Atherton City Council
September 18, 2024

Town of Atherton
2023 – 2031 Housing Element 56 Initial Study/Mitigated Negative Declaration 2474551.1 14537.003

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.

Town of Atherton
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
2023 – 2031 Housing Element 58 Initial Study/Mitigated Negative Declaration 2474551.1 14537.003
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
2023 – 2031 Housing Element 60 Initial Study/Mitigated Negative Declaration 2474551.1 14537.003

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
2023 – 2031 Housing Element 61 Initial Study/Mitigated Negative Declaration 2474551.1 14537.003
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
2023 – 2031 Housing Element 62 Initial Study/Mitigated Negative Declaration 2474551.1 14537.003
 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

Town of Atherton
2023 – 2031 Housing Element 63 Initial Study/Mitigated Negative Declaration 2474551.1 14537.003
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

Town of Atherton
2023 – 2031 Housing Element 64 Initial Study/Mitigated Negative Declaration 2474551.1 14537.003
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
2023 – 2031 Housing Element 65 Initial Study/Mitigated Negative Declaration 2474551.1 14537.003
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

Town of Atherton
2023 – 2031 Housing Element 66 Initial Study/Mitigated Negative Declaration 2474551.1 14537.003

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
2023 – 2031 Housing Element 67 Initial Study/Mitigated Negative Declaration 2474551.1 14537.003
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

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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

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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

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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

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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

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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

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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=

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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/

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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

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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

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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,

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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.

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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.

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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

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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.

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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

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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=

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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

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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

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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.

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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/

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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

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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

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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

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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/

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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

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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=

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2023 – 2031 Housing Element 121 Initial Study/Mitigated Negative Declaration 2474551.1 14537.003

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
2023 – 2031 Housing Element 122 Initial Study/Mitigated Negative Declaration 2474551.1 14537.003
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

Town of Atherton
2023 – 2031 Housing Element 123 Initial Study/Mitigated Negative Declaration 2474551.1 14537.003
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.

Town of Atherton
2023 – 2031 Housing Element 124 Initial Study/Mitigated Negative Declaration 2474551.1 14537.003
 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

Town of Atherton
2023 – 2031 Housing Element 126 Initial Study/Mitigated Negative Declaration 2474551.1 14537.003

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.

Town of Atherton
2023 – 2031 Housing Element 128 Initial Study/Mitigated Negative Declaration 2474551.1 14537.003

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.

Town of Atherton
2023 – 2031 Housing Element 129 Initial Study/Mitigated Negative Declaration 2474551.1 14537.003

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/.

Town of Atherton
2023 – 2031 Housing Element 130 Initial Study/Mitigated Negative Declaration 2474551.1 14537.003

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 .

Town of Atherton
2023 – 2031 Housing Element 131 Initial Study/Mitigated Negative Declaration 2474551.1 14537.003

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.

ATHERTON HOUSING ELEMENT

UPDATE AND ZONING CODE

AMENDMENTS AIR QUALITY &

GREENHOSE GAS ASSESSMENT
Atherton, California
January 25, 2024
Revised March 7, 2024
Prepared for:

Adam Petersen
Principal Planner
M-Group
1475 S. Bascom Ave, Suite 210
Campbell, CA 95008t
Prepared by:

James A. Reyff
Casey Divine
Jordyn Bauer
429 East Cotati Avenue
Cotati, CA 94931
(707) 794-0400
I&R Project: #23-116

INTRODUCTION
The purpose of this report is to address air quality, health risk, and greenhouse gas (GHG) impacts associated with buildout of the proposed Housing Element Update and resulting zoning code amendments located in Atherton, California. The air quality and GHG impacts from the Housing Element Update would be associated with construction of the new buildings and infrastructure and operation of the project. Air pollutants associated with construction and operation are addressed qualitatively since construction and operational details are not known at the level necessary to predict meaningful quantitative impacts. All analyses were conducted following guidance provided by the Bay Area Air Quality Management District (BAAQMD).1

BACKGROUND
The Town of Atherton has an area of approximately 3,600 acres or 5.6 square miles, comprised of 89% 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 2023-2031 Housing Element was passed in January 2023.

PROJECT DESCRIPTION
The Project is the proposed update to the Town of Atherton’s Housing Element 2023-2031 and the resulting amendment of Title 17 of the Town of Atherton Municipal Code that would apply overlays zones to specific properties located within the Town of Atherton, California. The proposed Project would allow for housing to be constructed on these properties, helping meet the Town’s future housing needs at all economic levels. As a policy document, the Housing Element Update and amended municipal code does not result in direct physical changes to the environment but would indirectly lead to physical environmental changes by enabling the potential development of additional housing units within the Town’s jurisdiction. Additional housing leads to additional air pollutant and GHG emissions as well as potential localized air quality impacts.

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. 1 Bay Area Air Quality Management District, 2022 CEQA Guidelines, April 2023 1

Table 1. RHNA Allocation
Income Category 6
th Cycle
RHNA
94 10% Buffer Units Total Units Percent
Extremely Low / Very Low
Low
9 5
103
59 26%
54 16%
Moderate 56 6 62 18%
Above Moderate 144
348
14 34
158
382
40%
Total 100%
Comparison of Site Inventory and RHNA
In addition to the proposed goals, objectives, policies, and programs to meet the RHNA, Atherton factored in programs including, but not limited to, a Residential Medium (RM) 10 overlay zone at 23 Oakwood, overlay zones on developed portions of open space sites, including the California Water Service site, the Circus Club, and the Gilmore House and Knox Playschool sites, vacant sites, lot splits (under the 2022 state law for urban lot splits; SB 9), private school sites, and accessory dwelling units (ADUs). The total new housing units needed to achieve the 6th Cycle RHNA are summarized in Table 2.

Table 2. Net RHNA – Projected Dwelling Units
Very Low Above
Moderate
>120%
AMI
Moderate & Low
0-80%
AMI
Total New
81-120% Housing Units
AMI
Projected Dwelling Units
ADUs 112
0 56
0 112
48 9
280
Lot Splits (SB 9) 48
Vacant Sites 0 0 9
RM 10 (23 Oakwood)
PFS (Private Schools)
4 0 12
0 16
96 95 191
Multi-Family
Opportunity Sites
Residential 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 accessory, 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). 2

In 2021 and 2022, the Town of Atherton experienced the construction of 44 new ADUs, three (3) JADUs, and seven (7) ADU conversions. 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.

SB 9
Senate Bill 9 or 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.

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.

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.
3

Table 3.

Site
Vacant Sites
Max. Primary Potential Net Reason not
selected as
Opportunity
Site
Lot Current
Zoning
Units under
current
New Primary
Units under
SB-9
APN Address ID Acres
Zoning
SB-9 application
filed. City Council
decision on
7/19/23.

City Council
070-
343-100
97 Santiago
Ave. V1
V2

1.42 2.12
R-1A
R1-A
1 2
4 decision on 070-
012-270
Polhemus
Ave. 4 7/19/23. Discussed
as part of 290
Polhemus Ave.

Not fully vacant.

Improved with
tennis court,
070-
180-400
95 Faxon
Road
landscaping &
walkways. Serves
as extended rear
yard of adjacent
property.

V3 1.13 R1-A 1 4
Not located on
major road or near
public & private
services.

