Flow Contribution and Water Quality with Depth in a Test Hole and Public-Supply Wells: Implications for Arsenic Remediation through Well Modification, Norma, Oklahoma, 2003-2006

摘要

The City of Norman, Oklahoma, is one municipality affected by a change in the Environmental Protection Agencys National Primary Drinking Water Regulation for arsenic. In 2006, the maximum contaminant level for arsenic in drinking-water was lowered from 50 to 10 micrograms per liter. Arsenic concentrations in water produced by 32 Norman public-supply wells ranged from less than 1 to 232 micrograms per liter. Some Norman wells with arsenic concentrations marginally exceeding 10 micrograms per liter are suspected of producing water from zones with acceptably low arsenic concentrations and zones with unacceptably high arsenic concentrations. If water with high arsenic concentrations can be limited or excluded from production without causing an excessive decrease in well yield, these wells may be rehabilitated to comply with the new regulation. The flow contribution and water quality of each producing zone was measured in 11 City of Norman wells to determine which wells were potential candidates for arsenic remediation by well rehabilitation. Depth-dependent flow-contribution and water-quality data were collected under normal production conditions using the U.S. Geological Survey combined well-bore flow and depth-dependent water sampler (U.S. Geological Survey well profiler). The depth-dependent water-quality data collected by the U.S. Geological Survey well profiler were extremely useful as a qualitative tool for identification of zones that degrade water quality in the Norman wells. The depth-dependent water-quality data, even without flow-contribution data, showed the depth at which the water mixture in the well bore was unsuitable for public supply.