Nitrate was detected at high concentrations in 10 percent of the aquifer system used for public water supply in coastal areas of Santa Barbara and San Luis Obispo counties, according to a new U.S. Geological Survey report.
Trace elements, such as naturally occurring arsenic and molybdenum, were found at high concentrations in 27 percent of the aquifer system. In comparison, elsewhere in California high concentrations of nitrate have generally been found in less than 1 percent to 8 percent of the groundwater used for public supply, and trace elements in 6 percent to 28 percent.
As part of a statewide study assessing groundwater quality, scientists analyzed untreated groundwater from wells — not treated tap water. Groundwater is typically treated by water distributors prior to delivering it to customers to ensure compliance with water quality standards.