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Facility Vulnerability Assessment for Imperial Dam and Desilting Works

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Facility Vulnerability Assessment for Imperial Dam and Desilting Works Facility Vulnerability Assessment for Imperial Dam and Desilting Works Invasive Quagga and Zebra Mussels Lower Colorado Region Yuma Area Office Boulder Canyon Project - All-American Canal System U.S. Department of the Interior Bureau of Reclamation Technical Service Center Denver, Colorado August 2012 Facility Vulnerability Assessment for Imperial Dam and Desilting Works Invasive Quagga and Zebra Mussels Prepared for Reclamation’s Lower Colorado Region & Yuma Area Office Mission Statements The mission of the Department of the Interior is to protect and provide access to our Nation's natural and cultural heritage and honor our trust responsibilities to Indian Tribes and our commitments to island communities. ___________________________ The mission of the Bureau of Reclamation is to manage, develop, and protect water and related resources in an environmentally and economically sound manner in the interest of the American public. U.S. Department of the Interior Bureau of Reclamation Technical Service Center Denver, Colorado February 2012 Disclaimer The information provided in this report is believed to be appropriate and accurate for the specific purposes described herein, but users bear all responsibility for exercising sound engineering judgment in its application, especially to situations different from those reported. References to commercial products do not imply endorsement by the Bureau of Reclamation and may not be used for advertising or promotional purposes. Cover Photo: View of Imperial Dam and Desilting Works iii Contents Executive Summary .............................................................................................. 1 Findings............................................................................................................. 1 Recommendations ............................................................................................. 1 Introduction ........................................................................................................... 3 Purpose and Objectives ..................................................................................... 3 Brief Project Description .................................................................................. 3 Background on Potential Invasive Mussel Impacts .......................................... 3 Assessment Findings ............................................................................................. 6 Susceptibility to Infestation .............................................................................. 6 Recreation ................................................................................................... 7 Dam and Spillway ....................................................................................... 7 Drainage System ................................................................................... 8 Intake Structures ......................................................................................... 9 Gates ......................................................................................................... 11 Service Water Taps ................................................................................... 13 Pumps ........................................................................................................ 14 All American Canal Desilting Works ....................................................... 15 Bulkheads and Stoplogs ............................................................................ 19 Instrumentation ......................................................................................... 19 Reservoir Elevation Gauge ................................................................. 19 Flow Measurement.............................................................................. 20 Other ................................................................................................... 20 Laguna Dam .............................................................................................. 21 Conclusions .......................................................................................................... 21 Recommendations ............................................................................................... 22 Monitoring and Detection ............................................................................... 22 Response Planning .......................................................................................... 22 Facility Protection Options ............................................................................. 22 Intake Structure ......................................................................................... 22 Emergency & Regulating Gates................................................................ 23 Bulkheads .................................................................................................. 23 Instrumentation ......................................................................................... 23 Drainage Systems...................................................................................... 23 Pumps ........................................................................................................ 23 Desilting Works ........................................................................................ 24 Appendix A .......................................................................................................... 25 Facility Vulnerability Checklist ...................................................................... 25 2. Preparation (Step 1) ............................................................................. 25 3. In-house Review and Preparation for Field Visits (Step 2) ................. 26 4. Site Visits, Follow-up and Reporting (Step 3) ..................................... 27 5. Mussel Vulnerability Evaluation - Project Team Contact List ............ 27 6. Mussel Vulnerability Evaluation – Sample Facility Deliverables List 28 1. Instructions for Using this Document ................................................... 29 2. Walkthrough Checklist ........................................................................ 29 iv Appendix B .......................................................................................................... 33 Management Options for Quagga & Zebra Mussel Infestations .................... 33 Actions to consider prior to detection of mussels: .......................................... 33 Actions to consider following detection of mussels: ...................................... 34 v Executive Summary The purpose of this assessment is to provide Reclamation management and project staff with information regarding the vulnerability of facility features to invasive mussel impacts. This report is not intended to be a risk assessment or prediction of the severity of the existing quagga mussel infestation. Instead it is intended to assist project management and staff in anticipating and planning for impacts should the infestation become exacerbated. Findings Imperial Dam and Desilting Works and appurtenances are relatively complex for a diversion structure. The outlet works intake structure trashracks, All American Canal desilting works, reservoir level measurement system, and sampling and irrigation water pumps appear most susceptible to mussel-related impacts. While it is currently uncertain, the potential for mussel settlement in drainage systems (including structure under drains and drain outlets with the potential for back flooding) should also be considered and closely monitored if a future infestation worsens. Potential factors mitigating mussel impacts that were identified during the site visit included extended high seasonal water temperatures and concomitantly low dissolved oxygen levels at the outlet works. The validity of these and potentially other environmental factors remains to be verified. Initial recommendations and options for facilities protection are provided to assist with preliminary planning and budgeting should the existing invasive mussel infestation worsen. It should be noted that various options for facilities protection exist (this report is not an all- inclusive list of possible options and new technologies may become available in the future). Selection of the best option will depend on a number of considerations including operational flexibility, design requirements, project constraints, and cost. Recommendations The following recommendations are provided for consideration: Invasive mussels have been detected at Imperial Dam and Desilting Works since 2008, but they have remained minor faunal constituents. This report is based on the hypothetical assumption that mussels will become problematic at some future time. While there is no precise way to foretell whether the Imperial infestation will become an issue without further study, planning ahead will allow time for budgeting and implementation of response actions if needed. It is important to build upon the Lower Colorado Region Invasive Mussel 1 Response Plan by developing site-specific plans to address a potential future worsening of the infestation. General information on management options have been included in Appendix B along with links to other response plans and response planning guidelines developed by the National Parks Service. It is also recommended that a monitoring plan, via plankton net sampling, be established as well as monitoring for settlement using either substrates and/or routine inspection of underwater
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