Los Altos City Council
June 23, 2026

Halsey House Project, SCH# 2025020308 108 Draft Environmental Impact Report City of Los Altos June 2026
Cumulative Impacts
Would the project result in a cumulatively considerable contribution to a cumulatively significant public services impact?
The geographic area for cumulative public services impacts is the City of Los Altos. The proposed project would not result in new residents or employees in Los Altos and, as a result, would have no impact on fire or police protection services, schools, parks, or other recreational facilities.

Therefore, the project would not result in a cumulatively considerable contribution to a cumulatively significant public services impact. (No Cumulative Impact)

Halsey House Project, SCH# 2025020308 109 Draft Environmental Impact Report City of Los Altos June 2026

4.16 Recreation

4.16.1 Environmental Setting
Regulatory Framework
Los Altos General Plan
The following policies in the City’s General Plan have been adopted for the purposes of avoiding or reducing recreation impacts and are applicable to the project:

Policy Description
OSCCF 1.4 Require park dedication, public open space, or require fees in lieu thereof, for all new subdivisions and multi-family residential development in Los Altos.

OSCCF 4.1 Provide adequate level of maintenance for City parks, open space, and public property to ensure safety, aesthetics, and recreational enjoyment for Los Altos residents.

Los Altos Parks Plan
The Los Altos Parks Plan, adopted in May of 2012, is intended to create a clear set of goals, policies, and objectives that will provide direction to the City Council and City staff for the development, improvement, and enhancement of the City’s park system for the next twenty to thirty years. The Parks Plan was designed to parallel the General Plan’s Open Space, Conservation, and Facilities Element by providing specific direction and recommendations related to parks in Los Altos.

Existing Conditions
The City of Los Altos’ Department of Recreation and Community Services is responsible for maintaining various parks and recreation facilities, as well as managing special interest programs and classes, senior programs, and community events. Overall, the City maintains a total of 19 parks, nature preserves, gyms, youth centers, and community centers that serve the community.

As described in Section 4.15 Public Services, nearby recreational facilities include the Preserve (which the Halsey House is in) and Shoup Park.

4.16.2 Impact Discussion
For the purpose of determining the significance of the project’s impact on recreation:
1) 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?
2) 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?

Halsey House Project, SCH# 2025020308 110 Draft Environmental Impact Report City of Los Altos June 2026
Project Impacts
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?
The project proposes to demolish the Halsey House, which is currently vacant and unused. The project would not generate new residents or employees and would not increase demand for local park and recreational facilities. For this reason, the proposed project would not result in the need for new or physically altered parks in the project area. (No Impact) 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? The demolition of the existing Halsey House would not require the construction or expansion of recreational facilities. The Preserve, where the Halsey House is located, would remain unchanged.

The project would not include new or expanded recreational facilities that would have an adverse physical effect on the environment. (No Impact)
Cumulative Impacts
Would the project result in a cumulatively considerable contribution to a cumulatively significant recreation impact?
The geographic area for cumulative park/recreational facility impacts is the City of Los Altos. The proposed project would demolish the Halsey House and would not include new residences. There would be no increase in park use such that physical deterioration would occur. Therefore, the project would have no cumulative impacts to recreational facilities. (No Cumulative Impact)

Halsey House Project, SCH# 2025020308 111 Draft Environmental Impact Report City of Los Altos June 2026

4.17 Transportation

4.17.1 Environmental Setting
Regulatory Framework
State
Senate Bill 743
SB 743 establishes criteria for determining the significance of transportation impacts using a vehicle miles traveled (VMT) metric intended to promote the reduction of GHG emissions, the development of multimodal transportation networks, and a diversity of land uses. Specifically, SB 743 requires analysis of VMT in determining the significance of transportation impacts. Local jurisdictions were required by OPR to implement a VMT policy by July 1, 2020.

SB 743 did not authorize OPR to set specific VMT impact thresholds, but it did direct OPR to develop guidelines for jurisdictions to utilize. CEQA Guidelines Section 15064.3(b)(1) describes factors that might indicate whether a development project’s VMT may be significant. Notably, projects located within 0.5 mile of transit should be considered to have a less than significant transportation impact based on OPR guidance.

Local
Los Altos General Plan
The following policies in the City’s General Plan have been adopted for the purpose of reducing or avoiding impacts related to transportation and traffic and are applicable to the proposed project.

Policy Description
CE 2.17 Maintain adequate emergency access for all land uses.

CE 2.20 Enhance driving safety in the community.

Los Altos Complete Streets Master Plan
The Complete Streets Master Plan (CSMP) was adopted in 2022 and is intended to build from the Bicycle and Pedestrian Master Plans that were previously adopted by the City. The CSMP provides recommendations and strategies for developing a comprehensive bicycle and pedestrian network that facilitates easy and safe circulation throughout the City. The CSMP outlines the existing conditions in the City, recommends improvements for the existing infrastructure, provides the Safe Routes to School Plan, and describes a strategy for evaluating and prioritizing suggested improvements.

Halsey House Project, SCH# 2025020308 112 Draft Environmental Impact Report City of Los Altos June 2026
Los Altos VMT Policy
SB 743 requires local jurisdictions to implement a VMT policy that can utilize analysis of VMT for proposed projects to determine the significance of transportation impacts. In February 2023, the Los Altos City Council adopted a VMT policy that establishes screening criteria to identify projects.

Existing Conditions
Roadway Network
Regional access to Los Altos is provided by SR 85 and I-280. Local access to the project site is provided by Foothill Expressway and University Avenue.

Bicycle Facilities
Bicycle facilities within the vicinity of the project site consist of separated bike lanes, bike routes, and bike lanes. These facilities are described in detail below. • Class III Bike Route60 along Lincoln Avenue and University Avenue between South El Monte Avenue and Fremont Road
• Class II Bicycle Lane along South San Antonio Road between Lincoln Avenue and El Camino Road
• A bike/pedestrian connector off University Avenue providing direct access to Shoup Park Pedestrian Facilities
Existing pedestrian facilities within the project vicinity include sidewalks and crosswalks. Sidewalks are present on University Avenue from South El Monte Avenue to Burke Road/Main Street.61 There is a pedestrian path off of University Avenue that provides direct access to the Preserve.

Transit Facilities
Existing bus transit service to the project area is provided by VTA and the City of Los Altos. VTA bus routes 40 and 52 serve the project area.62 Bus Route 40 provides service from Foothill College and Los Altos to the Mountain View Transit Center via Rengstorff Avenue and North Shoreline 60 A Class I classification is for multi-use paths that provide a completed separated right of way for the exclusive use of bicycles and pedestrians with cross flow minimized. A Class II classification is for bike lanes that provide a striped lane for one-way bike travel on a street or highway. A Class III classification includes bike route signed shared roadways that provide signage for bike routes on a roadway shared with motor vehicle traffic and pedestrian. Source: City of Los Altos. City of Los Altos Bicycle Transportation Plan. April 10, 2012. Page 3-15. 61 City of Los Altos. City of Los Altos Pedestrian Master Plan. August 2015. Page 3-14. 62 Valley Transportation Authority. “System Map.” October 30, 2023. Accessed December 19, 2025. https://www.vta.org/sites/default/files/2023-10/System-Map-103023.pdf.

Halsey House Project, SCH# 2025020308 113 Draft Environmental Impact Report City of Los Altos June 2026
Boulevard.
63 Bus Route 52 provides service from Foothill College and Los Altos to Mountain View Transit center via El Monte.
64 4.17.2 Impact Discussion
For the purpose of determining the significance of the project’s impact on transportation, would the project:
1) Conflict with a program, plan, ordinance or policy addressing the circulation system, including transit, roadways, bicycle lanes, and pedestrian facilities? 2) Conflict or be inconsistent with CEQA Guidelines Section 15064.3, subdivision (b)? 3) Substantially increase hazards due to a geometric design feature (e.g., sharp curves or dangerous intersections) or incompatible uses (e.g., farm equipment)? 4) Result in inadequate emergency access?
Project Impacts
a) Would the project conflict with a program, plan, ordinance, or policy addressing the circulation system, including transit, roadways, bicycle lanes, and pedestrian facilities? The project proposes to demolish the Halsey House. The project does not include construction of any buildings or structures. As such, the project would not generate any new trips. The roadway system, bicycle facilities, pedestrian facilities, and transit facilities would remain unchanged postdemolition of the Halsey House. Therefore, the project would have no impact on any program, plan, ordinance, or policy addressing the circulation system, including transit, roadways, bicycle lanes, and pedestrian facilities. (No Impact)
b) Would the project conflict or be inconsistent with CEQA Guidelines Section 15064.3, subdivision (b)?
The project would not be inconsistent with the CEQA Guidelines Section 15064.3 subdivision (b) because it would not generate any VMT.65 Therefore, the project would have no VMT impact. (No Impact)
63 Valley Transportation Authority. “40 Local Schematic Map.” Effective August 14, 2023. Accessed December 19, 2025. https://www.vta.org/go/routes/40.
64 Valley Transportation Authority. “52 Local Schematic Map.” Effective August 14, 2023. Accessed December 19, 2025. https://www.vta.org/go/routes/52.
65 The trucks traveling to and from the site during demolition would have VMT but travel for construction is temporary and not considered a source of permanent VMT.

Halsey House Project, SCH# 2025020308 114 Draft Environmental Impact Report City of Los Altos June 2026
c) Would the project substantially increase hazards due to a geometric design feature (e.g., sharp curves or dangerous intersections) or incompatible uses (e.g., farm equipment)? The project proposes to demolish the Halsey House. As discussed in Section 3.3 Project Description, the site can only be accessed via a pedestrian bridge that has an eight-ton weight capacity and 10- foot width constraint. An analysis completed by a structural engineer in December 2025, which included inspections of the bridge and a load rating assessment, determined that the bridge is in good condition and confirmed the eight-ton weight limit.66 The service utility trucks and track loaders used for demolition would weigh a maximum of seven tons. Additionally, other equipment used for demolition activities would be small and lightweight, consisting primarily of hand tools. As such, no hazards would be created during demolition activities.

Further, the proposed project does not include construction of any buildings or structures. As discussed in checklist question a), the project would not include any roadway features, bike facilities, or pedestrian facilities. There would also be no new trips generated by the project, other than temporary trips during the demolition period. For these reasons, there would be no impacts related to geometric design features or incompatible uses. (No Impact) d) Would the project result in inadequate emergency access? The project would also not hinder or block existing roadways used for emergency access during demolition. All construction staging would occur within the project site (refer to Figure 3.1-3) for the site disturbance area). For these reasons, the project would have no impact on emergency access. (No Impact)
Cumulative Impacts
Would the project result in a cumulatively considerable contribution to a cumulatively significant transportation impact?
The geographic area for transportation impacts is the City of Los Altos. As discussed under checklist question a), the project would not be inconsistent with plans and policies addressing the circulation system, including transit, roadways, bicycle lanes, and pedestrian facilities since no trips would be generated by the project. As discussed under checklist question b), the project would not generate any VMT; therefore, the project would not contribute to cumulative VMT in the region. As a result, the project would not result in a cumulatively considerable contribution to cumulative impacts in these areas. Additionally, the project would not create any transportation-related hazards or result in inadequate emergency access. For these reasons, the proposed project would not result in a cumulatively considerable contribution to a significant cumulative transportation impact. (No Cumulative Impact)
66 CSG Consultants, Inc. Halsey House Bridge Crossing Structural Assessment Memorandum. December 2025.

Halsey House Project, SCH# 2025020308 115 Draft Environmental Impact Report City of Los Altos June 2026

4.18 Tribal Cultural Resources

4.18.1 Environmental Setting
Assembly Bill 52
AB 52, effective July 2015, established a new category of resources for consideration by public agencies called Tribal Cultural Resources (TCRs). AB 52 requires lead agencies to provide notice of projects to tribes that are traditionally and culturally affiliated with the geographic area if they have requested to be notified. Where a project may have a significant impact on a TCR, consultation is required until the parties agree to measures to mitigate or avoid a significant effect on a TCR or until it is concluded that mutual agreement cannot be reached.

Under AB 52, TCRs are defined as follows:
• Sites, features, places, cultural landscapes, sacred places, and objects with cultural value to a California Native American tribe that are also either:
o Included or determined to be eligible for inclusion in the California Register of Historic Resources, or
o Included in a local register of historical resources as defined in Public Resources Code Section 5020.1(k).
• A resource determined by the lead agency to be a TCR.

Existing Conditions
There are no known TCRs on the project site. As discussed in Section 4.5 Cultural Resources, the project site is potentially sensitive for archaeological resources due to its proximity to Adobe Creek.

4.18.2 Impact Discussion
For the purpose of determining the significance of the project’s impact on tribal cultural resources, 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:
1) 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)? 2) 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 Resources Code Section 5024.1, the lead agency shall consider the significance of the resource to a California Native American tribe.

Halsey House Project, SCH# 2025020308 116 Draft Environmental Impact Report City of Los Altos June 2026
Project Impacts
a) Would the project cause a substantial adverse change in the significance of a tribal cultural resource that is 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)?
As discussed in Section 4.5 Cultural Resources, a Sacred Lands File Search was conducted through the NAHC for the project site on March 1, 2024 and the search results were negative per a response received March 4, 2024. The City has provided notice of the proposed project to culturally affiliated tribes in August, 2024. No responses were received. Therefore, there are no known TCRs on-site.

Also as discussed in Section 4.5 Cultural Resources, the proposed project would be required to implement a Standard Condition of Approval to address any accidental disturbance of unknown cultural resources and set forth the appropriate procedure to be followed in the event of discovery and would reduce impacts to unrecorded subsurface cultural resources. Therefore, the proposed project would not cause a substantial adverse change in the significance of a tribal cultural resource that is listed on local or state registers. (Less than Significant Impact) b) Would the project cause a substantial adverse change in the significance of a tribal cultural resource that is 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?
As discussed above under checklist question a), there are no known TCRs on-site and the project as proposed would not result in significant impacts to TCRs. (Less than Significant Impact) Cumulative Impacts
Would the project result in a cumulatively considerable contribution to a cumulatively significant tribal cultural resources impact?
The geographic study area for cumulative impacts to tribal cultural resources is the surrounding area. The cumulative projects listed in Table 4.0-1 may require excavation and grading or other activities that may affect tribal cultural resources. No cultural resources were identified in the project area; however, the project site is considered potentially sensitive for archaeological resources due to its proximity to Adobe Creek. The project and other cumulative projects would be required to implement Standard Conditions of Approval or mitigation measures that would avoid impacts and/or reduce them to a less than significant level consistent with CEQA and AB 52 requirements. These projects would also be subject to the federal, state, and county laws regulating archaeological resources and human remains. Therefore, the project in combination with other

Halsey House Project, SCH# 2025020308 117 Draft Environmental Impact Report City of Los Altos June 2026
cumulative projects would not result in a significant cumulative tribal cultural resources impact. (Less than Significant Cumulative Impact)

Halsey House Project, SCH# 2025020308 118 Draft Environmental Impact Report City of Los Altos June 2026

4.19 Utilities and Service Systems

4.19.1 Environmental Setting
Regulatory Framework
State
State Water Code
Pursuant to the State Water Code, water suppliers providing water for municipal purposes to more than 3,000 customers or supplying more than 3,000 acre-feet (approximately 980 million gallons) of water annually must prepare and adopt an urban water management plan (UWMP) and update it every five years. As part of an UWMP, water agencies are required to evaluate and describe their water resource supplies and projected needs over a 20-year planning horizon, water conservation, water service reliability, water recycling, opportunities for water transfers, and contingency plans for drought events. California Water Service adopted its most recent UWMP for the Los Altos Suburban District in June 2021. 67
Assembly Bill 939
The California Integrated Waste Management Act of 1989, or AB 939, established the Integrated Waste Management Board, required the implementation of integrated waste management plans, and mandated that local jurisdictions divert at least 50 percent of solid waste generated (from 1990 levels), beginning January 1, 2000, and divert at least 75 percent by 2010. Projects that would have an adverse effect on waste diversion goals are required to include waste diversion mitigation measures.

Regional and Local
Countywide Integrated Waste Management Plan
Pursuant to AB 939, solid waste facility compliance requires that each county prepare and adopt a Countywide Integrated Waste Management Plan. The Santa Clara County Integrated Waste Management Plan (CIWMP) was approved in 1996 and contains goals, policies, and objectives aimed to ensure an effective and efficient integrated waste management system. Public Resources Code Sections 41770 and 41822, and Title 24, California Code of Regulations Section 18788 require that each countywide or regional agency integrated waste management plan, and elements thereof, be reviewed, revised (if necessary), and submitted to CalRecycle every five years. The last review was completed in 2021 and concluded that despite population growth, solid waste diversion 67 California Water Service. 2020 Urban Water Management Plan, Los Altos Suburban District. June 2021. https://www.calwater.com/docs/uwmp2020/LAS_2020_UWMP_FINAL.pdf

Halsey House Project, SCH# 2025020308 119 Draft Environmental Impact Report City of Los Altos June 2026
has increased, Santa Clara County has adequate disposal capacity (i.e., greater than 15 years), and no revisions to the CIWMP are warranted.68
Los Altos General Plan
The following policies in the City’s General Plan have been adopted for the purpose of avoiding or reducing impacts on utilities and service systems and are applicable to the project:

Policy Description
IWD 4.1 Continue to work with infrastructure providers to ensure the community’s current and future infrastructure needs are met.

IWD 4.3 Maintain accurate records of infrastructure usage and needed infrastructure improvements.

Los Altos Municipal Code
Chapter 6.14 of the LAMC details the City’s requirements for disposing of solid waste that is generated during the demolition of existing structures and the construction of new buildings in the City. Projects that are valued at $25,000 or more must divert at least 65 percent of the construction and demolition debris associated with the project from landfills in order to help the City achieve their overall waste diversion goal of 78 percent.

Existing Conditions
Water Supply
The project site is served by the California Water Service (Cal Water) and is located within Cal Water’s Los Altos Suburban (LAS) District. Water supply for the project site is sourced from a combination of groundwater and purchased water. Approximately 21 percent of the LAS District’s provided water comes from primary groundwater production and 79 percent comes from water purchases from the Valley Water, sourced from underground aquifers, reservoirs, and the San Joaquin-Sacramento River Delta. The LAS District system includes 297 miles of mains, 65 booster pumps, and 46 storage tanks.69 The LAS District 2020 UWMP found that Cal Water has more than sufficient well capacity to meet the demands unserved by Valley Water purchases through 2045.

Sanitary Sewer/Wastewater Treatment
The City of Los Altos’ Department of Public Works is responsible for the wastewater collection system within the City. Wastewater is conveyed to the Palo Alto Regional Water Pollution Control Plant (PARWQCP) for treatment and disposal. The PARWQCP serves the wastewater management 68 California Department of Resources Recycling and Recovery. “Five-Year Countywide or Regional Agency Integrated Waste Management Plan Review Report Guidelines.” Accessed December 19, 2025. https://calrecycle.ca.gov/lgcentral/library/policy/5yrreview/. 69 California Water Service. 2020 Urban Water Management Plan, Los Altos Suburban District. June 2021. https://www.calwater.com/docs/uwmp2020/LAS_2020_UWMP_FINAL.pdf.

Halsey House Project, SCH# 2025020308 120 Draft Environmental Impact Report City of Los Altos June 2026
needs of the communities of Palo Alto, Los Altos, Mountain View, East Palo Alto, Los Altos Hills, Stanford University, and East Palo Alto Sanitary District. The City owns and maintains the collection system within the City and its sphere of influence and the trunk sewer that connects the City to the PARWQCP master metering station.70
The PARWQCP has an annual treatment capacity of 39 million gallons per day (mgd), with the municipalities of Los Altos, Mountain View, and Los Altos Hills estimated to generate 4,045 acrefeet per year, or 3.6 mgd of the plant’s treatment capacity (nine percent). The PARWQCP currently receives approximately 17 mgd from all its customers.71 The PARWQCP, therefore, has approximately 22 mgd of treatment capacity available.

Storm Drainage
Runoff from the project site drains as sheet flow to Adobe Creek. Adobe Creek flows to San Francisco Bay.72
Solid Waste
Solid waste collection in the City of Los Altos is provided by Mission Trail Waste Systems. Mission Trail Waste Systems provides residential, commercial, and industrial collection services for garbage, recycling, and organics for the City. Mission Trail Waste Systems operates a transfer station at 1313 Memorex Drive in Santa Clara. Solid waste generated in the City is disposed of at Newby Island Sanitary Landfill (NISL) in the City of San José. As of May 2023, Newby Island Landfill had approximately 12.4 million cubic yards of capacity remaining and an estimated closure year of 2035.73

4.19.2 Impact Discussion
For the purpose of determining the significance of the project’s impact on utilities and service systems, would the project:
1) Require or result in the relocation or construction of new or expanded water, wastewater treatment or stormwater drainage, electric power, natural gas, or telecommunications facilities, the construction or relocation of which could cause significant environmental effects?
2) Have insufficient water supplies available to serve the project and reasonably foreseeable future development during normal, dry and multiple dry years? 70 City of Los Altos. “Public Works – Sanitary Sewer.” Accessed December 19, 2025. https://www.losaltosca.gov/432/Sanitary-Sewer.
71 California Water Service. 2020 Urban Water Management Plan, Los Altos Suburban District. June 2021. https://www.calwater.com/docs/uwmp2020/LAS_2020_UWMP_FINAL.pdf 72 City of Los Altos. “Stormwater Master Plan – Appendix A: Drainage Basins.” Accessed December 19, 2025. https://www.losaltosca.gov/441/Stormwater-Master-Plan.
73 Boccaleoni, Anthony. Environmental Manager, Republic Services, Inc. Personal Communication. May 12, 2023.

Halsey House Project, SCH# 2025020308 121 Draft Environmental Impact Report City of Los Altos June 2026
3) Result in a determination by the wastewater treatment provider which serves or may serve the project that it does not have adequate capacity to serve the project’s projected demand in addition to the provider’s existing commitments?
4) 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? 5) Be noncompliant with federal, state, or local management and reduction statutes and regulations related to solid waste?
Project Impacts
a) Would the project require or result in the relocation or construction of new or expanded water, wastewater treatment or stormwater drainage, electric power, natural gas, or telecommunications facilities, the construction or relocation of which could cause significant environmental effects?
The project would demolish the Halsey House and would not construct any new structures. The site would be vacant post-demolition. Since no new structures would be constructed on-site, there would be no new connections to the City’s water, wastewater treatment or stormwater drainage, electric power, natural gas, or telecommunications facilities. As a result, there would be no need for relocation, expansion, or construction of these facilities that could cause significant environmental effects. (No Impact)
b) Would the project have insufficient water supplies available to serve the project and reasonably foreseeable future development during normal, dry and multiple dry years? The project would not construct a building or have operational activities that would require water or increase water demand. For these reasons, the proposed project would have no impact related to water supplies. (No Impact)
c) Would the project result in a determination by the wastewater treatment provider which serves or may serve the project that it does not have adequate capacity to serve the project’s projected demand in addition to the provider’s existing commitments? The project would not construct a building or have operational activities that would generate wastewater. For this reason, the project would have no impact related to wastewater generation in excess of the wastewater treatment provider’s capacity. (No Impact)

Halsey House Project, SCH# 2025020308 122 Draft Environmental Impact Report City of Los Altos June 2026
d) Would the project 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?
The project would not construct a building or have operational activities that would generate solid waste. However, demolition of the existing building would result in debris that would need to be hauled to an appropriate off-site disposal location. The project would comply with Chapter 6.14 of the LAMC requiring that at least 65 percent of demolition debris be diverted from landfills. For this reason, the project would have no impact related to solid waste generation in excess of state or local standards. (No Impact)
e) Would the project be noncompliant with federal, state, or local management and reduction statutes and regulations related to solid waste?
As mentioned under checklist question d), the project would not generate any operational solid waste since it is limited to the demolition of Halsey House. Demolition debris would be hauled to an appropriate off-site disposal location, and 65 percent of debris would be diverted from landfills, as required by Chapter 6.14 of the LAMC. Therefore, the project would not conflict or be out of compliance with federal, state, or local management and reduction statutes and regulations related to solid waste because these regulations would not be applicable. There would be no impact. (No Impact)
Cumulative Impacts
Would the project result in a cumulatively considerable contribution to a cumulatively significant utilities and service systems impact?
The geographic area for cumulative water supply, wastewater, and storm drainage systems is the City boundaries. The geographic area for electricity, natural gas, and telecommunication services is the State of California. As discussed above, the project would not have any impact on utility and service systems since the project would not connect to existing or create new utility infrastructure.

The project would also not increase water usage or result in an incremental increase in wastewater or solid waste generation since no operational activities are proposed at the site. Therefore, the project would not result in a cumulatively considerable contribution to a significant utilities and service systems impact. (No Cumulative Impact)

Halsey House Project, SCH# 2025020308 123 Draft Environmental Impact Report City of Los Altos June 2026

4.20 Wildfire

4.20.1 Environmental Setting
Regulatory Framework
Fire Hazard Severity Zones
CAL FIRE is required by law to map areas of significant fire hazards based on fuels, terrain, weather, and other relevant factors. Referred to as FHSZs, these maps influence how people construct buildings and protect property to reduce risk associated with wildland fires. FHSZs are divided into areas where the state has financial responsibility for wildland fire protection, known as SRAs, and areas where local governments have financial responsibility for wildland fire protection, known as LRA). Homeowners living in an SRA are responsible for ensuring that their property is in compliance with California’s building and fire codes. Only lands zoned for very high fire hazard are identified within LRAs.

Existing Conditions
The project site is in an urban area surrounded by existing development. The project site is not located near wildlands that could present a fire hazard. The site is not located within an identified Very High Fire Hazard Severity Zone in an SRA or a LRA.74

4.20.2 Impact Discussion
For the purpose of determining the significance of the project’s impact on wildfire, if located in or near state responsibility areas or lands classified as very high fire hazard severity zones, would the project:
1) Substantially impair an adopted emergency response plan or emergency evacuation plan? 2) 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?
3) 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? 4) 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? 74 California Department of Forestry and Fire Protection. “Fire Hazard Severity Zones.” Accessed December 19, 2025. https://osfm.fire.ca.gov/what-we-do/community-wildfire-preparedness-and-mitigation/fire-hazard-severityzones.

Halsey House Project, SCH# 2025020308 124 Draft Environmental Impact Report City of Los Altos June 2026
Project Impacts
The project site is not located in or near state responsibility areas or lands classified as very high fire hazard severity zones; therefore, the project would not result in wildfire impacts. (No Impact) Cumulative Impacts
The project site is not located in or near state responsibility areas or lands classified as very high fire hazard severity zones; therefore, the project would not result in cumulative wildfire impacts. (No Cumulative Impact)

Halsey House Project, SCH# 2025020308 125 Draft Environmental Impact Report City of Los Altos June 2026
Section 5.0 Growth-Inducing Impacts
Would the project foster or stimulate significant economic or population growth in the surrounding environment?
The CEQA Guidelines require that an EIR identify the likelihood that a proposed project could “foster economic or population growth, or the construction of additional housing, either directly or indirectly, in the surrounding environment” (Section 15126.2[d]). This section of the EIR is intended to evaluate the impacts of such growth in the surrounding environment.

The project consists of demolition of an existing vacant structure with no new development proposed. Therefore, the project would not result in direct population growth, or in indirect growth due to new employment opportunities. The project would not remove any obstacles that would help facilitate additional growth that could significantly affect the physical environment, nor would it include the expansion of existing infrastructure that would facilitate growth in the project area or other areas of the City. Therefore, the project would not result in growth-inducing impacts beyond what was envisioned in the City’s General Plan. (No Impact)

Halsey House Project, SCH# 2025020308 126 Draft Environmental Impact Report City of Los Altos June 2026
Section 6.0 Significant and Irreversible
Environmental Changes
Pursuant to CEQA Guidelines Section 15126.2(d), an EIR must identify significant irreversible environmental changes that would be caused by the proposed project being analyzed. Significant irreversible changes include the 1) irreversible use of nonrenewable resources, 2) commitment of future generations to similar use, and 3) irreversible damage resulting from environmental accidents associated with the project.

6.1 Irreversible Use of Nonrenewable Resources
Demolition of the Halsey House would require the use of nonrenewable resources and energy during the operation of demolition equipment and trucks. As described in Section 4.6 Energy under checklist question a), the project would minimize the use of nonrenewable resources like diesel fuel to be efficient, and would not use fuel wastefully due to expenses associated with demolition equipment. Also, the project site is within an urban area of Los Altos and can be easily accessed via roadways. The project would not have any operational phases that would consume energy. For these reasons, the project would minimize the use of nonrenewable resources.

6.2 Commitment of Future Generations to Similar Use
Demolition of the Halsey House would not commit resources to prepare the site or construct and operate a building. Removal of the existing structure would leave the site vacant. The proposed demolition would not result in other land use changes in the surrounding area. For these reasons, the project would not commit future generations to changes in land use.

6.3 Irreversible Damage Resulting from Environmental
Accidents Associated with the Project
The project does not propose hazardous uses, and environmental accidents would not occur since no operation is proposed. As discussed in Section 4.9 Hazards and Hazardous Materials, there are no significant unmitigable hazards and hazardous materials conditions on-site or off-site that would substantially affect the public and surrounding environment. As described in Section 4.7 Geology and Soils, there are no significant unmitigable geology and soils impacts which would result from implementation of the project. For these reasons, the project would not result in irreversible damage that may result from environmental accidents.

Halsey House Project, SCH# 2025020308 127 Draft Environmental Impact Report City of Los Altos June 2026
Section 7.0 Significant and Unavoidable
Impacts
A significant unavoidable impact is an impact that cannot be mitigated to a less than significant level if the project is implemented as it is proposed. The following significant and unavoidable impacts have been identified as resulting from the project:
• Impact CUL-1: Implementation of the proposed project would result in the demolition of the Halsey House, which is a historic resource.

Halsey House Project, SCH# 2025020308 128 Draft Environmental Impact Report City of Los Altos June 2026
Section 8.0 Alternatives
CEQA requires that an EIR identify and evaluate alternatives to a project as it is proposed. Two key provisions from the CEQA Guidelines pertaining to the discussion of alternatives are provided below:

Section 15126.6(a). Consideration and Discussion of Alternatives to the Proposed Project.

