Sinkhole risk in Addison 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: 50%
At or near the surface: under 1%
Buried under cover: 50%

The next step for one property

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

That works out to roughly 383 of Addison County's 766 square miles on soluble rock, 3 of them with the rock at or near the surface. With about 38,047 residents (50 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 248 map points about 1.8 miles apart, so a pocket smaller than that can be missed or overstated.

Two things to read before deciding: why the 50% under cover still counts, and how these percentages are measured.

Counties around Addison County

The nearest county rated sinkhole country is Union County, PA, about 291 miles southwest. 5 of the 6 closest counties land in the same band, so this is a regional pattern rather than a local quirk.

Rutland County, VT 29 mi south · under 1% at surface
Chittenden County, VT 30 mi north · 0% at surface
Washington County, VT 31 mi northeast · 0% at surface
Essex County, NY 32 mi west · 0% at surface
Orange County, VT 38 mi east · 0% at surface
Windsor County, VT 42 mi southeast · 0% at surface

Which formation it is

The largest mapped soluble unit here is the Stony Point Formation (black shale), Ordovician in age, covering about 9% of the county. Next is the Monkton Quartzite at 5%.

Against the rest of Vermont

Addison County ranks 3 of 14 in Vermont for soluble rock at the surface, and sits above 52% of US counties on that measure.