Sinkhole risk in Alleghany 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: 18%
At or near the surface: 18%
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 79 of Alleghany County's 447 square miles on soluble rock, 79 of them with the rock at or near the surface. With about 14,632 residents (33 per square mile), much of the land is open, and the mapped rock may sit far from where people actually live. The figures come from 500 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 Alleghany County

The nearest county rated sinkhole country is Rockbridge County, VA, about 31 miles east, close enough that the same rock may run under the county line. 5 of the 6 closest counties land in the same band, so this is a regional pattern rather than a local quirk.

Covington city, VA 1 mi east · 26% at surface
Botetourt County, VA 19 mi southeast · 49% at surface
Bath County, VA 25 mi northeast · 24% at surface
Craig County, VA 25 mi southwest · 34% at surface
Greenbrier County, WV 26 mi west · 35% at surface
Rockbridge County, VA 31 mi east · 57% at surface

What Alleghany County is built on

The largest mapped soluble unit here is the Ridgeley Sandstone, Helderberg and Cayugan Groups (sandstone), Silurian-Devonian in age, covering about 13% of the county. Next is the Moccasin or Bays Formation through Blackford Formation at 3%.

Against the rest of Virginia

Alleghany County ranks 47 of 133 in Virginia for soluble rock at the surface, and sits above 73% of US counties on that measure.