San Benito County, California: drinking water report. San Benito County in central California has about 64,000 residents, with Hollister as the county seat.
San Benito County in central California has about 64,000 residents, with Hollister as the county seat. The county relies heavily on groundwater from the Hollister and San Juan Bautista basins, supplemented by imported water from the San Felipe Division of the Central Valley Project. Agriculture – primarily wine grapes, cattle, and vegetables – drives the local economy and water demand.
Naturally occurring nitrate and chromium-6 are the primary groundwater quality concerns in San Benito County. According to the California State Water Board's 2024 drinking water data, four community water systems in the county have reported chromium-6 detections above the state notification level. While California's chromium-6 MCL was invalidated by court order in 2017, the state is developing a new standard, and the compound remains in the water regardless of regulatory status.
The former San Benito County Airport used AFFF in small quantities. A 2024 Regional Water Quality Control Board investigation found low-level PFAS in two monitoring wells near the site. Agricultural nitrate from fertilizer application and livestock waste adds to the groundwater contamination picture, particularly in the southern portion of the Hollister basin.
San Benito County's groundwater challenges are primarily naturally occurring and agricultural in origin. Chromium-6, unlike many contaminants, is not removed by standard carbon filters – it requires specific treatment technology.
Check your water for current results at your address. For chromium-6 and nitrate, reverse osmosis is effective against both. Our water filter guide identifies which systems handle naturally occurring metals. Pull your detailed report for local data, and visit our California page for statewide context.