Rock On Through -- Zion Tunnel is an Engineering Marvel
The view from one of the Zion Tunnel's windows. Photo by Roger Arave.
By Lynn Arave
AMID the heavenly natural wonders of Zion Park, it's easy to overlook one of man's engineering marvels here - The Zion-Mt. Carmel Tunnel, now 65 years old. It is Utah's and the National Park system's longest underground highway passage and the nation's fifth-longest land tunnel. This 1.1-mile subway and adjoining highway were dedicated on July 4, 1930.
The tunnel and highway, three years in the making at a cost of almost $1.5 million ($937,000 for the connecting highway and $503,000 for the tunnel itself), made easy access possible between Bryce National Park, the Grand Canyon and Zion. In fact, the tunnel cut the Zion-to-Bryce travel time in half and the Zion-to-Grand-Canyon travel requirement by one-third.It was considered to be an almost impossible engineering feat because drilling started in the middle.
The tunnel was made through Pine Canyon to connect Zion Canyon with the higher plateaus to the east. Indians had feared Zion for centuries because of its dark, narrow passageways and called the area "Ioogoon" - basically meaning, "come out the way you come in." The tunnel provided a second access to the park and alleviated this fear of only one entrance/exit.
Zion Canyon became a national park in 1909, and the tunnel came along 21 years later. It was a desirable passageway because it minimized cutting into the mountain-side with more switchbacks for a roadway.
Parunuweap Canyon, further south and directly east of Rockville, was the first route studied for a possible tunnel. However, Pine Canyon was eventually chosen. There was no trail to the top of Pine Mountain, so it was not feasible to do the tunnel survey from above. Surveyors used a special triangulation method to determine the tunnel's path from a foot trail that was some 200 feet below tunnel level.
Although it was the first time this type of survey had been used, the length of the tunnel connections varied by only two inches when finished.
The tunnel contract was awarded to Nevada Construction Company of Fallon, Nev., and work was done in a four-section process that began in 1927. A contractor's camp was made in Pine Creek Canyon and a cable tramway traveled 1,200 feet across and 400 feet up from the bottom of Pine Creek to the camp, then inaccessible by vehicle.
A pilot tunnel was first drilled through the sandstone mountain and then enlarged with an Erie Air Shovel to create a width of 22 feet and a height of 16 feet. The shovel used compressed air, creating less pollution and smoke.
By one report, 10 holes were made in the mountain, which were then connected to create the tunnel.
A scaffold was also used on the side of the mountain. Waste was hauled by narrow-gauge railcars and then dumped through one of the six galleries. (Erosion and revegetation have removed all traces of this dumping.)
Crews were careful not to disturb trees in the area with their blasting in a natural preservation effort. Masonry that was the same color as the surrounding rock was used in the tunnel work. However, the construction, which cost $503,000 for the tunnel itself, also had a higher price. Two tunnel workers died during separate accidents. Johnny Morrison, crew boss, died after inhaling dynamite fumes. Mac McClain was killed when a large rock slid off the switchbacks and pinned him against a power shovel.
It took 146 tons of dynamite to complete the 16-foot-high by 22-foot-wide tunnel and another 35 tons to make the switchbacks. After one blast hurled a 10-pound piece of sandstone inside the camp eating hall, residents began running outside to look around every time a dynamite charge went off.
Carbide lights to see by and compressed air to blow away fumes were initially used in the tunnel. By 1928 electric power brought electric lights and fans. It required 11 months and 12 days to tunnel through the mountain.
The six switchbacks in Pine Creek Canyon that lead up the tunnel from the west are 3.5 miles long and climb 800 feet with a maximum grade of six percent.
The tunnel is not level; it climbs 289 feet (3.3 percent grade) from the west to the east end. The west end of the tunnel is 4,835 feet above sea level, and the east end is 5,124. The Pine Creek Canyon switchbacks to the tunnel begin at 4,000 feet above sea level, and the east entrance to Zion is 1,700 feet higher.
The Park Service built the 8.5 miles of road inside the Zion Park boundaries connecting to the tunnel. In addition, the State of Utah spent $500,000 for its 16.5 miles of road leading from Mount Carmel Junction on the east to the park boundary.
The tunnel and roadway - State Highway 9 - were dedicated in conjunction with the 22nd annual National Conference of Governors that Utah hosted in 1930. The ceremony, on Independence Day, was held inside the tunnel with the galleries decorated with U.S. flags. KSL Radio broadcast a live report from the ceremony.
B.J. Finch, district engineer for the U.S. Bureau of Public Roads, and Horace M. Albright, superintendent of the National Park Service, were both present at the dedication.
Finch said nature had determined millions of years ago where the tunnel would be and noted that it completed a new north-south route through Utah that people could enjoy. He praised the states of Utah and Arizona and the park service for their cooperation on the project.
(NOTE: Riding bicycles through the Zion Tunnel is illegal.)
(-Originally written for the Deseret News, By Lynn Arave, July 16, 1995.)
A view on the far east side of the Zion Tunnel, Checkerboard Mesa.
-NOTE: The author, Lynn Arave, is available to speak to groups, clubs, classes or other organizations about Utah history at no charge. He can be contacted by email at: email@example.com