It is not clear that federal pipeline regulators are effectively prioritizing inspections for the riskiest gas and hazardous liquids pipelines, the U.S. Government Accountability Office said in an Aug. 3 report.
The report, mandated by the 2016 pipeline safety law, looked at the so-called Risk Ranking Index Model, or RRIM, that the U.S. Pipeline and Hazardous Materials Safety Administration uses to rank the relative risk of pipelines and prioritize annual inspections of pipeline operators.
The GAO found that "because PHMSA has not documented the basis for the design and key decisions of RRIM and has not formally evaluated its effectiveness at prioritizing pipelines for inspection, it is unclear how effectively the model has helped PHMSA manage its inspection resources or maximize safety benefits to the public."
From 2010 to 2015, pipeline materials and weld failures and corrosion caused about one-third of significant pipeline incidents, according to the report. Thus, it is important for PHMSA to monitor these factors in its inspections.
PHMSA's RRIM uses pipeline and corrosion data to determine the frequency of inspections based on threats to pipeline integrity, such as ineffective coatings and welding techniques that are susceptible to catastrophic failure, according to the report.
But the GAO found that PHMSA did not document the rationale for the design of its model, including the selection of threat factors and their associated weights. "For example, RRIM's design places a greater relative weight on longer pipeline units, assuming that longer pipeline segments have greater relative risk than shorter units," the report said.
PHMSA also lacks a process to assess and validate the effectiveness of its approach, the GAO said. The agency has made periodic changes to the model, such as adding threat factors and adjusting weights, but PHMSA did not provide any documentation as to why these changes were made, the report noted.
The GAO concluded that without a process that uses data to assess the effectiveness of the model, PHMSA is unable to demonstrate whether the model is effectively prioritizing pipelines for inspection.
The report recommended that PHMSA compare actual performance to planned or expected results in order to assess the validity of the model's threat factors and weighting. "In the context of RRIM, such analysis could compare the characteristics of pipeline segments involved in recent incidents to pipeline segments assigned to each risk tier by RRIM," the report said.
The report concluded that PHMSA should take a few key steps to improve the model. "GAO recommends that PHMSA document the design of its RRIM and implement a process that uses data to periodically assess the model's effectiveness."
The U.S. Department of Transportation concurred with both recommendations, according to a letter the department sent to the GAO. The DOT said it would provide a detailed response to each recommendation within 60 days of the final report's issuance.
Kate Winston is a contributor to S&P Global Platts, which, like S&P Global Market Intelligence, is owned by S&P Global Inc.