A top Department of Veterans Affairs official said Wednesday that his agency may never explain precisely how a hospital project in Aurora with a $604 million construction budget skyrocketed to $1.73 billion in barely two years.

Members of Congress, including Democratic Sens. Michael Bennet of Colorado and Richard Blumenthal of Connecticut, have asked for a detailed account of the price increase, saying those numbers must exist.

But during a news conference at the construction site, VA Deputy Secretary Sloan Gibson said not to expect a line-item description of the $1.1 billion difference.

“You’re not going to find a dollar-by-dollar account,” he said.

Gibson said the best explanation of the cost overruns can be found in the Civilian Board of Contract Appeals court decision in December 2014 that sustained contractor Kiewit-Turner’s complaint against the VA.

That ruling identified numerous VA errors but did not estimate how much any mistake cost.

Gibson said the two biggest contributors to the cost increase in Aurora were the decision to use an Integrated Design and Construct contract, a method unfamiliar to the VA, and the handwritten agreement signed in November 2011 to get construction started.

That agreement, known as SA-007, “put the liability of cost on the VA” to provide an affordable design, Gibson said. “From that point on, VA and Kiewit-Turner were at odds.”

Gibson met privately with Kiewit-Turner and VA project executives and held a conference call with Colorado’s congressional delegation before speaking with reporters.

On his eighth trip to Denver, he finally caught a warm day — and emerged with a sunny prediction.

“This project is going to get finished. I have absolutely no doubt,” he said.

Gibson described the attitude of all parties as open and candid. “We get issues on the table and work to get them resolved,” he said.

The VA has reduced the estimated cost of the project by dropping a nursing home and a PTSD center from the plans. Congress has provided enough money to keep construction going through September, but Gibson said about $625 million is still needed to complete the medical center.

PHOTOS: Take a tour of the embattled Aurora VA Hospital

The department has offered to take a 0.89 percent across-the-board cut to finance the remaining work. That cut would not affect veterans’ benefits.

For the VA, its Colorado hospital complex has become the sorest spot in a much-maligned major construction program.

Construction halted last December after Kiewit-Turner won the court case, resumed under an interim agreement, then nearly halted again in May before Congress provided another short-term infusion of money.

Meanwhile, construction is proceeding with a reduced work force, and Gibson hesitated to predict that the hospital could still open in 2017.

He defended his department’s accountability, noting that two senior executives retired amid questions from an agency-appointed investigative board and other top officials involved in the Aurora project had retired before the investigation.

“None were removed,” however, he said.

That explanation did not satisfy the state chapter of Concerned Veterans for America, which issued a statement after the news conference.

“Individuals overseeing such a disastrous project should be held accountable, but instead they were allowed golden parachutes and received millions of dollars in bonuses,” said Frank Crocker, its state director.

Gibson was asked if he felt the VA’s response to the Aurora debacle would satisfy congressional critics.

“The honest answer is no,” he said. “They want to see people fired.”

David Olinger: 303-954-1498, dolinger@denverpost.com or twitter.com/dolingerdp