Project: I-70 Glenwood Canyon

The highway through Glenwood Canyon was the final section of I-70 to be constructed. It replaced a dangerous, two-lane highway built in 1938. The project completed the original U.S. interstate highway system. With funding approved, the original plan was to blast into the canyon side to create a 4-lane highway. However, environmentalists lobbied to protect the natural surroundings and ultimately a new construction technique was used to deck the east and west bound lanes, minimizing disturbance to the canyon. This technique was called balanced cantilever construction and consists of pre-fabricating a section of the bridge and lowering it in from above instead of building it up from below. After the bridge column is built and put into place, a gantry crane is positioned atop the column and is used to fill in the gap between bridge sections outward from the column also using pre-cast segments.

Despite special efforts to minimize ecological impacts, several environmental groups actively sought to stop construction. The Supplemental Environmental Impact Statement (EIS) conduced in 1983-84 was challenged in local courts in 1984 when the Colorado Open Space Council and the Sierra Club sought a restraining order to stop construction, resulting in a temporary injunction. The case was brought to federal courts and was settled when federal judge rejected the plaintiff's arguments but required contractors to disturb as little of the canyon as possible. The project included construction of over 40 bridges and viaducts, five tunnel bores and 15 miles of retaining wall, for a total of 12 miles of roadway. The highway was completed in October 1992 at a cost of $737 million (2007 dollars). The federal government funded over 92% of the project.

One of the tunnels houses facilities for traffic management, maintenance, and emergency response services. The corridor also has four full-service rest areas, a bicycle path running the canyon's entire length, and special facilities for launching rafts, boats, and kayaks.

I-70 in Glenwood Canyon is a model of environmental preservation, safety, and mobility, aided by local citizen involvement and good planning. The community became involved during the early stages of planning and design in the 1970s, and encouraged CDOT to include recreational facilities in the project's overall design. Local residents now state that the canyon is safer, cleaner, and more accessible than before the highway was upgraded to an interstate. Several other government organizations were involved with the project, including the Army Corps of Engineers, the Colorado Division of Wildlife, the Bureau of Land Management, and the Forest Service. The project won more than 30 awards, including the 1993 Outstanding Civil Engineering Achievement Award from the American Society of Civil Engineers.