The goal of this project was provide complete fish passage for adult and juvenile salmon and trout. The primary species that will benefit are coho salmon and cutthroat trout, but this project will also benefit native char (bull trout and dolly varden), stream-type Chinook salmon, steelhead trout, and chum salmon. Winter rearing habitat has been identified as an important limiting factor for coho (Beechie et al 1994) and to a smaller extent Chinook salmon (SRSC and WDFW 2005). This project will provided passage for juvenile salmon to an extensive complex of existing winter rearing habitat. Upstream from the O'Brian culvert there was over 100,000 square meters of winter rearing habitat along 2.3 linear miles of sloughs and wetlands. Juvenile passage was needed so that coho spawned in other nearby streams can access and utilize the abundant, high quality rearing habitat. Improved passage to O'Brian Creek likely also benefits juvenile Chinook (stream type life histories) that spend the winter rearing in fresh water and bull trout which may use the habitat for foraging.

The O'Brian Creek Complex includes a large system of tributary, sloughs, and wetlands that drain directly into Illabot Creek, an important salmon-producing tributary of the Skagit River that supports populations of Chinook, chum, coho, and pink salmon, native char and steelhead trout. The O'Brian Creek Complex itself is maintained by large contributions of groundwater from the surrounding floodplain, so this project provided fish passage to abundant existing rearing habitat that is supported by stable groundwater flows. This is one of the most productive floodplain reaches in the entire Skagit basin (Smith and Ramsden 2006), so this additional rearing habitat should have been colonized immediately by fish. It also greatly benefits juvenile coho salmon spawned in two constructed groundwater spawning channels in the immediate vicinity (Illabot Channel, the outlet of which is just 1500 ft from the O'Brian Creek culvert, and Powerline channel, located nearby on the Skagit River).

The project involved replacing the undersized 48' diameter culvert with a 40' load-rated steel bridge along a powerline road that provides access to powerline towers and a number of private parcels. The O'Brian Creek complex flowed beneath the powerline corridor through an undersized culvert that acted as a velocity barrier for juvenile fish. The width of the channel was 32' at this location; therefore the 48' culvert was undersized and created a debris problem, increased the scour on the downstream end, and was a velocity barrier for fish passage. Water also occasionally overtopped the road, making crossing the road during high flow conditions hazardous and degraded the condition of the road. The installation of the bridge eliminated the channel contrainst caused by the culvert, improved natural flow conditions and passage of debris, and allowed for unrestricted access to over 100,000 square meters of overwintering habitat.