Its status as one of the richest townships in the region has not helped Upper Merion resolve its underlying problem of a proliferation of sinkholes, writes Grace Toohey for the Philadelphia Inquirer.

The home of the massive King of Prussia Mall has seen 35 cave-ins since the Mall’s expansion started two years ago.

“That’s the thing about sinkholes – you don’t know where or when they are going to appear, and you don’t know the size,” said Robert Cottone, president and CEO of IMC Construction.

The problem is that King of Prussia sits on what geologists call karst, which is ground made up of dissolvable limestone prone to sinkholes. Experts think that more development could exacerbate the issue, but they cannot say for sure.

This answer is of no comfort to real estate developer JBG. It is working on a $100-million, 125-acre outdoor shopping and restaurant venue with mixed residences less than a mile from the mall, on land designated as highly probable for sinkholes.

“Don’t assume that all limestone is going to have a sinkhole. It doesn’t,” said geologist Laura Toran of Temple University’s Department of Earth and Environmental Science. “To not build on that rock type would wipe out too much land.”

Read more about the sinkholes in the Philadelphia Inquirer by clicking here.