Sinkhole risk in Umatilla County, OR: No soluble rock mapped

No soluble rock mapped

No soluble bedrock mapped.

On soluble rock: under 1%
At or near the surface: under 1%
Buried under cover: 0%

What to do about a house in Umatilla County

No soluble bedrock is mapped here, so natural sinkholes are unlikely. Collapses from broken pipes or old mines are a separate risk.

That works out to roughly 13 of Umatilla County's 3,215 square miles on soluble rock, 13 of them with the rock at or near the surface. With about 80,491 residents (25 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 268 map points about 3.5 miles apart, so a pocket smaller than that can be missed or overstated.

Two things to read before deciding: how these percentages are measured, and the warning signs that apply anywhere.

Counties around Umatilla County

The nearest county rated sinkhole country is Emery County, UT, about 611 miles southeast. 6 of the 6 closest counties land in the same band, so this is a regional pattern rather than a local quirk.

Union County, OR 41 mi southeast · under 1% at surface
Morrow County, OR 44 mi west · 0% at surface
Walla Walla County, WA 47 mi north · 0% at surface
Benton County, WA 58 mi northwest · 0% at surface
Columbia County, WA 63 mi northeast · 0% at surface
Franklin County, WA 66 mi north · 0% at surface

What Umatilla County is built on

The largest mapped soluble unit here is the Landslide and debris-flow deposits (Holocene and Pleistocene) (landslide), Pleistocene to Holocene in age, covering about under 1% of the county.

Against the rest of Oregon

Umatilla County ranks 11 of 36 in Oregon for soluble rock at the surface, and sits above 52% of US counties on that measure.