Site work for a water / sewer project in Umatilla, Oregon. Completed plans call for site work for a water / sewer project.

The focus area for the solicited work is located on the Walla Walla River, approximately five miles southeast of Milton-Freewater, OR (Attachment A). This section of the Walla Walla River has been straightened and confined by informal levees and adjacent land use. The river confinements reduce channel connectivity to the flood plain. This section of the Walla Walla River also lacks structural elements necessary to create and maintain complex aquatic habitat. The CTUIR is accepting proposals to implement project tasks focused on removing the confining features along the proposed segment of the Walla Walla River, restoring floodplain connectivity, enhancing in-stream habitat diversity and quantity, and enhancing fish passage and survival at local irrigation diversions. The construction contract includes the following major elements, which are described in greater detail in the project design. The general goals of this project are to return an approximately 0.75 mile long reach of the Walla Walla River, located on private property, closer to its historic, naturally functioning state, and increase fish habitat quantity and quality while at the same time not adversely impacting present landowner land use needs. Key elements to accomplishing this goal include increasing channel complexity and floodplain connectivity, creating enhanced habitat diversity suitable for both spawning and rearing, constructing two reduced-maintenance, fish passable irrigation points of diversion (PODs), improving sediment sorting, enhancing stream velocity and thermal diversity, and promoting natural riparian function. Key fish species of concern include ESA-listed summer steelhead (Oncorhynchus mykiss) and Bull Trout (Salvelinus confluentus), resident Redband Rainbow Trout(O. mykiss), and spring Chinook Salmon (O.tshawytscha). The geomorphic processes, floodplain connectivity, and accompanying fish habitat within the project reach have been influenced by agricultural land use, homesite development, and the constricting effects of levee encroachment. These activities have led to limited instream and floodplain habitat complexity and degraded floodplain connectivity and riparian condition as key limiting factors for Chinook and steelhead in the vicinity of the project reach. This project aims to address these factors through stream restoration and habitat enhancement. The upper subreaches of the South Fork and the North Fork are confined by bedrock, revetments, bridges, roads, and terraces (Figure 3). The lower subreaches of the two forks are mainly unconfined but have incised enough that the 2-year flow does not access historical adjacent floodplains and is retained within the widened channel bottom. The Mainstem is confined along the right bank from the confluence of the forks downstream approximately 850 feet by a levee that was built after 1980. The Mainstem, North Fork, and the lower subreach of the South Fork are sediment transport limited. Bedload is supplied to the reaches in quantities that exceed transport capacity. The sediment transport regime results in bedload deposition and gravel bar development in these reaches. The North Fork and upper South Fork reaches lack floodplain continuity because of incision and revetments. The 10-year flow is still retained within the channel banks and does not access historic floodplain. The lower subreaches of the two forks, however, widened considerably in the large flood of 2020 and may begin to develop new floodplain within the channel bottom. There are several secondary channels on the right bank along the mainstem that are not accessible due to the levee. Additional secondary channels downstream along the left bank of the Walla Walla provide geomorphic complexity and floodplain continuity as they are activated during the 1.5-year flow. These secondary channels flow through an overstory of mature mixed riparian forest. Riparian and floodplain conditions at the site have been impacted by historical agricultural practices, domestic livestock grazing, surface diversions, residential developments, stream armoring, and flood control activities. In addition, significant flood events in 1965, 1996, and 2020 have altered river channel configuration and riparian cover. The point of diversion (POD) on the North Fork serves water right for a total withdrawal of up to 0.525 cfs. The POD on the Mainstem serves water rights for a total withdrawal of up 4.038 cfs. Each POD is currently configured as a surface ditch flowing to a rotating drum screen with bypass return pipes to the North Fork or Mainstem side channel, respectively. Gravel push-up dams and channels are constructed each year to maintain flow into the diversion ditches. These push-up dams can block fish passage during low-flow conditions. The project will involve specifically: o Excavation of 2,300 cubic yards of berm and channel material from the site, along approximately 850 feet of berm. Some of the excavated material may be used elsewhere in the project. The remaining material is to be hauled to a selected location identified in Attachment C. o Perform low-impact grading on three relict side channels as specified in Attachment C and D. o Install Large Wood Structures to create a variety of habitat conditions. All large wood structures will be constructed as specified in Attachment C and D. o Install one roughened riffle and diversion channel structure on the North Fork Walla Walla River and one roughened riffle structure on the South Fork Walla Walla River as specified in Attachment C and D. o Install an improved irrigation diversion, fish exclusion screen, and pipeline on the South Fork Walla Walla River as specified in Attachment C and D. Collectively, these actions are expected to lead to improved fish habitat, restored floodplain function, and improved sedimentation processes in this project reach. See all related contract documents including Attachment C for complete detail of construction requirements.