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Project Title: |
2026 Urban Limit Line Renewal |
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County File Number: |
GP25-0001 |
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Applicant/Owner: |
County-initiated |
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Project Location: |
Countywide |
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California Environmental Quality Act (CEQA) Status: |
To be determined once project description becomes stable. |
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Project Planner: |
Will Nelson, Principal Planner will.nelson@dcd.ccounty.us (925) 655-2898 |
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Staff Recommendation: |
Conduct a study session and provide comments on a potential 2026 Urban Limit Line ballot measure. |
I. BRIEF BACKGROUND ON URBAN LIMIT LINE
On November 6, 1990, Contra Costa County voters approved Measure C, the 65/35 Contra Costa County Land Preservation Plan (the “65/35 Plan”), which established various mechanisms aimed at containing urban sprawl and protecting resources like agricultural land and scenic ridges. The most significant and impactful of these mechanisms are the 65/35 Land Preservation Standard (the “65/35 Standard”) and Urban Limit Line (ULL). Pursuant to the 65/35 Standard, no more than 35 percent of the land in the county may be designated for urban uses (i.e., residential, commercial, industrial, and mixed-use) in the General Plans of the County and 19 cities, and at least 65 percent must be designated for agriculture, open space, parks, and other non-urban uses. Meanwhile, the ULL establishes a boundary beyond which no urban land uses may be designated. Working together, the 65/35 Standard and ULL limit the geographic extent of urban development in the county. Measure C was set to expire on December 31, 2010.
On November 7, 2006, county voters approved Measure L, which carried forward most of the elements of Measure C while adding provisions for periodic ULL reviews and establishing different processes for expanding the ULL by 30 acres or fewer and more than 30 acres. Measure L is in effect through December 31, 2026.
On February 25, 2025, staff made a presentation to the Board of Supervisors on a potential 2026 ballot measure to renew the ULL. The Board directed staff to complete the tasks necessary for placing a measure on the June 2026 Primary Election ballot and indicated a strong preference for this work to be completed in 2025.
II. ULL ISSUES FOR CONSIDERATION
A. Effects of County-Sponsored ULL Ballot Measure on Cities
In November 2004, county voters approved Measure J, an extension of the Contra Costa Transportation Authority (CCTA) half-cent transportation sales tax originally approved through passage of Measure C in 1988 (this is different from the Measure C that created the ULL). The Growth Management Program (GMP), a component of Measure J, required the County and each of the 19 cities in the county to adopt and continuously comply with a mutually agreed-upon ULL or their own voter-approved ULL to receive their shares of Measure J Local Street Maintenance and Improvement Funds (also known as “return to source funds”) and be eligible to receive Measure J Transportation for Livable Community Funds. The effort to create a mutually agreed-upon ULL failed. Following readoption of the County ULL in 2006, 16 of the 19 cities adopted the County’s ULL to comply with Measure J. Pittsburg, Antioch, and San Ramon adopted their own ULL (which San Ramon refers to as the Urban Growth Boundary [UGB]). Staff reviewed the ULL adoption resolutions for the cities that adopted the County’s ULL. Each resolution explicitly states that the ULL adopted by the voters through Measure L is the ULL the city is adopting. Each city also adopted procedures for adjusting the ULL consistent with CCTA’s “Principles of Agreement for Establishing the Urban Limit Line,” with some adding provisions to address local issues. Nothing in any of the cities’ resolutions suggests that their ULLs could be affected by future actions of the County, such as a subsequent ULL ballot measure. Staff concluded that the 2026 ULL ballot measure will not affect the cities’ ULLs in any way.
B. Relationship between ULL Ballot Measure, General Plan, and Ordinance Code
Measure C amended the General Plan Land Use Element and Ordinance Code, specifically the Zoning Code (Title 8), to establish the 65/35 Plan and ULL. Specific text was added to both documents and the voter-approved ULL map was added to the General Plan. Measure L modified the ULL map and amended the text of the General Plan and Zoning Code to extend the term of the 65/35 Plan and add procedures related to expansion and review of the ULL. The 2026 ballot measure also will contain a ULL map and text governing administration and enforcement of the ULL.
