The bridge over the Nenana River near the community of Ferry was built in 1925 and is 482 feet long. Replacement of a bridge pier and stabilization of flood-damaged riverbanks is expected to be complete by February 2019. Photos courtesy of Steve Rowe, Swalling General Contractors
Six years ago, a stronger-than-normal high pressure system over the northeast Pacific altered the path that storms usually follow, causing storms to detour into Alaska and, eventually, to wash out a 500- foot section of the Alaska Railroad near Talkeetna.
Farther north, torrents of rain drenched the Alaska Range and swelled the Nenana River, which drains the north side of the range. Currents that previously flowed around the large concrete central pier of the Alaska Railroad Corp.’s steel truss bridge near the whistle-stop community of Ferry shifted.
“The pier was originally designed to run parallel with the current. With the major flood event, the river channel alignment changed, and now the current runs in more of a transverse flow, which caused a major scour event and threatened the foundation of the pier,” said Swalling co-owner Paul Swalling.
In January, Swalling General Contractors began work on a $14 million collaboration with the Alaska Railroad to replace the pier where the current had scoured a hole in the riverbed, remove an adjacent old pier and stabilize areas where water had started eroding the riverbanks. The project used funding from U.S. Federal Emergency Management Administration disaster relief (75 percent) and Alaska Department of Homeland Security and Emergency Management (25 percent).
The 93-year-old, three-span, 482-foot bridge is near Mile 260 Parks Hwy. It carries the Alaska Railroad’s mainline track and communications utilities. About two passenger trains and six freight trains cross the bridge each day in peak season.
The original bridge has held up in some pretty challenging conditions, Swalling said. It’s the second bridge that spanned the river at Ferry; the first washed out after fewer than 10 years of service. Swalling said an old pier that is a remnant of the first bridge would be removed from the river as part of this project.
The railroad had considered constructing a new bridge or permanently or temporarily realigning the mainline track but decided against those alternatives due to cost, potential system disruptions and feasibility. “The current steel spans have substantial remaining service life,” the Alaska Railroad noted in a fact sheet.
“The project will benefit rail-based commerce and overall rail customer service as well as avoid the much higher costs of responding to an emergency track outage if necessary actions are not taken,” according to the Alaska Railroad.
“We aren’t replacing the bridge itself,” co-owner Steve Rowe said. “That’s staying in place. We’re holding it in place and replacing the foundations underneath.”
The process began on a 4-by-10 whiteboard once the bid was awarded in summer 2017.
“Essentially it’s everybody in a room, everybody with their own talents, working through logistical issues,” Rowe said. “You just start at the beginning, start out saying we know we need a trestle — that’s 100 truckloads to get up there. We need this many guys. Where’s everyone going to stay, all the equipment we’ll need, where we’ll put it, who’s going to get you fuel?”
Crews are going to use cranes that weigh 160 to 220 tons for handling the drilled shafts, 100-foot-long pipe that’s 8 feet diameter. At a peak of 1,500 gallons of diesel a day, it was crazy how much fuel we used.”
The project required permits from the Environmental Protection Agency, the Alaska Department of Fish and Game and U.S. Army Corps of Engineers, with site visits. Then there was getting power to run everything.
“Golden Valley Electric ran us our own feed, off the main power line, which required installing our own pole for the project,” Rowe said.
The crews couldn’t get access underneath the bridge structure itself with cranes and other large equipment needed to work both sides of the bridge to install the four drilled shafts: “We had to go back up the track a half mile from the bridge itself to a crossing point, cross over, and create a new road on the along the Alaska Railroad Right-of-Way to get down to the other side of the bridge so we could get back and forth around to both sides of the bridge.”
The project challenges started “spiderwebbing” out as Swalling team began plotting where they would need to get equipment and material to work locations.
“OK, I need a 220-ton crane; I need it here, but it’s 25 feet wide and the road’s only 17 feet wide,” Rowe said. “Now you step back and say, ‘We need to widen road, and then we’re going to move the crane there.’ You work down each scope as best you can, from start to finish, and it naturally starts leading you every which way until it hits a point that you think you’ve found it all.” Then he laughed: “But you know honestly in these jobs, you always miss something.”
