Sinkhole risk in Grant County, IN: 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: 100%
At or near the surface: 0%
Buried under cover: 100%

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 414 of Grant County's 414 square miles on soluble rock. With about 66,458 residents (160 per square mile), there is effectively nowhere in the county off the soluble rock, town or country. The figures come from 398 map points about 1.0 miles apart, so a pocket smaller than that can be missed or overstated.

Two things to read before deciding: why the 100% under cover still counts, and how these percentages are measured.

Counties around Grant County

The nearest county rated sinkhole country is Monroe County, IN, about 104 miles southwest. 6 of the 6 closest counties land in the same band, so this is a regional pattern rather than a local quirk.

Blackford County, IN 18 mi east · 0% at surface
Huntington County, IN 23 mi northeast · under 1% at surface
Wabash County, IN 24 mi north · 0% at surface
Delaware County, IN 24 mi southeast · 0% at surface
Howard County, IN 24 mi west · 0% at surface
Madison County, IN 24 mi south · 0% at surface

What Grant County is built on

The largest mapped soluble unit here is the Wabash Formation (limestone), Silurian in age, covering about 62% of the county. Next is the Pleasant Mills Formation at 27%.

Against the rest of Indiana

Grant County ranks 51 of 92 in Indiana for soluble rock at the surface, and sits above 0% of US counties on that measure.