Pilchuck River Bridge 581 is located on 64th St NE in the Lochsloy community, between Granite Falls and Lake Stevens. The new replacement bridge is a single-lane, single-span structure. The new steel truss design eliminates the need for intermediate support piers in the river and help to reduce debris accumulation under the bridge. The new bridge was constructed immediately upstream of the existing bridge and was completed the winter of 2017.
The total cost of the bridge replacement project was estimated at approximately $4.5 million. A federal bridge replacement grant funded 80% of the cost, with the remaining 20% supplied by local matching funds.
Northwest Hydraulic Consultants (NHC) was retained to prepare a Channel Migration Zone (CMZ) Study (PDF), which was completed in February 2013. Snohomish County Surface Water Management staff conducted the hydraulic modeling during 2013; the report (PDF) was completed in September 2013. Information from the modeling and the required CMZ study is essential for designing the bridge.