To: Board of Supervisors
Department or Agency Name(s): Sonoma County Public Infrastructure
Staff Name and Phone Number: Johannes J. Hoevertsz, 707-565-2550
Vote Requirement: Majority
Supervisorial District(s): Countywide
Title:
Title
Agreement for Environmental Review for New Compost Facility at the Airport Closed Landfill
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Recommended Action:
Recommended action
A) Receive an update on the development of a proposed compost facility on existing County-owned property located at 5200 Slusser Road, Windsor.
B) Authorize the Chair to execute an agreement with RCH Group for preparation of CEQA and NEPA environmental review documents for the proposed compost facility at the closed Airport Closed Landfill and adjacent airport property, for a period of three years and two optional one-year extensions ending May 1, 2029, and a total amount not to exceed $1,180,00.00.
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Executive Summary:
Sonoma County Public Infrastructure (SPI), Integrated Waste Division, in collaboration with Zero Waste Sonoma, is seeking to establish an advanced composting facility utilizing a covered row system on County-owned land at the Airport Closed Landfill and adjacent airport property. The facility will process an estimated 70,000 tons of organic material annually and the design will prioritize reducing greenhouse gas emissions through solar and renewable integration, energy efficient equipment, and innovative waste management practices.
In December 2022, a feasibility study confirmed the suitability of the proposed site, and in January 2024, SCS Engineers was retained to develop 30% design plans, conduct technical studies, and engage in public outreach to support regulatory compliance. In December 2025, 30% design was completed and an RFP was released for an environmental consultant to prepare the CEQA and NEPA documents. Two proposals were received, and RCH Group was deemed the most qualified firm for the project after a comprehensive review process by SPI, and Permit Sonoma staff. Staff is recommending entering into an agreement with RCH Group with a contract amount of $1,180,000.00 to perform the proposed work for a term of three years with two optional one-year extensions, if requested by the County.
Construction and operational expenses are anticipated to be financed primarily through a public-private partnership in which a private entity would provide capital to design, construct, and operate the facility. Additional funding mechanisms may include grant funding, tip fees on committed and self-haul green waste, and funds from the rural landfill fund. No General Fund contribution is proposed for this project.
Discussion:
Since 2015, organic materials collected in Sonoma County, including weekly pick-up of residential curbside green bins and commercial food scraps, have been hauled to composting facilities located outside the county. The Integrated Waste Division of SPI, in collaboration with Zero Waste Sonoma, seeks to design and build a centralized composting facility in Sonoma County. The proposed site is situated primarily on top of a closed landfill on airport property at 5200 Slusser Road, Windsor, CA., which is adjacent to the Charles M. Schulz - Sonoma County Airport.
In December 2022, the engineering firm Brelje and Race completed a feasibility study which found the proposed site viable as a compost facility utilizing a covered row system with sufficient area to process 65,000 tons of compost per year. Based on the conclusions of the feasibility study, SCS Engineers completed 30% design for a composting facility on the closed landfill in December 2025 and CEQA technical studies are in progress. To minimize long-term operational costs and ensure the site is environmentally friendly, the facility design will incorporate sustainable design features and strategies, emphasize reducing greenhouse gas (GHG) emissions through the integration of solar and other renewable technologies, as well as utilizing energy-efficient equipment, implementing energy recovery systems, using green building materials, and optimizing waste management practices.
Concentrating on minimizing GHG emissions and incorporating sustainable design elements is intended to create a state-of-the-art composting facility that is both environmentally responsible, cost-effective and will aid in meeting State legislation SB 1383’s objective of diverting 75% of the organics from the landfill by 2025.
The establishment of a local compost facility offers direct and substantial benefits to the County of Sonoma and its municipalities. A centrally located compost facility within the County will lower GHG emissions by reducing transportation distances for the delivery of organic waste. This reduction in travel distance translates into cost savings for both the county and municipal green waste collection services. These savings arise from decreased fuel consumption and lower wear-and-tear on collection vehicles, thereby reducing operational costs and improving operational efficiencies by allowing for more frequent and potentially increased collection capacities. Additionally, the local availability of high-quality compost generated by this facility can support municipal and regional agricultural, landscaping, and public works projects, thus closing the loop in organic waste recycling within the County and contributing to a more sustainable local ecosystem.
Project Objectives:
1. Repurposing Land: Repurpose a closed landfill area for beneficial use while maintaining protective controls and compatibility with site constraints and future land use.
2. Material Management Expansion: Expand local organics processing capacity by developing a composting facility designed for approximately 70,000 tons/year (with permitting up to 75,000 tons/year to accommodate growth). Key parameters include:
• Maximizing renewable energy opportunities (e.g., solar)
• Engineering controls consistent with a zero-discharge stormwater approach
• Covered Aerated Static Pile (CASP) composting to reduce odor and emission potential compared to uncovered windows.
