Sinkhole risk in Harnett County, NC: Sinkhole country

Sinkhole country

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

On soluble rock: 60%
At or near the surface: 60%
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 354 of Harnett County's 595 square miles on soluble rock, 354 of them with the rock at or near the surface. With about 146,096 residents (245 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 582 map points about 1.0 miles apart, so a pocket smaller than that can be missed or overstated.

Worth reading for this county: the signs to look for and how an inspection works, and how these percentages are measured.

Counties around Harnett County

The closest county with no soluble rock mapped is Chatham County, NC, about 32 miles northwest. 1 of the 6 closest counties land in the same band; the ground changes quickly around here.

Lee County, NC 18 mi northwest · 26% at surface
Cumberland County, NC 22 mi south · 23% at surface
Johnston County, NC 30 mi east · 38% at surface
Chatham County, NC 32 mi northwest · 0% at surface
Wake County, NC 32 mi northeast · 8% at surface
Hoke County, NC 32 mi southwest · 83% at surface

The rock underneath

The largest mapped soluble unit here is the Middendorf Formation (sand), Cretaceous in age, covering about 57% of the county. Next is the Yorktown Formation and Duplin Formation, Undivided at 1%.

Against the rest of North Carolina

Harnett County ranks 21 of 100 in North Carolina for soluble rock at the surface, and sits above 90% of US counties on that measure.