by the Housing Element is required to pay school impact fees to local school districts in order to provide funding for reconstruction and facility upgrades.40 Such impact fees will compensate school districts for the increased demand of additional services and facility space generated by new residential development. Through the payment of impact fees, impacts to schools resulting from adoption and implementation of the 2023 - 2031 Housing Element would be less than significant.
The Town maintains an approximate parkland ratio of 3.44 acres per 1,000 residents.41 Pursuant to the Quimby Act, future development of sites identified in the Housing Element will be required to provide land or in lieu fees for parks. As a result, impacts to parks resulting from adoption and implementation of the Housing Element will be less than significant.
5.15(e) (Other Public Facilities) Less Than Significant Impact: It is not anticipated that adoption and implementation of the proposed Housing Element would induce a demand requiring the expansion of other public services. Existing housing in the Town of Atherton comprises low intensity residential uses which minimizes the use of public facilities. Future housing will primarily consist of development on residential properties and other infill areas in the Town of a lower intensity nature comprised primarily of ADUs, single family housing, and lower intensity attached housing. Given the minimal impact to public facilities from existing uses and lower intensity nature of proposed housing, impacts will be less than significant.
Mitigation Measure(s): None Required.
40 https://www.seq.org/DEPARTMENTS/Administrative-Services/Maintenance--Operations/School-Impact--DeveloperFees/index.html 41 https://www.ci.atherton.ca.us/DocumentCenter/View/7325/General-Plan-2019_FINAL-DRAFT Town of Atherton
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5.16. RECREATION
Would the project:
Potentially
Significant
Impact
Less Than
Significant
with
Mitigation
Less Than
Significant
Impact
No Impact
a) Would the project increase the use of
existing neighborhood and regional parks
or other recreational facilities such that
substantial physical deterioration of the
facility would occur or be accelerated?
b) Does the project include recreational
facilities or require the construction or
expansion of recreational facilities which
might have an adverse physical effect on
the environment?
Sources: Town of Atherton General Plan 2019; Town of Atherton General Plan 2019 Update Project, Draft Initial Study/ Mitigated Negative Declaration; and State of California Department of Finance Population and Housing Estimates for Cities, Counties and the State, January 1, 2022 and 2023.
Recreation Setting
Atherton provides approximately 171 acres of land dedicated to parks and open space. Areas for outdoor recreation, within the Town limits, include Holbrook-Palmer Park (22 acres), Town Center Park (0.98 acres), and Menlo Circus Club (29.25 acres). There are open spaces dedicated as outdoor recreation for public and private schools in Atherton including Encinal Elementary School, Las Lomitas Elementary School, Laurel Elementary School, Selby Lane Elementary School, MenloAtherton High School, Menlo School, Sacred Heart Schools, and Menlo College. The remaining area comprises open space along the Atherton Channel and Bear Gulch Reservoir area.
Applicable General Plan Goals, Objectives, and Policies The Town of Atherton’s General Plan sets forth goals, objectives, and policies related to recreation, those particularly relevant to the 2023 -2031 Housing Element Update include the following:
Land Use Element
Goal LU-1: To preserve the Town’s character as a scenic, semi-rural, thickly-wooded residential area with abundant open space.
Policy LU-1.6 The Town shall continue to preserve the open space characteristics of existing schools, churches, and park facilities.
Open Space and Conservation Element
Goal OSC-1: Protect both publicly and privately held open space lands from deterioration of their semi-rural charm, scenic value and environmental equilibrium.
Town of Atherton
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Objective OSC-1.1 Preserve presently existing open space, wildlife and vegetation.
Objective OSC-1.2 Prevent developmental encroachment on open space and sensitive environmental resources.
Policy OSC-1.3 Holbrook-Palmer Park shall serve as the Town’s primary outdoor recreational facility subject to the following conditions:
The property shall not be used, occupied or operated for commercial or housing purposes except those which are strictly incidental and appropriate to its use as a public recreational park.
Policy OSC-1.2 The Town seeks to preserve the open space characteristics of existing public and private schools, churches, the Menlo Circus Club, the Bear Gulch Reservoir property and the public parks.
Policy OSC-1.4 Maintain Holbrook-Palmer Park so that the Park retains its utility for community activities and events while remaining a tranquil haven for Park visitors, which balances the needs of the community.
Recreation Impact Discussion
5.16(a) (Deterioration of Parks) Less Than Significant Impact: As described in the General Plan, future residential development is limited in the Town, but there is capacity for smaller scale residential development on existing residential properties, paved developed areas of parks, and on public schools and facility sites. Low intensity residential uses in Town currently results in minimal deterioration of parks. While future development resulting from the Housing Element Update will increase use of parks, the Town of Atherton budgets for park facility maintenance and upgrades.
Further, the Town collects user fees from park site reservations for groups of more than 12 people using facilities at Holbrook-Palmer Park that minimize impacts to the park. Therefore, the deterioration of parks from housing development that would occur under the 2023-2031 Housing Element Update would be less than significant.
5.16(b) (Additional Recreational Facilities) Less Than Significant Impact: The Adoption of the 2023 – 2031 Housing Element will not directly result in the physical construction but will rather facilitate future residential development in the Town. The Holbrook-Palmer Park Master Plan, which serves to guide the use and future redevelopment of the Holbrook-Palmer Park, states, “A need for new parkland is not anticipated, as the town population is stable.” Additionally, the plan addresses that there are opportunities for continued refinement and improvements of Holbrook-Palmer Park.
With a current population of approximately 6,67842 and a parkland acreage of 22.98, the Town provides approximately 3.44 acres of park space per 1,000 residents. This meets and exceeds the State of California Parks and Recreation Department standard of 3.0 acres per 1,000 residents.
Action OSC-1.2 in the General Plan states that the “Town shall evaluate the potential for cooperative recreational use of existing school sites.” The cooperative recreational use of existing school sites would offset the need to construct or expand recreational facilities for future residential developments. The Project does not include recreational facilities or require the construction or expansion of recreational facilities which might have an adverse physical effect on the environment. 42 https://dof.ca.gov/forecasting/demographics/estimates-e1/ Town of Atherton
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As a result, the adoption and implementation of the 2023 – 2031 Housing Element will have a less than significant impact to the construction or expansion of additional recreational facilities.
Mitigation Measure(s): None Required.
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5.17. TRANSPORTATION AND CIRCULATION
Would the project:
Potentially
Significant
Impact
Less Than
Significant
with
Mitigation
Less Than
Significant
Impact
No
Impact
a) Conflict with a program, plan, ordinance or
policy addressing the circulation system,
including transit, roadway, bicycle and
pedestrian facilities?
b) Would the project conflict or be
inconsistent
with CEQA Guidelines section 15064.3,
subdivision (b)?
c) Substantially increase hazards due to a
geometric design feature (e.g., sharp curves or
dangerous intersections) or incompatible uses
(e.g., farm equipment)?
d) Result in inadequate emergency access?
Sources: Town of Atherton General Plan 2019; Town of Atherton General Plan 2019 Update Project, Draft Initial Study/ Mitigated Negative Declaration; Technical Advisory on Evaluating Transportation Impacts in CEQA, prepared by OPR, April 2018; Town of Atherton Bicycle and Pedestrian Master Plan, July 2014; San Mateo Countywide Transportation Plan 2040, prepared by City/County Association of Governments of San Mateo County, February 9, 2017; Atherton Housing Element Update Transportation Analysis, February 13, 2024; Alameda de las Pulgas Corridor Traffic Study, prepared by Advanced Mobility Group, January 25, 2019; and Town of Atherton Emergency Operations Plan, 2022.
Transportation and Circulation Setting
The Circulation Element of the General Plan regulates the city’s transportation system with the stated goal of a balanced multimodal transportation network that meets the needs of all users of streets, roads, highways, and rail for safe and convenient travel.
