takatz appraisal report - final - sitka, alaska · 10.2 principal cost components for project...

Takatz Lake Hydroelectric Development

Appraisal Study Report

Submitted to:

City and Borough of Sitka Sitka, Alaska

Submitted by:

Currents Consulting Seattle, Washington

October 2014

Takatz Lake Hydroelectric Appraisal Study October 2014

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Table of Contents

Section Title Page

SECTION 1 – EXECUTIVE SUMMARY ..................................................................................... 1 1.1 Background ...................................................................................................................... 1 1.2 Objectives ......................................................................................................................... 1 1.3 Hydrology, Environmental Studies and Constraints ........................................................ 1 1.4 Project Development Alternatives ................................................................................... 2 1.5 Power Operations Studies ................................................................................................ 3 1.6 Construction Cost Estimates ............................................................................................ 3 1.7 Recommended Development Plan ................................................................................... 3 1.8 Future Studies ................................................................................................................... 4

SECTION 2 – INTRODUCTION .................................................................................................. 6 2.1 Project Setting .................................................................................................................. 6 2.2 Study Scope ...................................................................................................................... 6 2.3 Reference Documents and Prior Engineering Studies ..................................................... 9 2.4 Engineering Site Assessment ........................................................................................... 9 2.5 Hydrology....................................................................................................................... 10 2.6 Development Alternatives Considered ........................................................................... 10 2.7 Power Operations Studies .............................................................................................. 11 2.8 Cost Estimates ................................................................................................................ 11

SECTION 3 – HYDROLOGY ..................................................................................................... 12 3.1 Overview ........................................................................................................................ 12 3.2 Hydrology Analyses in the 1968 Study.......................................................................... 13 3.3 Extension of 1968 Estimated Hydrology Record ........................................................... 18

3.3.1 Source Data .............................................................................................................. 18 3.3.2 Methodology for Extension of Estimated Record ................................................... 18

3.4 Streamflow Measurements at Takatz Lake Outlet, 2009 - 2013 .................................... 23 3.5 Water Right .................................................................................................................... 24 3.5 Combined Hydrologic Data Set ..................................................................................... 26

SECTION 4 – ENVIRONMENTAL STUDIES AND RESOURCES ......................................... 30 4.1 Recent Studies Summary ............................................................................................... 30 4.2 Environmental Resources Summary .............................................................................. 32

4.2.1 Aquatic Resource Studies ........................................................................................ 32 4.2.2 Terrestrial Resource Studies – Wildlife ................................................................... 33 4.2.3 Terrestrial Resource Studies – Botanical ................................................................. 35 4.2.4 Recreation and Land Use ......................................................................................... 35 4.2.5 Scenery Resources Study ......................................................................................... 37 4.2.6 Cultural Resource Study .......................................................................................... 38

4.3 Environmental Resource Considerations During Project Construction & Operations .. 38 SECTION 5 – 2013 BATHYMETRIC SURVEY OF TAKATZ LAKE ..................................... 41

5.1 2013 Survey Program ..................................................................................................... 41 5.1.1 Bathymetric Survey ................................................................................................. 42 5.1.2 Sub-bottom Geophysical Conditions ....................................................................... 44

SECTION 6 – GEOTECHNICAL ASSESSMENT ..................................................................... 55 6.1 Regional Geology ........................................................................................................... 55


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6.2 Powerhouse Site Considerations .................................................................................... 62 6.3 Geotechnical Summary .................................................................................................. 63

SECTION 7 – TRANSMISSION LINE ....................................................................................... 64 7.1 Route Alternatives .......................................................................................................... 64

7.1.1 Commonwealth 2010 Transmission Line Study ...................................................... 64 7.1.2 Commonwealth 2011 Transmission Line Study ...................................................... 65

7.2 Recommended Transmission Alignment ....................................................................... 72 SECTION 8 – PROJECT DEVELOPMENT ALTERNATIVES ................................................ 74

