Flood Zones Along the Big River in St. Francois County, Missouri

How flooding and Superfund contamination overlap here

The Big River Mine Tailings/St. Joe Minerals Corp. Superfund site is organized by EPA into multiple operable units, and the one most relevant to a floodplain land buyer is Operable Unit 02: the Big River off-source study, which investigates how lead-contaminated sediment from the old Lead Belt mining piles has moved downstream and settled into the river's floodplain over decades of high-water events. EPA issued an Engineering Evaluation/Cost Analysis for this off-source work and opened it for public comment through September 17, 2025 -- meaning the scope and remedy for floodplain sediment along the Big River was still being actively defined as of this review, not a settled, closed-out cleanup.

Separately, Operable Unit 01 covers residential yard cleanup: a 2018 consent decree with Doe Run Resources Corporation set up an $80 million-plus program targeting roughly 4,100 contaminated residential properties, and a February 2025 five-year review recommended EPA re-evaluate whether the residential soil lead cleanup standard still matches current national guidance. The practical takeaway for a buyer is that this is not historical background -- it is an open, evolving federal cleanup with a live sediment study and a recently flagged soil-standard question, both bearing directly on floodplain and near-floodplain land in this specific county.

What to actually check before buying floodplain land here

Start with the ordinary FEMA check: pull the current Flood Insurance Rate Map for the parcel through the FEMA Flood Map Service Center, and confirm with the relevant floodplain administrator -- the county's Charles "Bob" Turner for unincorporated land, or the applicable city's own administrator (Bonne Terre, Desloge, Farmington, Iron Mountain Lake, Leadwood, and Park Hills each have one) if the parcel sits inside city limits -- whether a Special Flood Hazard Area designation would trigger an elevation certificate or floodplain development permit for your planned use.

Then check the parcel separately against EPA's Big River Mine Tailings site maps and operable-unit boundaries, available through the site's EPA profile page, particularly if the property is near Bonne Terre, Desloge, Leadwood, or the Big River corridor itself. If the parcel falls within a study or remediation area, ask directly what soil testing has been done, whether any remediation has occurred or is planned, and whether EPA or Doe Run Resources Corporation (the responsible party under the 2018 consent decree) has any pending obligations tied to that specific address. A seller's silence on this point is not the same as a clean bill of health -- given that the residential-yard program has already covered roughly 4,100 properties countywide, it is a reasonable, specific question to ask rather than an alarmist one.

Finally, remember that mine waste in this county was historically used well outside the river corridor -- as fill dirt, driveway aggregate, and winter road material -- so a parcel that reads as low flood risk on a FEMA map is not automatically free of the same soil questions. If your plans for the land include a garden, livestock, or young children playing in the yard, a soil test is a reasonable step regardless of the parcel's flood-zone designation, and the county Health Center's Environmental Health division is a starting point for a referral even though soil-lead testing itself is generally arranged privately or through EPA's ongoing program rather than the county directly.