A RAPID, HIGH DENSITY APPROACH FOR THE ASSESSMENT OF NITRATE IN MINNESOTA PRIVATE WELLS

Minnesota recently went through a lengthy revision process of the Nitrogen Fertilizer Management Plan which is the state’s response strategy for responding to nitrates in groundwater resulting from agricultural inputs. Approximately twenty community water suppliers are dealing with moderate to extreme nitrate issues. Statewide it is estimated that 6% of private wells exceed the 10 mg/L Nitrate-N drinking water standard. However past unscientific assessments, such as walk-in style clinics, suggest that some agricultural counties may have 10-20% of the wells above the standard. The Nitrogen Fertilizer Management Plan review process made it evident that Minnesota needed much better tools to assess current nitrate conditions for private households on a local scale.

In 2013, the Minnesota Department of Agriculture launched a pilot project in six agricultural townships that are considered hydrogeologically vulnerable. This strategy involved homeowners sampling their own well and sending samples to a certified lab with accompanying well information. Nitrate-N results showed that 75% of wells were less than 3 mg/L, 14% ranged from 3-10 mg/L and 11% of were greater than 10 mg/L. Well type was mostly of drilled construction (80%) with sand point wells and hand dug wells making up the remaining 20%. Another aspect of the pilot was to determine which of the problematic wells were capable of providing ambient groundwater conditions.

This novel approach is built upon the homeowner participation in partnership with local and state government. This presentation will walk the audience through the entire process and will share the findings and associated costs from the pilot. This pilot has paved the way for a statewide program to assess nitrates in private wells on a much larger scale. In the next six years, it is estimated that roughly 250 townships, which contain over 70,000 households, will have the opportunity to participate. These results will be extremely valuable for benchmarking current nitrate conditions and will guide the Nitrogen Fertilizer Management Plan process.