Sinkhole risk in St. Croix 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: 79%
At or near the surface: 1%
Buried under cover: 78%

What to do about a house in St. Croix County

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

That works out to roughly 570 of St. Croix County's 722 square miles on soluble rock, 9 of them with the rock at or near the surface. With about 97,954 residents (136 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 389 map points about 1.4 miles apart, so a pocket smaller than that can be missed or overstated.

Counties around St. Croix County

The nearest county rated sinkhole country is Vernon County, WI, about 127 miles southeast. 5 of the 6 closest counties land in the same band, so this is a regional pattern rather than a local quirk.

Pierce County, WI 21 mi south · 35% at surface
Washington County, MN 22 mi west · 0% at surface
Dunn County, WI 27 mi east · 2% at surface
Polk County, WI 30 mi north · 0% at surface
Ramsey County, MN 32 mi west · 0% at surface
Dakota County, MN 39 mi southwest · 0% at surface

What St. Croix County is built on

The largest mapped soluble unit here is the Prairie du Chien Group (shale), Lower Ordovician in age, covering about 61% of the county. Next is the Ancell Group at 18%.

Against the rest of Wisconsin

St. Croix County ranks 18 of 72 in Wisconsin for soluble rock at the surface, and sits above 56% of US counties on that measure.