8.1 Alternative Selection Goals ............................................................................................ 74 8.2 Project Hydraulic Capacity ............................................................................................ 74 8.3 Powerhouse Site Alternatives......................................................................................... 76 8.4 Access Dock Location Alternatives ............................................................................... 78 8.5 Dam and Intake Alternatives Considered ....................................................................... 79 8.6 1968 Plan of Development ............................................................................................. 80 8.7 Phased Development – Phase 1 Lake Tap ..................................................................... 82 8.8 Vertical Shaft and Upper Tunnel Portal ......................................................................... 84 8.9 Lower Tunnel Alternatives ............................................................................................. 86 8.10 Phased Development - Phase 2 Access Road Extension and Dam ............................ 86 8.11 Single Stage Development with Surface Intake ......................................................... 87

SECTION 9 – POWER OPERATIONS STUDIES ................................................................... 107 9.1 Existing Sitka Electric System ..................................................................................... 107 9.2 Reservoir Operations Models ....................................................................................... 107 9.3 Reservoir Mass Balance Model .................................................................................... 107

9.3.1 Green Lake Mass Balance Rule Curves ................................................................. 108 9.3.2 Blue Lake Mass Balance Rule Curves ................................................................... 110 9.3.3 Takatz Reservoir Mass Balance Rule Curves ........................................................ 111

9.4 Reservoir Energy Storage Estimates ............................................................................ 113 9.5 Generation Model Runs ............................................................................................... 116

9.5.1 Takatz Operations Model Development ................................................................ 116 9.5.2 Model Data............................................................................................................. 116 9.5.3 Operating Scenarios Considered ............................................................................ 118 9.5.4 Model Study Methodology .................................................................................... 119 9.5.5 Model Study Results .............................................................................................. 119

9.6 Integration of Takatz Project Output in Sitka System .................................................. 129 9.7 Future Operations Modeling ........................................................................................ 130 9.8 Takatz Project Operation within a Future Regional Electric Grid ............................... 131

SECTION 10 – CONSTRUCTION COST ESTIMATES.......................................................... 132 10.1 Methodology ............................................................................................................. 132 10.2 Principal Cost Components for Project Development .............................................. 133 10.3 Project Alternatives Cost Summary ......................................................................... 134

10.3.1 Overhead Transmission Line Construction Cost Estimate .................................... 135 SECTION 11 – RECOMMENDED DEVELOPMENT PLAN ................................................. 142

11.1 Evaluation of Alternatives ........................................................................................ 142 11.2 Recommended Project Arrangement Phase 1 (Lake Tap, Tunnel System, & Powerhouse / Switchyard Location) ....................................................................................... 143

11.2.1 Powerhouse Site Options & Tunnel Alignments ................................................... 143


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11.2.2 Powerhouse Structure ............................................................................................ 144 11.2.3 Selected Turbine Generating Equipment ............................................................... 144 11.2.4 Transformers, Switchyard and Controls ................................................................ 145

11.3 Phase 1 Site Support Facilities ................................................................................. 146 11.3.1 Standby Diesel Generator ...................................................................................... 146 11.3.2 Operations and Storage Building ........................................................................... 146 11.3.3 Housing and Maintenance Building....................................................................... 146

11.4 Recommended Project Arrangement: Phase 2 – Dam .............................................. 147 11.4.1 Access Road Extension .......................................................................................... 147 11.4.2 Arch Dam ............................................................................................................... 147

11.5 Phased Development Schedule ................................................................................. 148 SECTION 12 – OPERATION AND MAINTENANCE (O&M) ............................................... 160

12.1 Project Setting........................................................................................................... 160 12.2 Operations and Maintenance Plan ............................................................................ 160 12.3 Seasonal Operating Strategy ..................................................................................... 161 12.4 Operations and Maintenance Cost Projections ......................................................... 162

12.4.1 O&M Staffing and Logistics .................................................................................. 162 12.4.2 Major Maintenance and Renewals Costs ............................................................... 163

