To: Board of Supervisors
From: John Kopchik, Director, Conservation and Development
Report Title: 2025 Priority Conservation Areas Nominations
☒Recommendation of the County Administrator ☐ Recommendation of Board Committee
RECOMMENDATIONS:
1. ADOPT Resolution No. 2025-197 endorsing the nomination of four new Priority Conservation Areas (Tassajara Valley Preservation and Agricultural Enhancement Area, Briones Hills Agricultural Preserve Area, Iron Horse Trail Corridor, Marsh Creek Trail Corridor), and amendments to two existing Priority Conservation Areas (East Contra Costa County Habitat Conservation Plan/Natural Community Conservation Plan, Contra Costa County Agricultural Core) to be considered by the Association of Bay Area Governments.
2. AUTHORIZE the Conservation and Development Department Director or designee submit the required Priority Conservation Area nomination application and supporting materials to the Metropolitan Transportation Commission/Association of Bay Area Governments (MTC/ABAG).
FISCAL IMPACT:
No fiscal impact on the General Fund. Unincorporated County territory with approved MTC/ABAG Priority Conservation Area designations would be eligible for future Priority Conservation Area grant opportunities.
BACKGROUND:
Priority Conservation Areas (PCAs) are designated geographic areas identified to support the Bay Area’s regional conservation, resilience, and sustainability objectives. First introduced in 2007, the PCA program was updated in 2024 to ensure improved alignment with regional planning and funding opportunities. PCAs are characterized as one or more types:
• Natural Lands
• Agricultural & Working Lands
• Urban Greening
• Recreation
• Climate Adaptation (must overlap with one other PCA type)
The PCA designation encourages the preservation or enhancement of areas with high conservation values or needs. The PCA nomination process is locally driven, allowing jurisdictions to identify and propose areas of regional significance based on local priorities and community input. Jurisdictions that nominate PCAs gain access to the PCA Grant Program, which provides funding for acquisition, restoration, and public access improvements. Collaboration with community stakeholders, including non-government organizations (NGOs) and local residents, is strongly encouraged during the nomination process.
PCAs are voluntary designations, and as such, do not take precedence over local control. Under Government Code 65080 (b)(2)(K), a sustainable communities’ strategy (Plan Bay Area) does not supersede a city or County’s land use authority. Designation of a PCA does not affect the uses allowed for a property. The County General Plan and Zoning Code regulate these uses and designation of a PCA does not change the applicable General Plan land use designation or zoning district.
Proposed Amended Boundaries for Two Existing Priority Conservation Areas
Contra Costa County is the lead agency for the existing Priority Conservation Areas for the East Contra Costa County Habitat Conservation Plan/Natural Community Conservation Plan (HCP) and the Contra Costa County Agricultural Core. Staff is proposing amendments to the boundaries of both PCAs to address changes to the County’s Agricultural Core approved by the Board when adopting the new County General Plan in November 2024 and to address guidance from ABAG that PCAs can no longer overlap.
• East Contra Costa County Habitat Conservation Plan/Natural Community Conservation Plan (Central/East Contra Costa County), Natural Land PCA (approximately 59,000 acres). The HCP/NCCP provides regional conservation and development guidelines to protect natural resources while improving and streamlining the permit process for projects that will impact endangered species and sensitive habitat. The HCP/NCCP mainly offsets ecological impacts by conserving and restoring lands in a Preserve System. The Preserve System ultimately will encompass between 23,800 and 30,300 acres that will be acquired and managed to benefit the 28 plant and animal species covered by the HCP/NCCP, as well as the natural communities that they, and hundreds of other species, depend on for habitat. Staff is proposing boundary adjustments to reflect ABAG guidance, as summarized above.
• Contra Costa County Agricultural Core (East Contra Costa County), Agricultural Land PCA (approximately 12,000 acres). Much of the area in the Agricultural Core is prime agricultural land that is actively farmed with intensive row crops, orchards, and vineyards. Agricultural production is the primary use and takes precedent over other uses. Limited agricultural tourism activities that support the agricultural economy are consistent with the Agricultural Core. Staff is proposing boundary adjustments to reflect updates to the Agricultural Core land use designation in the County General Plan approved in November.
