Will environmentalists block Shell's offshore Arctic drilling plans?

Environmental groups are renewing a challenge to 2008 lease sale of Arctic sea off Alaska's northwest shore.

A dozen environmental groups told a federal court Monday they are renewing a challenge to the 2008 federal petroleum lease sale off Alaska's northwest shore, where Royal Dutch Shell PLC hopes to drill exploratory wells this summer.

The groups have twice obtained court rulings that said environmental analysis preceding the Chukchi Sea sale was flawed. The Department of Interior in March concluded that it had corrected mistakes.

Erik Grafe, an attorney for Earthjustice, said by phone Monday the environmental groups disagree and will lay out their claims in a future court filing.

The 2008 sale sold leases on 2.76 million acres, or 4,312 square miles (11,168 square kilometers), and brought in $2.7 billion for the federal government.

Shell spent $2.1 billion on high bids and began exploratory drilling in 2012. It has since spent upward of $7 billon, including the cost of staging drilling vessels and a support fleet in Seattle for the 2015 open water season.

Conservation and Alaska Native groups in their lawsuit said the former Minerals Management Service had based the sale's environmental review on projected extraction of only 1 billion barrels of oil. A court-ordered supplemental review assumed an extraction of 4.3 billion barrels.

The filing Monday informs the court that the environmental groups will continue their claim that the environmental review for the lease sale was insufficient, Grafe said.

The groups remain concerned about the effects of drilling around Hanna Shoal, an underwater plateau 80 miles (130 kilometers) off the coast that is important walrus habitat, Grafe said.

The revised environmental analysis also fails to assess the climate effect of burning 4.3 billion barrels of oil, Grafe said.

"This is an energy decision," he said. "It's about where we're going to get our energy in the future. That needs to be made in the context of climate policy and that wasn't done here."

John Callahan, spokesman for the Interior Department's Bureau of Ocean Energy Management, said the agency could not comment on the litigation.

Environmental groups strongly oppose Arctic outer continental drilling and say industrial activity and a major spill would harm marine mammals already hurt by climate warming.

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