SinkholeOdds

Sinkhole risk in St. Lucie County, FL: Sinkhole country

Sinkhole country

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

On soluble rock
91%
At or near the surface
83%
Buried under cover
8%

What this means before you buy

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

Standard Florida homeowners policies cover only catastrophic ground cover collapse; full sinkhole coverage is a separately priced option insurers must offer.

That works out to roughly 520 of St. Lucie County's 572 square miles on soluble rock, 476 of them with the rock at or near the surface. With about 390,670 residents (683 per square mile), there is effectively nowhere in the county off the soluble rock, town or country. The figures come from 342 map points about 1.3 miles apart, so a pocket smaller than that can be missed or overstated.

Two things to read before deciding: what Florida insurers have to cover, and why gypsum and salt move faster than limestone.

Counties around St. Lucie County

The closest county with no soluble rock mapped is Gulf County, FL, about 339 miles northwest. 4 of the 6 closest counties land in the same band, so this is a regional pattern rather than a local quirk.

What St. Lucie County is built on

The largest mapped soluble unit here is the Anastasia Formation (calcarenite), Pleistocene in age, covering about 52% of the county. Next is the Shelly sediments of Plio-Pleistocene age at 31%.

The county also lies over the Floridan shelf, a deep salt or gypsum basin. Deep beds rarely cause surface collapse on their own, but wells and mining into them have.

Against the rest of Florida

St. Lucie County ranks 10 of 67 in Florida for soluble rock at the surface, and sits above 95% of US counties on that measure.