Sinkhole risk in Lewis County, WA: Not karst, but voids possible

Not karst, but voids possible

No soluble bedrock; some pseudokarst (piping or lava-tube ground).

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

What this means before you buy

Not true karst, but soil piping or lava tubes can still open voids - mention it to an inspector.

Across 2,403 square miles, under one square mile of Lewis County maps onto soluble rock. With about 87,049 residents (36 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 358 map points about 2.6 miles apart, so a pocket smaller than that can be missed or overstated.

Two things to read before deciding: how ground with no limestone still opens up, and how these percentages are measured.

Counties around Lewis County

The nearest county rated sinkhole country is Emery County, UT, about 788 miles southeast. 3 of the 6 closest counties land in the same band; the ground changes quickly around here.

Cowlitz County, WA 30 mi southwest · 0% at surface
Thurston County, WA 33 mi northwest · 0% at surface
Pierce County, WA 34 mi north · 0% at surface
Skamania County, WA 43 mi southeast · 0% at surface
Wahkiakum County, WA 54 mi west · 0% at surface
Columbia County, OR 55 mi southwest · 0% at surface

Against the rest of Washington

Lewis County ranks 27 of 39 in Washington for soluble rock at the surface, and sits above 0% of US counties on that measure.