Padden Creek Fish Passage

KPFF is working with Granite Construction on the replacement of two total fish barriers with four total fish passable structures under I-5 and SR 11 at Padden Creek in Bellingham, WA. Scope of services include:

High Quality Habitat: KPFF is providing prime engineering, civil, structural and stream design to build a high-quality aquatic habitat. Two fish barrier culverts are being replaced with four injunction-compliant fish passable structures to improve over 1,000 LF of stream habitat. By optimizing the stream alignment and structure type, KPFF reduced the length of stream channel constructed under structures by 49.5 feet, a nearly 20% reduction compared to the conceptual design. KPFF’s design also includes 35 key pieces of Large Woody Material (LWM), exceeding the Fox and Bolton Requirements and doubling the amount of wood required by the contract.

KPFF utilized 33 additional pieces of LWM within the stream channel, and another 51 pieces of wood within the floodplain to provide a high-quality habitat and channel diversity, all of which were above the contract requirements. In addition to the LWM, the design also includes meander bars, gravel bars, spawning gravels and deformable riffles. KPFF also collaborated with Granite and stream team to collect six McNeil sediment samples to supplement the Wolman pebble counts and better categorize the natural streambed material as deep as nine inches below grade. The McNeil and Wolman data was used to better size the proposed streambed material, allowing for smaller streambed material and spawning gravel to provide high quality habitat for all fish life stages.

Support from Stakeholders: To gain support and collaborate with the regulators, KPFF and Granite created Multi-Agency Permitting Partnership (MAPP) meetings for timely and effective communication and collaboration. They provided a chance input from WDFW and the Tribes and allowed the design-build team to improve the design, increase fish habitat, and increase support. While the team originally committed to two MAPP meetings, meetings were held monthly as all parties saw their benefit. The meetings facilitated approval of the JARPA in just 38 days, and the HPA permit from WDFW in only 31 days, indicating strong support.

Minimize Impacts to Environmentally Sensitive Areas: KPFF shifted the stream alignment from the conceptual design locations, allowing the majority of the new stream alignment and bridge/culvert structures to be constructed off-line from the existing channel. By constructing the new stream away from the existing channel, impacts to the existing stream channel were limited to the channel tie-in points at each end of the project, minimizing the amount of time the stream is in the bypass pipe during construction and protecting environmentally sensitive areas. At the SR 11 site, KPFF designed the existing channel downstream of the crossing as off-channel habitat that is wetted at higher flows, minimizing impacts in this environmentally sensitive riparian area and re-purposing it within the new design.