Sinkhole risk in New Castle County, DE: No soluble rock mapped

What to do about a house in New Castle County

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 3 of New Castle County's 426 square miles on soluble rock, 3 of them with the rock at or near the surface. With about 588,093 residents (1,379 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 257 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 New Castle County

The nearest county rated sinkhole country is Washington County, MD, about 116 miles west. 3 of the 6 closest counties land in the same band; the ground changes quickly around here.

• Salem County, NJ 15 mi east · 15% at surface
• Cecil County, MD 16 mi west · 0% at surface
• Delaware County, PA 27 mi northeast · 0% at surface
• Chester County, PA 28 mi north · 7% at surface
• Gloucester County, NJ 28 mi east · 9% at surface
• Cumberland County, NJ 33 mi southeast · 0% at surface

Which formation it is

The largest mapped soluble unit here is the Cockeysville Marble (limestone), Paleozoic in age, covering about under 1% of the county. Next is the Vincentown Formation at under 1%.

Against the rest of Delaware

New Castle County ranks 1 of 3 in Delaware for soluble rock at the surface, and sits above 54% of US counties on that measure.

• Kent County 0%
• Sussex County 0%