To: BOARD OF SUPERVISORS
From: Supervisor Williams
Meeting Date: September 15, 2026
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Department Contact: |
Supervisor Williams |
Phone: |
707-937-3500 |
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Item Type: Regular Agenda |
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Time Allocated for Item: 45 Minutes |
Agenda Title:
title
Discussion and Possible Action Regarding Waterless Composting Toilet Options for Rural Mendocino County
(Sponsor: Supervisor Williams)
Vote Requirement: Majority
End
Recommended Action/Motion:
recommendation
Discuss and support Supervisor Williams in working with stakeholders, Santa Cruz County, and state representatives and regulatory agencies to explore a limited, voluntary rural container-based sanitation pilot, subject to full cost recovery; request limited consultation, within existing resources, from Public Health’s Environmental Health Division on discrete feasibility questions; and require any proposal to return to the Board before implementation or any substantial General Fund or departmental commitment.
End
Previous Board/Board Committee Actions:
In 1981, the Board adopted Ordinance No. 3343, establishing Mendocino County Code Chapter 18.23, Limited Density Rural Dwellings, commonly known as Class K. In 2021, Environmental Health, in coordination with Planning and Building Services, developed residential waterless-toilet standards in response to needs identified by the cannabis community. The materials reviewed do not identify a Board action adopting those standards, which treat waterless toilets as accessory to, rather than a replacement for, an approved onsite wastewater treatment system (OWTS), commonly called a septic system. On Sep 10, 2024, the Board adopted Ordinance No. 4538, including Chapter 20.170, Moveable Tiny Homes, as part of the Inland Zoning Code Update. In 2025, the Board adopted Resolution No. 25-093, approving the Mendocino County Drought Resilience Plan and authorizing its submission to the California Department of Water Resources. Together, these Board actions and staff work establish related rural construction, housing, drought-resilience, and sanitation policies, but do not authorize composting toilets as a replacement for an approved OWTS or otherwise alter applicable onsite wastewater requirements.
Summary of Request:
This item does not ask the County to establish or operate a pilot. It asks the Board to support Supervisor Williams in working with interested stakeholders, Santa Cruz County, state representatives, and regulatory agencies to determine whether a limited, voluntary pilot could be designed for rural Mendocino County, subject to full cost recovery. Public Health’s Environmental Health Division would be asked to answer only discrete questions and provide preliminary feasibility feedback within existing resources. Any proposal would return to the Board before implementation or any substantial General Fund or departmental commitment.
The case for exploring a pilot begins with rural housing. Many rural homes in Mendocino County rely on onsite wastewater treatment systems, and some undeveloped or underused residential parcels have difficult soil, slope, groundwater, reserve-area, or access conditions. Modern treatment requirements can make an approvable system prohibitively expensive or technically difficult. The County’s 2019 to 2027 Housing Element reports 2019 estimates of about $15,000 for a basic system and $40,000 for a larger system with secondary treatment, with some systems exceeding $50,000. Recent official California estimates are higher for constrained sites. San Luis Obispo County estimates $75,000 to $120,000 for advanced systems. A North Coast Regional Water Board staff report cites Sonoma County estimates ranging from $50,000 for a standard code-compliant system to $100,000 for a mound or drip system with treatment, plus $5,000 to $15,000 or more for design and permitting. Santa Cruz County’s pilot report describes a complex mountain property with three small rental units where septic estimates exceeded $160,000, including one estimate of $180,000. These are site-specific examples, not typical conventional-system costs, but they show how wastewater compliance can become a barrier to housing on difficult parcels.
Those costs matter in a county already struggling to add housing. A 2026 County Housing Element update presentation estimates that about 54 percent of Mendocino County households are in lower-income categories. The state’s final Regional Housing Need Determination assigns 6,456 units to the region, and MCOG’s adopted methodology produced a draft allocation of 3,780 units for unincorporated Mendocino County. Chapter 20.170 allows Moveable Tiny Homes but requires an Environmental Health-approved water and waste disposal system. A lawful waterless toilet could reduce wastewater volume and treatment demand attributable to toilets for some small homes, accessory dwelling units, moveable tiny homes, disaster-recovery sites, or existing dwellings. Any savings would still depend on site conditions, state law, and the approved system for kitchen, bathing, laundry, and other wastewater. Feasibility work would need to determine how many parcels or units might qualify; this item does not promise a housing outcome.
