Eisenhower Tunnel consists of two tunnel bores. Each are about 1.7 miles long. In total, each measure 48 feet high by 40 feet wide. The true size of the bores is deceptive as much of the space is used for forced air ventilation and water drainage systems.
***This pass is not open to bicyclists, and will require the permission of the Colorado Department of Transportation (“CDOT”).
STAY TUNED working on details. Summer 2019
The approach to the tunnel is steep on both sides of the Continental Divide. Amazingly, the Continental Divide weather patterns can lead to entering the tunnel with a sunny day and exit in a snowstorm.
Georgetown, 13.5 mi. to the east
Silverthorne, 8 mi. to the west
The Eisenhower tunnel is the longest mountain tunnel and highest point on the U.S. Interstate System.
Prior to the tunnel, the only way to the mountainous towns of Dillon and Breckenridge was through Loveland Pass (or the long way around up Hoosier Pass or via Kremling). Ideas to build a tunnel through the Continental Divide began in the 1940s. When construction commenced, the tunnel was known as the Straight Creek Tunnel, for the waterway that runs along the western approach to the tunnel.
The construction of the first bore (westbound), was scheduled to take three years. Construction began March 1968 and finished March 1973. The project suffered tremendous setbacks due to the discovery of fault lines in the mountain, and the machinery was unable to work efficiently at such a high elevation. The fault lines began to slip during construction endangering workers and threatening the stability of the tunnel. Some workers would lose their lives.
“We were going by the book, but the damned mountain couldn’t read,” a frustrated engineer said. It became apparent that the tunnel capacity was insufficient for the volume of traffic. As such, construction on the second bore (eastbound) was expedited, starting in 1975 and completed in 1979.
The tunnel became the most expensive federally aided project of its time. The initial estimate for the Eisenhower bore was $42 million, but the actual cost was $108 million. The cost for the Johnson bore was $102.8 million. There was also an additional $50 million for non-boring expenses.
Although intended for motor transportation, the tunnel also serves an important function of diverting water from the western side of the Continental Divide to the eastern side. Straight Creek watershed delivers over 300 acre-feet of water per year. Much of the water is delivered to the Coors Brewing Company in Golden.