The well had supposedly been plugged at the bottom with a modest quantity of cement, 60 barrels. The negative test essentially tempted oil and gas to invade the well. The drill team removed much of the heavy drilling mud that normally choked the well, to see whether that would cause pressure to build up on the drill pipe. If the cement had effectively plugged the bottom of the well, there should not have been any pressure.

But the initial result was troubling, according to testimony at the government inquiry conducted by the Coast Guard and what was then called the Minerals Management Service. When the drill pipe was opened at the top, fluid surged up onto the rig. When crewmen closed the drill pipe, pressure rose again.

People on the rig that day testified that one of the Transocean employees, tool pusher Jason Anderson, suggested that the troubling pressure reading was due to what he called the “bladder effect.” This has remained a fuzzy element of the disaster narrative. The testimony indicated that Anderson believed that heavy mud still in the well could have been creating the pressure seen on the drill pipe and that the pressure was not caused by oil and gas invading the well bore.

“BP’s onshore team should have, and easily could have, alerted the well site leaders and rig crew that cement failure at Macondo might be more likely than normal and instructed them to be extra vigilant regarding any odd pressure readings,” the chief counsel’s report stated.

The Oil Spill Commission concluded that multiple risk factors played a role in the disaster, including a flawed recipe for the cement slurry; procedures that included unnecessary removal of mud from the well bore; inadequate supervision of late-stage decisions in the well design; and missed signals from pressure gauges suggesting that gas had entered the well. The commission also found feeble regulatory oversight by the government. “Each of the mistakes made on the rig and onshore by industry and government increased the risk of a well blowout,” the commission concluded.

In a bizarre twist to the onshore-offshore dichotomy, two of Kaluza and Vidrine’s bosses happened to be on the rig at the time of the disaster. The two BP executives, Pat O’Bryan and David Sims, had flown by helicopter to the rig that afternoon along with two Transocean executives. The four executives took a tour and then held a meeting to congratulate the rig crew on its record of safe operations. The executives were not asked for input into the interpretation of the negative test.

Neither Kaluza nor Vidrine testified during earlier investigatory hearings. BP records obtained by the government show that Kaluza e-mailed two colleagues days after the blowout:

“I believe there is a bladder effect on the mud below an annular preventer as we discussed,” Kaluza wrote.

The grand jury indictment charged that Kaluza and Vidrine “accepted a nonsensical explanation for the abnormal readings, again without calling engineers onshore to consult.”

Both men remain employed by BP but have been on leaves of absence since the disaster.

Kaluza’s attorney, Clarke, said his client is being blamed for an accident that was the result of a collective failure. Kaluza had been on Deepwater Horizon only four days when the disaster happened. He had replaced another company man who had gone to shore to take classes in blowout prevention.

“Right now he’s devastated. He’s with family. But he feels very strongly that he did not cause the deaths of his 11 co-workers and he did not cause the most monumental environmental disaster in the country’s history,” Clarke said of his client. “And he has every intention of proceeding to trial.”