Sinkhole risk in Frederick County, VA: Pockets of it

Pockets of it

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

On soluble rock: 30%
At or near the surface: 30%
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 123 of Frederick County's 413 square miles on soluble rock, 123 of them with the rock at or near the surface. With about 98,109 residents (237 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 506 map points about 0.9 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 Frederick County

The nearest county rated sinkhole country is Winchester city, VA, about 5 miles southeast, close enough that the same rock may run under the county line. 2 of the 6 closest counties land in the same band; the ground changes quickly around here.

Winchester city, VA 5 mi southeast · 90% at surface
Clarke County, VA 16 mi southeast · 74% at surface
Hampshire County, WV 20 mi west · 8% at surface
Warren County, VA 21 mi south · 23% at surface
Berkeley County, WV 21 mi northeast · 44% at surface
Jefferson County, WV 23 mi east · 84% at surface

Which formation it is

The largest mapped soluble unit here is the Beekmantown Group (dolostone (dolomite)), Ordovician in age, covering about 9% of the county. Next is the Conococheague Formation at 7%.

Against the rest of Virginia

Frederick County ranks 38 of 133 in Virginia for soluble rock at the surface, and sits above 79% of US counties on that measure.