SECTION 13 – INTEGRATION OF TAKATZ PROJECT IN REGIONAL GRID ................. 165 13.1 Future Southeast Alaska Regional Grid ................................................................... 165 13.2 Interconnection to the South ..................................................................................... 165 13.3 Interconnection to the North ..................................................................................... 166 13.4 Submarine Cable Description ................................................................................... 166 13.5 DC Alternative .......................................................................................................... 167

REFERENCES AND BIBLIOGRAPHY ................................................................................... 169 APPENDICES ............................................................................................................................ 172 APPENDIX A – DRAFT FERC EXHIBIT A ............................................................................ A-1 APPENDIX B – DRAFT FERC EXHIBIT B ............................................................................ B-1 APPENDIX C – CONSTRUCTION COST ESTIMATES ........................................................ C-1

C.1 Background .................................................................................................................. C-2 C.1.1 Estimation of Overhead Transmission Line Bid Item Costs ................................. C-2

C.2 Methodology and Assumptions .................................................................................... C-2 C.2.1 Materials and Supplies Totals Report .................................................................... C-3 C.2.2 Subcontractors and Fees Totals Report .................................................................. C-3 C.2.3 Equipment Totals Report ....................................................................................... C-3 C.2.4 Labor Totals Report ............................................................................................... C-3 C.2.5 Activity Unit Price Summary ................................................................................. C-3

APPENDIX D – PHOTO SUMMARY ...................................................................................... D-1 APPENDIX E – TECHNICAL REPORTS ................................................................................. E-1 APPENDIX F – AGENCY COMMENTS .................................................................................. F-1


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LIST OF FIGURES Figure Title Page

Figure 2-1 Takatz Lake Project Location ................................................................................... 8 Figure 3-1 Takatz Lake Estimated Runoff per sq. mile, from 1968 Study .............................. 15 Figure 3-2 Flow Correlation between Takatz Creek and Sawmill Creek, from 1968 Study .... 16 Figure 3-3 Flow Gage Location Map ....................................................................................... 25 Figure 3-4 Comparison of 2009 - 2013 Gage Record to APA Estimated Hydrology .............. 26 Figure 3-5 Takatz Lake Flow Exceedance Curve, 10.8 sq mi Drainage Area ......................... 27 Figure 5-1 Bathymetric and Geophysical Survey Instrumentation Schematic ......................... 41 Figure 5-2 Takatz Lake, 2013 Computed Area-Capacity Curve .............................................. 43 Figure 5-3 Lake Bottom Coverage for 2013 Bathymetric & Geophysical Survey .................. 46 Figure 5-4 Takatz Lake Bathymetric Plan – Western Half ...................................................... 47 Figure 5-5 Takatz Lake Bathymetric Plan – Eastern Half ........................................................ 48 Figure 5-6 Takatz Lake Sun-Illuminated Plan – Western Half ................................................ 49 Figure 5-7 Takatz Lake Sun-Illuminated Plan – Eastern Half ................................................. 50 Figure 5-8 Takatz Lake Bottom Sediment Thickness – Western Half ..................................... 51 Figure 5-9 Takatz Lake Bottom Sediment Thickness – Eastern Half ...................................... 52 Figure 5-10 Lake Tap and Upper Tunnel Plan ........................................................................... 53 Figure 5-11 Takatz Lake Bottom Sediment Thickness – Longitudinal Profile .......................... 54 Figure 6-1 Air Photo Showing Lineation at East End of Takatz Lake ..................................... 55 Figure 6-2 Geologic Map (USGS) at East End of Takatz Lake ............................................... 56 Figure 6-3 General Layout of Upper Tunnel and Lake Tap ..................................................... 58 Figure 6-4 Faults Near Baranof Island ..................................................................................... 59 Figure 6-5 Earthquake History ................................................................................................. 60 Figure 6-6 Southeast Seismicity ............................................................................................... 60 Figure 6-7 2%, 50 Year Probability of Occurrence .................................................................. 61 Figure 7-1 Transmission Line Route Alternatives, Vicinity Map ............................................ 67 Figure 7-2 Transmission Line Route A Alignment (1 of 4) ..................................................... 68 Figure 7-3 Transmission Line Route A Alignment (2 of 4) ..................................................... 69 Figure 7-4 Transmission Line Route A Alignment (3 of 4) ..................................................... 70 Figure 7-5 Transmission Line Route A Alignment (4 of 4) ..................................................... 71 Figure 8-1 Takatz Bay Area Site Plan ...................................................................................... 89 Figure 8-2 Powerhouse and Switchyard Site Plan Options ...................................................... 90 Figure 8-3 Lower Tunnel Alignment Plans (Options 1 & 2) .................................................... 91 Figure 8-4 Lower Tunnel Profile (Powerhouse Site Option 1) ................................................ 92 Figure 8-5 Lower Tunnel Profile (Powerhouse Site Option 2) ................................................ 93 Figure 8-6 Water Depth Plan of Takatz Bay ............................................................................ 94 Figure 8-7 Takatz Project Plan and Profile, (from 1968 Study) ............................................... 95 Figure 8-8 Takatz Lake Dams, Plan, Sections, and Elevations, (from 1968 Study) ................ 96 Figure 8-9 Takatz Lake Powerhouse, Plans and Sections, (from 1968 Study) ........................ 97 Figure 8-10 Reservoir and Power Operations, (from 1968 Study) ............................................. 98 Figure 8-11 Lake Bottom Sediment and Lake Tap Plan ............................................................ 99 Figure 8-12 Lake Bottom Longitudinal Sediment Profile ........................................................ 100 Figure 8-13 Access Road Plan – North .................................................................................... 101 Figure 8-14 Access Road Plan – South .................................................................................... 102