An EIR shall describe a range of reasonable alternatives to the project, or to the location of the project, which would feasibly attain most of the basic objectives of the project but would avoid or substantially lessen any of the significant effects of the project and evaluate the comparative merits of the alternatives. An EIR need not consider every conceivable alternative to a project. Rather, it must consider a reasonable range of potentially feasible alternatives that will foster informed decision making and public participation. An EIR is not required to consider alternatives which are infeasible. The lead agency is responsible for selecting a range of project alternatives for examination and must publicly disclose its reasoning for selecting those alternatives. There is no ironclad rule governing the nature or scope of the alternatives to be discussed other than the rule of reason.

Section 15126.6(b). Purpose. Because an EIR must identify ways to mitigate or avoid the significant effects that a project may have on the environment (Public Resources Code Section 21002.1), the discussion of alternatives shall focus on alternatives to the project or its location which are capable of avoiding or substantially lessening any significant effects of the project, even if those alternatives would impede to some degree the attainment of the project objectives, or be more costly.

Other elements of the Guidelines discuss that alternatives should include enough information to allow a meaningful evaluation and comparison with the proposed project. The CEQA Guidelines state that if an alternative would cause one or more additional impacts, compared to the proposed project, the discussion should identify the additional impact, but in less detail than the significant effects of the proposed project. The CEQA Guidelines emphasize a commonsense approach – the alternatives should be reasonable, “foster informed decision making and public participation,” and focus on alternatives that avoid or substantially lessen the significant impacts. CEQA requires a range of alternatives necessary to permit a reasoned choice.

The three critical factors to consider in selecting and evaluating alternatives are, therefore: (1) the significant impacts from the proposed project which could be reduced or avoided by an alternative, (2) the project objectives, and (3) the feasibility of the alternatives available. These factors are discussed below. The following discussion is based, in part, on Relocation Feasibility Study prepared in July 2024 by Page & Turnbull and a Feasibility Study prepared in July 2021 by Architectural Resources Group.

Halsey House Project, SCH# 2025020308 129 Draft Environmental Impact Report City of Los Altos June 2026

8.1 Factors in Selecting Alternatives

8.1.1 Significant Impacts of the Project
As explained above, the CEQA Guidelines Section 15126.6 states that the alternatives analysis in an EIR should be limited to alternatives that are feasible and would avoid or substantially lessen any of the significant effects of the project and achieve most of the basic project objectives. Potentially significant environmental impacts that would result from the proposed project are evaluated in Section 4.0 Environmental Setting, Impacts, and Mitigation of this EIR. As discussed throughout this EIR, with implementation of mitigation measures and standard conditions of approval, many of the potentially significant impacts resulting from the project would be reduced to a less-than-significant level.

Impacts that would be mitigated to less than significant levels are summarized below. • Impact BIO-1: Disturbance of the existing woodrat nests on-site could result in the destruction of nests and injury or mortality of individual woodrats. • Impact BIO-2: Demolition of the structure on-site would disturb Townsend’s big-eared bats roosting within the structure.
• Impact HAZ-1: Demolition of the existing building could expose construction workers or residents in the vicinity of the project site to harmful levels of ACMs or LBPs.

The following impact would remain significant and unavoidable with all feasible mitigation implemented.
• Impact CUL-1: Implementation of the proposed project would result in the demolition of the Halsey House, which is a historic resource.

8.1.2 Project Objectives
While CEQA does not require that alternatives must be capable of meeting all of the project objectives, their ability to meet most of the basic objectives is considered relevant to their consideration.

As identified in Section 3.4 Project Objectives, the objectives for the project are as follows:

1. Protect the health, safety, and welfare of the surrounding community by eliminating safety hazards associated with the Halsey House building, which is currently vacant and in a state of disrepair.

2. Maintain and improve public open space at the project site through restoration of landscaped areas and enhanced open space accessibility and visibility.

3. Reduce or eliminate ongoing maintenance costs associated with an unused public facility.

Halsey House Project, SCH# 2025020308 130 Draft Environmental Impact Report City of Los Altos June 2026

4. Reduce or eliminate the cost to rehabilitate the existing structure to a usable condition.

5. Comply with the Secretary of the Interior’s Standards as necessary.

8.2 Project Alternatives
The City considered the following alternatives to the proposed project:
• No Project Alternative
• Preservation Alternative 1 – Relocation of Historic Resource Off-Site • Preservation Alternative 2 – Full Rehabilitation of Historic Resource • Preservation Alternative 3 – Partial Rehabilitation/Partial Demolition • Preservation Alternative 4 – Mothballing

8.2.1 Feasibility of Alternatives
CEQA, the CEQA Guidelines, and case law interpreting CEQA and the CEQA Guidelines have found that feasibility can be based on a wide range of factors and influences. The CEQA Guidelines state that such factors can include (but are not necessarily limited to) the suitability of an alternate site, economic viability, availability of infrastructure, consistency with a general plan or with other plans or regulatory limitations, jurisdictional boundaries, and whether the project proponent can “reasonably acquire, control or otherwise have access to the alternative site (Section 15126.6[f][1]).”

8.2.2 Project Alternatives Evaluated
In addition to a “No Project” alternative, the CEQA Guidelines advise that the range of alternatives discussed in the EIR should be limited to those that “would avoid or substantially lessen any of the significant effects of the project” (Section 15126.6[f]). The discussion below addresses alternatives which could reduce project impacts and are feasible from a physical land use and infrastructure perspective. This Draft EIR does not evaluate the financial or economic feasibility of the alternatives presented.

No Project Alternative
The CEQA Guidelines [§15126(d)4] require that an EIR specifically discuss a “No Project” alternative, which shall address both “the existing conditions, as well as what would be reasonably expected to occur in the foreseeable future if the project is not approved, based on current plans and consistent with available infrastructure and community services.” The No Project Alternative would retain the existing Halsey House as-is.

Comparison of Environmental Impacts
The No Project Alternative would avoid the project’s mitigated and significant and unavoidable impacts because it would not change existing conditions.

Halsey House Project, SCH# 2025020308 131 Draft Environmental Impact Report City of Los Altos June 2026
Relationship to Project Objectives
The No Project Alternative would not meet any of the project objectives. The Halsey House would remain a health and safety issue, and the City would continue to spend funds to maintain an unused public facility.

Conclusion
The No Project Alternative would avoid the project’s impacts but would not meet any of the project’s objectives.

Preservation Alternative 1 – Relocation of the Historic Resource Off-Site Under Preservation Alternative 1, the historic resource would be relocated to another location offsite. There would be no demolition of the Halsey House.

Historic buildings can be relocated in many circumstances, depending on structural condition, building materials, location, and the availability and suitability of a receiver site. A relocation feasibility study was prepared by Page & Turnbull (with a structural evaluation prepared by T&S Structural) in July 2024 (refer to Appendix G) to assess the feasibility and impact of relocating the Halsey House.

The most challenging aspect of relocation would be finding a suitable transportation route. Three routes were analyzed with the main constraint identified being the narrowness of the roadways available in relation to the geometry of the building. The three possible routes for relocation off-site would be (1) the main entrance to the Preserve; (2) the trail out of the Preserve onto Manresa Way, which is a private road; or (3) through an existing fence onto Manresa Way via Manresa Lane, which is also a private road. The possible routes would require the Halsey House to be divided into 14 or more sections for relocation and reassembly.75
The first route option through the main entrance of the Preserve is limited because of the width and load capacity of the existing bridge over Adobe Creek, and the mature redwoods on either side of the route. This route would only accommodate a maximum section width of 14 feet and six inches. Some of the mature redwood trees may need to be cleared to accommodate the trucks transporting pieces of the Halsey House. In addition, if the residence were cut into the 14 or more sections necessary to accommodate the route width, each section would weigh approximately eight tons, and the necessary shoring beams and power dollies required for the move would add an additional seven tons of weight for a total load of approximately 15 tons. The load capacity of the existing bridge is approximately eight tons; therefore, a temporary bridge over the existing bridge would be required to accommodate the load of each section of the residence.

The second route option would require trimming and selective removal of the existing native plantings and mature trees along the trail and at key intersections, but overall could accommodate 75 Page & Turnbull. Halsey House Relocation Feasibility Study. July 15, 2024. Page 5.

Halsey House Project, SCH# 2025020308 132 Draft Environmental Impact Report City of Los Altos June 2026
wider sections of up to 19 feet if the existing median features at the intersection of Manresa Way and University Ave were removed.

Finally, the third route option is limited by the width of the existing private community gates, which are substantial masonry structures, and would require transported sections to be no more than 50 feet wide.

Comparison of Environmental Impacts
The first route option described above would require construction of a temporary bridge to allow for larger width and load capacities. Based on the proximity of mature redwoods to the existing bridge, a temporary bridge large enough to accommodate the relocation would require removal of several mature redwoods.

Both the second and third options would require coordination with and approval from the gated community in addition to the typical local jurisdictional coordination, particularly for removal and trimming of site features along the route. Under all three options, relocation of the Halsey House would result in similar biological impacts as the proposed project, including removal of mature redwood trees, vegetation clearing, disturbance of woodrat nests, and potential indirect impacts on water quality. Mitigation measures MM BIO-1.1 through MM BIO-1.3 and MM BIO-2.1 identified for the proposed project would still need to be implemented to reduce these impacts to a less than significant level.

Further, the Halsey House is intrinsicality linked with the Preserve due to the events associated with Emma Wright Halsey, Mori, and Yoshio. Moving the Halsey House would diminish its ties to the location and it would no longer be directly associated with the development of the park. Relocation of the Halsey House would also potentially compromise the setting and feeling associated with the residence as it is currently located in a secluded woodsy area away from the main throughfares, situated along Adobe Creek, and surrounded by redwood trees. A potential receiver site would need to have a comparable feeling and setting to the current site, which would include the natural setting (e.g., mature redwood and oak trees) and semi-rural feeling adjacent to a waterway. A receiver site would also need to replicate similar building setbacks (e.g., 200 feet or more) and relationship to the public right of way (e.g., orientation and distance). The City of Los Altos does not own a receiver site that could provide a similar setting and feeling as the Preserve. While Preservation Alternative 1 would avoid demolition of the Halsey House, moving it would diminish four of the seven aspects of the Halsey House’s integrity including location, setting, feeling, and association. The loss of these aspects would result in a loss of historic integrity of the structure and, as such, would result in a significant unavoidable impact under CEQA.

The relocation feasibility study prepared by Page & Turnbull determined that while the Halsey House is an acceptable candidate for relocation since it retains structural integrity, relocation of the

Halsey House Project, SCH# 2025020308 133 Draft Environmental Impact Report City of Los Altos June 2026
existing building to an alternative location would encounter transportation route constraints and would result in the loss of integrity of setting and association, as explained above.76 Since Preservation Alternative 1 does not propose demolition of the Halsey House, construction workers and residents would not be potentially exposed to ACMs or LBPs, and mitigation measures MM HAZ-1.1 through MM HAZ-1.3 would not be needed.

Preservation Alternative 1 would require structural upgrades for conformance with current CBC standards, including ADA accessibility, fire access, and protection of the structure against liquefaction. The City would coordinate with the Fire District to ensure the alternative implements adequate fire access and design standards (e.g., sprinklers). Preservation Alternative 1 would comply with the recommendations identified in the site-specific Geotechnical Investigation.

Relationship to Project Objectives
Preservation Alternative 1 would meet some, but not all, of the project objectives. Assuming the Halsey House is relocated in a manner that eliminates the safety hazards associated with the structure’s current condition through implementation of required structural upgrades, this alternative would meet the objecting of protecting the health, safety, and welfare of the surrounding community by eliminating safety hazards associated with the Halsey House building, which is currently vacant and in a state of disrepair. Additionally, relocating the Halsey House would meet the objective of maintaining and improving public open space at the project site through restoration of landscaped areas and enhanced open space accessibility and visibility. However, this alternative would not adhere to the Secretary of the Interior’s Standards for Rehabilitation and Guidelines for Rehabilitating Historic Buildings because the relocation would affect the historic integrity of the structure. This alternative would also require continued financing to maintain the Halsey House after relocation; thus, this alternative would not reduce or eliminate maintenance costs.

Conclusion
Relocation of the Halsey House would preserve the building instead of demolishing it, which would result in lesser impacts than the proposed project. However, the historic impact would not be reduced to a less than significant level because relocation of the Halsey House would result in a loss of integrity and association. Additionally, relocation of the Halsey House would be infeasible to implement without resulting in undesirable impacts to the Preserve.

Preservation Alternative 2 – Full Rehabilitation of Historic Resource Under Preservation Alternative 2, the historic resource would be retained on-site and fully rehabilitated. There would be no demolition of the Halsey House. 76 Page & Turnbull. Halsey House Relocation Feasibility Study. July 15, 2024. Page 17.

Halsey House Project, SCH# 2025020308 134 Draft Environmental Impact Report City of Los Altos June 2026
Comparison of Environmental Impacts
Preservation Alternative 2 would avoid the project’s significant and unavoidable impacts because a historic resource would not be demolished. The full rehabilitation of the Halsey House would have similar air quality fugitive dust impacts if heavy-duty construction equipment or trucks, which can kick up dust while traveling on exposed pervious surfaces, are required. Implementation of Standard Conditions of Approval to reduce generation of fugitive dust would be required of this alternative.

Rehabilitation of the Halsey House would require exterior and interior work over an approximately 12-month construction period. Exterior work would include grading, provision of new walkways and pathways for accessibility around the building perimeter and to Shoup Park, rehabilitation of the courtyard, repair of the concrete terrace, roof upgrades, wood repairs, rehabilitation of windows, and rehabilitation of doors. Interior work would include carpet removal, new flooring, ceiling and wall repair, replacement or modification of door thresholds, installation of handrails, and replacement of kitchen cabinets and appliances. This alternative would also include structural improvements and building system upgrades for energy efficiency and lighting. For these reasons, this alternative would result in similar impacts to the Townsend’s big-eared bats roosting in the structure as the proposed project. Additionally, exterior work involved with this alternative would include removal of vegetation, which could impact woodrat nests. Mitigation measures MM BIO-1.1 through MM BIO-1.3 and MM BIO-2.1 identified for the proposed project would still need to be implemented to reduce these impacts to a less than significant level.

Preservation Alternative 2 would require structural upgrades for conformance with current State Historic Building Code (SHBC) standards, including ADA accessibility and usability (such as ramps, doorway widening, etc.), fire access, seismic upgrades, and protection of the structure against liquefaction. The City would coordinate with the Fire District to ensure the alternative implements adequate fire access and design standards (e.g., sprinklers). Preservation Alternative 2 would comply with the recommendations identified in the site-specific Geotechnical Investigation. All necessary improvements would need to be completed in compliance with the Secretary of Interior’s Standards for Rehabilitation as they pertain to adaptive reuse, which emphasize minimal change to the defining characteristics of the building and its site and environment. Modifications to the building that would be necessary to meet the SHBC would be dependent on the future adaptive reuse of the building.

Additionally, since the site is currently mapped within a regulatory floodway and floodplain, rehabilitation may be required to comply with the Secretary of Interior’s Guidelines on Flood Adaptation for Rehabilitating Historic Buildings, which includes measures such as elevating the building on a new foundation, as long as those measures would not risk damaging the historic integrity of the structure. However, the Guidelines call for a site-specific assessment of flood risks before determining which measures may be required. As described in Section 4.10.2.1, LIDAR and GPS data indicates the site may not be located in a floodway or floodplain. If a site-specific assessment of flood risks completed as part of the rehabilitation effort determines that the structure is not at risk from potential flooding, no floodproofing measures would be required.

Halsey House Project, SCH# 2025020308 135 Draft Environmental Impact Report City of Los Altos June 2026
Relationship to Project Objectives
Preservation Alternative 2 would meet the project’s objective of complying with the Secretary of the Interior’s Standards since all physical improvements would be required to adhere to the Secretary of the Interior’s Standards for Rehabilitation and Guidelines for Rehabilitating Historic Buildings. As a result, this alternative would not affect the historic integrity of the structure. Full rehabilitation of the Halsey House would also meet the project’s objective of protecting the health, safety, and welfare of the surrounding community by eliminating safety hazards since the building would be restored and safety hazards would be removed. However, this alternative would not meet the project’s objective of reducing or eliminating the cost to rehabilitate the existing structure to a usable condition. This alternative would meet the objective of reducing or eliminating ongoing maintenance costs associated with an unused public facility only if an adaptive reuse of the rehabilitated structure could be identified and if the City would have sufficient funds to maintain and operate the structure in perpetuity. There is not, however, an existing reuse plan for the structure. As such, even with rehabilitation, the City may still have ongoing maintenance costs associated with an unused public facility.

Conclusion
Preservation Alternative 2 would avoid the project’s significant and unavoidable impact but would not avoid the project’s mitigated impacts. The project would meet the health, safety, and welfare objective, adherence to the Secretary of Interior’s Standards objective, as well as the objective related to ongoing maintenance of an unused public facility, but would not meet the objectives related to maintaining and improving public open space at the project site or reducing/eliminating the costs related to rehabilitation.

Preservation Alternative 3 – Partial Rehabilitation/Partial Demolition Preservation Alternative 3 would consist of the demolition of the east and west wings of the structure and rehabilitation of the Entry, Main Room, Ohlone Room, and Ohlone Kitchen, along with a new building addition to house restrooms and an interior ramp. Building uses may include classes, meetings, or special events.

Comparison of Environmental Impacts
As described in the Historic Resource Evaluation prepared for the project, the Halsey House retains integrity for design, materials, and workmanship as many of the character-defining features of the residence are still evident. Halsey House is a modest example of a 1920s Spanish Colonial Revival style residence that retains a high degree of original materials including its stucco cladding, clay tile roof, multi-lite windows and doors, and metal (e.g., hardware and portions of lighting) fixtures. The presence of these features is consistent throughout the residence and demonstrates the 1920s workmanship. Additionally, the landscaping surrounding the Halsey House still consists of the

Halsey House Project, SCH# 2025020308 136 Draft Environmental Impact Report City of Los Altos June 2026
mature trees and fruit trees that were planted by Emma Wright Halsey and Mori during her period of residence.
77 Preservation Alternative 3 would demolish both wings of the Halsey House, which would leave less than half of the original structure intact. This level of demolition would remove many of the character-defining features of the building, significantly affecting the historic integrity of the structure and resulting in a significant unavoidable impact under CEQA. Additionally, this alternative would not avoid demolition-related impacts since some demolition would still occur, and additional construction-related impacts would be created as part of the rehabilitation activities. The mitigation measures and Standard Conditions of Approval identified for the proposed project would still need to be implemented to reduce these impacts to a less than significant level.

Preservation Alternative 3 would require structural upgrades for conformance with current CBC standards, including ADA accessibility, fire access, and protection of the structure against liquefaction. The City would coordinate with the Fire District to ensure the alternative implements adequate fire access and design standards (e.g., sprinklers). Preservation Alternative 3 would comply with the recommendations identified in the site-specific Geotechnical Investigation. Similar to Preservation Alternative 2, all necessary improvements would need to be completed in compliance with the SHBC and the Secretary of Interior’s Standards for Rehabilitation as they pertain to adaptive reuse, which emphasize minimal change to the defining characteristics of the building and its site and environment.

Additionally, as described in Preservation Alternative 2, since the site is currently mapped within a regulatory floodway and floodplain, rehabilitation may be required to comply with the Secretary of Interior’s Guidelines on Flood Adaptation for Rehabilitating Historic Buildings. As described in Section 4.10.2.1, however, LIDAR and GPS data indicates the site may not be located in a floodway or floodplain. If a site-specific assessment of flood risks completed as part of the rehabilitation effort determines that the structure is not at risk from potential flooding, no floodproofing measures would be needed.

Relationship to Project Objectives
Preservation Alternative 3 would meet the project’s objective of protecting the health, safety, and welfare of the surrounding community by eliminating safety hazards since the building would be rehabilitated and safety hazards would be removed. However, this alternative would not adhere to the Secretary of the Interior’s Standards for Rehabilitation and Guidelines for Rehabilitating Historic Buildings because demolition of both wings would affect the historic integrity of the structure, nor would it meet the objective of reducing or eliminating the cost to rehabilitate the existing structure to a usable condition. This alternative would meet the objective of reducing or eliminating ongoing maintenance costs associated with an unused public facility only if an adaptive reuse plan of the rehabilitated structure could be identified and if the City would have sufficient funds to maintain and operate the structure in perpetuity. There is not, however, an existing reuse plan for the 77 Page & Turnbull. Halsey House Historic Resource Evaluation. July 2021. Pages 44 through 47.

Halsey House Project, SCH# 2025020308 137 Draft Environmental Impact Report City of Los Altos June 2026
structure. As such, even with rehabilitation, the City may still have ongoing maintenance costs associated with an unused public facility.

Conclusion
Preservation Alternative 3 would not avoid the project’s significant and unavoidable impact since it includes partial demolition that would alter the historic integrity of the Halsey House. This alternative would meet the health, safety, and welfare objective, as well as the objective related to ongoing maintenance of an unused public facility, but would not meet the objectives related to adherence to the Secretary of the Interior’s Standards, reducing/eliminating rehabilitation costs, or maintaining and improving public open space at the project site.

Preservation Alternative 4 – Mothballing
Mothballing controls the long-term deterioration of a building while it is unoccupied. This process also stabilizes the building and protects the structure from fire, vandalism, and sudden loss. An effort to achieve a successful mothballing requires securing the structure from unwanted entry and providing adequate ventilation. The City currently has the Halsey House boarded up, and a locked fence surrounds the residence to secure the project site and prevent intruders.

Under this alternative, additional actions would be taken to start repairing and/or replacing damaged interior and exteriors surfaces to prevent further deterioration. Areas that have holes or are susceptible to water damage would be covered or filled to prevent water or pest intrusion without damaging the original materials. All debris, including furniture, equipment, appliances, broken glass, would be removed. Window and door openings would be replaced if broken. Any surfaces with signs of vandalism or paint failure would be repainted. The Halsey House would be thoroughly cleaned to remove debris on the floor (including birds, animals or insects, droppings and carcasses from the structure interiors) and to remove any water damaged carpet as moist carpets can promote mold and mildew growth. Additionally, any historic resource elements (such as stucco cladding, clay tile roof, multi-lite windows and doors, and metal features) that are removed would require documentation, cataloging, and storing for safekeeping. All loose architectural or design elements in the Halsey House would be secured in place or cataloged and removed for storage.78 Mothballing typically protects historic buildings for a period of up to 10 years and requires continued monitoring and maintenance during that time.79 Comparison of Environmental Impacts
Preservation Alternative 4 would avoid the project’s significant and unavoidable impacts because it would not substantially change existing conditions or demolish the Halsey House. The mothballing alternative would keep the Halsey House in the same location and repair any damage to the 78 Architectural Resources Group. Halsey House Pricing and Feasibility Study. July 2021. Page 11. 79 United States Department of the Interior, National Park Service. “Preservation Brief 31: Mothballing Historic Building.” Accessed December 19, 2025. https://www.nps.gov/orgs/1739/preservation-briefs.htm.

Halsey House Project, SCH# 2025020308 138 Draft Environmental Impact Report City of Los Altos June 2026
structure, protecting the building from further significant deterioration for a period of up to 10 years. Any repairing or replacing activity would likely require hand tools, not heavy-duty construction equipment powered by diesel engines. In addition, the mothballing alternative would not have construction phases, such as demolition, site preparation, or grading, where soil is disturbed resulting in fugitive dust emissions. Therefore, this alternative would avoid the need for Standard Conditions of Approval to reduce fugitive dust emissions. Additionally, the mothballing alternative would likely not impact woodrats and would not require implementation of MM BIO-1.1 through MM BIO-1.3. However, the mothballing alternative would include eviction of the Townsend’s big-eared bats roosting inside the building. Therefore, Preservation Alternative 4 would require implementation of MM BIO-2.1.

Relationship to Project Objectives
Preservation Alternative 4 would temporarily comply with the health, safety, and welfare objective as certain components of the Halsey House would be repaired and safety hazards would be removed. However, compliance with this objective would only last for the duration of the mothballing is active, monitored, and maintained. As discussed above, mothballing is typically effective for a period of up to 10 years, after which hazards may return due to continued deterioration. It should be noted that the Halsey House is currently in a state of disrepair, and substantial deterioration has already occurred. Given the current condition of the structure, it is unclear if a mothballing effort would be effective for 10 years. Even if it is assumed the mothballing could be completed in accordance with the Secretary of the Interior’s Standards for Mothballing Historic Buildings80, this alternative would not meet the objective of complying with all relevant Secretary of Interior’s Standards because it would not permanently prevent the further deterioration of the structure to the point where it will ultimately lose its historic integrity, and there is currently no approved plan in place to rehabilitate the structure in accordance with the Secretary of Interior’s Standards after the mothballing effort. This alternative would require continued financing to maintain the Halsey House in a less deteriorated condition since mothballing requires ongoing monitoring and maintenance activities; therefore, this alternative would not reduce or eliminate maintenance costs. If mothballing were to occur, the Halsey House would have to be rehabilitated in the future and an adaptive reuse identified or the City would need to again consider demolition of the building. In the short term, this alternative would meet the objective related to reducing costs associated with rehabilitation. In the long term, however, rehabilitation would be required if the intent is to avoid demolition of the structure, since mothballing is only a temporary solution. For a discussion of the implications of rehabilitation, please refer to Preservation Alternative 2 and Preservation Alternative 3.

Conclusion
Preservation Alternative 4 would temporarily avoid the project’s significant and unavoidable historic resource impact since it would not alter the historic integrity of the Halsey House or demolish the residence. Instead, mothballing would stabilize and protect the residence from further 80 Ibid.

Halsey House Project, SCH# 2025020308 139 Draft Environmental Impact Report City of Los Altos June 2026
significant damage for a period of up to 10 years. However, at the end of the effective mothballing period, the structure would need to either be rehabilitated or demolished. The mothballing alternative would meet the health, safety, and welfare objective in the short term, but would not meet this objective once the effective mothballing period has expired. It is unclear is this alternative would meet the Secretary of the Interior’s Standards objective since it would ultimately require rehabilitation or demolition after the effective mothballing period, and there is no approved plan in place for rehabilitation of the structure in accordance with the Secretary of Interior’s Standards and adaptive reuse of the building.

8.2.3 Environmentally Superior Alternative
The CEQA Guidelines state that an EIR shall identify an environmentally superior alternative. If the environmentally superior alternative is the “No Project” alternative, the EIR shall also identify an environmentally superior alternative among the other alternatives (Section 15126.6(e)(2)).

Based on the above discussion, the environmentally superior alternative is the No Project Alternative. The No Project Alternative would retain the site in its current condition with the historic building. Retaining the status quo on the site would avoid all construction and operational impacts associated with the project, including the significant and unavoidable loss of the historic resource, and construction-related air quality and biological resources impacts. Therefore, the No Project Alternative is the environmentally superior alternative; however, it would not achieve the project’s objectives.

CEQA Guidelines Section 15126.6 (e)(2) states that “if the environmentally superior alternative is the No Project Alternative, the EIR shall also identify an environmentally superior alternative among the other alternatives. Beyond the No Project Alternative, the Preservation Alternative 4 – Mothballing would be the environmentally superior alternatives.

Preservation Alternative 4 – Mothballing would avoid the significant unavoidable impact to historic resources. There would also be no construction phases that would result in soil disturbance, grading, or material hauling, and areas of the structure that have deteriorated would be repaired with hand tools, not heavy-duty construction equipment. As a result, air quality impacts related to fugitive dust and biological sources impacts related to woodrats would be avoided, eliminating the need for construction-related Standard Conditions of Approval and MM BIO-1.1 through MM BIO1.3. However, the Townsend’s big-eared bats would be evicted as a result of mothballing, and the project would need to implement MM BIO-2.1 to reduce impacts to the bats. This alternative, however, would not meet any of the project objectives.

Table 8.2-1 below summarizes the difference in impacts from alternatives to the proposed project.

Halsey House Project, SCH# 2025020308 140 Draft Environmental Impact Report City of Los Altos June 2026
Table 8.2-1: Comparison of Impacts from Alternatives to the Proposed Project Impacts Proposed
Project
No
Project
Relocation
of Historic
Resource
Full
Rehabilitation
of Historic
Resource
Partial
Rehabilitation/
Partial
Demolition
Mothballing
Impact BIO-1:

Disturbance of the
existing woodrat nests
on-site could result in
the destruction of nests
and injury or mortality
of individual woodrats.

LTS/M NI LTS/M LTS/M LTS/M NI
Impact BIO-2:

Demolition of the
structure on-site would
disturb Townsend’s bigeared bats roosting
within the structure.

LTS/M NI LTS/M LTS/M LTS/M LTS/M
Impact CUL-1:

Implementation of the
proposed project
would result in the
demolition of the
Halsey House, which is
a historic resource.

SU NI SU LTS SU LTS
Impact HAZ-1:

Demolition of the
existing building could
expose construction
workers or residents in
the vicinity of the
project site to harmful
levels of ACMs or LBPs.

LTS/M NI NI LTS/M LTS/M LTS/M
Meets Project’s
Objectives?
Objective 1 Yes No Yes Yes Yes No
Objective 2 Yes No Yes No No No
Objective 3 Yes No No Yes Yes No
Objective 4 Yes No No No No No
Objective 5 Yes No No Yes No No
Notes: LTS/M = less than significant impact with mitigation incorporated; LTS = less than significant impact; NI = no impact
Bold text indicates being environmentally superior to the proposed project.

Halsey House Project, SCH# 2025020308 141 Draft Environmental Impact Report City of Los Altos June 2026
Section 9.0 References
The analysis in this EIR is based on the professional judgement and expertise of the environmental specialists preparing this document, based upon review of the site, surrounding conditions, site plans, and the following references:

Architectural Resources Group. Halsey House Pricing and Feasibility Study. July 2021.

Association of Bay Area Governments and Metropolitan Transportation Commission. Plan Bay Area 2050. October 21, 2021.

Bay Area Air Quality Management District. “Air Quality Standards and Attainment Status.” Last Updated December 15, 2025. Accessed December 19, 2025. https://www.baaqmd.gov/about-airquality/research-and-data/air-quality-standards-and-attainment-status.

