Engineers are scrambling to figure out why a 100-foot-long, 20-foot-deep sinkhole opened up on 10th Street in downtown Pittsburgh on October 29, according to TribLive. City officials say it could take a while to determine the cause and noted the city’s advanced age.
“We’re building on top of 250 years of development, and there are vaults all throughout not only downtown, but throughout Western Pennsylvania, when it comes to mining and other types of things that were never reported 100 years ago, let alone 200 years ago,” said Mayor Bill Peduto, according to the news agency. “There’s a lot of surprises underground.
Mayor Peduto said they need to find the answers to two main questions: Why and how did the sinkhole happen, and how does the city make sure the road is stable in the future? City spokesman Tim McNulty said that after debris is removed and fiber-optic cables below ground are safe, utility companies will assess the damage to water, gas, and electric lines.
Simeon Suter, a geologist supervisor with the Pennsylvania Geological Survey, noted that underground utility lines can cause sinkholes. “Anytime there is a mass of material taken out of the ground, there will be some subsidence — even if it’s just an inch,” he said. “There are a lot of things we put underground — water lines, sewer lines, cable lines, electric lines. When we excavate and put those lines in and backfill, some settlement takes place. Now what you have under the street is not as compacted as soil.”
According to the news agency, Julie Vandenbossche, an assistant professor of geotechnical and pavements engineering at the University of Pittsburgh’s Swanson School of Engineering, said the issues are finding better solutions to repair and renew the infrastructure that already exists.“The aging infrastructure is not on our side,” she said. “The needs aren’t increasing linearly, but exponentially.”