Sinkhole risk in Iowa County, WI: Sinkhole country

Sinkhole country

Soluble rock at or near the surface across much of the county.

On soluble rock: 79%
At or near the surface: 77%
Buried under cover: 1%

The next step for one property

Get a sinkhole or geotechnical inspection before buying, building or adding weight to a foundation.

That works out to roughly 601 of Iowa County's 763 square miles on soluble rock, 590 of them with the rock at or near the surface. With about 23,963 residents (31 per square mile), much of the land is open, and the mapped rock may sit far from where people actually live. The figures come from 368 map points about 1.4 miles apart, so a pocket smaller than that can be missed or overstated.

Two things to read before deciding: the signs to look for and how an inspection works, and how these percentages are measured.

Counties around Iowa County

The closest county with no soluble rock mapped is Juneau County, WI, about 64 miles north. 2 of the 6 closest counties land in the same band; the ground changes quickly around here.

Lafayette County, WI 24 mi south · 91% at surface
Grant County, WI 30 mi west · 84% at surface
Richland County, WI 30 mi northwest · 41% at surface
Sauk County, WI 31 mi north · 16% at surface
Green County, WI 35 mi southeast · 38% at surface
Dane County, WI 36 mi east · 19% at surface

What Iowa County is built on

The largest mapped soluble unit here is the Sinnipee Group (dolostone (dolomite)), Ordovician in age, covering about 44% of the county. Next is the Prairie du Chien Group at 18%.

Against the rest of Wisconsin

Iowa County ranks 3 of 72 in Wisconsin for soluble rock at the surface, and sits above 94% of US counties on that measure.