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.

Bridge Design Meets Environmental Science

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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Structural Engineering
“The best part of my job is seeing needed infrastructure (especially bridges) get designed, permitted, and built.”

Doug Sarkkinen

Director of Bridges & Structures

Natural Systems Design
“Working at Otak allows me to experience interesting, exciting projects while furthering my professional and personal development. ”

Tracy Emmanuel

Manager of Water & Natural Resources, Colorado

Environmental Permitting
“Friendly people, challenging projects and collaborative problem solving, and honest work environment.”

Jeff Gray

Senior Managing Scientist

Stormwater Planning
“I like working at Otak because my projects bring me in contact with stormwater managers throughout the Pacific Northwest.”

Trista Kobluskie


Senior Planner