Sinkhole risk in Union 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 Union 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 12 of Union County's 2,037 square miles on soluble rock, 12 of them with the rock at or near the surface. With about 26,058 residents (13 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 481 map points about 2.1 miles apart, so a pocket smaller than that can be missed or overstated.

Counties around Union County

The nearest county rated sinkhole country is Emery County, UT, about 572 miles southeast. 3 of the 6 closest counties land in the same band; the ground changes quickly around here.

Umatilla County, OR 41 mi northwest · under 1% at surface
Baker County, OR 44 mi south · 14% at surface
Wallowa County, OR 44 mi northeast · 2% at surface
Columbia County, WA 68 mi north · 0% at surface
Walla Walla County, WA 70 mi north · 0% at surface
Asotin County, WA 71 mi northeast · 0% at surface

What Union County is built on

The largest mapped soluble unit here is the Sedimentary rocks (Jurassic and Upper Triassic) (mudstone), Triassic to Jurassic in age, covering about under 1% of the county. Next is the Marine sedimentary rocks (Upper Triassic? and Upper and Middle Triassic) at under 1%.

Against the rest of Oregon

Union County ranks 10 of 36 in Oregon for soluble rock at the surface, and sits above 53% of US counties on that measure.