The project site is located at a privately owned irrigation diversion structure that crosses the Lostine River approximately 1 mile south of the town of Lostine, Oregon (Figure 1, Vicinity Map). More specifically, the project site is located at river mile 4.8 on the Lostine River and generally includes the mainstem Lostine River and the Poley-Allen irrigation diversion structure and intake. Notable features of the site include:

*   An existing fish drum screen downstream of the point of diversion (within the upland area west of the river).
*   A channel-spanning concrete sill with a low-flow fishway at the point of diversion.
*   A concrete abutment at the concrete sill along the river right bank.
*   Approximately 170 feet of existing riprap lining the left bank, upstream and downstream of the point of diversion.
*   A side channel along the river right floodplain. The side channel inlet and outlet are approximately 400 feet upstream and 180 feet downstream of the point of diversion, respectively.

The existing Poley-Allen irrigation diversion is located on the west side of the Lostine River and consists of a headgate intake structure, a forebay with a second headgate that provides the irrigation water right to a gravity-driven open channel. The diversion includes a sill located between two concrete abutments on each channel bank and holds a series of boards in the vertical slots in six concrete piers. The boards are used to maintain a minimum water surface elevation that provides the hydraulic head required to deliver between 9 and 11 cubic feet per second (cfs) into the irrigation ditch.  The current diversion structure is an upstream passage barrier for ESA listed spring/summer Chinook Salmon, steelhead and Bull Trout.

A high-flow side channel extends approximately 570 feet on the right (eastern) side of the main channel. The side channel has a defined bed and bank, which suggests flow is present at least annually. However, overall, the side channel lacks complex structure such as Large Woody Material (LWM) and, as a result, low velocity juvenile rearing areas are sparse but potential for restoring them is high.

The project design development focused on mitigating fish passage limitations associated with the mechanical manipulation of the channel and providing irrigation water to the water right holders. The design development also included side-channel habitat improvements with LWM structures. The design engineer developed the proposed actions collaboratively with the landowners and the NPT and identified the roughened channel as the preferred alternative for providing fish passage while maintaining the necessary head for irrigation delivery. The proposed actions involve construction of a roughened channel, modification of the existing concrete sill and removal of the existing abutment on the right channel bank. Boulders will be placed within the roughened channel for hydraulic complexity and roughness. Irrigation water will continue to be collected in the existing concrete point of delivery located upstream of the grade-controlling roughened channel. The engineer anticipates streambed material deposition within the forebay due to static channel grade. To manage sediment deposition within the entrance forebay, they included a sediment management pipe with a manually operated valve that discharges downstream within the roughened channel.  The outcome of this project will maximize year-round fish passage for all life history stages of Bull Trout, steelhead, and Chinook Salmon, while maintaining access to irrigation water for current water rights holders.

The goal of this project is to restore fish passage through the Poley-Allen diversion structure while maintaining a minimum water surface elevation upstream of the diversion structure sufficient for the delivery of legal irrigation withdraws for the associated landowners.  By modifying the existing channel spanning concrete sill and concrete abutment, installation of a roughened channel downstream of the sill, and enhancing habitat in the adjacent side channel through LWM placement, this project will maximize year-round fish passage and diversify fish habitat for all life history stages of Bull Trout, steelhead, and Chinook Salmon, while maintaining access to irrigation water for current water rights holders.

Project partners include the Grande Ronde Model Watershed and BPA.