Colorado DOT and Kiewit Connect Communities with $1.2B Central 70 Project
From Viaduct to Park: Colorado DOT and Kiewit Improve I-70 Corridor with the State’s Largest Infrastructure Project to Date
Aiming to decrease congestion and improve safety and air quality, the Colorado Department of Transportation’s (CDOT) largest infrastructure project ever – the $1.2 billion Central 70 Project – will reconstruct a 10-mile stretch of Interstate 70 in Denver.
“It’s an aging viaduct, a large bridge built in the early 1960s, and the bridge is becoming structurally deficient,” says Jennifer Nelson, Central 70 Construction Manager for CDOT.
The current viaduct runs above city streets and railroad crossings. The partially covered road should reduce noise and improve air quality for nearby neighborhoods, where more than 22,000 people live. The corridor also contains thousands of businesses.
The public-private partnership project will relocate about 2 miles of the interstate 30-feet underground, widening the other 8 miles, rebuilding the local road that currently runs below the viaduct, adding shoulders and a new express lane in each direction, removing the existing 54-year-old viaduct, and building a 4-acre park above the interstate.
“The park alternative was chosen after multiple community outreach meetings,” Nelson says. “The park will reconnect communities on the north and south side of the park.”
Two local streets on both sides of the park will cross above the highway. The park features a small amphitheater, a sports field, playgrounds, a splash park, and space for food trucks and concerts. It is adjacent to an elementary school, which will use the park for recreation during school hours. It will be CDOT’s first park above a highway. However, similar park projects have been completed in Dallas and St. Louis.
“The park will help with air quality and keeps emissions low at the vehicle level,” Nelson says.
CDOT chose Kiewit Meridiam Partners of Denver from a short list of four teams to design, build, finance, operate, and maintain the Central 70 Project in August 2017. The department considered it a way to speed completion of the project. The team’s approach to the project will shave a full season off of the originally planned schedule. WSP Global of New York serves as the design partner and Roy Jorgensen Associates of Buckeystown, Maryland, as lead operator.
“We went with the P3 financing model, so Kiewit Meridiam Partners will help finance the project,” Nelson explains. “They will be paid availability payments for 30 years.”
CDOT will collect the tolls on the new express lanes and will own the infrastructure.
Design began in January 2018 and construction in August 2018. Crews are working through the winter. The project is scheduled for completion in 2022.
Kiewit must relocate more than 1,000 utility lines. Pipes and cables had run under the local roads. Now, Kiewit will move 20 miles of storm sewer, 3 miles of water lines, 3 miles of sanitary sewer and some other utilities.
During preconstruction, Kiewit conducted more than 1,800 soil bores to assess soil conditions in the corridor.
“It helps with efficiency to know the soil conditions,” Nelson says. “Once they start digging, they already know the soil characterization.”
The soil boring also addressed community concerns that the dirt might contain contaminates, which would be kicked up during construction, but nothing hazardous was found.
The new highway will pass below the Union Pacific Railroad and BNSF tracks. The tracks will be put on bridges to go over the interstate. Temporarily, crews will transfer the railroad tracks to two separate shoo-fly bridges off the current alignment, and then will build bridges where the tracks will ultimately go and dig underneath the tracks for the interstate. Union Pacific has a representative on site daily, and the team meets weekly for a three-week look ahead at the schedule. “It’s very collaborative,” Nelson says.
One of the innovations Kiewit brought to the project involves the city streets that will pass over the lowered section of the interstate. The company is building the bridges at grade, including the concrete girders and decking, and then will dig out from underneath them, allowing the bridge to appear.
“It appears to be a regular road, but columns and shafts are installed in the ground,” says Matt Sanman, Public Information Officer at Kiewit in Denver. “We remove the dirt after to minimize impacts and duration.”
Another innovation involves drainage from the highway. Drainage was originally designed by CDOT to be lower than the road, but the Kiewit team redesigned it with a pump station at one end of the lower section.
“It allowed us to raise the highway above the water table, so environmental impacts and concerns were eliminated,” Sanman says.
CDOT estimates that change also reduced the amount of soil disruption by 10,000 truck loads of dirt.
The park will be constructed as a wide bridge and use the pump station for water that feeds onto the highway, Sanman explains.
“It’s the same as any other bridge, with a lot more girders and bridge deck,” he says.
Kiewit designed the project to require only two major traffic switches on the interstate. Crews will build to the north of the viaduct, then when that is ready for traffic, the company will shift traffic to the new lower road and demolish the viaduct. Current traffic on the viaduct has not been affected by the construction, Nelson says.
Moving forward, three lanes in each direction must remain open from 5:30 a.m. until 8 p.m., with periodic lane closures at night.
“The phasing of the project set us apart,” Sanman says. “There are major cross streets that cannot be impacted. We will build those bridges in halves. We will build the widening to the east or west and build the other half.”
The project team also has partnered with the Northeast Transportation Connections to assist with mobility options, including offering shuttle services, bicycles, and bus passes to local residents.
As Kiewit crews excavate the lower section, the soil will be taken to other areas of the project and for other projects.
“Our goal is to minimize wasted dirt that ends up in a land fill,” Sanman says. “We’ve tried to use it in other areas of the project to build up walls, and for other projects in the area to use it as efficiently as we can.”
Benefiting the Community
Kiewit Meridiam Partners committed to hire at least 20 percent of its workforce from the community, and it will contribute through its foundation $1 million for student scholarships and other community programs.
The team has replaced windows and doors at the elementary school and provided some homes near the road with air conditioning and storm windows. Additionally, it is providing funding for affordable housing and fresh food access.
Kiewit is required to monitor and control dust and noise during construction so that neither go above approved limits. The project team has installed four air-quality monitors along parts of the project area to monitor for particulate matter levels to ensure that dust caused from construction work does not exceed 135 micrograms per cubic meter of air.
Additionally, Kiewit must use equipment that meets the latest EPA standards. CDOT is requiring all equipment be Tier 4 or higher. The equipment also features GPS to ensure accuracy, Sanman says.
Kiewit, CDOT, and other project partners are working closely and collaboratively to bring this innovative and one-of-a-kind projects to a successful completion.
- Owner: Colorado Department of Transportation
- Design, Build, Finance, Operate, and Maintain: Kiewit Meridiam Partners of Denver
Photos courtesy of Kiewit