On February 6, 2019, the excavator operator for a third-party contractor, Kilford Engineering Inc., impacted a Pacific Gas & Electric Company (PG&E) branch connection with the mini excavator trenching bucket attachment during mechanical excavation for fiberoptic conduit installation, which resulted in the release and ignition of natural gas. The accident occurred in the Richmond District, a neighborhood in San Francisco, California. A nearby restaurant with a rental unit above caught fire. There were no injuries. Estimated damages to nearby buildings and the pipeline system exceeded $10 million.
The San Francisco Fire Department was dispatched and arrived on scene and focused on containing the fire and minimizing its spread while PG&E crews worked to isolate and shut down the gas pipeline line. The fire department and police department evacuated about 100 persons, and PG&E shut off natural gas service to 328 customers. At 3:36 p.m., the damaged pipelines and branch connection were isolated, and the fire department extinguished the gas fire 2 minutes later.
We determined that the probable cause of the release of natural gas from the Pacific Gas & Electric Company distribution pipeline and the subsequent fire was the failure of the Kilford Engineering Inc. operator and spotter to follow safe excavation practices within the tolerance zone, which resulted in the mini excavator trenching bucket attachment impacting the branch connection.
As a result of the investigation, we made one recommendation each to the San Francisco Police Department, Fire
Department, and Department of Emergency Management and two recommendations to PG&E.
