Sinkhole risk in Routt County, CO: No soluble rock mapped

What this means before you buy

No soluble bedrock is mapped here, so natural sinkholes are unlikely. Collapses from broken pipes or old mines are a separate risk.

That works out to roughly 17 of Routt County's 2,362 square miles on soluble rock, 17 of them with the rock at or near the surface. With about 25,243 residents (11 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 288 map points about 2.9 miles apart, so a pocket smaller than that can be missed or overstated.

Two things to read before deciding: why gypsum and salt move faster than limestone, and how these percentages are measured.

Counties around Routt County

The nearest county rated sinkhole country is Emery County, UT, about 223 miles southwest. None of the 6 closest counties land in the same band, so Routt County stands out from its surroundings.

• Jackson County, CO 37 mi east · 4% at surface
• Grand County, CO 53 mi southeast · 6% at surface
• Eagle County, CO 61 mi south · 22% at surface
• Moffat County, CO 65 mi west · 8% at surface
• Rio Blanco County, CO 73 mi southwest · 1% at surface
• Summit County, CO 75 mi southeast · 4% at surface

The rock underneath

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 under 1% of the county.

The county also lies over the Eagle Valley Basin, 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 Colorado

Routt County ranks 35 of 64 in Colorado for soluble rock at the surface, and sits above 54% of US counties on that measure.

• Pueblo County 45%
• Bent County 44%
• Otero County 42%
• Prowers County 35%
• Kiowa County 30%