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Home arrow Working with Section 106 arrow ACHP Case Digest arrow Summer 2005 arrow Colorado: Expansion of the I-70 Corridor
Colorado: Expansion of the I-70 Corridor

Agency: Federal Highway Administration

Western Colorado’s Interstate 70 is the major east-west corridor between Denver and many Colorado mountain communities and ski areas. The highway cuts through several historic communities, including the Georgetown-Silver Plume National Historic Landmark and the Hot Springs Historic District in Glenwood Springs.

The Federal Highway Administration and the Colorado Department of Transportation are considering increasing traffic lanes or adding rail or bus service to I-70 to reduce congestion and improve mobility.

Any of the plans, however, will likely have direct impacts on some historic buildings and structures as well as noise and visual effects on the area’s historic districts.

Interstate 70, Clear Creek County, Colorado (photo: Colorado Preservation Inc.)
Interstate 70, Clear Creek County, Colorado
(photo: Colorado Preservation, Inc.)

The Federal Highway Administration (FHWA) and the Colorado Department of Transportation (CDOT) are reviewing proposed improvements to 144 miles of Interstate 70, which cuts through five counties and stretches from Denver to mountain communities and ski areas in western Colorado.

These include historic mountain communities such as Georgetown-Silver Plume, which, as a National Historic Landmark, includes 384 historic properties and the Georgetown Loop railroad grade that runs between the two towns and was considered an engineering marvel of the late 19th century.

I-70 also goes through the Idaho Springs Commercial District and Hot Springs Historic District in Glenwood Springs, which was developed between the 1880s and early 1900s as a resort. In addition, the I-70 corridor mountain communities in Clear Creek County are historically significant for their association with the development of the mining industry in Colorado.


CDOT has prepared a Tier I Programmatic Environmental Impact Statement (PEIS) to develop alternatives to reduce future congestion and improve mobility within the mountain corridor of Interstate 70.

The PEIS was published for public comment in December 2004, and FHWA and CDOT anticipate reaching a decision on the expansion project that may include a combination of increased traffic lanes or increased rail or bus service. Any of the alternatives under consideration will likely have direct impacts on some historic buildings and structures, as well as noise and visual effects on the historic districts.

Under the Section 106 review process, FHWA and CDOT are developing a Programmatic Agreement (PA) that provides for phased consultation with the proposed project’s many consulting parties, defining their roles and potential mitigation measures and identifying issues that need to be addressed in the design of each section of the project.

Consulting parties to the project include the ACHP, Colorado State Historic Preservation Officer, affected local governments, the National Trust for Historic Preservation, Colorado Preservation, Inc., the Denver Landmark Preservation Commission, and historical societies for Eagle County, Georgetown-Silver Plume, Mill Creek Valley, and Idaho Springs.

Some of the consulting parties are concerned about the effects that widening I-70 will have on the setting of their communities, especially visual and audible impacts. Colorado Preservation, Inc., has identified the historic communities along the I-70 corridor expansion project as one of Colorado’s Most Endangered Places for 2005.

In 2004, FHWA initiated consultation with the ACHP and other parties to discuss ways to complete consultation on the Tier I document. In January 2005, the ACHP notified CDOT and FHWA that it would participate in consultation, and it submitted comments on the PEIS in June 2005.

CDOT has developed a conceptual draft PA for completing consultation regarding effects to historic properties during Tier II, the design phase of project development, and will meet with the ACHP and other consulting parties in August 2005 to further develop the PA.

Staff contact: Carol Legard

Updated August 30, 2005

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