WASHINGTON COUNTY HISTORICAL SOCIETY (Washington County, Utah)
Zion National Park
DESCRIPTIONA series of six switchbacks are carved from the canyon floor 800 feet up to the west entrance of the main tunnel.
The main tunnel is 5,607 feet (1.1 miles) long. The tunnel has no artifical lighting.
Window-holes (called galleries) are cut out along the side of the tunnel. These holes provide air flow, light, and impressive views. During construction, they provided places to dump tunnel debris into the canyon below.
There is a much smaller tunnel a ways east of the main tunnel.
HISTORYThe new road through the park, including the Zion Tunnel was begun in 1927.
Engineers used mining techniques rather than traditional tunneling techniques. Construction of the tunnel was considered an engineering marvel and, at the time, it was the longest non-urban road-tunnel in the United States.
The tunnel was finished and opened on July 3, 1930. They held a dedication ceremony on July 4. All of the 48 state governors, except for New York's, were at a conference in Salt Lake City and came down for the dedication.
Today the tunnel is basically the same as it was upon its completion. However, because of the softness of the sandstone through which it passes, much reinforcing has been done and concrete ribs now give added support to the the tunnel's entire length.
Collapse of a sandstone pillar west of Gallery #3 in 1958 broke the top out of that gallery and flushed tons of debris into the tunnel, causing its closure for several weeks. Because of that collapse, the tunnel is now monitored electronically twenty-four hours a day to warn park officials to the danger of a reoccurrence.
In the spring of 1989, the National Park Service began an escort service (traffic control) to allow larger vehicles to pass through the tunnel. When such vehicles need to go through the tunnel, traffic is allowed only in one direction at a time.
On Friday, May 18, 2012, the Zion-Mount Carmel Road and Zion Tunnel were dedicated as a National Historic Civil Engineering Landmark.
WCHS-01121 Photo of work on the Zion tunnel
WCHS-01122 Photo of work on the Zion tunnel
REFERENCESThe Zion Tunnel; From Slickrock to Switchback
Book by Donald Garate
Southern Utah Memories: Zion-Mt. Carmel Tunnel Became a Key Road
by Loren R. Webb, August 18, 2012
National Park Service: The Zion-Mount Carmel Tunnel
Zion Tunnel An Engineering Marvel
Zion-Mt. Carmel Highway, tunnel to be designated historic landmark
Walking Through History At Zion National Park
YouTube videos of the Zion Tunnel:
East to west with some chatting (2:51)
Motorcycle trip through the tunnel west to east, including the road on both ends (2:22)
West to east including the road on both ends (5:01)
West to east with some comments and the road eastward including the second tunnel (7:24)