Tunneling Through the Continental Divide

The Eisenhower Tunnel is an architectural marvel.

The Eisenhower Tunnel is one of the world’s highest tunnels at 11,158 feet. The construction of the 1.7-mile tunnel started in 1968 with a plan to complete the tunnel in three years. Five years later, on March 8, 1973, the tunnel opened to the public.

The tunnel saw many setbacks during construction. The complicated tunnel cost $108 million, requiring more than 1,000 engineers and miners working in three shifts, 24 hours a day, six days a week.

The faultline of the Continental Divide across the tunnel meant more support was needed to protect miners from cave-ins. Despite best efforts, three engineers were killed during construction.

The Continental Divide follows the tectonic plates from Alaska’s Bering Sea to Cape Horn off the coasts of Chile and Argentina. Look for the sign that marks the Continental Divide in the middle of the tunnel.

In 1979, the adjacent Johnson Tunnel opened. Today, the Eisenhower Tunnel runs traffic east, while the Johnson Tunnel runs traffic west. The Johnson Tunnel was more expensive than the Eisenhower, took four years to complete and resulted in four fatalities.

Janet Bonnema Built Much More than a Tunnel
The Eisenhower Tunnel helped pave the way for women’s rights and equal opportunity in Colorado and the nation. When Janet Bonnema applied for a position as a technical engineer in the Eisenhower Tunnel, the employer read her name as “James” on the resume and hired her. When employers, miners and fellow engineers found out she was a woman, they quickly fired her.
Bonnema filed a lawsuit for sexual discrimination against the CDOH under Title VII of the 1964 Civil Rights Act. Bonnema won the case and was able to work in the tunnel taking rock samples and measurements, and creating technical drawings. Bonnema shattered the superstition that women brought bad luck to mines and paved the way for women to work in the construction, mining, and engineering industries.
In 2012, Bonnema was inducted to the Colorado Women’s Hall of Fame. Bonnema passed away in 2008 after a successful career as an engineer.

Today, the tunnel not only connects the Front Range to Exit 205 and beyond, but it’s also a launching point for outdoor adventures. One of our favorites? Seeing wildflowers on Upper Straight Creek trail. From Exit 205, head east and stay in the right lane as you approach the tunnel. Slow down and turn right into the staging area about 0.1 miles west of the entrance to the tunnel. Continue to the right of the tunnel, where you’ll find a road that loops up and around the tunnel’s entrance. Park your car and start your hike beyond the gate. J.R.

Photos from Bill Linfield