Sinkhole risk in Fayette County, PA: Pockets of it

Pockets of it

Soluble rock at the surface or under thin cover in part of the county.

On soluble rock: 23%
At or near the surface: 23%
Buried under cover: 0%

What this means before you buy

Check the parcel against your state survey sinkhole map, and ask for an inspection if cracks, depressions or sticking doors show up.

That works out to roughly 179 of Fayette County's 791 square miles on soluble rock, 179 of them with the rock at or near the surface. With about 123,941 residents (157 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 292 map points about 1.6 miles apart, so a pocket smaller than that can be missed or overstated.

Two things to read before deciding: why gypsum and salt move faster than limestone, and the signs to look for and how an inspection works.

Counties around Fayette County

The nearest county rated sinkhole country is Winchester city, VA, about 93 miles southeast. 1 of the 6 closest counties land in the same band; the ground changes quickly around here.

Westmoreland County, PA 29 mi north · 26% at surface
Monongalia County, WV 30 mi southwest · 12% at surface
Preston County, WV 31 mi south · 2% at surface
Greene County, PA 31 mi west · 8% at surface
Garrett County, MD 32 mi southeast · 8% at surface
Somerset County, PA 33 mi east · 5% at surface

Which formation it is

The largest mapped soluble unit here is the Monongahela Group (limestone), Pennsylvanian in age, covering about 17% of the county. Next is the Mauch Chunk Formation at 6%.

The county also lies over the Michigan Basin; Ohio Basin; Appalachian Basin, a deep salt or gypsum basin. Deep beds rarely cause surface collapse on their own, but wells and mining into them have.

Against the rest of Pennsylvania

Fayette County ranks 25 of 67 in Pennsylvania for soluble rock at the surface, and sits above 76% of US counties on that measure.