The idea for a tunnel under Loveland Pass existed since at least the 1950s.
William A.H. Loveland had an idea of a tunnel under the divide in 1867, but instead got the wagon road now known as Loveland Pass built. Serious discussion began when the state of Colorado lobbied for the Interstate Highway System to route a transcontinental highway across Colorado. After a round of negotiations with
Utah officials, it was decided the best option was to follow the US Route 6 corridor. Engineers recommended tunneling under the pass, rather than attempt to build a route across conforming to
Interstate Highway standards. named for the waterway that runs along the western approach to the tunnel. Before the tunnel was dedicated, it was renamed to honor Dwight D. Eisenhower and Edwin C. Johnson. The original Pioneer bore to access the two larger bores was "holed through" in late 1964, after fourteen months. Construction on the first bore of the tunnel was started on March 15, 1968. These faults began to slip during construction and emergency measures had to be taken to protect the tunnels and workers from cave-ins and collapses. Despite the best efforts of engineers, three workers were killed boring the first tube and four in boring the second. Further complicating construction, the boring machines could not work as fast as expected at such high
elevations and so the productivity was significantly less than planned. The frustration prompted one engineer to comment, "We were going by the book, but the damned mountain couldn't read." Initially, the northern Eisenhower bore was used for two-way traffic, with one lane for each direction. The amount of traffic through the tunnel exceeded predictions, and efforts soon began to expedite construction on the southern bore. Construction began on the eastbound Edwin C. Johnson tunnel on August 18, 1975, and finished on December 21, 1979. The initial engineering cost estimate for the Eisenhower bore was $42 million, but the actual cost was $108 million (equivalent to $ million in ). Approximately 90% of the funds were paid by the federal government, with the state of Colorado paying the rest. At the time, it set a record for the most expensive federally aided project. The excavation cost for the Johnson bore was $102.8 million (equivalent to $ million in ). Not included in the figures is about $50 million in non-boring expenses during the construction of both tunnels. Upon opening, it became the highest-elevation tunnel in the world, taking the title from the
Salang Tunnel in Afghanistan. The tunnel's construction highlighted issues relevant to the
feminist movement. When
Janet Bonnema applied for a position as an engineering technician with the Colorado Department of Transportation she was given an assignment on the Straight Creek Tunnels project. Her supervisor misread her resume and thought that he was hiring "James." When the supervisor discovered that the department had hired a woman, she was tasked with doing support work from the office. There was opposition to a woman entering the construction site. One supervisor stated that if she entered, "Those workers would flat walk out of that there tunnel and they'd never come back." The workers, most of whom had a
mining background, expressed a common superstition that a woman brought bad luck to a mine. One worker insisted, "It's a jinx. I've seen too many die after a woman was in the tunnel." Bonnema sued the department for the right to work inside the tunnel. She countered she was in better shape and more agile than most of the men who were working on the tunnel. Emboldened by the passage of an equal rights law in Colorado, she finally entered the tunnel, with an entourage of reporters, on November 9, 1972. Some workers walked off the job, and at least one of them yelled, "Get those women out of here." In November 2023, CDOT opened an updated operations center and new garage bays at the tunnels.
Plane crash during construction On Friday, October 2, 1970, during the tunnel's construction, workers constructing the tunnel were among the first on scene of a plane crash that had occurred less than northeast of the east portal. A
Martin 4-0-4 charter aircraft, one of two carrying the
college football team of
Wichita State University, crashed just north of the highway (). Of the 40 passengers and crew on board, only nine survived. The team was on its way to a game with
Utah State University in
Logan and had recently refueled at Denver's
Stapleton International Airport. The plane carrying the team's starters departed Denver and traveled a poorly planned scenic route. The other plane, carrying reserve players, followed the original route and landed safely in Logan. ==Water diversion==