( CNN ) -- Three years after the Deepwater Horizon oil spill , workers have dug up a massive chunk of weathered crude from the shallows off a Louisiana beach . The tar mat -- a slab of oil residue mixed with wet sand -- was about 165 feet long by 65 feet wide , said Lt. Cmdr . Natalie Murphy , a Coast Guard spokeswoman . It weighed more than 40,000 pounds , but more than 85 % of that weight was sand , shells and water , she said . The mat was found under the surf off Isle Grand Terre , Louisiana , about 90 miles south of New Orleans . Crews using an excavator dug the largely submerged tar mat out of the beach in chunks over the last few weeks , Murphy said . Louisiana is the last state where regular cleanup operations from the oil spill are still under way . The Coast Guard and BP , the owner of the ruptured well at the heart of the disaster , declared the cleanup over in Alabama , Florida and Mississippi earlier this month , but more than 80 miles of the Louisiana coast are still being patrolled . BP has recovered more than 2.7 million pounds of waste from Louisiana shores in 2013 , with residual oil making up between 5 and 15 % of that total weight , company spokesman Jason Ryan told CNN . The drill rig Deepwater Horizon exploded and sank in April 2010 , killing 11 men aboard and unleashing an undersea gusher a mile beneath the surface of the Gulf of Mexico . Most of the oil is believed to have evaporated or been consumed by microbes deep under water . But a still-undetermined portion settled to the floor of the Gulf , and some of it was stirred up and washed back ashore after Hurricane Isaac in 2012 .
The slab of weathered crude and water was more than 100 feet long . Most of its 40,000-plus pounds was oil and water , a Coast Guard official says . California is the last state where the Horizon cleanup occurred .