SUSITNA HYDROELECTRIC PROJECT SURVEY OF EXPERIENCE IN OPERATING HYDROELECTRIC PROJECTS IN COLD REGIONS VOLUME 1 - MAIN TEXT APPENDIX A & APPENDIX B Prepared by Harza-Ebasco Susitna Joint Venture Prepared for Alaska Power Authority Draft Report Apri1 1985 TABLE OF CONTENTS SECTION/TITLE PAGE 1. SCOPE OF WORK 1 2. SUMMARY 2 3. LITERATURE REVIEW 5 4. MAIL SURVEY 9 4.1 Questionnaires 10 4.2 Compilation of Responses 12 5. VISIT TO BRITISH COLUMBIA HYDRO AND PEACE RIVER TOWN 19 6. CONCLUSIONS AND RECOMMENDATIONS 20 42188183 i 850405 d II LIST OF APPENDICES II I A-l Mail Survey Questionnaire A-2 Compilat ion of Responses, Canada II A-3 Compilation of Responses, United States A-4 Compilation of Responses, Europe and Other Countries II B-1 Organizations Contacted, Canada B-2 Organizations Contacted, United States II B-3 Organizations Contacted, Europe and Japan C Responses to Mai1 Survey Questionnaire II D Supplementary Material Included in Responses E Field Memorandum of Visit by H.W. Coleman to British Columbia Hydro II (Vancouver) and Peace River Town, and Supporting Material 11II II II II II II d II III 42188183 ii II 850405 1. SCOPE OF WORK The Susitna Hydroelectric Project will be located in a reglon where winters are moderately severe and river and reservoir ice must be accommodated. The design and operation must consider ice effects both for the associated project structures and environmental effects on the aquatic, terrestrial, and human habitat. In particular, any changes to the natural condition of the river as regards ice must be addressed. In an attempt to develop background on experience for existing installations in cold regions, we have made the following investigations: A. Review of pertinent literature, B. Mail survey, and C. Visit to British Columbia Hydro (Vancouver) and Peace River Town. This report contains the results of that study including recommendations for the Susitna Hydroelectric Project. 42188183 1 850405 2. SUMMARY A literature review, mailed survey and site visit have been made to evaluate the procedures adopted by operators of hydroelectric projects in cold regions similar to the Susitna Hydroelectric Project site, in response to environmental concerns. Four specific areas were addressed: 1. Reservoir and powerhouse operating procedures to mitigate ice jam related flooding, 2. The effects of reservoir ice cover and bank ice on animal crossing, 3. Management of reservoir ice cover to control cracking and the associated danger to animals, and 4. Bank erosLon resulting from reservoir and river ice cover and its effect on suspended sediment and t urbi dit y levels, including ermissible turbidity levels. The results of the study indicate that: 1. There are a few documented proDlems within reservoir impoundment zones. These are generally caused by deer and elk fa11ing through a thin reservoir ice cover or by animals losing their footing on the ice cover. An operation constraint is being used at Lucky Peak Dam to minimize drownings. The reservoir water level is held constant during cover formation to prevent weak spots resulting from unsupported ce or i cracking which apparently occurs when the reservoir is drawn down during cover formation. 2. There are a few cases reported in Canada where ice jam flooding of towns has been attributed to upstream hydroelectric power operations. 42188183 2 850405 3. Where operational procedures are in effect, they are generally directed toward protecting human life and property rather than aquatic or terrestrial habitat. 4. Operational restrictions such as those for British Columbia Hydro's Peace River project include the following: a. During freeze-up ice cover progression through sensitive areas on the river, flows are controlled at a high level until the cover develops sufficient strength to withstand flow fluctuations. b. After freeze-up, the plant can be operated freely without endangering the cover except in the frontal zone. c. During break-up and melt-out, flows are again maintained at high levels in the sensitive areas to erode the cover "as quickly as possible. If tributary break-up appears imminent, B.C. Hydro releases are decreased in order to minimize the effect of the tributary ice surge on water levels in sensitive areas on the Peace River. 5. In other cases operational constraints are employed to prevent the formation of hanging dams in the river downstream of a hydro facility or to reduce water levels upstream of a hanging dam after it has formed. These hanging dams may result in high water levels which can reduce the plant generating capacity, endanger the powerhouse, or result in flooding of areas adjacent to the river. These types of constraints include: a. Inducing an early ice cover on the river upstream of known sites of hanging dams, by artificial means such as ice booms or other obstructions. When an ice cover forms, frazil ice production stops and the hanging dams, which result from frazil accumulation, are minimized. 