Duvall — Construction crews working for the Washington State Department of Transportation are removing an old culvert on Loutsis Creek just south of Duvall on State Route 203, and replacing it with a 15-foot tall arched bridge being billed as the first of its kind on the West Coast.
The structure will be built with "super-light" fiberglass forms, which do not require the typical heavy equipment associated with bridge-building. The conversion is expected to be complete on Aug. 26.
“Often building a bridge requires bringing in a large crane to place concrete girders, but these forms are light enough that people can handle them,” said Shawn Wendt, WSDOT’s engineer for the project. “We know this is a long time to close a highway thousands of people depend on each day, but traditional construction would take much longer.
Wendt said the fiber forms are hollow arched tubes with an opening to pump concrete. They have small holes to allow air to escape and are relatively light. Each form is 50-foot-long, one-foot diameter pipe that weighs about 200 pounds, which is light enough to be handled by two or three people.
Once the arches are in place, fiberglass panels are inserted between them and the concrete is poured inside. After it cures, crews will put fill over the top and repave the highway.
This method of bridge construction, according to Wendt, has been used in the northeastern part of the country.
The project got underway July 27 and will require a month-long closure of SR 203 in both directions just south of Big Rock Road. Those who use SR 203 between Duvall and Carnation need to plan for additional commute time to travel the two-mile detour route via Northeast Woodinville-Duvall Road, West Snoqualmie Valley Road Northeast and Northeast 124th Street.
Local traffic will be able to travel as far as Northeast 138th Street from the north and Duvall Park from the south. No one will be allowed access through the work zone while the project is ongoing.
“The existing Loutsis Creek culvert is being replaced because the water flow was too swift for salmon traveling upstream during the spawning season,” said WSDOT’s Tom Pearce. “The new culvert will create a more natural streambed, letting migratory and resident fish travel up and downstream more easily. It will open additional habitat and salmon spawning grounds to support growing fish populations in the Salish Sea.”
The total project cost is $8.2 million and will be financed from state and federal funding.