Not located on
major road or near
public & private
services.
12 Faxon
Forest
Road
V4
V5
070-
180-340 0.95

0.85 R1-A
R1-A
1 1
4 4
16 Faxon
Forest
Road
070-
180-350
No Address
(Located
between 7
& 11
Faxon
Forest Rd.)
Not located on
major road or near
public & private
services.
070-
180-290 V6
V7
V8

1.00 1.78

0.98 R1-A
R1-A
R1-A
1 1
4 4
Not fully vacant.

Portion occupied
by existing house.

Part of a larger
estate, approx. 12.6
acres.

Not fully vacant.

Portion occupied
by existing house.

Part of a larger
estate, approx. 12.6
acres.
070- 15 Monte
131-010 Vista Ave.
070- 25 Monte
180-020 Vista Ave. 1 4
TOTAL PRIMARY HOUSING UNITS 9 32
4

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. 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 seven (7) sites as multi-family residential opportunity sites, in addition to the ADU, SB 9, and vacant sites identified above. The Town is proposing to either rezone or adopt an overlay zone on these 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 separately and after adoption and certification of the Housing Element. A list of sites for multifamily residential opportunities is identified in Table 4.

The rezoning or zoning overlay allows residential units to be built at a density of 10 dwelling units per acre. Potential units were calculated would yield a total of 68 units on approximately 6.89 acres of land.

Table 4.

Site ID
Multi-Family Residential Opportunity Sites
Proposed Net
Residential Units from
Zoning Overlay
Existing Proposed Zoning Address Lot Acres Zoning Overlay MFO-1
MFO-2
MFO-3
MFO-4
MFO-5
MFO-6
MFO-7
999 Ringwood Ave.
352 Bay Rd.

0.90 0.92

0.94 0.93

1.1 R-1A
R-1A
R-1A
R-1A
R-1A
R-1A
R-1A
R-10
R-10
R-10
R-10
R-10
R-10
R-10
9 9
318 Bay Rd. 9
296 Bay Rd. 9
175 Ravenswood
185 Ravenswood
197 Ravenswood
TOTALS
11 11
10 68

1.1 1

6.89 Municipal Code Changes
Implementation of the Housing Element would effectuate the following zoning changes to the Atherton Municipal Code:
• RM-10 Overlay Zone – Public Open Space Sites: The project proposes an amendment to the Town’s Municipal Code of an RM-10 overlay to permit multifamily residential uses by right in the developed areas of properties in the Public Open Space zone. This includes the following: approximately 0.9 acres of Holbrook Palmer Park, occupied by the Gilmore 5

House; approximately 0.5 acres of developed portions of the Circus Club; and approximately 0.25 acres of portions of the California Water Service site at Bear Gulch Reservoir that are currently developed with offices or an ancillary off-street parking area. • RM-10 Overlay Zone – 23 Oakwood: The project proposes an amendment to the Town’s Municipal Code of an RM-10 overlay zone to permit multifamily residential uses by right.

Included in the amendment request is a maximum density of 10 dwelling units per acre, building height standards of 40 feet, setbacks to accommodate the density, parking, and objective design standards. The site would yield 16 dwelling units. • Menlo College Overlay Zone – 1000 El Camino Real: Implementation of the Housing Element would institute an overlay zone on three locations of the Menlo College site as described:
o 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 lot is surrounded by mature vegetation. Construction of a multi-family housing building is feasible at this location with podium parking at ground level and three-stories of housing above, or below grade parking. The Town does not have on-site parking requirements. Parking would be replaced to meet the needs of the college. The Town will amend the PFS zone, implementing an overlay zone on this site that permits 40 units per acre by right with objective design standards. The College has expressed interest in developing 60 dwelling units at this site. o Site 2: There are four residences located on the campus in World War II era houses that are currently utilized for faculty housing. Demolition of these residences would accommodate 30 apartment units, resulting in a net increase of 26 multifamily housing units. The Town will amend the PFS zone, implementing an overlay zone on this site that permits a density of 20 units per acre by right with objective design standards.
o 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. Additional parking can be developed near the entry to the College off El Camino Real. The Town will amend the PFS zone, implementing an overlay zone on this site that permits 40 units per acre by right with objective design standards.

Additional actions for all three sites include reducing the minimum front yard setback to 30 feet, amending the height limit to allow up to four-stories or 48 feet, permitting multifamily housing by right with objective design standards. • Menlo School Overlay Zone – 50 Valparaiso Avenue: Implementation of the Housing Element would implement an overlay zone at two locations on the Menlo School as described below:
6

o 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 by right with objective design standards. This site would yield 25 dwelling units. o 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 by right with objective design standards, this site could yield approximately 20 dwelling units.

To accommodate the new housing development, the zoning will be amended as follows:
o Reduce the minimum front yard setback to 30 feet (along Valparaiso Road). o Amend the height limit to allow four-stories or 48 feet. o Permit multifamily housing by right with objective design standards. • Sacred Heart Overlay Zone – 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. • Implementation of the Housing Element would amend the ADU provisions of the Atherton Municipal Code, permitting the following:
o Second story ADUs above detached garages, increasing the allowable height to 18 feet.
o Two ADUs to be constructed on properties two-acres or greater in area; the first ADU is exempt from floor area limitations and the second ADU will be included in the ADU floor area.
o Allow pool housing and guest houses to be rented as ADUs. o Waiving fees for all new ADUs.
o Eliminating the owner occupancy limitation on ADUs, including guest and pool houses.

Further, implementation of the Housing Element would result in the following amendments to the Atherton Municipal Code:
7

• 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.
• Permitting Low Barrier Navigation Centers in zones where multi-family and mixed uses are permitted.
• Permitting mobile homes and manufactured housing on a permanent foundation under the same manner as single-family homes.
• Allowing group homes for seven (7) or more residents in any district where residential uses are permitted.
• Permitting shelters, and amending their parking requirements, without discretionary action. • Amending the minimum lot size in the R-1B and subdivision ordinance allowing one-third (0.33) acre lots for the subject zone.

REGULATORY FRAMEWORK
Air pollutants are governed by multiple federal and state standards to regulate and mitigate health impacts. The pollutants regulated by the US EPA include” criteria” pollutants and 188 air toxics referred to as hazardous air pollutants (HAPs). Considering all the HAPs, the EPA has identified nine compounds with significant contributions from mobile sources that are among the national and regional-scale cancer risk drivers or contributors and non-hazard contributors. These are 1,3- butadiene, acetaldehyde, acrolein, benzene, diesel particulate matter (DPM), ethylbenzene, formaldehyde, naphthalene, and polycyclic organic matter.

The State of California also regulates criteria pollutants, which include the federal list but also adds pollutants specific to certain industries, such as hydrogen sulfide and vinyl chloride. The State also regulates HAPs, which are referred to as TACs. The common pollutants, their potential sources, and effects are summarized in Table 5.
8

Table 5. Health Effects of Air Pollutants
Pollutants Sources Primary Effects
• Incomplete combustion of fuels
and other carbon-containing
substances, such as motor exhaust.

Natural events, such as
decomposition of organic matter.

Motor vehicle exhaust.

High temperature stationary
combustion.

Atmospheric reactions.
•
•
•
•
•
•
•
•
•
•
Reduced tolerance for exercise.