Level of service (LOS) has historically been used as a standard measure of traffic service. However, pursuant to SB 743 a LOS deficiency is no longer considered a potential environmental impact. The General Plan establishes a goal of maintaining LOS ‘D’ or better at minor arterials and collectors, LOS ‘E’ or better for state highways, and LOS ‘C’ for local streets (Policy CIR-5.1). Pursuant to SB 743, the Office of Planning and Research (OPR) was charged with identifying an alternative metric to LOS for evaluating environmental impacts from transportation. In April 2018 OPR released the Technical Advisory on Evaluating Transportation Impacts in CEQA, which provides technical recommendation regarding assessment of vehicle miles traveled (VMT), as an alternate to LOS, thresholds of significance for VMTs, and mitigation measures. To date, the Town of Atherton has not adopted VMT thresholds.
CEQA Guidelines section 15064.3 subdivision (b) describes specific considerations for evaluating a project’s transportation impact using a vehicle miles traveled metric. This metric refers to the amount and distance of automobile travel attributable to a project.
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Town of Atherton Bicycle and Pedestrian Master Plan
Bicycle and Pedestrian Facilities
The Atherton Bicycle and Pedestrian Master Plan, adopted on July 2014, intends to identify and advance projects that promote increased safety and non-motorized activity within the Town of Atherton. The Bicycle and Pedestrian Master Plan contributes to the region’s bicycle priorities and the local Safe Routes to School efforts. The plan provides policy and design recommendations that retain and improve the Town’s scenic character, while improving accessibility for pedestrians and bicyclists.
According to the Bicycle and Pedestrian Master Plan, Class II bike lanes located along Middlefield Road, Valparaiso Avenue, and Alameda de las Pulgas provide connectivity within the Town. However, these lanes vary in quality and need enhancements which would include wayfinding signage, green pavement markings to show conflict zones, improved detection of bikes, and the conversion of substandard bike lanes to well-designed shared roads. The plan recommends the addition of new Class II bicycle lanes along Glenwood Avenue, Selby Lane, and Atherton Avenue, which would require the widening of existing road shoulders. Within the Town, there are no Class I trails and the Plan recommends the implementation of such trails on busier streets, specifically El Camino Real, Watkins Avenue, and Marsh Road. Additionally, the Plan recommends the implementation of the San Mateo County Comprehensive Bicycle and Pedestrian Plan, which proposes two Class III bike routes within Atherton to travel to and from Redwood City and Menlo Park, which would support pedestrian conditions along school routes.
Public Transit
San Mateo County Transportation Agency (SamTrans) provides transit service for the Town through three regular bus routes El Camino Real (ECR), 296 and 397. Additionally, transit services are provided along school-designated bus routes along 72, 82, 83, 87, and 88. The SamTrans bus route ECR provides fixed route bus service with 15-minute headways during peak commute hours. The Bicycle and Pedestrian Master Plan proposes the Grand Boulevard Greenway project, which would provide transit access improvements and improve safety for all modes of travel along El Camino Real. As the Town’s only transit corridor, El Camino Real is an important corridor that provides access to schools and to downtown Menlo Park, which is one of the closest commercial areas for Town residents.
San Mateo Countywide Transportation Plan
The San Mateo Countywide Transportation Plan for 2040 is a visionary transportation plan that serves throughout San Mateo County, with visions and goals that apply to all modes of transportation. The central vision is a coordinated multimodal approach that relies on advanced technologies and management practices for the growing transportation needs of the County.
Applicable General Plan Goals, Objectives, and Policies The Town of Atherton’s General Plan sets forth goals, objectives, and policies related to transportation and circulation, those particularly relevant to the 2023 -2031 Housing Element Update include the following:
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Circulation Element
Goal CIR-1: To develop a circulation system that is compatible with the needs of various land uses planned within the Town of Atherton.
Objective CIR-1.1 To minimize the encroachment of the circulation network on the residential and open spaces uses which prevail throughout most of the community.
Objective CIR-1.2 To preserve the streets of Atherton as scenic routes. Policy CIR-1.3 Where possible within the constraints of other policies, promote the use of and implement Green Streets techniques and practices in order to reduce flooding, treat stormwater at its source, and to reduce stormwater pollution. Policy CIR-1.6 Use of Town streets as thoroughfares by trucks and other large vehicles shall be carefully controlled.
Policy CIR-1.8 Valley gutters or rolled curbs may be required in all new subdivisions. Policy CIR-1.9 All streets and highways in the Town of Atherton shall be preserved as scenic routes.
Policy CIR-1.16 The emergency evacuation routes established in this General Plan Element are El Camino Real, Middlefield Road, Marsh Road, Alameda de las Pulgas, Stockbridge Avenue, Atherton Avenue/Fair Oaks Lane, Valparaiso Avenue, Glenwood Avenue, Encinal Avenue, Watkins Avenue and Ringwood Avenue.
Goal CIR-2: To reduce congestion on freeways, state highways and principal arterials by participation with and support for the congestion management programs of C/CAG.
Goal CIR-5: To achieve a high quality of roadway operation on all Atherton streets. Policy CIR-5.1 Atherton’s minimum acceptable intersection level of service standards are listed below.
Highways: LOS E (C/CAG adopted standard)
Minor Arterials and Collectors: LOS D
Local Streets: LOS C
Policy CIR-5.2 Limit cut-through and pass through traffic on local streets by supporting Towns’ efforts using the Neighborhood Traffic Management Program described in this Element.
Policy CIR-5.4 The Town shall support identified short-term and long-term strategies and physical improvements addressing traffic concerns originating both outside and within the Town boundaries in order to improve circulation, smooth progression, improved operations, mobility and safety for all modes of transportation, as feasible. Policy CIR-5.7 The Town desires to limit public bus service to minor arterials and State Highways.
Goal CIR-6: To halt the eventual use of the Peninsula Corridor by High Speed Rail.
Objective CIR-6.2 The Town will continue to support rail efforts and services determined to be appropriate for the community, while preserving the single-family character of the Town.
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Community Safety Element
Goal CS-6: Support the Town’s ability to respond effectively to natural and human-caused emergencies.
Policy CS-6.1 Support the preparation, implementation and regular update of local preparedness and evacuation plans, training and education; and multijurisdictional cooperation and communication for emergency situations. Policy CS-6.3 The emergency evacuation routes established in this General Plan Element are El Camino Real, Middlefield Road, Marsh Road, Alameda de las Pulgas, Atherton Avenue/Fair Oaks Lane, Stockbridge Avenue, Valparaiso Avenue, Glenwood Avenue, Encinal Avenue, Watkins Avenue and Ringwood Avenue.
Transportation and Circulation Impact Discussion
5.17(a) (Conflicts with Plans, Policies, Ordinances) Less Than Significant Impact: Adoption of the 2023 – 2031 Housing Element and Zoning Code updates will not result in direct housing construction but would rather facilitate the future residential development at sites identified in the Housing Element. Future developments, under the Housing Element Update, would be subject to the Town’s guidelines, standards, and any other policies related to the circulation system. The Town adopted Bicycle and Pedestrian Master Plan establishes the Town’s vision for a more pedestrian and bicycle friendly transportation network. Additionally, this plan identifies specific projects, including new and improved bicycle facilities and pedestrian intersections along major roads within the Town.
Such improvements would provide better safety and foster the use of different modes of transportation for future additional residents. The Town is served by three SamTrans bus routes that would serve future residents. Specifically, the El Camino Real bus route would be adjacent to the proposed multifamily housing sites on Menlo School and Menlo College campuses. Because implementation of the Housing Element and Zoning Code updates would be subject to all applicable Town guidelines, standards and specifications, the proposed updates would not conflict with adopted programs, plans, ordinances, and policies that address the circulation system. Therefore, the project will result less than significant impact to transit, bicycle, and pedestrian facilities.
