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Project Update: Cle Elum Dam Fish Passage Summer 2022

By August 3, 2022 No Comments

The Cle Elum Fish Passage project reestablishes access for juvenile sockeye, chinook, and steelhead around the Cle Elum Dam. Garco Construction, Inc. (Garco) is constructing six intake structures that stack on top of each other on the upstream end of the project to allow water to be drawn in from the lake and pass fish through the system regardless of the reservoir level (the lake fluctuates approximately 100 feet in elevation each year for irrigation purposes). Only one intake level will operate at a time though when the system is running since juveniles typically only travel within 8-10 feet of the water surface. Once in the intake system at a given level, the fish will travel through pre-cast intake conduits, a tunnel and intake penetration section, and then enter the previously constructed secant shaft that is broken up into two separate chambers by a cast-in-place separation wall. The gate chamber is on the upstream side of the shaft, and includes steel square pipes, a guard gate that allows water to flow into the system when open or holds water back with a seven by seven foot horizontal knife gate when closed, and a warped floor steel transition that prepares fish to enter the next chamber. Similar to the intake structures, the gate chamber is made up of six separate levels, with the foundation constructed approximately 90 feet below the finished ground line (also the roof line of this system since the secant shaft is constructed into the earth). Personnel access to each level will be from an elevator or a stairway shaft.

After entering the warped floor in the gate chamber, fish will begin to enter the helix chamber on the downstream side of the separation wall. The warped floor begins to transition the fish into a helix system (a spiral or corkscrew configuration) that will drop the fish in elevation to the bottom of this chamber. The helix is comprised of 117 pre-cast flume pieces supported by structural steel with the foundation being approximately 120 feet below the future finished ground/roof line. Each gate chamber level connects horizontally into the helix transition, but the foundation of the helix chamber is lower in elevation so there are 8 levels inside this chamber opposed to 6. The overall decent of the fish in the helix will depend on what level they enter the gate chamber at, but all fish will travel to the helix transition at the base of the chamber that allows them to enter into an existing tunnel (constructed by others). This tunnel is 7 feet in diameter and travels approximately 1,250 feet to the tunnel exit portal. Garco will tie on approximately 400 feet of HDPE pipe at this point to construct what is called the outfall pipe. This section will allow the fish to enter the outfall pool in the Cle Elum River at the end of the system. At that time the juvenile fish can continue to migrate downstream to the next dam.

Current Project Status:

Since our last project update, Garco has completed work inside the secant shaft that includes the separation wall that divides the gate and helix chamber, topped out each chamber’s access structure that house an elevator shaft, stairwell, and areas of refuge, installed all structural steel framing for the six levels in the gate chamber, poured concrete slabs supported by metal decking at each of these floors, set the six guard gates that act as emergency bulkheads for the intake system, and set the steel joists and framing for the gate chamber roof. In addition, our subcontractors have completed tunneling on two of the six intakes into the secant shaft, fireproofed the structural steel in the gate chamber, ran ductbank from the facility yard to the secant shaft, and set electrical and mechanical items for the facility to operate in the future. Beyond the secant shaft work, Garco also completed the concrete work on 2.5 intake levels in the fall and winter of last year (3.5 of 6 intakes completed at this time), set a water control gate called a crest gate at the lowest intake level, and continued construction of MSE walls and access roads. Our earthwork subcontractor has also tied to the previously constructed outfall of the tunnel with an hdpe pipe that heads directly into Cle Elum River where an outfall pool was also constructed by this subcontractor.

The project team at Cle Elum has now turned over the helix chamber to our ironworkers to begin structural steel and precast erection of the helix structure that drops the juvenile fish over 80’ in elevation to allow them access to the previously constructed tunnel structure. This section of work started after the 4th of July and is anticipated to run through December. Once completed, Garco will have tied all work to the guard gates that have been previously set and move forward with commissioning the system once the intake structures are completed and the reservoir is at the appropriate elevation. Also, Garco and our subcontractors are currently working to run permanent power into the secant shaft, complete underground conduit and fire piping runs that go to miscellaneous structures in the facility yard and the secant shaft, and are constructing equipment and tank pads that support unit substations, an 80,000 gallon water tank for our fire suppression system, and generator/fuel storage equipment.

The reservoir at Cle Elum continues to drive our work related to construction of intake structures, tunneling, and the overall work scope on the shoreline. The lake should drop to an elevation that allows for access to occur around the end of August. Garco and our associated subcontractors will then start tunneling into the secant shaft one level at a time and constructing the remaining intakes at levels 2 and 3. Other elements such as intake gates and structural steel will also be worked on when the lake drops at previously completed intake structures. Work in the reservoir is currently expected to run through the end of December or as weather allows. Depending on lake levels, Garco may complete some non-critical work in this area in April and May, but final construction in the reservoir is not expected to be completed until the end of 2023 or beginning of 2024 due to a schedule extension that was issued by the owner. The final contract completion date is currently slated for the end of August 2024 at this time.

Take virtual tour of the project here.

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