Cofferdam Begins Descent

BP on Thursday began lowering the containment dome at the site of the leaking Macondo well, approximately 5,000 feet below the surface.

A crane on Helix Energy's multi-purpose vessel, the Q4000, is lowering the 40- by 24- by 14-foot cofferdam to the target location. Once the nearly 100-ton steel chamber reaches the seabed to cap the crude oil discharge, BP will attempt to connect it to a riser system. The plan calls for funneling the contained crude nearly one mile up to the Transocean drillship Discoverer Enterprise on the surface via 6 5/8-inch drill pipe riser. BP will pump seawater from the surface into the space between the drill pipe and an outer, 21-inch riser in order to keep the crude flowing. The company continues to use remotely operated vehicles (ROVs) to monitor the subsea situation.

According to BP, it will be possible to assess the effectiveness of the containment dome solution  -- unprecedented at this water depth -- once the structure's descent to the seabed and connection to the riser system are complete.