Sinkhole risk in Winneshiek County, IA: Pockets of it

Pockets of it

Soluble rock at the surface or under thin cover in part of the county.

On soluble rock: 95%
At or near the surface: 18%
Buried under cover: 78%

What to do about a house in Winneshiek County

Check the parcel against your state survey sinkhole map, and ask for an inspection if cracks, depressions or sticking doors show up.

That works out to roughly 657 of Winneshiek County's 690 square miles on soluble rock, 121 of them with the rock at or near the surface. With about 19,723 residents (29 per square mile), there is effectively nowhere in the county off the soluble rock, town or country. The figures come from 399 map points about 1.3 miles apart, so a pocket smaller than that can be missed or overstated.

Counties around Winneshiek County

The nearest county rated sinkhole country is Clayton County, IA, about 41 miles southeast. 4 of the 6 closest counties land in the same band, so this is a regional pattern rather than a local quirk.

Allamakee County, IA 24 mi east · 25% at surface
Howard County, IA 24 mi west · 5% at surface
Chickasaw County, IA 28 mi southwest · 0% at surface
Fillmore County, MN 29 mi northwest · 26% at surface
Fayette County, IA 30 mi south · 19% at surface
Houston County, MN 31 mi northeast · 28% at surface

What Winneshiek County is built on

The largest mapped soluble unit here is the Maquoketa Formation (shale), Late Ordovician-Cincinnatian series in age, covering about 41% of the county. Next is the Galena-Decorah-Platteville Formations at 31%.

Against the rest of Iowa

Winneshiek County ranks 6 of 99 in Iowa for soluble rock at the surface, and sits above 73% of US counties on that measure.