Level of Service – General Plan Policy CIR-5.1
The Town of Atherton’s General Plan (CIR-5.1) identifies the level of service (LOS) standard for highways as LOS E, for minor arterials and collectors as LOS D, and for local streets as LOS C. A Transportation Analysis, prepared by Hexagon Transportation Consultants, Inc. and dated February 13, 2024, analyzed traffic conditions at intersections within the Town and the potential adverse operational effects due to the Project. The study uses the Town’s intersection analysis methodology and standards in determining potential adverse operation effects due to implementation of the Housing Element update.
The analysis of signalized intersections indicated that the added project trips would not cause an adverse operational effect, as defined by the Town, at any of the signalized study intersections. The study also evaluated and provided recommendations for four unsignalized intersections:
El Camino Real and Selby Lane: The study recommends installation of a traffic signal. The Town is currently coordinating with other jurisdictions on the El Camino Real Complete Streets Gap Closure planning study which will assist in further identifying any improvements to the portion of El Camino Real from north of Selby Lane to Valparaiso Avenue.
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Bay Road and Ringwood Avenue/Sonoma Avenue: The study recommends installation of a traffic signal. This intersection is within the jurisdiction of the City of Menlo Park.
Improvements for this intersection are identified in Menlo Park’s Traffic Impact Fee (TIF) and include: conversion of the east legs of Sonoma Avenue and Ringwood Avenue to one-way couplets with Ringwood Avenue serving eastbound traffic and Sonoma Avenue serving westbound traffic; addition of left-turn lanes, as deemed necessary during the design phase, on eastbound Ringwood Avenue and northbound Bay Road; and installation of a traffic signal. With the addition of the traffic signal, the intersection would be expected to operate at an acceptable LOS A during the AM peak hour.
Alameda de las Pulgas and Atherton Avenue: The study recommends evaluation of the potential installation of a single-lane roundabout. Pursuant to the Alameda de las Pulgas Corridor Traffic Study, prepared by Advanced Mobility Group and dated January 25, 2019, the Town of Atherton is currently analyzing the feasibility of a roundabout or signal at this intersection.
El Camino Real and Alejandra Avenue: The study found that in all scenarios (including existing and project) long delays equivalent to LOS E are present. Signalization of this intersection is not recommended. Menlo College is located at the southwest and southeast corners of this intersection. As a private school located within the Public Facilities and School District (PFS) zone, the school must submit a master plan for review by the Planning Commission on an annual basis. This review includes evaluation of the school’s operational compliance with General Plan Policy CIR-5.3 to address traffic congestion and flow issues to assure that impacts on the circulation system are not excessive.
The analysis of unsignalized intersections indicates that the recommended improvements are consistent with current transportation improvements under analysis by the Town and surrounding jurisdictions. Therefore, the project does not conflict with General Plan Policy CIR-5.1.
5.17(b) (Conflict with 15064.3(b) VMT) Less Than Significant Impact with Mitigation: In accordance with Senate Bill (SB) 743, an analysis of potential impacts on VMT resulting from new housing was conducted as part of the environmental analysis. The Town of Atherton has not formally adopted a VMT policy, therefore, the VMT thresholds for this project were based on the Governor’s Office of Planning and Research (OPR)’s recommendations. Consistent with OPR guidelines, 85 percent of the existing regional average daily VMT per resident was assumed as the VMT threshold of significance. Average VMT per resident for the project parcels was reported from the City/County Association of Governments (C/CAG) of San Mateo County VMT Estimation Tool, and the project average VMT per resident was compared to the Bay Area regional average.
The Transportation Analysis evaluated VMT impacts of the proposed accessory dwelling units (ADUs), SB 9 units, vacant sites, and multifamily housing sites under the Housing Element Update that would be spread throughout the Town. Pursuant to the OPR’s VMT guidelines, most of the proposed housing sites would be considered individually “small” projects, projects located in areas near transit or areas of existing low VMT. “Small” projects are characterized as generating less than 110 trips per day, this designation applies to ADUs, SB 9 units, vacant sites, 23 Oakwood Boulevard, 150 Valparaiso Avenue (Sacred Heart), the Gilmore House site, Circus Club and the Cal Water site.
Proposed multifamily housing sites at 1000 El Camino Real (Menlo College) and 50 Valparaiso (Menlo School) would be adjacent to El Camino Real, which serves as a high-quality transit corridor with SamTrans bus route ECR that has a fixed route bus service with 15-minute headways during peak Town of Atherton
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commute hours. Proposed multifamily sites located in areas of Low VMT include the properties at 175, 185, and 197 Ravenswood Avenue. Low VMT areas have a VMT per resident less than the Bay Area regional threshold of 12.4 daily VMT per resident. Pursuant to the OPR’s VMT guidelines, “small” projects and projects located in areas near transit or areas of existing low VMT are assumed to have a less than significant VMT impact.
Projects proposed at 999 Ringwood Avenue, 352, 318, and 296 Bay Road are located in an area where the existing VMT is 13.0 daily VMT per resident, which is above the established threshold of
12.4 daily VMT per resident and is referred to as being in a “high-VMT area”. Projects in high-VMT areas are required to include a set of VMT reduction measures that would reduce the project VMT to the greatest extent possible. The C/CAG VMT Estimation Tool evaluates a list of selected VMT reduction measures that can be applied to a project to reduce the project VMT. There are four strategy tiers whose effects on VMT can be calculated with the VMT estimation tool:
Tier 1: Project characteristics (e.g. density, diversity of uses, design, and affordability of housing) that encourage walking, biking and transit uses.
Tier 2: Multimodal infrastructure improvements that increase accessibility for transit users, bicyclists, and pedestrians. These improvements include:
Increase bike access,
Improve connectivity by increasing intersection density, Increase transit accessibility,
Traffic calming measures beyond the project frontage, Pedestrian network improvements beyond the project frontage.
Tier 3: Parking measures that discourage personal motorized vehicle-trips. These improvements include:
Limit parking supply,
Provide bike facilities.
Tier 4: Transportation demand management (TDM) measures that provide incentives and services to encourage alternatives to personal motorized vehicle-trips. These measures for residential developments include:
School pool program,
Bike share programs,
Car share programs,
Subsidized transit program,
Unbundle parking costs from property costs,
Voluntary travel behavior change program.
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The first three strategies are physical design strategies that can be incorporated into the project design. TDM includes programmatic measures that aim to reduce VMT by decreasing personal motorized vehicle mode share and by encouraging more walking, biking, and riding transit. To avoid potential impacts, future development on these subject parcels shall comply with Mitigation Measure TRAN-1 to implement Tier 1-4 strategies to reduce potential VMT impacts to less than significant.
5.17(c) (Geometric Design Feature Hazard) Less Than Significant Impact: Adoption of the 2023 – 2031 Housing Element and Zoning Code updates will not result in physical construction, but rather will facilitate future development of housing opportunity sites identified in the Housing Element.
Future residential development, including the development of bicycle infrastructure, transit infrastructure, and pedestrian infrastructure would be subject to the design requirements of the Town’s General Plan and other design standards. The sites identified in the Housing Element Update are located in an urban environment and therefore future development on these sites would not be incompatible with surrounding uses. As such, impacts related to transportation hazards would be less than significant.
5.17(d) (Emergency Access) Less Than Significant Impact: Adoption of the 2023 – 2031 Housing Element and Zoning Code updates will not result in physical construction, but rather will facilitate future development of housing opportunity sites identified in the Housing Element that may increase vehicular traffic and thus may impact emergency access. Future development of housing opportunity sites identified in the Housing Element will be subject to review by the Town of Atherton Public Works Department and the Menlo Park Fire Protection District, who will identify potential deficiencies in emergency access and provide recommendations to ensure emergency access is adequate and complies with applicable regulations. Additionally, the Town maintains an Emergency Operations Plan that serves as a foundation for emergency management. This plan focuses on four phases of emergency management which includes preparedness, response, recovery, and mitigation. Compliance with applicable regulations and the implementation of the Town’s Emergency Operations Plan will ensure future development of sites identified in the Housing Element Update provide adequate emergency vehicle access during construction and at operation.