---. Final 2017 Clean Air Plan. April 19, 2017. Page 12. ---. “Permitted Stationary Sources Screening Report.” Accessed December 19, 2025. Available at https://baaqmd.maps.arcgis.com/apps/webappviewer/index.html?id=845658c19eae4594b9f4b805 fb9d89a3.

Boccaleoni, Anthony. Environmental Manager, Republic Services, Inc. Personal Communication.

May 12, 2023.

California Air Resources Board. 2022 Scoping Plan for Achieving Carbon Neutrality. December 2022. ---. “Advanced Clean Cars II.” Accessed February 27, 2025. https://ww2.arb.ca.gov/ourwork/programs/advanced-clean-cars-program/advanced-clean-cars-ii. ---. “Overview: Diesel Exhaust and Health.” Accessed December 19, 2025. https://ww2.arb.ca.gov/resources/overview-diesel-exhaust-and-health.

California Building Standards Commission. “California Building Standards Code.” Accessed December 19, 2025. https://www.dgs.ca.gov/BSC/Codes#@ViewBag.JumpTo.

California Department of Conservation. “California Important Farmland Finder.” Accessed December 19, 2025. https://maps.conservation.ca.gov/DLRP/CIFF/. ---. “Earthquake Zones of Required Investigation.” Accessed December 19, 2025. https://maps.conservation.ca.gov/cgs/EQZApp/.
---. “Farmland Mapping and Monitoring Program.” Accessed December 19, 2025. http://www.conservation.ca.gov/dlrp/fmmp/Pages/Index.aspx. ---. “Williamson Act.” Accessed December 19, 2025. http://www.conservation.ca.gov/dlrp/lca.

Halsey House Project, SCH# 2025020308 142 Draft Environmental Impact Report City of Los Altos June 2026
California Department of Forestry and Fire Protection. “Fire and Resource Assessment Program.” Accessed December 19, 2025. http://frap.fire.ca.gov/.
---. “Fire Hazard Severity Zones.” Accessed December 19, 2025. https://osfm.fire.ca.gov/what-wedo/community-wildfire-preparedness-and-mitigation/fire-hazard-severity-zones.

California Department of Housing and Community Development. “Regional Housing Needs Allocation and Housing Elements” Accessed December 19, 2025. https://www.hcd.ca.gov/planningand-community-development/housing-elements California Department of Resources Recycling and Recovery. “Five-Year Countywide or Regional Agency Integrated Waste Management Plan Review Report Guidelines.” Accessed December 19, 2025. https://calrecycle.ca.gov/lgcentral/library/policy/5yrreview/.

California Department of Transportation. “Scenic Highways.” Accessed December 19, 2025. https://dot.ca.gov/programs/design/lap-landscape-architecture-and-community-livability/lap-liv-iscenic-highways.

California Environmental Protection Agency. “Cortese List Data Resources.” Accessed December 19, 2025. https://calepa.ca.gov/sitecleanup/corteselist/.

California Office of Historic Preservation. “California Office of Historic Preservation Technical Assistance Series #6.” Accessed August December 19, 2025. https://ohp.parks.ca.gov/pages/1069/files/technical%20assistance%20bulletin%206%202011%20u pdate.pdf.

California State Water Resources Control Board. “2020-2022 California Integrated Report (Clean Water Act Section 303(d) List and 305(b) Report).” May 11, 2022. Accessed December 19, 2025. https://www.waterboards.ca.gov/water_issues/programs/water_quality_assessment/2020_2022_i ntegrated_report.html.

California Water Service. 2020 Urban Water Management Plan, Los Altos Suburban District. June 2021. https://www.calwater.com/docs/uwmp2020/LAS_2020_UWMP_FINAL.pdf CalRecycle. Analysis of the Progress Toward the SB 1383 Organic Wase Reduction Goals. August 18, 2020.
https://www2.calrecycle.ca.gov/Publications/Details/1693#:~:text=Analysis%20of%20the%20Progr ess%20Toward,(DRRR%2D2020%2D1693)&text=SB%201383%20establishes%20targets%20to,75%2 0percent%20reduction%20by%202025.

City of Los Altos. 6
th Cycle Housing Element 2023-2031. Adopted January 2023, revised August 2023. https://www.losaltosca.gov/DocumentCenter/View/286/6th-Cycle-Los-Altos-Housing-Element2023-to-2031-PDF. ---. “About Us.” Accessed December 19, 2025 https://www.losaltosca.gov/262/About-Us.

---. City of Los Altos Bicycle Transportation Plan. April 10, 2012.

Halsey House Project, SCH# 2025020308 143 Draft Environmental Impact Report City of Los Altos June 2026
---. City of Los Altos Pedestrian Master Plan. August 2015. ---. “Fire.” Accessed December 19, 2025. https://www.losaltosca.gov/358/Fire.

---. “Historic Resources Inventory.” Accessed December 19, 2025. https://www.losaltosca.gov/535/Historic-Inventory.
---. Initial Study/Mitigated Negative Declaration for the Los Altos General Plan Update. November 2002.
---. “Local Creeks.” Accessed December 19, 2025. https://www.losaltosca.gov/461/Local-Creeks. ---. Los Altos General Plan Initial Study/Mitigated Negative Declaration. November 2002. ---. “Map of Parks.” Accessed December 19, 2025.
https://www.losaltosca.gov/documentcenter/view/1950.
---. “School Districts.” Accessed December 19, 2025. https://www.losaltosca.gov/462/SchoolDistricts. ---. “Stormwater Master Plan – Appendix A: Drainage Basins.” Accessed December 19, 2025. https://www.losaltosca.gov/441/Stormwater-Master-Plan.
---. “Public Works – Sanitary Sewer.” Accessed December 19, 2025. https://www.losaltosca.gov/432/Sanitary-Sewer.

Cornerstone Earth Group. Geotechnical Investigation Halsey House. February 2024.

County of Santa Clara. “Soils of Santa Clara County,” Accessed December 19, 2025. https://hub.arcgis.com/datasets/sccplanning::soils-of-santa-clara-county/explore. ---. “Williamson Act Properties Map,” Accessed December 19, 2025. https://experience.arcgis.com/experience/034e46f2f4bc44d1ada505dd92940ff7.

CSG Consultants, Inc. Halsey House Bridge Crossing Structural Assessment Memorandum. December 2025.

Department of Toxic Substances Control. “EnviroStor database.” Accessed December 19, 2025. https://www.envirostor.dtsc.ca.gov/public.

Page & Turnbull. Halsey House Historic Resource Evaluation. July 2021. ---. Halsey House Relocation Feasibility Study. July 2024.

Schaaf & Wheeler. Halsey House CEQA Hydrology Memorandum. March 2024. Page 3.

Silicon Valley Clean Energy. “Frequently Asked Questions.” Accessed December 19, 2025. https://www.svcleanenergy.org/faqs.

Halsey House Project, SCH# 2025020308 144 Draft Environmental Impact Report City of Los Altos June 2026
State of California Department of Finance. “E-5 Population and Housing Estimates for Cities, Counties and the State — January 1, 2021-2025.” May 2025. Accessed December 19, 2025. https://dof.ca.gov/forecasting/demographics/estimates/e-5-population-and-housing-estimates-forcities-counties-and-the-state-2020-2025/ State Water Resources Control Board. “GeoTracker.” Accessed December 19, 2025. https://geotracker.waterboards.ca.gov.

United States Department of Energy. “Energy Independence & Security Act of 2007.” Accessed December 19, 2025. http://www.afdc.energy.gov/laws/eisa.

United States Energy Information Administration. “California State Energy Profile.” Accessed December 19, 2025. https://www.eia.gov/state/print.php?sid=CA. ---. Energy Information Administration. “Petroleum & Other Liquids, California Field Production of Crude Oil.” September 27, 2023. Accessed December 19, 2025. https://www.eia.gov/dnav/pet/hist/LeafHandler.ashx?n=pet&s=mcrfpca1&f=a United States Environmental Protection Agency. “The 2022 EPA Automotive Trends Report:

Greenhouse Gas Emissions, Fuel Economy, and Technology since 1975.” December 2022. Accessed December 19, 2025. https://www.epa.gov/system/files/documents/2022-12/420r22029.pdf.

United States Department of Transportation. “USDOT Announces New Vehicle Fuel Economy Standards for Model Year 2024-2026.” April 1, 2022. Accessed December 19, 2025. https://www.nhtsa.gov/press-releases/usdot-announces-new-vehicle-fuel-economy-standardsmodel-year-2024-2026.

United States Environmental Protection Agency. “EPA Actions to Protect the Public from Exposure to Asbestos.” Accessed December 19, 2025. https://www.epa.gov/asbestos/epa-actions-protectpublic-exposure-asbestos ---. “Superfund: CERCLA Overview.” Accessed December 19, 2025. https://www.epa.gov/superfund/superfund-cercla-overview. ---. “Summary of the Resource Conservation and Recovery Act.” Accessed December 19, 2025. https://www.epa.gov/laws-regulations/summary-resource-conservation-and-recovery-act.

Valley Transportation Authority. “40 Local Schematic Map.” Effective August 14, 2023. Accessed December 19, 2025. https://www.vta.org/go/routes/40.
---. “52 Local Schematic Map.” Effective August 14, 2023. Accessed December 19, 2025. https://www.vta.org/go/routes/52.
---. “System Map.” October 30, 2023. Accessed December 19, 2025. https://www.vta.org/sites/default/files/2023-10/System-Map-103023.pdf.

Valley Water. 2021 Groundwater Management Plan, Santa Clara and Llagas Subbasins. November 2021.

Halsey House Project, SCH# 2025020308 145 Draft Environmental Impact Report City of Los Altos June 2026
---. “Map of District Creeks.” Accessed December 19, 2025. https://valleywater.maps.arcgis.com/apps/instant/nearby/index.html?appid=3f6d541471544eea8b f27a3259ec0384&sliderDistance=1.

Halsey House Project, SCH# 2025020308 146 Draft Environmental Impact Report City of Los Altos June 2026
Section 10.0 Lead Agency and Consultants

10.1 Lead Agency
City of Los Altos
Stephanie Williams, Development Services Director
Harun Musaefendic, Associate Civil Engineer

10.2 Consultants
David J. Powers & Associates, Inc.

Environmental Consultants and Planners
Shannon George, Principal and Vice President
Michael Lisenbee, Senior Project Manager
Mimi McNamara, Project Manager
Maria Kisyova, Project Manager
Nick Towstopiat, Project Manager
Ryan Osako, Graphic Artist
Cornerstone Earth Group, Inc.

Geotechnical Engineers
Stephen Ohlsen, Senior Project Engineer
Jesse Serpa, Senior Staff Engineer
Page & Turnbull
Historic Resource Consultants
Ruth Todd, Principal
Sarah Brummett, Senior Associate, Director of the Preservation Technology Studio, Designer/Senior Preservation Specialist
Schaaf & Wheeler
Hydrology Civil Engineers
Robin Lee, Senior Project Manager
Sarah Weinberg, Assistant Civil Engineer

Halsey House Project, SCH# 2025020308 147 Draft Environmental Impact Report City of Los Altos June 2026
Section 11.0 Acronyms and Abbreviations
AB Assembly Bill
ABAG Association of Bay Area Governments
ACM Asbestos-Containing Material
Air District Bay Area Air District
ALUC Airport Land Use Commission
APN Assessor’s Parcel Number
asml above mean sea level
ATCM Asbestos Airborne Toxic Control Measure
Bay Area San Francisco Bay Area
bgs below ground surface
BTP Bicycle Transportation Plan
BMP best management practice
Btu British thermal unit
CAAQS California Ambient Air Quality Standard
CAL FIRE California Department of Forestry and Fire Protection Cal/OSHA California Department of Industrial Relations, Division of Occupational Safety and Health
CalARP California Accidental Release Prevention
CalEPA California Environmental Protection Agency
CALGreen California Green Building Standards
Caltrans California Department of Transportation
CARB California Air Resources Board
CBC California Building Standards Code
CDFW California Department of Fish and Wildlife
CEQA California Environmental Quality Act
CERCLA Comprehensive Environmental Response, Compensation, and Liability Act CFC chlorofluorocarbon
CFR Code of Federal Regulations
CGS California Geological Survey
CH4 methane
CIWMP County Integrated Waste Management Plan

Halsey House Project, SCH# 2025020308 148 Draft Environmental Impact Report City of Los Altos June 2026
CLUP Comprehensive Land Use Plan
CNEL Community Noise Equivalent Level
CO carbon monoxide
CO2 carbon dioxide
CO2e carbon dioxide equivalents
CRHR California Register of Historical Resources
CSMP Complete Streets Master Plan
CUPA Certified Unified Program Agency
dBA A-weighted decibel
DNL Day/Night Average Sound Level
DPM diesel particulate matter
DTSC Department of Toxic Substances Control
EIR Environmental Impact Report
EO Executive Order
EPA United States Environmental Protection Agency
ESA Environmental Site Assessment
EV electric vehicle
FAA Federal Aviation Administration
FAR floor area ratio
FHSZ Fire Hazard Severity Zone
FMMP Farmland Mapping and Monitoring Program
GHG greenhouse gases
GHGRS Greenhouse Gas Reduction Strategy
GWh gigawatt hour
GWP Global Warming Potential
HABS Historic American Building Survey
HRI Historic Resources Inventory
HSWA Hazardous and Solid Waste Amendments
Leq Energy-Equivalent Sound/Noise Descriptor
Lmax Maximum A-weighted noise level during a measurement period LAMC Los Altos Municipal Code
LAS District Los Altos Suburban District

Halsey House Project, SCH# 2025020308 149 Draft Environmental Impact Report City of Los Altos June 2026
LOS Level of Service
LRA Local Responsibility Area
MBTA Migratory Bird Treaty Act
MMTCO2e Million Metric Tons of Carbon Dioxide Equivalent MND Mitigated Negative Declaration
mpg miles per gallon
MSL mean sea level
MTC Metropolitan Transportation Commission
N2O nitrous oxide
NAAQS National Ambient Air Quality Standard
NAHC Native American Heritage Commission
NCP National Contingency Plan
NESHAP National Emission Standards for Hazardous Air Pollutants NISL Newby Island Sanitary Landfill
NO2 nitrogen dioxide
NOA Naturally Occurring Asbestos
NOD Notice of Determination
NOx Nitrogen Oxides
NRHP National Register of Historic Places
NTMP neighborhood traffic management program
O3 ozone
OITC Outdoor-Indoor Transmission Class
PARWQCP Palo Alto Regional Water Pollution Control Plant PCB polychlorinated biphenyls
PCF perfluorocarbon
PDA Priority Development Area
PG&E Pacific Gas and Electric Company
PM particulate matter
PM10 Particulate matter with a diameter of 10 microns or less PM2.5 Particulate matter with a diameter of 2.5 microns or less PMP Pedestrian Master Plan
PPV Peak Particle Velocity

Halsey House Project, SCH# 2025020308 150 Draft Environmental Impact Report City of Los Altos June 2026
RAP Removal Action Plan
RCRA Resource Conservation and Recovery Act
RHNA Regional Housing Needs Allocation
ROG Reactive Organic Gases
RTP Regional Transportation Plan
RWQCB Regional Water Quality Control Board
SB State Bill
SCS Sustainable Communities Strategy
SF6 Sulfur Hexafluoride
SHMA Seismic Hazards Mapping Act
SMARA Surface Mining and Reclamation Act
SMP Site Management Plan
SOx Sulfur Oxides
SR State Route
SRA State Responsibility Area
STC Sound Transmission Class
SWRCB State Water Resources Control Board
TAC Toxic Air Contaminants
Title 24 Title 24, Part 6 of the California Code of Regulations TSCA Toxic Substances Control Act
USACE United States Army Corps of Engineers
USFWS United States Fish and Wildlife Service
UWMP Urban Water Management Plan
VMT Vehicle Miles Traveled
VTA Santa Clara Valley Transportation Authority
Williamson Act California Land Conservation Act
WSA Water Supply Assessment
ZNE Zero Net Carbon Emission

NOTICE OF PREPARATION OF

A DRAFT ENVIRONMENTAL IMPACT REPORT

FOR THE HALSEY HOUSE PROJECT
Los Altos, California
February 2025
PROJECT APPLICANT: City of Los Altos
APN: 175-30-021
As the Lead Agency, the City of Los Altos will prepare an Environmental Impact Report for the above-referenced project and would like your views regarding the scope and content of the environmental information to be addressed in the EIR.

The project description, location, and a brief summary of the environmental effects that could result from the proposed project are attached.

According to State law, the deadline for your response is 30 days after receipt of this notice; however, we would appreciate an earlier response, if possible. Please identify a contact person, and send your response to:

City of Los Altos
Public Works Department
Attention: Harun Musaefendic
One North San Antonio Road
Los Altos, CA 94022
[email protected]
Aida Fairman, Public Works Director Date
2/6/2025
Attachment 2 - Appendix A

1 City of Los Altos – Halsey House Project Notice of Preparation

NOTICE OF PREPARATION OF

A DRAFT ENVIRONMENTAL IMPACT REPORT

FOR THE HALSEY HOUSE PROJECT
February 2025
A. INTRODUCTION
The purpose of an Environmental Impact Report (EIR) is to inform decision-makers and the general public of the environmental effects of a proposed project that an agency may implement or approve. The EIR process is intended to provide information sufficient to evaluate a project and its potential for significant impacts on the environment, to examine methods of reducing adverse impacts, and to consider alternatives to the project.

An EIR is prepared when it is determined by the discretionary authority that changes proposed in an approved project will require revisions to the previous EIR because of possible new impacts or an increase in severity of previously identified impacts. As the Lead Agency, the City of Los Altos will prepare an EIR to address the environmental effects of the Halsey House Project.

The EIR will be prepared and processed in accordance with the California Environmental Quality Act (CEQA) of 1970, as amended, and the requirements of the City of Los Altos. In accordance with the requirements of CEQA, the EIR will include the following:
• A summary of the project;
• A project description, including project objectives;
• A description of the existing environmental setting, probable environmental impacts, and mitigation measures; and
• Environmental consequences, including (a) any significant environmental effects which cannot be avoided if the project is implemented; (b) any significant irreversible and irretrievable commitments of resources; (c) the growth inducing impacts of the proposed project; and (d) cumulative impacts.

The EIR also will discuss a reasonable range of alternatives to the project that could reasonably attain most of the basic objectives of the project and would avoid or substantially lessen any of the significant environmental effects of the project (CEQA Guidelines Section 15126.6[a]).

Project Location
The project site is located at 482 University Avenue in Los Altos (Assessor Parcel Number [APN] 175- 30-021). The site is situated within the six-acre Redwood Grove Nature Preserve, which is surrounded by single-family residences.

2 City of Los Altos – Halsey House Project Notice of Preparation Refer to Figures 1 and Figure 2 for regional and vicinity maps of the project site. An aerial photograph with surrounding land uses is shown on Figure 3. The project disturbance area is shown in Figure 4.

Project Description
The Halsey House was built in 1923 and used as a private residence until the property was purchased by the City of Los Altos in 1974 to serve as a park. The building was then converted to a nature center for educational and recreational programming. In 2008, the building was closed to the public. Since 2008, the Halsey House has remained vacant and unused. The Halsey House is a local Historic Landmark and is eligible for the California Register of Historic Resources (CRHR). As a result, it is considered a historic resource under CEQA.

The project proposes to demolish the Halsey House building. Demolition activities would occur within an approximately 15,000 square foot (or 0.3 acre) area of disturbance surrounding the building and would last roughly three months. Demolition equipment, such as an excavator, a bulldozer, and a track loader, would be utilized throughout the demolition period. Equipment and workers would access the site via the Redwood Grove Nature Preserve entrance on University Avenue. Equipment staging would occur within the proposed area of disturbance. After demolition of the building, the site would be cleared and replanted with native plant landscaping that matches the existing vegetation. All building materials would be hauled to an appropriate off-site disposal location.

Required Project Approvals
• Historical Alteration Permit
Potential Significant Environmental Impacts of the Project The EIR will identify the significant environmental effects anticipated to result from development of the project as proposed. Mitigation measures will be identified for significant impacts, as warranted. The EIR will include a discussion of all impact areas required by the CEQA Guidelines, with a particular focus on the following specific environmental categories most relevant to the proposed project:
• Biological Resources – The project site is located in the Redwood Grove Nature Preserve, which includes mature redwoods and Adobe Creek. The area has the potential to support special-status species (bats and the great blue heron) and sensitive habitats (wetlands). The EIR will identify the existing biological conditions, including special-status species with the potential to occur on the project site and any potentially sensitive/regulated habitats that may be present. In addition, the EIR will identify and discuss the project’s biological impacts during demolition.

3 City of Los Altos – Halsey House Project Notice of Preparation • Cultural Resources – The project, as proposed, would demolish the Halsey House, which is a local Historic Landmark and is eligible for the CRHR. This would be a significant impact under CEQA that could not be mitigated to a less than significant level. The EIR will disclose the significant and unavoidable impact, identify all feasible mitigation (such as recordation and salvage), and identify a reasonable range of alternatives to the proposed project. • Hydrology and Water Quality – The project site is currently mapped in an area designated as a Zone AE Special Flood Hazard Area (SFHA) by the Federal Emergency Management Agency (FEMA). Additionally, the Halsey House structure is partially within a mapped floodway associated with Adobe Creek. Floodways are FEMA designated areas where no placement of blockages shall occur unless an analysis is conducted that shows the structures present no impact. The EIR will analyze the surrounding floodplain and determine whether or not the existing structure impedes flood flows. The EIR will also evaluate the impacts of demolishing the structure
• Cumulative Impacts – Pursuant to CEQA Guideline Section 15130, the EIR will discuss the cumulative impacts of the project in combination with other past, present or reasonably foreseeable projects.
• Alternatives to the Project – Pursuant to CEQA Guidelines Section 15126.6, the EIR will evaluate a reasonable range of alternatives to the project, based on the results of the environmental analysis. A No Project Alternative will be evaluated along with its impacts.

The alternatives discussion will focus on those alternatives that could feasibly accomplish most of the basic objectives of the proposed project and could avoid or substantially lessen one or more of the significant environmental effects identified in the EIR (CEQA Guidelines Section 15126.6). The environmentally superior alternative(s) will be identified based on the number and degree of associated environmental impacts.

In addition, the EIR will address the project’s impacts on aesthetics, agricultural/forestry resources, air quality, energy, greenhouse gas emissions, hazards and hazardous materials, land use/planning, mineral resources, noise, population/housing, public services, recreation, transportation, tribal cultural resources, utilities/service systems, and wildfire. The EIR will also include all other sections required under the CEQA Guidelines including significant and unavoidable impacts, significant irreversible environmental changes, and growth-inducing impacts.

Base Map: ESRI, ArcGIS.

Saratoga
CuperƟno
Sunnyvale
Palo Alto
Menlo Park
East Palo Alto
Redwood City
Saratoga
CuperƟno
Sunnyvale
Los Altos os Altos
Mountain
View
Mountain
View
Palo Alto
Menlo Park
East Palo Alto
Redwood City San
Francisco
Bay
85 84
85 237
280
280
101
101
Project Site
04 .5 6 Miles 3
Pacific Ocean
Monterey Bay
San José an José
Sunnyvale unnyvale
San Fremont San Mateo
Redwood City edwood City
Livermore ivermore
Oakland
San Francisco an Francisco
Santa Cruz anta Cruz
Mountain View ountain View
Morgan Hill organ Hill
Project Site roject Site
San Francisco Bay
CuperƟno
Los Altos os Altos
REGIONAL MAP FIGURE 1

Lennox Way
Fremont Road
Burke Road
Chapin
Road
Darling
Lane
Burke
Lane
East
Sunset
Drive
West Sunset Drive
Manresa Lane
Manresa
Way
Manresa Way
University Avenue
Adobe
Creek Way
Sherman Street
Orange Avenue
Palm Avenue
Sheridan Street
Lee Street
Lincoln Avenue
Lincoln Avenue
Foothill Expressway
1st Street Lyell Street
Lennox Way Fremont Road
Burke Road
Chapin Road
Darling
Lane
Burke Lane
E
a
s
t
S
u
n
s
e
t
D
rive
West Sunset
Driv
e
Manresa Lane
M
a
n
re
s
a
W
a
y
Manresa Way
University Avenue
Ado
b
e
C
r
e
e
k
W
ay
Sherman Street
Orange Avenue
Palm Avenue
Sheridan Street
Lee Street Lincoln Avenue
Lincoln Avenue
Foothill Expressway
1st Street Lyell Street
Base Map: ESRI, ArcGIS
0 50 300 400 600 Feet
Project Boundary
Halsey House
VICINITY MAP FIGURE 2

ResidenƟal
ResidenƟal
ResidenƟal
ResidenƟal
ResidenƟal
ResidenƟal
Redwood Grove
Nature Preserve
Fremont Road
Lennox Way
Lennox Way
Manresa Lane
Sheridan Street
University Avenue
Sherman Street
Orange Avenue
Adobe Creek Way
Fremont Road
Lennox Way
Lennox Way
Manresa Lane
Sheridan Street
University Avenue Sherman Street
Orange Avenue
Adobe Creek Way Photo Date: Apr. 2022
0 25 150 200 300 Feet
Project Boundary
Halsey House
Aerial Source: Google Earth Pro, Apr. 19, 2024.

AERIAL PHOTOGRAPH AND SURROUNDING LAND USES FIGURE 3

Fremont Road
Lennox Way
Lennox Way
Manresa Lane
Sheridan Street
Sherman Street
Orange Avenue
Adobe Creek Way
Fremont Road
Lennox Way
Lennox Way
Manresa Lane
Sheridan Street
Sherman Street
Orange Avenue
Adobe Creek Way
University AvenueUniversity Avenue
Photo Date: Apr. 2022
0 25 150 200 300 Feet
Project Boundary
Halsey House
Aerial Source: Google Earth Pro, Apr. 19, 2024.

SITE PLAN FIGURE 4

Mr. Gabriel Engeland March 14, 2025
City manager, City of Los Altos
1 North San Antonio Rd.

Los Altos, CA 94022
Dear Mr. Engeland:

Friends of Historic Redwood Grove was formed in 2014 by a group of Los Altos residents with the goal of ensuring the preservation of Redwood Grove along with its historic elements. As you may be aware, we were instrumental in funding a Historic Resource Evaluation (HRE) of Halsey House and have continued to advocate for the preservation and restoration of this important City landmark.

It has come to our attention that the City of Los Altos is working to develop an Environmental impact Report at the request of the Los Altos City Council to evaluate a range of alternatives for this building. The EIR File, number EVN25467 was filed with the County of Santa Clara on February 12, 2025. This email is in response to that action.

The City of Los Altos is required to conduct a PUBLIC scoping meeting prior to initiating an EIR if publicly requested or considered of state or regional designation (including historical buildings) Two draft EIR filings by the City of Los Altos contain statements acknowledging this requirement:

1. CONSISTENT with Section 21083.9 of the CEQA statute, the City will conduct a scoping meeting, solicit input and comments from the general public and public agencies as to the content and scope of the Draft EIR.

2. Section 21083.9 of the California Environmental Quality Act (CEQA) statute mandates that an agency must hold scoping meetings for a proposed project if a written requests made, particularly for projects that may significantly impact highways or other facilities under the Department of Transportation’s jurisdiction, or projects considered to be of statewide, regional areawide significance.

Halsey House meets the above criteria and Friends of Historic Redwood Grove is requesting a public scoping meeting in which the content and scope of the Draft EIR will be discussed.

Best Regards,
Marie Backs,
President, Friends of Historic Redwood Grove

From: Harun Musaefendic
To: Michael Lisenbee
Cc: Aida Fairman
Subject: FW: Halsey House Notice of CEQA Prep
Date: Wednesday, March 26, 2025 4:11:47 PM
Hey Michael,
See comments from Jim Wing below, I’m not sure if I have sent them before.

Let me know if you have any questions.

Thank you,
Harun Musaefendic, PE
Associate Civil Engineer
From: Jim Wing <[email protected]>
Sent: Sunday, March 9, 2025 12:06 PM
To: Harun Musaefendic <[email protected]>
Cc: Aida Fairman <[email protected]>; Gabriel Engeland <[email protected]> Subject: Halsey House Notice of CEQA Prep
Harun Musaefendic,
Thank you for posting notice of CEQA Preparation on Los Altos Web site! I recommend you reconsider technical feasibility for Project Description – page 2-Equipment Access from Redwood Grove University Entrance that requires crossing “8 Ton Bridge” and equipment access through narrow road space between two major Redwood Trees. As you may already know “8 Ton Bridge” main structural beams have deteriorated and show heavy signs of “stress dusting” when Los Altos Maintenance trucks cross. This was noted by prior Public Works Director Jim Sandoval before he retired and CEQA Construction Consultant last March. At my March 2024 on-site meeting with CEQA Construction Consultant, he was going to recommend equipment access via Manresa.

What is your estimated public release date for complete CEQA report? I am interested in creekbank soil core sample data from septic tank / drain field and lead contamination from water pipes.

Since you are also working on Adobe Creek Sewer Line replacement project, I would like to make you aware of major cost / environmental impact reduction by eliminating two creek crossings that only serve abandoned sewer line that may have never been hooked up to Halsey House.

Thank you for your consideration.

From: Harun Musaefendic
To: Michael Lisenbee
Cc: Aida Fairman
Subject: FW: Valley Water Comments on Notice of Preparation Date: Thursday, March 20, 2025 4:11:44 PM
Hey Mike,
Received the following comments from Shree at Valley Water. I’ll save them in our project folder but want to make sure you are aware of these comments as well.

Please let me know if you have any questions.

Thank you,
Harun Musaefendic, PE
Associate Civil Engineer
From: Shree Dharasker <[email protected]>
Sent: Wednesday, March 19, 2025 10:12 AM
To: Harun Musaefendic <[email protected]>
Cc: Josh Weinik <[email protected]>
Subject: Valley Water Comments on Notice of Preparation Dear Mr. Musaefendic:

The Santa Clara Valley Water District (Valley Water) has reviewed the February 6, 2025 Notice of Preparation for a draft Environmental Impact Report (EIR) for the Halsey House project in Los Altos, and has the following comments:

1. Please clarify if the "Native plant landscaping" described in the Project Description, aims to meet aesthetic needs or if an ecological restoration is planned

2. Biological resource consideration scope needs to include nearby Valley Water native plant mitigation site on Abode Creek at the Jesuit Retreat. This project should not impact Valley Water’s mitigation site.

