By Bruce Nichols
HOUSTON (Reuters) - Failure to follow test procedures last June may have caused a CHEVRON (CVX.NY)oil pipeline leak in Utah on December 1, the U.S. pipeline safety agency said Wednesday.
The U.S. Pipeline and Hazardous Materials Safety Administration said water may have been left in the line after a pressure test and that oversight may have led to freeze damage during recent cold weather.
A Chevron spokesman said he could not comment because he had not yet seen the order.
The 10-inch diameter line, which brings crude from Rangely, Colorado, to Chevron's Salt Lake City refinery, was shut down after the leak was discovered and remains shut.
Chevron Pipe Line Co has increased the estimate of the spill on the University of Utah campus in Salt Lake City from 100 barrels to 500 barrels, the agency said.
Chevron has said there has been no effect on the operations of the refinery or the Rangely oilfield, which are relying on storage during the shutdown.
The June 20 pressure test involved injection of water in the line to check it after repair of a leak that occurred last June about 500 feet from the latest leak.
PHMSA said in a corrective action order Wednesday that the manufacturer of the valve involved in the leak required that all water be removed and antifreeze be injected.
The agency ordered Chevron to remove all fluids from line segments involved in the pressure test and to inspect all affected parts to assure no lingering effects.
The line will not be restarted until the agency is satisfied that Chevron has appropriate monitors and procedures in place to detect leaks, the order said.
(Editing by Bernard Orr)