Sinkhole risk in San Juan County, CO: Mostly deep or small

Mostly deep or small

Some soluble rock, mostly deeply buried or in a small share of the county.

On soluble rock: 1%
At or near the surface: 1%
Buried under cover: 0%

What this means before you buy

Sinkholes are uncommon here; watch for new depressions after heavy rain or leaking pipes.

That works out to roughly 5 of San Juan County's 388 square miles on soluble rock, 5 of them with the rock at or near the surface. With about 821 residents (2 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 247 map points about 1.3 miles apart, so a pocket smaller than that can be missed or overstated.

Worth reading for this county: how these percentages are measured, and the warning signs that apply anywhere.

Counties around San Juan County

The nearest county rated sinkhole country is Emery County, UT, about 186 miles northwest. 1 of the 6 closest counties land in the same band; the ground changes quickly around here.

Hinsdale County, CO 16 mi east · under 1% at surface
Ouray County, CO 27 mi north · under 1% at surface
La Plata County, CO 35 mi south · 2% at surface
Mineral County, CO 40 mi southeast · 0% at surface
San Miguel County, CO 44 mi west · under 1% at surface
Dolores County, CO 46 mi west · 0% at surface

Which formation it is

The largest mapped soluble unit here is the Leadville, Gilman, Dyer, Parting, and Sawatch Fms in west-central and south-central. Leadville Limestone, Ouray Limestone, Elbert Fm, and Ignacio Quartzite in far southwest (limestone), Mississipian-Cambrian in age, covering about 1% of the county.

Against the rest of Colorado

San Juan County ranks 30 of 64 in Colorado for soluble rock at the surface, and sits above 56% of US counties on that measure.