Commuters who rely on Interstate 70 northeast of downtown Denver are still two years from the most jarring moment of the highway’s $1.2 billion expansion project.

That’s when the Grim Reaper will come for the crumbling 54-year-old viaduct between Brighton and Colorado boulevards, the focus of the most intensive work. The first of two major traffic shifts for all six lanes will send cars and trucks to the bottom of a massive, mostly open-air trench that crews will dig in the meantime alongside the old viaduct.

The milestone will mark just the midpoint of I-70’s four-year widening project, with more digging to be done once the viaduct is out of the way. By the end, the entire project will reconstruct a larger portion of I-70 between Interstate 25 and Chambers Road and add a new tolled express lane in each direction along that 10-mile stretch.

But get ready: Construction officially starts in the coming week.

After 15 years of detailed planning, heated debates about whether to re-route I-70, combative lawsuits and still-persistent concerns about environmental impacts, the Central 70 project soon will become as ever-present for commuters as the Denver metro area’s last major urban freeway overhaul — the Transportation Expansion Project, known as T-REX. Finished in 2006, that project overhauled and widened southeast Interstate 25 from Broadway to the suburbs and also installed the southeast light-rail line.

Similar to that beast of an undertaking, the I-70 project is likely to be a grind for residents and businesses near the highway. On tap are local detours and some truck traffic and noisy overnight bridge demolitions. In fact, the lead contractor is still working to obtain a controversial noise limits variance from the city to allow that overnight work, with a hearing now likely in September.

The Colorado Department of Transportation agreed during the project review process to dozens of community concessions, the most prominent of which will be installation of a 4-acre, ground-level parkland cover atop the newly depressed freeway next to Swansea Elementary.

On Friday, CDOT leaders are set to be joined by Gov. John Hickenlooper, Denver Mayor Michael Hancock and other local leaders at a groundbreaking ceremony.

The work will be overseen by Kiewit-Meridiam Partners, the consortium that won a public-private partnership contract both to carry out the project and operate and maintain the expanded highway for 30 years. All told, the costs for CDOT in that 34-year deal total $2.2 billion, according to an analysis last year by The Denver Post, in an arrangement that requires the contractors to hit certain construction milestones and shoulder significant cost risks.

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Hickenlooper, recent CDOT directors and city leaders have stood by the project against recurring community and legal challenges. Transportation officials maintain the project is worthwhile.

“As the region continues to grow at an unprecedented rate, projects like Central 70 are important for providing regional mobility,” said Ron Papsdorf, director of transportation planning for the Denver Regional Council of Governments. “As with any improvement project, there will be challenges during construction, but the region will benefit from improvements along this important corridor.”

In the next month, drivers — and residents and businesses near the highway — will begin to notice varying levels of prep work all along the project zone through Denver and Aurora, including on ramps, frontage roads and below the viaduct. The first highway-widening work is expected late this year, in the eastern area.

Project officials expressed optimism the project wouldn’t be a traffic disaster. During construction, main contractor Kiewit Infrastructure Co. is required by CDOT to keep three lanes open in each direction during the day — the status quo for most areas — though lane shifts and cone zones may slow traffic.

One message drivers will hear: Don’t look for relief on surface streets.

“People need to stay on the highway, because there’s a lot of work on the local streets and you have other city projects that are happening,” said Hunter Sydnor, Kiewit’s spokeswoman. “People are not going to make better time getting off the highway.”

Here are the I-70 project’s basics

The project zone is divided into three distinct sections, each with its own phases of work and timelines:

West section (I-25 to Colorado): Below-the-viaduct, 46th Avenue will close between Brighton and York Street in late August, allowing for the building of a new Union Pacific railroad bridge and work on new street crossings. Digging for the sunken highway section will start north of the viaduct next year, with two phases (before and after the viaduct’s removal). Completion is expected in mid-2022, and work also includes rebuilding the Colorado overpass.

