Sinkhole risk in Lee County, FL: Sinkhole country

Sinkhole country

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

On soluble rock: 72%
At or near the surface: 69%
Buried under cover: 3%

What to do about a house in Lee County

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 562 of Lee County's 781 square miles on soluble rock, 541 of them with the rock at or near the surface. With about 860,959 residents (1,102 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 306 map points about 1.6 miles apart, so a pocket smaller than that can be missed or overstated.

Counties around Lee County

The closest county with no soluble rock mapped is Gulf County, FL, about 303 miles northwest. 6 of the 6 closest counties land in the same band, so this is a regional pattern rather than a local quirk.

Charlotte County, FL 24 mi north · 81% at surface
DeSoto County, FL 45 mi north · 73% at surface
Collier County, FL 47 mi southeast · 89% at surface
Hendry County, FL 51 mi east · 91% at surface
Sarasota County, FL 53 mi northwest · 83% at surface
Glades County, FL 56 mi northeast · 69% at surface

The rock underneath

The largest mapped soluble unit here is the Shelly sediments of Plio-Pleistocene age (limestone), Pliocene/Pleistocene in age, covering about 54% of the county. Next is the Tamiami Formation at 15%.

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

Lee County ranks 16 of 67 in Florida for soluble rock at the surface, and sits above 92% of US counties on that measure.