By Steve Gorman
LOS ANGELES (Reuters) - An environmental group petitioned the federal government on Thursday to immediately inspect more than 200 miles (320 km) of undersea oil pipelines off California's coast.
The Center for Biological Diversity cited extensive corrosion that is believed to have caused an onshore pipeline to burst in May west of Santa Barbara, unleashing the biggest oil spill to hit that region in more than four decades.
The failed pipeline, which had been inspected by its owner, Texas-based Plains All American Pipeline, weeks before the rupture, is decades younger than much of California's offshore infrastructure, the group said in its petition.
Many of those undersea pipelines date to the 1960s and are well past the 30 years of age shown to significantly increase the risks of failure, while the spill has exposed weaknesses in the current regimen of self-policing, the petition said.
Two weeks before the spill, Plains had reported to federal regulators that the section of pipe that burst had lost about 45 percent of its original wall thickness. After the spill, third-party inspectors found that corrosion had degraded the wall thickness to just 1/16th of an inch (1.6 mm), beyond the 45 percent metal loss Plains had reported.
Not only are many of California's offshore pipelines older than the Plains onshore line but they are subject to greater wear and tear from saltwater, surf, storms and subsea pressure, the petition said.
As a safeguard against further spills, the letter called for the U.S. government to immediately inspect the more than 200 miles of undersea oil pipelines off California, most of them in federal waters, which collectively carry millions of gallons of petroleum to shore each day.
The petition was delivered to the U.S. Transportation Department's Pipeline and Hazardous Materials Safety Administration and the Interior Department's Bureau of Safety and Environmental Enforcement.
Bureau spokesman Greg Julian said the agencies were reviewing the petitions and had not decided yet on a response, adding: "We have a very active and thorough inspection program."
Center for Biological Diversity attorney Kristen Monsell said the government now requires operators to periodically inspect their own pipelines, generally once every five years for those in "sensitive" areas.
The petitions came a day after Plains said new calculations found that its ruptured pipe may have spilled 41 percent more crude, about 1,000 barrels more, than previously estimated, or up to 3,400 barrels.
Either estimate ranks as the largest spill to foul the ecologically sensitive but oil-rich coastline northwest of Los Angeles since a massive 1969 blowout dumped up to 100,000 barrels of crude into the Santa Barbara Channel.
(Reporting by Steve Gorman; Editing by Eric Beech)