Groundwater resource faces challenges
By Janet Kubat Willette
Date Modified: 10/25/2013 12:59 PM
ST. PAUL — Nitrate and chloride concentrations are the greatest challenges facing Minnesota's groundwater.
In central Minnesota, about 40 percent of the shallow sand and gravel aquifer wells contain water with nitrate concentrations that exceed the maximum contaminant level of 10 milligrams per liter set by the U.S. Environmental Protection Agency. In southwestern Minnesota, 20 percent of the shallow sand and gravel aquifer wells exceed the standard. There also are wells in the uppermost bedrock aquifers of southeast Minnesota that exceed the drinking water standard.
Chloride concentrations as high as 8,900 milligrams per liter were measured in shallow groundwater in the Twin Cities metropolitan area, and 27 percent of the monitoring wells in the sand and gravel aquifers had chloride concentrations that were greater than the EPA-established secondary maximum contaminant level of 250 milligrams per liter, according to the Minnesota Pollution Control Agency's 2013 Groundwater Condition Report.
The report was released in August and testimony was given on it Oct. 7 before the House Environment, Natural Resources and Agriculture Finance Committee.
The report, "The Condition of Minnesota's Groundwater," builds on the last report that was released in 2007, said MPCA research scientist Sharon Kroening, who provided a summary for the committee.
The assessments in the most recent report are based on data collected from 2007-11 by the Minnesota Pollution Control Agency, Minnesota Department of Agriculture and the volunteer nitrate monitoring network in southeastern Minnesota.
Researchers assessed nitrate, phosphorus, sulfate, chloride, arsenic, iron, manganese, 68 volatile organic compounds and more than 100 contaminants of emerging concern, Kroening said.
"Contaminants of emerging concern were detected in about one-third of the sampled wells," the report says. "No concentrations exceeded any applicable human-health guidance set by the state of Minnesota."
However, the report says, "The presence of contaminants of emerging concern in the groundwater, even though these are low in concentration, bears watching because this monitoring identifies chemicals in Minnesota's groundwater that have no health-based drinking water standard."
The latest data analysis -- from 90 wells -- found that the amount of nitrate contamination in the state's groundwater has not changed over the past 15 years. By contrast, chloride concentrations have increased by about 100 milligrams per liter in the last 15 to 20 years in some wells in the Twin Cities Metropolitan Area. The source of the chloride is likely winter de-icing chemicals.
Rep. Karen Clark, DFL-Minneapolis, asked if the MPCA is monitoring groundwater for chemicals used in fracking.
To date, the department hasn't, Kroening said.
The department does continue to monitor groundwater and additional wells are being installed, she said.
To view the report, go to pca.state.mn.us/0agx947