PHMSA chief: Silvertip oil line surpassed burial rules

Nick Snow
OGJ Washington Editor

WASHINGTON, DC, July 14 -- ExxonMobil Pipeline Co. (Empco) exceeded burial requirements for its Silvertip crude oil pipeline in Montana before it ruptured on July 1 and leaked 1,000 bbl into the Yellowstone River, the director of the US Pipeline and Hazardous Materials Safety Administration told a US House Transportation and Infrastructure subcommittee.

PHMSA requires at least 4 ft of cover when a pipeline crosses a river that is 100 ft wide, Cynthia L. Quarterman said during a July 14 Railroads, Pipelines, and Hazardous Materials Subcommittee hearing on the pipeline rupture and leak near Laurel, Mont. When ExxonMobil performed a depth-of-cover (DOC) survey in December 2010, it found 5 ft of cover in the riverbed and 12 ft of cover on the crossing’s south side, she said.

Empco performed the survey after PHMSA and the city of Laurel jointly reviewed rising river flow and erosion near the river’s south bank and expressed concern, Quarterman said. When flooding became heavy the following May, she said PHMSA inspectors began monitoring the river’s flow rates daily and visually observed the pipeline’s crossing biweekly. Empco confirmed there was at least 12 ft of cover on the bank in June after PHMSA asked for another DOC inspection, she said.

She said PHMSA also alerted pipeline operators along the upper Missouri River and its tributaries of risks from high runoff in early June and urged them to take appropriate actions.

The US Department of Transportation agency has routinely inspected the pipeline for years, according to Quarterman. “As recently as June 6-10, 2011, PHMSA personnel performed an integrity management field inspection on the Silvertip pipeline,” she said. It reviewed Empco’s 2009 internal inspection data for the line and found no violations. It did find, however, an anomaly at the river crossing that was below required repair conditions under federal pipeline safety regulations, she said.

August retrieval
PHMSA will investigate the matter thoroughly and not allow Empco to restart the pipeline until it is clear that it is free of safety and environmental risks, Quarterman pledged. She said that water in the river could subside to a point where the ruptured section can be retrieved sometime in August. “ExxonMobil will be responsible for exposing the pipeline, and we will be there to take custody of it once it comes from the water,” she told the subcommittee. Finding the rupture’s cause could take several months, Quarterman added.

Empco Pres. Gary W. Pruessing said the ExxonMobil Corp. subsidiary is committed to using horizontal drilling to replace the damaged section of pipe, consistent with PHMSA’s June 6 corrective action order, with a new pipe section that will be placed 30 ft below the riverbed. “Drilling will not be in rubble or sediment, but in rock,” he indicated. “As we go to a depth of 30 ft below the riverbed, we’ll have to dig farther bank from the bank so we don’t have too steep a slope. That will require moving some of the valves back.”

The company tried to respond quickly once it realized that a rupture had occurred, he told the subcommittee. “Of paramount concern to us is the impact on local communities,” Pruessing said. “We established a community information line and have received more than 300 calls. A number of these calls are related to property, agriculture, and health, and we are actively responding to more than 120 of them.”

Empco also continues to work with the incident response’s unified command, which the US Environmental Protection Agency is leading, monitoring air and water quality along a 200-mile stretch of the river, he continued. “To date, it confirms there is no danger to public health, and no reported water system impacts,” he testified. Empco also brought in several experts to monitor local wildlife impacts.

Two members of Montana’s congressional delegation separately pledged to hold Empco accountable for the rupture and leak. “This spill was a failure that did not live up to our standards,” said Rep. Dennis Rehberg, its at-large House member and a Republican. “I want to know why, and how we can keep it from happening again.”

US Sen. Jon Tester, a Democrat, said that it’s imperative to fully determine what happened before, during, and after the incident. “It’s just as important we build a culture committed to safety, transparency, and accountability,” he said.

Contact Nick Snow at nicks@pennwell.com.

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