Sinkhole risk in Hardin County, KY: Sinkhole country

Sinkhole country

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

On soluble rock: 89%
At or near the surface: 89%
Buried under cover: 0%

What to do about a house in Hardin County

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

That works out to roughly 557 of Hardin County's 624 square miles on soluble rock, 557 of them with the rock at or near the surface. With about 112,826 residents (181 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 501 map points about 1.1 miles apart, so a pocket smaller than that can be missed or overstated.

Counties around Hardin County

The closest county with no soluble rock mapped is Spencer County, IN, about 61 miles west. 5 of the 6 closest counties land in the same band, so this is a regional pattern rather than a local quirk.

Larue County, KY 18 mi southeast · 78% at surface
Meade County, KY 23 mi northwest · 91% at surface
Bullitt County, KY 24 mi northeast · 42% at surface
Breckinridge County, KY 26 mi west · 89% at surface
Grayson County, KY 27 mi southwest · 60% at surface
Hart County, KY 27 mi south · 89% at surface

The rock underneath

The largest mapped soluble unit here is the Ste. Genevieve and St. Louis Limestones, undivided (limestone), Mississippian in age, covering about 60% of the county. Next is the Rocks of Chesterian age, lower part at 20%.

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 Kentucky

Hardin County ranks 9 of 120 in Kentucky for soluble rock at the surface, and sits above 97% of US counties on that measure.