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To help support the potential benefits of the instream flow management regime, the HCP provides funding for facility improvements at Seattle City Light Cedar Falls hydroelectric facility and at the U. S. Army Corps of Engineers Hiram Chittenden Locks (Ballard Locks).
Emergency Bypass Improvements
In its original configuration, the Cedar Falls Hydroelectric Project was not able to provide flow to the river during emergency shutdown of electrical generating equipment. To remedy this situation, in early 1999, the City installed equipment to provide bypass flows around its hydroelectric turbines during most emergency plant shutdowns. This original bypass system’s flow capacity was limited to approximately 70 percent of the original flow passing through the generator prior to the load rejection. The city expanded the emergency bypass system’s scope to improve the flow capacity through the bypass system as part of the HCP. This work was completed in 2002 and has resulted in a more reliable system that has provided matching flow continuation to the river during most emergency shutdowns. These changes reduce the risk of stranding juvenile salmonids and dewatering salmonid redds.
New Tailrace Barrier
With the original configuration of the tailrace at the Cedar Falls Hydroelectric Project, upstream migrating adult fish were at risk of entering the turbine effluent pipes where they were subject to injury or mortality. The City installed a tailrace barrier in 2002, prior to fish passage above Landsburg dam to prevent salmon that reached the powerhouse from accessing the tailrace. Currently no anadromous fish have been documented in the reach of the river where the Cedar Falls Powerhouse is located. As a result, the barrier has not yet been truly tested.
Low-level valve installation in Masonry Dam
Approximately a 0.5 mile of the potential anadromous fish habitat is present in the “Canyon Reach” of the Cedar River between the tailrace of the Cedar Falls Hydroelectric Project at RM 33.7 and natural migration barrier formed by Lower Cedar Falls at RM 34.2. As part of the HCP the city committed to providing a minimum of 30 cfs in the “Canyon Reach” which began with fish passage above Landsburg. Modification to the dam was required, which included the installation of a new valve and new automated control system to provide the continuous minimum river flow of 30 cfs and to improve the control system for downramping. The new guaranteed flow of 30 cfs began September, 2003 and has been successfully implemented ever since.
Water flow at the Locks must be shared between vessel traffic and migrating fish, both upstream and downstream. Investigations have shown that there are opportunities to improve the efficiency with which fresh water is used at the Locks through various facility and operational improvements. The HCP provides funding for the USACOE to help assess and potentially implement measures to improve conditions for migrating fish through enhanced water use efficiency.
Smolt passage improvements
In co-sponsorship with King County and the Muckleshoot Indian Tribe, the HCP provided funding to the USACOE for the construction and installation of smolt passage flumes at the Ballard Locks. The flumes provide improved downstream passage conditions for emigrating juvenile salmon and steelhead.
Water Resources Manager
Seattle Public Utilities
Phone: (206) 615-0021