3. There are more sensitive habitats in addition to wetlands. Flagging for sensitive habitats such as redwood forest and riparian woodlands should be considered The above comments should be addressed in the EIR. Valley Water has no right of way or ground water wells at this location. No encroachment permit will therefore be required. The site is in FEMA Flood Zone X ( area determined to be outside the 500‐year flood and protected by levee from 100‐ year flood),
Please contact me if there are any questions. Valley Water would like to review future environmental documents on this project,

Shree Dharasker
Associate Engineer Civil
Community Projects Review Unit
(408)630-3037

Halsey House Demolition Project Detailed Report, 3/1/2024 1 / 19
Halsey House Demolition Project Detailed Report
Table of Contents

1. Basic Project Information

1.1. Basic Project Information

1.2. Land Use Types

1.3. User-Selected Emission Reduction Measures by Emissions Sector

2. Emissions Summary

2.1. Construction Emissions Compared Against Thresholds

2.2. Construction Emissions by Year, Unmitigated

3. Construction Emissions Details

3.1. Demolition (2025) - Unmitigated

4. Operations Emissions Details

4.10. Soil Carbon Accumulation By Vegetation Type

4.10.1. Soil Carbon Accumulation By Vegetation Type - Unmitigated

4.10.2. Above and Belowground Carbon Accumulation by Land Use Type - Unmitigated

4.10.3. Avoided and Sequestered Emissions by Species - Unmitigated Attachment 3 - Appendix B

Halsey House Demolition Project Detailed Report, 3/1/2024 2 / 19

5. Activity Data

5.1. Construction Schedule

5.2. Off-Road Equipment

5.2.1. Unmitigated

5.3. Construction Vehicles

5.3.1. Unmitigated

5.4. Vehicles

5.4.1. Construction Vehicle Control Strategies

5.5. Architectural Coatings

5.6. Dust Mitigation

5.6.1. Construction Earthmoving Activities

5.6.2. Construction Earthmoving Control Strategies

5.7. Construction Paving

5.8. Construction Electricity Consumption and Emissions Factors

5.18. Vegetation

5.18.1. Land Use Change

5.18.1.1. Unmitigated

Halsey House Demolition Project Detailed Report, 3/1/2024 3 / 19

5.18.1. Biomass Cover Type

5.18.1.1. Unmitigated

5.18.2. Sequestration

5.18.2.1. Unmitigated

6. Climate Risk Detailed Report

6.1. Climate Risk Summary

6.2. Initial Climate Risk Scores

6.3. Adjusted Climate Risk Scores

6.4. Climate Risk Reduction Measures

7. Health and Equity Details

7.1. CalEnviroScreen 4.0 Scores

7.2. Healthy Places Index Scores

7.3. Overall Health & Equity Scores

7.4. Health & Equity Measures

7.5. Evaluation Scorecard

7.6. Health & Equity Custom Measures

8. User Changes to Default Data

Halsey House Demolition Project Detailed Report, 3/1/2024 4 / 19

1. Basic Project Information

1.1. Basic Project Information
Data Field Value
Project Name Halsey House Demolition Project
Construction Start Date 1/1/2025
Lead Agency —
Land Use Scale Project/site
Analysis Level for Defaults County
Windspeed (m/s) 2.70
Precipitation (days) 32.8
Location 37.37293862875913, -122.11975058114137
County Santa Clara
City Los Altos
Air District Bay Area AQMD
Air Basin San Francisco Bay Area
TAZ 1720
EDFZ 1
Electric Utility Pacific Gas & Electric Company
Gas Utility Pacific Gas & Electric
App Version 2022.1.1.21

1.2. Land Use Types
Land Use Subtype Size Unit Lot Acreage Building Area (sq ft) Landscape Area (sq ft)
Special Landscape
Area (sq ft)
Population Description
Single Family
Housing

1.00 Dwelling Unit 0.32 1,950 11,713 — 3.00 —

Halsey House Demolition Project Detailed Report, 3/1/2024 5 / 19

1.3. User-Selected Emission Reduction Measures by Emissions Sector No measures selected

2. Emissions Summary

2.1. Construction Emissions Compared Against Thresholds Criteria Pollutants (lb/day for daily, ton/yr for annual) and GHGs (lb/day for daily, MT/yr for annual) Un/Mit. TOG ROG NOx CO SO2 PM10E PM10D PM10T PM2.5E PM2.5D PM2.5T BCO2 NBCO2 CO2T CH4 N2O R CO2e Daily,
Winter
(Max)
— — — — — — — — — — — — — — — — — —
Unmit. 0.73 0.61 5.31 7.16 0.01 0.18 0.91 1.09 0.17 0.11 0.28 — 1,168 1,168 0.05 0.02 0.02 1,177 Average
Daily
(Max)
— — — — — — — — — — — — — — — — — —
Unmit. 0.13 0.11 0.93 1.25 < 0.005 0.03 0.15 0.18 0.03 0.02 0.05 — 205 205 0.01 < 0.005 0.05 207 Annual
(Max)
— — — — — — — — — — — — — — — — — —
Unmit. 0.02 0.02 0.17 0.23 < 0.005 0.01 0.03 0.03 0.01 < 0.005 0.01 — 33.9 33.9 < 0.005 < 0.005 0.01 34.2

2.2. Construction Emissions by Year, Unmitigated
Criteria Pollutants (lb/day for daily, ton/yr for annual) and GHGs (lb/day for daily, MT/yr for annual) Year TOG ROG NOx CO SO2 PM10E PM10D PM10T PM2.5E PM2.5D PM2.5T BCO2 NBCO2 CO2T CH4 N2O R CO2e Daily -
Summer
(Max)
— — — — — — — — — — — — — — — — — —
Daily -
Winter
(Max)
— — — — — — — — — — — — — — — — — —
2025 0.73 0.61 5.31 7.16 0.01 0.18 0.91 1.09 0.17 0.11 0.28 — 1,168 1,168 0.05 0.02 0.02 1,177

Halsey House Demolition Project Detailed Report, 3/1/2024 6 / 19
Average
Daily
— — — — — — — — — — — — — — — — — —
2025 0.13 0.11 0.93 1.25 < 0.005 0.03 0.15 0.18 0.03 0.02 0.05 — 205 205 0.01 < 0.005 0.05 207 Annual — — — — — — — — — — — — — — — — — —
2025 0.02 0.02 0.17 0.23 < 0.005 0.01 0.03 0.03 0.01 < 0.005 0.01 — 33.9 33.9 < 0.005 < 0.005 0.01 34.2

3. Construction Emissions Details

3.1. Demolition (2025) - Unmitigated
Criteria Pollutants (lb/day for daily, ton/yr for annual) and GHGs (lb/day for daily, MT/yr for annual) Location TOG ROG NOx CO SO2 PM10E PM10D PM10T PM2.5E PM2.5D PM2.5T BCO2 NBCO2 CO2T CH4 N2O R CO2e Onsite — — — — — — — — — — — — — — — — — —
Daily,
Summer
(Max)
— — — — — — — — — — — — — — — — — —
Daily,
Winter
(Max)
— — — — — — — — — — — — — — — — — —
Off-Road
Equipment

0.68 0.56 5.16 6.67 0.01 0.18 — 0.18 0.17 — 0.17 — 994 994 0.04 0.01 — 997 Demolitio
n
— — — — — — 0.05 0.05 — 0.01 0.01 — — — — — — —
Onsite
truck
< 0.005 < 0.005 0.02 0.01 < 0.005 < 0.005 0.74 0.74 < 0.005 0.07 0.07 — 3.43 3.43 < 0.005 < 0.005 < 0.005 3.62 Average
Daily
— — — — — — — — — — — — — — — — — —
Off-Road
Equipment

0.12 0.10 0.91 1.17 < 0.005 0.03 — 0.03 0.03 — 0.03 — 174 174 0.01 < 0.005 — 175 Demolitio
n
— — — — — — 0.01 0.01 — < 0.005 < 0.005 — — — — — — —
Onsite
truck
< 0.005 < 0.005 < 0.005 < 0.005 < 0.005 < 0.005 0.12 0.12 < 0.005 0.01 0.01 — 0.60 0.60 < 0.005 < 0.005 < 0.005 0.63

Halsey House Demolition Project Detailed Report, 3/1/2024 7 / 19
Annual — — — — — — — — — — — — — — — — — —
Off-Road
Equipment

0.02 0.02 0.17 0.21 < 0.005 0.01 — 0.01 0.01 — 0.01 — 28.9 28.9 < 0.005 < 0.005 — 29.0 Demolitio
n
— — — — — — < 0.005 < 0.005 — < 0.005 < 0.005 — — — — — — — Onsite
truck
< 0.005 < 0.005 < 0.005 < 0.005 < 0.005 < 0.005 0.02 0.02 < 0.005 < 0.005 < 0.005 — 0.10 0.10 < 0.005 < 0.005 < 0.005 0.10 Offsite — — — — — — — — — — — — — — — — — —
Daily,
Summer
(Max)
— — — — — — — — — — — — — — — — — —
Daily,
Winter
(Max)
— — — — — — — — — — — — — — — — — —
Worker 0.04 0.04 0.04 0.44 0.00 0.00 0.10 0.10 0.00 0.02 0.02 — 99.2 99.2 < 0.005 < 0.005 0.01 101 Vendor < 0.005 < 0.005 0.04 0.02 < 0.005 < 0.005 0.01 0.01 < 0.005 < 0.005 < 0.005 — 27.0 27.0 < 0.005 < 0.005 < 0.005 28.2 Hauling < 0.005 < 0.005 0.06 0.03 < 0.005 < 0.005 0.01 0.01 < 0.005 < 0.005 < 0.005 — 44.8 44.8 < 0.005 0.01 < 0.005 47.0 Average
Daily
— — — — — — — — — — — — — — — — — —
Worker 0.01 0.01 0.01 0.08 0.00 0.00 0.02 0.02 0.00 < 0.005 < 0.005 — 17.6 17.6 < 0.005 < 0.005 0.03 17.8 Vendor < 0.005 < 0.005 0.01 < 0.005 < 0.005 < 0.005 < 0.005 < 0.005 < 0.005 < 0.005 < 0.005 — 4.73 4.73 < 0.005 < 0.005 0.01 4.95 Hauling < 0.005 < 0.005 0.01 < 0.005 < 0.005 < 0.005 < 0.005 < 0.005 < 0.005 < 0.005 < 0.005 — 7.85 7.85 < 0.005 < 0.005 0.01 8.24 Annual — — — — — — — — — — — — — — — — — —
Worker < 0.005 < 0.005 < 0.005 0.01 0.00 0.00 < 0.005 < 0.005 0.00 < 0.005 < 0.005 — 2.91 2.91 < 0.005 < 0.005 0.01 2.95 Vendor < 0.005 < 0.005 < 0.005 < 0.005 < 0.005 < 0.005 < 0.005 < 0.005 < 0.005 < 0.005 < 0.005 — 0.78 0.78 < 0.005 < 0.005 < 0.005 0.82 Hauling < 0.005 < 0.005 < 0.005 < 0.005 < 0.005 < 0.005 < 0.005 < 0.005 < 0.005 < 0.005 < 0.005 — 1.30 1.30 < 0.005 < 0.005 < 0.005 1.36

4. Operations Emissions Details

4.10. Soil Carbon Accumulation By Vegetation Type

Halsey House Demolition Project Detailed Report, 3/1/2024 8 / 19

4.10.1. Soil Carbon Accumulation By Vegetation Type - Unmitigated Criteria Pollutants (lb/day for daily, ton/yr for annual) and GHGs (lb/day for daily, MT/yr for annual) Vegetatio
n
TOG ROG NOx CO SO2 PM10E PM10D PM10T PM2.5E PM2.5D PM2.5T BCO2 NBCO2 CO2T CH4 N2O R CO2e Daily,
Summer
(Max)
— — — — — — — — — — — — — — — — — —
Total — — — — — — — — — — — — — — — — — —
Daily,
Winter
(Max)
— — — — — — — — — — — — — — — — — —
Total — — — — — — — — — — — — — — — — — —
Annual — — — — — — — — — — — — — — — — — —
Total — — — — — — — — — — — — — — — — — —

4.10.2. Above and Belowground Carbon Accumulation by Land Use Type - Unmitigated Criteria Pollutants (lb/day for daily, ton/yr for annual) and GHGs (lb/day for daily, MT/yr for annual) Land
Use
TOG ROG NOx CO SO2 PM10E PM10D PM10T PM2.5E PM2.5D PM2.5T BCO2 NBCO2 CO2T CH4 N2O R CO2e Daily,
Summer
(Max)
— — — — — — — — — — — — — — — — — —
Total — — — — — — — — — — — — — — — — — —
Daily,
Winter
(Max)
— — — — — — — — — — — — — — — — — —
Total — — — — — — — — — — — — — — — — — —
Annual — — — — — — — — — — — — — — — — — —
Total — — — — — — — — — — — — — — — — — —

Halsey House Demolition Project Detailed Report, 3/1/2024 9 / 19

4.10.3. Avoided and Sequestered Emissions by Species - Unmitigated Criteria Pollutants (lb/day for daily, ton/yr for annual) and GHGs (lb/day for daily, MT/yr for annual) Species TOG ROG NOx CO SO2 PM10E PM10D PM10T PM2.5E PM2.5D PM2.5T BCO2 NBCO2 CO2T CH4 N2O R CO2e Daily,
Summer
(Max)
— — — — — — — — — — — — — — — — — —
Avoided — — — — — — — — — — — — — — — — — —
Subtotal — — — — — — — — — — — — — — — — — —
Sequest
ered
— — — — — — — — — — — — — — — — — —
Subtotal — — — — — — — — — — — — — — — — — —
Remove
d
— — — — — — — — — — — — — — — — — —
Subtotal — — — — — — — — — — — — — — — — — —
— — — — — — — — — — — — — — — — — — —
Daily,
Winter
(Max)
— — — — — — — — — — — — — — — — — —
Avoided — — — — — — — — — — — — — — — — — —
Subtotal — — — — — — — — — — — — — — — — — —
Sequest
ered
— — — — — — — — — — — — — — — — — —
Subtotal — — — — — — — — — — — — — — — — — —
Remove
d
— — — — — — — — — — — — — — — — — —
Subtotal — — — — — — — — — — — — — — — — — —
— — — — — — — — — — — — — — — — — — —
Annual — — — — — — — — — — — — — — — — — —
Avoided — — — — — — — — — — — — — — — — — —
Subtotal — — — — — — — — — — — — — — — — — —

Halsey House Demolition Project Detailed Report, 3/1/2024 10 / 19
Sequest — — — — — — — — — — — — — — — — — —
Subtotal — — — — — — — — — — — — — — — — — —
Remove
d
— — — — — — — — — — — — — — — — — —
Subtotal — — — — — — — — — — — — — — — — — —
— — — — — — — — — — — — — — — — — — —

5. Activity Data

5.1. Construction Schedule
Phase Name Phase Type Start Date End Date Days Per Week Work Days per Phase Phase Description Demolition Demolition 1/1/2025 3/31/2025 5.00 64.0 Demolition of the Halsey House

5.2. Off-Road Equipment

5.2.1. Unmitigated
Phase Name Equipment Type Fuel Type Engine Tier Number per Day Hours Per Day Horsepower Load Factor Demolition Tractors/Loaders/Backh
oes
Diesel Average 2.00 6.00 84.0 0.37
Demolition Rubber Tired Dozers Diesel Average 1.00 1.00 367 0.40 Demolition Concrete/Industrial
Saws
Diesel Average 1.00 8.00 33.0 0.73
Demolition Excavators Diesel Average 1.00 8.00 36.0 0.38

5.3. Construction Vehicles

5.3.1. Unmitigated

Halsey House Demolition Project Detailed Report, 3/1/2024 11 / 19
Phase Name Trip Type One-Way Trips per Day Miles per Trip Vehicle Mix Demolition — — — —
Demolition Worker 12.5 11.7 LDA,LDT1,LDT2
Demolition Vendor 1.00 8.40 HHDT,MHDT
Demolition Hauling 0.63 20.0 HHDT
Demolition Onsite truck 1.00 0.50 HHDT

5.4. Vehicles

5.4.1. Construction Vehicle Control Strategies
Non-applicable. No control strategies activated by user.

5.5. Architectural Coatings
Phase Name Residential Interior Area Coated
(sq ft)
Residential Exterior Area Coated
(sq ft)
Non-Residential Interior Area
Coated (sq ft)
Non-Residential Exterior Area
Coated (sq ft)
Parking Area Coated (sq ft)

5.6. Dust Mitigation

5.6.1. Construction Earthmoving Activities
Phase Name Material Imported (cy) Material Exported (cy) Acres Graded (acres) Material Demolished (Building Square Footage)
Acres Paved (acres)
Demolition 0.00 0.00 0.00 3,400 —

5.6.2. Construction Earthmoving Control Strategies
Non-applicable. No control strategies activated by user.

5.7. Construction Paving
Land Use Area Paved (acres) % Asphalt
Single Family Housing 0.01 0%

Halsey House Demolition Project Detailed Report, 3/1/2024 12 / 19

5.8. Construction Electricity Consumption and Emissions Factors kWh per Year and Emission Factor (lb/MWh)
Year kWh per Year CO2 CH4 N2O
2025 0.00 204 0.03 < 0.005

5.18. Vegetation

5.18.1. Land Use Change

5.18.1.1. Unmitigated
Vegetation Land Use Type Vegetation Soil Type Initial Acres Final Acres

5.18.1. Biomass Cover Type

5.18.1.1. Unmitigated
Biomass Cover Type Initial Acres Final Acres

5.18.2. Sequestration

5.18.2.1. Unmitigated
Tree Type Number Electricity Saved (kWh/year) Natural Gas Saved (btu/year)

6. Climate Risk Detailed Report

6.1. Climate Risk Summary
Cal-Adapt midcentury 2040–2059 average projections for four hazards are reported below for your project location. These are under Representation Concentration Pathway (RCP) 8.5 which assumes GHG emissions will continue to rise strongly through 2050 and then plateau around 2100.

Halsey House Demolition Project Detailed Report, 3/1/2024 13 / 19
Climate Hazard Result for Project Location Unit
Temperature and Extreme Heat 12.8 annual days of extreme heat Extreme Precipitation 7.75 annual days with precipitation above 20 mm Sea Level Rise — meters of inundation depth
Wildfire 11.1 annual hectares burned
Temperature and Extreme Heat data are for grid cell in which your project are located. The projection is based on the 98th historical percentile of daily maximum/minimum temperatures from observed historical data (32 climate model ensemble from Cal-Adapt, 2040–2059 average under RCP 8.5). Each grid cell is 6 kilometers (km) by 6 km, or 3.7 miles (mi) by 3.7 mi.

Extreme Precipitation data are for the grid cell in which your project are located. The threshold of 20 mm is equivalent to about ¾ an inch of rain, which would be light to moderate rainfall if received over a full day or heavy rain if received over a period of 2 to 4 hours. Each grid cell is 6 kilometers (km) by 6 km, or 3.7 miles (mi) by 3.7 mi.

Sea Level Rise data are for the grid cell in which your project are located. The projections are from Radke et al. (2017), as reported in Cal-Adapt (Radke et al., 2017, CEC-500-2017-008), and consider inundation location and depth for the San Francisco Bay, the Sacramento-San Joaquin River Delta and California coast resulting different increments of sea level rise coupled with extreme storm events.

Users may select from four scenarios to view the range in potential inundation depth for the grid cell. The four scenarios are: No rise, 0.5 meter, 1.0 meter, 1.41 meters Wildfire data are for the grid cell in which your project are located. The projections are from UC Davis, as reported in Cal-Adapt (2040–2059 average under RCP 8.5), and consider historical data of climate, vegetation, population density, and large (> 400 ha) fire history. Users may select from four model simulations to view the range in potential wildfire probabilities for the grid cell. The four simulations make different assumptions about expected rainfall and temperature are: Warmer/drier (HadGEM2-ES), Cooler/wetter (CNRM-CM5), Average conditions (CanESM2), Range of different rainfall and temperature possibilities (MIROC5). Each grid cell is 6 kilometers (km) by 6 km, or 3.7 miles (mi) by 3.7 mi.

6.2. Initial Climate Risk Scores
Climate Hazard Exposure Score Sensitivity Score Adaptive Capacity Score Vulnerability Score Temperature and Extreme Heat N/A N/A N/A N/A
Extreme Precipitation 2 0 0 N/A
Sea Level Rise 1 0 0 N/A
Wildfire 1 0 0 N/A
Flooding N/A N/A N/A N/A
Drought N/A N/A N/A N/A
Snowpack Reduction N/A N/A N/A N/A
Air Quality Degradation 0 0 0 N/A
The sensitivity score reflects the extent to which a project would be adversely affected by exposure to a climate hazard. Exposure is rated on a scale of 1 to 5, with a score of 5 representing the greatest exposure.

The adaptive capacity of a project refers to its ability to manage and reduce vulnerabilities from projected climate hazards. Adaptive capacity is rated on a scale of 1 to 5, with a score of 5 representing the greatest ability to adapt.

The overall vulnerability scores are calculated based on the potential impacts and adaptive capacity assessments for each hazard. Scores do not include implementation of climate risk reduction measures.

Halsey House Demolition Project Detailed Report, 3/1/2024 14 / 19

6.3. Adjusted Climate Risk Scores
Climate Hazard Exposure Score Sensitivity Score Adaptive Capacity Score Vulnerability Score Temperature and Extreme Heat N/A N/A N/A N/A
Extreme Precipitation 2 1 1 3
Sea Level Rise 1 1 1 2
Wildfire 1 1 1 2
Flooding N/A N/A N/A N/A
Drought N/A N/A N/A N/A
Snowpack Reduction N/A N/A N/A N/A
Air Quality Degradation 1 1 1 2
The sensitivity score reflects the extent to which a project would be adversely affected by exposure to a climate hazard. Exposure is rated on a scale of 1 to 5, with a score of 5 representing the greatest exposure.

The adaptive capacity of a project refers to its ability to manage and reduce vulnerabilities from projected climate hazards. Adaptive capacity is rated on a scale of 1 to 5, with a score of 5 representing the greatest ability to adapt.

The overall vulnerability scores are calculated based on the potential impacts and adaptive capacity assessments for each hazard. Scores include implementation of climate risk reduction measures.

6.4. Climate Risk Reduction Measures

7. Health and Equity Details

7.1. CalEnviroScreen 4.0 Scores
The maximum CalEnviroScreen score is 100. A high score (i.e., greater than 50) reflects a higher pollution burden compared to other census tracts in the state.

Indicator Result for Project Census Tract
Exposure Indicators —
AQ-Ozone 14.9
AQ-PM 12.5
AQ-DPM 39.1
Drinking Water 51.4
Lead Risk Housing 27.9

Halsey House Demolition Project Detailed Report, 3/1/2024 15 / 19
Pesticides 40.9
Toxic Releases 40.9
Traffic 80.5
Effect Indicators —
CleanUp Sites 64.7
Groundwater 83.5
Haz Waste Facilities/Generators 59.8
Impaired Water Bodies 23.9
Solid Waste 0.00
Sensitive Population —
Asthma 0.44
Cardio-vascular 1.21
Low Birth Weights 13.9
Socioeconomic Factor Indicators —
Education 8.99
Housing 9.81
Linguistic 29.5
Poverty 7.83
Unemployment 7.77

7.2. Healthy Places Index Scores
The maximum Health Places Index score is 100. A high score (i.e., greater than 50) reflects healthier community conditions compared to other census tracts in the state.

Indicator Result for Project Census Tract
Economic —
Above Poverty 98.54998075
Employed 35.60887976
Median HI 99.88451174

Halsey House Demolition Project Detailed Report, 3/1/2024 16 / 19
Education —
Bachelor's or higher 99.97433594
High school enrollment 100
Preschool enrollment 95.7141024
Transportation —
Auto Access 90.86359553
Active commuting 67.58629539
Social —
2-parent households 95.67560631
Voting 94.75170024
Neighborhood —
Alcohol availability 91.55652509
Park access 22.12241755
Retail density 27.98665469
Supermarket access 21.22417554
Tree canopy 96.86898499
Housing —
Homeownership 92.89105608
Housing habitability 97.51058642
Low-inc homeowner severe housing cost burden 81.32939818 Low-inc renter severe housing cost burden 92.05697421
Uncrowded housing 96.93314513
Health Outcomes —
Insured adults 99.34556653
Arthritis 0.0
Asthma ER Admissions 99.5
High Blood Pressure 0.0

Halsey House Demolition Project Detailed Report, 3/1/2024 17 / 19
Cancer (excluding skin) 0.0
Asthma 0.0
Coronary Heart Disease 0.0
Chronic Obstructive Pulmonary Disease 0.0
Diagnosed Diabetes 0.0
Life Expectancy at Birth 96.9
Cognitively Disabled 78.9
Physically Disabled 89.8
Heart Attack ER Admissions 98.9
Mental Health Not Good 0.0
Chronic Kidney Disease 0.0
Obesity 0.0
Pedestrian Injuries 19.6
Physical Health Not Good 0.0
Stroke 0.0
Health Risk Behaviors—
Binge Drinking 0.0
Current Smoker 0.0
No Leisure Time for Physical Activity 0.0
Climate Change Exposures—
Wildfire Risk 0.0
SLR Inundation Area 0.0
Children 87.0
Elderly 7.7
English Speaking 86.8
Foreign-born 55.8
Outdoor Workers 81.0

Halsey House Demolition Project Detailed Report, 3/1/2024 18 / 19
Climate Change Adaptive Capacity —
Impervious Surface Cover 91.2
Traffic Density 73.2
Traffic Access 49.4
Other Indices —
Hardship 0.7
Other Decision Support —
2016 Voting 93.8

7.3. Overall Health & Equity Scores
Metric Result for Project Census Tract
CalEnviroScreen 4.0 Score for Project Location (a) 3.00 Healthy Places Index Score for Project Location (b) 100 Project Located in a Designated Disadvantaged Community (Senate Bill 535) No Project Located in a Low-Income Community (Assembly Bill 1550) No Project Located in a Community Air Protection Program Community (Assembly Bill 617) No a: The maximum CalEnviroScreen score is 100. A high score (i.e., greater than 50) reflects a higher pollution burden compared to other census tracts in the state. b: The maximum Health Places Index score is 100. A high score (i.e., greater than 50) reflects healthier community conditions compared to other census tracts in the state.

7.4. Health & Equity Measures
No Health & Equity Measures selected.

7.5. Evaluation Scorecard
Health & Equity Evaluation Scorecard not completed.

7.6. Health & Equity Custom Measures
No Health & Equity Custom Measures created.

8. User Changes to Default Data

Halsey House Demolition Project Detailed Report, 3/1/2024 19 / 19
Screen Justification
Construction: Construction Phases Project would include only the demolition of the existing Halsey House. Demolition activities would last approximately three months.

Construction: Off-Road Equipment Keeping default tractor/loader/backhoe, rubber tired dozer, and concrete/industrial saw engine tier and hours/day. Added excavator for 8 hours a day.