As a result, impacts to emergency access will be less than significant.
Mitigation Measure(s):
TRAN-1: Submittals of site-specific development proposals for housing sites identified in the 2023 – 2031 Housing Element that are located in an high-VMT area shall include a VMT analysis that identifies travel demand management (TDM) measures and/or physical measures (i.e. Tier 1 through Tier 4 strategies) to reduce VMT impacts to less than significant. Additional measures may be proposed by individual projects and/or required by Town staff to achieve the necessary VMT reductions or to meet applicable TDM reduction requirements. programs.
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5.18. TRIBAL CULTURAL RESOURCES
Would the project:
Potentially
Significant
Impact
Less Than
Significant
with
Mitigation
Less Than
Significant
Impact
No Impact
a) Would the project cause a substantial
adverse change in the significance of a
tribal cultural resource, defined in Public
Resources Code section 21074 as either a
site, feature, place, cultural landscape that
is geographically defined in terms of the
size and scope of the landscape, sacred
place, or object with cultural value to a
California Native American tribe, and that
is:
i. Listed or eligible for listing in the
California Register of Historical
Resources, or in a local register of
historical resources as defined in Public
Resources Code section 5020.1(k), or
ii. A resource determined by the lead
agency, in its discretion and supported
by substantial evidence, to be
significant pursuant to criteria set forth
in subdivision (c) of Public Resources
Code Section 5024.1. In applying the
criteria set forth in subdivision (c) of
Public Resource Code Section 5024.1,
the lead agency shall consider the
significance of the resource to a
California Native American tribe.
Sources: Town of Atherton General Plan 2019; Town of Atherton General Plan 2019 Update Project, Draft Initial Study/ Mitigated Negative Declaration.
Tribal Cultural Resources Setting
Public Resources Code (PRC) Section 21074, identifies tribal cultural resources as:
4. Sites, features, places, cultural landscapes, sacred places, and objects with cultural value to a California Native American tribe that are either of the following:
a. Included or determined to be eligible for inclusion in the California Register of Historical Resources; or
b. Included in a local register of historical resources as defined in PRC Section 5020.1(k).
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5. A resource determined by the lead agency, in its discretion and supported by substantial evidence, to be significant pursuant to criteria set forth in PRC Section 5024.1(c). In applying the criteria set forth in PRC Section 5024.1(c), the lead agency shall consider the significance of the resource to a California Native American tribe.
6. A cultural landscape that meets the criteria of PRC Section 21074(a) to the extent that the landscape is geographically defined in terms of the size and scope of the landscape.
7. A historical resource described in PRC Section 21084.1, a unique archaeological resource as defined in PRC Section 21083.2(g), or a “non-unique archaeological resource” as defined in PRC Section 21083.2(h), if it conforms with the criteria of PRC Section 21074(a).
In accordance with Public Resources Code (PRC) Section 21084.2, lead agencies are required to consider Tribal Cultural Resources (TCR) including a site feature, place, cultural landscape, sacred place, or object, of cultural value to the tribe and is listed on the California Register of Historic Resources (CRHR) or a local register, or the Lead agency, at its discretion, chooses to treat resources as such. Assembly Bill 52 and Senate Bill (SB) 18 require lead agencies to contact and consult with California Native American tribes prior to amending and adopting a general plan. In accordance with AB 52 and SB 18, The Town of Atherton carried out notification to the Amah Mutsun Tribal Band of Mission San Juan Bautista, Costanoan Rumsen Carmel Tribe, Indian Canyon Mutsun Band of Coastanoan, the Ohlone Indian Tribe, Wuksachi Indian Tribe/Eshom Valley Band, and the Tamien Nation.
Applicable General Plan Goals, Objectives, and Policies The Town of Atherton’s General Plan sets forth goals, objectives, and policies related to tribal cultural resources, those particularly relevant to the 2023 -2031 Housing Element Update include the following:
Open Space and Conservation Element
Goal OSC-1: Protect both publicly and privately held open space lands from deterioration of their semi-rural charm, scenic value and environmental equilibrium. Policy OSC-1.1 The Town shall endeavor to protect scenic resources, significant stands of natural vegetation, wildlife habitat, public safety and significant archaeological resources, both publicly and privately held.
Goal OSC-4: Protect both publicly and privately held cultural resources from deterioration and/or destruction.
Policy OSC-4.1 Encourage the preservation of both private and public historical resources and artifacts for the benefit of future generations. Policy OSC-4.2 The Town will comply with minimum State requirements in the event archaeological or paleontological resources are discovered during construction.
Tribal Cultural Resources Impact Discussion
5.18(a.i - ii) (Listed or Eligible for Listing; Significant Resource) Less Than Significant Impact with Mitigation: Adoption of the proposed Housing Element Update will facilitate future development of undeveloped, developed, and infill housing opportunity sites identified in the Housing Element Update. The Town of Atherton carried out notification to the Amah Mutsun Tribal Town of Atherton
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Band of Mission San Juan Bautista, Costanoan Rumsen Carmel Tribe, Indian Canyon Mutsun Band of Coastanoan, the Ohlone Indian Tribe, Wuksachi Indian Tribe/Eshom Valley Band, and the Tamien Nation in accordance with AB 52 and SB 18. None of the tribes requested consultation during the notification period. During the future development of sites identified in the Housing Element Update, there is a potential that unrecorded resources may be encountered during grounddisturbing activities including potentially significant tribal cultural resources. With implementation of Mitigation Measure TCUL-1, which requires compliance with minimum State requirements for the discovery of paleontological and archaeological resources, impacts due to a change in the significance of tribal cultural resources will be reduced to less than significant.
Mitigation Measure(s):
TCUL-1: Implement Mitigation Measure CUL-2.
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5.19. UTILITIES AND SERVICE SYSTEMS
Would the project:
Potentially
Significant
Impact
Less Than
Significant
with
Mitigation
Less Than
Significant
Impact
No Impact
a) Require or result in the relocation or
construction of new or expanded water, or
wastewater treatment, or storm water
drainage, electric power, natural gas, or
telecommunication facilities, the
construction or relocation of which could
cause significant environmental effects?
b) Have sufficient water supplies available to
serve the project and reasonably
foreseeable future development during
normal, dry and multiple dry years?
c) Result in a determination by the
wastewater treatment provider which
serves or may serve the project that it has
adequate capacity to serve the project’s
projected demand in addition to the
provider’s existing commitments?
d) Generate solid waste in excess of State or
local standards, or in excess of the capacity
of local infrastructure, or otherwise impair
the attainment of solid waste reduction
goals?
e) Comply with federal, state, and local
management and reduction statutes and
regulations related to solid waste?
Sources: Town of Atherton General Plan 2019; Town of Atherton General Plan 2019 Update Project, Draft Initial Study/ Mitigated Negative Declaration; 2020 Urban Water Management Plan: Bear Gulch District, June 2021; Green Infrastructure Plan, September 18, 2019; GreenWaste Recovery, Inc. website; Franchise Agreement Between the Town of Atherton and GreenWaste Recovery, Inc., November 19, 2020.
Utilities and Service Systems Setting
Sites identified in the Housing Element are located within the Town of Atherton on existing developed land connected to or adjacent to existing utility infrastructure.43 Water supply derives from the City and County of San Francisco Hetch Hetchy System and is distributed by the California Water Service Company. Wastewater is collected by the West Bay Sanitary District and the Fair Oaks Sanitary District. The wastewater is conveyed for treatment to the Silicon Valley Clean Water (SVCW) 43 Atherton Housing Element
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Wastewater Treatment Plant (WWTP). The Town of Atherton, in addition to the Atherton Channel Drainage District and the San Mateo County Flood Control District, is responsible for the management of stormwater drainage. Solid waste services are provided by GreenWaste, Inc. that hauls the waste to GreenWaste Material Recovery Facility, and electrical and natural gas are provided by Pacific Gas and Electric (PG&E).