Analysis of Proposed New Priority Conservation Areas
Proposed PCA Name: Tassajara Valley Preservation and Agricultural Enhancement Area
Location: Southern Contra Costa County/Tri-Valley Area
Type(s): Natural Lands, Agricultural & Working Lands, Climate Adaptation
Area (acres): 17,665.2 acres
Justification and Eligibility:
• Regional Significance: The County, the City of San Ramon and the East Bay Regional Park District entered into the Agreement Regarding Preservation and Agricultural Enhancement in the Tassajara Valley on July 13, 2021 for the purpose of cooperating to preserve and enhance agricultural uses within the Tassajara Valley. Much of the Tassajara Valley includes undeveloped rural land that has historically been comprised of agricultural, resource conservation and park and recreation areas. Most areas are non-irrigated, rural lands that may support grazing and dryland farming, though it also includes non-prime, productive agricultural lands. Lands also include ecologically significant or environmentally sensitive areas that may not be within publicly-owned parkland.
• Alignment with PCA Types: The Tassajara Valley Preservation and Agricultural Enhancement Area is outside the County’s Urban Limit Line which prevents sprawl by establishing a boundary beyond which no urban land uses can be designated. The Natural Lands PCA and Agricultural & Working Lands PCA objectives align with the County’s policies for preserving this area for non-urban uses. Doing so also aligns with the Climate Adaption PCA objectives by maintaining habitat migration opportunities and serving as an open space buffer from urban areas that could be susceptible to wildfire risk.
• Conservation and Community Goals: This PCA nomination aligns with the County’s General Plan goals for: 1) Maintaining a thriving, sustainable, and competitive agricultural economy, 2) Preserving and enhancing ecological resources, and wildlife habitat, 3) Protecting natural watercourses, riparian corridors, and wetland areas that improve habitat, water quality, wildlife diversity, stormwater flows, and scenic values, and 4) Minimizing injury, loss of life, and damage to property from wildfire hazards.
Proposed PCA Name: Briones Hills Agricultural Preserve Area
Location: North West/Central Contra Costa County, State Route 4 Corridor
Type(s): Natural Lands, Agricultural & Working Lands, Climate Adaptation
Area (acres): 7,887 acres
Justification and Eligibility:
• Regional Significance: The County and the Cities of Martinez, Pleasant Hill, Lafayette, Orinda, Richmond, San Pablo, Pinole and Hercules approved a joint resolution in 1987 establishing an agricultural preservation area in the Briones Hills. The proposed PCA is for portions of the Briones Hills area covered by the 1987 joint resolution that are outside the current County ULL, outside Cities, not on land owned by a special district and not inside other existing PCAs. The Briones Hills area is comprised of mostly open space and grazing land with hilly or varying topography, but includes corridors of non-prime, productive agricultural lands. The Pinole Creek Watershed (Lead: Contra Costa Resource Conservation District) is adjacent to the southwest, thus creating a contiguous PCA covering a predominant swath of the open space areas between west and central Contra Costa County.
• Alignment with PCA Types: Like the Tassajara Valley, the Briones Hills Agricultural Preserve Area is outside the County’s Urban Limit Line which prevents sprawl by establishing a boundary beyond which no urban land uses can be designated. The Natural Lands PCA and Agricultural & Working Lands PCA objectives align with the County’s policies for preserving this area for non-urban uses. Doing so also aligns with the Climate Adaption PCA objectives by maintaining habitat migration opportunities and serving as an open space buffer from urban areas that could be susceptible to wildfire risk.
• Conservation and Community Goals: This PCA nomination aligns with the County’s General Plan goals for: 1) Maintaining a thriving, sustainable, and competitive agricultural economy, 2) Preserving and enhancing ecological resources, and wildlife habitat, 3) Protecting natural watercourses, riparian corridors, and wetland areas that improve habitat, water quality, wildlife diversity, stormwater flows, and scenic values, and 4) Minimizing injury, loss of life, and damage to property from wildfire hazards.
