homeWelcome, sign in or click here to subscribe.login

This Century's Top Ten Construction Projects


This Century's Top Ten Construction Projects
December 9, 1999

Cascade Tunnel bores a rock-solid spot in history

Dates: 1925-1928
Costs: $25.6 million
Contractor: A. Guthrie & Co. of St. Paul, Minn.
Amazing Fact: The tunnel is an 8-mile-long straight bore through solid rock.

Stevens Pass is a favorite route for cross-state travelers, and a popular destination for skiers and hikers as well. But perhaps few people today realize that 74 years ago the pass was the scene of a herculean engineering effort -- one that ultimately sent trains rumbling through solid rock 1,000 feet below the chairlifts.

Cascade Tunnel map
This marvel is the Cascade Tunnel, a straight bore nearly eight miles long that carries trains between Scenic, on the western slope of the Cascade Mountains, and Berne, on the east. It remains the longest in the Western Hemisphere.

Built for the Great Northern Rail way by A. Guthrie & Co. of St. Paul, Minn., the tunnel replaced a shorter one further north. That original Cascade Tunnel, some 500 feet higher than its replacement, was an ongoing expense to the railroad be cause of its switchback approaches and the danger of avalanches.

In taking on the new job Guthrie had to meet a number of challenges, both in engineering and from the railroad itself.

For starters, the contractor had to complete the tunnel in three years -- an unheard-of feat -- and do it for expenses plus a flat fee.

Then, the tunnel had to descend from east to west at a 1.6 percent grade. This made it likely that sub stantial flows of groundwater would gush out, carrying with them the potential for serious delays.

Cascade Tunnel
An eastbound Burlington Northern Santa Fe freight pulls out of the Cascade Tunnel at Berne.
Photo by Lindsay Korst
And, not least, the company had to maintain a large workforce at what was then a very remote site.

Guthrie rose to the occasion. The project was divided into segments, starting with drilling a 622-foot vertical shaft at a site 2.4 miles west of Berne. The shaft intersected the tunnel route, and provided two additional rock faces for drilling crews to attack.

At the same time, engineers pushed a small work tunnel east to meet this shaft. It ran parallel to, but 60 feet south of, the main bore. From it, some 21 connecting passages were cut to the main route, providing 42 more working faces.

The work tunnel had many other uses. It carried workers, materials, air pipes and power lines in, and drained 9,000 gallons of water out every minute.

Workers attacked the rock 24 hours a day, seven days a week for 35 months. When they were finished, on Dec. 24, 1928, some 923,000 cubic yards of rock and earth had been removed.

The project cost $25.6 million, including tunnel construction, relocating the rail line and expand ing electrification. Electric locomotives were used in the tunnel to avoid smoke.


djc home | top | special issues index

Email or user name:
Forgot password? Click here.