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Safety Study: Integrity Management of Gas Transmission Pipelines in High Consequence Areas
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 Safety Study: Integrity Management of Gas Transmission Pipelines in High Consequence Areas

Summary

There are approximately 298,000 miles of onshore natural gas transmission pipelines in the United States. Although rare, failure of these pipelines poses a significant risk to the public, especially when pipelines traverse populated areas, known as high consequence areas (HCA). To ensure the physical integrity of their systems in HCAs, gas transmission pipeline operators have been required by the Pipeline and Hazardous Materials Safety Administration (PHMSA) to develop and implement integrity management programs since 2004.
 
The NTSB undertook this study because of concerns about deficiencies in the operators’ integrity management programs and the oversight of these programs by PHMSA and state regulators—concerns that were also identified in three gas transmission pipeline accident investigations conducted by the NTSB in the last five years. These accidents resulted in 8 fatalities and over 50 injuries, and they also destroyed 41 homes. This study used both quantitative and qualitative approaches. Data analysis was combined with insights on industry practices and inspectors’ experiences obtained through interviews and discussions with pipeline operators, state and federal inspectors, industry associations, and other stakeholders.
 
This study found that while the PHMSA’s gas integrity management requirements have kept the rate of corrosion failures and material failures of pipe or welds low, there is no evidence that the overall occurrence of gas transmission pipeline incidents in HCA pipelines has declined. This study identified areas where improvements can be made to further enhance the safety of gas transmission pipelines in HCAs. Areas identified for safety improvements include (1) expanding and improving PHMSA guidance to both operators and inspectors for the development, implementation, and inspection of operators’ integrity management programs; (2) expanding the use of in-line inspection, especially for intrastate pipelines; (3) eliminating the use of direct assessment as the sole integrity assessment method; (4) evaluating the effectiveness of the approved risk assessment approaches; (5) strengthening aspects of inspector training; (6) developing minimum professional qualification criteria for all personnel involved in integrity management programs; and (7) improving data collection and reporting, including geospatial data.
NTSB Number: SS-15-01
NTIS Number: PB2015-102735
Adopted: 1/27/2015