983 University Avenue, Building D  Los Gatos, CA 95032  408.458.3200  www.harveyecology.com Halsey House Demolition Project
Biological Resources Report
Project #4814-01
Prepared for:

Mimi McNamara
David J. Powers & Associates
1871 The Alameda, Suite 200
San José, CA 95126
Prepared by:

H. T. Harvey & Associates
August 2, 2024
Attachment 4 - Appendix C

Halsey House Demolition Project
Biological Resources Report
ii H. T. Harvey & Associates
August 2, 2024
Table of Contents
Section 1. Introduction......................................................................................................................................... 1

1.1 Project Location ...................................................................................................................................................... 1

1.2 Project Description ................................................................................................................................................. 1

1.1.1 Background ...................................................................................................................................................... 1

1.1.2 Demolition Details.......................................................................................................................................... 1 Section 2. Methods................................................................................................................................................ 5

2.1 Background Review ................................................................................................................................................ 5

2.2 Site Visit.................................................................................................................................................................... 5 Section 3. Regulatory Setting............................................................................................................................... 6

3.1 Federal Regulations................................................................................................................................................. 6

3.1.1 Clean Water Act............................................................................................................................................... 6

3.1.2 Rivers and Harbors Act.................................................................................................................................. 6

3.1.3 Federal Endangered Species Act .................................................................................................................. 7

3.1.4 Federal Migratory Bird Treaty Act ............................................................................................................... 8

3.2 State Regulations...................................................................................................................................................... 8

3.2.1 Porter-Cologne Water Quality Control Act................................................................................................ 8

3.2.2 California Endangered Species Act.............................................................................................................. 9

3.2.3 Native Plant Protection Act .......................................................................................................................... 9

3.2.4 California Environmental Quality Act......................................................................................................... 9

3.2.5 California Fish and Game Code .................................................................................................................11

3.2.6 State Water Resources Control Board Stormwater Regulation .............................................................12

3.3 Local Regulations ..................................................................................................................................................13

3.3.1 Los Altos Tree Protection Ordinance........................................................................................................13

3.3.2 Los Altos Watercourse Protection Regulations........................................................................................14 Section 4. Environmental Setting .....................................................................................................................15

4.1 General Project Area Description ......................................................................................................................15

4.2 Biotic Habitats .......................................................................................................................................................15

4.2.1 Developed ......................................................................................................................................................15

4.2.2 Coast Live Oak Woodland ..........................................................................................................................18

4.3 Adjacent Habitat Areas.........................................................................................................................................19

4.4 Wildlife Movement................................................................................................................................................20 Section 5. Special-Status Species and Sensitive Habitats ..............................................................................21

5.1 Special-Status Plant Species.................................................................................................................................24

5.2 Special-Status Animal Species .............................................................................................................................26

5.3 Sensitive Natural Communities, Vegetation Alliances, and Habitats............................................................37

5.3.1 Sensitive Natural Communities...................................................................................................................37

5.3.2 Sensitive Vegetation Alliances.....................................................................................................................38

5.3.3 CDFW Riparian Habitat ..............................................................................................................................38

5.3.4 Sensitive Habitats (Waters of the U.S./State)...........................................................................................38

5.3.5 Nonnative and Invasive Species .................................................................................................................38 Section 6. Impacts and Mitigation Measures..................................................................................................39

6.1 Impacts on Special-Status Species......................................................................................................................40

6.1.1 Impacts on Regionally Common Habitats and Associated Common Plant and Wildlife Species (Less than Significant)............................................................................................................................................40

6.1.2 Impacts on Water Quality and Special-Status Fish (Less than Significant) .........................................40

Halsey House Demolition Project
Biological Resources Report
iii H. T. Harvey & Associates
August 2, 2024

6.1.3 Impacts on Nonbreeding Special-Status Invertebrates, Birds, and Mammals (Less than Significant) ....................................................................................................................................................................................41

6.1.4 Impacts on the White-Tailed Kite, Vaux’s Swift, and Yellow Warbler (Less than Significant) .......42

6.1.5 Impacts on the San Francisco Dusky-Footed Woodrat (Less than Significant with Mitigation).....42

6.1.6 Impacts on California Giant Salamander (Less than Significant)..........................................................44

6.1.7 Impacts on Common and Special-Status Roosting Bats (Less than Significant with Mitigation)....44

6.2 Impacts on Sensitive Communities....................................................................................................................45

6.2.1 Impacts on Riparian Habitat or Other Sensitive Natural Communities (Less than Significant)......45

6.3 Impacts on Wetlands............................................................................................................................................46

6.4 Impacts on Wildlife Movement ..........................................................................................................................46

6.4.1 Impacts on Wildlife Movement (Less than Significant)..........................................................................46

6.5 Impacts due to Conflicts with Local Policies:...................................................................................................47

6.5.1 Impacts Due to the Removal of Ordinance-Sized Trees (Less than Significant)...............................47

6.5.2 Impacts Due to Encroachment into the Stream/Riparian Corridor (Less than Significant)............47

6.6 Impacts due to Conflicts with an Adopted Habitat Conservation Plan.......................................................48

6.7 Cumulative Impacts..............................................................................................................................................49 Section 7. Compliance with Additional Laws and Regulations for Nesting Birds....................................50 Section 8. References..........................................................................................................................................51 Figures
Figure 1. Vicinity Map.................................................................................................................................................... 3 Figure 2. Project Site ...................................................................................................................................................... 4 Figure 3. Biotic Habitats..............................................................................................................................................16 Figure 4. CNDDB-Mapped Records of Special-Status Plants..............................................................................22 Figure 5. CNDDB-Mapped Records of Special-Status Animals..........................................................................23 Tables
Table 1. Special-Status Plant Species, Their Status, and Potential for Occurrence on the Project Site ........25 Table 2. Special-Status Animal Species, Their Status, and Potential for Occurrence on the Project Site ....28 Appendices
Appendix A. Plants Observed..............................................................................................................................A-1 Appendix B. Special-Status Plants Considered but Rejected for Occurrence..............................................B-1

Halsey House Demolition Project
Biological Resources Report
iv H. T. Harvey & Associates
August 2, 2024
List of Preparers
Steve Rottenborn, Ph.D., Principal/Senior Wildlife Ecologist Kelly Hardwicke, Ph.D., Principal/Senior Plant and Wetlands Ecologist Robin Carle, M.S., Project Manager/Senior Wildlife Ecologist Vanessa Morales, B.S., Plant and Wetlands Ecologist
Zachary Hampson, B.A., Wildlife Ecologist
Emily Malkauskas, B.S., Wildlife Ecologist

Halsey House Demolition Project
Biological Resources Report
1 H. T. Harvey & Associates
August 2, 2024
Section 1. Introduction
This report describes the biological resources present in the area of the proposed Halsey House Demolition project, the potential impacts of the proposed project on biological resources, and measures necessary to reduce project impacts to less-than-significant levels under the California Environmental Quality Act (CEQA). This assessment is based on the project maps and description provided to H. T. Harvey & Associates by David J.

Powers & Associates through July 2024.

1.1 Project Location
The 0.6-acre project site is located within the Redwood Grove Nature Preserve in Los Altos, California (Figures 1 and 2). The Preserve is surrounded by residential development, with University Avenue located to the east, Manresa Lane to the south, Lennox Way and Fremont Road to the west, and Shoup Park to the north. The project site is located on the Cupertino, California 7.5-minute United States Geological Survey (USGS) quadrangle.

1.2 Project Description

1.1.1 Background
The Halsey House was built in 1923 and used as a private residence until the property was purchased by the City of Los Altos in 1974 to serve as a park. The building was then converted to a nature center for educational and recreational programming. In 2008, the building was closed to the public. Since 2008, the Halsey House has remained vacant and unused. The Halsey House is a local Historic Landmark and is eligible for the California Register of Historic Resources. As a result, it is considered a historic resource under CEQA.

1.1.2 Demolition Details
The project proposes to demolish the Halsey House building. Demolition activities would occur within an approximately 0.6-acre area surrounding the building and would last roughly three months. Equipment and workers would access the site via the Redwood Grove Nature Preserve entrance on University Avenue.

Equipment staging would occur within the proposed area of disturbance.

Demolition equipment, such as an excavator and a compact track loader, would be utilized throughout the demolition period. Due to the weight capacity and width of the pedestrian bridge (approximately 8 tons and 10 feet, respectively), the equipment used for demolition would be small and lightweight. For example, the compact track loader would weigh 7 tons and the excavator would weigh 6 tons.

Service utility trucks weighing about 4 tons would be used for hauling. The service trucks would be able to hold a maximum of 3 tons. When hauling materials off-site the service utility trucks would weigh 7 tons total.

Halsey House Demolition Project
Biological Resources Report
2 H. T. Harvey & Associates
August 2, 2024
During demolition, construction equipment and manual labor would be used to tear down the Halsey House structure. Some of the demolition would be completed manually with hand tools due to the weight and width constraints of the pedestrian bridge. After demolition of the building, the site would be cleared and building materials would be hauled to an appropriate off-site disposal location. Some tree trimming and/or removal may be necessary to allow for demolition of the building.

Pine Ln
Esther Clark
Park
Manuella
R
d
W Fremont Rd
La
Paloma
Rd
Ro
bleda
Rd
Chapin Rd
Miranda Rd
s Altos Hills
280
C ollege Loop Rd
Ok eefe Ln
Elena Rd
tamont Rd
Moody Rd
Josefa Ln
Adobe Ln
Foothill College
Foothills
Distel Dr
Jardin Dr
Pine Ln
Los
Ninos
Way
Yerba Santa Ave
Casita
Way
Solana Dr
Arbuelo Way
Valencia Dr
Lincoln Ave
Los Altos Ave W Edith Ave
Lyell S t
Cuesta Dr
Hawthorne Ave
Plaza N
Pepper Dr
Merrit t Rd
Galli Dr
E Edith Ave
Doud Dr
Tyndall S t
Palm Ave
Solana Dr
S El Monte
Ave
S San Antonio Rd
Redwood Grove
Nature Preserve
Lincoln Park
Covington
School
Los Altos High
School
Hillview School
North
Los Altos
280
El M onte Rd
Covington Rd
Dian
ne
Dr
Summerhill Ave
Voorhees Dr
Border Rd
Valley View D r
S El Monte Ave
Magdalena Ave
Foothill Expy
Saint Nicholas
School
Marich Wa
Ca
mpbell Ave
Rosita Ave S Clark Ave Arboleda D
Springe
Camellia
Paco Dr
Campbell Ave
Echo
Dr
Fairway
Dr
Los Altos
Christian Hig
School
Country
^_
^_
^_
^_
^_ ^_
^_
^_
^_
^_
^_
^_
SONOMA
MARIN

CONTRA COSTA

SANTA CLARA

ALAMEDA

STANISLAUS

SANTA CRUZ
San Rafael
Martinez
Oakland
Stockton
Redwood City
San Jose
Santa Cruz
Hollister
Salinas
N:\Projects4800\4814-01\Reports\BRR\BRR.aprx
1,500 750 0 1,500 ± US Feet
Halsey House Demolition Project Biological Resources Report (4814-01) August 2024
Figure 1. Vicinity Map
Project
Vicinity
California
Project Location Adobe
Creek

Manresa Ln
N:\Projects4800\4814-01\Reports\BRR\BRR.aprx
60 30 0 60
±
Feet
Project Site
Figure 2. Project Site
Halsey House Demolition Project Biological Resources Report (4814-01) August 2024
Adobe Creek

Halsey House Demolition Project
Biological Resources Report
5 H. T. Harvey & Associates
August 2, 2024
Section 2. Methods

2.1 Background Review
Prior to conducting field work, H. T. Harvey & Associates ecologists reviewed the project description and site plan provided by David J. Powers & Associates through July 2024; aerial images (Google Inc. 2024); a USGS topographic map; a National Wetlands Inventory map (2024); National Resources Conservation Service (NRCS) soil survey maps (2024); the California Department of Fish and Wildlife’s (CDFW’s) California Natural Diversity Database (CNDDB) (2024); and other relevant reports, scientific literature, and technical databases.

For the purposes of this report, the project vicinity is defined as the area within a 5-mile radius surrounding the project site.

In addition, for plants, we reviewed all species on current California Native Plant Society (CNPS) California Rare Plant Rank (CRPR) 1A, 1B, 2A, 2B, 3, and 4 lists (CNPS 2024) occurring in the project region, which is defined as the Cupertino, California USGS 7.5-minute quadrangle and surrounding eight quadrangles (Palo Alto, Mountain View, Milpitas, San Jose West, Mindego Hill, Big Basin, Castle Rock Ridge, and Los Gatos). In addition, we queried the CNDDB (2024) for natural communities of special concern that occur on the project site, and we perused records of birds reported in nearby areas, such as at Redwood Grove Nature Preserve and Shoup Park, on eBird (Cornell Lab of Ornithology 2024) and on the Peninsula-Birding List Serve (2024).

2.2 Site Visit
H. T. Harvey & Associates plant and wetland ecologist Vanessa Morales, B.S., and wildlife ecologist Zachary Hampson, B.A., conducted a reconnaissance-level survey of the project site on May 7, 2024. The purpose of the surveys was to provide an impact assessment specific to the proposed construction of the project, as described above. Specifically, surveys were conducted to (1) assess existing biotic habitats and plant and animal communities on the project site, (2) assess the project site for its potential to support special-status species and their habitats, and (3) identify potential jurisdictional and sensitive habitats, such as waters of the U.S./state and riparian habitat. V. Morales conducted a focused presence/absence survey for bent-flowered fiddleneck (Amsinkia lunaris), arcuate bush mallow (Malacothamnus arcuatus var. arcuatus), Dudley’s lousewort (Pedicularis dudleya), and California bottlebrush (Elymus californicus), four special-status plants that were thought to have some potential for occurrence and that would have been detectable during the May 7 site visit, on the project site. Z.

Hampson conducted a focused survey for roosting bats and signs of bat presence (e.g., guano and urine staining) in the existing Halsey House structure as well as in trees on the site, as well as a focused survey for nests of the San Francisco dusky-footed woodrat (Neotoma fuscipes annectens). In addition, Z. Hampson and H. T. Harvey & Associates wildlife ecologist Emily Malkauskas, B.S., returned to the site on May 16, 2024, to conduct a dusk emergence survey for roosting bats.

Halsey House Demolition Project
Biological Resources Report
6 H. T. Harvey & Associates
August 2, 2024
Section 3. Regulatory Setting
Biological resources on the project site are regulated by a number of federal, state, and local laws and ordinances, as described below.

3.1 Federal Regulations

3.1.1 Clean Water Act
The Clean Water Act (CWA) functions to maintain and restore the physical, chemical, and biological integrity of waters of the U.S., which include, but are not limited to, tributaries to traditionally navigable waters currently or historically used for interstate or foreign commerce, and adjacent wetlands. Historically, in non-tidal waters, U.S. Army Corps of Engineers (USACE) jurisdiction extends to the ordinary high water (OHW) mark, which is defined in Title 33, Code of Federal Regulations, Part 328.3. If there are wetlands adjacent to channelized features, the limits of USACE jurisdiction extend beyond the OHW mark to the outer edges of the wetlands.

In tidal waters, USACE jurisdiction extends to the landward extent of vegetation associated with salt or brackish water or the high tide line. The high tide line is defined in 33 Code of Federal Regulations Part 328.3 as “the line of intersection of the land with the water’s surface at the maximum height reached by a rising tide.” The May 25, 2023 U.S. Supreme Court decision in Sackett v. Environmental Protection Agency limited the definition of waters of the U.S. by including only wetlands that have a continuous surface connection with traditional navigable waters. On August 29, 2023, the U.S. Environmental Protection Agency and USACE issued a final implementing rule to amend the definition of waters of the U.S. to conform with the Sackett decision.

Construction activities within jurisdictional waters are regulated by the USACE. The placement of fill into such waters must comply with permit requirements of the USACE. No USACE permit will be effective in the absence of Section 401 Water Quality Certification. The State Water Resources Control Board (SWRCB) is the state agency (together with the Regional Water Quality Control Boards [RWQCBs]) charged with implementing water quality certification in California.

Project Applicability: The project site does not support wetland or aquatic habitats. Adobe Creek, located approximately 16 feet off-site to the northeast, is considered jurisdictional waters of the U.S. under the CWA, but no project activities are proposed within the bed and banks of the creek. As a result, a permit from the USACE would not be required for the project.

3.1.2 Rivers and Harbors Act
Section 10 of the Rivers and Harbors Act of 1899 prohibits the creation of any obstruction to the navigable capacity of waters of the U.S., including discharge of fill and the building of any wharfs, piers, jetties, and other structures without Congressional approval or authorization by the Chief of Engineers and Secretary of the Army (33 U.S.C. 403).

Halsey House Demolition Project
Biological Resources Report
7 H. T. Harvey & Associates
August 2, 2024
Navigable waters of the U.S., which are defined in 33 CFR, Part 329.4, include all waters subject to the ebb and flow of the tide, and/or those which are presently or have historically been used to transport commerce. The shoreward jurisdictional limit of tidal waters is further defined in 33 CFR, Part 329.12 as “the line on the shore reached by the plane of the mean (average) high water.” It is important to understand that the USACE does not regulate wetlands under Section 10, only the aquatic or open waters component of bay habitat, and that there is overlap between Section 10 jurisdiction and Section 404 jurisdiction. According to 33 CFR, Part 329.9, a waterbody that was once navigable in its natural or improved state retains its character as “navigable in law” even though it is not presently used for commerce as a result of changed conditions and/or the presence of obstructions. Historical Section 10 waters may occur behind levees in areas that are not currently exposed to tidal or muted-tidal influence, and meet the following criteria: (1) the area is presently at or below the mean high water line; (2) the area was historically at or below mean high water in its “unobstructed, natural state”; and (3) there is no evidence that the area was ever above mean high water.

As mentioned above, Section 404 of the CWA authorizes the USACE to issue permits to regulate the discharge of dredged or fill material into waters of the U.S. If a project also proposes to discharge dredged or fill material and/or introduce other potential obstructions in navigable waters of the U.S., a Letter of Permission authorizing these impacts must be obtained from the USACE under Section 10 of the Rivers and Harbors Act.

Project Applicability: No current or historical Section 10 Waters are present on or close to the project site, including in Adobe Creek located off-site to the northeast. Therefore, a Letter of Permission from the USACE is not required.

3.1.3 Federal Endangered Species Act
The Federal Endangered Species Act (FESA) protects federally listed wildlife species from harm or take, which is broadly defined as “to harass, harm, pursue, hunt, shoot, wound, kill, trap, capture, collect, or attempt to engage in any such conduct.” Take can also include habitat modification or degradation that directly results in death or injury of a listed wildlife species. An activity can be defined as take even if it is unintentional or accidental. Listed plant species are provided less protection than listed wildlife species. Listed plant species are legally protected from take under the FESA only if they occur on federal lands.

The U.S. Fish and Wildlife Service (USFWS) and the National Marine Fisheries Service have jurisdiction over federally listed, threatened, and endangered species under FESA. The USFWS also maintains lists of proposed and candidate species. Species on these lists are not legally protected under FESA, but may become listed in the near future and are often included in their review of a project.

Project Applicability: The May 2024 site visit determined that no federally listed plant species are present on the project site. The monarch butterfly (Danaus plexippus), a candidate for listing under FESA, may occur on the project site as an occasional nonbreeding forager or dispersant, but it is not expected to breed on the project

Halsey House Demolition Project
Biological Resources Report
8 H. T. Harvey & Associates
August 2, 2024
site or to be impacted substantively by the project. No additional federally listed or candidate plant or animal species occur or potentially occur on the project site.

3.1.4 Federal Migratory Bird Treaty Act
The federal Migratory Bird Treaty Act (MBTA), 16 U.S.C. Section 703, prohibits killing, possessing, or trading of migratory birds except in accordance with regulations prescribed by the Secretary of the Interior. The MBTA protects whole birds, parts of birds, and bird eggs and nests, and it prohibits the possession of all nests of protected bird species whether they are active or inactive. An active nest is defined as having eggs or young, as described by the USFWS in its June 14, 2018 memorandum “Destruction and Relocation of Migratory Bird Nest Contents”. Nest starts (nests that are under construction and do not yet contain eggs) and inactive nests are not protected from destruction.

Project Applicability: All native bird species that occur on the project site are protected under the MBTA.

3.2 State Regulations

3.2.1 Porter-Cologne Water Quality Control Act
The SWRCB works in coordination with the nine RWQCBs to preserve, protect, enhance, and restore water quality. Each RWQCB makes decisions related to water quality for its region, and may approve, with or without conditions, or deny projects that could affect waters of the state. Their authority comes from the CWA and the Porter-Cologne Water Quality Control Act (Porter-Cologne). Porter-Cologne broadly defines waters of the state as “any surface water or groundwater, including saline waters, within the boundaries of the state.” Because Porter-Cologne applies to any water, whereas the CWA applies only to certain waters, California’s jurisdictional reach overlaps and may exceed the boundaries of waters of the U.S. For example, Water Quality Order No. 2004-0004-DWQ states that “shallow” waters of the state include headwaters, wetlands, and riparian areas.

Moreover, the San Francisco Bay Region RWQCB’s Assistant Executive Director has stated that, in practice, the RWQCBs claim jurisdiction over riparian areas. Where riparian habitat is not present, such as may be the case at headwaters, jurisdiction is taken to the top of bank.

On April 2, 2019, the SWRCB adopted the State Wetland Definition and Procedures for Discharges of Dredged or Fill Material to Waters of the State. In these new guidelines, riparian habitats are not specifically described as waters of the state but instead as important buffer habitats to streams that do conform to the State Wetland Definition.

The Procedures describe riparian habitat buffers as important resources that may both be included in required mitigation packages for permits for impacts to waters of the state, as well as areas requiring permit authorization from the RWQCBs to impact.

Pursuant to the CWA, projects that are regulated by the USACE must also obtain a Section 401 Water Quality Certification permit from the RWQCB. This certification ensures that a proposed project will uphold state water quality standards. Because California’s jurisdiction to regulate its water resources is much broader than

Halsey House Demolition Project
Biological Resources Report
9 H. T. Harvey & Associates
August 2, 2024
that of the federal government, proposed impacts on waters of the state require Water Quality Certification even if the area occurs outside of USACE jurisdiction. Moreover, the RWQCB may impose mitigation requirements even if the USACE does not. Under the Porter-Cologne, the SWRCB and the nine regional boards also have the responsibility of granting CWA National Pollutant Discharge Elimination System (NPDES) permits and Waste Discharge Requirements for certain point-source and non-point discharges to waters. These regulations limit impacts on aquatic and riparian habitats from a variety of urban sources.

Project Applicability: No waters of the state or riparian habitats regulated by the RWQCB are present on the project site. Adobe Creek located off-site to the northeast is considered waters of the state, but no impacts to this creek will result from project activities. Therefore, a Section 401 permit or Waste Discharge Requirement from the RWQCB would not be required.

3.2.2 California Endangered Species Act
The California Endangered Species Act (CESA) (California Fish and Game Code, Chapter 1.5, Sections 2050- 2116) prohibits the take of any plant or animal listed or proposed for listing as rare (plants only), threatened, or endangered. In accordance with CESA, the CDFW has jurisdiction over state-listed species (Fish and Game Code 2070). The CDFW regulates activities that may result in take of individuals (i.e., “hunt, pursue, catch, capture, or kill, or attempt to hunt, pursue, catch, capture, or kill”). Habitat degradation or modification is not expressly included in the definition of take under the California Fish and Game Code. The CDFW, however, has interpreted take to include the “killing of a member of a species which is the proximate result of habitat modification.”
Project Applicability: The May 2024 site visit determined that no state-listed plant species occur on the project site. The mountain lion (Puma concolor), a candidate for listing under CESA, may occur on the site occasionally as a nonbreeder, but no impacts to individuals will result from the project.

3.2.3 Native Plant Protection Act
The Native Plant Protection Act (NPPA), enacted in 1977, allows plants to be designated as rare or endangered by the California Fish and Game Commission (Fish and Game Code Sections 1900–1913). The NPPA includes prohibitions on the take of such plants, with exceptions for certain activities. A total of 64 species, subspecies, and varieties of plants are considered “rare” by the NPPA.

Project Applicability: The May 2024 site visit determined that no NPPA-designated rare plant species occur on the project site.

3.2.4 California Environmental Quality Act
CEQA is a state law that requires state and local agencies to document and consider the environmental implications of their actions and to refrain from approving projects with significant environmental effects if there are feasible alternatives or mitigation measures that can substantially lessen or avoid those effects. CEQA

Halsey House Demolition Project
Biological Resources Report
10 H. T. Harvey & Associates
August 2, 2024
requires the full disclosure of the environmental effects of agency actions, such as approval of a general plan update or the projects covered by that plan, on resources such as air quality, water quality, cultural resources, and biological resources. The State Resources Agency promulgated guidelines for implementing CEQA known as the State CEQA Guidelines.

Section 15380(b) of the State CEQA Guidelines provides that a species not listed on the federal or state lists of protected species may be considered rare if the species can be shown to meet certain specified criteria. These criteria have been modeled after the definitions in the FESA and the CESA and the section of the California Fish and Game Code dealing with rare or endangered plants and animals. This section was included in the guidelines primarily to deal with situations in which a public agency is reviewing a project that may have a significant effect on a species that has not yet been listed by either the USFWS or CDFW or species that are locally or regionally rare.

The CDFW has produced three lists (amphibians and reptiles, birds, and mammals) of “species of special concern” that serve as “watch lists”. Species on these lists are of limited distribution or the extent of their habitats has been reduced substantially, such that threat to their populations may be imminent. Thus, their populations should be monitored. They may receive special attention during environmental review as potential rare species, but do not have specific statutory protection. All potentially rare or sensitive species, or habitats capable of supporting rare species, are considered for environmental review per the CEQA Section 15380(b).

The CNPS, a non-governmental conservation organization, has developed CRPRs for plant species of concern in California in the CNPS Inventory of Rare and Endangered Plants (CNPS 2024). The CRPRs include lichens, vascular, and non-vascular plants, and are defined as follows:
• CRPR 1A Plants considered extinct.
• CRPR 1B Plants rare, threatened, or endangered in California and elsewhere. • CRPR 2A Plants considered extinct in California but more common elsewhere. • CRPR 2B Plants rare, threatened, or endangered in California but more common elsewhere. • CRPR 3 Plants about which more information is needed - review list. • CRPR 4 Plants of limited distribution-watch list.

The CRPRs are further described by the following threat code extensions:
• .1—seriously endangered in California;
• .2—fairly endangered in California;
• .3—not very endangered in California.

Although the CNPS is not a regulatory agency and plants on these lists have no formal regulatory protection, plants appearing as CRPR 1B or 2 are, in general, considered to meet CEQA’s Section 15380 criteria, and

Halsey House Demolition Project
Biological Resources Report
11 H. T. Harvey & Associates
August 2, 2024
adverse effects to these species may be considered significant. Impacts on plants that are listed by the CNPS on CRPR 3 or 4 are also considered during CEQA review, although because these species are typically not as rare as those of CRPR 1B or 2, impacts on them are less frequently considered significant.

Compliance with CEQA Guidelines Section 15065(a) requires consideration of natural communities of special concern, in addition to plant and wildlife species. Vegetation types of “special concern” are tracked in Rarefind (CNDDB 2024). Further, the CDFW ranks sensitive vegetation alliances based on their global (G) and state (S) rankings analogous to those provided in the CNDDB. Global rankings (G1–G5) of natural communities reflect the overall condition (rarity and endangerment) of a habitat throughout its range, whereas S rankings are a reflection of the condition of a habitat within California. If an alliance is marked as a G1–G3, all of the associations within it would also be of high priority. The CDFW provides the Vegetation Classification and Mapping Program’s (VegCAMP’s) currently accepted list of vegetation alliances and associations (CDFW 2024).

Project Applicability: All potential impacts on biological resources will be considered during CEQA review of the project in the context of this biological resources report. Project impacts are discussed in Section 6 below.

3.2.5 California Fish and Game Code
Ephemeral and intermittent streams, rivers, creeks, dry washes, sloughs, blue line streams on USGS maps, and watercourses with subsurface flows fall under CDFW jurisdiction. Canals, aqueducts, irrigation ditches, and other means of water conveyance may also be considered streams if they support aquatic life, riparian vegetation, or stream-dependent terrestrial wildlife. A stream is defined in Title 14, California Code of Regulations Section 1.72, as “a body of water that follows at least periodically or intermittently through a bed or channel having banks and that supports fish and other aquatic life. This includes watercourses having surface or subsurface flow that supports or has supported riparian vegetation.” Using this definition, CDFW extends its jurisdiction to encompass riparian habitats that function as a part of a watercourse. California Fish and Game Code Section 2786 defines riparian habitat as “lands which contain habitat which grows close to and which depends upon soil moisture from a nearby freshwater source.” The lateral extent of a stream and associated riparian habitat that would fall under the jurisdiction of CDFW can be measured in several ways, depending on the particular situation and the type of fish or wildlife at risk. At minimum, CDFW would claim jurisdiction over a stream’s bed and bank. Where riparian habitat is present, the outer edge of riparian vegetation is generally used as the line of demarcation between riparian and upland habitats.

Pursuant to California Fish and Game Code Section 1603, CDFW regulates any project proposed by any person that will “substantially divert or obstruct the natural flow or substantially change the bed, channel, or bank of any river, stream, or lake designated by the department, or use any material from the streambeds.” California Fish and Game Code Section 1602 requires an entity to notify CDFW of any proposed activity that may modify a river, stream, or lake. If CDFW determines that proposed activities may substantially adversely affect fish and wildlife resources, a Lake and Streambed Alteration Agreement (LSAA) must be prepared. The LSAA sets

Halsey House Demolition Project
Biological Resources Report
12 H. T. Harvey & Associates
August 2, 2024
reasonable conditions necessary to protect fish and wildlife, and must comply with CEQA. The applicant may then proceed with the activity in accordance with the final LSAA.

Certain sections of the California Fish and Game Code describe regulations pertaining to protection of certain wildlife species. For example, Code Section 2000 prohibits take of any bird, mammal, fish, reptile, or amphibian except as provided by other sections of the code.

The California Fish and Game Code Sections 3503, 3513, and 3800 (and other sections and subsections) protect native birds, including their nests and eggs, from all forms of take. Disturbance that causes nest abandonment and/or loss of reproductive effort is considered take by the CDFW. Raptors (e.g., eagles, hawks, and owls) and their nests are specifically protected in California under Code Section 3503.5. Section 3503.5 states that it is “unlawful to take, possess, or destroy any birds in the order Falconiformes or Strigiformes (birds of prey) or to take, possess, or destroy the nest or eggs of any such bird except as otherwise provided by this code or any regulation adopted pursuant thereto.”
Bats and other non-game mammals are protected by California Fish and Game Code Section 4150, which states that all non-game mammals or parts thereof may not be taken or possessed except as provided otherwise in the code or in accordance with regulations adopted by the commission. Activities resulting in mortality of nongame mammals (e.g., destruction of an occupied nonbreeding bat roost, resulting in the death of bats), or disturbance that causes the loss of a maternity colony of bats (resulting in the death of young), may be considered take by the CDFW.

Project Applicability: No riparian habitat regulated by the CDFW occurs on the project site. Adobe Creek and associated riparian habitat located off-site to the northeast is regulated by CDFW, but no impacts to riparian habitat along this creek will result from activities under the project. Therefore, a CDFW LSAA would not be required for the project.

Most native bird, mammal, and other wildlife species that occur on the project site and in the immediate vicinity are protected under the California Fish and Game Code. Project impacts on these species are discussed in Section 6.

3.2.6 State Water Resources Control Board Stormwater Regulation Construction Phase. Construction projects in California causing land disturbances that are equal to 1 acre or greater must comply with state requirements to control the discharge of stormwater pollutants under the NPDES General Permit for Storm Water Discharges Associated with Construction and Land Disturbance Activities (Construction General Permit; Water Board Order No. 2009-0009-DWQ, as amended and administratively extended). Prior to the start of construction/demolition, a Notice of Intent must be filed with the SWRCB describing the project. A Storm Water Pollution Prevention Plan must be developed and maintained during the project and it must include the use of best management practices (BMPs) to protect water quality until the site is stabilized.

Halsey House Demolition Project
Biological Resources Report
13 H. T. Harvey & Associates
August 2, 2024
Standard permit conditions under the Construction General Permit requires that the applicant utilize various measures including: on-site sediment control BMPs, damp street sweeping, temporary cover of disturbed land surfaces to control erosion during construction, and utilization of stabilized construction entrances and/or wash racks, among other factors. Additionally, the Construction General Permit does not extend coverage to projects if stormwater discharge-related activities are likely to jeopardize the continued existence, or result in take of any federally listed endangered or threatened species.

Post-Construction Phase. In many Bay Area counties, including Santa Clara County, projects must also comply with the California RWQCB, San Francisco Bay Region, Municipal Regional Stormwater NPDES Permit (Water Board Order No. R2-2015-0049, as amended). This permit requires that all projects implement BMPs and incorporate Low Impact Development practices into the design that prevent stormwater runoff pollution, promote infiltration, and hold/slow down the volume of water coming from a site. In order to meet these permit and policy requirements, projects must incorporate the use of green roofs, impervious surfaces, tree planters, grassy swales, bioretention and/or detention basins, among other factors.

