Welders work on the top of a portion of the BP subsea oil recovery system chamber at Wild Well Control, Inc. in Port Fourchon, Louisiana May 3, 2010. The swelling slick coming from the Deep Water Horizon wellhead is estimated to be at least 130 miles (208 km) by 70 miles (112 km), threatening shipping, wildlife, beaches and one of the United States' most fertile fishing grounds. U.S. President Barack Obama has called the situation "a massive and potentially unprecedented environmental disaster." REUTERS/Sean Gardner (UNITED STATES - Tags: DISASTER ENERGY ENVIRONMENT BUSINESS IMAGES OF THE DAY)