Amador County – Amador County may be the source for high concentrations of arsenic found in nine percent of northern San Joaquin County’s groundwater.

A newly released, five year study from the U.S. Geological Survey (USGS) reveals high areas of arsenic concentration appear to be in the areas surrounding Stockton and south of Stockton near the eastern edge of the Delta.

Wells in Lodi did not have high arsenic concentrations.

The study’s authors say most of the arsenic arrived in the area as runoff from the Sierra Nevadas. Samples for the survey were taken from 61 wells in areas of Amador, Alameda, Calaveras, Contra Costa, San Joaquin and Stanislaus counties.

The USGS analysis focused solely on untreated groundwater from wells. More than 40 percent of the state’s drinking water comes from groundwater.

The report is designed as an informational tool to increase awareness of the issue for regional resource managers and water agencies. It is the most recent indication that higher than average levels of arsenic are prevalent throughout this region.

The Sierra Fund conducted soil tests on a number of public trails near mine shafts in the foothills earlier this year and discovered some cases of extremely high levels of arsenic, lead and asbestos. Researchers said these levels are a result of the extensive mining conducted in our area since the Gold Rush era, when miners dug deep into the earth to expose pockets of toxic contamination.

Speaking with SFGate.com in June, Elizabeth Martin, Sierra Fund chief executive, called these findings “the longest neglected environmental problem in California.”

Arsenic occurs naturally in many minerals and is mainly associated with sulfur and metals. It is considered extremely poisonous. People exposed to arsenic in their drinking water may be at increased risk for more serious illness or death.

Story by Alex Lane This email address is being protected from spambots. You need JavaScript enabled to view it.