Impairment of mental function.

Impairment of fetal development.

Death at high levels of exposure.

Aggravation of some heart diseases (angina).

Aggravation of respiratory illness.

Reduced visibility.

Reduced plant growth.

Formation of acid rain.

Aggravation of respiratory and cardiovascular
diseases.

Irritation of eyes.

Impairment of cardiopulmonary function.

Plant leaf injury.

Impairment of blood functions and nerve construction.

Behavioral and hearing problems in children.

Reduced lung function.

Aggravation of the effects of gaseous pollutants.

Aggravation of respiratory and cardiorespiratory
diseases.

Increased cough and chest discomfort.

Soiling.

Reduced visibility.

Aggravation of respiratory diseases (asthma,
emphysema).

Reduced lung function.

Carbon
Monoxide (CO)
•
•
Nitrogen •
Dioxide (NO2)
•
• Atmospheric reaction of organic
gases with nitrogen oxides in
sunlight. Ozone
(O3)
•
•
•
• •
•
Contaminated soil. Lead
(Pb)
•
•
•
•
Stationary combustion of solid
fuels.

Construction activities.

Industrial processes.

Suspended
Particulate
Matter
•
•
(PM • 2.5 and
PM )
Atmospheric chemical reactions. •
•
•
•
10 •
•
•
Combustion of sulfur-containing
fossil fuels.

Smelting of sulfur-bearing metal
ores.
•
•
•
•
•
Sulfur Dioxide
(SO2)
Irritation of eyes.

Reduced visibility.

Plant injury.

Deterioration of metals, textiles, leather, finishes,
coatings, etc.

Industrial processes.
•
•
•
•
Cars and trucks, especially diesel
engines.

Industrial sources such as chrome
platers.

Neighborhood businesses such as
dry cleaners and service stations.

Building materials and product.
•
•
•
Cancer.

Chronic eye, lung, or skin irritation.

Neurological and reproductive disorders. Toxic Air
Contaminants
Source: CARB, 2009. ARB Fact Sheet: Air Pollution and Health, see:
https://www.arb.ca.gov/research/health/fs/fs1/fs1.htm
Federal Air Quality Regulations
At the federal level, the EPA has been charged with implementing national air quality programs.

EPA’s air quality mandates are drawn primarily from the Federal Clean Air Act (FCAA), which was enacted in 1963. The FCAA was amended in 1970, 1977, and 1990. Pursuant to the FCAA of 1970, the EPA established National Ambient Air Quality Standards (NAAQS) for the following criteria pollutants:
9

Ozone (O3) -Ozone is a secondary air pollutant produced in the atmosphere through a complex series of photochemical reactions involving reactive organic gases (ROG) and oxides of nitrogen (NO ). The main sources of ROG and NO , often referred to as ozone precursors, are X X combustion processes (including combustion in motor vehicle engines) and the evaporation of solvents, paints, and fuels. In the Bay Area, automobiles are the single largest source of ozone precursors. Ozone is referred to as a regional air pollutant because its precursors are transported and diffused by wind concurrently with ozone production through the photochemical reaction process. Ozone is a powerful oxidant that is harmful to public health at high concentrations.

Ozone, at high levels, can damage the tissues of the lungs and respiratory tract. High concentrations of ozone irritate the nose, throat, and respiratory system and constrict the airways.2 Ozone also can aggravate other respiratory conditions such as asthma, bronchitis, and emphysema, causing increased hospital admissions. Repeated exposure to high ozone levels can make people more susceptible to respiratory infection and lung inflammation and permanently damage lung tissue. Ozone can also have negative cardiovascular impacts, including chronic hardening of the arteries and acute triggering of heart attacks.

Carbon Monoxide - Carbon monoxide (CO) is an odorless, colorless gas usually formed as the result of the incomplete combustion of fuels. The single largest source of CO is motor vehicles.

While CO transport is limited, it disperses with distance from the source under normal meteorological conditions. However, under certain extreme meteorological conditions, CO concentrations near congested roadways or intersections may reach unhealthful levels that adversely affect local sensitive receptors (e.g., residents, schoolchildren, the elderly, hospital patients, etc.). Typically, high CO concentrations are associated with roadways or intersections operating at unacceptable levels of service (LOS) or with extremely high traffic volumes.

Exposure to high concentrations of CO reduces the oxygen-carrying capacity of the blood and can cause headaches, nausea, dizziness, fatigue, impair central nervous system function, and induce angina (chest pain) in persons with serious heart disease. Very high levels of CO can be fatal.

Nitrogen Dioxide - Nitrogen Dioxide (NO2) is a reddish-brown gas that is a byproduct of combustion processes. Automobiles and industrial operations are the main sources of NO2.

Aside from its contribution to ozone formation, NO2 also contributes to other pollution problems, including a high concentration of fine particulate matter, poor visibility, and acid deposition. NO2 may be visible as a coloring component on high pollution days, especially in conjunction with high ozone levels. NO2 decreases lung function and may reduce resistance to infection.

Sulfur Dioxide - Sulfur dioxide (SO2) is a colorless, irritating gas formed primarily from incomplete combustion of fuels containing sulfur. Industrial facilities also contribute to gaseous SO levels in the region. SO irritates the respiratory tract, can injure lung tissue when 2 2 combined with fine particulate matter, and reduces visibility and the level of sunlight. 2 See: California Air Resource Board, Web: https://ww2.arb.ca.gov/resources/ozone-and-health 10

Particulate Matter - Particulate matter is the term used for a mixture of solid particles and liquid droplets found in the air. Coarse particles are those that are larger than 2.5 microns but smaller than 10 microns (PM10). PM2.5 refers to fine suspended particulate matter with an aerodynamic diameter of 2.5 microns or less that is not readily filtered out by the lungs. Nitrates, sulfates, dust, and combustion particulates are major components of PM10 and PM2.5. These small particles can be directly emitted into the atmosphere as by-products of fuel combustion, through abrasion, such as tire or brake lining wear, or through fugitive dust (wind or mechanical erosion of soil). They can also be formed in the atmosphere through chemical reactions. Particulates may transport carcinogens and other toxic compounds that adhere to the particle surfaces and can enter the human body through the lungs.

Lead - Lead is a metal found naturally in the environment as well as in manufactured products.

The major sources of lead emissions have historically been mobile and industrial sources. As a result of the phase-out of leaded gasoline in the 1990’s, metal processing is currently the primary source of lead emissions. The highest levels of lead emissions are generally found near lead smelters. Other stationary sources are waste incinerators, utilities, and lead-acid battery manufactures.

NAAQS include both primary and secondary standards. Primary standards set limits to protect public health, including the health of sensitive populations such as asthmatics, children, and the elderly. Secondary standards set limits to protect public welfare, including protection against decreased visibility, damage to animals, crops, vegetation, and buildings.3 Areas (i.e., air basins) that do not meet the NAAQS, or nonattainment areas, are required to develop State Implementation Plans (SIPs) that are designed to bring them into attainment of the NAAQS by specific dates.

The FCAA Amendments of 1990 changed deadlines for attaining NAAQS as well as the remedial actions required of areas of the nation that exceed the standards. Conformity with an area’s SIP requirements satisfy the FCAA requirements for a given project.

