The company hopes the new cap will be able to completely contain the leaking oil, but tests are still needed to determine its effectiveness.
Video supplied by BP showed robotic arms gingerly lowering the new 18-foot, 150,000-pound cap over the well, with little oil appearing to escape.
If the new cap does not completely contain oil from the crippled well, some may have to be brought to the surface to waiting containment ships. But under a worst-case scenario, there could be new damage to blowout preventer.
The "well integrity" tests are due to begin Tuesday morning, CNN's Ed Lavandera reported on "The Situation Room." The process could take anywhere from six hours to two days.
Here's video of the undersea robots placing the cap on the gushing well (there is no sound.) Take a look:
BP issued a statement today that said "It is expected, although cannot be assured, that no oil will be released to the ocean for the duration of the test. This will not however be an indication that flow from the well bore has been permanently stopped." A great deal of testing must be done to see if the new cap will hold.