Project Applicability. The project will not disturb an acre or more of ground, so the NPDES General Permit would not apply to this project. It is our understanding that the Municipal Regional Stormwater NPDES Permit would apply; however, and the project will comply with the requirements of this permit. Therefore, construction-phase activities would not result in detrimental water quality effects on biological or regulated resources.

3.3 Local Regulations

3.3.1 Los Altos Tree Protection Ordinance
According to the City’s Municipal Code Chapter 11.08, it is unlawful to damage or kill any protected tree, or to remove any protected tree from private or public property without obtaining a permit. A protected tree is defined as trees that are 48 inches in circumference at 48 inches above grade, designated by the historical commission as a heritage tree (or that is under consideration for designation as a heritage tree), or any tree that was required by the City to be saved or planted in conjunction with a development review application. City requirements to protect trees designated for preservation during construction include installing protective fencing; maintaining the existing grade out to the dripline of the tree; installing drain wells where impervious surfaces will be placed over a tree’s root system; repairing trees that are damaged by construction, and avoiding attachment of signs, wires, or other objects to the tree. Conditions approval for tree removal may include planting replacement trees.

Project Applicability: The project will comply with the City’s requirements for any trees that need to be removed.

Halsey House Demolition Project
Biological Resources Report
14 H. T. Harvey & Associates
August 2, 2024

3.3.2 Los Altos Watercourse Protection Regulations
The City’s Municipal Code Chapter 6.32 requires creeks to be maintained reasonably free of trash, debris, excessive vegetation, and other obstacles that would pollute, contaminate, or significantly retard the flow of water. Any discharge into creeks, modification of the natural flow of water, development of permanent structures, earthwork, fence construction, removal of materials from, or placement of materials within a creek requires a permit.

In addition, all parcels along Adobe Creek from Shoup Park south to O’Keefe Lane are subject to a setback equivalent to the greatest of the following distances:
• 40 feet (for parcels 3 acres in size or smaller) or 80 feet (for parcels larger than 3 acres) from the top of the nearest bank,
• The distance of any easement owned or controlled by the Santa Clara Valley Water District, or • The 100-year floodplain.

No construction activities including structures, grading, paving, fences, water storage facilities, and subsoil disturbance; dumping; use of herbicides or pesticides; or removal of vegetation may occur except with permission from the planning department. Pathways, access roads, utilities, bridges, and fire and flood control measures are allowed. Exceptions are available for special circumstances (e.g., size, shape, and topography) where the proposed activity will not be detrimental to the health, safety, or welfare of persons living or working in the vicinity and is consistent with the purposes of the setbacks as provided.

Project Applicability: No streams are present on the project site. Due to the presence of Adobe Creek approximately 16 feet to the northeast, and because the project site is located in between Shoup Park to the north and O’Keefe Lane to the south, a setback overlaps the project site. The size of the parcel on which the project site is located is 4.3 acres; therefore, the setback defined by the City for this location is 80 feet from the top of bank. The project would need to comply with the City’s watercourse protection regulations, which include guidance for allowable uses within the stream corridor. It is our understanding that the City will grant an exception to the 80-foot setback for the project, as the proposed removal of Halsey House will result in returning the area to its natural grade and vegetation, a net benefit to the Adobe Creek corridor.

Halsey House Demolition Project
Biological Resources Report
15 H. T. Harvey & Associates
August 2, 2024
Section 4. Environmental Setting

4.1 General Project Area Description
The project site is located in the City of Los Altos in Santa Clara County, California (Figure 1). The climate in the project vicinity is coastal Mediterranean, with most rain falling in the winter and spring. Mild cool temperatures are common in the winter, and hot to mild temperatures are common in the summer. Climate conditions in the vicinity include a 30-year average of 18.68 inches of annual precipitation with a monthly average temperature range from 48.5ºF to 71.4ºF (PRISM Climate Group 2024). Elevations on the project site range from 203–223 feet above mean sea level (Google Inc. 2024). The NRCS has mapped one soil unit on the project site: Urban land-Flaskan complex 2 to 9% slopes (NRCS 2024). Urban land-Flaskan complex is a welldrained soil found on alluvial fans, and is composed of sandy loam, sandy clay loam, gravelly sandy clay loam, and very gravelly sandy loam (NRCS 2024).

4.2 Biotic Habitats
The reconnaissance-level survey identified two biotic habitats on the project site: developed and coast live oak woodland (Figure 3). These biotic habitats are described in detail below. Plant species observed during the reconnaissance-level survey are listed in Appendix A.

4.2.1 Developed
Vegetation. Approximately 0.3 acre of the project site
is developed and supports the unoccupied Halsey
House building, associated seating areas, an
ornamental garden, and an equipment shed (Photo 1).

Trees growing in the developed area on the site include native coast live oak (Quercus agrifolia) and California bay (Umbellularia californica) along with nonnative
pepper tree (Schinus molle) and persimmon (Diospyros
virginiana). Understory plants in this area include
Douglas iris (Iris douglasiana), marah (Marah fabacea), privet (Ligustrum sp.), annual blue grass (Poa annua),
foxtail barley (Hordeum murinum), and English ivy (Hedera helix). Native California poppy (Eschscholzia californica), hummingbird sage (Salvia spathacea), purple sage (Salvia leucophylla), black sage (Salvia mellifera), California gooseberry (Ribes californicum), coffeeberry (Frangula californica), and strawberry (Fragaria sp.) are present in the ornamental garden. In addition, nonnative French broom (Genista monspessulana) is present adjacent to the Halsey House building.

Photo 1. Developed habitat on the project
site.

N:\Projects4800\4814-01\Reports\BRR\BRR.aprx
40 20 0 40
±
Feet
Project Site
Adobe Creek and Setback
Top of Bank
80-foot Setback from Top of Bank
Biotic Habitats
Coast Live Oak Woodland (0.3 acre)
Developed (0.3 acre)
Figure 3. Biotic Habitats
Halsey House Demolition Project Biological Resources Report (4814-01) August 2024
Adobe Creek

Halsey House Demolition Project
Biological Resources Report
17 H. T. Harvey & Associates
August 2, 2024
Wildlife. Developed areas of the project site serve as wildlife habitat only in a very limited capacity, and most wildlife species that occur in these areas are tolerant of frequent human disturbances. Common wildlife species that are associated with developed areas and can occur in developed portions of the project site include the nonnative European starling (Sturnus vulgaris), house mouse (Mus musculus), and black rat (Rattus rattus), as well as the native western fence lizard (Sceloporus occidentalis), raccoon (Procyon lotor), and a variety of birds including the Anna’s hummingbird (Calypte anna), dark-eyed junco (Junco hyemalis), American crow (Corvus brachyrhynchos), and northern mockingbird (Mimus polyglottos). The buildings on the project site may be attractive to certain bird species in the area that nest on buildings such as the black phoebe (Sayornis nigricans), Bewick’s wren (Thryomanes bewickii), mourning dove (Zenaida macroura), and house finch (Haemorhous mexicanus).

The Halsey House building provides suitable roosting habitat for bats, and an individual Townsend’s big-eared bat (Corynorhinus townsendii) was observed roosting in the building during the May 7, 2024 site visit. During the May 16, 2024 dusk emergence survey, two California myotis (Myotis californicus) and one Townsend’s big-eared bat were recorded flying overhead with acoustic detectors. In addition, an acoustic detector was left inside the Halsey House building for five nights, during which time 20 Townsend’s big-eared bat calls (which may have been produced by one or several individuals) were recorded (Table 1). Based on the relatively small number of calls detected each night (i.e., 1–7 calls per night), as well as their timing, we determined in consultation with H. T. Harvey & Associates senior bat biologist David Johnston, Ph.D., that the Townsend’s big-eared bat(s) using the building represent a non-maternity roost of a small number of individuals. This was determined based on the detection of calls only in the late evening and early morning, when the bats exited and returned to the roost, as opposed to numerous call detections throughout the night (which is typical when adults are feeding young). This roost likely consists of one or a few individual male bats, which is typical of this species.

Table 1. Summary of Townsend’s Big-Eared Bat Calls Detected Inside Halsey House from May 16– 21, 2024
Date
Time Total Calls
midnight 6am noon 6pm Recorded
16-May 4
17-May 7
18-May 1
19-May 3
20-May 4
21-May 1

Halsey House Demolition Project
Biological Resources Report
18 H. T. Harvey & Associates
August 2, 2024

4.2.2 Coast Live Oak Woodland
Vegetation. Coast live oak woodland makes up 0.3
acre of the project site. This habitat is dominated by
coast live oaks, which are interspersed with several
other tree species including native California bay,
California buckeye (Aesculus californica), and valley oak (Quercus lobata) as well as nonnative tree of heaven
(Ailanthus altissima). Shrubs that occur in the midstory of this habitat include native toyon (Heteromeles
arbutifolia) and poison oak (Toxicodendron diversilobum).

The understory is mainly composed of leaf duff and
large patches of nonnative Italian thistle (Carduus
pycnosephalus) and ripgut brome (Bromus diandrus) with
smaller numbers of native California blackberry (Rubus ursinus), foxtail barley, rose clover (Trifolium hirtum), California buttercup (Ranunculus californica), common bedstraw (Galium aparine), and miners lettuce (Claytonia perfoliata) as well as nonnative curly dock (Rumex crispus).

Wildlife. Woodlands dominated by oaks typically support diverse animal communities in California. Coast live oaks provide abundant food resources, including acorns and invertebrates, as well as substantial shelter for animals in the form of cavities, crevices in bark, and complex branching growth. The oak woodland habitat on the project site is part of a larger woodland (including oaks, redwoods [Sequoia sempervirens], and other trees) at the Redwood Grove Nature Preserve, and is connected to open space areas supporting woodlands and grasslands to the south between the site and Interstate 280 by Adobe Creek. However, the oak woodland habitat on the site is limited in extent, and the Redwood Grove Nature Preserve and other open spaces along Adobe Creek to the south are isolated from more extensive oak woodland habitats in the region (e.g., large parks in the foothills several miles to the southwest) by residential development and roadways. As a result, the oak woodland habitat on the site provides fewer resources and foraging opportunities for wildlife species compared to more extensive oak woodlands in the region. Nevertheless, due to the high quality of this habitat on the site, the close proximity of riparian habitat associated with Adobe Creek (located approximately 16 feet to the north), and the presence of numerous remnant oaks in the urban forest of the surrounding residential development, a number of wildlife species associated with oak woodlands and tolerant of moderate levels of human disturbance are expected to utilize the coast live oak woodland habitat on the site for breeding and foraging.

Birds such as the chestnut-backed chickadee (Poecile rufescens), Anna’s hummingbird, bushtit (Psaltriparus minimus), Bewick’s wren, oak titmouse (Baeolophus inornatus), and California scrub-jay (Aphelocoma californica) may nest and forage in oaks on the project site. Other birds expected to use this habitat are the wintering hermit thrush (Catharus guttatus), ruby-crowned kinglet (Regulus calendula), Townsend’s warbler (Setophaga townsendi), and white-crowned sparrow (Zonotrichia leucophrys). Raptors such as the Cooper’s hawk (Accipiter cooperii) may forage for prey in oak woodlands on the site in small numbers. It is possible that up to one pair of raptors could nest Photo 2. Coast live oak woodland habitat on
the project site.

Halsey House Demolition Project
Biological Resources Report
19 H. T. Harvey & Associates
August 2, 2024
in the patches of oak woodland habitat on the site, but no active or inactive raptor nests were detected during the site visit, suggesting that raptors have not nested on the site in recent years.

Common amphibians such as the Pacific tree frog (Pseudacris regilla) and California slender salamander (Batrachoseps attenuatus) may take refuge in leaf duff and forage within oak woodland habitat on the project site.

Mammals, including the native bobcat (Lynx rufus), coyote (Canis latrans), raccoon, and black-tailed deer (Odocoileus hemionus) as well as the nonnative eastern gray squirrel (Sciurus carolinensis) and Virginia opossum (Didelphis virginiana) will forage in the oak woodland habitat on the project site. Additionally, several nests of the native San Francisco dusky footed woodrat, a California species of special concern, are present in this habitat, as are several burrows of Botta's pocket gophers (Thomomys bottae). The deer mouse (Peromyscus maniculatus) is also a common resident of oak woodlands. Diurnal raptors, such as the red-tailed hawk (Buteo jamaicensis), will forage for small mammals on the project site during the day, and nocturnal raptors, such as the great horned owl (Bubo virginianus) will forage for nocturnal rodents at night.

The mature oak trees on the site provide potential roosting habitat for bats in cavities; however, no bats were visually observed or recorded acoustically emerging from these or any other trees on the site during the May 16, 2024 dusk emergence survey, indicating that bats are not roosting in these trees currently, and no maternity roosts are present in these trees.

4.3 Adjacent Habitat Areas
Adobe Creek is an intermittent stream located approximately 16 feet northeast of the project site (Figure 2).

This creek supported flowing water at the time of the May 2024 site visit. Riparian woodland habitat along Adobe Creek is dominated by coast live oaks, California buckeyes, coast redwoods, and California bays rooted above and below the tops of banks. The understory of this habitat consists of leaf duff and sparse nonnative annual grasses, with occasional native species such as poison oak. Most of the ground is covered in leaf duff or erosion control materials. The creek is incised with steep banks with grades between 10–20%.

Riparian habitats in California generally support exceptionally rich animal communities and contribute disproportionately to landscape-level species diversity. The presence of seasonal water and abundant invertebrates provide foraging opportunities for many species, and the diverse habitat structure provides cover and nesting opportunities. Leaf litter provides cover for California slender salamanders and Pacific tree frogs, among others. Several reptiles may also occur here, including the western fence lizard, western skink (Eumeces skiltonianus), and southern alligator lizard (Elgaria multicarinata). Mammals such as the ornate shrew (Sorex ornatus), California vole (Microtus californica), Audubon’s cottontail (Sylvilagus audubonii), and San Francisco duskyfooted woodrat provide a prey base for mesopredators that forage here, such as the bobcat and coyote.

In addition to amphibians, reptiles, and mammals, the reach of Adobe Creek adjacent to the project site provides suitable foraging and breeding habitat for many of the bird species listed above, as well as the western flycatcher (Empidonax difficilis), Wilson’s warbler (Cardellina pusilla), warbling vireo (Vireo gilvus), and others.

Raptors such as red-shouldered hawks (Buteo lineatus) and Cooper’s hawks nest within riparian corridors and

Halsey House Demolition Project
Biological Resources Report
20 H. T. Harvey & Associates
August 2, 2024
forage there, as well as in adjacent habitats. Riparian habitats are also used heavily by migrant passerines and wintering birds.

4.4 Wildlife Movement
Wildlife movement within and in the vicinity of the project site takes many forms, and is different for the various suites of species associated with these lands. Bird and bat species move readily over the landscape in the project vicinity, foraging over and within both natural lands and landscaped areas. Mammals of different species move within their home ranges, but also disperse between patches of habitat. Generally, reptiles and amphibians similarly settle within home ranges, sometimes moving to central breeding areas, upland refugia, or hibernacula in a predictable manner, but also dispersing to new areas. Some species, especially among the birds and bats, are migratory, moving into or through the project vicinity during specific seasons. Aside from bats, there are no other mammal species in the vicinity of the site that are truly migratory. However, the young of many mammal species disperse from their natal home ranges, sometimes moving over relatively long distances in search of new areas in which to establish.

Movement corridors are segments of habitat that provide linkage for wildlife through the mosaic of suitable and unsuitable habitat types found within a landscape while also providing cover. On a broader level, corridors also function as paths along which wide-ranging animals can travel, populations can move in response to environmental changes and natural disasters, and genetic interchange can occur. In California, environmental corridors often consist of riparian areas along streams, rivers, or other natural features.

Due to the presence of development surrounding the project site, there are currently no well-defined or important movement corridors for mammals, amphibians, or reptiles on or through the project site. Wildlife species may move through the area using cover and refugia as they find them available. Adobe Creek, which eventually drains to the open waters of the San Francisco Bay, and its associated riparian corridor serves as a movement corridor for several common and special-status species of birds fish, mammals, reptiles, and amphibians through the Los Altos area. In addition, a number of birds, mammals, reptiles, and amphibians utilize the riparian corridor of Adobe Creek for movement purposes, as it provides sufficient vegetative cover preferred by these species when navigating across the landscape. Specifically, migratory passerines, rabbits, striped skunks, raccoons, Pacific treefrogs, and alligator lizards, amongst other species, are expected to move along this corridor adjacent to the project site.

Halsey House Demolition Project
Biological Resources Report
21 H. T. Harvey & Associates
August 2, 2024
Section 5. Special-Status Species and Sensitive Habitats CEQA requires assessment of the effects of a project on species that are protected by state, federal, or local governments as “threatened, rare, or endangered”; such species are typically described as “special-status species”. For the purpose of the environmental review of the project, special-status species have been defined as described below. Impacts on these species are regulated by some of the federal, state, and local laws and ordinances described in Section 3 above.

For purposes of this analysis, “special-status” plants are considered plant species that meet one or more of the following criteria:
• Listed under FESA as threatened, endangered, proposed threatened, proposed endangered, or a candidate species.
• Listed under CESA as threatened, endangered, rare, or a candidate species. • Listed by the CNPS as CRPR 1A, 1B, 2, 3, or 4.

For purposes of this analysis, “special-status” animals are considered animal species that meet one or more of the following criteria:
• Listed under FESA as threatened, endangered, proposed threatened, proposed endangered, or a candidate species.
• Listed under CESA as threatened, endangered, or a candidate threatened or endangered species. • Designated by the CDFW as a California species of special concern. • Listed in the California Fish and Game Code as fully protected species (fully protected birds are provided in Section 3511, mammals in Section 4700, reptiles and amphibians in Section 5050, and fish in Section 5515).

Information concerning threatened, endangered, and other special-status species that potentially occur on the project site was collected from several sources and reviewed by H. T. Harvey & Associates biologists as described in Section 2.1 above. Figure 4 depicts CNDDB records of special-status plant species in the general vicinity of the project site and Figure 5 depicts CNDDB records of special-status animal species. These generalized maps show areas where special-status species are known to occur or have occurred historically.

Cañada College
84 Tripp Rd
Canada Rd
Wunderlich
County Park
Sky Londa
84 Pescadero
Rd
La Honda
Allied Arts
Stanford Park Woodside Hills
Martin
Creek
Whiskey
Hill Rd
Portola Rd
Jasper Ridge
Biological
Preserve
Stanford
University
West Menlo
Central Portola
Valley
Sharon Heights
Woodside
Heights
Woodside
Portola Valley
West Menlo
Park
Stanford
Weekend Acres
Ladera
Woodruff C reek
Mindego Creek
Alpine Creek
Stevens Creek
35 Alpine Rd
Windy Hill Open
Space Preserve
- Skyline
Boulevard
Portola Valley
Ranch
Vista Verde
Los Trancos
Woods
Embarcade
Palo Alto ro Rd
Adobe Creek
Stanford Ave
S California Ave
Ca
Los Al
lifornia St
tos Ave
La Cresta
Dr
Louis Rd
Bryant St
Middlefield Rd
Oregon Expy
Cuesta Dr
El Camino Real
W El Camino Real
Pa
g
e
Mill
Rd
Central Expy
Foothill
Expy
San
Antonio Rd
Shoreline Golf
Links
Stanford
University
Los Altos Hills
Stanford
Los Altos
Mountain
View
Permanente Creek
35 Covington Rd
Miramonte Ave
Summerhill Ave
Ta affe Rd
Foothill Expy
Rancho San
Antonio County
Park
Foothill College
Loyola
W Wa
E Arques Ave
shington Ave
E Evelyn Ave
E Evelyn Ave
Kifer Rd
Fairchild Dr
W E
Stewart Dr
velyn Ave
Manila Dr
Tasman Dr
Grant Rd
N Mathilda Ave
Moffett Blvd
N Shoreline Blvd
E Middlefield Rd
N
Fair Oaks
Ave
Central Expy
Lawrence Expy
W Valley Fwy
Sunnyvale Golf
Course
Sunnyvale
Baylands
County Park
Moffett Federal
Airfield
South Shore
Port
Sunnyvale
Grape Ave
S
W Remington Dr
Bernardo Ave
Iris Ave
Henderson Ave
The Dalles Ave
Levin Ave Reed Ave
Poplar Ave
Rainbow Dr Rainbow Dr
Belleville Way
Johnson Ave
Bubb Rd
Creston Dr
S Stelling Rd
S Tantau Ave
S Blaney Ave
Grant Rd
Sunnyvale Saratoga Rd
W Fremont Ave
Miller Ave
E Homestead Rd
N De Anza Blvd
Lawrence Expy
E El Camino Real
Foothill Expy
W
Valley Fwy
Cupertino
Lakeside Dr
L aurelwood Rd
Kifer Rd
Scott Blvd
Lafayette
St
Los Estero
Central Expy
Mountain View Alvis
Santa Clara Golf
and Tennis Club
Alviso
Payne Ave
Benton St
Pomeroy Ave
Nobili Ave
Walsh Ave
War burton Ave Warburton Ave
Blackford Ave
Doyle Rd
Monroe St
Kiely Blvd
Williams Rd
S
an
To
mas Expy
Santa C
Serpentine Bunchgrass
Northern Coastal Salt Marsh
Northern Coastal Salt Marsh
Northern Coastal Salt Marsh
robust spineflower robust spineflower
fragrant fritillary
alkali milk-vetch
lost thistle
saline clover saline clover
arcuate bushmallow
western leatherwood
Hoover's button-celery
San Francisco collinsia
alkali milk-vetch
Hoover's button-celery
chaparral ragwort chaparral ragwort
Santa Clara red ribbons
arcuate bushmallow
round-headed collinsia
Santa Cruz clover Santa Cruz clover
San Mateo thorn-mint San Mateo thorn-mint
northern slender pondweed
Hoover's button-celery
Hoover's button-celery
woodland woollythreads
woodland woollythreads woodland woollythreads
two-fork clover two-fork clover
Choris' popcornflower Choris' popcornflower
Point Reyes salty bird's-beak
arcuate bushmallow
Franciscan onion
hairless popcornflower hairless popcornflower
woodland woollythreads
legenere
western leatherwood
Jepson's coyote-thistle
Congdon's tarplant Congdon's tarplant
woodland woollythreads
San Mateo woolly sunflower San Mateo woolly sunflower
woodland woollythreads
Anderson's manzanita
western leatherwood
woodland woollythreads
white-flowered rein orchid
Hall's bushmallow
Franciscan onion
western leatherwood
western leatherwood
western leatherwood
western leatherwood
Kings Mountain manzanita Kings Mountain manzanita
Congdon's tarplant Congdon's tarplant
Santa Clara red ribbons
western leatherwood
arcuate bushmallow
western leatherwood
Congdon's tarplant Congdon's tarplant
western leatherwood
western leatherwood
Marin western flax
western leatherwood
arcuate bushmallow
Marin western flax
Congdon's tarplant Congdon's tarplant
Congdon's tarplant Congdon's tarplant
western leatherwood
Sanford's arrowhead
western leatherwood
western leatherwood
western leatherwood
western leatherwood
western leatherwood
western leatherwood
western leatherwood
Jepson's coyote-thistle
woodland woollythreads woodland woollythreads
woodland woollythreads
western leatherwood
western leatherwood
western leatherwood
Congdon's tarplant Congdon's tarplant
western leatherwood
western leatherwood
Choris' popcornflower Choris' popcornflower
western leatherwood
western leatherwood
western leatherwood
western leatherwood
western leatherwood
Choris' popcornflower Choris' popcornflower
western leatherwood
Congdon's tarplant Congdon's tarplant
Kings Mountain manzanita Kings Mountain manzanita
western leatherwood
Kings Mountain manzanita Kings Mountain manzanita
Kings Mountain manzanita
western leatherwood
western leatherwood
arcuate bushmallow
woodland woollythreads woodland woollythreads
arcuate bushmallow
western leatherwood
Kings Mountain manzanita Kings Mountain manzanita
woodland woollythreads
arcuate bushmallow
Congdon's tarplant Congdon's tarplant
Congdon's tarplant Congdon's tarplant
western leatherwood
western leatherwood
western leatherwood
woodland woollythreads
N:\Projects4800\4814-01\Reports\BRR\BRR.aprxmlagarde
Halsey House Demolition Project Biological Resources Report (4814-01) August 2024
Figure 4. CNDDB-Mapped Records of Special-Status Plants

1.2 0.6 0 1.2 ± Miles
Specific Location
General Area
Approximate Location
Plants
General Area
Terrestrial Communities
CNDDB Records
5-mile Radius
Project Location

Cañada College
84 Tripp Rd
Canada Rd
Wunderlich
County Park
Sky Londa
84 Pescadero
Rd
La Honda
Allied Arts
Stanford Park Woodside Hills
Martin
Creek
Whiskey
Hill Rd
Portola Rd
Jasper Ridge
Biological
Preserve
Stanford
University
West Menlo
Central Portola
Valley
Sharon Heights
Woodside
Heights
Woodside
Portola Valley
West Menlo
Park
Stanford
Weekend Acres
Ladera
Woodruff C reek
Mindego Creek
Alpine Creek
Stevens Creek
35 Alpine Rd
Windy Hill Open
Space Preserve
- Skyline
Boulevard
Portola Valley
Ranch
Vista Verde
Los Trancos
Woods
Embarcade
Palo Alto ro Rd
Adobe Creek
Stanford Ave
S California Ave
Ca
Los Al
lifornia St
tos Ave
La Cresta
Dr
Louis Rd
Bryant St
Middlefield Rd
Oregon Expy
Cuesta Dr
El Camino Real
W El Camino Real
Pa
g
e
Mill
Rd
Central Expy
Foothill
Expy
San
Antonio Rd
Shoreline Golf
Links
Stanford
University
Los Altos Hills
Stanford
Los Altos
Mountain
View
Permanente Creek
35 Covington Rd
Miramonte Ave
Summerhill Ave
Ta affe Rd
Foothill Expy
Rancho San
Antonio County
Park
Foothill College
Loyola
W Wa
E Arques Ave
shington Ave
E Evelyn Ave
E Evelyn Ave
Kifer Rd
Fairchild Dr
W E
Stewart Dr
velyn Ave
Manila Dr
Tasman Dr
Grant Rd
N Mathilda Ave
Moffett Blvd
N Shoreline Blvd
E Middlefield Rd
N
Fair Oaks
Ave
Central Expy
Lawrence Expy
W Valley Fwy
Sunnyvale Golf
Course
Sunnyvale
Baylands
County Park
Moffett Federal
Airfield
South Shore
Port
Sunnyvale
Grape Ave
S
W Remington Dr
Bernardo Ave
Iris Ave
Henderson Ave
The Dalles Ave
Levin Ave Reed Ave
Poplar Ave
Rainbow Dr Rainbow Dr
Belleville Way
Johnson Ave
Bubb Rd
Creston Dr
S Stelling Rd
S Tantau Ave
S Blaney Ave
Grant Rd
Sunnyvale Saratoga Rd
W Fremont Ave
Miller Ave
E Homestead Rd
N De Anza Blvd
Lawrence Expy
E El Camino Real
Foothill Expy
W
Valley Fwy
Cupertino
Lakeside Dr
L aurelwood Rd
Kifer Rd
Scott Blvd
Lafayette
St
Los Estero
Central Expy
Mountain View Alvis
Santa Clara Golf
and Tennis Club
Alviso
Payne Ave
Benton St
Pomeroy Ave
Nobili Ave
Walsh Ave
War burton Ave Warburton Ave
Blackford Ave
Doyle Rd
Monroe St
Kiely Blvd
Williams Rd
S
an
To
mas Expy
Santa C
yellow rail yellow rail
pallid bat pallid bat
pallid bat pallid bat
hoary bat hoary bat
hoary bat hoary bat
hoary bat hoary bat
hoary bat hoary bat
yellow rail yellow rail
yellow rail yellow rail
western bumble bee
obscure bumble bee obscure bumble bee
Crotch's bumble bee
long-eared owl long-eared owl
yellow rail yellow rail
hoary bat hoary bat
American badger American badger
western bumble bee
obscure bumble bee
obscure bumble bee
Crotch's bumble bee
burrowing owl burrowing owl
pallid bat pallid bat
Santa Cruz kangaroo rat Santa Cruz kangaroo rat Alameda song sparrow Santa Cruz kangaroo rat Santa Cruz kangaroo rat
hoary bat hoary bat
Townsend's big-eared bat Townsend's big-eared bat
yellow rail yellow rail
California giant salamander California giant salamander salt-marsh wandering shrew
tricolored blackbird
American badger American badger northwestern pond turtle western bumble bee
Alameda song sparrow
longfin smelt longfin smelt burrowing owl burrowing owl western ridged mussel western ridged mussel
obscure bumble bee
foothill yellow-legged frog - central coast DPS
foothill yellow-legged frog - central coast DPS
California giant salamander California giant salamander Townsend's big-eared bat Townsend's big-eared bat
mimic tryonia (=California brackishwater snail) mimic tryonia (=California brackishwater snail) hoary bat hoary bat
burrowing owl burrowing owl
western snowy plover western snowy plover
American badger American badger
American badger American badger
burrowing owl burrowing owl
burrowing owl burrowing owl
western snowy plover western snowy plover
western ridged mussel western ridged mussel
saltmarsh common yellowthroat saltmarsh common yellowthroat American badger American badger
northwestern pond turtle
northwestern pond turtle
burrowing owl burrowing owl
Santa Cruz black salamander Santa Cruz black salamander Santa Cruz black salamander Santa Cruz black salamander Santa Cruz black salamander Santa Cruz black salamander Santa Cruz black salamander Santa Cruz black salamander salt-marsh harvest mouse
California Ridgway's rail California Ridgway's rail
American badger American badger
steelhead - central California coast DPS steelhead - central California coast DPS burrowing owl burrowing owl
burrowing owl burrowing owl
burrowing owl burrowing owl
American badger American badger
California black rail California black rail
western ridged mussel western ridged mussel
American badger American badger
Alameda song sparrow
bald eagle
burrowing owl burrowing owl
burrowing owl burrowing owl
California Ridgway's rail California Ridgway's rail
white-tailed kite
burrowing owl burrowing owl
northwestern pond turtle
American badger American badger
American badger American badger
burrowing owl burrowing owl
burrowing owl burrowing owl
California black rail California black rail
California least tern
California least tern
American badger American badger
American badger American badger
Townsend's big-eared bat Townsend's big-eared bat
Townsend's big-eared bat Townsend's big-eared bat
Santa Cruz black salamander Santa Cruz black salamander burrowing owl burrowing owl
American badger American badger
burrowing owl burrowing owl
Alameda song sparrow
American badger American badger
Santa Cruz black salamander Santa Cruz black salamander burrowing owl burrowing owl
Bay checkerspot butterfly
American badger American badger
American badger American badger
California linderiella
salt-marsh harvest mouse
California Ridgway's rail California Ridgway's rail
Yuma myotis
saltmarsh common yellowthroat saltmarsh common yellowthroat American badger American badger
northwestern pond turtle
American badger American badger
American badger American badger
burrowing owl burrowing owl
burrowing owl burrowing owl
northwestern pond turtle
American badger American badger
American badger American badger
American badger American badger
American badger American badger
American badger American badger
American badger American badger
American badger American badger
American badger American badger
American badger American badger
American badger American badger
California black rail California black rail
salt-marsh harvest mouse
salt-marsh harvest mouse
burrowing owl burrowing owl
saltmarsh common yellowthroat saltmarsh common yellowthroat burrowing owl burrowing owl
northwestern pond turtle
saltmarsh common yellowthroat saltmarsh common yellowthroat burrowing owl burrowing owl
northwestern pond turtle
steelhead - central California coast DPS
saltmarsh common yellowthroat saltmarsh common yellowthroat burrowing owl burrowing owl
California giant salamander California giant salamander Bay checkerspot butterfly
San Francisco dusky-footed woodrat San Francisco dusky-footed woodrat San Francisco dusky-footed woodrat San Francisco dusky-footed woodrat California giant salamander California giant salamander California giant salamander California giant salamander northwestern pond turtle
northwestern pond turtle
northwestern pond turtle
burrowing owl burrowing owl
burrowing owl burrowing owl
burrowing owl burrowing owl
San Francisco dusky-footed woodrat San Francisco dusky-footed woodrat burrowing owl burrowing owl
Cooper's hawk
red-bellied newt red-bellied newt
American badger American badger
American badger American badger
American badger American badger
California black rail California black rail
northwestern pond turtle
northwestern pond turtle
northwestern pond turtle
northwestern pond turtle
Townsend's big-eared bat Townsend's big-eared bat
Townsend's big-eared bat Townsend's big-eared bat
Townsend's big-eared bat Townsend's big-eared bat
California giant salamander California giant salamander California giant salamander California giant salamander San Francisco dusky-footed woodrat San Francisco dusky-footed woodrat San Francisco dusky-footed woodrat San Francisco dusky-footed woodrat California giant salamander California giant salamander Townsend's big-eared bat Townsend's big-eared bat
CRLF
CRLF
CRLF
CRLF
CRLF
CRLF
CRLF
CRLF
CRLF
CRLF
CRLF
CRLF
CRLF
CRLF
CRLF
CRLF
CRLF
CRLF
CRLF
CRLF
CRLF
CRLF
CRLF
CRLF
CRLF
CRLF
CRLF
CRLF
CRLF
CRLF
CRLF
CRLF
CRLF
CRLF
CRLF
CRLF
CRLF
CTS
CTS
CTS
CTS
CTS
CTS
CTS
N:\Projects4800\4814-01\Reports\BRR\BRR.aprxmlagarde
Figure 5. CNDDB-Mapped Records of Special-Status Animals

1.2 0.6 0 1.2 ± Miles
Note: CTS = California Tiger Salamander,
CRLF = California Red-legged Frog
Specific Location
General Area
Approximate Location
Wildlife
CNDDB Records
5-mile Radius
Project Location
Halsey House Demolition Project Biological Resources Report (4814-01) August 2024

Halsey House Demolition Project
Biological Resources Report
24 H. T. Harvey & Associates
August 2, 2024

5.1 Special-Status Plant Species
The CNPS (2024) and CNDDB (2024) identify 89 special-status plant species as potentially occurring in at least one of the nine USGS 7.5-minute quadrangles containing or surrounding the project site (for CNPS) or within the project vicinity (for CNDDB) (Appendix B). Of the 89 potentially occurring special-status plant species, 85 were determined to be absent from the project site for at least one of the following reasons: (1) absence of suitable habitat types, (2) lack of specific microhabitat or edaphic requirements, (3) the elevation range of the species is outside of the range of the project site, and/or (4) the project site is outside the species’ known geographic range and/or there are no nearby extant records (Appendix B).