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Figure 8-15 Upper Tunnel and Vertical Shaft Plan .................................................................. 103 Figure 8-16 Upper Tunnel and Vertical Shaft Profile .............................................................. 104 Figure 8-17 Upper Tunnel Valve Chamber Plan and Section .................................................. 105 Figure 8-18 Phase 2 Dam and Staging Area Plan .................................................................... 106 Figure 9-1 Rule Curves for Green Lake Reservoir ................................................................. 109 Figure 9-2 Rule Curves for Blue Lake Expansion Reservoir ................................................. 111 Figure 9-3 Mass Balance Rule Curves for Takatz Lake ......................................................... 113 Figure 9-4 Takatz Project 1968 Plan of Development – Reservoir Haze Chart ..................... 120 Figure 9-5 Takatz Project Phase 1 Development – Reservoir Haze Chart ............................. 121 Figure 9-6 Takatz Project Phase 2 Development – Reservoir Haze Chart ............................. 122 Figure 9-7 Takatz Project Single Stage Development – Reservoir Haze Chart ..................... 123 Figure 11-1 Recommended Project Plan .................................................................................. 149 Figure 11-2 Recommended Project Tunnel Profile .................................................................. 150 Figure 11-3 Recommended Lake Tap Location Plan ............................................................... 151 Figure 11-4 Recommended Upper and Lower Tunnel Alignment Plan ................................... 152 Figure 11-5 Recommended Lower Tunnel & Site Plan ........................................................... 153 Figure 11-6 Recommended Powerhouse Area & Access Road Site Plan ................................ 154 Figure 11-7 Powerhouse Mechanical and Electrical Plan ........................................................ 155 Figure 11-8 Powerhouse Transverse Section ........................................................................... 156 Figure 11-9 Operations and Storage Building Floor Plan ........................................................ 157 Figure 11-10 Housing & Maintenance Building Plan & Elevation ........................................... 158 Figure 11-11 Conceptual One Line Diagram ............................................................................. 159 Figure 13-1 Future Regional Intertie Map ................................................................................ 168


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LIST OF TABLES Table Title Page