Potable Water Supplies
The Town acquires potable water from the Bear Gulch District of the California Water Service. The water supply is purchased or imported from the San Francisco Public Utilities Commission (93%) and some supply is provided by the Bear Gulch Reservoir (7%).44 Currently, a recycled water system for beneficial use within the Bear Gulch District is not planned. Due to low demand and high unit cost, recycled water supply is not being urgently pursued. The 2020 Urban Water Management Plan for the Bear Gulch District projects waters use through 2045 and is estimated based on population, housing, and employment projections development by the Association of Bay Area Government (ABAG). The planned water capacity is sufficient to accommodate the Town’s RHNA that projects population and housing through 2031. In addition, the Town anticipates that the new developments proposed will have greater efficiency of water use, due to the subdivision of properties through SB 9 and the development of ADUs.14 Per the Housing Element Update, Cal Water’s Management Plan indicates that the use of potable water is projected to decrease for single-family residences due to appliance efficiency standards, plumbing codes, and conservation programs.
Wastewater and Recycled Water
Wastewater generated in the Town of Atherton is collected by the West Bay Sanitary District and the Fair Oaks Sanitary District to facilities operated by Silicon Valley Clean Water (SVCW). The water is conveyed for processing at the treatment facilities located in Redwood City and operated by SVCW.
The SVCW wastewater treatment plant (WWTP) has a treatment capacity of 29.5 million gallons per day (MGD). The WWTP undergoes primary, secondary (activated sludge), filtration, disinfection, and dichlorination treatment before it reaches the outfall pipe to the San Francisco Bay. Within the current SVCW service area, the WWTP receives approximately 20.0 MGD. In 2020, SVCW collected 1,345 acre-feet of wastewater from the Town of Atherton. SVCW currently provides recycled water to areas located in and owned by Redwood City and Menlo Park.45 Storm Drainage
Within the Town of Atherton, storm drains convey runoff form impervious surfaces such as streets, sidewalks, and buildings to street channels that drain to the Atherton Channel and ultimately to the San Francisco Bay.46 This water is untreated and can carry contaminants such as solvents, oils, fuels, and sediment. In Chapter 8.50 of the Town’s Municipal Code, there are regulations and standard requirements on the storm drain system, which all existing and proposed development shall comply with.
44 Atherton Housing Element
45 Bear Gulch 2020 UWMP https://www.calwater.com/docs/uwmp2020/BG_2020_UWMP_FINAL.pdf 46 Atherton Green Infrastructure Plan https://www.ci.atherton.ca.us/DocumentCenter/View/6813/Green-Infrasturcture-Plan Town of Atherton
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Solid Waste
Solid waste (debris, construction waste, recyclable materials, and green waste/compost) generated in the Town of Atherton is collected by GreenWaste, Inc. and delivered to the GreenWaste Material Recovery Facility. The GreenWaste Material Recovery Facility serves to sort and process solid waste and recyclables. There are three separate processing facilities for different types of materials including a recyclables facility, Municipal Solid Waste facility, and a Yard Trimmings facility.47 Applicable General Plan Goals, Objectives, and Policies The Town of Atherton’s General Plan sets forth goals, objectives, and policies related to utilities and service systems, those particularly relevant to the 2023 -2031 Housing Element Update include the following:
Land Use Element
Goal LU-1: To preserve the Town’s character as a scenic, semi-rural, thickly-wooded residential area with abundant open space.
Objective LU-1.3 To retain the quality of life, character and existing in the Town’s residential neighborhoods.
Policy LU-1.5 Proposed residential subdivisions as well as proposals to replace existing homes, shall adhere to the following design criteria:
Adequate drainage and off-street parking shall be provided. Street lighting shall be kept to a minimum. Temporary or guest on-street parking areas shall be minimized. All utilities installed in conjunction with new subdivisions shall be placed underground.
Policy LU-1.9 Identify and implement green infrastructure opportunities for stormwater management including those recognized in the Town’s Green Infrastructure Plan. Green infrastructure facilities should reflect the Town’s visual semi-rural character.
Circulation Element
Goal CIR-1: To develop a circulation system that is compatible with the needs of various land uses planned within the Town of Atherton.
Policy CIR-1.3 Where possible within the constraints of other policies, promote the use of and implement Green Streets techniques and practices in order to reduce flooding, treat stormwater at its source, and to reduce stormwater pollution. Policy CIR-1.8 Valley gutters or rolled curbs may be required in all new subdivisions.
Open Space and Conservation Element
Goal OSC-3: Minimize the impacts of flooding on health, safety and property damage. Policy OSC-3.1 New development shall provide detention volume to attenuate any increase in stormwater runoff caused by increased imperviousness created by the proposed development.
47 https://www.greenwaste.com/about-us/processing-facility/ Town of Atherton
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Policy OSC-3.2 The Town will assure that opportunities for green infrastructure are routinely considered by all Town departments.
Goal OSC-5: Implement the GHG programs in the Atherton Climate Action Plan related to energy efficiency, community waste generation, and reduced water consumption.
Community Safety Element
Goal CS-4: Support any Town Green Infrastructure programs that address stormwater infrastructure that may use natural processes to manage water and create healthier urban environments.
Utilities and Service Systems Impact Discussion
5.19(a) (Relocation/Expansion of Utilities) Less Than Significant Impact: Housing Opportunity sites identified in the 2023 – 2031 Housing Element are currently well served by water, wastewater, electricity, natural gas, and telecommunication facilities. Future development under the Housing Element will increase utility demands relative to existing conditions. As previously discussed, the number of units and resulting population are within the available capacity of utilities and service systems. New residential uses facilitated by adoption of the Housing Element will connect to existing utility lines in adjacent rights-of-way and will install new utility pipelines, connections, laterals, and associated equipment onsite and offsite including potable and recycled water pipelines, sanitary sewer and storm drain infrastructure. New electric power, natural gas, and telecommunication lines will be connected to existing facilities in the immediate vicinity of sites identified in the Housing Element.
Population projections guiding the operational capacity are provided in the 2020 Urban Water Management Plan (UWMP) for the Bear Gulch District. These projections extend through 2045 and are based on population growth metrics provided by ABAG. The SVCW WWTP has sufficient wastewater treatment capacity to accommodate current and projected demand from the 2023-2031 Housing Element planning period, as the Project is within the time frame planned for by the UWMP.
Therefore, there is sufficient wastewater treatment capacity to accommodate development of residential uses under the 2023 – 2031 Housing Element and adoption of the Housing Element will not cause or exceed wastewater treatment requirements set forth by the Regional Water Quality Control Board, nor is it expected to necessitate the expansion or construction of water or wastewater treatment facilities. Therefore, implementation of the Housing Element will have a less than significant impact related to the adequacy or capacity of stormwater facilities.
5.19(b) (Sufficient Water Supplies) Less Than Significant Impact: During future construction of sites identified in the Housing Element, water will be required primarily for dust suppression and soil compaction. Construction water volumes will be minimal and will not require new or expanded water supplies or entitlements.
At operation future housing development identified in the 2023 – 2031 Housing Element will generate water demand for indoor and outdoor uses and will rely on potable water supplies to meet demands. Future development of sites identified in the Housing Element will increase water demand relative to existing conditions. As described above, demand projections included in the 2020 UWMP Bear Gulch District will adequately supply the Project. However, consumption of the Bear Gulch’s water supply is also projected to decrease between 2025 – 2045, this decrease is attributed due to ongoing changes in appliance standards and plumbing codes, conservation and customer assistance programs, and inflation-adjusted costs. Such factors are anticipated to attenuate the increase in Town of Atherton
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water use associated with the increase in population. As such, impacts to water supplies as a result of adoption and implementation of the Housing Element will be less than significant.