The provisions of Measure L set to expire at the end of 2026 include the term of the 65/35 Plan and most procedures for expanding and periodically reviewing the ULL, but not the ULL itself. Were the provisions of Measure L to expire without a replacement voter-approved measure, then the 65/35 Plan and those procedures for expanding and reviewing the ULL would no longer be in effect, but the ULL would remain as part of the General Plan. The 65/35 Plan’s prohibition on designating land for urban uses outside the ULL would sunset, but General Plan policy LU-P2.3 provides a backstop by limiting development outside the ULL to non-urban uses. Absent Measure L’s requirement for a 4/5 supermajority vote to expand the ULL, the Board could expand it through the standard process to adopt a General Plan amendment (GPA), which requires a simple majority vote.
The Land Use Element and Growth Management Element of the 2045 General Plan each contain policies stating that a voter-approved ULL will be maintained. The Growth Management Element is consistent with the Measure J GMP. Failure to maintain a voter-approved ULL would cause the Growth Management Element to become inconsistent with the GMP and jeopardize the County’s “return to source” road maintenance funds, which are about $2 million annually.
C. Term of the ULL
Measures C and L each had terms lasting 20 years. At its February 25 meeting the Board indicated its preference for a 25-year term for the new measure. If approved by the voters, this would extend the ULL to 2051.
D. Periodic ULL Reviews
Measure L contains two provisions for reviewing the ULL: optional 5-year reviews and a mandatory mid-term (year 2016) review. The purpose of the mid-term review was to determine whether any changes to the boundary of the ULL were warranted, “based on facts and circumstances resulting from the County’s participation with the cities in a comprehensive review of the availability of land in Contra Costa County sufficient to satisfy housing and jobs needs for 20 years thereafter.”
In its February presentation to the Board, staff recommended against including periodic review requirements in the 2026 ballot measure for the following reasons:
• The 2016 mid-term review, conducted in cooperation with the cities, demonstrated substantial development capacity within the ULL through 2036. “Higher density” and “lower density” development scenarios were analyzed and staff determined that inside the ULL there was capacity for 67,400 to 110,800 residential units and 172,000 to 190,700 jobs.
• The County’s 2045 General Plan, adopted in November 2024, provides substantial development capacity in the unincorporated areas through its land use designations. The General Plan EIR analyzed the impacts of developing 23,200 residential units, 1.2 million square feet of commercial space, and 5 million square feet of industrial space on vacant and underutilized land inside the ULL through the General Plan’s 2045 horizon year.
• Every jurisdiction in California is required to update the Housing Element of its General Plan every eight years. A significant component of the Housing Element update is the housing sites inventory, which demonstrates each jurisdiction’s capacity to accommodate its Regional Housing Needs Allocation (RHNA). The California Department of Housing and Community Development, which reviews Housing Elements and certifies their compliance with State law, will not certify a Housing Element with an inadequate housing sites inventory. The County and each of the 19 cities will therefore be required to complete three comprehensive housing capacity analyses over the course of a 25-year ULL extension.
The Board indicated that it may be appropriate to link some form of ULL review to the Housing Element update process.
E. Process and Findings for Adjusting the ULL
The County processes adjustments to the ULL as GPAs, making them subject to State and County regulations and policies governing GPAs. ULL expansions are subject to additional procedures contained in Measure L. Expansions of 30 or fewer acres require a 4/5 vote of the Board after making at least one of the following findings:
(i) A natural or man-made disaster or public emergency has occurred which warrants the provision of housing and/or other community needs within land located outside the ULL.
(ii) An objective study has determined that the ULL is preventing the County from providing its fair share of affordable housing or regional housing as required by State law, and the Board of Supervisors finds that a change to the ULL is necessary and the only feasible means to enable the County to meet these requirements of State law.
(iii) A majority of the cities that are party to a preservation agreement and the County have approved a change to the ULL affecting all or any portion of the land covered by the preservation agreement.
(iv) A minor change to the ULL will more accurately reflect topographical characteristics or legal boundaries.
(v) An objective study has determined that a change to the ULL is necessary or desirable to further the economic viability of the East Contra Costa County (Byron) Airport, and either mitigate adverse aviation related environmental or community impacts attributable to Buchanan Field, or further the County’s aviation-related needs.
(vi) A change is required to conform to applicable California or federal law.
(vii) A five-year cyclical review of the ULL has determined, based on the criteria and factors for establishing the ULL set forth above, that new information is available (from city or County growth management studies or otherwise) or circumstances have changed, warranting a change to the ULL.
ULL expansions exceeding 30 acres must be approved by a 4/5 vote of the Board after making at least one of these findings, then receive countywide voter approval.