Water supply, coastal groundwater, and disaster resilience are also part of the case. The Board-adopted 2025 Drought Resilience Plan maps 6,654 domestic wells, or 84 percent of the County total, and 25 of 27 State Small Water Systems, or 93 percent, in areas with high physical or social vulnerability to drought and water shortage. It concludes that the County is highly likely to experience drought conditions similar to or more severe than those of the past 20 years, with dry years more likely to be followed by additional dry years. During the 2021 drought, the County sought a 20 percent reduction in water use and arranged emergency water hauling to the coast. Contemporary reporting described businesses closing public restrooms and relying on portable toilets. EPA estimates that toilets account for nearly 30 percent of average indoor household water use nationally. The North Coast Basin Plan identifies saltwater intrusion as a climate-related hazard and states that sea-level rise can raise coastal groundwater levels and threaten shoreline infrastructure. On vulnerable low-lying parcels, higher groundwater can reduce separation from wastewater dispersal fields and complicate onsite wastewater treatment. Waterless sanitation will not solve drought-related water scarcity or coastal groundwater problems, but a limited pilot could begin to evaluate potable-water savings, continued sanitation service during shortages and disasters, operating reliability, and public-health performance under Mendocino conditions.
Environmental Health has already done some of the groundwork. Its residential waterless-toilet standards contemplate construction permits and three-year operational permits; operation and maintenance manuals; system sizing and setbacks; NSF/ANSI Standard 41 certification for manufactured units unless otherwise approved; controls for leachate and disease vectors; title recordation; inspections; and owner-paid permit, inspection, recordation, and enforcement costs. After a minimum one-year treatment period under biologically active conditions, material must be tested by a certified laboratory before removal and may not exceed 75 percent moisture or 200 fecal coliforms per gram. The standards allow waterless toilets only in specified settings, treat them as accessory to an approved OWTS, and require all remaining wastewater to be discharged to an approved system. Environmental Health has advised that this approach reflects the applicable treatment of blackwater as including kitchen and toilet wastewater. The remaining question is whether toilet waste could be regulated separately while preserving approved treatment of all other wastewater.
Container-based sanitation still depends on a managed service chain: containment, collection, transport, treatment, and safe reuse or disposal. World Health Organization guidance identifies emptying, transport, off-site treatment, and handling of treated material as important exposure points. The guidance emphasizes worker training, protective equipment, safe handling, and treatment verification. A Mendocino proposal would also need clear spill-prevention and access-control procedures tailored to the equipment, operator, and site.
Santa Cruz offers a useful, but limited, California comparison. Like Mendocino, it has steep, forested, unsewered mountain communities. Interest in the pilot followed the CZU fire, costly septic reconstruction, watershed concerns, nonconforming rural housing, and the need for sanitation that can continue when wildfire, flood, power loss, or infrastructure failure interrupts normal service. This item does not propose adopting Santa Cruz’s program.
Santa Cruz authorized a limited container-based sanitation pilot capped at 25 eligible participants. It used bag-lined five-gallon containers, sawdust, sealed transport totes, household collection and, for several participants, transport to the compost site or a town handoff, all under project-specific operating and spill-response procedures, with centralized composting at the Watsonville wastewater treatment facility. The pilot processed more than 250 containers and 2,500 pounds of material. One finished-compost sample reported fecal coliform below 7.5 MPN per gram dry weight and Salmonella below 3 MPN per four grams dry weight. The final report states that these values met the cited CalRecycle pathogen-reduction criteria and EPA Class A biosolids standards. The results are encouraging, but the pilot’s limited duration and single reported finished-compost sample do not establish repeatability across batches or seasons. The report did not provide a comparison group, clearly state how many eligible households completed the pilot, test for a broader range of contaminants, or measure housing units enabled. The material was transferred for further commercial composting rather than documented unrestricted onsite reuse. The report documented technical feasibility in several areas but did not conclude that container-based sanitation could replace conventional wastewater systems.
