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Accept the 2026 Annual Biosolids Land Application Report and Biosolids Research Project results from the Department of Resource Management
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Published Notice Required? Yes ___ No _X _
Public Hearing Required? Yes ___ No _X _
DEPARTMENTAL RECOMMENDATION:
The Department of Resource Management recommends that the Board of Supervisors accept the 2026 Annual Biosolids Land Application Report and Biosolids Research Project results.
SUMMARY:
Solano County Code, Chapter 25, requires that a report be submitted annually to the Board of Supervisors presenting the results of the past season’s activities on the land application of Class B biosolids in Solano County. The report documenting the results of the 2025 season for the land application of biosolids in Solano County is provided as the 2026 Annual Biosolids Land Application Report (Attachment A). The annual report must also include an update on the generator's progress toward utilizing alternative technologies for the reuse of biosolids other than land application or landfilling. That update is provided in the 2025 Bay Area Clean Water Agencies (BACWA) annual summary memorandum (Attachment B). The 2026 annual report also includes the results of the Solano County-funded Biosolids Research Project, which studied the fate of per- and polyfluoroalkyl substances (PFAS) in biosolids after land application.
FINANCIAL IMPACT:
The cost of managing and overseeing the biosolids land application program is typically recovered through fees collected for site registration and land spreading charged to the applicant. Costs for biosolids material sampling and sample analysis are also charged to the applicant. A per-acre surcharge for research, charged to the applicant, is used for conducting research activity to improve our understanding of potential impacts, if any, of the land application of biosolids. Class B biosolids land application has not occurred in Solano County since 2023.
The costs associated with preparing this agenda item are nominal and absorbed by the Department’s FY2025/26 Working Budget.
DISCUSSION:
Solano County is one of the few California counties that regulates the land application of biosolids onto agricultural land as a soil amendment. Since the mid-1990s, Department of Resource Management (DRM) staff have implemented the County’s biosolids land application oversight program through enforcement of Solano County Code Chapter 25, which incorporates the requirements contained in Title 40, Code of Federal Regulations, Part 503. Chapter 25 was amended between 1998 and 2012 to incorporate additional requirements including public notification for land application activities, wet weather restrictions on biosolids land application, prohibition of biosolids application within primary and secondary marsh areas, and expanded soil and groundwater testing requirements. These amendments have provided additional public health and environmental protections regarding the use of biosolids. The County’s biosolids program has been recognized nationally for its emphasis on public participation, research partnerships and proactive enforcement standards.
The reduction of land application activities is primarily attributed to the acquisition by Flannery Associates LLC (California Forever) of properties historically utilized for biosolids land application and the subsequent discontinuation of land application activities on those properties. Although no Class B biosolids land application occurred during 2025, the County's biosolids oversight program remains in effect and staff continue to monitor biosolids-related activities, emerging regulatory developments, and alternative biosolids management technologies.
One odor complaint associated with Class A biosolids-derived fertilizer application activities conducted by Lystek International was received in February 2025 in the eastern unincorporated Vacaville area. DRM staff continue to evaluate potential mitigation and oversight measures related to the land application of LysteGro fertilizer products to reduce the potential for future odor nuisance concerns. Staff are also evaluating potential amendments to Chapter 25 and/or other operational standards applicable to biosolids-derived injectable fertilizer products.
The annual report also includes the results of the Solano County-funded Biosolids Research Project, which studied the fate of PFAS in biosolids following land application. A separate report of these findings is provided as Attachment C. Funding for the research project was provided through the Board-established Biosolids Education and Research Trust Fund, supported through a $15 per applied acre fee charged to biosolids land application permit holders. The research project, conducted by Trihydro Corporation, evaluated the occurrence and behavior of PFAS compounds within historically biosolids-applied fields near the intersection of State Highways 12 and 113. The project was intended to evaluate the presence of residual PFAS compounds in soils previously receiving biosolids applications and identify trends among detected PFAS compounds. The research project provided baseline information regarding the occurrence and behavior of PFAS compounds in historically biosolids-applied soils. The study identified PFAS compounds in both historically biosolids-applied soils and the non-applied control area, reflecting the widespread occurrence of PFAS compounds in the environment. Some PFAS compounds were detected at concentrations exceeding available environmental screening levels; however, these screening levels are intended as risk-screening tools and are not regulatory standards or determinations of human health risk.
The report also references the 2025 BACWA annual memorandum, which provides an update on member agencies’ progress toward alternative technologies for biosolids reuse beyond land application or landfilling, as well as a summary of the Biosolids Stakeholder Group meeting held on February 26, 2026. Although no Class B biosolids were land applied in 2025, BACWA provided its annual memorandum to continue informing the County regarding regional biosolids management trends, emerging technologies, and alternative reuse strategies.
ALTERNATIVES:
The Board of Supervisors may choose not to accept the 2026 Biosolids Land Application Report and Biosolids Research Project results. This alternative is not recommended because the report is required pursuant to Solano County Code Chapter 25 and documents the Department's biosolids oversight activities during 2025.
OTHER AGENCY INVOLVEMENT:
In obtaining information for this report, the Department consulted with County Counsel, County Administrator’s Office, Agricultural Commissioner’s Office, University of California Cooperative Extension, US Environmental Protection Agency, the San Francisco Bay Area and Central Valley Regional Water Quality Control Boards, Synagro LLC, Lystek International Inc., and the Biosolids Stakeholder Group including representatives from interested constituents from the Rio Vista-Suisun areas of Solano County, East Bay Municipal Utilities District, Fairfield-Suisun Sewer District, Union Sanitary District and the City and County of San Francisco Public Utilities Commission. Information contained in the 2026 Annual Biosolids Land Application Report is distributed to participants in the Biosolids Stakeholder Group.
CAO RECOMMENDATION:
APPROVE DEPARTMENTAL RECOMMENDATION