Contractors will pay more than $450 million to settle the state's lawsuit over a fatal tunnel collapse and to cover the costs of leaks and design flaws in the Big Dig, officials said Wednesday.

Bechtel/Parsons Brinckerhoff, the consortium that oversaw design and construction of the nation's costliest and most complex highway project, has agreed to pay $407 million, U.S. Attorney Michael Sullivan said in announcing the deal. Several smaller companies will pay about $51 million collectively.

"The citizens of Massachusetts entrusted Bechtel/Parsons Brinckerhoff to act as their eyes and ears on the Central Artery Project," Sullivan said. "They grossly failed to meet their obligations and responsibilities to the citizens of Massachusetts and the United States."

Under the settlement, Bechtel/Parsons Brinckerhoff will not face criminal charges in the deadly Interstate 90 tunnel ceiling collapse in July 2006. Milena Del Valle, 39, of Boston, was crushed by 26 tons of concrete as she and her husband drove to Logan International Airport.

The deal also does not bar the consortium from receiving future government contracts. Bechtel/Parsons Brinckerhoff was paid more than $2 billion to manage the project.

State officials will be able to seek additional damages from Bechtel/Parsons Brinckerhoff if a future accident or event causes more than $50 million in damages. Its liability will be capped at $100 million, and an arbitrator would decide whether the consortium was to blame.

Sullivan said Bechtel/Parsons Brinckerhoff, which managed the project over 20 years, made $150 million in profit from the Big Dig.

"They lost money as a result of the failures that occurred under their watch," Sullivan said.

The settlement does not have a direct effect on a separate lawsuit filed by Del Valle's family.

"We believe that today's global agreement is the best possible resolution. I do not say perfect, but the best possible resolution at this time," Attorney General Martha Coakley said.

Powers Fasteners Inc., the only company that has been criminally charged in the tunnel collapse, also is the only one out of 15 companies that has settled with the Del Valle family. Powers, which provided the epoxy blamed for the collapse, has agreed to pay the family $6 million.

The Brewster, N.Y.-based company, which has been charged with involuntary manslaughter, has denied responsibility for the collapse.

Max Stern, the company's lawyer in the criminal case, criticized the decision by prosecutors to allow Bechtel/Parsons Brinckerhoff, a multibillion-dollar consortium, to avoid criminal charges while pursuing charges against Powers, a smaller, family-owned business.

"Obviously, this is out of Powers' price range," Stern said of the $407 million settlement.

"The sheer size of this settlement underlines what we think is the undeniable fact that Bechtel bears the real responsibility for this accident. After all, Bechtel was responsible for the design, it was responsible for the construcction crews had considered that the epoxy holding support anchors for the panels could slowly pull away over time.

Dec. 31 marked the end of the joint venture that teamed Bechtel/Parsons Brinckerhoff with the Massachusetts Turnpike Authority to bury the old elevated Central Artery that ran through the heart of Boston with a series of tunnels, ramps and bridges.

The $14.79 billion Big Dig, which had an initial price tag of $2.6 billion, was plagued by problems and cost overruns throughout the two decades it took to design and build.