Report: Valero refinery fire caused by leak

The U.S. Chemical Safety Board found Valero Energy Corp., which operates the McKee Refinery in the Texas Panhandle, didn't have an effective program to identify and protect from freezing pipelines and equipment that were out of service or infrequently used. It also found the refinery didn't apply company policies on emergency isolation valves to control fires.

The refinery, 65 miles north of Amarillo, exploded in February 2007. The blast was so big, a billowing cloud of smoke could be seen 60 miles away. Three workers were critically injured, and the major refinery shut down for two months.

The fire occurred in the refinery's propane de-asphalting unit, which uses propane as a solvent to separate gas oil from asphalt. The leak occurred in an ice-damaged section believed to have been out of service since the early 1990s, CSB investigators said.

Water likely froze in the pipe during a cold snap and then melted prior to the blast.

Valero spokesman Bill Day said the company has already begun implementing new safety measures at its refineries, including the removal of unused pipelines and the installation of remotely operated shut-off valves to reduce risks in these kind of incidents.

CSB investigators said the McKee Refinery fire could have been far worse.

"There were a couple of near-misses," said Investigations Supervisor Don Holmstrom.

The fire caused the release of an estimated 5,300 pounds of chlorine from tanks near the fire. The highly toxic chemical could have posed a serious threat to emergency responders had they not already been evacuated, Holmstrom said.

The fire also threatened, but didn't reach, a tank containing up to 151,000 gallons of liquid butane. Workers couldn't reach the controls for the water system designed to cool the tank in an emergency.