Adjustments to the ULL are rare; it has been moved only six times (1993, 1996, 2000, 2005, 2009, and 2021) since inception in 1990. Just once has the ULL been expanded as part of a private development proposal. The ULL expansion process is difficult by design, and the Board indicated no intention to fundamentally change the procedures.
F. Urban Limit Line Map
General Plan Land Use Element Figure LU-2, Urban Limit Line, is the official ULL map approved by the voters in 2006, with amendments adopted in 2009 and 2021. Attachment A includes Figure LU-2 (labeled as Figure 1: Current County Urban Limit Line) followed by a series of maps depicting potential ULL adjustments. These maps were presented for the Board’s consideration on February 25. The adjustments constitute 10,787 acres of ULL contraction and 1,634 acres of ULL expansion, for a net contraction of 9,153 acres. These acreages do not include the potential Byron Airport Study Area expansion discussed in section G below. Proposed ULL adjustments are categorized as follows:
Contractions
(i) Restricted Development, 3,233 acres. These contractions would move outside the ULL land with permanent development restrictions. These restrictions include ownership by government agencies such as the East Bay Regional Park District and County Flood Control District; scenic, conservation, and agricultural easements; and grant deeds of development rights or similar instruments in favor of the County or other government entities. Most of this acreage is already designated Resource Conservation (RC), Parks and Recreation (PR), or Public and Semi-Public (PS) in the General Plan. These designations are non-urban and drastically limit development potential. The remaining acreage is designated Agricultural Lands (AL), which is also non-urban.
(ii) Buffers, 1,488 acres. These contractions would move outside the ULL land set aside as buffers around subdivisions, cemeteries, and industrial facilities (e.g., refineries and quarries). Nearly all this acreage is already designated RC in the General Plan. A small amount is designated AL.
(iii) Constraints, 4,393 acres. These contractions move outside the ULL land with development constraints such as steep slopes, high or very high fire hazards, flood hazards, high quality agricultural soil, access issues/isolation, or lack of access to utilities. These lands are inappropriate for urban development. All this acreage has a non-urban land use designation in the General Plan except for approximately 20.5 acres in Diablo and 1.1 acres in Byron designated for residential development. If those 21.6 acres were moved outside the ULL, then DCD would process a GPA in the future to change the land use designation to one that is non-urban, likely AL.
(iv) Align with City Limits, 888 acres. These contractions move the ULL inward to align with the incorporated limits of San Ramon, Pittsburg, and Antioch, the cities that adopted their own ULL or equivalent Urban Growth Boundary instead of adopting the County’s 2006 ULL. All land shown to be moved outside the ULL has a non-urban General Plan land use designation.
(v) Shoreline Simplification, 785 acres. These contractions smooth out the ULL along the shoreline and place undevelopable islands in San Pablo Bay and the Delta outside the ULL.
Expansions
(i) Existing Development, 131 acres. These expansions would bring inside the ULL certain properties occupied by homes, businesses, a sports facility, and a former fire station. Some of these properties already have an urban General Plan land use designation despite being outside the ULL.
(ii) Improved Clarity, 159 acres. These expansions eliminate existing “islands” or holes in the ULL that were created when land was annexed to cities, and new islands that would be created by other recommended expansions and contractions. They also eliminate instances where the ULL unnecessarily splits parcels. Approximately 82 of these acres are owned and permanently protected by the National Park Service or East Bay Regional Park District. The remaining 77 acres are designated AL or RC in the General Plan. Most of this acreage has no urban development potential.
(iii) Align with City Limits, 923 acres. These expansions move the ULL outward to align with city limits. Approximately 823 of these acres are within San Ramon’s city limits. These expansions have no regulatory effect on the County or cities.
(iv) Shoreline Simplification, 421 acres. These expansions smooth out the ULL along the shoreline. Approximately 387 acres are within cities and include water adjacent to existing ports and marinas. ULL changes within the cities have no regulatory effect on the County or cities. The remaining 34 acres are in Rodeo and unincorporated Antioch and include water adjacent to existing marinas. These areas have a Water land use designation in the General Plan. The Water designation allows shipping terminals, marinas, docks, and other marine-oriented uses and may exist inside and outside the ULL. Moving these areas inside the ULL is therefore inconsequential from a regulatory standpoint.
(v) Byron Airport Study Area, approximately 500 acres. This expansion, shown in detail on the maps marked “H” in Attachment A, involves land between the airport and Byron Highway and is the only expansion contemplated as a precursor to potential future development.
