Sinkhole risk in Harford County, MD: No soluble rock mapped

The next step for one property

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 2 of Harford County's 437 square miles on soluble rock, 2 of them with the rock at or near the surface. With about 265,514 residents (607 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 552 map points about 0.9 miles apart, so a pocket smaller than that can be missed or overstated.

Two things to read before deciding: how these percentages are measured, and the warning signs that apply anywhere.

Counties around Harford County

The nearest county rated sinkhole country is Washington County, MD, about 81 miles west. 3 of the 6 closest counties land in the same band; the ground changes quickly around here.

• Baltimore County, MD 18 mi west · 8% at surface
• Cecil County, MD 19 mi east · 0% at surface
• Kent County, MD 22 mi southeast · under 1% at surface
• Baltimore city, MD 23 mi southwest · 0% at surface
• Lancaster County, PA 35 mi north · 46% at surface
• York County, PA 35 mi northwest · 10% at surface

The rock underneath

The largest mapped soluble unit here is the Cockeysville Marble (marble), Late Precambrian (?) in age, covering about under 1% of the county.

Against the rest of Maryland

Harford County ranks 16 of 24 in Maryland for soluble rock at the surface, and sits above 52% of US counties on that measure.

• Washington County 61%
• Calvert County 47%
• Allegany County 24%
• Prince George's County 22%
• Anne Arundel County 15%