( CNN ) -- The Royal Dutch Shell oil drilling barge that ran aground off southern Alaska this week is sound and ready to be towed to safe harbor , a company official said Saturday , adding there is no evidence of any sheen in the vicinity . The 266-foot-diameter Kulluk remains upright and there is no apparent threat to its stability , said Sean Churchfield , the incident commander and operations manager for Shell Alaska . The fuel tanks appear intact , and naval architects report the vessel is sound and fit to tow , he said . The Killuk ran aground off uninhabited Sitkalidak Island , about 200 miles south of Anchorage , on Monday night . The current tow plan calls for the barge to be towed 30 miles to the north to Kiliuda Bay for safe harbor and a more detailed assessment . `` The exact timing of a potential towing activity will depend on weather , tides and operational readiness , '' Churchfield told reporters in a news conference . As much as 150,000 gallons of ultra low sulfur diesel and approximately 12,000 gallons of other petroleum products are on board the Kulluk , which had been working in the Beaufort Sea , off Alaska 's North Slope , until October . The vessel was being towed back to its winter home in Seattle when it ran into a severe storm off the Alaskan coast . The Coast Guard evacuated the Kulluk 's 18-man crew Dec. 29 , and it drifted for 10 hours the following day after the tug that was towing it lost power . Monday night , tug crews had to cut the rig loose during a storm that whipped up 24-foot waves . That led to its grounding in an area where water depth is 32 to 48 feet . The Kulluk is a blue and white circular rig with a helicopter landing pad and a tower in the middle . The steel vessel is double-hulled and designed for drilling in Arctic waters . Most of the nearby shore is owned by a native Alaskan corporation on adjacent Kodiak Island , said Steven Russell , of Alaska 's Department of Environmental Conservation . State officials are working with residents to watch for any environmental impact caused by the grounding . Shell 's Arctic exploration plans caused widespread concern among environmentalists and were held up after BP 's Deepwater Horizon disaster in the Gulf of Mexico . Shell says it 's working at far less depth and lower pressures than the BP well that erupted off Louisiana , killing 11 men aboard and unleashing an undersea gusher that took three months to cap . The fuel on board the rig is used to power equipment and is not the result of the drilling operations Shell conducted off the North Slope , on the opposite side of the vast state from where the Kulluk now rests . The U.S. Geological Survey estimates more than 90 billion barrels of oil and nearly 1,700 trillion cubic feet of natural gas may be recoverable by drilling . And the shrinking of the region 's sea ice -- which hit record lows in 2012 -- has created new opportunities for energy exploration in the region . Climate researchers say that a decrease in sea ice is a symptom of a warming climate , caused largely by the combustion of carbon-rich fossil fuels . The science is politically controversial but generally accepted as fact by most scientists . CNN 's Matt Smith contributed to this report .
Shell says there is no evidence of any sheen in the vicinity . The Coast Guard said it was investigating a report that an oil slick had been spotted near the site where the rig exploded. The fuel tanks appear intact , the company says . The drilling rig ran aground during a storm Monday off Alaska 's southern coast .