The National Transportation Safety Board today determined that the probable cause of a large oil spill near a Potomac Electric Power Company (PEPCO) generating station in Chalk Point, Maryland, was a fracture in a wrinkle in the pipeline that was not discovered because data from an in-line inspection device was inaccurately interpreted by PEPCO's inspection contractor. Contributing to the magnitude of the fuel oil release, the Board found, were inadequate procedures for monitoring the flow of oil through the pipeline to ensure timely leak detection.
The Piney Point oil pipeline failed on the morning of April 7, 2000, near the PEPCO generating station in southeastern Prince George's County, Maryland, but the pipe fracture and oil spill were not discovered and addressed until the late afternoon. In the interim, over 140,000 gallons of fuel oil were released into the surrounding marsh, Swanson Creek and, subsequently, the Patuxent River. No injuries were caused by the accident; cost of the environmental response and clean-up operations totaled about $70 million.
The pipeline last had an in-line ultrasonic inspection in August 1997, under a periodic program designed to help ensure pipeline integrity. But because the data from that inspection indicating a possible wrinkle in the line was misinterpreted as a T-shaped pipe connection, PEPCO was not alerted to the need to further examine the pipeline at the location where it subsequently ruptured.
The rupture occurred at a wrinkle in a section of pipe that had been installed during construction of the pipeline in 1971-2. Longstanding regulations prohibit the use of pipe containing bends with wrinkles in new pipeline construction. However, pipe wrinkles that were not discovered during the construction phase or that formed sometime after installation are still found periodically in pipelines. The Board, noting that pipeline operators do not have nationally-recognized criteria for determining whether pipe containing wrinkles should be allowed to remain in service, recommended that the regulatory authority, the Research and Special Programs Administration (RSPA) of the U.S. Department of Transportation, establish such criteria based on engineering evaluations.
The Board determined that the fuel leak might have been discovered much sooner if more systematic detection procedures had been followed. Subsequent to the accident, monitoring of the Piney Point pipeline has been improved and RSPA has issued a new regulation requiring operators to have a "means to detect" leaks. The NTSB supports these efforts and is encouraging RSPA to expedite the development of criteria for defining adequate leak detection measures and to consider increased system automation to ensure prompt leak detection.
The Board noted that PEPCO initially did not provide accurate information to public agencies about the volume of the oil released, which potentially could have hampered the ability to evaluate the threat and respond with sufficient personnel and equipment. The Board recommended that RSPA require pipeline operators to provide timely telephone updates to the authorities when new or significantly different information relating to the volume of the hazardous material spill is obtained.
The Board also made a recommendation to the Environmental Protection Agency to improve the incident command system used to manage the response to a hazardous material spill and the training of personnel that are involved.
A synopsis of the investigation report, including the findings, probable cause and safety recommendations, can be found on the Board's web site at www.ntsb.gov. The complete accident report will be available in about one month.