Sinkhole risk in Washington County, TN: Sinkhole country

Sinkhole country

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

On soluble rock: 88%
At or near the surface: 88%
Buried under cover: 0%

What to do about a house in Washington County

Get a sinkhole or geotechnical inspection before buying, building or adding weight to a foundation.

That works out to roughly 286 of Washington County's 327 square miles on soluble rock, 286 of them with the rock at or near the surface. With about 139,642 residents (428 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 249 map points about 1.1 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 Washington County

The closest county with no soluble rock mapped is Mitchell County, NC, about 27 miles southeast. 3 of the 6 closest counties land in the same band; the ground changes quickly around here.

Unicoi County, TN 14 mi south · 11% at surface
Sullivan County, TN 18 mi northeast · 92% at surface
Carter County, TN 21 mi east · 25% at surface
Greene County, TN 21 mi west · 88% at surface
Hawkins County, TN 27 mi northwest · 73% at surface
Mitchell County, NC 27 mi southeast · 0% at surface

What Washington County is built on

The largest mapped soluble unit here is the Knox Group (dolostone (dolomite)), Ordovician to Cambrian in age, covering about 64% of the county. Next is the Sevier Shale at 8%.

Against the rest of Tennessee

Washington County ranks 16 of 95 in Tennessee for soluble rock at the surface, and sits above 96% of US counties on that measure.