SinkholeOdds

Sinkhole risk in Pierce 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 to do about a house in Pierce County

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

Across 1,668 square miles, under one square mile of Pierce County maps onto soluble rock. With about 941,170 residents (564 per square mile), most of the county is built up, so a mapped unit is likely to sit under somebody's street. The figures come from 574 map points about 1.7 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 Pierce County

The nearest county rated sinkhole country is Emery County, UT, about 800 miles southeast. 2 of the 6 closest counties land in the same band; the ground changes quickly around here.

Against the rest of Washington

Pierce County ranks 31 of 39 in Washington for soluble rock at the surface, and sits above 0% of US counties on that measure.