The leading cause of accidents in both transmission and distribution systems is damage by digging near existing pipeline. Frequently, this damage results from someone excavating without asking or without waiting the standard 48-hours for the gas company to mark the location of its lines. Excavation damage accounted for almost 60 percent of all reported distribution pipeline incidents between 1995 and 2004, according to statistics kept by the U.S. Department of Transportation’s Office of Pipeline Safety. Other causes include corrosion, a fire or explosion causing a pipeline incident, or even a vehicle striking an aboveground meter or regulator. Corrosion sometimes results from excavation damage, which, while not severe enough to trigger a puncture or failure of the pipeline, could create weaknesses in the pipeline that later render it more susceptible to corrosion.
In 2004, the most recent year with pipeline statistics available, one-third (95) of the 288 total incidents along the entire natural gas delivery system were caused by excavation damage. (Note: The U.S. Department of Transportation classifies excavation damage as “damage by outside force,” “third party excavation damage,” and “operator excavation damage.”) A closer look at the statistics shows the percentages are even higher on the distribution part of the delivery system. On the distribution part of the system, which includes the pipelines that spread out from the city gate and travel through more densely populated areas to reach the customer, fully 42 percent (71) of pipeline incidents in 2004 were caused by excavation damage.
According to DOT statistics, the other leading causes of natural gas distribution pipeline incidents in 2004 included a fire or explosion that caused a natural gas incident (26 incidents) and a vehicle striking above-ground facilities (12 incidents). There were 3 incidents related to corrosion on distribution lines. See the accompanying graphic below, “Causes of Pipeline Incidents.”
In view of the enormity of the delivery system’s 2.4 million miles of pipeline, which serve 70 million homes, businesses, factories and power plants daily, pipeline incidents are rare. But the natural gas industry strives for “extinct,” and it is dedicated to improving and perfecting the system. For more information on natural gas company pipeline safety programs, see the related Natural Gas Industry Safety Programs.
Most Incidents on Natural Gas Distribution Pipelines
Caused by Excavation Damage/Outside Force