Sinkhole risk in Darlington County, SC: Sinkhole country

Sinkhole country

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

On soluble rock: 87%
At or near the surface: 87%
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 486 of Darlington County's 561 square miles on soluble rock, 486 of them with the rock at or near the surface. With about 62,425 residents (111 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 510 map points about 1.0 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 Darlington County

The closest county with no soluble rock mapped is Union County, NC, about 56 miles northwest. 6 of the 6 closest counties land in the same band, so this is a regional pattern rather than a local quirk.

Lee County, SC 20 mi southwest · 88% at surface
Chesterfield County, SC 24 mi northwest · 63% at surface
Marlboro County, SC 25 mi northeast · 64% at surface
Florence County, SC 25 mi southeast · 77% at surface
Dillon County, SC 34 mi east · 79% at surface
Kershaw County, SC 36 mi west · 57% at surface

The rock underneath

The largest mapped soluble unit here is the Duplin Formation (sand), Pliocene in age, covering about 61% of the county. Next is the Bear Bluff Formation at 14%.

Against the rest of South Carolina

Darlington County ranks 2 of 46 in South Carolina for soluble rock at the surface, and sits above 96% of US counties on that measure.