Dakota County was one of the first to join the Minnesota Department of Agriculture’s Targeted Townships project to test private wells considered to be at risk of high levels of nitrate.
The Minnesota Department of Agriculture is in the process of updating its plan to reduce groundwater contamination. One feature of the new plan is to identify geographic areas, based on township boundaries, where more than 5 percent of the private drinking water wells exceed the drinking water standard for nitrate.
Dakota County offers free well water testing
In 2013, the County conducted a pilot project to evaluate the effectiveness of collecting nitrate samples from private well owners by mail from the cities of Coates, Hampton, and Hastings and the townships of Castle Rock, Douglas, Hampton, Marshan, Nininger, Randolph, Sciota, Vermillion, and Waterford. These areas were based on their soils and geology and the percentage of land used in agriculture.
The County worked with a private lab that handled test kit mailing and sample analysis. Test kits and sample analysis were free to well owners. More than 2,800 kits were mailed to the targeted communities, and 300 additional kits were sent to interested parties outside the targeted areas. From the targeted area, 667 households returned water samples to the lab for analysis. The lab sent participants their individual results after the sample was received.
The project was funded by a $65,000 grant from the Clean Water, Land & Legacy Amendment.
Contamination worse than expected
The results of the 2013 study were worse than expected. In the study area, 32 percent of the private wells tested exceeded the drinking water standard of 10 milligrams per liter (10 parts per million). See the Targeted Townships Final Aggregated Map.
Each community exceeded the Minnesota Department of Agriculture threshold of 5 percent of private drinking water wells exceeding the health standard. See the Targeted Townships Results Map.
|Castle Rock Twp.
|City of Coates
|Hampton Twp. and City
|City of Hastings
|Total for Study Area
|Outside Study Area
* Greater than 10 mg per liter.
Age of well plays a factor
Wells with high nitrate levels tend to be older and shallower. Seventy percent of wells that predate the State Well Code (1974) had nitrate levels higher than 10 mg/L (the drinking water standard).
In the 2013 study area, 38 percent of the households are estimated to have wells that predate the State Well Code (1974); 25 percent are estimated to have been installed between 1974 and 1988, and 37 percent are
estimated to have been installed after the County began to directly regulate private well construction.
Age of Wells in Study Area
Age of Wells with High Nitrate