Table 1-1 Takatz Project Development Alternatives ................................................................ 5 Table 3-1 Seasonal Runoff Distribution for Takatz Lake (APA 1968 Study) ........................ 13 Table 3-2 Monthly Flow Correlation: Takatz Creek to Sawmill Creek, from 1968 Study ..... 17 Table 3-3 Computed Inflow to Takatz Lake 1946 to 1964 Water Years - 1968 Study .......... 18 Table 3-4 Takatz Creek Estimated Monthly Average Flows .................................................. 20 Table 3-5 Takatz Lake Estimated Monthly Average Inflows (with Saddle Dam) .................. 21 Table 3-6 Takatz Lake Estimated Monthly Average Inflows (without Saddle Dam) ............. 22 Table 3-7 Takatz Lake Outflows 2009 – 2013, based on USGS Gage 15099900 .................. 23 Table 3-8 Takatz Lake Monthly Average Inflows (without Saddle Dam), 28-Year Record .. 28 Table 3-9 Takatz Lake Monthly Average Inflows (with Saddle Dam), 28-Year Record ....... 29 Table 4-1 Summary of Project Environmental Studies ........................................................... 31 Table 5-1 Control Coordinates ................................................................................................ 42 Table 6-1 Rock Properties Anticipated in Excavations at the Takatz Project ......................... 57 Table 8-1 Summary of Project Statistics & Design Criteria for Development Alternatives .. 80 Table 8-2 Summary of Alternatives Investigated by APA, 1968 Report ................................ 81 Table 9-1 Monthly Distribution of Reservoir Inflows and Sitka Electric Loads .................. 108 Table 9-2 Mass Balance Operation of Green Lake Reservoir, Monthly Level Changes ...... 109 Table 9-3 Mass Balance Operation of Blue Lake Reservoir, Monthly Level Changes ........ 110 Table 9-4 Mass Balance Operation of Takatz Reservoir, Monthly Level Changes .............. 111 Table 9-5 Estimated Reserve Storage Volumes and Stored Energy for Takatz, Blue Lake and

Green Lake .......................................................................................................................... 115 Table 9-6 City of Sitka, Monthly Distribution of Electric System Loads ............................. 117 Table 9-7 Takatz Lake Elevation vs. Storage Relationship .................................................. 117 Table 9-8 Takatz Powerhouse Turbine Performance Data – Unit 1 ..................................... 118 Table 9-9 Recommended Takatz Reservoir Capacities ........................................................ 118 Table 9-10 Project Generation Summary, Alternative 1 - 1968 Plan of Development ........... 125 Table 9-11 Project Generation Summary, Alternative 2 - Phase 1 Development ................... 126 Table 9-12 Project Generation Summary, Alternative 2 – Phase 2 Development .................. 127 Table 9-13 Project Generation Summary, Alternative 3 – Single Stage Development .......... 128 Table 10-1 Project Development Alternatives Cost Summary ............................................... 134 Table 10-2 Alternative No. 1 Concept Project Development Cost Estimate .......................... 137 Table 10-3 Alternative No. 2, (Phase 1 only) Concept Project Development Cost Estimate . 138 Table 10-4 Alternative No. 2, (Phase 2 only) Concept Project Development Cost Estimate . 139 Table 10-5 Alternative No. 2, (Phases 1 & 2) Concept Project Development Cost Estimate 140 Table 10-6 Alternative No. 3 Concept Project Development Cost Estimate .......................... 141 Table 11-1 Energy and Capacity Costs for Development Alternatives .................................. 142 Table 11-2 Recommended Takatz Powerhouse Installed Capacities (by Project Phase) ....... 144 Table 12-1 Estimated Operations and Maintenance Staffing Budget for Takatz Project ....... 163 Table C-1 Concept Level Estimation of Direct Construction Costs ...................................... C-5


