ConocoPhillips planned to reopen a six-mile stretch of the Yellowstone Pipeline along the North Fork of the Coeur d’Alene River late Tuesday, after a series of recent tests confirmed the line’s integrity, a company spokesman said.
The 10-inch line transports unleaded gasoline and diesel fuel between Spokane and Thompson Falls, Mont. Authorities still aren’t sure what caused a gradual drop in pressure in that portion of the line on Oct. 1, said Jeff Callender, a ConocoPhillips spokesman. But he said tests conducted since last Thursday don’t indicate leaks or other problems.
In addition to an acoustic test to listen for problems within the line, ConocoPhillips filled the pipeline with water and conducted pressure tests. One of the tests, required by the federal Department of Transportation, requires keeping the pipeline near its maximum operating pressure and monitoring the line for eight hours, Callender said.
“We’ve gone through all of our own procedures for verifying the integrity of the line, and all the Department of Transportation’s,” he said.
ConocoPhillips will continue to check the Yellowstone Pipeline after it’s restarted, he said.
The drop in pressure in the line may have been caused by a change in outside temperatures, according to Callender, who said the company’s technical staff continues to review the data in search of an explanation.