Sinkhole risk in Sauk 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: 16%
At or near the surface: 16%
Buried under cover: 0%

What to do about a house in Sauk 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 133 of Sauk County's 832 square miles on soluble rock, 133 of them with the rock at or near the surface. With about 66,486 residents (80 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 281 map points about 1.7 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 Sauk County

The nearest county rated sinkhole country is Iowa County, WI, about 31 miles south, close enough that the same rock may run under the county line. 2 of the 6 closest counties land in the same band; the ground changes quickly around here.

Richland County, WI 25 mi west · 41% at surface
Columbia County, WI 31 mi east · under 1% at surface
Iowa County, WI 31 mi south · 77% at surface
Juneau County, WI 36 mi north · 0% at surface
Dane County, WI 36 mi southeast · 19% at surface
Marquette County, WI 38 mi northeast · 0% at surface

Which formation it is

The largest mapped soluble unit here is the Prairie du Chien Group (shale), Lower Ordovician in age, covering about 16% of the county.

Against the rest of Wisconsin

Sauk County ranks 13 of 72 in Wisconsin for soluble rock at the surface, and sits above 72% of US counties on that measure.