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SECTION 1 – EXECUTIVE SUMMARY 1.1 Background Takatz Lake represents one of the best hydroelectric development sites on Baranof Island, with a lake perched at El. 905 ft about a mile from tidewater. The Project was studied extensively by the Alaska Power Administration (APA) in the 1960’s. The site has not been developed mainly due to its remote location, about 18 miles from Sitka on the eastern shore of Baranof Island. In September, 2008, the City and Borough of Sitka (the City) obtained a Federal Energy Regulatory Commission (FERC) preliminary permit (FERC No. P-13234) to study the possible development of Takatz Lake as a hydroelectric generation project. Since 2009, the City has completed a series of site surveys, hydrological analyses, environmental studies, and engineering assessments in and around Takatz Lake and along the electrical transmission corridor to Sitka. This Appraisal Study Report provides a summary of the historical studies conducted, our evaluation of alternatives for developing the dam and powerplant site, and a concept level cost estimate for our preferred development alternative. 1.2 Objectives The objectives of the Appraisal Study were to 1) develop, based on technical feasibility, a number of development alternatives for the power generating facilities of the Project; i.e., the dam, power conduit and powerhouse and 2) select a Preferred Alternative based on a combination of technical feasibility, energy generation and cost. In addition, we evaluated environmental factors to determine which might affect issuance of necessary licenses and permits, or which might affect project operations and/or economics. A key element of the Appraisal Study was an examination of whether a phased development of the project is feasible. Construction in phases could reduce initial capital costs while still allowing full development of the site, when electric loads increases merit this. This study sought to confirm that a phased development of the Takatz Lake Project would be technically feasible and cost effective, compared to alternatives previously developed for the Takatz site. 1.3 Hydrology, Environmental Studies and Constraints With the new stream gage at the outlet of Takatz Lake, the City was able to significantly improve the hydrologic record for Takatz Lake. Prior studies relied on an 18 year record based only on estimated data for sites away from the lake outlet. The improved record spans 28 years including 5 years of actual gage data at the lake outlet. The estimated average outflow from Takatz Lake is 169 cfs based on this 28 year record. A synopsis of the environmental studies is included at Section 4 and the historical reports are available as an appendix to this report. The upper reaches of Takatz Creek are free of salmonid species, due to a barrier falls 0.73 stream miles (SM) from the mouth of the creek. Takatz Lake does not have a native fish population due to the heavy sediment load in the lake and a lack of habitat and food. Dolly Varden have been observed in the middle reaches of Takatz Creek, below


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the lake, where tributaries contribute additional inflow. This area also provides habitat for wildlife and birds. Redirecting flow from Takatz Lake through a power tunnel to a powerhouse at tidewater would reduce flow in these middle reaches. Additional environmental studies have been recommended to gain a better understanding of contribution flows along Takatz Creek. Recreational and aesthetic resources would be impacted by the development of the Takatz Project in an otherwise undisturbed remote area. Local communities (Sitka, Baranof Warm Springs) and some area businesses have voiced opposition to the Project, mainly related to the electric transmission line route across the island and the possible future road from Sitka to the Baranof Hot Springs area. The 2008 Tongass National Forest Land and Resource Management Plan (Forest Plan) and the Roadless Rule may continue to restrict certain types of development associated with a hydropower project, such as roads. However, a transportation utility system (TUS) Land Use Designation (LUD) overlay does exist for a potential power transmission and proposed state road corridor across Baranof Island. The proposed Takatz transmission line is situated within this corridor over part of its length. Also, the 2005 Federal Highway SAFETEA-LU Act (Public Law 109-59) established a similar transportation corridor across the island. Limits within the TUS LUD have not been clarified by the Forest Service, U.S. Departement of Agriculture (Forest Service), and will require consultation. The transmission line has been the source of most major environmental concerns because of its potential inconsistency with the Forest Plan restrictions. Public opposition has centered more on transmission than on generation facilities. Construction and operation of the generating facilities, while challenging and costly due to remoteness and terrain, could have reduced environmental impacts relative to other locations in southeast Alaska. This is based on the following findings from several years of environmental study:

