The findings, while preliminary, confirm “significant new questions,” according to a memo released by the House Energy and Commerce Committee (see right to download memo)

Among the red flags, they told the panel, were several equipment readings suggesting that gas was bubbling into the well, a potential sign of an impending blowout. Investigators also noted “other events in the 24 hours before the explosion that require further inquiry,” including a critical decision to replace heavy mud in the pipe rising from the seabed with seawater, possibly increasing the risk of an explosion.

Some of those who survived the explosion, including managers from BP and Transocean – which leased the Deepwater Horzion rig to BP –  are expected to testify at hearings in Louisiana to be held by the Coast Guard and the federal Minerals Management Service, beginning Wednesday.

The testimony may help clear up some of the uncertainties about the day of the accident, including who was making the decisions.

President Obama, whose frustration over BP’s seeming inability to plug the leak, is scheduled to revisit Louisiana on Friday, according to White House staff and press reports.

Much information confirms congressional findings.

The new information, released Tuesday night in a memorandum addressed to members of the House Committee on Energy and Commerce, confirmed many of the committee’s own findings from a review of documents and from statements and testimony given at Congressional hearings over the last two weeks.

The information provides the most detailed account yet of accounting of the events and decisions made aboard the Deepwater Horizon before the accident on April 20 that took 11 lives and caused a so-far unchecked torrent of oil to pour into the gulf, and comes as BP prepared an ambitious “top kill” procedure in a new effort to stop the leak.

BP announced yesterday, under pressure from Massachusetts Congressman Ed Markey, who heads up the House Committee on Energy and Commerce, that it would not kill the live video feed from the ocean floor during the top kill operation.

A 45 second view of the gusher taken by BP cameras and provided by RT to YouTube. BP’s live streamng video, which will continue through the top kill can be found here.

BP CEO Tony Hayward told NBC’s “Today” show that he will decide whether to proceed with the top kill Wednesday, after a number of reschedulings, after he and other top BP executives and engineers huddle later today.

“Later this morning I will review that with the team, and I will take a final decision as to whether or not we should proceed,” BP Chief Executive Tony Hayward told the morning news programme.

If he determines it is safe to proceed, the procedure is expected to happen on Wednesday, he said. He added it will take a day or two to determine whether the procedure worked. Only yesterday, however, Hayward gave the top kill procedure about a 60 to 70 percent of working.

As to the findings presented to Congress, Haward told reporters earlier this week that, “A number of companies are involved, including BP, and it is simply too early — and not up to us — to say who is at fault.”

The findings presented to congress are preliminary, and most come from BP, which owns the lease on the well and has at hearings pointed fingers at other companies for the problems on the rig, including Transocean, the rig’s owner.

The new findings

Even though recounted in BP’s words, the memo says there were  three warning signs of problems in the hour before the explosion, BP investigators informed the committee.

The first came 51 minutes beforehand when more fluid began flowing out of the well than was being pumped in, the memo said. When the pump was shut down for a test 41 minutes before the explosion, it continued flowing instead of stopping, and drill pipe pressure also unexpectedly increased. Then 18 minutes before the explosion, abnormal pressure and “mud returns” were observed and the pump was abruptly shut down.

“The data suggests that the crew may have attempted mechanical interventions at that point to control the pressure, but soon after, the flow out and pressure increased dramatically and the explosion took place,” the memo says.

The memo from the House committee, which is led by Representative Henry Waxman, Democrat of California, shows that other preliminary findings also indicate other events in the 24 hours before the explosion merit further investigation, it said.

Almost five hours before the explosion, an unexpected loss of fluid was observed in the riser pipe, suggesting a leak in a key part of the blowout preventer, the fail-safe device on the rig that failed.

The investigators also detailed problems encountered during pressure tests in the two hours before the explosion.

Negative pressure testing was initially done on the drill pipe rather than the kill line, even though the drill plan specified that it would be done on the kill line. After an unacceptable result from conducting the test through the drill pipe, the test was then moved to the kill line.

When pressure on the kill line was bled to zero, pressure on the drill pipe remained high, leading BP investigators to conclude a “fundamental mistake” may have been made at that time because those results indicated a “very large abnormality.”

After monitoring the kill line, the rig team determined the test was successful and started the process that led to the three problems in the hour before the explosion.

Mud displacement

Evidence also suggests several problems with the displacement of heavy drilling fluid, known as “mud,” with seawater. Spacer fluid used during the process did not rise to the level required by the drilling plan, increasing pressure in the drill pipe, and the mud was transferred to another boat instead of measured in the mud pits, which may have interfered with the monitoring of flow levels from the well, the memo said.

“Key questions exist about whether proper procedures were followed for critical activities throughout the day,” said the Waxman memo.

Congressional investigators and news accounts have suggested that the decision to begin removing drilling mud was a subject of intense discussion — and perhaps even disagreement — among engineers working on the rig that day, congressional aides told Bellona Web Wednesday morning.

Executives from both Transocean and BP have said in testimony before Congress that they were unfamiliar with the details of that debate. But the hearings this week in Louisiana – which will include testimony from the top managers on the rig from BP and Transocean – may provide a clearer picture of the day’s deliberations.

In the final hour before the explosion, after the crew had begun withdrawing the mud, there were more signs that the well was going out of control, the memo said.

They included a sharp increase in fluid coming from the well, even when the pumps were shut down – an indication, drilling experts say, of a “kick,” a surge in pressure from oil and gas deep down in the well. If not controlled, such a kick can lead to a full-scale blowout, and that is exactly what happened at roughly 9:49 p.m. on April 20th.

BP also identified several concerns related to the cementing process. Cement work failed, the float collar used in the cementing process originally did not work as intended and the test performed after cementing may not have been definitive, the memo said.

The company also detailed concerns with the blowout preventer, including the failure of its emergency disconnect system, deadman switch and shearing functions along with questions about its maintenance history, modification, inspection and testing.

Spill could be nation’s ‘biggest environmental disaster’ – EPA chief

Meanwhile, U.S. EPA chief Lisa Jackson yesterday said the spill could be the “biggest environmental disaster this country has ever seen.”

Asked whether BP was acting as a responsible environmental steward in the wake of the spill caused by its exploded Deepwater Horizon rig, Jackson yesterday said, “I don’t think anybody could call them a steward.” She added, “I don’t see how I can make that judgment about BP, just having what could well be the biggest environmental disaster this country has ever seen,” said Jackson in remarks reported by E&E Daily, an environmental newswire.