Suitable habitat, edaphic requirements, and elevation range are present on the project site for four special-status plant species; these species are addressed in greater detail in Table 1 below. All of the special-status plant species for which suitable habitat is present on the site would have been detectable during a May survey, and hence were determined to be absent from the site during the May 7, 2024 site visit.

Halsey House Demolition Project
Biological Resources Report
25 H. T. Harvey & Associates
August 2, 2024
Table 1. Special-Status Plant Species, Their Status, and Potential for Occurrence on the Project Site Name *Status Habitat and Blooming Period Potential for Occurrence on the Project Site Federal or State Endangered, Threatened, Candidate, or Rare Species Dudley's lousewort
(Pedicularis dudleyi)

SR, CRPR
1B.2
Maritime chaparral, cismontane
woodland, North Coast
coniferous forest, and valley
and foothill grassland, often in
deep shady woods of older
coast redwood forests
(blooming period April to June)
Absent. Only low-quality suitable cismontane woodland habitat to support this species is present on the project site. Most occurrences are known from more shaded and mesic habitats with less vegetation in the understory. Known to occur at Portola Redwoods State Park approximately 12 miles to the south (CNDDB 2024). No individuals were observed on the site during a focused survey conducted in May 2024. Determined to be absent.

CNPS-Listed Plant Species
Bent-flowered fiddleneck
(Amsinckia lunaris)
CRPR 1B.2 Coastal bluff scrub, cismontane
woodland, valley and foothill
grassland/oak woodland and
chaparral (blooming period
March to June).

Absent. Suitable grassland habitat to support this species is present on the project site. Bent-flowered fiddleneck is known to occur at Foothills Open Space Preserve approximately 3.9 miles to the southwest (CNDDB 2024). However, no individuals were observed on the site during a focused survey conducted in May 2024. Determined to be absent.

California bottlebrush
(Elymus californicus)
CRPR 1B.2 Cismontane woodland,
broadleafed upland forest,
North Coast coniferous forest,
riparian woodland (blooming
period May to August)
Absent. Suitable cismontane woodland habitat to support this species is present on the project site. California bottlebrush is known to occur in Sam McDonald County Park approximately 8.8 miles to the southwest (Calflora 2024). However, no individuals were observed on the site during a focused survey conducted in May 2024.

Determined to be absent.

Arcuate bush-mallow
(Malacothamnus arcuatus)
CRPR 1B.2 Chaparral and cismontane
woodland, sometimes on
gravelly alluvial soils, or in any
shrub or tree woodland that has
recently burned (detectable
year-round)
Absent. Has been documented in a wide variety of woody habitats, including oak woodland, and is most prevalent after wildland fires (Morse 2022). Known to occur adjacent to Rancho San Antonio County Park and Open Space Preserve approximately 2.3 miles to the south (CNDDB 2024). However, no individuals were observed on the site during a focused survey conducted in May 2024. Determined to be absent.
*Key to Status Abbreviations: State Rare (SR); California Rare Plant Rank (CRPR).

CRPR 1B = Rare, Threatened, or Endangered in California and elsewhere .2 = Moderately threatened in California (20-80% of occurrences threatened)

Halsey House Demolition Project
Biological Resources Report
26 H. T. Harvey & Associates
August 2, 2024

5.2 Special-Status Animal Species
The legal status and likelihood of occurrence on the project site of special-status animal species known to occur, or potentially occurring, in the surrounding region are presented in Table 2. Most of the special-status species listed in Table 2 are not expected to occur on the project site because it lacks suitable habitat, is outside the known range of the species, and/or is isolated from the nearest known extant populations by development or otherwise unsuitable habitat.

The following special-status species that are present in specialized habitats on the San Francisco Peninsula, or that occurred on or near the Peninsula historically but are no longer present, are absent from the project site due to a lack of suitable habitat and/or isolation of the site from populations by urbanization: the western bumble bee (Bombus occidentalis), Crotch’s bumble bee (Bombus crotchii), Bay checkerspot butterfly (Euphydryas editha bayensis), California tiger salamander (Ambystoma californiense), Santa Cruz black salamander (Aneides niger), California red-legged frog (Rana draytonii), foothill yellow-legged frog (Rana boylii), San Francisco garter snake (Thamnophis sirtalis tetrataenia), northwestern pond turtle (Actinemys marmorata), northern harrier (Circus hudsonius), burrowing owl (Athene cunicularia), grasshopper sparrow (Ammodramus savannarum), tricolored blackbird (Agelaius tricolor), loggerhead shrike (Lanius ludovicianus), and American badger (Taxidea taxus). While bald eagles (Haliaeetus leucocephalus) and golden eagles (Aquila chrysaetos) may fly over the project site at times, none are expected to nest or forage on or close to the project site.

No aquatic habitats to support special-status fish species are present on the project site. Adobe Creek, located 16 feet to the north, potentially supports southern coastal roach (Hesperoleucus venustus subditus) and riffle sculpin (Cottus gulosus), which are California species of special concern. The Sacramento hitch (Lavinia exilicauda exilicauda), also a species of special concern, is not known to occur in the Adobe Creek watershed. Anadromous special-status fish species, including the Central California Coast steelhead (Oncorhynchus mykiss), Central California Coast coho salmon (Oncorhynchus kisutch), and Pacific lamprey (Entosphenus tridentatus), are absent from Adobe Creek due to the tide gates at the mouth of Adobe Creek and the box culverts at the road crossings of El Camino Real and Interstate 280 downstream of the site, which are impassible barriers (Leidy et al. 2005).

The mountain lion (Puma concolor), a candidate for listing under CESA; the monarch butterfly (Danaus plexippus), a candidate for listing under FESA; and the western red bat (Lasiurus blossevillii) and pallid bat (Antrozous pallidus), which are California species of special concern, may also forage on the project site. As discussed in Table 2, these species are not expected to den, roost, or breed on or immediately adjacent to the project site due to a lack of suitable habitat, and they will be affected very little, if at all, by the proposed project. In addition, the olive-sided flycatcher (Contopus cooperi) is considered a California species of special concern only when nesting; individuals may occasionally occur on or over the project site as nonbreeding transients, foragers, or migrants, but no suitable nesting habitat for this species occurs on the project site.

Halsey House Demolition Project
Biological Resources Report
27 H. T. Harvey & Associates
August 2, 2024
The California giant salamander (Dicamptodon ensatus), Vaux’s swift (Chaetura vauxi), yellow warbler (Setophaga petechia), white-tailed kite (Elanus leucurus), San Francisco dusky-footed woodrat, and Townsend’s big-eared bat are addressed in greater detail in this report because these species can potentially breed or occur on or immediately adjacent to the project site and/or may be significantly impacted by the proposed project in the absence of avoidance and minimization measures (see Section 6 Impacts and Mitigation Measures below).

Halsey House Demolition Project
Biological Resources Report
28 H. T. Harvey & Associates
August 2, 2024
Table 2. Special-Status Animal Species, Their Status, and Potential for Occurrence on the Project Site Name *Status Habitat Potential for Occurrence on the Project Site Federal or State Endangered, Threatened, or Candidate Species Bay checkerspot
butterfly
(Euphydryas editha
bayensis)
FT Native grasslands on serpentine soils.

Larval host plants are Plantago erecta
and/or Castilleja sp. The flight season
extends from late February to early May.

Absent. No suitable habitat; determined to be absent.

Monarch butterfly
(Danaus plexippus)
FC Requires milkweeds (Asclepias spp.) for
egg-laying and larval development, but
adults obtain nectar from a wide variety
of flowering plants in many habitats.

Individuals congregate in winter roosts,
primarily in Mexico and in widely
scattered locations on the central and
southern California coast.

May be Present as Nonbreeder. The monarch butterfly occurs throughout the region primarily as a migrant. No milkweeds were observed on the project site during the May 2024 survey, and therefore no breeding habitat is present on the site. Small numbers of individuals may forage on the project site, especially during spring and fall migration. However, the site does not provide high-quality foraging habitat for this species. While ostensibly suitable overwintering habitat for monarchs (i.e., eucalyptus [Eucalyptus sp.] trees) is present within areas of the Redwood Grove Nature Preserve adjacent to the site, no current or historical overwintering sites are known as far inland as the project site; the nearest known overwintering aggregation location is 18.6 miles to the northwest in Coyote Point Recreation Area in San Mateo (Xerces Society 2024).

Crotch’s bumble bee
(Bombus crotchii)
SC Open grassland and scrub habitats. Absent. Although this species was historically found throughout the southern two-thirds of California, population declines and range contractions (25% relative to its historical range) have made this species very scarce in the region (CDFW 2019). Since 2019, there have been documented occurrences of approximately 100
individuals from nearly 20 locations in Santa Clara County (Bumble Bee Watch 2024; iNaturalist 2024; S. Rottenborn, pers. obs.), indicating that the species is still extant, and fairly widespread (albeit in low numbers in most locations) in the county. However, no suitable grassland or scrub habitat to provide nesting and foraging habitat for this species is present on or adjacent to the site, and no high-quality floral resources to attract this species to the site are present. Therefore, this species is determined to be absent.

Halsey House Demolition Project
Biological Resources Report
29 H. T. Harvey & Associates
August 2, 2024
Name *Status Habitat Potential for Occurrence on the Project Site Western bumble bee
(Bombus occidentalis)
SC Occurs in a variety of grassland, scrub,
and open woodland habitats.

Absent. Although the species was historically found throughout much of central and northern California, including the project vicinity, it has been extirpated from much of its former range, and there are no recent records from Los Altos or nearby areas (CDFW 2019, Bumble Bee Watch 2024, iNaturalist 2024). Therefore, this species is absent from the project site.

Central California
coast steelhead
(Oncorhynchus
mykiss)
FT Cool streams with suitable spawning
habitat and conditions allowing
migration between spawning and
marine habitats.

Absent. Occurs in the open waters of the San Francisco Bay, and is known to have occurred historically in Adobe Creek. However, the tide gates at the mouth of Adobe Creek can preclude the passage of anadromous fish, and the box culverts at the road crossings of El Camino Real and Interstate 280 downstream of the site are impassible barriers (Leidy et al. 2005). Determined to be absent.

Central California
Coast coho salmon
(Oncorhynchus
kisutch)
FT, ST Open ocean, estuaries, and rivers Absent. Central California Coast coho salmon may have occurred historically in the San Francisquito Creek watershed, but they have not been observed in San Francisco Estuary streams since the earlyto mid-1980’s (Leidy 2007). In addition, the tide gates at the mouth of Adobe Creek can preclude the passage of anadromous fish, and the box culverts at the road crossings of El Camino Real and Interstate 280 downstream of the site are impassible barriers (Leidy et al. 2005). Thus, this species is absent from Adobe Creek adjacent to the project site.

California tiger
salamander
(Ambystoma
californiense)
FT, ST Vernal or temporary pools in annual
grasslands or open woodlands. Adults
live terrestrially in small mammal burrows.

Absent. The California tiger salamander’s range on the San Francisco Peninsula historically occurred as far northwest as Woodside (CNDDB 2024). The closest extant population is located in the vicinity of Lake Lagunita on the Stanford University Campus, approximately 3.9 miles to the northwest (CNDDB 2024). Two additional historical occurrences are located 2.5 miles to the south (from 1893) and 3.9 miles to the west (from 1940), on the far side of Interstate 280 (CNDDB 2024). All of these occurrences are located far beyond the known dispersal distance of the species from the project site, and are separated from the project site by extensive urbanization and busy roadways. Therefore, this species is determined to be absent.

Halsey House Demolition Project
Biological Resources Report
30 H. T. Harvey & Associates
August 2, 2024
Name *Status Habitat Potential for Occurrence on the Project Site California red-legged
frog
(Rana draytonii)
FT, CSSC Streams, freshwater pools, and ponds
with emergent or overhanging
vegetation.

Absent. No suitable aquatic breeding habitat for California redlegged frogs is present on the project site, and the nearby Adobe Creek is too fast-flowing and shallow, and lacks suitable pools and submergent vegetation, to provide suitable breeding habitat for this species. Known to occur along Purisima Creek 2.0 miles to the north and at Rancho San Antonio County Park 3.5 miles to the south (CNDDB 2024). However, dense urbanization and busy roadways present in between these records and the project site represent barriers to dispersal that prevent individuals at these locations from reaching the project site. Thus, this species is determined to be absent.

Foothill yellow-legged
frog
(Rana boylii)
FT, SE Streams, freshwater pools, and ponds
with emergent or overhanging
vegetation.

Absent. No suitable aquatic habitat is present on the project site, and the nearby Adobe Creek is too incised with limited cover to support habitat for this species. Historic records of this species are present in the Stanford and Portola Valley areas, but these records are considered to be extirpated (CNDDB 2024). The closest population of this species is located more than 9 miles to the southwest in the Santa Cruz Mountains (CNDDB 2024). Due to the intervening distance between current populations of this species and the project site, this species is determined to be absent.

San Francisco garter
snake
(Thamnophis sirtalis
tetrataenia)
FE, SE, SP Occurs in a variety of habitats, including
riparian areas; requires burrows for
hibernation and frogs as a prey base.

Absent. The San Francisco garter snake occurs on the San Francisco Peninsula from just north of the San Francisco–San Mateo County line south to approximately the San Mateo–Santa Cruz County line.

An intergrade zone composed of hybrids between the San
Francisco garter snake and red-sided garter snake (Thamnophis sirtalis sirtalis) occurs from Palo Alto north to the Pulgas region near Upper Crystal Springs Reservoir (Barry 1994). Thus, the project site is outside the range of the species, and determined to be absent.

Halsey House Demolition Project
Biological Resources Report
31 H. T. Harvey & Associates
August 2, 2024
Name *Status Habitat Potential for Occurrence on the Project Site Northwestern pond
turtle
(Actinemys
marmorata)
FPT, CSSC Permanent or nearly permanent water in
a variety of habitats with abundant
emergent or riparian vegetation.

Females lay eggs in upland habitats, in
clay or silty soils in unshaded (often
south-facing) areas (Jennings and Hayes
1994).

Absent. Known to occur in the project vicinity west of Interstate 280 approximately 3.1 miles to the southwest at Boranda Lake and 3.5 miles to the west at Felt Lake (CNDDB 2024). Ostensibly suitable aquatic dispersal and foraging habitat is present in Adobe Creek adjacent to the project site. However, Adobe Creek lacks connectivity to known occurrences of the species, and the lack of deep pools with aquatic escape cover make the habitat unsuitable for regular use by pond turtles. Further, because the closest occurrences of the species are separated from the project site by urban development and Interstate 280, individuals are not expected to successfully disperse across these developed areas to reach the project site. Determined to be absent.

Bald eagle
(Haliaeetus
leucocephalus)
SE, SP Occurs mainly along seacoasts, rivers,
and lakes; nests in tall trees or in cliffs,
occasionally on electrical towers; feeds
mostly on fish and waterfowl
Absent. No rivers or lakes are present on or near the project site to provide foraging habitat for this species, and individuals are not expected to nest on the site due to the lack of foraging habitat nearby. Determined to be absent.

Tricolored blackbird
(Agelaius tricolor)
ST Nests near fresh water in dense
emergent vegetation.

Absent. The tricolored blackbird has bred in only a few scattered locations in the project vicinity, and is absent from, or occurs only as a nonbreeder in, the surrounding area (Sequoia Audubon Society 2001, Rottenborn 2007a). This species typically nests in extensive stands of tall emergent herbaceous vegetation in non-tidal freshwater marshes and ponds. No suitable nesting habitat is present on the project site or along Adobe Creek adjacent to the site, as no large patches of emergent vegetation, blackberry (Rubus sp.) stands, or other suitable vegetation are present. Further, this species (whose colonies are loud and conspicuous) has never been recorded nesting in the site vicinity (Sequoia Audubon Society 2001, Rottenborn 2007a, Cornell Lab of Ornithology 2024), and high levels of disturbance likely preclude nesting near the site. The site also does not provide suitable foraging habitat for this species.

Halsey House Demolition Project
Biological Resources Report
32 H. T. Harvey & Associates
August 2, 2024
Name *Status Habitat Potential for Occurrence on the Project Site Mountain lion
(Southern
California/Central
Coast ESU)
(Puma concolor)
SC Has a large home range size and occurs
in a variety of habitats. Natal dens are
typically located in remote, rugged
terrain far from human activity. May
occasionally occur in areas near human
development, especially during
dispersal.

May be Present as Nonbreeder. In the project region, there are verified sightings reported on BAPP.org (2024) and numerous unpublished reports. This species occurs widely, though at low densities, throughout the Santa Cruz Mountains, and may disperse into lowland/valley floor areas. Mountain lions are not expected to regularly use the project site or establish a den on the site due to high levels of human activity and a lack of suitable denning habitat, but individuals may occur on the site as rare dispersants due to the site’s location near the periphery of development in the Los Altos Hills area (i.e., only approximately 1 mile from open lands south of Interstate 280).

California Species of Special Concern
Pacific lamprey
(Entosphenus
tridentatus)
CSSC Occupies anadromous habitat in large
streams entering the San Francisco and
San Pablo Bays. Spawns in cool
(shaded), clear, slow-moving rivers and
streams supporting gravel, silt, and sand
substrates (Moyle et al. 2015).

Absent. Historically, this species may have been present in streams throughout Santa Clara County. However, the tide gates at the mouth of Adobe Creek can preclude the passage of anadromous fish, and the box culverts at the road crossings of El Camino Real and Interstate 280 downstream of the site are impassible barriers (Leidy et al. 2005). Determined to be absent.

Southern coastal
roach
(Hesperoleucus
venustus subditus)
CSSC Occur in a wide array of habitats and
are tolerant of intermittent surface
water, a range of temperatures, and low
dissolved oxygen. Spawn in shallow
habitats with flow and coarse substrates.

Absent (May be Present in Adjacent Waters). No suitable aquatic habitat is present on the project site. However, this species is known to occur in Adobe Creek (Leidy 2007), and may be present in the adjacent reach of Adobe Creek during months when water is present.

Sacramento hitch
(Lavinia exilicauda
exilicauda)
CSSC Warm, lowland, waters including clear
streams, turbid sloughs, lakes, and
reservoirs. Has a high tolerance for
varying stream conditions and water
temperature.

Absent. Not known to occur within the Adobe Creek watershed (Leidy 2007). Determined to be absent.

Riffle sculpin
(Cottus gulosus)
CSSC Permanent, cool, headwater streams
with an abundance of riffles and rocky
substrates.

Absent (May be Present in Adjacent Waters). Riffle sculpin are widespread and locally abundant in the region, and are native to the Adobe Creek watershed (Leidy 2007). No suitable aquatic habitat to support this species is present on the project site.

However, individuals may be present in the adjacent reach of Adobe Creek when it contains water.

Halsey House Demolition Project
Biological Resources Report
33 H. T. Harvey & Associates
August 2, 2024
Name *Status Habitat Potential for Occurrence on the Project Site California giant
salamander
(Dicamptodon
ensatus)
CSSC Adults found in wet forests under rocks
and logs near streams. Uses cold, clear
streams for breeding.

May be Present as Nonbreeder. California giant salamanders are known to occur in the project vicinity in the residential hills surrounding the project site as close as 0.6 mile to the northwest, and along Permanente Creek 3.8 miles to the southwest (CNDDB 2024). Suitable aquatic habitat is present in Adobe Creek during period when it contains water, and vegetative debris in the riparian woodland along the creek provides upland refugial habitat.

Aquatic breeding habitat and riparian nonbreeding habitat to support this species are absent from the project site. However, small numbers of individuals from nearby locations along Adobe Creek or in the surrounding residential hills may disperse across the site on occasion.

Santa Cruz black
salamander
(Aneides niger)
CSSC Mixed deciduous and coniferous
woodlands and coastal grasslands.

Adults found under rocks, talus, and
moist woody debris.

Absent. Occurs in the Santa Cruz Mountains and foothills southeast of Interstate 280 (CNDDB 2024, iNaturalist 2024). However, no records are known from valley floor areas in the project vicinity northeast of Interstate 280 (CNDDB 2024, iNaturalist 2024). Determined to be absent.

Northern harrier
(Circus cyaneus)
CSSC
(nesting)
Nests in marshes and moist fields, forages
over open areas.

Absent. No suitable nesting or foraging habitat is present on the project site or in the surrounding vicinity, which is developed as a residential area. Determined to be absent.

Burrowing owl
(Athene cunicularia)
CSSC Nests and roosts in open grasslands and
ruderal habitats with suitable burrows,
usually those made by California ground
squirrels (Otospermophilus beecheyi).

Absent. No burrows of California ground squirrels are present on the project site to provide suitable nesting and roosting habitat for this species, and no suitable grasslands are present to provide foraging habitat. Not known to occur on the site, and the nearest occurrences are located several miles away along the periphery of the San Francisco Bay to the north and at Pearson-Arastradero Preserve to the west (Cornell Lab of Ornithology 2024). Determined to be absent.

Halsey House Demolition Project
Biological Resources Report
34 H. T. Harvey & Associates
August 2, 2024
Name *Status Habitat Potential for Occurrence on the Project Site Vaux’s swift
(Chaetura vauxi)
CSSC
(nesting)
Nest both in small colonies and as single
pairs, occupying cavities in large snags,
primarily in old-growth forests. They also
occasionally use artificial cavities such as
chimneys. Forage aerially.

May be Present. Known to nest in northwestern Santa Clara County (Rottenborn 2007b) and in eastern San Mateo County (Sequoia Audubon Society 2001) near the project location. The residential chimney in the Halsey House building on the site provides suitable nesting habitat for this species, and cavities large snags in surrounding areas at Redwood Grove Nature Preserve also provide suitable habitat. However, no Vaux’s swifts were observed on the site during the May 2024 site visit, indicating this species is not nesting on or adjacent to the site currently. Nonbreeding individuals may forage aerially over the project site, especially during migration.

Olive-sided flycatcher
(Contopus cooperi)
CSSC
(nesting)
Breeds in mature, primarily coniferous,
forests with open canopies, along forest
edges in more densely vegetated areas,
in recently burned forest habitats, and in
selectively harvested landscapes.

May be Present as Nonbreeder. Known to nest throughout much of San Mateo County and in northwestern Santa Clara County, including in the project vicinity (Sequoia Audubon 2001, Bousman 2007a). However, no suitable coniferous forest nesting habitat is present on or adjacent to the project site. Occasional nonbreeding individuals may forage on the site, especially during migration.

Loggerhead shrike
(Lanius ludovicianus)
CSSC
(nesting)
Nests in tall shrubs and dense trees;
forages in grasslands, marshes, and
ruderal habitats.

Absent. Known to nest in eastern San Mateo County (Sequoia Audubon Society 2001) and in northwestern Santa Clara County (Bousman 2007b). However, no grasslands are present on the site to provide suitable nesting and foraging habitat. Determined to be absent.

Yellow warbler
(Setophaga
petechia)
CSSC
(nesting)
Nests in riparian woodlands. May be Present as Nonbreeder (May be Present in Adjacent Areas).

No suitable riparian nesting habitat is present on the project site.

Potentially suitable riparian nesting habitat is present along Adobe Creek adjacent to the site; however, this species is an uncommon breeder in the region, and is not known to nest near the site (Cornell Lab of Ornithology 2024). Thus, the likelihood that this species would nest along Adobe Creek adjacent to the site is relatively low. The yellow warbler is an abundant migrant throughout the project region during the spring and fall, when nonbreeding individuals may forage in woodland habitat on the site.

Grasshopper sparrow
(Ammodramus
savannarum)
CSSC
(nesting)
Nests and forages in grasslands,
meadows, fallow fields, and pastures.

Absent. Known to nest and occur in the project region primarily in grasslands, such as at the Pearson-Arastradero Preserve approximately 3.1 miles to the west (Cornell Lab of Ornithology 2024). No suitable nesting or foraging habitat for this species is present on the project site due to the lack the grassland habitat and the presence of trees. Determined to be absent.

Halsey House Demolition Project
Biological Resources Report
35 H. T. Harvey & Associates
August 2, 2024
Name *Status Habitat Potential for Occurrence on the Project Site Pallid bat
(Antrozous pallidus)
CSSC Forages over many habitats; roosts in
caves, rock outcrops, buildings, and
hollow trees.

May be Present as Nonbreeder. Historically, pallid bats were likely present in a number of locations throughout the project region, but their populations have declined in recent decades. However, no known recent (after 1960) records of maternity colonies of this species are present on or adjacent to the project site (CNDDB 2024, iNaturalist 2024). Suitable roosting habitat for pallid bats is present in the Halsey House building, as well as in cavities in the large coast live oak tree on the project site. However, no pallid bats were detected during focused bat surveys in May 2024, and thus the species is not currently roosting on the site. Individuals from colonies in the region (especially in the Santa Cruz Mountains to the west) could occasionally forage on the project site.

Townsend’s big-eared
bat
(Corynorhinus
townsendii)
CSSC Roosts in caves and mine tunnels, and
occasionally in deep crevices in trees
such as redwoods or in abandoned
buildings, in a variety of habitats.

Present as Nonbreeder. An individual Townsend’s big-eared bat was observed roosting in the Halsey House building during the May 2024 site visit, and calls of this species were detected within and outside of the building during the acoustic survey. Based on the relatively small number of calls detected, as well as their timing, we determined in consultation with H. T. Harvey & Associates senior bat biologist David Johnston, Ph.D., that the Townsend’s big-eared bats using the building represent a non-maternity roost of a small number of individuals, likely consisting of one or few individual male bats, which is typical of this species.

Western red bat
(Lasiurus blossevillii)
CSSC Roosts in foliage in forest or woodlands,
especially in or near riparian habitat.

Low Potential for Occurrence. Western red bats occur in the project vicinity in low numbers as migrants and winter residents, but this species does not breed in the region. Individual western red bats may roost in the foliage of trees virtually anywhere on the project site, but are expected to roost primarily in riparian areas, such as along Adobe Creek to the north. Occasional individuals may forage over the project site year-round.