State Air Quality Regulations
California Clean Air Act
In 1988, the CCAA established its own, more stringent ambient air quality standards, known as California Ambient Air Quality Standards (CAAQS). The CCAA requires that all air basins in the state endeavor to achieve and maintain CAAQS for CO, O , SO , and NO by the earliest practical 3 2 2 date. The CCAA establishes local air districts and provides them with authority to regulate indirect sources and mandates that air quality districts focus particular attention on reducing emissions from transportation and area-wide emission sources. Each nonattainment area in the State is required to adopt a plan to achieve a 5 percent annual reduction, averaged over consecutive 3-year periods, for each nonattainment pollutant or its precursors. A Clean Air Plan is a SIP that shows how a district would reduce emissions to achieve air quality standards. 3 See: U.S. Environmental Protection Agency, Web: https://www.epa.gov/criteria-air-pollutants/naaqs-table, Accessed 13 August 2020
11

California Air Resources Board
The California Air Resources Board (CARB) is the agency responsible for coordination with the EPA and developing SIPs to achieve and maintain both the NAAQS and CAAQS. As a result, it has oversight of the state’s air pollution control programs. Other CARB duties include monitoring air quality (in conjunction with air monitoring networks maintained by air pollution control and air quality management districts), determining and updating area designations and maps, and setting emissions standards for new mobile sources, consumer products, small utility engines, and off-road vehicles.

California Air Resources Board Handbook
In 1998, CARB identified particulate matter from diesel-fueled engines (i.e., DPM) as a toxic air contaminant. CARB has completed a risk management process that identified potential cancer risks for a range of activities using diesel-fueled engines.4 CARB subsequently developed an Air Quality and Land Use Handbook5 (Handbook) in 2005 that is intended to serve as a general reference guide for evaluating and reducing air pollution impacts associated with new projects that go through the land use decision-making process. The 2005 CARB Handbook recommends that planning agencies consider proximity to air pollution sources when considering new locations for “sensitive” land uses, such as residences, medical facilities, daycare centers, schools, and playgrounds.

Air pollution sources of concern include freeways, rail yards, ports, refineries, distribution centers, chrome plating facilities, dry cleaners, and large gasoline service stations. Key recommendations in the Handbook relative to the Plan Area include taking steps to consider or avoid siting new, sensitive land uses:
• Within 500 feet of a freeway, urban roads with 100,000 vehicles/day or rural roads with 50,000 vehicles/day.
• Within 300 feet of gasoline fueling stations (note that new fueling stations utilize enhanced vapor recovery systems that substantially reduce emissions). • Within 300 feet of dry-cleaning operations (note that dry cleaning with TACs is being phased out and will be prohibited in 2023).

Advanced Clean Cars
The Advanced Clean Cars Program, adopted by CARB in 2012, was designed to bring together CARB’s traditional passenger vehicle requirements to meet federal air quality standards and also support California’s AB 32 goals to develop and implement programs to reduce GHG emissions back down to 1990 levels by 2020, a goal achieved in 2016 as a result of numerous emissions reduction programs.
4 California Air Resources Board, 2000. Risk Reduction Plan to Reduce Particulate Matter Emissions from Diesel-Fueled Engines and Vehicles. October.
5 California Air Resources Board, 2005. Air Quality and Land Use Handbook: A Community Health Perspective.

April.
12

This recent rule, Advanced Clean Cars II (ACC II) is phase two of the original rule. ACC II establishes a year-by-year process, starting in 2026, to have all new cars and light trucks sold in California be zero emission vehicles (ZEVs) by 2035. The regulation codifies the light-duty vehicle goals set out in Governor Newsom’s Executive Order N-79-20. Currently, 16 percent of new light-duty vehicles sold in California are zero emissions or plug-in hybrids. By 2030, 68 percent of new vehicles sold in California would be zero emissions and 100 percent by 2035.

On-road Heavy-Duty Diesel Vehicle Regulations
CARB is actively enforcing on-road heavy-duty diesel vehicle regulations that require fleets to replace or retrofit older heavy-duty diesel vehicles. As of January 1, 2020, the DMV cannot register any vehicle that does not meet the diesel engine replace/retrofit requirements. Other CARB diesel programs affecting heavy-duty diesel vehicles include:
• Idling limits of no more than 5 minutes with special exceptions. • Emission Control Labels must be affixed to engines of all commercial heavy-duty diesel vehicles, and must be legible as proof the engine, at minimum, meets U.S. federal emissions standards for the engine model year.
• The Periodic Smoke Inspection Program requires owners of California-based fleets of two or more diesel vehicles to perform annual smoke opacity tests and to keep records for at least two years for each vehicle.
• The Heavy-Duty Vehicle Inspection Program uses random roadside inspections to verify that diesel engines do not smoke excessively and are tamper-free.

Advanced Clean Trucks (ACT)
California’s Advanced Clean Trucks (ACT) rule increases the percentage of medium and heavyduty trucks sold as ZEVs beginning in 2024. By 2035, 40 to 75 percent of new trucks sold, depending on size, would have to meet ZEV requirements. In addition, large employers including retailers, manufacturers, brokers, and others are required to report about their existing fleet operations and report information about shipments and shuttle services with 50 or more trucks,.

Off-Road Vehicle and Equipment Regulations
CARB has adopted and implemented regulations to reduce DPM and nitrogen oxides (NOx) emissions from in-use (existing) and new off-road heavy-duty diesel vehicles (e.g., loaders, tractors, bulldozers, backhoes, off-highway trucks, etc.). The regulations apply to diesel-powered off-road vehicles with engines 25 horsepower (hp) or greater. The regulations are intended to reduce particulate matter and NOx exhaust emissions by requiring owners to turn over their fleet (replace older equipment with newer equipment) or retrofit existing equipment in order to achieve specified fleet-averaged emission rates. Implementation of this regulation, in conjunction with stringent Federal off-road equipment engine emission limits for new vehicles, is expected to substantially reduce emissions of DPM and NOx.

Fleet owners must report the vehicle and engine information for all vehicles within their fleets operating in California. Fleet owners must also report owner information using DOORS, which is 13

CARB’s online reporting tool. CARB issues a unique Equipment Identification Number (EIN) that is assigned to each vehicle. The fleet owner must label their vehicles with the EIN.

Other CARB diesel programs affecting off-road vehicles and equipment include:
• Idling limits of no more than 5 minutes with special exceptions. • Portable engines 50 hp or greater may require a permit or registration to legally operate.

Bay Area Air Quality Management District
The BAAQMD is the local air quality management authority charged with attainment of the NAAQS/CAAQS and maintenance of air quality in the San Francisco Bay Area Air Basin (SFBAAB). They do this through a comprehensive program of planning, regulation, enforcement, technical innovation, and education. The BAAQMD also inspects stationary sources and responds to citizen complaints, monitors ambient air quality and meteorological conditions, and implements programs and regulations required by law.

Clean Air Plan
The BAAQMD is responsible for developing a Clean Air Plan which guides the region’s air quality planning efforts to attain the NAAQS and CAAQS. The BAAQMD’s 2017 Clean Air Plan is the latest air quality plan which contains district-wide control measures to reduce ozone precursor emissions (i.e., ROG and NOX), particulate matter, and greenhouse gas (GHG) emissions. The 2017 Clean Air Plan, which was adopted on April 19, 2017 by the BAAQMD’s board of directors:
• Updates the Bay Area 2010 Clean Air Plan in accordance with the requirements of the CCAA to implement “all feasible measures” to reduce ozone; • Provides a control strategy to reduce ozone, particulate matter, air toxics, and GHGs in a single, integrated plan;
• Reviews progress in improving air quality in recent years; and • Continues and updates emission control measures.