5.19(c) (Sufficient Wastewater Treatment) Less Than Significant Impact: Future construction facilitated by adoption of the 2023 – 2031 Housing Element will generate wastewater. As described above in 5.19(a), wastewater generated by future development at sites identified in the Housing Element will be conveyed to the Silicon Valley Clean Water (SVCW) treatment facilities, which has sufficient operating capacity to process effluent generated by residential developments at these sites. As such, adoption and implementation of the 2023 – 2031 Housing Element will not require or result in the construction or expansion of new wastewater treatment facilities. Therefore, impacts to the wastewater treatment system will be less than significant.
5.19 (d, e) (Solid Waste Generation/Compliance with Solid Waste Management) Less Than Significant Impact: Future construction facilitated by adoption of the 2023 – 2031 Housing Element will generate solid waste. Consistent with Cal Green Mandatory Measures, and as a standard requirement for building permits, at least 65% of nonhazardous construction and demolition waste will be required to be recycled or salvaged and preparation of a Construction Waste Management Plan that documents the diversion of materials as required by CALGreen will also be required.
Accordingly, impacts associated with construction waste will be less than significant.
Future operation of residential uses at sites identified in the Housing Element will generate solid waste including debris, recyclables, and compostables. The Town is under contract with GreenWaste Recovery, Inc. for hauling, sorting, and disposal of waste. Solid waste is collected and processed to ensure that materials that are marketable or recoverable are not transported to the landfill and that the Town receives credit for the state diversion mandates.48 All residues after processing are transported to the landfill. GreenWaste ensures that Recyclable Materials, Mixed Compostable Materials, and Yard Trimmings are diverted from landfills to the maximum extent practicable with recovery rates ranging from 75% to 98%. Although the waste stream generated by operation of residential uses at sites identified in the Housing Element will increase during construction and operation, it is not expected to exceed landfill capacity and is not expected to result in violations of federal, state, and local statutes and regulations related to solid waste. Therefore, disposal of solid waste resulting from construction and operation of sites identified in the 2023 – 2031 Housing Element will be less than significant.
Mitigation Measure(s): None required.
48 https://www.ci.atherton.ca.us/DocumentCenter/View/11046/FINAL_Atherton-GWR-Agreement-and-Exhibits-111920?bidId= Town of Atherton
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5.20. WILDFIRE
Would the project:
Potentially
Significant
Impact
Less Than
Significant
with
Mitigation
Less than
Significant
Impact
No
Impact
If located in or near state responsibility areas
or lands classified as very high fire hazard
severity zones, would the project:
a) Substantially impair an adopted
emergency response plan or emergency
evacuation plan?
b) Due to slope, prevailing winds, and other
factors, exacerbate wildfire risks, and
thereby expose project occupants to
pollutant concentrations from a wildfire
or the uncontrolled spread of a wildfire?
c) Require the installation or maintenance
of associated infrastructure (such as
roads, fuel breaks, emergency water
sources, power lines or other utilities)
that may exacerbate fire risk or that may
result in temporary or ongoing impacts
to the environment?
d) Expose people or structures to significant
risks, including downslope or
downstream flooding or landslides, as a
result of runoff, post-fire slope instability,
or drainage changes?
Sources: Town of Atherton General Plan 2019; Town of Atherton General Plan 2019 Update Project, Draft Initial Study/ Mitigated Negative Declaration; Wildland Urban Interface Fire Threatened Communities Map, produced by CalFire, 2003; San Mateo County Very High Fire Hazard Severity Zones in Local Responsibility Area map, produced by CalFire, November 28, 2008; Menlo Park Fire Protection District Staff Report, 2011; MTC/ABAG Hazard Viewer Map; and Menlo Park Fire Protection District Ordinance No. 48-2022 District Fire Prevention Code.
Wildfire Setting
According to the General Plan, wildland fires pose a hazard within the Town of Atherton. The entire Town has been categorized as a “Community at Risk” by the California Department of Forestry and Fire Protection (CAL FIRE).49 The Walsh Road neighborhood is the most seriously threatened neighborhood within the Town limits and is limited to one primary evacuation route.50 This neighborhood is in an area with steeper slopes compared to the rest of the Town. As shown in 49 firethreat_wui.pdf (smcgov.org)
50 Town of Atherton General Plan
Town of Atherton
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Figure 5, the Town of Atherton is designated as a Non-Very High Fire Hazard Severity Zone (NonVHFHSZ) within the Local Responsibility Area (LRA) by CAL FIRE.51
FIGURE 5: CAL FIRE SAN MATEO COUNTY VERY HIGH FIRE HAZARD SEVERITY ZONES (LOCAL RESPONSIBILITY AREA) 51 https://osfm.fire.ca.gov/media/6800/fhszl_map41.pdf
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Applicable General Plan Goals, Objectives, and Policies The Town of Atherton’s General Plan sets forth goals, objectives, and policies related to wildfire, those particularly relevant to the 2023 -2031 Housing Element Update include the following:
Land Use Element
Goal LU-1: To preserve the Town’s character as a scenic, semi-rural, thickly-wooded residential area with abundant open space.
Policy LU-1.3 Minimum new lot sizes in hillside areas (defined as areas with average cross slopes greater than 20 percent) shall be related to the slope and shall not be less than:
0 – 19% cross slope is a minimum lot size of 1 acre
20 – 34.9% average cross slope is a minimum lot size of 2 acres 35% + average cross slope is a minimum lot size of 5 acres Policy LU-1.5 Proposed residential subdivisions as well as proposals to replace existing homes, shall adhere to the following design criteria:
Adequate drainage and off-street parking shall be provided. Street lighting shall be kept to a minimum. Temporary or guest on-street parking areas shall be minimized. Policy LU-9 Identify and implement green infrastructure opportunities for stormwater management including those recognized in the Town’s Green Infrastructure Plan. Green infrastructure facilities should reflect the Town’s visual semi-rural character.
Circulation Element
Goal CIR-1: To develop a circulation system that is compatible with the needs of various land uses planned within the Town of Atherton.
Objective CIR-1.1 To minimize the encroachment of the circulation network on the residential and open spaces uses which prevail throughout most of the community. Policy CIR-1.16 The emergency evacuation routes established in this General Plan Element are El Camino Real, Middlefield Road, Marsh Road, Alameda de las Pulgas, Stockbridge Avenue, Atherton Avenue/Fair Oaks Lane, Valparaiso Avenue, Glenwood Avenue, Encinal Avenue, Watkins Avenue and Ringwood Avenue. Policy CIR-1.3 Where possible within the constraints of other policies, promote the use of and implement Green Streets techniques and practices in order to reduce flooding, treat stormwater at its source, and to reduce stormwater pollution.
Goal CIR-7: Support the goals, policies and programs embodied in the adopted Atherton Climate Action Plan.
Open Space and Conversation Element
Goal OSC-1: Protect both publicly and privately held open space lands from deterioration of their semi-rural charm, scenic value and environmental equilibrium.
Objective OSC-1.2 Prevent developmental encroachment on open space and sensitive environmental resources.
Objective OSC-1.3 Endeavor to prevent soil erosion and the potential loss of topsoil through the development review process.
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Policy OSC-1.1 The Town shall endeavor to protect scenic resources, significant stands of natural vegetation, wildlife habitat, public safety and significant archaeological resources, both publicly and privately held.
Goal OSC-3: Minimize the impacts of flooding on health, safety and property damage. Policy OSC-3.1 New development shall provide detention volume to attenuate any increase in stormwater runoff caused by increased imperviousness created by the proposed development.
Policy OSC-3.2 The Town will assure that opportunities for green infrastructure are routinely considered by all Town departments.
Community Safety Element
Goal CS-1: The Town recognizes the potential danger to public safety that may result from natural or man-made causes and seeks to minimize the public risks in such hazards.
Goal CS-2: Reduce the risk of injury, structure and property damage from exposure to seismic activity.
Policy CS-2.1 Support the Goals, Objectives and Policies contained in adopted Atherton local hazard mitigation plans and Emergency Operations Plans. Policy CS-2.2 Public education, research and information dissemination on seismic hazards and emergency response shall be encouraged.
