More than half of tested farmworker water systems showed bacterial contamination and San Mateo County is changing the rules
San Mateo County, California – For years, some of the smallest drinking water systems serving farmworker families in San Mateo County operated without routine government inspections. That is about to change, following the discovery of bacterial contamination in more than half of the systems tested during a county investigation.
The findings were difficult to ignore. Of 38 water systems examined, 21 tested positive for coliform bacteria, E. coli, or both. Although corrective work eventually brought those systems into compliance, county officials concluded that fixing problems after they appear was not enough to protect families who depend on the water every day.
On October 20, the San Mateo County Board of Supervisors approved a Farm Labor Housing Water System Inspection Program, establishing regular testing and inspections for smaller systems that previously received limited oversight. The new rules take effect November 19, 2026, as part of revisions to the County’s Domestic Water Systems Ordinance.
The program will initially cover 32 water systems serving 49 farmworker housing units in unincorporated areas of the county.
Previously, water systems serving farmworker housing with four or fewer connections generally escaped routine regulatory monitoring. Authorities typically intervened only when a reported problem presented an immediate health threat.
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Under the new requirements, operators must test their water for coliform and E. coli bacteria every three months. Systems must also meet standards for water pressure, quantity and quality, undergo county inspections, and address dangerous conditions affecting residents.
The policy grew out of a broader investigation following the January 23, 2023, shootings at two Coastside farms, where seven farmworkers were killed and another critically injured. The tragedy drew attention to unsafe conditions in employer-provided housing.
County officials subsequently established the Farmworker Housing Compliance Task Force, which inspected agricultural housing and identified drinking water contamination as a major concern.
Its February 2025 report recommended permits and ongoing testing for small water systems rather than relying on occasional inspections.
“After the tragedy in January 2023, we made a promise that every farmworker on the Coastside would live in a safe and healthy home. The Task Force showed us that unsafe drinking water was the most common problem these families faced,” said Supervisor Ray Mueller.
The County is also attempting to limit the financial burden on agricultural operators, including small family farms.
Annual permits will cost $1,706 per system, but applications submitted by June 30, 2027, will qualify for a full county subsidy. The subsidy will decline to 50 percent in fiscal years 2027–28 and 2028–29, then 25 percent in 2029–30. Operators will pay the full amount beginning in 2030–31.
Environmental Health Services developed the requirements with input from farmers, ranchers and local community organizations.
“Safe drinking water depends on regular testing and on owners who know exactly what is expected of them,” said Charles Ice, the department’s director.
Beyond farmworker housing, the ordinance updates rules for small domestic water systems serving up to 14 connections, clarifies landlord obligations and establishes water quality requirements for food facilities using small systems.
County officials will continue investigating complaints involving similar systems serving other multifamily housing, depending on available resources.
Residents and property owners can find additional information through San Mateo County Environmental Health Services or call 650-372-6200.
