Lower Big Quilcene Riverscape Restoration and Bridge Replacement Jefferson County, Washington
Critical infrastructure updates and subsequent restoration of the surrounding floodplain eliminate county road flooding and improve safety for non-motorized traffic along the lower reach of the Big Quilcene River. A new bridge along with levee removal / relocation are part of a design emphasizing a number of habitat enhancement features. Otak completed baseline environmental documentation to support permit submittals for construction, led the road and bridge design, and supported the riverscape restoration design through detailed geomorphic, sediment transport, and hydraulic analyses.
Updating Critical Infrastructure while Reconnecting a Floodplain
In close collaboration with associated stakeholders, including the Hood Canal Enhancement Group and the Jamestown S’Klallam Tribe, a design focused on integrated floodplain protection replaces an 80-foot-long bridge with a 1,040-foot-long floodplain-spanning bridge. For a channel that had been historically leveed, the Linger Longer Road bridge replacement and associated riverscape restoration allows more area for the floodplain to occupy, decreases sediment impacts to Quilcene Bay shellfish beds, and re-establishes a highly-productive corridor for salmon habitat. The features also improve recreational access to fishing, exploring, and wildlife observation.
Geomorphology and hydraulics (using a two-dimensional hydraulic model) guided the bridge design. The environmental science behind the project was essential to verify scour estimates, federal no-rise requirements, and support bridge-associated pier and abutment protection.
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