About the Eisenhower-Johnson Memorial Tunnel

Driving west into the Eisenhower Johnson Memorial Tunnel

Tunnel Overview

The Eisenhower-Johnson Memorial Tunnel (EJMT) is a vital connection to safely move people and goods from the eastern slope of the Rocky Mountains to the western slope. This tunnel is the result of more than 50 years of discussion, planning, designing, and construction- with the Eisenhower Bore opening in 1973 and the Johnson Bore opening in 1979. 

Located about 60 miles west of Denver on Interstate 70, EJMT traverses through the Continental Divide at an average elevation of 11,112 feet. When originally opened in the 1970s, the tunnel was not only the highest vehicular tunnel in the US, but at that time it was also the highest in the world. Since then, higher tunnels have been built across the globe.

The facility lies entirely within the Arapaho National Forest and is divided by two counties: Clear Creek County at the East Portal and Summit County at the West Portal. The tunnel and the Continental Divide also separate two watersheds: the Clear Creek Watershed on the east side and the Straight Creek Watershed on the west side. Annual snowfall in the area averages 315 inches (26 feet) from November through April.

EJMT Employees

EJMT is located in the Colorado Department of Transportation's Denver Metro region (Region 1, in Maintenance Section 9). The team that manages EJMT is one of nine Maintenance and Operations sections dedicated to developing and maintaining the best possible multi-modal transportation system for Colorado that most effectively moves people, goods and information. All tunnel employees are trained firefighters, and the tunnel has its own fire truck and tow truck co crews can respond to emergencies and clear crashes in or near the tunnel. Crew members are also responsible for monitoring the air quality levels Inside the tunnel and control the ventilation fans to ensure the carbon monoxide levels are kept low. 

The Twin Bores

EJMT was originally designed as a twin bore tunnel. Construction on the westbound bore (Eisenhower Tunnel) began Mar. 15, 1968, and was completed five years later on Mar. 8, 1973. The Eisenhower Tunnel celebrates a big milestone of "Connecting Colorado for 50 Years" as of March 8, 2023. This bore was originally called the Straight Creek Tunnel, and later was officially named the Eisenhower Memorial Bore.

Construction on the second bore began Aug. 18, 1975, and was completed four years later on Dec. 21, 1979. This eastbound bore was named after Edwin C. Johnson, a past governor and US senator who had actively supported an interstate highway system across Colorado.


Centerline to centerline, the two tunnel bores are approximately 115 feet apart at the east ventilation building entrance, 120 feet apart at the west ventilation building entrance, and some 230 feet at the widest point of separation under the mountain.

The length of the westbound/Eisenhower Bore is 1.693 miles, and the length of the eastbound/Johnson Bore is 1.697 miles (outside, face to outside face of the ventilation buildings).

The average grade of both tunnels is 1.64 percent rising toward the west (rising 1.64 feet for each 100 feet on the horizontal). The westbound tunnel curves slightly to the left, about midway into the mountain. The approach grades are steep, being seven percent on the west approach and six percent on the east approach.

At the circumference, the tunnel shape varies according to the type of rock encountered, from a straight-leg horseshoe pattern to oval—the latter used where rock stress is greatest. Maximum excavated height for the tunnels is 48 feet, with a width of 40 feet. However, when driving through the tunnels, the actual height is not apparent. The exhaust and supply air ducts are above a suspended porcelain enamel panel ceiling, and a drainage system is provided underneath the roadway surface.

Because of the lining inside the portals, drivers travel through a rectangle that is uniform in size and shape and only see the distance from the roadway surface to the ceilings in the tunnels—a distance of 16 feet, 4 inches. However, because of a series of variable message boards mounted from the ceiling, actual clearance is set at 13 feet, 11 inches. The width in both bores provides two traffic lanes of 13 feet each, providing a total travel width of 26 feet.

Tunnel maintenance personnel utilize a walkway that runs adjacent to the vehicle travel lanes. The walkway also provides access between the westbound or eastbound tunnels through three cross passageways, which are spaced at 2,000-foot intervals. 

The ventilation buildings each measure 252 feet in width, 185 feet in depth and 50 feet high. Ventilation stacks stand an additional 30 feet above the buildings.

Other Equipment

At one time, there was a tram car suspended from the wall, a gasoline-powered unit that could travel the length of the tunnel, carrying an attendant. An emergency power system is in place to use as emergency backup, in case of interruption of the commercial source of electricity. Closed-circuit television allows control room operators to monitor traffic flow from the control room in the east ventilation building.