BACKGROUND
Hofer Dam was built sometime around the turn of the century; it is a concrete gravity dam that spans the Touchet River approximately 4.1 miles upstream from its confluence with the Walla Walla River.   The dam provides irrigation water, for agricultural use, for The Eastside/Westside Irrigation District.  The Touchet River, which is the largest tributary to the Walla Walla River, provides habitat for ESA listed Mid-Columbia Steelhead, and Bull Trout as well as Spring Chinook which were reintroduced in the Walla Walla Basin by the Confederated Tribes of the Umatilla Indian Reservation (CTUIR) in 2000.   The target species for this Touchet River project are ESA listed Mid-Columbia Basin Steelhead and Bull Trout as well as reintroduced Spring Chinook.  Steelhead are the primary target species with adult summer steelhead migrating upstream from September through March and juvenile steelhead out migration occurring between March and July.  There are small but increasing numbers of Spring Chinook found in the Touchet River; most of the spawning adults are thought to be recruits from hatchery production from other river systems or returning progeny from the pre-spawning adult Spring Chinook planted in the Walla Walla Basin since 2000 by the CTUIR.   Spring Chinook adult migration occurs between Mid-April and end of June.  Bull Trout are not generally found in the lower Touchet River Basin; however, there are populations of Bull Trout in both the upper Walla Walla and Touchet River systems.   Fish populations in the Walla Walla River Basin have been severely impacted by poor passage facilities at diversion dams.  Inadequate passage conditions have been identified as one of the key factors responsible for the decline of native summer run steelhead in the basin.  In 1996, CTUIR and Bonneville Power Administration (BPA) commissioned a feasibility study to identify improvements necessary to restore fish passage conditions at several irrigation diversions in the Walla Walla River Basin.  The study, conducted by Montgomery Watson Harza (MWH), concluded that the Hofer Dam and diversion created a partial barrier to fish passage for both juvenile and adult salmonids.  The study also developed conceptual design alternatives and cost estimates for both screen and improved upstream passage and outlined several alternatives which were presented to agencies and stakeholders at a series of meetings.  The CTUIR and BPA attempted to identify an acceptable alternative and secure funds to implement a passage improvement project at Hofer Dam in the late-1990’s but were unsuccessful in that endeavor.  At that time Hofer Dam was a barrier to adult salmonids inmigrating from the ocean to spawning grounds in Touchet River headwater streams and an imminent threat to outmigrant juveniles moving downstream.  Most Basin stakeholders agreed that Hofer Dam was the biggest and most complex passage barrier for adults in the watershed and that passage had to be improved at this site if we were to recover mid-Columbia Steelhead, successfully re-establish spring Chinook and maintain the genetic viability of bull trout in the Basin.  On April 20, 2004 there was an onsite meeting between CTUIR, BPA, DOE, Corps of Engineers, Eastside/Westside Irrigation District, and WDFW at which time the WWCCD agreed to initiate the necessary action to secure funding to restart the long dormant project.  WWCCD applied for and received funds from the WA Salmon Recovery Funding Board (SRFB) for picking up where the MWH left off and completing an engineered design for a major reconstruction of Hofer dam and associated Touchet Eastside and Touchet Westside Irrigation Districts’ diversion.  Following completion of plans and specification in 2005 the WWCCD applied for and received funding from SRFB and the Energy Facility Site Evaluation Council (EFSEC) for construction of the project which was completed and became operational in 2006.  Copies of the final design (as built) drawings for the 2006 Hofer Dam project can be found in PISCES Attachments.