42188183 3 850405 b. Inducing an early ice cover on the river by keeping powerhouse discharges low while the ice cover forms. This may result in more rapid i ce cover advance, preventing further f razi 1 production. After the ice cover is formed, powerhouse discharges can be increased. c. Preventing ice cover formation in sensitive areas by fluctuating discharges, continually breaking up the ice cover and keeping it downstream. This may result in higher water levels further downstream, but lower water levels in sensitive areas. d. Reducing discharges after a hanging dam forms in order to reduce water levels upstream of the hanging dam. 6. The Canadian Electrical Association and many plant operators indicated that powerhouse operations during the winter to maintain a st abl e cover would be site specific and require operating experience over a number of years. Reservoir discharge, climatic conditions, channel morphology, and water temperature are all variables which must be considered. 42188183 4 850405 II 3. LITERATURE REVIEW II Several organizations have published general informat ion and guidelines for II ice considerations in the design and operat ion of hydroelectric and other projects. These sources were reviewed: II 1. Evaluation of Ice Problems Associated with Hydroelectric Power II Generation in Alaska, Final Report to the State of Alaska Department of Commerce and Economic Development by J.P. Gosink and T.E. Osterkamp, of the University of Alaska Geophysical Institute. II The problems dealt with in this study pertained more to energy II generation than to environmental concerns. There was discussion of problems related to hanging dams and ice jams which is of interest. II Various methods for determining the open water reach downstream of a reservoir were discussed. A survey of hydropower plants was conducted to determine potential ice-related problems and possible solutions. II 2. Course Notes for Ice Engineering on Rivers and Lakes by the University II of Wisconsin, Madison in cooperation with the U.S. Army Corps of Engineers, Cold Regions Research and Engineering Laboratory and the II University of Wisconsin Sea Grant Institute. II The course notes include articles by leading authorities in the field of ice engineering, dealing with II .a. formation and breakup of a river ice cover and methods for analyzing and solving associated problems, II b. ice problems at hydroelectric structures, and d c. mechanical properties of ice and ice forces on structures. a 42188183 5 850405 The notes provide a good compendium of potential ice problems and engineering solutions. However, they do not deaI with environmentaI effects other than effects of flooding on human habitation. 3. Design and Operation of Shallow River Diversions in Cold Regions by the U.S. Department of the Interior, Bureau of Reclamation REC-ERC-74-19. This report contains information on potential ice problems and design guidel ines. Although the report is written for shallow river diversions, many of the design guidelines are applicable to hydroelectric projects as well. The report does not deal with environmental problems. 4. Winter Ice Jams on the Gunnison River, by the U.S. Department of the Interior, Bureau of Reclamation REC-ERC-79-4. The report details ice jam flooding problems associated with operating projects and methods used in an attempt to alleviate the problem. The flooding affected residents along the reach of the Gunnison River between Blue Mesa and Taylor Park Reservoirs. Relationships were developed between ice jam location, weather conditions and level of Blue Mesa Reservoir water surface. 5. Ice Management Manual, by Ontario Ministry of Natural Resources. This report includes guidelines for dealing with chronic ice problems including procedures for monitoring, predicting and acting on freeze-up and break-up ice jallll1ling related flooding. It includes information on conditions causing ice jallll1ling, explains causes and predictive methods for break-up, lists the data which should be collected in a monitoring program, and assesses the success rate of various remedial measures. 42188183 6 850405 6. Ice Engineering by the U.S. Army Corps of Engineers , EM lLLO-2-1612. This is a very comprehensive report summarizing potential problems at all types of civil works structures including hydroelectric projects. The report provides guidance for the planning, design, construct ion, operation and maintenance of ice control and ice suppression measures and is used by the Corps of Engineers for their projects. The manual discusses ice formation processes, physical properties 'and potential solutions. 7. Behavior of Ice Covers Subject to Large Daily Flow and Level Fluctuataions by Acres Consulting Services, Ltd. for the Canadian Electrical Association. This report contains much valuable information on the types of problems encountered relative to river ice covers downstream of hydroelectric projects. An attempt was made to establish the state-of-the-art in predicting the stability of a river ice cover subject to flow and level fluctuations. Theoretical computations were made to establish stability criteria for the ice cover and to provide a means for developing guidelines for flow and level fluctuations to prevent ice cover break-up. The study concludes that: " ...generalized criteria do not exist at present, and designs cannot be prepared for many cases of ice structure, or shoreline, interaction." The report concludes that extensive laboratory and field studies are necessary before a generally applicable model can be formulated and that the guidelines presented in the manual can be used to establish that field program. Site specific studies would also be required. 42188183 7 850405