USGS Releases Findings on Elevated Contaminants in Groundwater Determined in the Midwest

The U.S. Geological Survey (USGS) has released a report entitled, “Areas of Elevated Contaminants in Groundwater Determined from Regional Assessment in the Midwest.” The study was conducted as part of an ongoing systematic assessment of some of the Nation’s most important aquifer systems by the USGS National Water-Quality Assessment (NAWQA) Program. This regional assessment of the Cambrian-Ordovician aquifer system is ranked ninth in the nation for public supply water withdrawals from principal aquifers. The aquifer supplies water to many parts of the northern Midwest, including areas of Minnesota, Wisconsin, Illinois, Iowa, Missouri, and the Upper Peninsula of Michigan, as well as the major cities of Minneapolis, Rockford and Chicago.

The report shows at least one contaminant at levels of human-health concern in about one third of untreated groundwater samples collected from wells in the Cambrian-Ordovician aquifer system. When radon concentrations greater than 300 picocuries per liter are included, 64 percent of wells sampled contain a contaminant concentration above a human-health benchmark.

Many of the public and private wells sampled contain natural or manmade contaminants, including; radium, radon, boron, strontium, manganese, barium, nitrate, pesticides, and volatile organic compounds. The levels of radium and strontium from the Cambrian-Ordovician aquifer system are higher and more frequently exceed the human-health benchmark than in any of the other 30 principal aquifers studied by NAWQA. Many of the other principal aquifers studied by NAWQA have arsenic levels that frequently exceed the human-health benchmark in domestic and public-supply wells, though arsenic did not exceed the benchmark in any samples from the Cambrian-Ordovician aquifer system.

To view the report online, visit the USGS web site at: