SinkholeOdds

Sinkhole risk in McDonough County, IL: 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
19%
At or near the surface
under 1%
Buried under cover
19%

What to do about a house in McDonough County

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

That works out to roughly 114 of McDonough County's 589 square miles on soluble rock, 3 of them with the rock at or near the surface. With about 26,662 residents (45 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 391 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 gypsum and salt move faster than limestone, and why the 19% under cover still counts.

Counties around McDonough County

The nearest county rated sinkhole country is Calhoun County, IL, about 89 miles south. 5 of the 6 closest counties land in the same band, so this is a regional pattern rather than a local quirk.

The rock underneath

The largest mapped soluble unit here is the Middle Valmeyeran (Salem, Warsaw, Borden, Springville; includes thin Mvl and Mk in south and east) Series (limestone), Mississippian in age, covering about 12% of the county. Next is the Lower Valmeyeran (Keokuk-Sedalia) Series at 4%.

The county also lies over the Illinois Basin, a deep salt or gypsum basin. Deep beds rarely cause surface collapse on their own, but wells and mining into them have.

Against the rest of Illinois

McDonough County ranks 25 of 102 in Illinois for soluble rock at the surface, and sits above 53% of US counties on that measure.