Prior to the 2006 WWCCD project, Hofer Dam was an imminent threat to juveniles produced in the entire Touchet River watershed which includes important spawning and rearing tributaries such as Coppei Creek, Wolf Fork, Touchet South Fork and Touchet North Fork.  The fish screen for the dam was installed sometime in the 40’s or early 50’s and did not meet modern day State or Federal criteria for fish screens.  The 2006 WWCCD project replaced the fish screens with compliant Interlox traveling belt screens which are maintained by the WDFW Yakima Screen Shop.  Adult passage was blocked by Hofer Dam at lower flows.  Hofer Dam is located on a relatively straight section of the Touchet River, with a bank-to-bank width of about 105 feet.  The dam is composed of two sections forming an angled shape that runs downstream towards the left bank.  Prior to the 2006 WWCCD project, the dam section adjacent to the right bank was the overflow section, which measured approximately 60 feet along its crest with an average elevation of 479.7 feet.  The left bank section was approximately 1 foot higher and 40 feet along its crest.  There was an 8-foot wide downstream apron that ran the entire length of the dam.  The apron eliminated the possibility for a jump pool and the height of the dam creates a 3.4-foot difference from headwater to tail-water, making passage nearly impossible during low flows. A fish-way structure was located on the apron where the two dam sections met.   The fish-way did not provide good attraction flows and had an inadequate plunge pool (the plunge pool bottom is the spillway apron).  The fish-way was believed to be ineffective during most flows.   The irrigators were required to install wood flash boards lined with plastic sheeting each irrigation season in order for them to get their water.  The flashboards raise the elevation of the dam about 1 ft. across the entire dam section (60 feet) adjacent to the right bank including the exit of the fish-way structure.  The 2006 WWCCD project raised the height of the dam about 0.6 ft., removed the old fish ladder, and installed a new pool and chute fish ladder.  The new project was intended to provide the irrigators with their water, provide juveniles with safe passage down the Touchet River and improve passage conditions for adults moving upstream.        
PROBLEM STATEMENT
In the years following construction of the 2006 WWCCD Hofer Dam project it became evident that the modified water circulation pattern in the Hofer Dam diversion pool caused an unforeseen problematic sediment accumulation in the diversion pool.  This problem sediment resulted from the fact that the lower Touchet River system carries an incredibly heavy load of suspended sediment at moderate to high flows and any slight attenuation of velocity has a significant negative effect on shear stress which is the ability of flowing water to transport suspended sand and silt.  Although the effect of structures on flow patterns and localized sediment transport are very difficult to predict, anecdotal evidence suggests that the problem at Hofer Dam stems from the fact that the flow rate through the fish ladder on the west side of the dam is lower than the flow rate through the spillway in the center of the dam.   Thus, at moderate flows when the main flow of the river is transporting a heavy sediment load, the reduced flow rate on the west side of the diversion pool is enough to cause a critical reduction in shear stress and a problematic accumulation of sediment which forms a bar in front of the irrigation diversion.  This bar impairs the ability of the diversion project to meet the needs of the irrigation districts (see ”Hofer Sedimentation Pattern” in Attachments). The accumulation of sediment is of sufficient size that it blocks water from entering the diversion and negatively affects the ability of the irrigation districts to divert their legal water right.  Without remedial action taken by the irrigation districts the diversion would not have delivered their legal water right.  These remedial actions include the use of heavy equipment (excavator) to dredge out the sediment accumulation and installation of wooden flash boards lined with black plastic sheeting across the dam and fishway to raise the forebay water level above the height of the sediment bar.  Since construction of the WWCCD 2006 Hofer Dam project, the irrigation districts, WDFW’s Yakima Screen Shop and the WWCCD have worked together and consulted with several engineers and a fluvial geomorphologist in an effort to understand the cause of the sediment issue.  In October, 2013 WDFW requested a meeting of the primary technical folks and stakeholders involved with Hofer Dam in an effort to flesh out a strategy for addressing the sediment issue.  This meeting ultimately lead to a site visit and suggested concept for structural modifications formulated by Bruce Heiner, WDFW Engineer, and Dave Karl, WDFW Biologist.  

PROJECT DESCRIPTION
The WDFW conceptual plan calls for:  a) converting the existing fish ladder into a sluiceway by removing the cross veins and installing an Obermeyer weir, b)  constructing a new pool and chute fish ladder adjacent to the old fish ladder, c) installing structures upstream that would direct flow toward the diversion/sluiceway.
BPA funding through contract 267441 will be used by WWCCD to develop a design and complete the necessary environmental compliance for structural and/or operational modifications that will rectify the sediment problem at the Hofer Dam diversion as described.  WWCCD will abide by federal contracting guidelines on the solicitation for proposals and procurement of the services of an engineering firm with demonstrated expertise in sediment transport, fish passage and irrigation diversion design.  The design subcontractor will be instructed to start with the concept described above and work with an interagency team of engineers and biologists to develop plans, specifications and an engineer's construction cost estimate for structural and/or operational modifications to the Hofer Dam Diversion that will allow it to operate as originally designed.  The intent of the WWCCD is to complete the design and EC work in 2014 and construct the project during the 2015 in-water work window.  When a final engineer's construction cost estimate becomes available (~5-31-2015) WWCCD will request that Gary James authorized construction funds from 2009-026-00 and that those funds be added as an amendment to CR-267441.          
  
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