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(Updates with Coast Guard statement about the estimated size of the well leak.) NEW YORK (Dow Jones)--The U.S. Coast Guard said that operations will begin Sunday to secure a leak at a well off the coast of Louisiana. "When the source is secured, a cap will be installed to ensure the wellhead is permanently closed," the Coast Guard said in a statement Saturday. The leak began after the well was hit by a towing vessel four days ago. An oily sheen, recently seen across six miles, has largely remained in the Mud Lake area. The size of this leak--roughly estimated at 33 barrels a day--is a tiny fraction of the massive oil Gulf of Mexico oil spill that released tens of thousands a barrels a day starting in late April after the Deepwater Horizon drilling rig caught fire and sank. The newer, second leak is taking place at an orphaned well that is no longer in production. It has been spewing a mixture of oil, natural gas and water into Barataria Waterway when a vessel towing a barge hit the wellhead on Tuesday about 1 a.m. local time, the Coast Guard said in a written statement Saturday. It is unclear how much is leaking in this "uncontrolled situation, " but roughly 100 barrels could have been released since the incident began, based on the well's last known production rate of 33 barrels a day. As much as half of the light oil being released is expected to evaporate. "While we do not know the true release, twice as much as the production value is possible, but probably not three times that value," the Coast Guard said in an updated statement Saturday evening. About 52,800 feet of containment boom and 31 skimmers, boats and barges are being used to clean up the spill. And equipment needed to secure the leak, including two barges, will be deployed to the site to secure the wellhead starting Sunday morning. The Coast Guard said Friday that Chevron Corp. (CVX) and BP PLC (BP, BP.LN) pipelines in the area were marked to protect them from the vessels anchoring in the area. The clean-up is being funded by the Oil Spill Liability Trust Fund, which is supported by taxes paid by oil companies. The cause of the collision is under investigation. -By Naureen S. Malik, Dow Jones Newswires; 212-416-4210; naureen.malik@dowjones.com (END) Dow Jones Newswires July 31, 2010 21:01 ET (01:01 GMT)