St. Croix County committee hears groundwater update; staff propose multi-year nitrate plan
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Summary
County staff presented new groundwater monitoring and nitrate-screening data showing persistent nitrate issues in central St. Croix County and proposed a multi‑year, USDA‑funded program of best‑management practice contracts; committee members urged seeking funding and sharing results with the full board.
St. Croix County staff outlined the results of 2025 groundwater monitoring and proposed a multi‑year nitrate‑reduction plan at the Community Development Committee meeting on Jan. 15.
Patty, the county water resource specialist, said the county’s nitrate-screening clinics and the Community Groundwater Monitoring Program (CGMP) show a consistent, geographically concentrated problem. “Nitrate is the most common, groundwater contaminant in Wisconsin and in Saint Croix County,” Patty said, and added that clinic screening results averaged 7.77 milligrams per liter while the CGMP average was 5.48 mg/L. Patty said 27% of clinic screening samples and about 15% of CGMP samples exceeded the EPA drinking‑water standard of 10 mg/L.
An unnamed staff presenter described a groundwater protection plan focused on the Roberts/Hammond/Twin Lakes watersheds and shared a GIS-based load estimate and scenario modeling. The presenter said corn and agricultural practices are the largest contributors to leaching in the affected watershed and that model scenarios show roughly a 21% reduction in leaching is possible with about 50% adoption of key best‑management practices (BMPs). “Corn is is probably the biggest leaching crop that we have,” the presenter said.
Staff presented a funding strategy built around USDA multi‑year contracts and technical assistance, estimating program costs at roughly $270,000 per year for five years (about $1.4 million). The presenter said drilling deeper municipal wells reduces exposure for those systems but is not a viable county‑wide solution for private wells; treatment at the tap helps individuals but does not address source loading.
Committee members commended the data and urged staff to pursue USDA funding and return with formal requests for resolutions of support when the plan is eligible. Several members asked about farmer outreach and incentives; staff said outreach, technical assistance and cost‑share programs would be central to uptake and that monitoring should be part of any large project to verify outcomes.
The committee asked staff to present a summary to the full board and to continue developing the plan and funding applications.
The county’s data include: 469 clinic samples from 448 addresses in 2025; a clinic screening mean of 7.77 mg/L; CGMP coverage of 160 annually sampled wells with a 2025 average of 5.48 mg/L; and a modeled watershed nitrogen load staff reported as about 750,000 pounds. Patty cautioned that screening kits are rapid, in‑field tools and not standardized laboratory tests and that confirmatory lab testing is recommended for samples above the drinking‑water standard.
Next steps include finalizing the plan in USDA format, pursuing multi‑year funding, expanding outreach to producers, and returning to the governing body for formal support when required.