Planning Healthy Places
BAAQMD developed a guidebook that provides air quality and public health information intended to assist local governments in addressing potential air quality issues related to exposure of sensitive receptors to exposure of emissions from local sources of air pollutants. The guidance provides tools and recommends best practices that can be implemented to reduce exposures. The information is provided as recommendations to develop policies and measures in city or county General Plans, neighborhood or specific plans, land use development ordinances, or into projects. 14

BAAQMD California Environmental Quality Act Air Quality Guidelines The BAAQMD California Environmental Quality Act (CEQA) Air Quality Guidelines6 were prepared to assist in the evaluation of air quality impacts of projects and plans proposed within the Bay Area. The guidelines provide recommended procedures for evaluating potential air impacts during the environmental review process consistent with CEQA requirements including thresholds of significance, mitigation measures, and background air quality information. They also include assessment methodologies for TACs, odors, and GHG emissions. In June 2010, the BAAQMD’s Board of Directors adopted CEQA thresholds of significance and an update of their CEQA Guidelines. In May 2011, the updated BAAQMD CEQA Air Quality Guidelines were amended to include a health risk and hazards threshold for new receptors and modify procedures for assessing impacts related to TAC impacts. The Guidelines were then updated in May 2017 and again in April 2023, and this version serves as the Air District’s most recent CEQA guidance. The updated guidelines provide recommended procedures for evaluating potential air impacts during the environmental review process consistent with CEQA requirements including thresholds of significance, mitigation measures, and background air quality information. They include assessment methodologies for air toxins, odors, and GHG emissions.

Per Appendix G of the CEQA Guidelines, air quality and GHG impacts are considered significant if implementation of the General Plan (or specific area plan) would:
1) Conflict with or obstruct implementation of an applicable air quality plan. 2) 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.
3) Expose sensitive receptors to substantial pollutant concentrations. 4) Result in other emissions (such as those leading to odors) adversely affecting a substantial number of people.
5) Generate greenhouse gas emissions, either directly or indirectly, that may have a significant impact on the environment.
6) Conflict with an applicable plan, policy, or regulation adopted for the purpose of reducing the emissions of greenhouse gases.

Additionally, specific projects within a planning area that have TAC emissions that could adversely affect sensitive receptors must prepare a health risk assessment to quantify the potential risks to the community and, if appropriate, identify mitigation measures to reduce impacts.

The BAAQMD’s current significance thresholds are listed in Table 6 and Table 7. Though not necessarily a CEQA issue, the effect of existing TAC sources on future sensitive receptors (e.g., residences) is requested by BAAQMD to comply with the 2017 Clean Air Plan’s key goal of reducing population TAC exposure and protecting public health in the Bay Area. 6 Bay Area Air Quality Management District, 2022 CEQA Guidelines, April 2023 15

Table 6. BAAQMD Plan-Level Air Quality Significance Thresholds Pollutant/
Contaminant
Criteria Air
Pollutants and
Precursors
Construction Operational

1. Consistency with Current Air Quality Plan control measures.

2. Projected vehicle miles traveled (VMT) or vehicle trip increase is less than or equal to projected population increase.

1. Overlay zones around existing and planned sources of TACs (including adopted Risk Reduction Plan areas).

2. Overlay zones of at least 500 feet from all freeways and highvolume roadways.

None
Risks and Hazards None For this analysis – overlay zones are based on potential for sources to result in the following impacts:

1. Excess cancer risk >10.0 chances per million

2. Annual PM2.5 Concentration > 0.3 µg/m3

3. Hazard Index >1.0
Identify the location, and include policies to reduce the impacts, of existing or planned sources of odors

1. Meet State’s goals to reduce emissions to 40% below 1990 levels by 2030 and carbon neutrality by 2045; OR

2. Be consistent with a local GHG reduction strategy that meets the criteria under State CEQA Guidelines Section 15183.5(b) Odors None
Greenhouse gases None
16

Table 7. BAAQMD Project-Level Air Quality Significance Thresholds Construction Thresholds
Average Daily Emissions
Operational Thresholds
Average Daily Annual Average
Emissions (lbs./day) Emissions (tons/year)
Criteria Air
Pollutant (lbs./day)
ROG
NOX
PM10
PM2.5
54 54
54 54
82 54
10 10
15 10
82 (Exhaust)
54 (Exhaust)

9.0 ppm (8-hour average) or 20.0 ppm (1-hour
average) CO Not Applicable
Construction Dust Ordinance or other
Best Management Practices (BMPs)* Fugitive Dust Not Applicable Health Risks
and Hazards
Single Sources/
Individual Project
Combined Sources (Cumulative from all
sources within 1000-foot zone of influence)
Excess Cancer
Risk
>10 in a
million
OR >100 in a million OR Compliance with
Qualified Compliance with
Hazard Index Qualified Community >1.0 >10.0
Community
Incremental
annual PM2.5
Risk Reduction Plan >0.3 µg/m3 Risk Reduction Plan >0.8 µg/m3 Greenhouse Gas Emissions
A. Projects must include, at a minimum, the following project design elements:

1. Buildings
a. The project will not include 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
a. Achieve a reduction in project-generated 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:

Land Use Projects
– (Must Include A
or B)
i.
ii.
iii.

Residential projects: 15 percent below the existing VMT per capita Office projects: 15 percent below the existing VMT per employee Retail projects: no net increase in existing VMT
b. Achieve compliance with off-street electric vehicle requirements in the most recently adopted version of CALGreen Tier 2.

B. Be consistent with a local GHG reduction strategy that meets the criteria under State CEQA Guidelines Section 15183.5(b).

Note: ROG = reactive organic gases, NOX = nitrogen oxides, PM10 = course particulate matter or particulates with an aerodynamic diameter of 10 micrometers (µm) or less, PM2.5 = fine particulate matter or particulates with an aerodynamic diameter of 2.5µm or less. GHG = greenhouse gases.
* BAAQMD strongly recommends implementing all feasible fugitive dust management practices especially when construction projects are located near sensitive communities, including schools, residential areas, or other sensitive land uses.

Source: Bay Area Air Quality Management District, 2022
The BAAQMD recommends all projects include a “basic” set of best management practices (BMPs) to manage fugitive dust and consider impacts from dust (i.e., fugitive PM and PM ) to 10 2.5 be less than significant if BMPs are implemented.
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Basic Best Management Practices: Include measures to control dust and exhaust during construction.

During any construction period ground disturbance, the applicant shall ensure that the project contractor implement measures to control dust and exhaust. Implementation of the measures recommended by BAAQMD and listed below would reduce the air quality impacts associated with grading and new construction to a less-than-significant level. The contractor shall implement the following BMPs that are required of all projects:

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 off-site shall be covered.

3. All visible mud or 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 possible.

Building pads shall be laid as soon as possible 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. Publicly visible signs shall be posted with the telephone number and name of the person to contact at the lead agency regarding dust complaints. This person shall respond and take corrective action within 48 hours. The Air District’s General Air Pollution Complaints number shall also be visible to ensure compliance with applicable regulations.