“That’s the great part about working with clients like the Alaska Railroad — especially in a collaborative effort,” Rowe continued. “Nobody’s perfect, but we try to find every potential issue we can beforehand. Sometimes things can spiderweb into six different issues, and then you’ve got to bring it all back down to the one answer. It takes a lot time.”
In January, 140-plus semi-trucks laden with trestle and other equipment and materials journeyed to Ferry from Tok, Valdez and Anchorage.
An Alaska Railroad train passes over the Nenana River on trestle used during a project to replace a damaged pier at a bridge near the community of Ferry.
The first task was getting the project site configured to receive the truckloads of material and equipment required for the project, followed closely by gaining access to the work location via temporary access road and work trestle to enable the SGC crews to install the 8-foot drilled shafts.
Pushing to get the drilled shafts in place before breakup, Swalling said the crew worked around the clock for more than two months. During breakup in April, workers had to keep sheets of ice flowing down river from slamming into the trestle.
“We were going out there with a ditch witch, cutting channels into the ice to where, when the ice broke free, the center channel would open up right away with the flow moving away from the trestle,” he said. “We had about four days there where we sat on the end of the trestle with an excavator and the arm down pushing the ice away from the trestle and letting it flow downstream. Then it melted out, and it was fine.”
Currently, workers have been waiting for water levels to drop low enough to pour the concrete caps for the concrete-filled shafts. “After winter, the water level rise up,” Rowe said. “You have that point right before the river freezes, when the water level hits its lowest out there, to where it’s 3 or 4 feet deep in those sections. Right now, it’s running at 10 feet or more in certain sections.”
Rowe said that sometimes on jobs that are in remote areas, “You find the guy who’s lived in the cabin for 30 years … and you ask him, ‘What’s the river do every year?’ And usually nine times out of 10, they have better information and intel than anybody or any machine or any computer out there. Go figure, the year we go out there, he’s like, ‘Yeah, I haven’t seen the water stay this high this long in like 22 years.’” Rowe laughed: “Well, yeah, that’s how it usually goes when we go to work.”
Rowe said in early August that “a few days ago was the first time that our bottom soffit supports that are going to hold the concrete forms came out of the water. They’ve been under water for the last two months; we have been waiting for it to get low enough to go back to work.”
Next steps, he said, were for the work crew to head back up to the site, form and pour the concrete caps, and set the large steel substructure underneath it with the new bearings that actually hold the bridge itself.
“We’ll put all those in place,” Rowe said. “There will come a point where everything is set in place that we’ll literally lift the bridge up by about ¼ inch or so. We’ll cut the old bearings and supports out to remove them, and then we’re going to install the new ones in and set the bridge right down on top of them. The goal is not to pick the bridge up very high or give yourself a bunch of space. It’s literally just to lift it just enough to where you can take all the old stuff out, slide the new stuff in and just set it right down on top of it.”
This will allow the Alaska Railroad to keep scheduled train service throughout the project. Swalling said that’s a primary goal of the project.
“Every morning we’d have a meeting with the railroad and they’d tell us a northbound train was coming at this time and a southbound train was coming at this time. We couldn’t have anything hanging over the track or crossing over the track for about an hour before the train passed by,” he said. With planning, the temporary restriction on activity didn’t cause any work delays, Swalling said.
Construction is expected to be completed by January or February 2019.
“Once the bridge is on its new substructure, we’re going to be working at removing that existing pier, the one in the center,” Rowe said. “We’ll start pulling that out, and as we pull that out and finish that, just the way we had walked ourselves out with the temporary trestle, we’re going to start pulling the pieces of trestle off and walk ourselves right back out of the water, removing the trestle itself as we go to where essentially you won’t know we’re there.”
Rowe said Swalling will remove the temporary access road it made along the right-of-way of the railroad “We’ll put some trees back, we’ll rough up the dirt and plant a lot of grass through there so it can look natural again.”
As soon as the crews start pulling trestle, the trucks will start rolling and Swalling will start moving its material and equipment off site.
“Any remaining work that’s left after that, we’ll do it on the ice itself.”
Tracy Kalytiak is a writer from Palmer.