How They Bored I-70 Through the Continental Divide at 11,000 Feet

How did engineers carry Interstate 70 through Colorado’s Continental Divide at more than 11,000 feet above sea level? This documentary tells the complete construction story of the Eisenhower–Johnson Memorial Tunnel, from the early pioneer bore and repeated failed bidding attempts to the opening of the Eisenhower bore in 1973 and the Johnson bore in 1979. Crews drilled and blasted through nearly 9,000 feet of mountain while fighting unstable fault zones, groundwater, ice, severe winter weather, and crushing rock pressure. A 640-ton steel shield became trapped underground, forcing engineers to adopt a multi-drift excavation system. Above and around the bores, massive portal facilities and 14 ventilation fans at each end were built to control potentially lethal automobile exhaust at extreme altitude. The film also examines the project’s human cost, Janet Bonnema’s fight to work underground as an engineering technician, the first bore’s schedule and cost overruns, and the construction of a second tunnel beside live Interstate traffic. Finally, it explores the continuously operated mechanical system that now carries tens of thousands of vehicles beneath the Continental Divide each day. The Eisenhower–Johnson Memorial Tunnel remains the highest point on the U.S. Interstate Highway System and one of the defining transportation engineering achievements of the American West. #americanconstruction #engineeringhistory #BuiltAmerica