Well Water in San Benito County: What to Test and Why

Groundwater in San Benito County contains arsenic, chloride, iron, manganese, nitrate, radon, sulfate, uranium, and PFOA and PFOS compounds. Multiple contaminants exceed EPA health standards, making this a high-concern area where well owners need to test their water regularly.

The Central Valley aquifer system here sits in an area shaped by agriculture, urban development, and natural mineral deposits. Nitrate enters from fertilizer and septic systems on the land surface. Arsenic, uranium, and other metals leach naturally from rock and soil layers underground. Radon seeps up from radioactive elements in the deep rock. High chloride and sulfate reflect both old seawater trapped in deep layers and salt from agricultural irrigation runoff.

Groundwater in this county is moderately hard and carries elevated sodium, sulfate, and dissolved minerals that make the total dissolved solids very high. These minerals come from the natural rock composition of the Central Valley and from decades of agricultural activity that concentrates salts in the soil and groundwater. Wells across the county show these characteristics as a widespread pattern, though individual well results vary based on depth and location.

Wells in San Benito County show elevated levels of arsenic, uranium, radon, nitrate, and PFOA and PFOS chemicals. Arsenic and uranium are radioactive metals that can damage kidneys and increase cancer risk with long-term exposure. Radon is a radioactive gas that raises lung cancer risk. Nitrate harms infants and can affect thyroid function. PFOA and PFOS are industrial chemicals that can weaken the immune system and affect liver health.

Your well water in this county may have minerals that affect how your water looks, tastes, and feels. Moderate hardness can leave scale buildup on faucets and inside pipes and appliances. Hard water can shorten the life of water heaters and dishwashers. Iron in the water can stain laundry and fixtures orange or brown, though levels here are generally low.

We recommend testing your well water right away since every well is different and yours could have higher or lower levels than other wells in the county. Testing is the only way to know what is actually in your water so you can treat it properly. A comprehensive panel that checks for metals, minerals, and chemicals typically costs two hundred to four hundred dollars. Water softeners and specialized filters can address multiple concerns once you know what you are treating.