Sinkhole risk in Ste. Genevieve County, MO: Sinkhole country

Sinkhole country

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

On soluble rock: 76%
At or near the surface: 76%
Buried under cover: under 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 381 of Ste. Genevieve County's 499 square miles on soluble rock, 379 of them with the rock at or near the surface. With about 18,546 residents (37 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 575 map points about 0.9 miles apart, so a pocket smaller than that can be missed or overstated.

Counties around Ste. Genevieve County

The closest county with no soluble rock mapped is Perry County, IL, about 45 miles east. 4 of the 6 closest counties land in the same band, so this is a regional pattern rather than a local quirk.

St. Francois County, MO 18 mi west · 71% at surface
Randolph County, IL 22 mi northeast · under 1% at surface
Perry County, MO 23 mi southeast · 86% at surface
Monroe County, IL 27 mi north · 6% at surface
Madison County, MO 30 mi south · 67% at surface
Jefferson County, MO 33 mi northwest · 98% at surface

What Ste. Genevieve County is built on

The largest mapped soluble unit here is the Smithville Dolomite, Powell Dolomite, Cotter Dolomite, Jefferson City Dolomite (dolostone (dolomite)), Early Ordovician-Ibexian Series in age, covering about 14% of the county. Next is the Gasconade Dolomite at 12%.

The county also lies over the Illinois Basin, a deep salt or gypsum basin. Deep beds rarely cause surface collapse on their own, but wells and mining into them have.

Against the rest of Missouri

Ste. Genevieve County ranks 47 of 115 in Missouri for soluble rock at the surface, and sits above 94% of US counties on that measure.