Below-the-viaduct, 46th Avenue will close between Brighton and York Street in late August, allowing for the building of a new Union Pacific railroad bridge and work on new street crossings. Digging for the sunken highway section will start north of the viaduct next year, with two phases (before and after the viaduct’s removal). Completion is expected in mid-2022, and work also includes rebuilding the Colorado overpass. Central section (Colorado to just east of Quebec Street): Full reconstruction along I-70’s current alignment begins in January. Highway widening and rebuilding work is expected to start in the late spring, along with improvements to local cross-streets, and end by late 2020.

Full reconstruction along I-70’s current alignment begins in January. Highway widening and rebuilding work is expected to start in the late spring, along with improvements to local cross-streets, and end by late 2020. East section (east of Quebec to Chambers): The longest section will have the most straight-forward highway widening, plus construction of a replacement flyover ramp from Interstate 270 to eastbound I-70. Prep work on ramps begins in September, and work to widen the highway’s land base starts after November. The entire section, which also includes the rebuilding of the highway bridge over Peoria Street, should be complete by late 2019.

Kiewit-Meridiam Partners plans to install the tolling equipment once all construction is done. Still unclear, though, is whether the new lanes in the east section will be accessible before then.

No doubt, the most complicated work will be the digging of what CDOT calls the “lowered section,” to replace the 1.8-mile viaduct through the Elyria-Swansea neighborhoods.

For one, several cross-street bridges over that section will be built before digging begins.

“We’ll build these bridges on grade,” said Tom Howell, Kiewit’s project manager, who also worked on T-REX. “So you really drill the shafts and everything at grade, build the abutment and put the bridge girders on, plus the deck. And then, once that’s all put together, then you basically dig underneath the structure.”

After the first phase of digging is done, in two years, both directions of traffic will move to the completed portion of the trench. Digging will continue southward after the viaduct’s removal.

When it’s done, the lowered section between Brighton and Colorado will be triple the width of the highway’s current footprint through the area, or about 275 feet, including new frontage roads to replace 46th Avenue. It will have four lanes in each direction (including a toll lane), plus acceleration/deceleration lanes between ramps.

For comparison, project officials say the new width will be about 25 feet narrower than “The Narrows” section of I-25 between Franklin Street and Broadway.

But the project is gobbling up a lot of property. To acquire 56 homes and 17 businesses needed for the project in that area, CDOT said Thursday that it paid out nearly $96 million to buy property and relocate families, including renters.

Night closures and project complexities

Officials from CDOT and Kiewit delved into some of the complexities of managing the project and its impact during a recent briefing for The Denver Post.

Though the highway is expected to stay open during the day, there will be a need for night closures. Per its contract, Kiewit will be limited in the next four years to 10 overnight highway closures and four weekend-long full closures, said Rebecca White, CDOT’s deputy project director.

She said the project office is working with the Regional Transportation District to ensure bus routes wouldn’t be sidelined by detours. It’s also coordinating with about two-dozen employers along I-70, including some who have shifts around the clock, and it’s encouraging commuters who don’t want to drive to take the University of Colorado A-Line, which parallels I-70.

When it comes to construction, Kiewit officials expressed confidence that they were ready for the potential complications of digging the lowered section in parts of a Superfund site and so close to groundwater, both potential hang-ups cited by project critics. Project plans include new drainage systems, and the project also will benefit from underway city stormwater drainage projects.

CDOT has analyzed 300 or so soil samples, and Kiewit says it’s taken more than 1,000. Kiewit officials said that gave them confidence they wouldn’t find large amounts of contaminated soil in need of cleaning or specialized disposal.

”We will have full-time monitors out there as we excavate … in case there’s something we do come across that we, for whatever reason, didn’t catch in the samples,” Howell said.

As for the potential for groundwater to interfere, he said: “At this point in time, our design keeps us above the water table — 3 feet, plus or minus. Our plan is just to make sure our design keeps us up and out of the water.”

