Route 202 has another sinkhole. Why does this keep happening in King of Prussia?

Another sinkhole has cracked its way into Dekalb Pike in a heavily trafficked area not far from the King of Prussia Mall and other retail areas at the crest of the holiday-shopping season. A section of Route 202 is now closed for the second time in six months for sinkhole-related repairs.

“It’s the time of the year when a lot of people come to get their haircuts … some of our customers have been late for their appointments and that makes us late for other appointments,” said Salvatore Giannone, 38, owner of Sal’s Barbershop. Giannone said that, at first, he thought the latest round of road work was part of the process of repairing July’s sinkhole.

“It’s scary to think that our roads aren’t safe,” he said, adding that he hoped the process isn’t rushed, “so that we don’t have to keep having this problem.”

Less than a mile away at Marian’s Attic, a thrift store that helps fund Laurel House’s domestic violence programs, sales associate Sarah Polwort said she also was concerned about the sinkhole situation.

But she added that she trusted that the roadwork would resolve the problem.

In the meantime, traffic is being diverted to Henderson Road and Saulin Boulevard, and that has helped Marian’s Attic weather the disruption, she said.

“We are not really feeling it much,” said Polwort. “We put out a sale and there have been quite a lot of people,” she added, noting they had at least 30 customers before noon.

It was unclear how Sunday’s forecast for heavy rains would affect repairs. “It’s not ideal,” said PennDot spokesperson Brad Rudolph, “but we’ll be out there.” PennDot announced late Saturday night that one of the northbound lanes had reopened, but no timetable has been set for opening the other northbound lane or the southbound lanes.

So, why are sinkholes so prone to happen in King of Prussia, and just what is a sinkhole?

Also referred to as voids, sinkholes are underground cavities typically caused by water erosion. They are common in areas that have bedrock composed of materials that can be dissolved by groundwater, such as limestone.

“Once it breaks down, it causes a void,” said Rudolph. “Eventually, those voids collapse when something heavy gets on it.”

Typically, moisture from sources such as rain or groundwater gets to the bedrock, and, lacking surface drainage, breaks it down over time. The area impacted can often appear undamaged on its surface for long periods of time, but collapses suddenly as the void grows bigger, according to the U.S. Geological survey.

They are different from potholes, which are a result of an issue with a road’s paving material. Often, those come about due to the freezing and thawing of water, and aren’t usually as disruptive as a sinkhole.

The King of Prussia area sits atop what geologists refer to as “karst,” or a landscape of limestone. As a result, it’s susceptible to sinkholes, as that limestone bedrock is easily damaged by water.

But with this area of 202 specifically, it’s not just the bedrock itself.

“It won’t collapse on its own,” Rudolph said. “It needs to be eroded with water.”

So, for that stretch of road, there is water infiltrating to the bedrock somewhere. Crews are working to determine where that is and to seal it up to limit future issues. But so far, the source hasn’t been identified.

“The geological layout of this area is challenging,” Rudolph said. “They’re looking for any kind of water infiltration to figure out what is going on here.”

The area of 202 that is closed right now had issues in July when a sinkhole opened up following a water main break, causing closures on the roadway. It reopened July 12 following repairs by Pennsylvania American Water, Montgomery County’s water utility provider. That sinkhole was near the latest one, Rudolph said.

“This is the not the fault of anyone at this particular moment,” he added. “They’re looking for any kind of water infiltration to figure out what is going on here.”

Rudolph said that PennDot expects Route 202′s closure in the area to last at least through the weekend as crews continue to search for the source of the water.

“We’re trying to get it open as quickly as possible, but we ran into another void, and public safety is first,” Rudolph said. “We can’t have traffic if we know something is compromised underneath.”

After workers identify the source of the water and stop it from getting under the roadway, the repair process will begin. They will pump material known as flowable fill to reinforce the void under the roadway.

That will take about 24 hours to settle, and during that time, crews will lay down accelerate concrete to level the roadway’s surface, Rudolph said.

But that process is still a ways off. And even once the roadway is reopened, crews will likely need to continue a more formal investigation into the area with tools including ground-penetrating radar to examine it for additional voids.

“We haven’t even started filling yet,” Rudolph said. “We’re still doing underground exploratory stuff.”

Plenty of them.

Most recently, in July, a large sinkhole opened up near 57th and Media Streets in West Philadelphia, causing road closures on the 1400 block of North 57th Street.

More notably, in 2019, a sinkhole at 43rd and Baltimore inspired ritual offerings from neighborhood residents, who gifted it with feathers, flowers, and candy as if it were a deity. That one was caused by a 20-by-20-foot chasm under the pavement that had been created by a sewage line leak.

That area has long experienced cave-ins and sinkholes, which are often attributed to the Mill Creek sewer — likely as far back as the 19th century. And in 1952, a sinkhole opened at 43rd and Sansom Streets that ran the width of the street. It swallowed a car and a pickup truck, and as rain moved into the area, residents’ front porches collapsed and about 300 people were evacuated, according to West Philadelphia Collaborative History.

And in 1961, an issue with the Mill Creek sewer caused the collapse of several houses, killing four people, including a 9-year-old boy. Homes of an additional 100 families were condemned, according to an Inquirer report.

The city reinforced the area around the sewer in the 1960s, reducing the chances of housing collapses, according to West Philadelphia Collaborative History.