Sinkhole risk in Orangeburg 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: 72%
Buried under cover: 26%

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 1,088 of Orangeburg County's 1,106 square miles on soluble rock, 798 of them with the rock at or near the surface. With about 83,129 residents (75 per square mile), there is effectively nowhere in the county off the soluble rock, town or country. The figures come from 476 map points about 1.5 miles apart, so a pocket smaller than that can be missed or overstated.

Counties around Orangeburg County

The closest county with no soluble rock mapped is Saluda County, SC, about 66 miles northwest. 5 of the 6 closest counties land in the same band, so this is a regional pattern rather than a local quirk.

Calhoun County, SC 17 mi north · 62% at surface
Bamberg County, SC 22 mi southwest · 84% at surface
Dorchester County, SC 34 mi southeast · 61% at surface
Clarendon County, SC 37 mi northeast · 79% at surface
Barnwell County, SC 38 mi west · 45% at surface
Sumter County, SC 41 mi northeast · 77% at surface

Which formation it is

The largest mapped soluble unit here is the Duplin Formation (sand), Pliocene in age, covering about 44% of the county. Next is the Huber/Lisbon/Barnwell Formations, undivided at 38%.

Against the rest of South Carolina

Orangeburg County ranks 9 of 46 in South Carolina for soluble rock at the surface, and sits above 93% of US counties on that measure.