Photos: A second chance for Shell Oil's 'fourth line of defense'

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The Arctic Challenger with the newly redesigned and repaired Containment Dome move away from the Port of Bellingham, Wash. on Dec. 12. The challenger had been moored since returning in September 2012 after a catastrophic failure of the first iteration of their containment process.

The containment dome Royal Dutch Shell hopes never to use has been transformed, following an accident this September that left it "crushed like a beer can" -- hampering the company's groundbreaking effort to suck oil from the Arctic Ocean off Alaska's North Slope.

The failed Puget Sound sea trial for the unique dome, essentially an undersea oil-sucking vacuum cleaner, plus construction delays on the Arctic Challenger barge that will house it, stymied Shell's plans this summer to drill deep enough to reach oil this summer.

The problems delayed federal regulatory approval, so Shell was merely allowed to conduct well preparation and preliminary drilling that stopped nearly a mile short of where the company expects to find oil.

Shell overhauled the barge this year -- it once sat so long it became a protected bird rookery in California -- in a round-the-clock effort involving ...

More: Will Shell's Arctic oil containment dome fare better second time around?