Philadelphia Gas Works Co. crews unearthed a damaged cast iron natural gas line near the site of a deadly explosion in South Philadelphia, according to the Pennsylvania Public Service Commission.
Investigators from the Safety Division of the Pennsylvania Public Service Commission, or PUC, identified a crack in a six-inch cast iron gas main, one of two Philadelphia Gas Works lines that run beneath the street directly in front of buildings damaged in the Dec. 19, 2019, blast. The investigators also collected information about recent water and wastewater work completed in the area, the PUC said in a preliminary report released Jan. 16.
PUC pipeline safety engineers will continue to investigate the explosion, and it could take a year or more for staff to reach a conclusion about its cause, according to the report. The blast caused two deaths and severe damage to several buildings on the 1400 block of South 8th Street.
"The investigation by the Safety Division is active and ongoing, exploring the cause and circumstances surrounding this incident, along with whether there are any violations of state or federal pipeline safety regulations," the PUC said.
The PUC interviewed gas company employees and other parties following the blast, observed the collection of evidence including gas mains, and investigated other nearby facilities. The commission noted that it has no jurisdiction over municipal water and wastewater services operated by the Philadelphia Water Department.
Work on water and wastewater infrastructure on the affected block wrapped up Dec. 6, 2019, according to The Philadelphia Inquirer. Damage during excavation work is one of the most common causes of significant pipeline incidents, accounting for nearly 19% of the total in 2018, according to the U.S. Pipeline and Hazardous Materials Safety Administration.
Philadelphia Gas Works' backlog of leak-prone cast iron and bare steel lines has long been a concern for the city of Philadelphia, which owns the utility. The company had the second-highest ratio of distribution main and service line leak repairs in S&P Global Market Intelligence's latest annual review.