Sinkhole risk in Winnebago County, WI: Pockets of it

Pockets of it

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

On soluble rock: 52%
At or near the surface: under 1%
Buried under cover: 52%

What this means before you buy

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 228 of Winnebago County's 435 square miles on soluble rock, 1 of them with the rock at or near the surface. With about 173,307 residents (399 per square mile), homes are spread across towns and farmland, and a mapped unit may or may not reach the developed parts. The figures come from 391 map points about 1.1 miles apart, so a pocket smaller than that can be missed or overstated.

Two things to read before deciding: why the 52% under cover still counts, and the signs to look for and how an inspection works.

Counties around Winnebago County

The nearest county rated sinkhole country is Iowa County, WI, about 105 miles southwest. 1 of the 6 closest counties land in the same band; the ground changes quickly around here.

Calumet County, WI 23 mi east · 0% at surface
Fond du Lac County, WI 24 mi south · 0% at surface
Outagamie County, WI 25 mi northeast · 0% at surface
Green Lake County, WI 26 mi southwest · 0% at surface
Waushara County, WI 28 mi west · 0% at surface
Waupaca County, WI 31 mi northwest · 0% at surface

The rock underneath

The largest mapped soluble unit here is the Sinnipee Group (dolostone (dolomite)), Ordovician in age, covering about 29% of the county. Next is the Prairie du Chien Group at 12%.

Against the rest of Wisconsin

Winnebago County ranks 24 of 72 in Wisconsin for soluble rock at the surface, and sits above 51% of US counties on that measure.