ARLINGTON HEIGHTS The latest phase of construction on the Swanson Road bridge recently wrapped up, but Snohomish County Public Works reminded area motorists that the new bridge isnt scheduled to be opened until next summer.
Ken Miller, project engineer with Snohomish County Public Works, explained that the project will replace the existing wood trestle bridge which has been in place since 1935. The project is widening and reducing the grade of the road, which currently has a blind curve and a slope of more than 10 percent.
The county regularly rates all of its bridges and replaces about two to three every year, Miller said. We take advantage of federal money which can cover up to 80 percent of the total cost, which in this case is more than $4.5 million. Well be getting slightly less than 80 percent this time, though, since construction costs have risen since we locked in the designs for this project a few years ago.
Miller elaborated that this project will ultimately benefit not only the residents of approximately 25 homes on the other side of the bridge, but also the timber companies whose logging trucks use the bridge. It will make the road safer to drive on, especially during rain and snow, he said. In order to accommodate construction, those residents and truckers have been diverted to alternate roads for the past month as the bridge has been closed between 7:30 a.m. to 3:30 p.m. weekdays, adding an estimated 15 minutes or more to driving times.
We tried to schedule those times so that people could go to work or school without being too affected, Miller said. We set up a row of mailboxes for residents to collect their mail and weve offered a shuttle service from our main staging site, so that people could park their cars there without having to drive down or around the bridge.
Crews finished drilling shafts to the new bridges supports Oct. 10, nearly two months after they began prep work on the site in August. The new bridge will be a 293-foot-long, three-span concrete and steel structure located on a straight alignment with the approach road south of the existing bridge, eliminating the tight curves of the current approach. When completed, the bridge will be 28 feet wide, nine feet wider than the existing bridge, and will handle two lanes of traffic.
Each shaft goes about 120 feet down, Miller said. We had to go deep to reach the hard foundation because, otherwise, all it would take would be one earthquake and you could kiss it goodbye. That added significantly to the cost.
To prevent the empty shafts from collapsing in on themselves, crews filled them with slurry, a viscous liquid that can be reused. From there, towering cranes lifted the rebar cages for the supports into place and when concrete was pumped into the shafts, it forced out the slurry.
Were going away for a while, said Miller, noting that several of the projects remaining materials arent expected to be assembled until March. Well be back then, to splice together the three spans of the bridge, starting with the two at the end. From there, well need to lay the concrete for the deck and give it time to cure, as well as set up the railings. Some of these parts will come pre-cast, but well still need to schedule another road closure.
Miller predicted that the new bridge would be complete and open to traffic in June, but warned drivers to plan for single-lane traffic on the current bridge in the meantime.