Natural gas transmission pipeline integrity management (IM) programs required by the Pipeline and Hazardous Materials Safety Administration (PHMSA) since 2004 have kept the rate of corrosion failures and material failures of pipe and welds low, but there is no evidence that the overall occurrence of pipeline incidents in "high consequence areas" has declined, according to a report adopted Tuesday by the National Transportation Safety Board (NTSB).
In fact, incidents in those more densely populated areas attributed to causes other than corrosion and material defects in pipe or weld increased from 2010 to 2013, according to the report. And gas transmission pipeline incidents associated with corrosion failure continue to disproportionately occur on pipelines installed before 1970.
Researchers concluded that the complexity of IM programs may make their development and evaluation of operators' compliance difficult. PHMSA's resources in guiding operators and inspectors needs to be expanded and improved, NTSB said.
The study found that aspects of operators' threat identification and risk assessment processes require improvement. Of the four integrity assessment methods -- pressure test, direct assessment, in-line inspection (ILI) and other techniques -- "ILI yields the highest per-mile discovery of pipe anomalies and the use of direct assessment as the sole integrity assessment method has numerous limitations."
The report includes more than two dozen recommendations to the PHMSA, American Gas Association, Interstate National Gas Association of America, National Association of Pipeline Safety representatives and U.S. Department of Transportation. Recommendations include closer state-to-state and federal-state cooperation among inspectors, and a call for expanded and improved resources and guidance at the federal level, including improvements to the National Pipeline Mapping System and better integration of geographic information system technology.
NTSB analyzed information from PHMSA's data systems, federal and state pipeline inspectors, transmission pipeline operators, industry associations, and pipeline and safety engineering support organizations. The study also reviewed recent NTSB accident investigations.
In the last five years NTSB has investigated three major transmission pipeline accidents "where deficiencies with the operators' IM programs and PHMSA oversight were identified as a concern," the agency said. Those incidents occurred in Palm City, FL, in 2009; San Bruno, CA, in 2010 (see Daily GPI, Sept. 13, 2010); and Sissonville, WV, in 2012 (see Daily GPI, Dec. 13, 2012).