Sinkhole risk in Franklin County, OH: 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: 47%
At or near the surface: 0%
Buried under cover: 47%

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 249 of Franklin County's 532 square miles on soluble rock. With about 1,356,303 residents (2,547 per square mile), most of the county is built up, so a mapped unit is likely to sit under somebody's street. The figures come from 353 map points about 1.2 miles apart, so a pocket smaller than that can be missed or overstated.

Two things to read before deciding: why the 47% under cover still counts, and how these percentages are measured.

Counties around Franklin County

The nearest county rated sinkhole country is Mason County, KY, about 105 miles southwest. 3 of the 6 closest counties land in the same band; the ground changes quickly around here.

Delaware County, OH 21 mi north · 0% at surface
Madison County, OH 21 mi west · 0% at surface
Pickaway County, OH 22 mi south · 0% at surface
Fairfield County, OH 25 mi southeast · 0% at surface
Licking County, OH 29 mi east · 0% at surface
Union County, OH 29 mi northwest · 0% at surface

Which formation it is

The largest mapped soluble unit here is the Columbus Limestone (limestone), Devonian in age, covering about 26% of the county. Next is the Salina Group at 15%.

Against the rest of Ohio

Franklin County ranks 31 of 88 in Ohio for soluble rock at the surface, and sits above 0% of US counties on that measure.