The "timelines won't be known until we get a recommendation on the course of action," he said.
Allen told reporters that when it comes to giving a green light to the "bottom kill" of the well through the nearby relief well, "nobody wants to make that declaration any more than I do," but the process "will not start until we figure out how to manage the risk of pressure in the annulus."
The annulus is a ring that surrounds the casing pipe, which sits in the center of the well shaft. Unless the annulus is breached, it should be accessible only from the bottom of the well.
Scientists began new pressure tests last week to gauge the effects of the mud and cement poured into the well from above during the static kill procedure that started August 3 and ended a few days later. From those pressure readings, they believe that either some of the cement breached the casing pipe and leaked into the annulus or cement came up into the annulus from the bottom.
The scientists believe that process may have trapped some oil between the cement and the top of the well, inside the annulus. Now, given that new variable, they're trying to figure out how to safely maintain the pressure within the well.
"We're using an overabundance of caution," Allen said.
The former Coast Guard admiral said the science team should settle on one of two options soon to deal with the situation. Then, the scientists will meet with Interior Secretary Ken Salazar and Energy Secretary Steven Chu to make their recommendation as to how to proceed. Chu would then need to sign off on a plan.
Allen said the team is looking at two primary options for how to deal with the situation.
First, crews could remove the capping stack that sealed the oil in the well on July 15, then replace the well's blowout preventer with a new one stored on the nearby Development Driller II in the Gulf. Allen said a new blowout preventer would be "rated at much higher pressure levels than the annulus."
The other option would require BP to devise a pressure-relief device for the current capping stack.
Once crews get their marching orders, it will take them about 96 hours to prepare, drill the final 50 feet of the relief well and intercept the main well. Then, the bottom kill process of plugging the well from below would begin, but "that seven days will not start until we figure out how to manage the risk of pressure in the annulus," Allen said.
The disaster began with an April 20 explosion aboard the BP-operated offshore drilling rig Deepwater Horizon that killed 11 workers. Roughly 205.8 million gallons of oil -- about 2.4 million gallons a day -- spilled into the Gulf from mid-April until July 15, when the well was capped, according to the most recent estimates from the U.S. scientific teams charged by Allen with determining the flow of oil from BP's leaking well.
Almost four months after the initial catastrophe, the waterways on Alabama's coast that had been closed to fishing due to the oil spill in the Gulf of Mexico have been reopened for commercial and recreational fishermen to catch finfish, and all the waters in Mobile Bay north of Fort Morgan are open to shrimping, the state said Monday.
Tests conducted on finfish and shrimp in the area indicate no presence of oil or dispersants, the Alabama Department of Conservation and Natural Resources said in a news release.
However, crab harvesting is still prohibited while tests on blue crabs are being analyzed, according to the release.
In Gulf Shores, Alabama, Mayor Robert Craft told CNN on Sunday that the last oil washed up on the white sands about three weeks ago, and visitors are coming back to his resort town.
"We don't know what to expect and we certainly have no experience in dealing with it -- no training, no background and every day is a different day," he said. But he added, "The beaches are clean, and the water is open, and we still have hope to salvage a good portion of this year."
BP acknowledged Monday that the disruption the oil spill has caused to lives across the Gulf coast has built up tension among residents. In response, the company announced Monday it is providing a total of $52 million to five behavioral health support and outreach programs.
BP released a statement saying it would give the federal Substance Abuse and Mental Health Services Administration $10 million; the Florida Department of Children and Families, $3 million; the Louisiana Department of Health and Hospitals, $15 million; and the departments of mental health in Mississippi and Alabama, $12 million each.
"We appreciate that there is a great deal of stress and anxiety across the region, and as part of our determination to make things right for the people of the region, we are providing this assistance now to help make sure individuals who need help know where to turn," said Lamar McKay, president of BP America and incoming leader of BP's Gulf Coast Restoration Organization.
-- CNN's Vivian Kuo and Reynolds Wolf contributed to this report
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