Santa Cruz also showed that the toilet is only one part of the system. The pilot encountered insurance difficulties, an ill-fitting liquid septic-hauler permit, unbudgeted household collection, steep and gated access, privacy concerns, containers too heavy for some participants, and dependence on a willing receiving facility. A workable Mendocino proposal would need an identified operator and backup operator, depot, transporter, treatment site, chain of custody, insurance, spill and complaint response, a plan for failed batches, and closure funding before implementation.
Supervisor Williams has also seen professional waterless-sanitation systems in operation. At the urging of constituents of Supervisors Williams and Norvell, Supervisor Williams toured Finizio near Berlin and Kompotoi in the Zurich region. He also reviewed Composting Toilets Sanitation Without Water at the request of Wolfgang Berger, a mentor with decades of experience developing and implementing composting-toilet systems. Finizio combines urine-diverting dry toilets with professional collection and centralized processing, including high-temperature hygienization, managed composting, and quality assurance. Kompotoi provides mobile and permanent waterless toilets along with collection and processing services. Both demonstrate the importance of professional operation rather than unmonitored composting by individual property owners. Photographs from the visits will be presented to the Board. At Finizio, Supervisor Williams was introduced to DIN SPEC 91421:2020-12, a German quality-assurance specification for fertilizers and soil amendments made from dry-toilet contents. It provides a useful model for representative sampling and testing of pathogens, selected pharmaceutical residues, fluorinated compounds, metals, foreign material, nutrients, and agronomic quality. The specification addresses product quality and safety, not toilet design, collection, transport, treatment-process approval, or California authorization, and it does not establish limits for every possible contaminant. It could inform a Mendocino proposal, but regulator-approved methods and release criteria would control.
Any Mendocino pilot would need regulator-approved public-health monitoring procedures. The design should address repeated sampling; monitoring of time, temperature, moisture, aeration, pH, curing, vectors, and leachate; fecal-coliform and Salmonella testing; any viral or helminth validation required by regulators; and targeted testing for pharmaceuticals, PFAS, metals, and other contaminants selected with the state and an accredited laboratory. During the pilot, material should remain under controlled management and be sent for further treatment or disposal at an authorized facility, with no land application unless separately approved.
No single state provision answers whether Mendocino could authorize such a pilot. The 2025 California Plumbing Code provides several possible, but untested, pathways. Sections 301.5 and 301.7 allow case-specific alternative engineered designs and local-health-authority approval of substantially equivalent alternate facilities for one- and two-family dwellings. Section 303.1 separately allows an alternative to a water closet in limited-density owner-built rural dwellings when approved by the local health official and paired with approved graywater treatment or disposal. Appendix O is nonmandatory unless adopted and addresses prefabricated integrated systems certified to ANSI/CAN/IAPMO/ISO 30500, not the container service tested in Santa Cruz. These provisions do not by themselves resolve the full sanitation service chain. County Counsel and state regulators would need to determine whether a limited demonstration could proceed under existing authority and, if not, identify the narrowest necessary legislation or code changes. The questions include plumbing approval, treatment of remaining wastewater, hauler registration, transport and spill controls, compost-facility authorization, testing, end use, insurance, cost recovery, reporting, and a sunset.
The immediate work would remain with Supervisor Williams and outside participants, not a County department. An applicant, operator, nonprofit, academic partner, or outside consultant would develop the parameters and technical package needed to evaluate a Mendocino pilot. Environmental Health would answer discrete questions and provide preliminary feasibility feedback within existing resources, but would not be directed to design, administer, inspect, or operate a pilot, change existing permitting requirements, or commit substantial General Fund resources. Supervisor Williams would return to the Board with the proposed legal pathway, use cases, operator and receiving facility, public-health safeguards, funding, cost-recovery method, and next steps. Any pilot would require separate Board authorization.
