Trends in Arsenic Concentrations in the San Joaquin Valley

Arsenic is known to be a problem in groundwater used for drinking water supplies in the San Joaquin Valley. About 10% of the are of groundwater resources used for public supply contain more than the USEPA MCL of 10 µg/L. Most public-supply and domestic wells currently yield groundwater with arsenic levels below 3 µg/L and do not exhibit trends in concentration.