Sinkhole risk in Will County, IL: Pockets of it

Pockets of it

Soluble rock at the surface or under thin cover in part of the county.

On soluble rock: 88%
At or near the surface: 3%
Buried under cover: 86%

What this means before you buy

Check the parcel against your state survey sinkhole map, and ask for an inspection if cracks, depressions or sticking doors show up.

That works out to roughly 739 of Will County's 836 square miles on soluble rock, 23 of them with the rock at or near the surface. With about 708,583 residents (848 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 250 map points about 1.8 miles apart, so a pocket smaller than that can be missed or overstated.

Worth reading for this county: why the 86% under cover still counts, and the signs to look for and how an inspection works.

Counties around Will County

The nearest county rated sinkhole country is Jo Daviess County, IL, about 131 miles northwest. 1 of the 6 closest counties land in the same band; the ground changes quickly around here.

Kankakee County, IL 22 mi south · 6% at surface
Grundy County, IL 24 mi southwest · 0% at surface
Kendall County, IL 25 mi northwest · 2% at surface
DuPage County, IL 28 mi north · 0% at surface
Lake County, IN 31 mi east · 0% at surface
Cook County, IL 35 mi northeast · under 1% at surface

What Will County is built on

The largest mapped soluble unit here is the Silurian (dolostone (dolomite)), Silurian in age, covering about 88% of the county.

Against the rest of Illinois

Will County ranks 18 of 102 in Illinois for soluble rock at the surface, and sits above 59% of US counties on that measure.