Sinkhole risk in Berks County, PA: Pockets of it

Pockets of it

Soluble rock at the surface or under thin cover in part of the county.

On soluble rock: 22%
At or near the surface: 22%
Buried under cover: 0%

The next step for one property

Check the parcel against your state survey sinkhole map, and ask for an inspection if cracks, depressions or sticking doors show up.

That works out to roughly 189 of Berks County's 856 square miles on soluble rock, 189 of them with the rock at or near the surface. With about 439,117 residents (513 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 489 map points about 1.3 miles apart, so a pocket smaller than that can be missed or overstated.

Two things to read before deciding: the signs to look for and how an inspection works, and how these percentages are measured.

Counties around Berks County

The nearest county rated sinkhole country is Union County, PA, about 70 miles northwest. 3 of the 6 closest counties land in the same band; the ground changes quickly around here.

Lehigh County, PA 22 mi northeast · 29% at surface
Schuylkill County, PA 25 mi northwest · 2% at surface
Lebanon County, PA 28 mi west · 31% at surface
Lancaster County, PA 31 mi southwest · 46% at surface
Chester County, PA 32 mi south · 7% at surface
Montgomery County, PA 33 mi southeast · 5% at surface

Which formation it is

The largest mapped soluble unit here is the Allentown Formation (dolostone (dolomite)), Cambrian in age, covering about 5% of the county. Next is the Leithsville Formation at 3%.

Against the rest of Pennsylvania

Berks County ranks 26 of 67 in Pennsylvania for soluble rock at the surface, and sits above 76% of US counties on that measure.