BAAQMD strongly encourages enhanced BMPs for construction sites near schools, residential areas, or other sensitive land uses. Enhanced measures include:
• Limit the simultaneous occurrence of excavation, grading, and ground-disturbing construction activities.
• Install wind breaks (e.g., trees, fences) on the windward side(s) of actively disturbed areas of construction. Wind breaks should have at maximum 50 percent air porosity. 18

• Plant vegetative ground cover (e.g., fast-germinating native grass seed) in disturbed areas as soon as possible and watered appropriately until vegetation is established. • Install sandbags or other erosion control measures to prevent silt runoff to public roadways from sites with a slope greater than one percent.
• Minimize the amount of excavated material or waste materials stored at the site. • Hydroseed or apply non-toxic soil stabilizers to construction areas, including previously graded areas, that are inactive for at least 10 calendar days.

CARE Program
The BAAQMD’s Community Air Risk Evaluation (CARE) program was initiated in 2004 to evaluate and reduce health risks associated with exposures to outdoor TACs in the Bay Area.7 The program examines TAC emissions from point sources, area sources, and on-road and off-road mobile sources with an emphasis on diesel exhaust, which is a major contributor to airborne health risk in California. The CARE program is an on-going program that encourages community involvement and input. The technical analysis portion of the CARE program has been implemented in three phases that includes an assessment of the sources of TAC emissions, modeling and measurement programs to estimate concentrations of TAC, and an assessment of exposures and health risks. Throughout the program, information derived from the technical analyses has been used to focus emission reduction measures in areas with high TAC exposures and high density of sensitive populations. Risk reduction activities associated with the CARE program are focused on the most at-risk communities in the Bay Area. The BAAQMD has identified six communities as impacted: Concord, Richmond/San Pablo, Western Alameda County, San José, Redwood City/East Palo Alto, and Eastern San Francisco.

Overburdened Communities Program
To address localized health impacts in Bay Area communities, BAAQMD staff met with community advocacy organizations to develop concepts and recommendations on how the air district could be more health protective. Through a series of public workshops and a public comment period, BAAQMD amended Rule 2 (i.e., Regulation 2-1-24) in 2021. It identifies an overburdened community as an area located (i) within a census tract identified by the California Office of Environmental Health Hazard Assessment's (OEHHA’s) Communities Environmental Health Screening Tool (CalEnviroScreen), Version 4.0, as having an overall score at or above the 70th percentile, or (ii) within 1,000 feet of any such census tract. Projects in overburdened communities must conduct specific public involvement activities and stationary sources are subject to specific permitting requirements. The entire Town of Atherton fall under the 10th percentile in CalEnviroScreen.
7 See BAAQMD: https://www.baaqmd.gov/community-health/community-health-protection-program/communityair-risk-evaluation-care-program. 19

Atherton General Plan
The Atherton General Plan, adopted in November 2002 and updated in 2019, includes goals, objectives, policies, and actions to reduce exposure of the Town’s sensitive population to exposure of air pollution and toxic air contaminants or TACs. The following objectives, goals, policies, and actions relevant to air quality are contained in the Land Use, Circulation, and Open Space & Conservation Elements.

Land Use.

Goal LU-1 To preserve the Town’s character as a scenic, semi-rural, thickly-wooded residential area with abundant open space.

Policies:

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.
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 to minimize the discharge of pollutants into the waterways.
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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.

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.

Circulation.

Goal CIR-1 To develop a circulation system that is compatible with the needs of various land uses planned within the Town of Atherton.

Policies:

CIR-1.7: Paving for temporary on-street parking within the roadway right-of-way will be prohibited.

CIR-1.13: On-street and visible off-street parking shall be preserved to the extent consistent with traffic safety.

Goal CIR-4 To achieve a balanced, multi-modal transportation network that meets the needs of all users of Atheron streets and highways for safe and convenient travel in a manner that is suitable to the semi-rural context of the general plan.

Policies:

CIR-4.1: To incorporate, over time and where feasible, the principles of Complete Streets in future roadway projects. Complete Streets are streets and facilities that accommodate all users including bicyclists, children, persons with disabilities, motorists, movers of commercial goods, pedestrians, users of public transportation, and seniors.

CIR-4.2: Bicycle paths separating bicycles from vehicular traffic are considered desirable.

Goal CIR-5 To achieve a high quality of roadway operation on all Atherton streets.

Policies:

CIR-5.6: The Town shall support the continued operation and upgrading of passenger rail service operated over the Joint Powers Board right-of-way between Gilroy and San Francsico.

Open Space and Conservation.

Goal OSC-1 Protect both publicly and privately held open space lands from deterioration of their semi-rural charm, scenic value and environmental equilibrium. 21

Action
OSC-1.1: Minimum lot sizes, setback restrictions, height limitations, tree protection and preservation, and sign regulations shall be employed to accomplish open space and conversation objections.

Goal OSC-2 Protect and enhance the existing Coastal Oak Woodland character of the Town.

Policies
OSC-2.1: Trees shall be preserved where practical. This policy shall be explicitly considered during the development and subdivision process.

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.

OSC-2.3: Enforce the Heritage Tree Ordinance and Tree Preservation Guidelines and Standards, or equal document.

Goal OSC-3 Minimize the impacts of flooding on health, safety, and property damage.

Actions
OSC-3.2: The Town will encourage property owners to incorporate water conservation techniques into their landscaping to reduce water usage and use green infrastructure techniques to capture and/or treat rainfall and stormwater runoff at its source, as feasible.

Goal OSC-5 Implement the GHG programs in the Atheron Climate Action Plan related to energy efficiency, community waste generation, and reduced water consumption.

SETTING AND EXISTING AIR QUALITY CONDITIONS
The project is located in San Mateo County, which is part of the San Francisco Bay Area Air Basin.

The Air Basin includes the counties of San Francisco, Santa Clara, San Mateo, Marin, Napa, Contra Costa, and Alameda, along with the southeast portion of Sonoma County and the southwest portion of Solano County.

This Project is within the jurisdiction of the BAAQMD. Air quality conditions in the San Francisco Bay Area have improved significantly since the BAAQMD was created in 1955. Ambient concentrations of air pollutants, and the number of days during which the region exceeds air quality standards, have fallen dramatically. Exceedances of air quality standards occur primarily during meteorological conditions conducive to high pollution levels, such as cold, windless winter nights or hot, sunny summer afternoons.
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Air quality is a function of both local climate and local sources of air pollution. Air quality is the balance of the natural dispersal capacity of the atmosphere and emissions of air pollutants from human uses of the environment. Climate and topography are major influences on air quality.

Climate and Meteorology
During the summer, mostly clear skies result in warm daytime temperatures and cool nights in the Santa Clara Valley. Winter temperatures are mild, except for very cool but generally frost-less mornings. Further inland where the moderating effect of the bay is not as strong, temperature extremes are greater. Rainfall amounts are modest, ranging from 13 inches in the lowlands to 20 inches in the hills. Wind patterns are influenced by local terrain, with a northwesterly breeze in response to the sea breeze infiltrating San Francisco Bay typically developing during the daytime.

