St. Croix County staff report rising groundwater nitrates, expand monitoring and cost‑share outreach

St. Croix County Land & Water staff presented a year‑long update on water‑quality monitoring and outreach that shows persistent nitrate contamination in parts of the county and a plan to scale up targeted action.

Tim Stever, the county’s Land and Water Conservation Administrator, told the committee the 2016 Water Quality Study Group’s recommendations led to a sustained monitoring program and mapping work to identify sensitive areas. He said staff have built a network of monitoring wells, mapped sinkholes and karst features that affect groundwater vulnerability, and run clinics that have collected nearly 2,000 samples over five years.

The report said staff used available data and modeling (including a DRASTIC‑style vulnerability model and focused HUC‑12 evaluations) to prioritize watersheds for action and to relate high nitrate wells to land use and well construction. "If a person cases their well below the bedrock, they generally have cleaner water," Stever said, explaining staff findings that geology and well construction strongly influence nitrate results in the county’s karst terrain.

Patty Schrank, the county’s Water Resource Specialist, presented results from the Citizen Groundwater Monitoring Program (CGMP) and a small septic‑density pilot. The CGMP sampled 167 volunteer wells in 2024 and found an average nitrate concentration of 5.48 mg/L (range 0–46.7 mg/L). Schrank said 12% of the CGMP samples exceeded 10 mg/L — the EPA drinking‑water standard — and that roughly 48% of monitored wells show increasing nitrate trends since 2019; 23 wells showed statistically significant trends (17 increasing, about five decreasing or explained by a new well).

Schrank described geographic concentration: central St. Croix County, including the Kinnickinnic Headwaters, contains a disproportionate share of wells above 10 mg/L and shallower well depths. For one municipal well in Roberts, trend extrapolation suggested it could reach 10 mg/L by about 2048 if current trends continue.

To address the problem, staff outlined a multi‑part 2025 plan: expand nitrate clinics to achieve at least 25 samples per township (to support a 'tier status' analysis), implement a USDA National Water Quality Initiative in the Kinnickinnic Headwaters (a 67,000‑acre focus area where average private‑well nitrates run ~6.9 mg/L), develop modeled stacks of best management practices (BMPs) to identify cost‑effective combinations, and make cost‑share funding available through USDA for BMP implementation next year.

The county is also piloting a conductivity‑based approach to flag likely bacteria events for homeowners, conducting aquatic invasive species monitoring and prevention (DNR‑supported wader wash stations and plant surveys), and maintaining monitoring wells to track groundwater levels near Hudson.

Stever and Schrank told supervisors that some regulatory options are constrained by state statute and NR151 standards, limiting the county’s ability to impose stricter erosion or well‑construction rules without state changes. They emphasized voluntary and incentive‑based tools — cost‑share, soil sampling assistance and targeted outreach — as the near‑term path forward. Schrank highlighted a new soil‑sampling cost‑share program that reduces the per‑acre cost of nutrient‑management planning by subsidizing sample collection and analysis.

The presentation closed with supervisors asking follow‑up questions about cost of deeper wells, follow‑up on clinic participants, municipal pumping rates and the role of agriculture in nitrate loads. Staff said they have coordinated with Health & Human Services on outreach and that more trend data will be available as the CGMP continues.

The committee did not take a formal vote on new regulatory measures during the meeting; staff were asked to return with updates and to present actions that would help move trend lines in a budget‑conscious way.