For 57 years, drivers on Interstate 70 have traveled through a two-mile stretch of northeast Denver on a hulking, increasingly crumbling highway viaduct that towers over the neighborhood below.
That mass of concrete and steel is about to come down. As it’s torn apart piece by piece for 1.8 miles in coming months, drivers who have navigated more visible roadwork elsewhere on the Central 70 project will finally get an up-close look at the brand-new stretch of highway built between Brighton and Colorado boulevards.
Starting May 24, they’ll drive on it.
The upcoming traffic shift — dubbed the “Mile High Shift” by the Colorado Department of Transportation — will bring a new experience nearly three years into the project. Vehicles will descend about 25 feet below ground level on a mostly open-air roadway built north of the viaduct. They’ll pass through a 1,000-foot tunnel that CDOT expects will cause unfamiliar drivers to slow down until they get used to it.
“We believe that a lot of folks don’t understand what we’ve built adjacent to I-70 next to the viaduct,” said Bob Hays, CDOT’s Central 70 project director, during a recent tour of the new “lowered” section. “We understand this is going to be a change. We understand that there’s going to be a learning curve associated with driving through this.”
The west section is home to the most complex work on the Central 70 project, which is widening I-70 for nearly 10 miles between Interstate 25 and Chambers Road in Aurora. A tolled express lane will be added in each direction, with a second toll lane possible in a future project.
The traffic shift marks the most significant milestone of the $1.3 billion project, which has weathered delays, added costs and other setbacks. At least 18 months of construction is left to go.
For residents and businesses in Denver’s Elyria-Swansea neighborhood, long bisected by the viaduct, the demolition work in coming months will be some of the noisiest and invasive of the project.
Here is a look at what’s coming.
What drivers can expect
CDOT will close I-70 next weekend to prepare for the traffic shift and route the six lanes in either direction into the new lowered section. The highway will close between Washington Street and Interstate 270 from 10 p.m. May 21 through 5 a.m. May 24.
When it reopens, drivers will travel through just half of the final highway west of Colorado Boulevard — the other half can’t be excavated and built until the viaduct is gone. For the next 14 months or so, both directions of traffic will share the eventual westbound side, with the existing six lanes maintained.
Hays says each lane will be 11 feet wide, the same as on the viaduct and in the construction zone to the east — though narrower than the modern 12-foot interstate standard that I-70 will have once construction is complete. When the eastbound side opens in late summer 2022, he said, both sides will have room for full-width lanes, including the new express lane, and shoulders — spacing that should make the tunnel section appear less constraining on approach.
Until then, travel will be about as tight as it’s been atop the viaduct.
Drivers will notice dark-blue accents on overpasses and embedded artwork in sections of the concrete sidewalls, both resulting from community workshops that CDOT organized.
The 1,000-foot tunnel, topped by box girders set side by side, will be replicated on the eastbound side, carrying traffic beneath a planned 4-acre parkland cap next to Swansea Elementary. Plans call for a full-size soccer field and amenities including an amphitheater with a stage and lawn.
While excavating the lowered section, crews have encountered expected contaminants, including old utility ducts wrapped in asbestos, and the demolished old Swansea school, which was buried on site. They’ve also encountered fossils of animals that included a camel dating back to the Ice Age.
What neighbors can expect
Residents living near the project zone long have experienced wall-rattling racket, sleep-disrupting vibrations and ever-present dust, though project-provided retrofits have reduced some of the impact.
“I’m just ready for it to be over,” said San Juana Romero, 32, whose family had lived mid-block on Fillmore Street prior to the project.
After CDOT condemned dozens of properties to make way for I-70’s new lowered section, Romero’s house is now on a corner, across 46th Avenue North from the highway. Kiewit Construction says it’s responded quickly to noise complaints and monitored vibrations, but Romero says her many complaints have resulted in little relief. She began working a night custodial job, she said, since she couldn’t sleep anyway.
The disruption is about to get worse. While it will take until late summer to bring the viaduct all down, Hays and other project officials say demolition will focus on one- or two-block sections so that work is over within two weeks in a given area.
Crews will use jack-hammers and mechanical “munchers” to break apart the concrete and steel. Above new cross-street bridges built in anticipation of the lowered section’s expansion, cranes will lower larger pieces of the viaduct to the ground to be broken up.
“This will be a very surgical process,” Hays said — though still a noisy one. Netting akin to that used at a driving range will be hung south of the viaduct to catch anything that falls near buildings, he said.
Most of the demolition will happen during daytime hours, but Kiewit plans overnight work for portions over busy streets. Under its noise variance from the city — which is up for renewal in late summer — Kiewit must offer hotel vouchers to the closest residents on those nights; a spokesman says it will do so during the upcoming weekend closure, too, as initial demolition work gets underway.
Dust is inevitable, and CDOT says mist-sprayers on the viaduct and water crews on the ground will help keep it out of the air.
Both the contractors and the Denver Department of Public Health and Environment will monitor several sensors set up in the area for particulate readings. DDPHE also will send samples from air filters for lab testing for lead and other metal content that could be a concern.
“From an air quality standpoint, that’s what we’re planning — four (sensor) sites within the vicinity of the project that will give us a large amount of real-time data,” said Gregg Thomas, the director of DDPHE’s Environmental Quality Division, adding that he’s optimistic about the measures in place.
Project is about 70% done, director says
The upcoming traffic shift should have happened in the second half of last year under the original schedule. Completion of major work is still projected by the contracting team, Kiewit-Meridiam Partners, in February 2023 — nearly a year behind the original plan but five months late under a more recent schedule.
But the team has reined in some delays that stemmed from design work on a railroad bridge. Its leaders and CDOT still hope to reach the “substantial completion” milestone by the end of 2022.
With 70% of work now complete, by the project director’s approximation, the viaduct demolition marks the last major hurdle.
“Like any large project, frankly, we had some challenges out of the gate,” Hays said in an interview. “We’ve really found our stride. Whether it’s the east segment, which is substantially complete, the central segment – which will be substantially complete in a September/October type of timeframe — or this (the west section), we are really moving in a great direction.”
Though the other sections will be done by late this year, CDOT says it won’t allow traffic into the new express lanes until the west section is in its final configuration in late 2022. Use of them will be free during a test period for the tolling equipment.
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