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Arsenic in Minnesota groundwater and its impact on the drinking water supply

PIs: Randal Barnes, Professor, Department of Civil Engineering

Collaborator: Mindy Erickson, Research Assistant, Water Resources Science Program

Funding Source: USGS-WRRI 104B/ CAIWQ Competitive Grants Program

Project Duration: 3/1/03- 2/28/04

In 2001 the United States' federal drinking water standard, or Maximum Contaminant Level (MCL), was decreased from 50 mg/L to 10 mg/L. Public water supplies have until January 1, 2006 to comply with the new standard. Nationwide, the change in the MCL will have significant economic impact on public water supplies that exceed the new MCL. In Minnesota alone, 67 (12%) of Minnesota's public water supplies have arsenic in excess of 10 mg/L. A recent western-Minnesota study found that over 50% of the 900 sampled private drinking water wells had arsenic over 10 mg/L. Statewide, almost 15% of wells sampled exceed 10 mg/L arsenic.

The proposed research project's key components involve creating a useful database from existing data; field work, including groundwater and solids sampling; laboratory analyses of groundwater and solids samples; and data analysis/model building to provide the following information:

  • Characterization of the sampling and temporal variability of arsenic concentration in wells.
  • Determination of how many samples are enough to be confident that the arsenic concentration is actually below the MCL.
  • Determination of the relationship between arsenic concentration in geologic material and arsenic concentrations in water.
  • Determination of likely mechanisms.
  • Characterization of the changes in arsenic concentration in new wells. Specifically, determining how the well's presence changes the arsenic concentration in the water.