NEW : BP plans to place a third rig called the Helix Producer at the well site next week , which will increase the amount of oil being captured to 53,000 barrels a day , Allen said . Shell , BP evacuate nonessential personnel from Gulf of Mexico platforms . The oil spill is now the largest in U.S. history and has already cost more than $21 billion to clean up. Alex could push more oil ashore . Alex moving toward Mexico 's Yucatan Peninsula .
NEW : Shell , BP evacuate nonessential personnel from Gulf of Mexico platforms . The oil spill is now the largest in U.S. history and has already cost more than $21 billion to clean up. Alex could push more oil ashore . Alex moving toward Mexico 's Yucatan Peninsula .