Squalicum Creek Channel Relocation and Modeling

The City of Bellingham completed design and construction of a mile long relocation of Squalicum Creek, coincident with designs for a regional rail trail along with a future major roadway connection.  The previous stream passed through fish barrier culverts as well as an abandoned borrow pit, with the new channel eliminating these fish constraints and creating a more diverse and natural channel habitat.  The new channel passes under a recently completed bridge replacement at James Street as well as an existing Interstate 5 railroad overpass.  Sharing the Interstate 5 bridge opening will be the proposed Bay-to-Baker trail and Orchard Extension roadway.  KPFF was lead design engineer for the corridor project, with MacLeod-Reckord on the team for trail design.  Interfluve provided channel design, with WSE under subcontract to both KPFF and Interfluve for hydraulics.

Role / Services:  WSE provided hydraulic engineering and modeling in support of the preliminary, intermediate, and final design and permitting of the proposed roadway, regional trail, and channel restoration project located within the FEMA floodplain of Squalicum Creek.  Complex split flows and backwater caused by various road embankments required use of branched flow unsteady modeling using HEC-RAS.  WSE evaluated multiple alternatives to provide design water surface and other inputs for the roadway and trail embankments, with five bridge or culvert openings spanning the stream or floodplain.  WSE also evaluated scour risk at each opening and providing design guidance accordingly.  Under separate contracts with the City of Bellingham, WSE has also provided hydraulic modeling and evaluation of the relocation and restoration of the Squalicum Creek channel.  Pier and abutment scour at the existing I-5 freeway bridge spanning the proposed channel and road/trail embankments was also considered.

Outcome: The project aims at improving non-motorized and motorized transportation within the constraints imposed by existing infrastructure, along with improving stream conditions to benefit habitat function. The James Street Bridge, channel relocation, and trail work were completed in 2015 and 2016. The Orchard Extension will be constructed at a future date. A feasibility study for a downstream extension of the channel reroute is presently also underway by Interfluve and WSE. A “no-rise” certification and CLOMR with revised flood maps was prepared and submitted, and has been approved by FEMA. The channel relocation was named the 2016 APWA national environmental project of the year (under $5 million)