Habitat - Fish Passage Technical Assistance
Date Published: December 2008
Number of Pages: 54
Author(s): Prepared by: R2 Resource Consultants, Inc. in association with Kozmo Ken Bates
This white paper was prepared on behalf of the Electron Downstream Fish Passage Work Group to review potential options and assess the technical feasibility for improving the downstream fish passage conditions at the Electron Hydroelectric Project. The objective of the study was to assess a wide variety of potential options for downstream passage and determine which options appear to have the possibility of functioning given the relatively extreme design and operating conditions at the Electron Project.
A variety of general approaches were considered, including:
- Screen fish at the intake and prevent them from entering the flume.
- Divert all fish from the flume near the intake and bypass them back to the river.
- Divert all fish from the flume near the settling basin and bypass them back to the river.
- Divert all fish from the flume near the forebay and truck fish to the river.
- Allow fish to pass to forebay and improve collection facilities there, and truck fish to the river.
Descriptions are provided for five options the study team felt have enough merit to warrant further investigation, and met the evaluation criteria. Options that were not believed to be feasible are also documented, with discussions describing why the study team felt they would likely not function well in this environment. Key differentiators for the five remaining alternatives include facility location, fish bypass mechanisms, and whether or not to design to fingerling or fry criteria. The key concern with all of the design concepts is sediment management.
The five alternatives considered to be potentially viable include:
- Plate fingerling screen near intake
- Plate fry screen downstream of settling basin
- Inclined fingerling screen near intake
- Inclined fry screen downstream of settling basin
- Improve existing forebay trap and holding
This list of options can be reduced with further definitions of biological needs and practical options for sediment management. A framework on how to proceed with further analysis is provided if the work group chooses to proceed further with fish passage improvement investigations. It should be understood that this was only a brief review with the main goal of eliminating options that clearly had deficiencies given the local conditions in the Puyallup River at Electron. The fact that five options are considered worth some level of further review should not be taken as an implication that upon further feasibility development some of them may prove to be unworkable.
Budget and time constraints for this review limited the level of detail that was possible for these assessments. Therefore, some of the option descriptions provide multiple potential locations and approaches for providing the passage downstream, with little detail and significant questions that will need to be assessed in further feasibility studies. Although rough ranges of potential construction costs are provided, they are based on the overall costs of similar facilities that have been installed at other projects and not on any detailed breakdown of quantities and unit costs for the components that may be required or the site conditions at Electron. Additionally, assessments of long-term operation and maintenance costs, or the potential cost of lost generation during construction, were beyond the scope of this review.
The Electron Project is a challenging site for fish passage facilities, however, there are options worth further consideration. Additional information should be developed to quantify the existing system’s performance, and help determine how to resolve some of the trade-offs between approach, screen location, and sediment management issues. This could be developed with the work group based on biological data and goals, along with a thorough sediment investigation. If this recommended information were developed, it would be possible to further reduce the list of potentially viable alternatives, at which time a more detailed engineering feasibility analysis could be conducted. Close coordination of biological goals along with a potentially iterative engineering feasibility analysis and assessment to meet the goals is recommended with any further study.