Sinkhole risk in Union County, TN: 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 this means before you buy

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

That works out to roughly 198 of Union County's 224 square miles on soluble rock, 198 of them with the rock at or near the surface. With about 21,064 residents (94 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 289 map points about 0.9 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 Union County

The closest county with no soluble rock mapped is Whitley County, KY, about 37 miles northwest. 5 of the 6 closest counties land in the same band, so this is a regional pattern rather than a local quirk.

Claiborne County, TN 18 mi northeast · 75% at surface
Grainger County, TN 18 mi east · 79% at surface
Campbell County, TN 20 mi northwest · 28% at surface
Knox County, TN 21 mi south · 95% at surface
Anderson County, TN 23 mi southwest · 50% at surface
Jefferson County, TN 27 mi southeast · 100% at surface

Which formation it is

The largest mapped soluble unit here is the Copper Ridge Dolomite (dolostone (dolomite)), Cambrian in age, covering about 23% of the county. Next is the Longview Dolomite and Chepultepec Dolomite at 14%.

Against the rest of Tennessee

Union County ranks 14 of 95 in Tennessee for soluble rock at the surface, and sits above 96% of US counties on that measure.