By Steve Gorman
LOS ANGELES (Reuters) - Numerous lapses in safety measures, judgment and planning by Plains All American Pipeline LP led to and worsened a major oil spill last year that fouled miles of shoreline and ocean near Santa Barbara, California, the U.S. Transportation Department said on Thursday.
The agency said it would focus next on "enforcement options" against the Houston-based company for the rupture of an underground petroleum pipeline that federal inspectors have found was severely worn by corrosion.
In their final report on the spill, federal investigators concluded that Plains "failed on multiple levels to prevent, detect and respond to this incident," said Marie Therese Dominguez, head of the Transportation Department's Pipeline and Hazardous Materials Safety Administration.
While the immediate cause of the rupture was external decay, the company was at fault for failing to protect the pipeline from corrosion beforehand and to promptly detect and respond to the spill once it occurred, the agency said in a statement.
The report came two days after Plains was indicted in California on 46 state criminal charges stemming from the spill, which environmental groups seized on to warn of hazards posed by an aging U.S. oil and gas industry infrastructure.
By the company's own estimate, as much as 3,400 barrels of crude gushed onto the shore and into the Pacific Ocean when the company's 24-inch Line 901 burst along a coastal highway about 20 miles (32 km) west of Santa Barbara on May 19, 2015.
The spill, linked to the deaths of hundreds of sea birds and marine mammals, forced closure of two state beaches and left slicks that stretched over 9 miles of the ocean.
It ranks as the largest spill to hit the ecologically sensitive but energy-rich coastline northwest of Los Angeles since 1969's 100,000-barrel blowout in the Santa Barbara Channel.
The severity of the 2015 spill was compounded by flawed response planning that overlooked the presence of a roadside culvert beside the pipeline that acted as a channel for escaping crude to flow easily to the sea, the federal report said.
An internal pipeline inspection conducted two weeks before the accident revealed far less corrosion than actually existed, the report said, citing shortcomings in both the inspection tool and the company's analysis of its data.
Plains said it was reviewing the report but declined to comment on its findings.
Line 901 typically carried about 1,200 barrels of oil an hour from an Exxon Mobile processing plant to a longer pipeline 10 miles away, Line 903, which transported the oil on to gathering facilities and refineries inland.
Both lines have since been shut down, forcing Exxon and two other companies to idle a total of seven offshore platforms that account for roughly 38,000 barrels of oil a day, Santa Barbara County officials say.
(Reporting by Steve Gorman; Editing by Jonathan Oatis and Leslie Adler)