Sinkhole risk in Hill County, TX: Pockets of it

Pockets of it

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

On soluble rock: 22%
At or near the surface: 22%
Buried under cover: 0%

The next step for one property

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 210 of Hill County's 959 square miles on soluble rock, 210 of them with the rock at or near the surface. With about 38,771 residents (40 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 590 map points about 1.3 miles apart, so a pocket smaller than that can be missed or overstated.

Counties around Hill County

The nearest county rated sinkhole country is Taylor County, TX, about 163 miles west. 5 of the 6 closest counties land in the same band, so this is a regional pattern rather than a local quirk.

McLennan County, TX 30 mi south · 41% at surface
Bosque County, TX 30 mi west · 26% at surface
Johnson County, TX 31 mi northwest · 18% at surface
Ellis County, TX 32 mi northeast · 33% at surface
Navarro County, TX 39 mi east · 0% at surface
Somervell County, TX 41 mi northwest · 35% at surface

What Hill County is built on

The largest mapped soluble unit here is the Austin Chalk (limestone), Late Cretaceous; Gulfian Series in age, covering about 13% of the county. Next is the Grayson Marl and Main Street Limestone, undivided at 9%.

The county also lies over the Gulf Coast salt domes, 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 Texas

Hill County ranks 99 of 254 in Texas for soluble rock at the surface, and sits above 76% of US counties on that measure.