Investigators said Monday that in the hours and days before the Deepwater Horizon explosion in the Gulf of Mexico, workers made decision after decision that steadily increased risks -- but there is no evidence anyone at BP deliberately cut corners in order to save money. During a day-long hearing, the presidential commission investigating the Deepwater Horizon disaster highlighted a series of possible problems in the hours before the explosion, including misinterpreted pressure tests, possibly unstable cement used to seal the well and missed warning signs that gas had breached the well. When a surge of natural gas flowed unchecked out of the well and ignited on the Deepwater Horizon rig on April 20, the explosion killed 11 workers and triggered the nation's worst oil spill. Panel investigators also said they found no smoking gun that revealed any conscious decisions by BP officials to trade safety for dollars on the Macondo well project. But, they added, that doesn't mean people weren't thinking about costs -- given that the daily price tag was about $1.5 million and the project was about 45 days behind schedule. 'Anytime you're talking about a million and a half dollars a day, money enters in,' said Fred Bartlit, the commission's chief counsel and lead investigator. But, he added, 'I don't believe people sit there and say, 'this is really dangerous, but the guys in London will make more money.' It's more complicated than that.' The finding bucks a common criticism on Capitol Hill, where lawmakers have speculated that the high cost of drilling -- and the potential lost millions from waiting for tests to be conducted and more equipment to be installed -- may have prompted BP to make fatal decisions to speed up work. For instance, BP has been rapped for choosing a potentially more vulnerable well design that relied on a long string of casing that went all the way to the top of the well, rather than a more time-consuming plan using a liner that involved shorter segments of pipe. And lawmakers also have faulted the company for opting to abandon its plan to add 15 more devices known as centralizers to secure a section of pipe-like casing in the middle of the well hole before cement was poured around it. BP officials said they believed they had the wrong type of centralizers on hand. 'There seemed to be a compulsion to get this rig completed in that April 19, April 20-time period,' noted commission co-chairman Bob Graham, a former Democratic Florida senator and governor. As a result of that timeline, 'a number of things which might have made the outcome of this quite different were deferred or abandoned.' The other commission co-chairman, William Reilly, a former Republican head of the Environmental Protection Agency, said he was concerned about 'a culture of complacency affecting everything involved with this exercise.' Ultimately, he added, the explosion was the culmination of 'several very human decisions made by competent professionals who missed signals.' During a long day of courtroom-like questioning of representatives from BP, rig owner Transocean, and Halliburton, the cement contractor, the companies tried to shift blame for key decisions. Halliburton insisted that BP should have used more centralizers to ensure a balanced cement job that could effectively isolate the well from outside oil and gas. Richard Vargo, a Gulf of Mexico region manager for Halliburton, also stressed that a successful cement job can only be confirmed if a test known as a cement bond log is conducted -- something that BP opted against. Mark Bly, a BP vice president who led that company's internal probe, insisted Halliburton should have done a better job of flagging its concerns and highlighting 'critical' issues. And Transocean's director of special projects, Bill Ambrose, insisted that BP workers -- not its employees -- were responsible for interpreting a so-called 'negative pressure test' used to verify well integrity. 'Who makes a decision that a test has passed -- that interpretation lies with the operator,' Ambrose said. Bartlit said it is unclear why workers on the Deepwater Horizon rig believed the test had been successful, despite repeated pressure spikes that should have indicated problems. Although negative pressure tests are crucial to evaluating well integrity, there are no federal regulations that require them, much less give guidelines for their interpretation. And while BP requests the tests, it doesn't have set procedures or training for its well site leaders on how they should be done. At BP's Macondo well, the negative pressure test was even more essential, said commission deputy chief counsel Sean Grimsley, because right afterward, the oil company planned to displace heavy drilling muds that help contain oil and gas with lighter seawater. Grimsley noted the displacement is a particularly vulnerable time -- when there are no other barriers between the bottom of the well and the rig more than a mile above, so it placed 'a premium' on a successful pressure test. A major dispute erupted over the precise flow of oil and gas through the well. Commission investigators concluded -- along with BP -- that the hydrocarbons traveled up the center of the well, rather than in the space between the drill pipe and the hole known as the annulus. But Vargo insisted that gas flowed through the annulus -- a conclusion that would point to problems with the well design under BP'S control, rather than Halliburton's cement job. The company representatives did not testify under oath, because the national commission does not have subpoena power. Only Congress can authorize the issuance of subpoenas -- President Barack Obama created the commission by executive order. Although the House has twice voted to give subpoena power to the panel, those proposals have stalled in the Senate. Commission investigators and leaders urged the lame-duck Congress to pass the legislation later this month -- or else some questions about what happened on the Deepwater Horizon rig may never be answered. The seven-member panel is expected to submit its final report in January, but Graham said the commission could ask for more time if it were granted the authority. (Jennifer A. Dlouhy can be reached at 202-263-6400 or at the e-mail address jdlouhy@hearstdc.com) 