ULL expansions do not approve new development by themselves. Subsequent GPAs would be required to change non-urban land use designations to urban in support of more intense land uses. Such GPAs could be adopted only if they were consistent with goals and policies of the General Plan.
G. Byron Airport Study Area
The County owns and operates two general aviation airports, Buchanan Field Airport near Concord and Pleasant Hill, and Byron Airport south of Byron. The airports are self-funded and generate revenue for the County’s General Fund from leases, licenses, aircraft tax, sales tax, and other sources related to activities on airport property. While Byron Airport embodies a significant investment of public resources, it has historically operated at a deficit. The airport’s potential as a job center and economic engine is limited by scarcity of developable land on and near the airport property and inadequate road and utility infrastructure at the airport and in the vicinity. More development not only equates to more revenue, but private development projects typically construct or improve infrastructure. Therefore, adequate acreage should be available to accommodate projects large enough to absorb the cost of installing the necessary infrastructure.
The ULL around Byron Airport is a nebulous form that was adopted several years before the airport opened in 1994. Today it poorly reflects actual land use and development potential around the airport. About 75 percent of the non-airport land that surrounds the airport and is within the ULL is owned by the County or East Bay Regional Park District. This land is permanently protected. The remaining 25 percent is under private ownership and designated AL in the General Plan, which does not allow urban development. Urban services such as water and sewer are unavailable.
The possibility of adjusting the ULL around the airport has been contemplated since Measure C created the ULL in 1990, as evidenced by the finding to expand the ULL that specifically addresses the airport’s economic viability and furtherance of the County’s aviation-related needs. The logical location for a ULL expansion is to the east and northeast, between the airport and Byron Highway, where several hundred acres of generally poor agricultural land remain mostly undeveloped. This area is flat, not a conservation priority under the East Contra Costa County Habitat Conservation Plan/Natural Community Conservation Plan, and within the State Route 239 corridor being planned by CCTA.
Staff presented the Board with two procedural options for expanding the ULL to the east/northeast of the airport. The first is to include the expansion on the ULL map presented to the voters as part of the ballot measure. If the voters approved the ballot measure, then the ULL as shown on the map would take effect immediately. The second option is for the ballot measure ULL map to show a maximum extent of potential expansion with accompanying language authorizing the Board to move the ULL within and up to the boundary of that area in the future. Because such expansion would almost certainly exceed 30 acres, the ballot measure would make clear that its adoption by the voters satisfied the requirement for a countywide vote for a ULL expansion exceeding 30 acres. It would also be desirable for the ballot measure to explain the purpose of a future expansion, which would be to facilitate development of aviation-related uses that depend on proximity to the airport and restrict future development to just these aviation-related uses. Both options include contraction of the ULL by significantly greater acreage on the airport’s north, west, and south sides.
Staff suggested to the Board that the second option, obtaining voter authorization to expand the ULL but deferring actual expansion, is preferable. The County has not been approached with a proposal for aviation-related development near the airport, so there is no immediate need to move the ULL. The State Route 239 right-of-way alignment has not been finalized and that could affect the ideal location of the ULL boundary. Deferring a ULL expansion until needed also guards against real estate speculation. The Board did not explicitly endorse either option.
III. OUTREACH
The Board directed staff to conduct public outreach including at least one presentation to the County Planning Commission (CPC), consultation with the 19 cities in the county, and distribution of materials to the 13 Municipal Advisory Councils (MACs). The Envision Contra Costa website and mailing list, which has over 1,200 subscribers representing a wide range of interests, is also being utilized. Staff is available to meet with any individual or entity wishing to discuss the ULL.
IV. SCHEDULE
The Primary Election is scheduled for June 2, 2026. The schedule for completing the tasks necessary to place the ULL renewal measure on the Primary Election ballot is as follows:
• March-June 2, 2025: Staff seeks input from the public, cities, MACs, and CPC.
• June/July 2025: Board meets to review the comments received, refine draft ballot measure, and provide direction to staff.
• June/July 2025-Fall 2025: Staff conducts environmental (CEQA) review.
• December 2025 (sooner, if possible): Board meets to adopt the CEQA document and forward the final ULL measure to the County Elections Department for inclusion on Primary Election ballot.
V. ATTACHMENTS
A. Map Series Depicting Potential ULL Adjustments