Colorado transportation officials have faced a flurry of legal challenges over the massive proposed project to widen Interstate 70 through northeast Denver — and they acknowledged Thursday that the plan likely will face new court challenges.

But after 14 years, officials finally have a long-sought document in hand: a federal “Record of Decision” that ends a thorough environmental impact study and gives the Colorado Department of Transportation an official green light to plow forward with the $1.2 billion project.

“When you talk about a marathon — this is a marathon,” said Commerce City Councilman René Bullock, a project supporter who joined local, state and federal officials at a news conference at CDOT headquarters.

On the horizon, as soon as early next year, is the start of four or five years of construction along 10 miles of I-70, from Brighton Boulevard to Chambers Road in Aurora. The CDOT-dubbed Central 70 project will gobble up 56 homes and 17 businesses — mostly in Denver’s Elyria-Swansea, where added lanes and new frontage roads will triple I-70’s footprint.

It’s a project that will require feats of engineering, staging and coordination to keep highway traffic moving while nearly 2 miles of a 53-year-old viaduct in that area northeast of downtown are replaced with a significantly widened, below-grade freeway that carries plenty of flood risk. Because of this, controversy over I-70 has enveloped a city storm drainage project plan that would benefit the lowered highway.

In CDOT’s largest concession to community concerns in recent years, officials added plans for a 4-acre parkland cap over the lowered freeway adjacent to Swansea Elementary School.

CDOT chief Shailen Bhatt said Thursday that federal and state officials welcome the chance to defend the project against any legal challenge to widening the six-lane freeway.

And he asserted anew that he sees the project’s hallmarks — one managed express lane in each direction for 10 miles, with another added in a later phase — as the best chance to accommodate the Denver metro area’s growing population within the fiscal handcuffs constraining state funding.

With the Federal Highway Administration’s blessing, CDOT now can move ahead in coming months with a final bid solicitation for four short-listed teams vying for a public-private partnership. The partner will design, finance, build, maintain and operate the expanded highway.

“We didn’t get here quickly and easily. It took many years. We had some false starts on some concepts that we thought would work — and they didn’t work,” said John Cater, the Lakewood-based FHA division administrator. “We listened to what (the community) had to say, came back and came up with the solution that I believe is a consensus-driven approach.”

Not everyone’s happy with it, he acknowledged — perhaps an understatement.

Opposition groups have made several attempts to delay or halt the project, with a lawsuit filed by the Sierra Club over federal air quality standards still pending.

Most recently, opponents submitted input on updated air quality impact projections issued by CDOT during a public comment period that ended Saturday.

“They’re obviously really rushing this through,” said Drew Dutcher, president of the Elyria and Swansea Neighborhood Association, questioning whether those recently submitted comments received any attention. “We think there are very serious problems with this project, from the pollution and environmental (standpoints) to civil rights, and then just as far as our vision as a metropolitan area. We just think this is the wrong way to go.”

Indeed, the timing of Thursday’s announcement was curious in two ways.

Last month, federal transportation officials initiated an investigation of a civil rights complaint filed against CDOT by a trio of community groups, including Dutcher’s, and Earthjustice, an environmental law firm.

The investigation is done, but the U.S. Department of Transportation and the Federal Highway Administration haven’t issued their findings. Cater said Thursday: “We’ve been given an indication that there will be no substantive findings,” which gave his side of the agency enough confidence to issue the I-70 Record of Decision.

That was news to Earthjustice and Dutcher.

The FHA also released its Record of Decision on the eve of a changeover in presidential administrations, from President Barack Obama to Donald Trump.

“Our goal was to deliver this as soon as possible,” Cater said, downplaying the significance of the timing. “We have a team in place in our agency where we have assurance of being able to have signature authority, so it didn’t hurt that we were able to (finish) during this administration, but it didn’t drive the entire process.”

I-70 has faced knocks beyond the immediate communities it will affect for what some critics see as fatal drawbacks.

A coalition that includes Unite North Metro Denver long has pushed for a “reroute” option that would turn I-70 into a boulevard while rerouting highway traffic to the north along interstates 270 and 76. That idea never received serious study from CDOT — and Bhatt dismissed that option again Thursday as a distraction that would flood the city street grid with much of I-70’s passenger vehicle traffic, even if most large trucks take the detour.

Other critics contend that any widening will only spur more traffic as drivers who had avoided I-70 fill up the extra lanes.

Bhatt said “induced demand” is real — but he contends that the managed lanes will offset that with varying tolls aimed at keeping traffic moving at 55 mph even when the free lanes get congested.

“I am confident that the four lanes we put down, and the potential for us to add a fifth lane, will adequately solve our traffic issues for the next 50 years,” Bhatt said.

“Will there still be traffic at 8 a.m.? Probably,” he added. “But we can’t build a system that is wide enough for every road to be a peak-time road. We’ve got to manage, sort of, expectations.”

The I-70 expansion has strong support from Denver Mayor Michael Hancock and other local government leaders across the corridor, though some Denver City Council members have become fierce opponents.

Former Denver City Auditor Dennis Gallagher on Thursday called the project a bad fiscal choice “that can be done a lot cheaper.”

“It’s clear that the city and the Department of Transportation haven’t heard the message of the last election (and that) people are furious that the establishment is willing to screw two minority neighborhoods that have historically been left out so that suburbanites can get through northeast Denver in three minutes less,” he said. “I hope reason will prevail.”

CDOT says it has made 148 commitments and modifications to reduce the impact of the project on Elyria-Swansea and other communities.

The most prominent is the landscaped cover, which will include new street connections across the highway. Others include a 20 percent local hiring target for project contractors, paying to remodel parts of the school, paying for some home improvements in that area to improve air filtration and contributing $2 million toward affordable housing projects.

Diane Barrett, Hancock’s special projects manager, said CDOT’s years of outreach resulted in “some phenomenal plans for our communities that are now going to become reality because of this decision today.”

CDOT also must provide relocation assistance for renters and homeowners displaced by the project — though some community groups have questioned where that assistance will be adequate, given Denver’s rising home prices and high rents.

City Council president Albus Brooks, whose district includes Elyria-Swansea, said he shares concerns about its potential impact on health and quality of life because he lives six blocks from I-70.

But he hasn’t joined the council’s several outspoken opponents in fighting the project.

“This project is bigger than any one councilperson and community leader,” Brooks said. “With the right stewardship and community involvement, I do believe this project could be beneficial. I want to encourage all leaders to remain at the table — especially those who are disappointed in the outcome of this Record of Decision. We all have much work to do.”