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Potential for Siting New Water Wells and Restoring Existing Wells in Arsenic-Impacted Aquifers
Citation:
PULS, R. Potential for Siting New Water Wells and Restoring Existing Wells in Arsenic-Impacted Aquifers. Presented at Fifth Annual EPA Drinking Water Workshop on Treatment and Distribution System Compliance Challenges, Cincinnati, OH, August 05 - 07, 2008.
Impact/Purpose:
Conducting studies to determine if arsenic concentrations greater than the new U.S. Environmental Protection Agency (EPA) maximum contaminant level (MCL) concentration of 10 micrograms per liter (ug/L) occur in numerous aquifers around the United States
Description:
Studies have indicated that arsenic concentrations greater than the new U.S. Environmental Protection Agency (EPA) maximum contaminant level (MCL) concentration of 10 micrograms per liter (ug/L) occur in numerous aquifers around the United States. One such aquifer is the Central Oklahoma aquifer, which supplies drinking water to numerous communities in central Oklahoma. Concentrations as high as 230 ug/L have been reported in some drinking water supply wells from this aquifer. The City of Norman, like most other affected cities, is actively seeking a cost-effective solution to the arsenic problem. Only six of the city’s 32 wells exceeded the old MCL of 50 micrograms per liter. When the new MCL became effective (2006), 18 of the 32 wells exceeded the allowable concentration of arsenic. Arsenic-bearing shaly sandstones appear to be the source of the arsenic. It may be possible to isolate these arsenic-bearing zones from water supply wells, enabling production of water that complies with drinking water standards. It is hypothesized that geologic mapping together with detailed hydrogeochemical investigations will yield correlations which predict high arsenic occurrence for the siting of new drinking water production wells. More data and methods to assess the specific distribution of arsenic in aquifers are needed to improve our predictions for arsenic occurrence in water supply aquifers. Research is also needed to assess whether we can retrofit existing water supply wells to isolate arsenic-bearing strata in these aquifers. This is a collaborative effort between EPA-ORD, the city of Norman, Oklahoma State University, and the U.S. Geological Survey.