Washington (CNN) -- Interior Department regulators designing disaster contingency plans didn't prepare for a calamity the size of the current Gulf of Mexico oil spill crisis because of a lack of precedent, a former interior secretary said Tuesday.
Dirk Kempthorne told a joint congressional subcommittee that previous environmental impact statements, assessments and oil spill response plans were "based on the probability that a significant oil spill was small."
"When the 2007 and '12 five-year plan was written, there had not been a major oil spill in 40 years," he said. "One very real consequence of the Deepwater Horizon accident is that these historical assumptions will be forever changed."
Kempthorne added that the repercussions from BP's ruptured oil well in the Gulf of Mexico "will forever change the offshore energy industry. Never again will a cabinet secretary take office and be told that more oil seeps from the seabed than has been spilt from drilling operations in U.S. waters. Never again will decision-makers not include planning for events that might be low-probability events, but which, in the unlikely event they occurred, would be catastrophic."
Two House subcommittees held a joint hearing Tuesday to investigate the role of the Interior Department in the Deepwater Horizon disaster. Legislators are trying to figure out who's responsible for the crisis and how better government regulation of energy producers might help avert such disasters in the future.
Kempthorne and Gale Norton, who preceded him as interior secretary under President George W. Bush, showed up at the beginning of the session to testify. Current Interior Secretary Ken Salazar was expected to appear later Tuesday.
The beginning of the hearing consisted of several lawmakers lobbing partisan broadsides against the opposing party's administration. House Energy and Commerce Committee Chairman Henry Waxman, D-California, was one of the few to acknowledge fault on both sides of the aisle.
"Today, we're going to examine the role of the regulators," Waxman said. "We will learn that the Department of Interior under both President Bush and President Obama made serious mistakes. The cop on the beat was off duty for nearly a decade and this gave rise to a dangerous culture of permissiveness."
While lawmakers in Washington debate the causes of the crisis, people across the Gulf region were working on solutions.
As tests continued Tuesday on the temporarily, yet apparently securely, capped well, scientists were weighing a new option for permanently sealing it.
The "static kill" would involve pumping mud into the well to force oil back into the reservoir below, officials from BP said Monday, noting that the option could succeed where similar attempts have failed because pressure in the well is lower than expected.
Geologist Arthur Berman said on CNN's "American Morning" Tuesday the relative simplicity of a static kill makes it an attractive option for BP.
"I think the reason that they're considering it is because they've yet to intercept the well bore," Berman said. "They're very close, a few feet away with the relief well, as everyone knows. But to actually intersect the 7-inch pipe does involve a bit of technology and accuracy, whereas if they do the static kill through the existing well bore at the top, there's less uncertainty about their ability to actually get the mud into the pipe."
No visible oil has flowed from the well since July 15, when BP closed all the valves in a new custom-made cap that was installed July 12.
Energy Secretary Steven Chu refused comment on the proposed static kill. He said the Obama administration is assimilating the constantly evolving information about the crisis to "try and formulate plans going ahead that will bring the ultimate stopping of the leak as quickly as possible, at the same time trying to minimize oil spillage."
BP Senior Vice President Kent Wells told reporters Monday that the static kill idea was still "very much in its infancy," but a decision could be made in several days.
"At the end of the day, relief wells are still the ultimate solution," he said.
Former Coast Guard Adm. Thad Allen, the federal government's point man on the spill, said Monday that there were no signs of significant problems with the ruptured well's casing. But he said tests on the well would continue for another 24 hours as federal and company officials try to explain "anomalous" pressure readings and possible leaks.
Allen said there were possible leaks of methane gas from around the well and from the inoperative blowout preventer, as well as a separate and possibly unrelated seep from the ocean floor about 3 kilometers (about 2 miles) away.
Scientists and engineers are still debating whether the low pressure is caused by the well's depletion after three months of spewing oil into the Gulf, or whether oil is leaking from the well into the surrounding sea floor, Allen said.
"There are arguments to be made on both sides," he said. "But those discussions continue, and we're trying to develop information that will allow us to do that."
Berman said the seepage could be unconnected to the well, either naturally occurring or caused by the search for seepage.
"Having seeps on the sea floor is not anything out of the ordinary. Certainly not in this area of the Gulf of Mexico," Berman said. "The evidence perceived is unclear to me. There are a lot of people that are watching the live feeds from the ROVs (remotely operated vehicles) and they think they see things that they are sure are seeps, but I've had correspondence with experts on these ROVs and apparently the ROVs themselves have thrusters that can very easily stir up the bottom sediments and create some sort of illusion that there is seepage."
If scientists detect a leak, Allen said, officials are ready to resume collecting oil.
"At any moment, we have the ability to return to the safe containment of the oil on the surface until the time the relief well is completed and the well is permanently killed," Allen said.
In the coming weeks, BP has said, it also plans to bring in two more oil collection ships in addition to the two already in the Gulf, bringing containment capacity to 80,000 barrels (nearly 3.4 million gallons) of oil a day, more than high-end estimates of how much oil had been leaking. Coast Guard Rear Adm. Paul Zukunft, Allen's deputy on the scene, said the Helix Producer and the Q4000, two of the ships disconnected from the well to make way for the containment cap, could be quickly reconnected within hours if scientists decide that's necessary.
In addition, BP also plans to conduct tests known as ranging runs on one of its relief wells, which company officials have said could intersect the ruptured well by the end of July and provide the permanent solution to the leak.
CNN's Eric Fiegel and Vivian Kuo contributed to this report.