(CNN) — A Royal Dutch Shell drilling unit was aground on an uninhabited Alaskan island early Tuesday after lines to a tugboat that was towing the rig during a fierce winter storm were cut to ensure the safety of the tugboat’s nine-man crew, the U.S. Coast Guard said in a statement.
The drilling rig Kulluk originally went adrift for 10 hours on Sunday while being shuttled to Seattle when the tug that was towing it lost power.
Crews of two Shell-contracted tugboats were able to secure towing lines to the Kulluk the following day.
But just after 8 p.m. Monday, the weather conditions made the towing effort too dangerous, according to a statement from the response team in charge of the rig. It was allowed to drift free, running aground off Sitkalidak Island.
“The extreme weather conditions and high seas continue to be a challenge. We have more than 250 people actively involved in the response efforts,” said Susan Childs, incident commander for Shell. “Our priority right now is maintaining the safety of our response personnel and evaluating next steps.”
The rig grounded in an area of Ocean Bay where water depth is 32 feet to 48 feet, according to a release from the response team.
It reported that the rig had 139,000 gallons of ultra low sulfur diesel and 12,000 gallons of combined lube oil and hydraulic fluid on board, but no leaks had been detected.
Weather conditions were expected to improve Tuesday and through the rest of the week, with seas subsiding from 24 feet on Tuesday to 11 feet by Friday, according to the National Weather Service.
The rig’s 18-person crew was evacuated Saturday.
The Kulluk finished drilling operations in the Beaufort Sea in October and was headed to its winter home when the tug boat that was towing it lost power, resulting in the current problem.