The containment dome that will be placed over the Macondo well site to capture leaking crude oil departed Port Fourchon, La., late Wednesday afternoon.

Following the approximately 12-hour trip aboard the M/V Joe Griffin to the Deepwater Horizon site, the 125-ton cofferdam structure will be lowered approximately one mile to the sea floor where it will be placed atop the largest leak source. It will serve as a containment chamber, collecting crude oil and funneling it to the Discoverer Enterprise drillship on the surface via approximately 5,000 feet of 6 5/8-inch drill pipe riser.

Low water temperatures approximately 42 degrees Fahrenheit and high (2,300 psi) pressures at the great depth in question will make the operation particularly challenging. In order to prevent pipe-clogging gas hydrates from forming under these extreme conditions, BP will work to ensure that the crude oil stays at an acceptably warm temperature throughout the riser. It will do so by pumping seawater from the surface into the annular space of a second, 21-inch riser that will encase the primary riser and by pumping methanol into the top of the containment dome. Crude will be processed aboard the drillship and separated into oil, gas, and water. The oil will be stored on the ship and ultimately offloaded at a terminal facility on land.

BP personnel anticipate spending two or three days perfecting the process, but the Subsea Oil Recovery System could begin processing fluids and stop the spill as early as Monday. That is, of course, if all goes according to plan.

During a Wednesday afternoon press conference, Coast Guard Rear Admiral Mary Landry -- federal on-scene coordinator of the response -- reminded members of the news media that the approach is not a sure thing. "This hasn't been done before, it's very complex, and it will likely have challenges on the way," added BP Chief Operating Officer Doug Settles.