Summary: The Department of Transportation is responsible for ensuring the safety of about 267,000 miles of interstate natural gas pipelines. The use of an instrumented internal inspection device known as a "smart pig" is the only way to detect internal and external corrosion without excavating the pipe. Pipeline corrosion is the second leading cause of pipeline accidents after accidental excavation damage. Smart pigs can also spot other flaws, such as gouges and dents, that weaken a pipe's structural integrity. Smart pigs have their limits, however. They cannot detect defects like longitudinal cracks and metal loss in pipe welds, and some pipelines with sharp bends and other configurations cannot accommodate smart pigs. Even so, this technology has the potential to greatly reduce pipeline accidents. No federal regulations governing smart pigs or the frequency of smart pig inspections are on the books. Because corrosion can lead to ruptures and leakages in aging pipelines--problems that smart pigs can avert--GAO urges DOT to complete the feasibility study and regulations mandated under the law.
