BLOSSBURG - Smoke billows from Mullan Tunnel long after the westbound train begins its tedious descent off the Continental Divide.
The tunnel walls are tarnished raven black, the architecture reminiscent of a bygone era. The passage dates back to the Northern Pacific's steam locomotives, which chugged over the mountain pass beginning in 1883.
Cut under the Continental Divide at 5,548 feet above sea level, Mullan Tunnel is undergoing its first major overhaul since it opened to railroad traffic more than 120 years ago.
Stretching 3,896 feet, the tunnel is the longest in Montana. At less than 13 feet wide, it is also one of the narrowest active tunnels in the country, clearing some freight by less than 3 inches on either side.
A full century after surveyors scouted the route over the main range of the Rocky Mountains, the tunnel remains a vital connector on Montana Rail Link's east-west line between Helena and Missoula. And while it has served the railroad well for years, crews are working against time to keep the route open to traffic and save their equipment from overheating.
"In the course of our study, we determined that structurally, the tunnel had been in existence for more than 100 years," said Dave Cook, director of structures for MRL. "It was time to do something with the tunnel under controlled methods rather than having some kind of an outage that delays our trains."
Headed by L.R.L. of Tillamook, Ore., the $18 million project presents a structural and logistical challenge. When the tunnel was built, it was shored up with timbers, padded with concrete walls, and capped with an arch of red brick, baked and stamped on site by the Switzer brick company.
Bringing the old work down and cutting into the rock takes a steady hand and a keen knowledge of the mountain's geology. Working with supervised precision, crews will blast, cut and chip away more than 100,000 cubic yards of rock and dirt.
Cook said the work will leave the tunnel 5 feet taller and 3 feet wider. Doing so will better accommodate today's large freight trains and protect sensitive locomotives from overheating as they push through the mountain.
"Making it larger gives us a lot more volume of air for the newer locomotives that are electronically oriented," Cook said. "The helper sets were dying because of a lack of oxygen. They have much more horsepower and they need much more air. But they weren't getting that air if they were the fourth and fifth engines in the consist."
Armed with the permits and environmental applications needed for a job of this size, the "Blossburg Station" now rumbles with activity.
Excavators hammer and claw at the mountain above the tunnel's west portal. Trucks bound down an earthen ramp loaded with boulders as big as motorcycles. The radios squawk in the Blossburg pump house, the operation's temporary headquarters.
It is here on the west side of the pass in a meadow surrounded by timber that crews are working to "retreat" the tunnel's entrance 400 feet. The work will remove a large chunk of mountain above, effectively reducing the tunnel's length to 3,496 feet.
The work above goes on in the full light of day. But inside the tunnel, the blackened walls and the lack of light makes for tedious, dirty work. Crews wear respirators, hard hats and boots. Construction lights help guide their way.
Using a rolling line of machinery, crews chisel out the old bricks and cover the tunnel with shockcrete, a primer mixed with aggregate and metal to keep air off the rock. They drill rock bolts into the granite and scratch away the walls to achieve the dimensions specified by tunnel engineers and determined safe by geologists.
"We've got some weathered material, which can be a challenge at times," said Ray Jordan, a tunnel inspector with Jacobs and Associates. "If we have a pocket, I want to make sure we can continue to tunnel in a safe manner to pass trains so that 100 years down the road it's still going to operate."
The railroad was not the first to cross the Continental Divide at this location. Centuries earlier, American Indians used the low-lying pass to access the Great Plains and hunt the buffalo that roamed there.
Not until 1854 did a Caucasian explorer named Capt. John Mullan cross the Divide to develop the pass for travel. Once created, the Mullan Trail connected the steamboat port at Fort Benton with Walla Walla, Wash.
The rutted wagon tracks left by travelers following the trail are still visible if one knows where to look. The Masons held their first Montana meeting alongside the trail less than a mile from here, and Cromwell Dixon landed nearby in 1911, becoming the first person to fly across the Continental Divide. After landing his Curtiss Pusher biplane that September day, Dixon wired New York from the entrance of Mullan Tunnel to spread word of his success.
While history is not hard to find, even up here at this seemingly remote location, it was the Northern Pacific Railroad and its mainline that opened Helena and parts of Montana to coastal cities. But it was not easy going, and carrying the railroad over the Rocky Mountains was not an easy task.
Surveys in 1871 revealed as many 15 practical passes for the railroad, each varying in elevation, ease of approach and complexity of construction. Engineers soon narrowed their list to three passes that included Little Pipestone, Deer Lodge and Mullan.
The Pipestone route at Butte was the highest of the three and because of it, its grades would have been too steep, its route too long. Deer Lodge provided the easiest approach and needed no tunnel. But that route added nearly 40 miles of rail.
While the Mullan route required a long tunnel, it also offered the shortest route. In 1881, it was the option approved by the railroad's board of directors.
Tunnel construction began Dec. 14, 1881. Crews cut trees from the surrounding hills and timbered the tunnel as they went, cutting through long stretches of granite followed by frustrating encounters with softer material.
In 1883, water burst into the tunnel's eastern side. The deluge carried away support beams and filled portions of the tunnel with debris. The washout slowed the tunnel's progress.
"The bad character of the rock and the unexpected labor involved in timbering delayed the progress of the tunnel, and it is not finished at the date of the issue of this book," wrote Eugene Smalley in his 1883 account, "History of the Northern Pacific Railroad."
The workmanship completed by 19th century workers is still visible inside the blackened tunnel. Bricks arch more than 20 feet overhead. The stamped concrete on the portal itself reads "Mullan Tunnel" in big block letters.
But above the portal, 21st century equipment tears into the mountain, sending up columns of dust. The bricks are coming down, as will the portal itself. What was done by hand 126 years ago is now completed by machine, though the work is no less tedious and dangerous.
Contractors from Montana and Oregon are working the site. Some live in trailers alongside the Blossburg pump house. As many as 25 employees are on the job, including blasters, excavators, geologists and railroad officials.
Robotic nozzles, mixers, lifts and drills sit atop railroad cars. The cars are rolled into the tunnel and placed wherever work needs to be done. Pulling 100,000 cubic yards of dirt from the mountain takes time. The material is piled alongside the tracks, creating a berm 20 feet high and just as wide for a distance of several hundred feet.
The freight continues to move as well and that, Cook said, raises the precise scheduling to a whole new level.