Possible outside support includes USDA Rural Development predevelopment planning grants, EPA RealWaterTA, and State Water Board technical assistance. USDA grants are limited to qualifying low-income rural communities and cover no more than $60,000 or 75 percent of eligible planning costs, whichever is less. Assistance from EPA and the State Water Board depends on eligibility and program capacity. County review and oversight would need to be supported by grants, other non-General Fund sources, or an applicant or operator cost-recovery deposit.
References:
Mendocino County Class K Limited Density Rural Dwellings Ordinance
<https://mendocino.legistar.com/View.ashx?GUID=C305CAE0-8BBA-43F6-91CD-A5753AC0EA68&ID=10553530&M=F>
Mendocino County Code Section 16.08.015
<https://mendocinoco-ca.elaws.us/code/coor_title16_ch16.08_sec16.08.015>
Mendocino County Chapter 20.170 Moveable Tiny Homes
<https://www.mendocinocounty.gov/home/showpublisheddocument/67452/638642328326170000>
Mendocino County Drought Resilience Plan
<https://mendocino.legistar.com/View.ashx?GUID=7003AD70-9C44-453B-BB35-F551E76E5F16&ID=14215010&M=F>
Mendocino County Resolution No. 25-093
<https://www.mendocinocounty.gov/home/showpublisheddocument/71589/638834395565670000>
Mendocino County Housing Element
<https://www.mendocinocounty.gov/home/showpublisheddocument/44814/637636854812800000>
San Luis Obispo County Advanced Onsite Wastewater Treatment System Cost Comparison
<https://www.slocounty.ca.gov/departments/public-works/forms-documents/projects/cabrillo-estates-sewer-project/cabrillo-estates-wastewater-comparison>
North Coast Regional Water Board Russian River Pathogen TMDL Staff Report
<https://www.waterboards.ca.gov/northcoast/board_info/board_meetings/08_2025/pdf/6/6-rrtmdl-staffreport.pdf>
Santa Cruz Container-Based Sanitation Pilot Final Report
<https://santacruzcountyca.primegov.com/api/compilemeetingattachmenthistory/historyattachment/?historyId=63ad62b5-af4c-4570-8741-584bf60cdc98>
Mendocino County 2027 to 2035 Housing Element Update Presentation
<https://www.mendocinocounty.gov/home/showpublisheddocument/77530/639135708506900000>
Mendocino Council of Governments Resolution M2026-08
<https://www.mendocinocog.org/files/6188b9391/MCOG%2BResolution%2BM2026-08%2BAdoption%2BApproving%2BRHNA%2BMethodology.pdf>
California Fourth Climate Change Assessment North Coast Region Summary Report
<https://www.energy.ca.gov/sites/default/files/2019-11/Reg_Report-SUM-CCCA4-2018-001_NorthCoast_ADA.pdf>
North Coast Regional Water Quality Control Board Basin Plan, June 2025
<https://www.waterboards.ca.gov/northcoast/water_issues/programs/basin_plan/250703/06_25_BP.pdf>
Mendocino County Drought Conservation Notice
<https://www.mendocinocounty.gov/Home/Components/News/News/5499/626?arch=1>
Mendocino County Water Hauling Services Notice
<https://www.mendocinocounty.gov/Home/Components/News/News/5697/18?arch=1&npage=32>
Associated Press Dry California Tourist Town to Guests Please Conserve
<https://www.ksby.com/news/drought/dry-california-tourist-town-to-guests-please-conserve>
U.S. EPA WaterSense Labeled Toilets
<https://www.epa.gov/sites/default/files/2017-01/documents/ws-products-factsheet-toilets_0.pdf>
World Health Organization Guidelines for the Safe Use of Wastewater, Excreta and Greywater, Volume 4
<https://www.who.int/publications/i/item/9241546859>
Ryan A. Smith, Disasters, Finances, Nutrients, and Climate Change: A Case for Waterless Sanitation Systems
<https://hdl.handle.net/10945/66143>
Santa Cruz County Composting Toilet Pilot Program Announcement
<https://www.santacruzcountyca.gov/portals/0/county/BOS/district1/press-releases/PR_Establishing_6month_CBS_Pilot.06272023.pdf>
Santa Cruz County Expansion of Container-Based Sanitation Pilot