Winds are usually stronger in the spring and summer. The southerly winds experienced are more common in late fall and winter. The wind rose shown in Figure 1 describes the patterns and frequency of winds at the San Carlos Airport near the Town. Wind data was collected from 2011 through 2015.

Figure 1. Windrose for San Carlos Airport Years 2011-2015 Notes: Based on data provided by BAAQMD
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NAAQS and CAAQS Status
Both the US EPA and CARB designate air basins as attainment, nonattainment, or unclassified based on ambient monitoring data. An “attainment” designation for an area signifies that pollutant concentrations did not violate the standard for that pollutant in that area. A “nonattainment” designation indicates that a pollutant concentration violated the standard at least once, excluding those occasions when a violation was caused by an exceptional event, as defined in the criteria.

An “unclassified” designation signifies that data does not support either an attainment or nonattainment status, or that monitoring data were not available. Table 8 shows the state and federal standards for criteria pollutants and provides a summary of the attainment status for the San Francisco Bay Area.

Table 8. NAAQS and CAAQS and Air Basin Attainment Status State Federal
Averaging
Time Pollutant
Standard Status Standard Status
9 ppm
(10 mg/m3)
20 ppm
(23 mg/m3)

0.030 ppm
(57 mg/m3)

0.18 ppm
(338 µg/m3)

0.07 ppm
9 ppm
(10 mg/m3)
35 ppm
(40 mg/m3)

0.053 ppm
(100 µg/m3)
8-Hour
1-Hour
Attainment
Attainment
Attainment
Attainment
Attainment
Unclassified
Carbon
Monoxide (CO)
Annual
Mean Attainment Nitrogen
Dioxide (NO2)
1-Hour
8-Hour
1-Hour
Attainment 0.100 ppm
Nonattainment 0.070 ppm
Nonattainment
Nonattainment
Not Applicable
Ozone
(O3)
(137 µg/m3)

0.09 ppm
(180 µg/m3)
Not Applicable
Suspended
Particulate
Matter (PM10)
Suspended
Particulate
Matter (PM2.5)
Annual
Mean
24-Hour
Annual
Mean
24-Hour
Annual
Mean
20 µg/m3
50 µg/m3
Nonattainment
Nonattainment
Nonattainment
Not Applicable
Not Applicable
Not Applicable
150 µg/m3
Not Applicable
Unclassified
12 µg/m Attainment 3 12 µg/m3
Not Applicable
Not Applicable
35 µg/m3
80 µg/m3
(0.03 ppm)
365 µg/m3
(0.14 ppm)

0.075 ppm
(196 µg/m3)
Nonattainment
Attainment
Sulfur Dioxide
(SO2)

0.04 ppm
(105 µg/m3)

0.25 ppm
24-Hour
1-Hour
Attainment
Attainment
Attainment
Attainment (655 µg/m3
)
Lead (Pb) is not listed in the above table because it has attained the NAAQS/CAAQS since the 1980s. ppm = parts per million, mg/m3 = milligrams per cubic meter, µg/m3 = micrograms per cubic meter Source: Bay Area Air Quality Management District, 2017. Air Quality Standards and Attainment Status. January 5.

Criteria Pollutant Concentrations
BAAQMD monitors air pollution at various sites within the airshed. The closest air monitoring station is approximately 2 miles northwest of the Town in the City of Redwood City (897 Barron 24

Ave). This station monitors O , CO, NO , and PM over the past 5 years (2018 through 2022). 3 2 2.5 The data shows over the past few years, the general plan area has exceeded the state and/or federal O3 and PM2.5 ambient air quality standards. Table 9 lists air quality trends in data collected for the past 5 years and published by the BAAQMD and CARB for the Redwood City monitoring location, which is the most recent time-period available. Note that some of these concentrations were influenced by smoke from wildfires.

Table 9. Ambient Air Quality Concentrations for Redwood City from 2018-2022 Pollutant Standard 2018 2019 2020 2021 2022
O3, Ozone
Max 1-hr concentration
No. days exceeded: CAAQS
Max 8-hr concentration
No. days exceeded: CAAQS
NAAQS
67 ppb 83 ppb 98 ppb 85 ppb 79 ppb
90 ppb 0 0 1 0 0
49 ppb 77 ppb 78 ppb 64 ppb 62 ppb
70 ppb
70 ppb
0 0
2 2
1 1
0 0
0 0
CO, Carbon Monoxide
Max 1-hr concentration
No. days exceeded: CAAQS
NAAQS
Max 8-hr concentration
No. days exceeded: CAAQS
NAAQS

2.5 ppm 2.0 ppm --
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
0 0
0 0
0 0

1.7 ppm 1.1 ppm
0 0
0 0
0 0
PM2.5
Max 24-hr concentration
No. days exceeded: NAAQS
Annual Concentration
No. days exceeded: CAAQS
NAAQS
120.9µg/m3 29.5 µg/m3 124.1 µg/m3 30.1 µg/m3 27.4 µg/m3 >35 µg/m3 13 0 9 0 0

10.3µg/m3 7.0µg/m3 9.8µg/m3 6.0µg/m3 6.8µg/m3
>12 µg/m3
>12 µg/m3
-
-
-
-
-
-
-
-
-
-
NO2, Nitrogen Dioxide
Max 1-hr concentration
No. days exceeded: CAAQS
NAAQS
77 ppb 55 ppb --
--
--
--
--
--
--
--
--

0.18 ppm

0.100 ppm
0 0
0 0
Note: Monitoring of CO and NO2 discontinued in 2020.

Source: Bay Area Air Quality Management District, Web: https://www.baaqmd.gov/about-air-quality/air-qualitymeasurement/air-quality-summaries.

California Air Resource Board, Web: https://arb.ca.gov/adam/select8/sc8start.php Ozone and PM2.5, are the major regional air pollutants of concern in the San Francisco Bay Area.

Elevated concentrations of PM10 and PM2.5 are the result of both region-wide (or cumulative) emissions and localized emissions. Understanding and controlling ozone and PM2.5 pollution is described in BAAQMD’s most recent Clean Air Plan.8 These descriptions are summarized below.

High ozone levels are caused by the cumulative emissions of ROG and NOX. Controlling the emissions of these precursor pollutants is the focus of BAAQMD’s attempts to reduce ozone levels. The highest ozone levels in the Bay Area occur in the eastern and southern inland valleys that are downwind of air pollutant sources. Ozone frequently forms on hot summer days when the prevailing seasonal northerly winds carry ozone precursors southward across the county. 8 Bay Area Air Quality Management District, 2017. Spare the Air Cool the Climate Final 2017 Clean Air Plan.

April. Web: https://www.baaqmd.gov/~/media/files/planning-and-research/plans/2017-clean-air-plan/attachment-a_- proposed-final-cap-vol-1-pdf.pdf?la=en
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Because emissions in one part of the region can impact air quality miles downwind, efforts to reduce ozone levels focus on reducing emissions of ROG and NOx throughout the region. The relationship between ROG and NOx in ozone formation is complex; the ratio between the precursor pollutants influences how ozone forms. BAAQMD’s ozone modeling indicates that the Bay Area is “ROG‐limited” for ozone formation. This means that reducing ROG emissions in the Bay Area will be more productive in reducing ozone, at least in the near term. However, modeling also suggests that large reductions in NOx emissions will be needed to achieve the ozone reductions required to attain the current health-based ozone standards. A certain amount of ozone formation occurs naturally, even in the absence of anthropogenic emissions of ROG and NOx.

