Well Water in Fillmore County, Minnesota

MDA's own township testing found five Fillmore County townships with real nitrate exceedances

Fillmore County participated in the Minnesota Department of Agriculture's Township Testing Program alongside other Southeast Minnesota counties, with ten townships specifically sampled: Money Creek, Houston, Sheldon, Union, Black Hammer, Caledonia, Mayville, Spring Grove, Wilmington, and Winnebago. The program's final results identified five of those ten townships -- Black Hammer, Caledonia, Mayville, Spring Grove, and Wilmington -- where 10 percent or more of tested private wells came back above the health risk limit (HRL) for nitrate. That's a meaningfully different due-diligence signal than a generic 'rural wells can have nitrate' caveat: it's a specific, published, township-level result tied directly to Fillmore County's own karst hydrogeology, where thin soils over fractured limestone let surface-applied nitrogen move into groundwater faster than it would over more typical glacial till.

A well testing above the HRL doesn't necessarily mean an existing well on a specific parcel is contaminated -- results vary well to well even within the same township -- but a parcel located in one of these five townships warrants a fresh nitrate test as part of due diligence rather than reliance on an old test result or none at all, and homeowners who test above the HRL are typically offered follow-up nitrate-and-pesticide testing through MDA's Private Well Pesticide Sampling project as a next step.

A well-sealing cost-share program addresses the karst-specific abandoned-well risk

Older Fillmore County farmsteads commonly carry one or more old, unused wells that were never properly sealed when a replacement well was drilled -- and in karst terrain, an unsealed abandoned well is a direct, open conduit connecting the land surface to groundwater, bypassing the natural filtering that intact soil and rock would otherwise provide. The Fillmore Soil and Water Conservation District runs a specific cost-share program to address exactly this: financial assistance covering 75 percent of the cost, up to $2,000, to properly seal an unused well, prioritized for locations in a highly vulnerable area for drinking water -- which describes much of the county's karst terrain. Landowners interested in this cost-share should contact Fillmore SWCD directly (507-887-0240) rather than assume an old well on a newly purchased property is someone else's problem to have already solved.

Minnesota's statewide well code (Minn. Stat. ch. 103I; Minn. R. ch. 4725) defines an abandoned well as one whose use has been permanently discontinued or whose disrepair makes continued use impracticable, and requires such wells to be sealed by a licensed contractor -- this isn't a Fillmore-specific legal obligation, but the county's karst geology is exactly the kind of setting the Minnesota Department of Health's own wellhead-protection guidance flags as the highest-consequence place for that statewide requirement to actually matter.

What this means when buying land with an existing well

1. Check whether the target parcel sits in Black Hammer, Caledonia, Mayville, Spring Grove, or Wilmington township -- MDA's own published results flag these five as having 10%+ of tested wells over the nitrate health risk limit -- and treat that as a reason to test before closing, not after.
2. Commission a fresh nitrate and coliform test on any well you're relying on for drinking water, regardless of township, given how quickly karst groundwater conditions can shift; don't rely on a seller-provided test that's more than a year or two old.
3. Walk the property (or ask the seller directly) for any old, unused, or capped-but-not-properly-sealed wells, especially on a farmstead with a documented well-replacement history -- these are common and are the specific hazard Fillmore SWCD's cost-share program exists to address.
4. If an unsealed well is found, contact Fillmore SWCD (507-887-0240) about the 75%/$2,000 cost-share before assuming full sealing cost falls entirely on the buyer.
5. Don't assume a deeper well is automatically safe from nitrate: MDH's own guidance notes drilling into a deeper aquifer may lower nitrate concentration in karst areas but is not a guaranteed long-term solution, so periodic retesting matters even for a well that tested clean once.