Widening I-70 in Denver, Colorado

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Map credit: Map tiles by Stamen Design, under CC BY 3.0. Data by OpenStreetMap, under ODbL.


Status: Completed
Originally reported cost: $1.2 billion

Update for current status:

As of September 2023, the project to widen I-70 in Colorado has been completed.

Update from Highway Boondoggles 4, 2018:

In January 2017, the Federal Highway Administration gave its final approval to the Colorado Department of Transportation’s (CDOT) I-70 reconstruction and expansion project. The approval clears the way for CDOT to use federal funds to widen I-70 between Brighton Boulevard and Tower Road, a 12-mile stretch of road estimated to cost $1.2 billion, with one new, tolled express lane in each direction.

Construction of the project is expected to start in 2018 and will require the destruction of 56 homes and 17 businesses in the surrounding neighborhood. But the highway still faces considerable local opposition.

Residents claim the expanded highway will worsen air quality in an area already affected by poor health outcomes closely linked to air pollution from transportation. A recent study showed that the 80216 zip code, which is home to two neighborhoods around the I-70 project area, had elevated levels of pollution compared even to parts of Los Angeles. CDOT argued that moving part of the currently elevated portion of the roadway below street level with a park over it compensates for the negative impacts of the road. However, the park only covers a small portion of the expansion near Swansea Elementary School and concerns remain regarding highway pollution rising on either side of the park.

Original story from Highway Boondoggles 2, 2016:

The need to tear down the viaduct carrying I-70 through the center of Denver is clear. The bridge, which was built in 1964, first had detectable cracks in 1981. Since then, the bridge has required many repairs. A major 1997 project installed rods intended to reduce cracking. In 2005, the weight of vehicles on the viaduct was limited in hopes of extending the bridge’s life. But the bridge continued to crumble. By 2010, the bridge was considered “structurally deficient,” a federal designation indicating significant problems in its structure.

A $30 million maintenance project in 2010 was expected to give the viaduct another 10 to 15 years of service. But just four years later, the Colorado Department of Transportation announced that some of the work done in 1997 was failing. The repairs themselves needed to be repaired.

The viaduct is also an eyesore whose removal has been sought by the local community for many years. Since it was built, neighbors have complained that it divides their community, which is one of Denver’s poorest.

The Colorado Department of Transportation (CDOT) has proposed to replace the viaduct with a trench for the highway, and partially cover the road with a park. In September 2015, CDOT put out a formal call for private companies willing to finance and build the project.

However, CDOT is also proposing to widen the highway. Originally, CDOT wanted to widen a section of I-70 from I-25 to Tower Road to 10 lanes, up from four- and six-lane segments today, for a total cost of $1.8 billion. Without enough money, the agency scaled the work back to just the area around the failing viaduct, for a cost of $1.17 billion. But its plans to widen the road remain.

There is another major step CDOT could take to reduce the cost: It could decide not to widen the highway.

The agency says in an online fact sheet that the additional cost of expanding the highway from eight lanes to 10 would be “very modest.” Without detailed evaluations of six- and eight-lane options, cost comparisons have proven difficult.

In 2008, however, CDOT provided the savings associated with a narrower highway. Its original Draft Environmental Impact Statement estimated that building an eight-lane trench instead of a 10-lane one would save $58 million, in part because of reduced need to acquire additional private property on which to dig the trench, but also because of reduced construction costs. Since then, CDOT has done no additional cost analysis on a narrower project that has been made readily available to the public.

Perceived need for highway expansion is already under scrutiny in Colorado. Expert reviewers from the American Planning Association’s Transportation Planning Division suggested in October 2014 that CDOT consider options for I-70 expansion with fewer than 10 lanes, because the state’s review process had not yet done so. Their report had several criticisms of the existing proposal, including:

  • CDOT did not evaluate options with fewer than 10 lanes, instead focusing on one that would “maximize rather than minimize impact on the abutting . . . neighborhoods.”
  • In examining the options it did evaluate, CDOT used an outdated traffic modeling system, which had been supplanted in 2010. That old system assumes that people won’t change their travel habits when using routes that are commonly congested, and does not account for the increased traffic created by highway expansion projects.
  • CDOT also used an out-of-date model for determining how highway expansion projects drive development and land-use decisions, which in turn influence traffic levels. The department erroneously assumed land-use patterns would remain the same whether the highway was expanded or not; had CDOT properly incorporated the effects of highway construction on development and resulting traffic, it would likely have found worse traffic outcomes than it did.


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