PM2.5 concentrations are from direct and indirect emissions. Fossil fuel combustion and wood burning are the primary contributors of directly-emitted PM2.5. Formation of PM2.5 occurs in the atmosphere by complex chemical processes with precursors such as NOx, ammonia, and sulfur dioxide. According to BAAQMD, particulate matter concentrations vary considerably in composition and in spatial distribution both on a daily basis and on a seasonal basis in response to changes in weather and emissions. The Bay Area generally experiences its highest PM2.5 concentrations in the winter, with exceedances of the 24-hour standard mostly between November and February. High and very high PM2.5 episodes from wildfire smoke are typically regional in scale, affecting the area mostly in late summer and fall. On an annual average basis, PM2.5 levels in the Bay Area are relatively low.

With the exception of smoke from wildfires, the Bay Area currently meets PM2.5 standards, but has yet to attain the state annual and 24-hour standards for PM10. BAAQMD efforts to reduce PM2.5 and PM10 concentrations are focused on reducing woodburning, cooking emissions, and NOx emissions. BAAQMD, along with CARB and U.S. EPA have efforts to reduce particulate matter emissions from combustion engines associated with stationary and mobile sources.

Existing Sources of TACs and Sensitive Receptors
Atherton is primarily a residential area with no industries or substantial sources of air pollution.

Primary emission sources are traffic and diesel-powered locomotives using the CalTrain rail line.

The primary substantial roadway within the Town is El Camino Real. The CalTrain line services diesel-powered commuter trains and some freight trains. CalTrain is currently being modernized and will mostly serve electric-powered trains in the future; although some commuter trains and freight trains will still be powered by diesel.

There are groups of people more affected by air pollution than others. CARB has identified the following people who are most likely to be affected by air pollution: children under 16, the elderly over 65, athletes, and people with cardiovascular and chronic respiratory diseases. These groups are classified as sensitive receptors. Locations that may contain a high concentration of these sensitive population groups include residential areas, hospitals, daycare facilities, elder care facilities, and elementary schools. For cancer risk assessments, children are the most sensitive receptors, since they are more susceptible to cancer causing TACs. Residential locations are assumed to include infants and small children. Sensitive receptors in Atherton include residences, 26

schools and daycare facilities. The proposed Housing Element Update and resulting zoning code amendments would include new residential dwellings that are considered sensitive receptors.

The proposed lots and surrounding community are not considered to be in an overburdened community. According to CalEnviroScreen, the census tracts representative of the project sites and environs within 1,000 feet of the project have an overall percentile scores of 10th or less. Note that Oakwood Boulevard portion adjacent to Redwood City would be near the 40th percentile.

AIR QUALITY IMPACTS AND PROPOSED ZONE CODE AMENDMENT

POLICIES
Air pollutant emissions and associated health risks were predicted using emissions and dispersion models. The methodology for computing health risks impacts is contained in Appendix E of the BAAQMD CEQA Guidelines.9 The latest version of the California Emissions Estimator Model (CalEEMod) Version 2022 was used to compute annual emissions. The model output from CalEEMod along with inputs are included as Attachment 1.

Impact AIR-1: Conflict with or obstruct implementation of an applicable air quality plan?
BAAQMD, with assistance from Association of Bay Area Governments (ABAG) and the Metropolitan Transportation Commission (MTC), has prepared and implements specific plans to meet the applicable laws, regulations, and programs. The most recent and comprehensive of which is the Bay Area 2017 Clean Air Plan.
10 The BAAQMD has also developed CEQA guidelines to
assist lead agencies in evaluating the significance of air quality impacts. In formulating compliance strategies, BAAQMD relies on planned land uses established by local general plans. Land use planning affects vehicle travel, which in turn affects region-wide emissions of air pollutants and GHGs.

Consistency of the proposed Project with Clean Air Plan control measures is demonstrated by assessing whether the proposed zoning implements the applicable Clean Air Plan control measures. The 2017 Clean Air Plan includes control measures that are intended to reduce air pollutant emissions in the Bay Area either directly or indirectly. The control measures are divided into five categories that include:
• 40 measures to reduce stationary and area sources;
• 8 mobile source measures;
• 23 transportation control measures (including land use strategies); • 4 building sector measures;
• 2 energy sector measures;
• 4 agriculture sector measures;
• 3 natural and working lands measures;
• 4 waste sector measures;
9 BAAQMD, 2022. Appendix E of the BAAQMD CEQA Guidelines. April 2023. 10 Bay Area Air Quality Management District (BAAQMD), 2017. Final 2017 Clean Air Plan. 27

• 2 water sector measures; and
• 3 super-GHG pollutants measures.

In developing the control measures, BAAQMD identified the full range of tools and resources available, both regulatory and non-regulatory, to develop each one. This approach relies upon lead agencies to assist in implementing some of the control measures. A key tool for local agency implementation is the development of land use policies and implementing measures that address new development or redevelopment in local communities. To address this impact, the proposed Project’s effect on implementing the Clean Air Plan is evaluated based on consistency with Clean Air Planning projections (i.e., rate of increase in population versus vehicle travel).

Consistency with Clean Air Plan Projections
The BAAQMD, with assistance from ABAG and MTC, has prepared and implemented the Clean Air Plan to meet the applicable laws, regulations, and programs. The primary goals of the Clean Air Plan are to attain air quality standards, reduce population exposure and protect public health, and reduce GHG emissions and protect the climate. The BAAQMD has also developed CEQA guidelines to assist lead agencies in evaluating the significance of air quality impacts. In formulating compliance strategies, BAAQMD relies on planned land uses established by local general plans. Land use planning affects vehicle travel, which in turn affects region-wide emissions of air pollutants and GHG.

The BAAQMD CEQA Guidelines recommend comparing the increase in the rate of population compared to the rate of traffic increase that is based on vehicle miles travelled (VMT) or trips.

Table 10 provides population and traffic conditions for existing and future build out conditions with the Housing Element Update developed. The Housing Element Update identified 332 potential new single-family and 292 multi-family housing opportunities that could be developed.

This could increase the population by 2,048 people or 31 percent over existing conditions. Daily vehicle trips for this build out in housing were provided by the project traffic consultant. Using “Existing” as a baseline condition (estimated at 17,644 trips), daily trips attributable to the Project are anticipated to increase 29 percent at build-out with the Housing Element Update (22,750 trips).

The VMT per population is anticipated to decrease from 18.35 miles per capita to 17.99 miles with the Project. In summary, the Project increases population and traffic. The rate of increase in traffic, measured as the rate of trips or VMT, would be less than increase in population.

Table 10. Atherton Housing Element Update Traffic and Population Projections VMT per
Scenario Population Dwelling Units Daily Trips Population Existing Conditions
(Dept. of Finance 2023) 6,678
2,048
2,547 17,644
5,106

18.35 Single fam. 337
Multi Fam. 292 Year 2031 Additional --
2031 Conditions
2031 Project - Exist
8,726
+31%
22,750
+29%

17.99 -2%
Source: Project Description and Hexagon Transportation Consultants, per email from Adam Peterson (M Group), dated Nov. 20, 2023.
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