3. Centralized Facility: Provide a centrally located County facility to reduce out-of-county hauling of green waste. A local facility is expected to significantly reduce route miles (estimate up to approximately 350,000 miles/year avoided at full planned throughput), lowering cost and greenhouse-gas emissions.
4. Private Enterprise Partnership: Continue developing the project to support a long-term public-private partnership in which a private operator finances, constructs, and operates the facility, providing compost processing and product marketing under a long-term operating agreement structured to reduce upfront public capital costs, provide rate certainty, and align with County goals and ZWS program needs.
Project Status:
The project has reached 30% design, which is the level needed to begin formal CEQA analysis. Required CEQA technical studies and analysis are in progress.
On December 17, 2025, SPI issued a Request for Proposal (RFP) to solicit competitive proposals from qualified consulting firms to prepare the CEQA and NEPA documents once technical studies have been completed. Proposals were due February 4, 2026, and two were received from the following firms:
1. RCH Group
2. Hamer Environmental
In February 2026, proposals were reviewed and scored by partnered staff of SPI and Permit Sonoma, based on the following criteria:
• Project Understanding and Approach;
• Qualifications and Experience, understanding of CEQA, NEPA, Federal Aviation Administration’s policy and procedures for NEPA compliance and compost facilities;
• Costs relative to the scope of services;
• Quality of Work and References;
• Willingness to accept the County’s contract terms;
• Responsiveness and clarity of Written Proposal;
• Locality of the proposer.
RCH Group was selected and deemed to have a proposal responsive to the County’s needs due to the strength of their team and their experience with similar complex projects. The total proposed contract amount is for $1,180,00.00. Funding sources include use of fund balance from the Former Rural Landfill Fund and grant funds should they become available.
Initial public outreach is anticipated to begin May 2026 and will include two public meetings. A website and email address has been set up for the project and will be made available at the start of public outreach.
Tasks Completed to Date:
March 2022: Airport site visit conducted with SPI and regional partners.
March/April 2022: Area review, tonnage projection, and technical data analysis done in collaboration with ZWS and partners.
December 2022: Third-party feasibility study confirmed the site's capability to compost up to 65,000 tons/year of green waste.
August 3, 2023: RFP released for Engineering and Environmental Services to develop 30% plans.
January 23, 2024: Board item for awarding Engineering and Environmental Services for development of 30% plans.
2025: 30% design completed (sufficient level to initiate CEQA analysis), CEQA studies underway.
December 17, 2025: RFP released for Environmental Consultant to prepare CEQA/NEPA document(s).
Upcoming Tasks:
May/June 2026: Initial public outreach meetings
2026: (following consultant award) Prepare draft CEQA document(s) using completed technical studies and circulate for public review.
2027: Return to Board for final CEQA action and project approvals (as required). Once CEQA has been completed, the NEPA document will be prepared and submitted to the FAA for review.
Strategic Plan:
N/A
Prior Board Actions:
1/23/24: Award agreement for Engineering and Environmental Services for Development of 30% plans.
Fiscal Summary
|
Expenditures |
FY 25-26 Adopted |
FY 26-27 Projected |
FY 27-28 Projected |
|
Budgeted Expenses |
$200,000 |
$1,180,000 |
$180,000 |
|
Additional Appropriation Requested |
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|
|
Total Expenditures |
$200,000 |
$1,180,000 |
$180,000 |
|
Funding Sources |
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General Fund/WA GF |
|
|
|
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State/Federal |
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Fees/Other |
$200,000 |
$1,180,000 |
$180,000 |
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Use of Fund Balance |
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Contingencies |
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|
|
|
Total Sources |
$200,000 |
$1,180,000 |
$180,000 |
Narrative Explanation of Fiscal Impacts:
Appropriations for this agreement are available in the FY 2025-26 Integrated Waste Former Rural Landfill (41122-34050200) Adopted Budget, with unanticipated savings from perimeter fencing and road improvements not due to be completed within the fiscal year.
Appropriations for FY 2026-27 in the amount of $1,180,000 are included in Former Rural Landfill Recommended Budget, utilizing available 41122 Fund balance. The Fiscal Year 2026-27 ending Fund Balance for the 41122 Former Rural Landfill fund is projected to be $31,274.
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Staffing Impacts: |
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Position Title (Payroll Classification) |
Monthly Salary Range (A-I Step) |
Additions (Number) |
Deletions (Number) |
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Narrative Explanation of Staffing Impacts (If Required):
None
Attachments:
1 - Compost Facility Infographic
2 - Professional Service Agreement
Related Items “On File” with the Clerk of the Board:
None