County land and water staff report rising nitrate trends in groundwater; recommend voluntary BMPs

County Land and Water Administrator Tim Steber presented results from the Citizens Groundwater Monitoring Program, a near-decade project that samples about 160 randomly selected wells annually to assess nitrate concentrations and trends.

Steber said the county's long-term testing found roughly 15% of sampled wells exceed the 10 parts per million drinking standard; extrapolating that result suggested more than 2,600 wells in the county may currently exceed that standard, potentially affecting about 7,000 residents who rely on private wells. He described a modeling exercise using 619 samples and land-use leaching rates that estimated approximately 750,000 pounds of nitrate loading into a 67,000-acre aquifer area annually. The model identified corn production as the largest contributor (roughly 70% in the baseline model), followed by soybeans and other sources; septic systems and lawns were smaller contributors by comparison.

To address the problem, staff emphasized voluntary best management practices (BMPs): increasing nitrogen-use efficiency in corn, cover crops, crop rotation, and reduced manure application rates. Steber said the county prefers voluntary adoption supported by cost-share and education, with regulatory options considered second.

Steber cautioned that lag times and local karst topography complicate modeling; he recommended sustained monitoring and cited that 34 wells showed a statistically verifiable trend in the county's dataset, with 26 increasing and eight decreasing over the study period. The presentation was followed by supervisory questions about health risks (including infant impacts like "blue baby" syndrome), septage land-application practices, and how quickly BMP adoption might reverse trends.