San Francisco duskyfooted woodrat
(Neotoma fuscipes
annectens)
CSSC Nests in a variety of habitats including
riparian areas, oak woodlands, and
scrub.

Present. Four active woodrat nests were detected on the ground in understory vegetation in coast live oak woodland habitat on the site during the focused survey in May 2024. Suitable habitat for this species is present throughout the coast live oak woodland habitat on the project site.

Halsey House Demolition Project
Biological Resources Report
36 H. T. Harvey & Associates
August 2, 2024
Name *Status Habitat Potential for Occurrence on the Project Site American badger
(Taxidea taxus)
CSSC Burrows in grasslands and occasionally in
infrequently disked agricultural areas.

Absent. Primarily occurs in extensive grasslands and scrub habitats.

This species is known to occur in the project region in the Santa Cruz Mountains to the west (CNDDB 2024, iNaturalist 2024). Occasional dispersants occur in the project vicinity, and an individual was detected 1.9 miles to the northwest near Foothill Expressway and Arastradero Road in 2019 (iNaturalist 2024). However, badgers are not expected to occur on the project site or establish a den there due to the lack of extensive grasslands present as well as the approximately 5-mile distance between the site and known populations in the Santa Cruz Mountains to the west. Determined to be absent.

State Fully Protected Species
Golden eagle
(Aquila chrysaetos)
SP Breeds on cliffs or in large trees (rarely on
electrical towers); forages in open areas.

Absent. The habitat on the site and within the surrounding Preserve is not sufficiently large to support a nesting pair of golden eagles, and the species would not forage on the site or in the Preserve due to the limited extent of habitat present and its isolation from more extensive habitats in the region, such as in the Santa Cruz Mountains, in the Stanford Dish area, and along the San Francisco Bay. Determined to be absent.

White-tailed kite
(Elanus leucurus)
SP Nests in tall shrubs and trees; forages in
grasslands, marshes, and ruderal
habitats.

May be Present. White-tailed kites are common residents in open areas in the project vicinity. Trees in the coast live oak woodland habitat on the project site provide suitable nesting habitat for this species. No white-tailed kites or nests of this species were observed on or adjacent to the site during the May 2024 site visit, and the species is not known to occur on the site (Cornell Lab of Ornithology 2024). However, occasional individuals will nest and forage in parks in urban areas, and up to one pair of white-tailed kites may nest in trees on or adjacent to the project site. Individuals of this species may forage on the site year-round.

Key to Abbreviations: Status: Federally Endangered (FE); Federally Threatened (FT); Federal Candidate for Listing (FC); Federally Proposed as Threatened (FPT); State Endangered (SE); State Threatened (ST); State Candidate for Listing (SC); State Fully Protected (SP); California Species of Special Concern (CSSC).

Halsey House Demolition Project
Biological Resources Report
37 H. T. Harvey & Associates
August 2, 2024

5.3 Sensitive Natural Communities, Vegetation Alliances, and Habitats
Natural communities have been considered part of the Natural Heritage Conservation triad, along with plants and animals of conservation significance, since the state inception of the Natural Heritage Program in 1979.

The CDFW determines the level of rarity and imperilment of vegetation types, and tracks sensitive communities in its Rarefind database (CNDDB 2024). Global rankings (G) of natural communities reflect the overall condition (rarity and endangerment) of a habitat throughout its range, whereas state (S) rankings are a reflection of the condition of a habitat within California. Natural communities are defined using NatureServe’s standard heritage program methodology as follows (Faber-Langendoen et al. 2012):

G1/S1: Critically imperiled
G2/S2: Imperiled
G3/S3: Vulnerable.

G4/S4: Apparently secure
G5/S4: Secure
In addition to tracking sensitive natural communities, the CDFW also ranks vegetation alliances, defined by repeating patterns of plants across a landscape that reflect climate, soil, water, disturbance, and other environmental factors (Sawyer et al. 2009). If an alliance is marked G1-G3, all of the vegetation associations within it will also be of high priority (CDFW 2024). The CDFW provides VegCAMP’s currently accepted list of vegetation alliances and associations (CDFW 2024).

Impacts on CDFW sensitive natural communities, vegetation alliances/associations, or any such community identified in local or regional plans, policies, and regulations, must be considered and evaluated under CEQA (Title 14, Division 6, Chapter 3, Appendix G of the California Code of Regulations). Furthermore, aquatic, wetland and riparian habitats are also protected under applicable federal, state, or local regulations, and are generally subject to regulation, protection, or consideration by the USACE, RWQCB, CDFW, and/or the USFWS.

5.3.1 Sensitive Natural Communities
A query of sensitive natural communities in the CNDDB (2024) identified four sensitive natural communities as occurring within the nine 7.5-minute USGS quadrangles containing or surrounding the project site: northern coastal salt marsh (Rank G3/S3.2), northern interior cypress forest (Rank G1/S1.2), serpentine bunchgrass (Rank G2/S2.2), and valley oak woodland (G3/S2.1). The coast live oak woodland on the project site does not the meet the definition of valley oak woodland natural community type due to the lack of dominance of valley oaks within the overstory. No sensitive natural communities are present on the project site.

Halsey House Demolition Project
Biological Resources Report
38 H. T. Harvey & Associates
August 2, 2024

5.3.2 Sensitive Vegetation Alliances
None of the habitat types on the site represent or include sensitive vegetation alliances.

5.3.3 CDFW Riparian Habitat
Due to its rarity and disproportionately high habitat values and functions to wildlife, the CDFW considers riparian habitat to be sensitive. As described above in Section 3.2.4, the CDFW would likely claim jurisdiction over areas at, and below, the top of bank lines on either side of Adobe Creek adjacent to the project site, as well as its associated riparian habitat, located approximately 16 feet off-site to the north. However, riparian habitat associated with Adobe Creek does not extend onto the project site, and it would not be directly or indirectly impacted by project activities.

5.3.4 Sensitive Habitats (Waters of the U.S./State)
No wetlands or other waters of the U.S./state occur on the project site. Adobe Creek located approximately 16 feet off-site to the north would likely be considered jurisdictional waters of the U.S. up to the OHW mark, and the RWQCB may claim the banks of Adobe Creek, and riparian habitat rooted below top of bank, as waters of the state. However, these potentially jurisdictional areas are located entirely off-site.

5.3.5 Nonnative and Invasive Species
Several nonnative, invasive plant species occur on the project site. Of these, several have a “limited” rating by the Cal-IPC, indicating they are invasive but their ecological impacts are minor on a statewide level or there was not enough information to justify a higher score. Their reproductive biology and other attributes result in low to moderate rates of invasiveness. Ecological amplitude and distribution are generally limited, but these species may be locally persistent and problematic. These “limited” species on the project site are pepper tree, variable burclover (Medicago polymorpha), curly dock, and soft chess (Bromus hordeaceus). Species with a “moderate” rating by the Cal-IPC have substantial and apparent–but generally not severe–ecological impacts on physical processes, plant and animal communities, and vegetation structure, and that their reproductive biology and other attributes are conducive to moderate-to-high rates of dispersal, though establishment would be generally dependent on ecological disturbance are: tall sock-destroyer (Torilis arvensis), greater periwinkle (Vinca major), Italian thistle, rose clover, tree of heaven, ripgut brome, and foxtail barley. Species with a “high” invasive rating by the Cal-IPC have the potential to cause severe ecological impacts on physical processes, plant and animal communities, and vegetation structure. Their reproductive biology and other attributes are conducive to moderate-to-high rates of dispersal and establishment, and most are widely distributed ecologically (Cal-IPC 2024). On the project site, species with a “high” rating are English ivy and French broom. Due to these species’ ubiquity in the region, project activities are not expected to result in the spread of nonnative and invasive plant species.

Halsey House Demolition Project
Biological Resources Report
39 H. T. Harvey & Associates
August 2, 2024
Section 6. Impacts and Mitigation Measures
CEQA and the State CEQA Guidelines provide guidance in evaluating impacts of projects on biological resources and determining which impacts will be significant. The Act defines “significant effect on the environment” as “a substantial adverse change in the physical conditions which exist in the area affected by the proposed project.”
Appendix G of State CEQA Guidelines provides a checklist of other potential impacts to consider when analyzing the significance of project effects. The impacts listed in Appendix G (Chapter IV) may or may not be significant, depending on the level of the impact. For biological resources, these impacts include whether the project would:

A. “have a substantial adverse effect, either directly or through habitat modifications, on any species identified as a candidate, sensitive, or special status species in local or regional plans, policies, or regulations, or by the California Department of Fish and Game or U.S. Fish and Wildlife Service” B. “have a substantial adverse effect on any riparian habitat or other sensitive natural community identified in local or regional plans, policies, regulations or by the California Department of Fish and Game or U.S. Fish and Wildlife Service”
C. “Have a substantial adverse effect on state or federally protected wetlands (including, but not limited to, marsh, vernal pool, coastal, etc.) through direct removal, filling, hydrological interruption, or other means” D. “interfere substantially with the movement of any native resident or migratory fish or wildlife species or with established native resident or migratory wildlife corridors, or impede the use of native wildlife nursery sites”
E. “conflict with any local policies or ordinances protecting biological resources, such as a tree preservation policy or ordinance”
F. “conflict with the provisions of an adopted Habitat Conservation Plan, Natural Community Conservation Plan, or other approved local, regional, or state habitat conservation plan” Potential impacts on biological resources as a result of the proposed project were systematically evaluated at the project level based on the project description provided to us by David J. Powers & Associates through July 2024. Based on this information, it is our understanding that all project impacts including grading, construction, and staging will occur within the limits of boundaries provided, and that all project impacts within this boundary will be permanent. For the purpose of this assessment, we have assumed that the proposed project would impact up to all 0.6 acre of the project site.

Halsey House Demolition Project
Biological Resources Report
40 H. T. Harvey & Associates
August 2, 2024
Potential impacts on existing biological resources were evaluated by comparing the quantity and quality of habitats present on the project site under baseline conditions to the anticipated conditions after implementation of the proposed project. Direct and indirect impacts on special-status species and sensitive natural communities were assessed based on the potential for the species, their habitat, or the natural community in question to be disturbed or enhanced following implementation of the proposed project.

6.1 Impacts on Special-Status Species: Have a substantial adverse effect, either directly or through habitat modifications, on any species identified as a candidate, sensitive, or special-status species in local or regional plans, policies, or regulations, or by the CDFW or USFWS (Less than Significant with Mitigation)

6.1.1 Impacts on Regionally Common Habitats and Associated Common Plant and Wildlife Species (Less than Significant)
Proposed project activities would result in the permanent removal of up to 0.3 acre of developed areas and 0.3 acre of coast live oak woodland on the project site. These impacts would reduce the extent of vegetation within the impact area and result in a reduction in the abundance of some of the common plant and wildlife species that occur there. However, the developed and coast live oak woodland habitats on the project site occur in a location in Los Altos that has been subject to disturbance in the past, is regularly disturbed by human activities, and are surrounded by developed residential areas such that these habitats do not provide regionally rare or especially high-value habitat for native vegetation, wildlife, or special-status species. In addition, these habitats are abundant and widespread regionally, are not particularly sensitive, and are not especially valuable (from the perspective of providing important plant or wildlife habitat) or exemplary occurrences of these habitat types.

Also, following demolition of the building and removal of building materials, the site will remain vegetated with ruderal herbaceous vegetation, which will still have some habitat value. Therefore, impacts on these habitats are considered less than significant under CEQA. Further, because the number of individuals of any common plant or animal species within these habitats, and the proportion of these species’ regional populations that could be disturbed, is very small, the project’s impacts would not substantially reduce regional populations of these species. Thus, these impacts do not meet the CEQA standard of having a substantial adverse effect, and would not be considered significant under CEQA.

6.1.2 Impacts on Water Quality and Special-Status Fish (Less than Significant) No direct impacts to Adobe Creek, which flows southwest to northeast approximately 16 feet from the project site, are proposed. Indirect impacts on water quality in the creek could potentially occur as a result of project activities, which are located upslope of the creek. Project activities could potentially impact the southern coastal roach and riffle sculpin in Adobe Creek due to a temporary increase in erosion, sedimentation, and turbidity in aquatic habitats located downstream of the work area. Additionally, minor spills of petrochemicals, hydraulic fluids, and solvents may occur during vehicle and equipment refueling. Such leaks/spills could adversely affect water quality downslope and downstream of construction activities.

Halsey House Demolition Project
Biological Resources Report
41 H. T. Harvey & Associates
August 2, 2024
Indirect impacts on water quality from construction of the project would be avoided and minimized by implementing erosion and sediment control measures, as well as BMPs for work near aquatic environments. In addition, in many Bay Area counties, including Santa Clara County, projects must also comply with the California RWQCB, San Francisco Bay Region, Municipal Regional Stormwater National Pollutant Discharge Elimination System Permit (Water Board Order No. R2-2015-0049). This permit requires that all projects implement BMPs and incorporate Low Impact Development practices into the design to prevent stormwater runoff pollution, promote infiltration, and hold/slow down the volume of water coming from a site after construction has been completed. In order to meet these permit and policy requirements, projects must incorporate the use of green roofs, impervious surfaces, tree planters, grassy swales, bioretention and/or detention basins, among other factors.

Compliance with these permit requirements will minimize the potential for impacts on water quality due to increases in erosion, sedimentation, and turbidity as well as releases of pollutants into Adobe Creek located downslope of the project site. Therefore, project activities are not expected to result in substantial adverse indirect effects on water quality or special-status fish, and such impacts would be less than significant.

6.1.3 Impacts on Nonbreeding Special-Status Invertebrates, Birds, and Mammals (Less than Significant)
Several special-status bird and mammal species may occur on the project site as nonbreeding migrants, transients, or foragers, but they are not known or expected to breed or occur in large numbers within or near the project impact area. These are the monarch butterfly, olive-sided flycatcher, mountain lion, and western red bat.

Few, if any, monarch butterflies are expected to be present on the project site given the small size of the site, the lack of milkweeds on the site, the lack of high-quality floral resources to support foraging individuals, and the lack of any evidence that an overwintering site is present. The olive-sided flycatcher (a California species of special concern) is not expected to occur on or close to the project site as a breeder due to the lack of suitable habitat, but individuals may occur occasionally as foragers during the nonbreeding season. Due to the site’s location in a low-density residential area on the periphery of open space areas of the Santa Cruz Mountains, individual mountain lions (a state candidate species) may briefly traverse the site as non-breeding dispersants or foragers, but individuals are not expected to linger for any length of time due to high levels of human activity.

The western red bat (a California species of special concern) may roost in small numbers in trees on the project site, but it does not breed in the project region.

Activities under the proposed project would have some potential to impact foraging habitats and/or disturb small numbers of individuals of these species. Construction activities might result in a temporary direct impact through the alteration of foraging patterns (e.g., avoidance of work sites because of increased noise and activity levels during maintenance activities) but would not result in the loss of individuals, as individuals of these species would move away from any construction areas or equipment before they could be injured or killed.

Further, the project site does not provide important foraging habitat used regularly or by large numbers of

Halsey House Demolition Project
Biological Resources Report
42 H. T. Harvey & Associates
August 2, 2024
individuals of any of these species. As a result, impacts of the project will have little impact on these species’ foraging habitat and no substantive impact on regional populations of these species. Therefore, this impact would be less than significant under CEQA.

6.1.4 Impacts on the White-Tailed Kite, Vaux’s Swift, and Yellow Warbler (Less than Significant)
The white-tailed kite (a state fully protected species) may nest in oak woodland habitat or landscape trees on and adjacent to the project site, the Vaux’s swift (a California species of special concern) may nest in the Halsey House chimney or in hollow snags in surrounding areas, and the yellow warbler (a California species of special concern) could potentially nest adjacent to the project site in riparian trees along Adobe Creek. These species are assessed together because the potential impacts of the project on these species would be similar.

Based on site observations, the areal extent of suitable habitats on and adjacent to the project site, and known nesting densities of this species, no more than one pair of white-tailed kites or yellow warblers, or two pairs of Vaux’s swifts, could potentially nest on or immediately adjacent to the project site. The project would not result in the permanent loss of suitable nesting habitat for the yellow warbler, as no activities are proposed within the riparian habitat along Adobe Creek. The project would result in the permanent loss of suitable nesting and foraging habitat for the white-tailed kite and Vaux’s swift, as well as suitable foraging habitat for the yellow warbler. In addition, activities that occur during the nesting season and cause a substantial increase in noise or human activity near active nests may result in the abandonment of active nests (i.e., nests with eggs or young).

Heavy ground disturbance, noise, and vibrations caused by project activities could potentially disturb nesting and foraging individuals and cause them to move away from work areas.

Because the number of nesting pairs that could be disturbed is very small (i.e., one or two pairs), the impacts of project activities would represent a very small fraction of the regional populations of these species. Therefore, neither the potential loss of individual white-tailed kites, Vaux’s swifts, or yellow warblers, nor the disturbance of nesting and foraging habitat, would rise to the CEQA standard of having a substantial adverse effect, and these impacts would thus not constitute a significant impact on these species or their habitat under CEQA.

However, as discussed in Section 3 above, all native migratory birds, including yellow warblers and white-tailed kites, are protected under the MBTA and California Fish and Game Code. Recommended measures to comply with these laws are provided under Section 7 Compliance with Additional Laws and Regulations, below.

6.1.5 Impacts on the San Francisco Dusky-Footed Woodrat (Less than Significant with Mitigation)
Four nests of San Francisco dusky-footed woodrats are present in coast live oak woodland habitat on the project site. Woodrats from this community will also forage in oak woodland habitats on the project site.

Construction of the project could result in the injury or mortality of individual woodrats and disturbance or destruction of nests and young, leading to increased predation risk on woodrats flushed from nests, as a result of vegetation clearing and operation of equipment.

Halsey House Demolition Project
Biological Resources Report
43 H. T. Harvey & Associates
August 2, 2024
Although woodrats are abundant in the project region, they are very important ecologically in that they provide an important prey source for raptors (particularly owls) and for predatory mammals, and their nests also provide habitat for a wide variety of small mammals, reptiles, and amphibians. Thus, in our opinion, impacts of the project on four woodrat nests would be considered significant under CEQA.

Implementation of Mitigation Measures BIO-1 through BIO-3 below would reduce this impact to a less-thansignificant level under CEQA.

Mitigation Measure BIO-1. Pre-Activity Survey. A qualified biologist will conduct a pre-activity survey for San Francisco dusky-footed woodrat nests within 30 days of the start of work activities. If active woodrat nests are determined to be present in, or within 10 feet of, the impact areas, Measures 2 and 3 below will be implemented, as appropriate.

Mitigation Measure BIO-2. Avoidance Buffers. Active woodrat nests that are detected within the work areas will be avoided to the extent feasible. Ideally, a minimum 10-foot buffer will be maintained between project activities and woodrat nests to avoid disturbance. In some situations, a smaller buffer may be allowed if, in the opinion of a qualified biologist, nest relocation (Measure BIO-3 below) would represent a greater disturbance to the woodrats than the adjacent work activities.

Mitigation Measure BIO-3. Nest Relocation. If avoidance of active woodrat nests within and immediately adjacent to the work areas is not feasible, then nest materials will be relocated to suitable habitat as close to the project area as possible (ideally, within or immediately adjacent to the project site). Relocation efforts will avoid the peak nesting season (February–July) to the maximum extent feasible.

Prior to the start of work activities, a qualified biologist will disturb the woodrat nest to the degree that all woodrats leave the nest and seek refuge outside of the construction area. Disturbance of the woodrat nest will be initiated no earlier than one hour before dusk to prevent the exposure of woodrats to diurnal predators. Subsequently, the biologist will dismantle and relocate the nest material by hand.

During the deconstruction process, the biologist will attempt to assess if there are juveniles in the nest.

If immobile juveniles are observed, the deconstruction process will be discontinued until a time when the biologist believes the juveniles will be capable of independent survival (typically after 2 to 3 weeks).

A no-disturbance buffer will be established around the nest until the juveniles are mobile. The nest may be dismantled once the biologist has determined that adverse impacts on the juveniles would not occur.

Implementation of these measures would minimize impacts of the project on the San Francisco dusky-footed woodrat, and no compensatory mitigation (beyond the relocation of nest materials described above) would be necessary.

Halsey House Demolition Project
Biological Resources Report
44 H. T. Harvey & Associates
August 2, 2024

6.1.6 Impacts on California Giant Salamander (Less than Significant) There is a low potential for California giant salamander to occur on the project site when construction occurs, and thus, the project is unlikely to impact this species. However, the possibility that a small number of individuals could occur on the project site cannot be eliminated. Individuals, if present, could be directly impacted by construction activities associated with the project. Individuals may be crushed by foot traffic, vehicles, or equipment, or crushed, trapped, and/or suffocated in their refugia by the passage of heavy equipment. An increase in native and nonnative predators attracted to the project site due to trash left on the work site might temporarily result in increased mortality of individuals of these species. Because project activities will be limited to upland areas, and no impacts on the species’ primary habitats (i.e., rocks and woody debris along Adobe Creek, or aquatic habitat in Adobe Creek) would occur, the number of individuals that could be impacted by the project is extremely small (i.e., one or two individuals of each species, at most).

Because these impacts would represent such a small proportion of these species’ regional populations, they would not rise to the CEQA standard of having a substantial adverse effect. For these reasons, project impacts on individual California giant salamanders would be less than significant under CEQA.

Project activities will be limited to upland areas, and no impacts on primary habitats for the California giant salamander (i.e., rocks and woody debris along the creek, or aquatic habitat in the channel) would occur.

However, project activities could indirectly impact suitable habitat for these species along Adobe Creek due to a temporary increase in erosion, sedimentation, and turbidity downslope of the work area. Additionally, minor spills of petrochemicals, hydraulic fluids, and solvents may occur during vehicle and equipment refueling. Such leaks/spills could adversely affect water quality downstream of construction activities, potentially impairing the health of eggs or larvae along the creek. However, potential indirect impacts on habitat and individuals due to a reduction in water quality would be avoided and minimized as described in Section 6.1.2 above, and would be less than significant under CEQA.

6.1.7 Impacts on Common and Special-Status Roosting Bats (Less than Significant with Mitigation)
The large coast live oak trees on the project site provide suitable roosting habitat for common bat species, such as the Yuma myotis, California myotis, and big brown bat (Eptesicus fuscus), as well as the pallid bat, a California species of special concern. The Townsend’s big-eared bat, a California species of special concern, is known to roost in the Halsey House building. These species are grouped together because project impacts on these species will be similar.

Although the trees on the site provide suitable roosting habitat, no evidence of a colony of roosting bats was detected in trees on the site during the May 2024 focused surveys, indicating that bats are not roosting in these trees currently, and no maternity colony is present. Due to the absence of bats during this survey, bats are not expected to be impacted during tree removal or modification.

Halsey House Demolition Project
Biological Resources Report
45 H. T. Harvey & Associates
August 2, 2024
One individual Townsend’s big-eared bat was observed roosting within the Halsey House structure during the May 7 focused survey, and small numbers of calls of this species were recorded within the structure during five nights of acoustic monitoring, indicating that a nonbreeding roost of one or a few individual male bats is present. When the Halsey House building is demolished, individual Townsend’s big-eared bats can be physically injured or killed, can be subjected to physiological stress from disturbance during torpor, or can face increased predation because of exposure during daylight. However, no nursing young would be affected. Impacts due to the loss of individual nonbreeding Townsend’s big-eared bats would be significant under CEQA, as this could have a substantial effect on the species’ small regional population. However, impacts due to the removal of the Halsey House building would be less than significant, as such roosting habitat for small numbers of nonbreeding individuals is widely available in the region. The following measure to avoid and minimize impacts on roosting Townsend’s big-eared bats will reduce project impacts on this species to less-than-significant levels under CEQA.

Mitigation Measure BIO-4. Bat Exclusion from Halsey House. Prior to the start of any projectrelated activities on the exterior or interior of the Halsey House building, a qualified bat biologist will guide and supervise the installation of appropriate exclusion devices to allow any roosting Townsend’s big-eared bats (and other bat species, if present) to vacate the roost and prevent bats from reoccupying these features before construction activities are initiated. Bird exclusion netting shall not be used because bats may become entangled in it, potentially leading to mortality. Exclusion materials will be inspected once per month between their installation and initiation of building demolition, to ensure that the materials are in good working order. If exclusion materials become compromised, the applicant shall perform maintenance on these devices, as directed by the qualified bat biologist.

6.2 Impacts on Sensitive Communities: Have a substantial adverse effect on any riparian habitat or other sensitive natural community identified in local or regional plans, policies, or regulations, or by the CDFW or USFWS (Less than Significant)

6.2.1 Impacts on Riparian Habitat or Other Sensitive Natural Communities (Less than Significant)
The CDFW defines sensitive natural communities and vegetation alliances using NatureServe’s standard heritage program methodology (CDFW 2024), as described above in Section 5.3. Aquatic, wetland, and riparian habitats are also protected under applicable federal, state, or local regulations, and are generally subject to regulation, protection, or consideration by the USACE, RWQCB, CDFW, and/or the USFWS (see Section 6.3 below). Project impacts on sensitive natural communities, vegetation alliances/associations, or any such community identified in local or regional plans, policies, and regulations, were considered and evaluated.

Adobe Creek flows from southwest to northeast adjacent to, but not through, the project site. The entirety of ground-disturbing project impacts will occur outside of the riparian corridor; thus, the proposed project will have no direct permanent or temporary impacts on riparian habitat. There is potential for indirect effects to

Halsey House Demolition Project
Biological Resources Report
46 H. T. Harvey & Associates
August 2, 2024
occur within riparian areas downslope of the project site if runoff from the project increases in intensity or frequency due to the proposed project. However, required construction-period BMPs and post-construction stormwater requirements will apply to the proposed project as discussed above in Section 6.1.2, and these requirements would avoid and reduce these impacts to a less-than-significant level.

No other sensitive natural communities are located on the project site or would be affected by the proposed project.

6.3 Impacts on Wetlands: Have a substantial adverse effect on state or federally protected wetlands (including, but not limited to, marsh, vernal pool, coastal, etc.) through direct removal, filling, hydrological interruption, or other means (Less than Significant)
No wetlands or other waters of the U.S./state are present on the project site. Adobe Creek, located 16 feet downslope of the project site to the northwest, supports other waters of the U.S./state but does not support wetlands. The project will avoid all direct impacts on state or federally protected aquatic habitats within this creek.

Because Adobe Creek is located downslope of the project site, there is some potential for the project to result in indirect impacts on other waters of the U.S./state within this creek. However, the project will comply with required construction period BMPs and post-construction storm water requirements will apply to the project as discussed above in Section 6.1.2, and these requirements would minimize increases of peak discharge of storm drain water and to reduce runoff of pollutants to protect water quality, including during construction.

Thus, with compliance with permit requirements, potential project impacts on other waters would be less than significant under CEQA.

6.4 Impacts on Wildlife Movement: Interfere substantially with the movement of any native resident or migratory fish or wildlife species or with established native resident or migratory wildlife corridors, or impede the use of native wildlife nursery sites (Less than Significant)

6.4.1 Impacts on Wildlife Movement (Less than Significant) For many species, the landscape is a mosaic of suitable and unsuitable habitat types. Environmental corridors are segments of land that provide a link between these different habitats while also providing cover.

Development that fragments natural habitats (i.e., breaks them into smaller, disjunct pieces) can have a twofold impact on wildlife: first, as habitat patches become smaller they are unable to support as many individuals (patch size); and second, the area between habitat patches may be unsuitable for wildlife species to traverse (connectivity).

Halsey House Demolition Project
Biological Resources Report
47 H. T. Harvey & Associates
August 2, 2024
Adobe Creek and the associated riparian corridor provide an important movement pathway for both aquatic and terrestrial wildlife species, connecting natural areas in the project vicinity. Songbirds that migrate along the Pacific Flyway disperse and forage along Adobe Creek in low to moderate numbers. Common, urban-adapted species such as raccoons and striped skunks may use the vegetation along the creek to move north and south through the Los Altos area. Small mammals, such as mice and shrews, will also use this vegetation to move between habitats. Common species of reptiles and amphibians, such as Pacific treefrogs and alligator lizards, amongst other species, are also expected to move along this corridor adjacent to the project site. The proposed demolition of Halsey House will not result in any loss of aquatic, wetland, or riparian habitat along Adobe Creek or in any substantial reduction in the value of the Adobe Creek corridor for wildlife movement. The removal of the Halsey House building within the 80-foot setback adjacent to the creek is expected to provide at least a minor improvement in conditions within the setback, potentially allowing animals to move more readily along the adjacent section of the creek. Thus, aquatic and terrestrial species would continue to be able to move north to south along Adobe Creek following completion of the project, without any substantial reduction in such movement. Therefore, the project would not interfere substantially with the movement of any native resident or migratory fish or wildlife species or with established native resident or migratory wildlife corridors, or impede the use of native wildlife nursery sites, and this impact is determined to be less than significant.

6.5 Impacts due to Conflicts with Local Policies: Conflict with any local policies or ordinances protecting biological resources, such as a tree preservation policy or ordinance (Less than Significant with Mitigation)

6.5.1 Impacts Due to the Removal of Ordinance-Sized Trees (Less than Significant) The project may remove existing trees on the site, including protected trees as defined by the City (see Section

3.3.1 above), and the applicant will submit a permit application for tree removal. In accordance with the City’s Municipal Code, the City will comply with applicable permit conditions including installing protective fencing; maintaining the existing grade out to the dripline of the tree; installing drain wells where impervious surfaces will be placed over a tree’s root system; repairing trees that are damaged by construction, and avoiding attachment of signs, wires, or other objects to the tree. Conditions of approval for tree removal may also include planting replacement trees. With the incorporation of these measures to ensure compliance with the Los Altos Hills Municipal Code, any potential impacts related to conflicts with local policies or ordinances protecting trees would be less than significant.

6.5.2 Impacts Due to Encroachment into the Stream/Riparian Corridor (Less than Significant)
To protect the ecological functions and values of a stream, buffers are often prescribed between new development and the stream (or its banks or associated riparian habitat). These buffers provide habitat for plants and animals associated with the stream, provide habitat connectivity (i.e., areas used for wildlife movement, including flight paths for birds), reduce indirect effects of adjacent development (e.g., noise, lighting, human activity, or invasive species) on the natural stream and riparian habitats, allow for the possible