Sinkhole risk in Washington County, OK: 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: 9%
At or near the surface: 9%
Buried under cover: 0%

What to do about a house in Washington County

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

That works out to roughly 37 of Washington County's 416 square miles on soluble rock, 37 of them with the rock at or near the surface. With about 54,060 residents (130 per square mile), homes are spread across towns and farmland, and a mapped unit may or may not reach the developed parts. The figures come from 365 map points about 1.1 miles apart, so a pocket smaller than that can be missed or overstated.

Counties around Washington County

The nearest county rated sinkhole country is Montgomery County, KS, about 35 miles north, close enough that the same rock may run under the county line. 1 of the 6 closest counties land in the same band; the ground changes quickly around here.

Nowata County, OK 17 mi east · 34% at surface
Rogers County, OK 28 mi southeast · 14% at surface
Osage County, OK 28 mi west · 39% at surface
Montgomery County, KS 35 mi north · 72% at surface
Chautauqua County, KS 36 mi northwest · 38% at surface
Craig County, OK 39 mi east · 31% at surface

Which formation it is

The largest mapped soluble unit here is the Dewey Formation or Dewey Limestone (limestone), Middle Pennsylvanian in age, covering about 7% of the county. Next is the Hogshooter Formation at 2%.

Against the rest of Oklahoma

Washington County ranks 49 of 77 in Oklahoma for soluble rock at the surface, and sits above 67% of US counties on that measure.