Not just a big hole in the ground

Linda Jones

02/08/2007 - You’re being watched every inch of the way as you drive through the Eisenhower Tunnel! Any one of the 52 Colorado Department of Transportation (CDOT) employees assigned to work in the tunnel may be watching on the multiple television sets directed at every part of the tunnel drive. The total excavation in the mountain dwarfs the actual driving tunnel, which is all the motorist sees.

  The full and proper name is the Eisenhower/Johnson Memorial Tunnels, because these are twin bores, but the common term is “the Eisenhower Tunnel”. The tunnels are a vital link in America’s East Coast-West Coast interstate highway system and were a tremendous boost to the infant western slope ski industry when they were completed in the 1970s. Last year 11,092,693 vehicles used the tunnels, a record annual traffic count for the site.

  The tunnels hold the distinction of being the highest vehicular tunnels in the world, with an average elevation under the Continental Divide of 11,112 feet. Because the tunnels cross under the Continental Divide, the watershed-divider for the North American continent, they separate two watersheds, one of which flows into the Pacific Ocean and one into the Atlantic Ocean. Summit County lies on the west side of the Divide, Clear Creek County on the east side, and Arapahoe National Forest covers all the surrounding mountains. The bores are nearly 1.7 miles long.

  At this elevation, and particularly on the Continental Divide, lots of snow falls and the winds often howl their way across America, west to east. Average annual snowfall is 315 inches – over 26 feet. On the eastern approach to the tunnels lies Loveland Valley Ski Area; close to the western side is Arapaho Basin Ski Area.

  The excavation for the tunnels is much larger than the traveling public would suspect. The two traffic lanes in each bore are 13 feet wide, a total travel width of 26 feet, but the excavation is 40 feet wide. The driver sees only from the roadway surface to the ceilings in the tunnels, a distance of 16 feet, 4 inches, yet the excavated height is 48 feet—three times that visible distance.

  All that excavated space drivers never see is used for exhaust and supply air ducts above and a drainage system underneath. The tunnel workers utilize a walkway which runs adjacent to the travel lanes; the walkway provides access between the tunnels through three cross passageways spaced at 2,000-foot intervals. The 52 CDOT employees staff the tunnels 24 hours a day, 7 days a week, 365 days a year.

  The square tan building on the east side is the nerve center for the monitors linked to the surveillance cameras. Video screens, air-quality gauges, vehicle-counting machines and switches to control 28 ventilation and 14 exhaust fans are inside. The tunnel complex has its own sewage-treatment facility, water storage center and two 480-volt generators to power the tunnel’s lights if necessary. The normal power sources are duplicated, connected to the grids on both sides of the Divide, as a precaution against power outages; the generators are merely a backup source of power. A small fleet of firefighting trucks is parked within the complex and  most of the crew on duty at any time are certified firefighters (and also certified paramedics). About three fires annually break out in passing autos.

  From centerline to centerline, the two tunnels are 115 feet apart at the east ventilation building entrance and 120 feet apart at the west and they are 230 feet under the mountaintop. The average grade is 1.64%, rising to the west; the approach grades, however, are steep: 7% on the west and 6% on the east.

  W.A.H. Loveland dreamed of a railroad tunnel under the Divide at this location. In 1881 he organized the Loveland Pass Mining & Railroad Tunnel company with the goal of cutting a tunnel through the range here as a railroad shortcut. In early 1943 a pilot bore of 7 feet by 7 feet for the “Loveland Pass Highway 6 Tunnel” was drilled through at 11,000 feet elevation. The idea at that time was a 5,418-foot-long tunnel to replace the route over the top.

  The final construction – our present twin tunnels – began on the north tunnel on March 15, 1968 and was completed almost exactly five years later on March 8, 1973. Three miners died in the construction of this first bore, and many more died in highway accidents as the 1,000-man force drove mostly from the metro area. The north tunnel, the westbound bore, was originally named the Straight Creek Tunnel, but the name was soon changed to Eisenhower Memorial Tunnel.

  Because six years passed before the second bore was completed, the name Eisenhower became imbedded in the public mind, but the south tunnel, the eastbound, was actually named for Edwin C. Johnson, a past Governor of Colorado and U.S. Senator who was an active supporter of the interstate highway system across Colorado. That bore was begun on August 18, 1975 and completed in a mere four years, on December 21, 1979, with a comparable loss of life.