Will express lanes provide enough relief?

When it’s all done, what will the I-70 project deliver for drivers?

From cash-strapped CDOT, the answer is a bit of a mixed bag: As vehicle traffic builds on I-70 in coming decades, the new express lanes are projected to slow the growth of congestion in all lanes, but not to make it better than it is now. Today’s volume of 200,000 vehicles a day in the project corridor is projected to increase by 35 percent, to 270,000 a day, by 2035.

But those who want a quicker trip and are willing to pay a few dollars will gain an alternative that promises a more reliable trip, with tolls in the “managed lanes” varying based on congestion to keep traffic moving. They will operate similarly to toll lanes on U.S. 36 and I-25 North, which also means they’ll be free for vehicles carrying at least three people.

There’s still an unfunded second phase of the I-70 expansion, which would have pushed the project price to about $1.8 billion, but it’s on the shelf for now. If funded, it would add a second toll lane in each direction, in part by taking advantage of some of the widening work from the upcoming project.

Denver City Councilman Paul Kashmann, a project skeptic, isn’t so sure the pain of the coming project will be worth it.

He and other council members pushed last year for the city to provide extra money to expand a CDOT program that has equipped nearby homes in Elyria-Swansea with improvements to insulate them from project noise and dust.

But the neighborhood will be ground zero for several big, concurrent construction projects, including the $1 billion city-led National Western Center plan and the continuing reconstruction of Brighton Boulevard. And unlike T-REX, where a lot of work happened down in I-25’s existing sunken section, I-70’s initial work will be at ground level.

“I’m thinking it’s going to be a mess,” Kashmann predicted.

Noise limits issue is still unresolved

Some neighbors in Elyria-Swansea have said they just want the project to get done, after more than a decade of debate. Others, with concerns about air quality and other issues, are still battling CDOT and the contractors.

Kiewit’s nighttime noise variance request could be considered by the city’s Board of Public Health and Environment in September, and it’s shaping up as the next skirmish. Kiewit initially filed for a July hearing, but it quickly pulled back to retool the proposal after neighborhood advocates and Councilman Albus Brooks took it to task for a lack of public outreach.

Drew Dutcher, president of the Elyria and Swansea Neighborhood Association, said he would like to see the appointment of an independent ombudsman with authority to push neighborhood concerns with Kiewit and CDOT.

“The big problem is that in these neighborhoods, we don’t have a CRL,” he said, referring to Kiewit’s lobbying firm. “We don’t have lawyers. We don’t have lobbyists. And that’s what we need.”

Former Councilman Charlie Brown represented some neighborhoods during their battle with Kiewit over the T-REX noise variance request in 2001.

Ultimately, he secured the promise of hotel vouchers for residents on noisy nights, something Kiewit says it already plans for I-70. Howell said the accommodations for T-REX are “the baseline” for the new variance request.

“It was emotional, like everything in this town,” Brown said of the 2001 community negotiations with Kiewit and CDOT. “And it worked out. … Once (I-70) is finished, people will be grateful. I think it will improve the neighborhood.”

Esmeralda Aguilar, 26, and her family won’t be around to find out.

Along with her parents, three siblings and her husband, she had rented a home that was slated for demolition for the project. During negotiations with CDOT that Aguilar called “way harder than I thought,” she and the rest of the family struggled to find a rental elsewhere that could accommodate them all.

Ultimately, CDOT’s $75,000 in relocation assistance covered a down payment on a house in Commerce City — a positive outcome.

But in a bit of irony, Aguilar, who recently had a baby, won’t be able to escape the project. She works as a secretary at a law firm downtown, and her bus commute takes her right through the project zone.

“There’s a couple streets already blocked off by the highway, and that also reroutes the bus,” she said. “Once construction starts happening with I-70, I fear I’m going to have to start leaving two hours early to get to work on time.”