Proposed PCA Name: Iron Horse Trail Corridor
Location: Corridor extends from State Route 4 to Contra Costa County/Alameda County line, paralleling Interstate 680 Corridor
Type(s): Urban Greening, Recreation, Climate Adaptation
Area (acres): 383.21 acres
Justification and Eligibility:
• Regional Significance: The Iron Horse Trail corridor (approximately 18.5 miles within Contra Costa County) lies within 1.5 miles, or a comfortable walking distance, of over 340,000 residents (151,000 commuters) and 3 miles, or a comfortable bicycling distance, of 425,000 residents (200,000 commuters). The corridor is only a few blocks from both the Pleasant Hill and Dublin/Pleasanton BART stations. The trail connects workers to dense employment areas like Bishop Ranch in San Ramon and Contra Costa Centre Transit Village in Walnut Creek and provides recreational users with an active transportation route that is separated from vehicles. The Iron Horse Trail is one of the largest and oldest multi-use trails in the San Francisco Bay Area and is a treasured community asset.
• Alignment with PCA Types: In July 2020 the County Board of Supervisors adopted the Iron Horse Trail Active Transportation Corridor Study. The Study analyzed various corridor improvements, including shade trees, green bioretention infrastructure, linear parks, and student and community gardens. Access improvements within and to/from the corridor would enhance existing and future trail use and improve access to adjacent and nearby parks, regional trails and recreation opportunities. Implementing the Study recommendations will enhance user comfort and the overall riding experience which will also increase demand.
• Conservation and Community Goals: This PCA nomination aligns with the goals of the County General Plan: Support people who walk, bike, roll, or use mobility devices by creating safe, equitable, connected, and comfortable facilities for all ages and abilities; and Climate Action and Adaptation Plan: Improve the viability of walking, biking, zero-emission commuting, and using public transit for travel within, to, and from the county.
Proposed PCA Name: Marsh Creek Trail Corridor
Location: Corridor extends from Clayton city limit to Round Valley Regional Preserve
Type(s): Natural Lands, Agricultural & Working Lands, Recreation, Climate Adaptation
Area (acres): 4,169.74 acres
Justification and Eligibility:
• Regional Significance: The approximately 12.5-mile Marsh Creek corridor travels through rolling hills between the communities of Clayton on the west and Brentwood on the east. Most of the land along the corridor is dedicated to agricultural, open space, and parks and recreation. Several parks and destinations for recreational activities exist along the corridor. Access to Mt. Diablo State Park is provided via multiple staging areas and trailheads along Marsh Creek Road and Morgan Territory Road. Round Valley Regional Preserve is accessed via a staging area and parking lot located at the eastern end of the study corridor. Marsh Creek Road also provides access to Morgan Territory Road and the Morgan Territory Regional Preserve. The creekshed is home to multiple habitat types, including agricultural lands, grasslands, various oak woodlands, and a riparian corridor along the creek. The proposed Marsh Creek trail alignment would create a new public connection from the eastern edge of the City of Clayton to the Round Valley Regional Preserve at the eastern end of the corridor.
• Alignment with PCA Types: The purpose of the Marsh Creek Corridor Multi-Use Trail Feasibility Study was to develop concept alignments for a multi-use public trail that provides a safe, useful, and enjoyable transportation corridor that supports multiple forms of non-motorized travel, including pedestrians, bicyclists, and equestrians. This section of the Marsh Creek Trail would connect to the existing Marsh Creek Trail in Brentwood, the Mokelumne Coat to Crest Trail, Big Break Regional Shoreline Trail, and ultimately the Great California Delta Trail network. A future trail project would also seek to identify restoration opportunities along Marsh Creek to occur in conjunction with trail development opportunities. A field review and meeting with a handful of property owners in the eastern section of the project area. Participants shared their concerns about the impacts to local ranching operations, fire-safety and personal liability concerns, and knowledge about the seasonal variations in water heights and banks that regularly occur in the creek shed. The field visit supported the modifications made to the alignments which emphasized moving the trail away from private residences.
• Conservation and Community Goals: This PCA nomination aligns with the goals of the County General Plan: Support people who walk, bike, roll, or use mobility devices by creating safe, equitable, connected, and comfortable facilities for all ages and abilities; and Climate Action and Adaptation Plan: Improve the viability of walking, biking, zero-emission commuting, and using public transit for travel within, to, and from the county.
Mapping and Boundary Details
The proposed PCA satisfies the MTC/ABAG eligibility map requirements which ensure consistency in PCA nominations across the region. The proposed PCA boundaries have been carefully mapped to meet eligibility and avoid overlap with ineligible areas. Maps are provided in Exhibit A.
