Cottage Grove and Denmark Township private wells will undergo nitrate testing to determine whether the water is safe enough to drink.
Over 1,400 households will receive test kits in the next few months as part of a partnership between Washington County and the Minnesota Department of Agriculture.
The two communities have pockets of elevated nitrate levels due to sensitive geology and traditional agriculture fertilizer runoff.
Failing septic systems can also cause nitrate contamination, which is a public health concern, said Washington County planner Stephanie Souter.
“Levels above 10 milligram per liter are dangerous to populations like infants under 6 months of age, pregnant women and those with certain blood disorders,” she said.
According to the Agriculture Department, elevated levels of nitrate testing in drinking water can cause long term health effects to older children and healthy adults as well.
The National Cancer Institute suggests a link between nitrate and increased risk of non-Hodgkin’s lymphoma.
Nitrate is naturally occurring and it also comes from manmade sources such as fertilizer as well as animal and human waste, Agriculture Department hydrologist Kimberly Kaiser said.
The 10 milligrams per liter threshold is associated with blue baby syndrome, which causes decreased oxygen carrying capacity of hemoglobin in babies, potentially leading to death.
“Those are the concentrations we’re very concerned about,” Kaiser said. “Anything from 0 to 3 is usually considered a background concentration.”
Some private well owners have in the past used walk-in test clinics that were set up all across the state, including in Lake Elmo and Afton.
In 2011, over 2,000 samples were analyzed during nitrate testing clinics from 41 counties across the state, according to the Agriculture Department. Counties with the greatest levels of concern were in the southwestern part of the state; Rock, Nobles and Pipestone had the top three highest results for private wells greater than 10 milligrams per liter.
In Washington County, 141 samples were tested with 3.5 percent showing nitrate levels over 10 milligrams per liter.
“A lot of times when you do clinics like that people that think their water might be high (in nitrate) come in,” Kaiser said. “It’s not a very good scientific sample.”
More targeted testing is being done in areas most vulnerable to groundwater contamination like in south Washington County, to gather firm scientific data.
“Water travels quickly from the land surface to the aquifer where people are getting their drinking water,” Kaiser said of areas in Cottage Grove and Denmark Township. “The combination of the percentage of crop production and aquifer vulnerability make those areas more sensitive to nitrate contamination.”
Homeowners who receive kits are encouraged to fill out the questionnaire about the nature of their groundwater and septic systems and return it with the water sample.
The results will be mailed within a couple of weeks. If nitrate is found, private well owners must find a different source for drinking water.
If the sample comes back within the 0 to 3 milligrams per liter range, homeowners are advised to continue monitoring their water.
“When you have a private well, you’re not regulated,” Kaiser said, “but you should still test your water to make sure it’s safe because water conditions can change.”