Policy CS-2.3 The Town shall seek to improve interjurisdictional cooperation with other agencies for geotechnical safety in land use planning, hazard prevention and emergency response.
Goal CS-4: Support any Town Green Infrastructure programs that address stormwater infrastructure that may use natural processes to manage water and create healthier urban environments.
Goal CS-5: Prevent and reduce risks to property and protect residents from urban and wildland fire hazards.
Goal CS-6: Support the Town’s ability to respond effectively to natural and human-caused emergencies.
Policy CS-6.1 Support the preparation, implementation and regular update of local preparedness and evacuation plans, training and education; and multijurisdictional cooperation and communication for emergency situations. Policy CS-6.2 Continue to participate in regional emergency planning efforts. Policy CS-6.3 The emergency evacuation routes established in this General Plan Element are El Camino Real, Middlefield Road, Marsh Road, Alameda de las Pulgas, Atherton Avenue/Fair Oaks Lane, Stockbridge Avenue, Valparaiso Avenue, Glenwood Avenue, Encinal Avenue, Watkins Avenue and Ringwood Avenue.
5.20(a) (Impair Emergency Plans) Less Than Significant Impact: Adoption of the 2023 – 2031 Housing Element will not result in physical development, but rather will facilitate future development of housing sites identified in the 2023 – 2031 Housing Element, all of which are within incorporated Town limits. The Town of Atherton is supported by a total of six Menlo Park Fire Protection District stations, which allows for short response times. Furthermore, site-specific designs Town of Atherton
2023 – 2031 Housing Element 125 Initial Study/Mitigated Negative Declaration 2474551.1 14537.003
will be reviewed by the Menlo Park Fire Protection District to ensure safe and efficient ingress and egress for emergency vehicles is provided. All sites are adjacent to emergency evacuation routes established in the General Plan. Further, all identified sites in the 2023 – 2031 are spread throughout the Town and are not concentrated in one area. Such dispersion would minimize impairment on the ingress and egress of emergency vehicles. Additionally, the Menlo Park Fire Protection District has established primary emergency response routes within Town limits to ensure rapid deployment of emergency resources and maintain quick response times.52 Further, any future development would be evaluated for consistency with General Plan goals, objectives, and policies that ensure emergency response plans will not be impaired. For these reasons, future housing developments facilitated by the 2023 – 2031 Housing Element are not expected to substantially impair an adopted emergency response plan or emergency evacuation plan, and impacts will be less than significant.
57.20(b-d) (Wildfire Risk Exacerbation, Infrastructure Contributing to Wildfire Risk, Exposure to Wildfire-Related Risks) Less Than Significant Impact: Housing sites identified for future development in the Housing Element are located outside of very high wildfire risk, according to CALFIRE.53 Most of the identified housing sites are relatively level and are not subject to risks associated with flooding, landslides or slope instability.54 Housing sites located west of Alameda de las Pulgas, adjacent to the Bear Gulch Reservoir, would be subject to greater slopes and adjacent to the Walsh Road neighborhood; thus, such housing sites would have a greater wildfire risk than other areas of the Town. To offset potential wildfire risks within this area, all future developments on sites identified in the 2023 – 2031 Housing Element must comply with the MPFPD Fire Prevention Code and the CBC, which contains standards for building materials, systems, and assemblies used in the exterior design and construction of new buildings. Additionally, the Town has established an evacuation plan that provides emergency response information and coordination for first responders and contributing agencies. According to the Housing Element, there is adequate water supply infrastructure for fire suppression purposes that would accommodate planned density of development. The Town area is susceptible to gusty winds during the summer; however, the local requirements of the MPFPD and the enforced Fire Code would reduce a fire’s ability to spread, when experiencing such wind patterns.55 Therefore, there are no factors, such as steep slopes, prevailing winds, or the installation/maintenance of new infrastructure, that would exacerbate fire risk, result in temporary or ongoing impacts to the environment, or expose occupants of future residential developments to the uncontrolled spread of a wildfire, post-fire slope instability, post-fire flooding, or pollutant concentrations from a wildfire. Therefore, the 2023 – 2031 Housing Element Update impacts will be less than significant.
Mitigation Measure(s): None Required.
52 Menlo Park Fire Protection District Primary Response Routes Staff Report 53 https://osfm.fire.ca.gov/media/6800/fhszl_map41.pdf
54 https://mtc.maps.arcgis.com/apps/webappviewer/index.html?id=4a6f3f1259df42eab29b35dfcd086fc8 55https://www.menlofire.gov/media/News/2022/October/Town%20of%20Atherton%20Fire%20Code%20Ordinance%202022% 20FINAL.pdf
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5.21. MANDATORY FINDINGS OF SIGNIFICANCE (CAL. PUB. RES. CODE §15065) A focused or full environmental impact report for a project may be required where the project has a significant effect on the environment in any of the following conditions:
Would the project:
Potentially
Significant
Impact
Less Than
Significant
with
Mitigation
Less Than
Significant
Impact
No Impact
a) Does the project have the
potential to substantially degrade
the quality of the environment,
substantially reduce the habitat of a
fish or wildlife species, cause a fish or
wildlife population to drop below
self-sustaining levels, threaten to
eliminate a plant or animal
community, substantially reduce the
number or restrict the range of a
rare or endangered plant or animal
or eliminate important examples of
the major periods of California
history or prehistory?
b) Does the project have impacts that
are individually limited, but
cumulatively considerable?
(“Cumulatively considerable” means
that the incremental effects of a
project are considerable when
viewed in connection with the effects
of past projects, the effects of other
current projects, and the effects of
probable future projects)?
c) Does the project have
environmental effects, which will
cause substantial adverse effects on
human beings, either directly or
indirectly?
Mandatory Findings Discussion
5.21(a) (Degrade the Environment): Less Than Significant Impact: The proposed Housing Element and Zoning Code updates are consistent with the General Plan, goals, policies and programs of the Town. As a policy document, the Housing Element Update guides future housing development activities and does not in and of itself result in physical development. Future development of housing as anticipated by the proposed Housing Element has the potential to result in environmental impacts associated with construction and operation as described herein. However, Town of Atherton
2023 – 2031 Housing Element 127 Initial Study/Mitigated Negative Declaration 2474551.1 14537.003
compliance with City General Plan policies, municipal code requirements, uniformly applies development standards, and implementation of mitigation measures set forth herein will ensure that implementation of the proposed Housing Element results in less than significant impacts due to degradation of the environment. As such, the project will not degrade the quality of the environment, reduce habitat, or adversely affect cultural resources.
5.21(b) (Cumulatively Affect the Environment) Less Than Significant Impact:
Implementation of the proposed Housing Element, in combination with past, present, and future development in the Town would not result in long-term cumulative impacts. Future housing development will be subject to General Plan policies, state and federal regulations, uniformly applied development standards, and mitigation measures, which ensure that potential cumulative adverse effects to the environment are reduced to less than significant.
5.21(c) (Substantial Adverse Effect on Humans) Less Than Significant Impact: The proposed Housing Element, as a policy document would have no effect on humans. Development of housing and occupancy as by future residents has the potential to result in direct and indirect effects on humans if not properly controlled. With implementation of mitigation measures set forth herein, potential impacts to humans from the future development of housing as identified in the proposed Housing Element will be reduced to less than significant levels. Therefore, the project will have less than significant impacts due to substantial adverse environmental effects.
Mitigation Measure(s): None Required.
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6. REFERENCE DOCUMENTS
The following information sources were referenced in the preparation of this initial study/ mitigated negative declaration and are available for review online or at the Town of Atherton’s Planning Department, 80 Fair Oaks Lane, Atherton:
1. Air Quality and Greenhouse Gas Assessment: Atherton Housing Element Update and Zoning Code Amendments, prepared by Illingworth & Rodkin, Inc., March 7, 2024.
