Well Water in Stanislaus County: What to Test and Why

Groundwater in Stanislaus County contains arsenic, chloride, nitrate, uranium, radon, and several other contaminants at levels that exceed EPA health standards. These are serious concerns that well owners should have their water tested for and address where standards are exceeded.

These contaminants come from a mix of sources. Arsenic and uranium occur naturally in the rock layers that make up the Central Valley aquifer system. Nitrate and chloride enter groundwater from agricultural activities and urban runoff across the valley's heavily farmed landscape. Radon seeps in from radioactive minerals in the surrounding rock. Some contaminants like trichloropropane come from old industrial or pesticide use.

Groundwater in this county is very hard, driven by elevated calcium and magnesium that dissolve from the rock as water moves through the aquifer. The high sodium levels reflect both natural salt deposits in the aquifer and salt that has moved in from irrigation and agricultural practices over decades. These mineral characteristics are widespread across wells throughout the county.

Wells in Stanislaus County can contain several contaminants that exceed EPA health standards, including arsenic, lead, uranium, radon, nitrate, and a group of chemicals called PFOA and PFOS. Arsenic and uranium are radioactive elements that build up in your body over time and increase cancer risk. Lead damages the brain and nervous system, especially in children, and can cause learning problems and behavioral issues. Radon is a radioactive gas that increases lung cancer risk when breathed in for years. Nitrate is especially dangerous for babies and can prevent their blood from carrying oxygen properly. PFOA and PFOS are long-lasting chemicals that can affect your liver, immune system, and cholesterol levels with long-term exposure.

The county's water is also very hard and contains high sodium levels. Hard water leaves white scale on faucets, pipes, and shower heads, and makes soap less effective for cleaning. It can shorten the life of water heaters and dishwashers by years. High sodium can make your water taste salty and is a concern for people on restricted diets.

We recommend testing your well water with a comprehensive panel since multiple contaminants exceed health standards in county wells. Every well is different, and yours could have higher or lower levels than what is common here. Testing is the only way to know what is actually in your water so you can treat it correctly. A comprehensive metals and minerals panel typically costs between two hundred and four hundred dollars. Treatment options like activated carbon filters, water softeners, or reverse osmosis systems can address different contaminants depending on what your test shows.