Community Support
These nominations reflect the priorities outlined in Contra Costa County 2045 General Plan (November 2024), Iron Horse Corridor Active Transportation Study (June 2020), and the Marsh Creek Corridor Multi-Use Trail Feasibility Study (May 2023). Those processes included input collected in various ways (online surveys, workshops, community meetings, public hearings, etc.) from local residents, business owners, interested agencies, local stakeholders and community organizations.
CONSEQUENCE OF NEGATIVE ACTION:
Rejecting the PCA nominations would preclude eligibility for MTC/ABAG Priority Conservation Area grant opportunities.
THE BOARD OF SUPERVISORS OF CONTRA COSTA COUNTY, CALIFORNIA
and for Special Districts, Agencies and Authorities Governed by the Board
body
IN THE MATTER OF: Endorsing the nomination of four new Priority Conservation Areas (Tassajara Valley Preservation and Agricultural Enhancement Area, Briones Hills Agricultural Preserve Area, Iron Horse Trail Corridor, Marsh Creek Trail Corridor), and amendments to two existing Priority Conservation Areas (East Contra Costa County Habitat Conservation Plan/Natural Community Conservation Plan, Contra Costa County Agricultural Core) to be adopted by the Association of Bay Area Governments.
WHEREAS, the Association of Bay Area Governments (ABAG) has updated the Priority Conservation Area (PCA) planning framework which creates a regionally consistent approach to designate key areas for conservation and nature-based improvements;
WHEREAS, PCAs include diverse landscapes such as nature preserves, farms, ranches, trails, urban parks, and areas that benefit from urban greening or nature-based climate adaptation solutions;
WHEREAS, the PCA planning framework includes locally nominated PCAs as locations to coordinate local and regional planning for the conservation of regionally significant areas which are adopted by the ABAG;
WHEREAS, the PCA designation provides opportunities for grant funding to support conservation, restoration, and recreational projects, helping to achieve both local and regional conservation goals;
WHEREAS, the updated PCA criteria adopted by ABAG in 2024 aim to ensure alignment with regional sustainability and conservation priorities;
WHEREAS, the County is the lead agency for two existing Priority Conservation Areas (East Contra Costa County Habitat Conservation Plan/Natural Community Conservation Plan and Contra Costa County Agricultural Core) and is proposing amendments that align them with the County’s Agricultural Core boundary;
WHEREAS, the Tassajara Valley Preservation and Agricultural Enhancement Area includes undeveloped rural land that has historically been comprised of ecologically significant or environmentally sensitive agricultural, resource conservation and park and recreation areas;
WHEREAS, the Briones Hills Agricultural Preserve Area is comprised of mostly open space and grazing land with hilly or varying topography, but includes corridors of non-prime, productive agricultural lands;
WHEREAS, the Iron Horse Trail Corridor is one of the largest and oldest multi-use trails in the San Francisco Bay Area and is a treasured community asset;
WHEREAS, the Marsh Creek Trail Corridor has several parks and destinations for recreational activities along the corridor, including access to Mt. Diablo State Park, and contains a creekshed that is home to multiple habitat types, including agricultural lands, grasslands, various oak woodlands, and a riparian corridor along the creek;
WHEREAS, the designation of the Tassajara Valley Preservation and Agricultural Enhancement Area, Briones Hills Agricultural Preserve Area, Iron Horse Trail Corridor, and Marsh Creek Trail Corridor as a Priority Conservation Areas does not alter existing land use designations, zoning, or the County’s land use authority;
WHEREAS, the Board of Supervisors recognizes the importance of nominating these PCA areas to ensure eligibility for future funding and support for projects that enhance these areas;
NOW, THEREFORE, BE IT RESOLVED
1. The Board of Supervisors endorses amendments for two existing Priority Conservation Areas (East Contra Costa County Habitat Conservation Plan/Natural Community Conservation Plan, Contra Costa County Agricultural Core) and is proposing amendments that align them with the County’s Agricultural Core boundary; and
2. The Board of Supervisors endorses the nomination of the Tassajara Valley Preservation and Agricultural Enhancement Area, Briones Hills Agricultural Preserve Area, Iron Horse Trail Corridor, and Marsh Creek Trail Corridor as Priority Conservation Areas to be adopted by the Association of Bay Area Governments, recognizing their regional and local significance; and
3. Authorizes the Conservation and Development Department Director or designee to complete and submit the required PCA nomination forms and any supporting materials to the Metropolitan Transportation Commission/Association of Bay Area Governments.