Sinkhole risk in Sampson County, NC: Sinkhole country

Sinkhole country

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

On soluble rock: 77%
At or near the surface: 77%
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 730 of Sampson County's 946 square miles on soluble rock, 730 of them with the rock at or near the surface. With about 60,404 residents (64 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 593 map points about 1.3 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 Sampson County

The closest county with no soluble rock mapped is Chatham County, NC, about 70 miles northwest. 3 of the 6 closest counties land in the same band; the ground changes quickly around here.

Duplin County, NC 25 mi east · 93% at surface
Cumberland County, NC 26 mi west · 23% at surface
Bladen County, NC 29 mi south · 38% at surface
Wayne County, NC 32 mi northeast · 84% at surface
Johnston County, NC 36 mi north · 38% at surface
Harnett County, NC 39 mi northwest · 60% at surface

What Sampson County is built on

The largest mapped soluble unit here is the Black Creek Formation (clay or mud), Cretaceous in age, covering about 73% of the county. Next is the Peedee Formation at 4%.

Against the rest of North Carolina

Sampson County ranks 13 of 100 in North Carolina for soluble rock at the surface, and sits above 94% of US counties on that measure.