<https://www.santacruzcountyca.gov/portals/0/county/BOS/district1/press-releases/PR%20Establishing%206-month%20CBS%20Pilot_August%2013%2C%202024.pdf>
Santa Cruz County Staff Report Accepting the Pilot Final Report
<https://santacruzcountyca.primegov.com/api/compilemeetingattachmenthistory/historyattachment/?historyId=9882d53a-a2da-45fd-9c32-2e44db4fd35e>
Santa Cruz County Civil Grand Jury Consolidated Final Report
<https://www.santacruzcountyca.gov/Portals/0/County/GrandJury/GJ2024_final/2023-24_Consolidated_Final_Report_with_Responses.pdf>
Finizio Recycling and Treatment Model
<https://finizio.de/recycling/>
Kompotoi Composting Toilet Systems and Services
<https://www.kompotoi.ch/en/faq/>
Composting Toilets Sanitation Without Water
<https://www.susana.org/_resources/documents/default/2-1128-composting-toilets-index.pdf>
DIN SPEC 91421: Quality Assurance of Recycling Products from Dry Toilets for Use in Horticulture
<https://www.dinmedia.de/en/technical-rule/din-spec-91421/330937272>
2025 California Plumbing Code
<https://epubs.iapmo.org/2025/CPC/>
IAPMO Water Efficiency and Sanitation Standard
<https://iapmo.org/we-stand/document-information/>
California Health and Safety Code Section 117405
<https://leginfo.legislature.ca.gov/faces/codes_displaySection.xhtml?lawCode=HSC§ionNum=117405>.
California Health and Safety Code Section 25163
<https://leginfo.legislature.ca.gov/faces/codes_displaySection.xhtml?lawCode=HSC§ionNum=25163>.
CalRecycle Compostable Materials Regulations
<https://www2.calrecycle.ca.gov/Docs/Web/120138>
California State Water Resources Control Board Onsite Wastewater Treatment Systems Policy
<https://www.waterboards.ca.gov/water_issues/programs/owts/docs/adopted_owts_policy.pdf>
U.S. EPA Plain English Guide to the Part 503 Biosolids Rule
<https://www.epa.gov/sites/default/files/2018-12/documents/plain-english-guide-part503-biosolids-rule.pdf>
U.S. EPA Analytical Methods for Contaminants of Emerging Concern
<https://www.epa.gov/cwa-methods/cwa-analytical-methods-contaminants-emerging-concern>
U.S. EPA Method 1633A for PFAS
<https://www.epa.gov/cwa-methods/cwa-analytical-methods-and-polyfluorinated-alkyl-substances-pfas>
USDA Water and Waste Disposal Predevelopment Planning Grants
<https://www.rd.usda.gov/programs-services/water-environmental-programs/water-waste-disposal-predevelopment-planning-grants>
U.S. EPA RealWaterTA
<https://www.epa.gov/water-infrastructure/real-water-technical-assistance-realwaterta-information>
Alternative Action/Motion:
Provide alternate direction to staff.
Strategic Plan Priority Designation: A Safe and Healthy County
Supervisorial District: All
Supplemental Information Available Online At: N/A
Fiscal Details:
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source of funding: N/A |
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current f/y cost: No Additional Appropriation Requested |
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budget clarification: N/A |
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annual recurring cost: None Authorized |
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budgeted in current f/y (if no, please describe): Existing resources only, no pilot or new funding is authorized |
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revenue agreement: N/A |
AGREEMENT/RESOLUTION/ORDINANCE APPROVED BY COUNTY COUNSEL: N/A
CEO Liaison: Executive Office
CEO Review: Yes
CEO Comments:
FOR COB USE ONLY
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Executed By: Deputy Clerk |
Final Status: Item Status |
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Date: Date Executed |
Executed Item Type: item |
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Number: |
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