Sinkhole risk in Franklin County, VT: Mostly deep or small

Mostly deep or small

Some soluble rock, mostly deeply buried or in a small share of the county.

On soluble rock: 23%
At or near the surface: under 1%
Buried under cover: 23%

What to do about a house in Franklin County

Sinkholes are uncommon here; watch for new depressions after heavy rain or leaking pipes.

That works out to roughly 147 of Franklin County's 631 square miles on soluble rock, 4 of them with the rock at or near the surface. With about 51,066 residents (81 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 287 map points about 1.5 miles apart, so a pocket smaller than that can be missed or overstated.

Counties around Franklin County

The nearest county rated sinkhole country is Union County, PA, about 341 miles southwest. 5 of the 6 closest counties land in the same band, so this is a regional pattern rather than a local quirk.

Grand Isle County, VT 20 mi west · 1% at surface
Lamoille County, VT 22 mi southeast · 0% at surface
Chittenden County, VT 28 mi south · 0% at surface
Orleans County, VT 32 mi east · under 1% at surface
Clinton County, NY 40 mi west · under 1% at surface
Washington County, VT 43 mi south · 0% at surface

The rock underneath

The largest mapped soluble unit here is the Iberville Formation (black shale), Ordovician in age, covering about 6% of the county. Next is the Morses Line Formation at 5%.

Against the rest of Vermont

Franklin County ranks 2 of 14 in Vermont for soluble rock at the surface, and sits above 54% of US counties on that measure.