 Construction on the first bore of the tunnel was started on March 15 , 1968 . Construction efforts suffered many setbacks and the project went well over time and budget . One of the biggest setbacks was the discovery of fault lines in the path of the tunnel that were not discovered during the pilot bores . 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 . A total of nine workers were killed during the construction of both bores . Further complicating construction was that the boring machines could not work as fast as expected at such high altitudes , and 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 " . The first bore was dedicated March 8 , 1973 . Initially this tunnel 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 second tube ( the Johnson bore ) , which was finished on December 21 , 1979 . The initial engineering cost estimate for the Eisenhower bore was $ 42 million ; the actual cost was $ 108 million ( equivalent to $ 576 million today ) . Approximately 90 % of the funds were paid by the federal government , with the state of Colorado paying the rest . At the time , this figure set a record for the most expensive federally aided project . The excavation cost for the Johnson bore was $ 102 @.@ 8 million ( equivalent to $ 335 million today ) . 
