Sinkhole risk in Clarendon County, SC: Sinkhole country

Sinkhole country

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

On soluble rock: 98%
At or near the surface: 79%
Buried under cover: 19%

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 595 of Clarendon County's 607 square miles on soluble rock, 478 of them with the rock at or near the surface. With about 31,030 residents (51 per square mile), there is effectively nowhere in the county off the soluble rock, town or country. The figures come from 542 map points about 1.1 miles apart, so a pocket smaller than that can be missed or overstated.

Worth reading for this county: why the 19% under cover still counts, and the signs to look for and how an inspection works.

Counties around Clarendon County

The closest county with no soluble rock mapped is Fairfield County, SC, about 73 miles northwest. 4 of the 6 closest counties land in the same band, so this is a regional pattern rather than a local quirk.

Sumter County, SC 20 mi northwest · 77% at surface
Williamsburg County, SC 29 mi east · 31% at surface
Calhoun County, SC 32 mi west · 62% at surface
Lee County, SC 34 mi north · 88% at surface
Berkeley County, SC 35 mi southeast · 30% at surface
Orangeburg County, SC 37 mi southwest · 72% at surface

Which formation it is

The largest mapped soluble unit here is the Bear Bluff Formation (calcareous sand), Pliocene in age, covering about 44% of the county.

Against the rest of South Carolina

Clarendon County ranks 4 of 46 in South Carolina for soluble rock at the surface, and sits above 94% of US counties on that measure.