Sinkhole risk in Ottawa County, OK: Sinkhole country

Sinkhole country

Soluble rock at or near the surface across much of the county.

On soluble rock: 63%
At or near the surface: 63%
Buried under cover: 0%

The next step for one property

Get a sinkhole or geotechnical inspection before buying, building or adding weight to a foundation.

That works out to roughly 296 of Ottawa County's 471 square miles on soluble rock, 296 of them with the rock at or near the surface. With about 30,404 residents (65 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 364 map points about 1.1 miles apart, so a pocket smaller than that can be missed or overstated.

Two things to read before deciding: the signs to look for and how an inspection works, and how these percentages are measured.

Counties around Ottawa County

The closest county with no soluble rock mapped is Crawford County, AR, about 92 miles south. 4 of the 6 closest counties land in the same band, so this is a regional pattern rather than a local quirk.

Craig County, OK 23 mi west · 31% at surface
Cherokee County, KS 23 mi north · 6% at surface
Newton County, MO 26 mi east · 99% at surface
McDonald County, MO 29 mi southeast · 100% at surface
Delaware County, OK 31 mi south · 94% at surface
Jasper County, MO 36 mi northeast · 85% at surface

Which formation it is

The largest mapped soluble unit here is the Keokuk and Reeds Spring Formations and St. Joe Group (chert), Early Mississippian in age, covering about 43% of the county. Next is the Pitkin + Fayetteville + Batesville + Hindsville + Moorefield Formations at 20%.

Against the rest of Oklahoma

Ottawa County ranks 7 of 77 in Oklahoma for soluble rock at the surface, and sits above 91% of US counties on that measure.