2. Alameda de las Pulgas Corridor Traffic Study, prepared by Advanced Mobility Group and dated January 25, 2019.
3. Archaeological Record Search and Report of Findings for the Town of Atherton Housing Element and Zoning Code Update prepared by Evans and De Shazo Archaeology Historic Preservation, February 21, 2024.
4. Atherton Resident Handbook, February 2023.
5. Athertonian Newsletter, Receive Resident Input and Review Fire Service Options, March 5, 2020.
6. Bay Area Air Quality Management District (BAAQMD), 2017 Bay Area Clean Air Plan, April 19, 2017.
7. Bay Area Air Quality Management District (BAAQMD) Justification Report: California CEQA Thresholds for Evaluating the Significance of Climate Impacts from Land Use Projects and Plans, https://www.baaqmd.gov/~/media/files/planning-and-research/ceqa/ceqa-guidelines2022/appendix-b-thresholds-for-evaluating-significance-of-climate-impacts_finalpdf.pdf?rev=10305f45037b41dba2cd1b45b288d54b&sc_lang=en, April 2022.
8. Biological Constraints Analysis Report, prepared by Monk & Associates, November 20, 2023.
9. California Building Code 2022
10. California Department of Conservation Farmland Mapping and Monitoring Program (FMMP). https://maps.conservation.ca.gov/DLRP/CIFF/, Accessed March 22, 2024.
11. California Department of Conservation, San Mateo County Tsunami Hazard Areas, Accessed August 1, 2023.
12. California Department of Finance Population and Housing Estimates for Cities, Counties, and the State – January 1, 2022 and 2023.
13. California Department of Forestry and Fire Protection, San Mateo County Very High Fire Hazard Severity Zones in Local Responsibility Area map, https://osfm.fire.ca.gov/what-wedo/community-wildfire-preparedness-and-mitigation/fire-hazard-severity-zones/fire-hazardseverity-zones-maps, November 28, 2008.
14. California Department of Forestry and Fire Protection, Wildland Urban Interface Fire Threatened Communities Map, https://www.smcgov.org/media/73086/download?inline=, 2003.
15. California Department of Housing and Community Development: Affirmatively Furthering Fair Housing, April 2021.
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16. California Energy Commission, 2019 California Energy Efficiency Action Plan, https://www.energy.ca.gov/programs-and-topics/programs/energy-efficiency-existingbuildings
17. California Energy Commission, Supply and Demand of Natural Gas in California, https://www.energy.ca.gov/data-reports/energy-almanac/californias-natural-gasmarket/supply-and-demand-natural-gas-california, Accessed December 11, 2023.
18. California Energy Commission, Total System Electric Generation (2021) https://www.energy.ca.gov/data-reports/energy-almanac/california-electricity-data/2020- total-system-electric-generation, Accessed December 11, 2023.
19. California Water Service, 2020 Urban Water Management Plan: Bear Gulch District, June 2021.
20. City/County Association of Governments of San Mateo County, Comprehensive Airport Land Use Compatibility Plan for the Environs of San Carlos Airport, October 2015.
21. City/County Association of Governments of San Mateo County, San Mateo Countywide Transportation Plan 2040, February 9, 2017.
22. County of San Mateo, Emergency Operations Plan Basic Plan, May 22, 2015.
23. County of San Mateo Office of Sustainability, Groundwater, https://www.smcsustainability.org/water/groundwater/.
24. County of San Mateo, San Mateo Plain Groundwater Basin Assessment, July 2018.
25. County of San Mateo, Water Pollution Prevention Program C.3 Regulated Projects Guide, January 2020.
26. Department of Conservation, Seismic Hazard Zone Report 111, 2006.
27. Department of Water Resources, Dam Breach Inundation Map, https://fmds.water.ca.gov/webgis/?appid=dam_prototype_v2, Accessed August 1, 2023.
28. Department of Toxic Substances Control, EnviroStor Database, https://www.envirostor.dtsc.ca.gov/public/map/, Accessed August 10, 2023.
29. State Water Resources Control Board, GeoTracker Map, https://geotracker.waterboards.ca.gov/map/?CMD=runreport&myaddress=Sacramento, Accessed August 10, 2023.
30. Federal Transit Administration, Transit Noise and Vibration Impact Assessment Manual, September 2018.
31. FEMA’s National Flood Hazard Layer (NFHL) Viewer,
https://www.arcgis.com/apps/webappviewer/index.html?id=8b0adb51996444d4879338b552 9aa9cd, Accessed August 1, 2023.
32. Franchise Agreement Between the Town of Atherton and GreenWaste Recovery, Inc., November 19, 2020.
33. GreenWaste Recovery, Inc., Atherton, https://www.greenwaste.com/atherton/.
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34. Historic Resource Evaluation: Faculty Housing Apartment 8B, Menlo College, prepared by Metropolitan Planning Group (M-Group), March 2024.
35. Memorandum: Preliminary Evaluation, prepared by Isabel Castellano, Historic Preservation Specialist, M-Group, March 11, 2024.
36. Menlo Park Fire Protection District Fire Unit Performance Data, 2023.
37. Menlo Park Fire Protection District Ordinance No. 48-2022 District Fire Prevention Code.
38. Menlo Park Fire Protection District Staff Report, Consider for Adoption a Resolution Adopting the Primary Emergency Response Routes for the Menlo Park Fire Protection District, August 16, 2011.
39. Metropolitan Transportation Commission/Association of Bay Area Governments (MTC/ABAG) Hazard Viewer Map, Earthquake Liquefaction Susceptibility, Landslide Hazard (Rainfall Induced),
https://mtc.maps.arcgis.com/apps/webappviewer/index.html?id=4a6f3f1259df42eab29b35df cd086fc8, Accessed April 11, 2024.
40. Moffat & Nichol, Redwood City Bayfront Canal and Atherton Channel Flood Improvement and Habitat Restoration Project Feasibility Study.
41. Noise and Vibration Assessment: 2023-2031 Housing Element, prepared by Illingworth and Rodkin, Inc., January 18, 2024.
42. Office of Planning & Research, Technical Advisory on Evaluating Transportation Impacts in CEQA, April 2018.
43. San Mateo County Important Farmland 2018 Map,
https://www.conservation.ca.gov/dlrp/fmmp/Pages/SanMateo.aspx, September 2019.
44. Santa Cruz Mountains Bioregional Council, About the Santa Cruz Mountains, https://www.scmbc.org/about-the-sc-mtns.
45. Sequoia Union High School District, School Impact / Developer Fees, https://www.seq.org/DEPARTMENTS/Administrative-Services/Maintenance-- Operations/School-Impact--Developer-Fees/index.html.
46. State of California Department of Finance Population and Housing Estimates for Cities, Counties and the State, January 1, 2022 and 2023.
47. State Water Resources Control Board, Construction Stormwater Program, https://www.waterboards.ca.gov/water_issues/programs/stormwater/construction.html, .
48. Town of Atherton Bicycle and Pedestrian Master Plan, July 2014.
49. Town of Atherton Climate Action Plan, November 2016.
50. Town of Atherton Drainage Criteria, January 2, 2013.
51. Town of Atherton Emergency Operations Plan, 2022.
52. Town of Atherton, Fire Services Fiscal Review, https://www.ci.atherton.ca.us/460/FireServices-Fiscal-Review .
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53. Town of Atherton General Plan 2019.
54. Town of Atherton General Plan 2019 Update Project, Draft Initial Study/Mitigated Negative Declaration (SCH #2003012009), April 4, 2019.
55. Town of Atherton Green Infrastructure Plan, September 18, 2019.
56. Town of Atherton Heritage Tree Preservation Standards and Specifications, December 2019.
57. Transportation Analysis: Atherton Housing Element Update, prepared by Hexagon Transportation Consultants, Inc., February 13, 2024.
58. United States Department of Agriculture, Natural Resources Conservation Service Web Soil Survey, https://websoilsurvey.nrcs.usda.gov/app/WebSoilSurvey.aspx, Accessed May 8, 2024.