Sinkhole risk in Sullivan County, NH: 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: 2%
At or near the surface: 0%
Buried under cover: 2%

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 13 of Sullivan County's 538 square miles on soluble rock. With about 44,012 residents (82 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 247 map points about 1.5 miles apart, so a pocket smaller than that can be missed or overstated.

Two things to read before deciding: how these percentages are measured, and the warning signs that apply anywhere.

Counties around Sullivan County

The nearest county rated sinkhole country is Union County, PA, about 298 miles southwest. 2 of the 6 closest counties land in the same band; the ground changes quickly around here.

Windsor County, VT 24 mi northwest · 0% at surface
Merrimack County, NH 28 mi east · 0% at surface
Cheshire County, NH 30 mi south · 0% at surface
Windham County, VT 36 mi southwest · 0% at surface
Hillsborough County, NH 40 mi southeast · 0% at surface
Belknap County, NH 41 mi east · 0% at surface

Which formation it is

The largest mapped soluble unit here is the Fitch and Clough Formations, undivided (quartzite), Silurian in age, covering about 2% of the county.

Against the rest of New Hampshire

Sullivan County ranks 10 of 10 in New Hampshire for soluble rock at the surface, and sits above 0% of US counties on that measure.