Sinkhole risk in Dunn County, WI: Mostly deep or small

Mostly deep or small

Some soluble rock, mostly deeply buried or in a small share of the county.

On soluble rock: 4%
At or near the surface: 2%
Buried under cover: 1%

What this means before you buy

Sinkholes are uncommon here; watch for new depressions after heavy rain or leaking pipes.

That works out to roughly 31 of Dunn County's 850 square miles on soluble rock, 20 of them with the rock at or near the surface. With about 46,135 residents (54 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 376 map points about 1.5 miles apart, so a pocket smaller than that can be missed or overstated.

Two things to read before deciding: how these percentages are measured, and the warning signs that apply anywhere.

Counties around Dunn County

The nearest county rated sinkhole country is Vernon County, WI, about 107 miles southeast. 1 of the 6 closest counties land in the same band; the ground changes quickly around here.

Pepin County, WI 22 mi south · 23% at surface
St. Croix County, WI 27 mi west · 1% at surface
Pierce County, WI 30 mi southwest · 35% at surface
Chippewa County, WI 31 mi east · 0% at surface
Eau Claire County, WI 34 mi southeast · 0% at surface
Barron County, WI 34 mi north · 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 4% of the county.

Against the rest of Wisconsin

Dunn County ranks 17 of 72 in Wisconsin for soluble rock at the surface, and sits above 59% of US counties on that measure.