Takatz Lake and Takatz Creek upstream of the lake support no fish populations; Takatz Creek above a barrier falls near tidewater harbors no anadromous fish populations; Salmon populations in Takatz Bay should not be significantly impacted; There are no potentially-affected threatened or endangered species in the Project area; No significant cultural resources were found within the proposed footprint of the

generation and proximal transmission facilities. It is expected, however, that more environmental issues will arise as field surveys extend beyond the rather limited areas examined up to the time of this report. It is already known that there are wetlands in the area, and that certain Project features, as designed, are not consistent with the scenic integrity objectives of the Forest Plan Land Use Designations. 1.4 Project Development Alternatives This study examined three main alternatives for development of the Takatz site, see Table 1-1. These include:


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Alternative 1: The “1968 plan of development” which is slightly modified from the APA’s 1968 recommended plan of development. In Alternative 1 we eliminated the surface penstock and surge chambers which were proposed in 1968 and we modified the tunnel alignments.

Alternative 2: A phased development of the Project which sought to reduce the initial capital cost of the project. This option includes the Phase 1 development of a lake tap, tunnel, powerhouse, and site support facilities, with no dam constructed. Phase 2 of this alternative would include the future addition of a dam to increase the average generation and greatly expand the project’s storage capacity.

Alternative 3: A single-stage development similar to the 1968 APA plan, with a lower main dam, to avoid construction of the saddle dam initially proposed.

All alternatives include a two-unit powerhouse with a nominal hydraulic capacity of 450 cfs, a dock in Takatz Bay with an 800-ft access road to the powerhouse site, support facilities in the powerhouse area, and an 18-mile long, primarily overhead transmission line to Sitka. 1.5 Power Operations Studies The power operations studies estimated both the required reservoir storage capacity of the Takatz Project and the likely energy generation of each development alternative, using the updated hydrology. Comparisons to the storage volume, reserve energy and annual rule curves of the City’s Blue Lake and Green Lake Projects show that each of the three alternatives would provide sufficient storage to effectively regulate inflows to Takatz Lake. Average annual generation from the project would range from 87,500 MWH to 102,600 MWH per year, depending on the alternative selected. The very large reservoir storage volumes possible with the 1968 APA Plan and the Phase 2 development would allow the Takatz Project to provide significant carry-over energy storage for use during dry years or system emergencies. 1.6 Construction Cost Estimates The Takatz site’s remote location will make it a challenging project to develop. The high elevations, lack of road access, avalanche risk, and extreme terrain along the transmission line route all combine to make the transmission line construction a costly element of the project. This study included a contractor’s style cost estimate with development of mobilization plans, staging, crew types, and a preliminary construction schedule to estimate the overall cost of construction. Our estimates indicate that the project’s total construction cost may range from $298 million to $436 million (2014$), depending on the development plan selected, with a cost per kW of installed capacity ranging from $11,900 to $14,880 per kW. 1.7 Recommended Development Plan Major statistics for the three alternatives examined in this study are shown in Table 1-1. This table shows that the Phased development of the Takatz site offers the best combination of reduced initial investment, adequate reservoir storage and annual energy generation. Phase 1 of this development would include a lake tap intake, approximately 5,700 feet of tunnel, a 25 MW powerhouse, and an


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18 mile transmission line from the Project to the City of Sitka. This initial development would provide 70,200 MWH of firm energy with an average annual energy of 87,500 MWH. The total project cost for this Phase 1 development is estimated at $298 million. The initial Phase 1 construction would increase the City’s installed hydropower capacity by 75% (from 33 MW to 58 MW) with a 57% increase in average annual energy generation, increasing the system’s hydro generation from 156,000 MWH to 243,000 MWh per year. Phase 2 of this development alternative would increase energy generation by a modest 7% to 93,840 MWH but would greatly increase the project’s carry-over energy storage. This long-term storage capability may have significant future value to the City of Sitka or to a regional electric system. The Southeast Alaska Power Agency (SEAPA) transmission system currently ties the Ketchikan/Saxman area to Wrangell and Petersburg. A transmission extension to the Kake area is in the permitting stage. Completion of the transmission extension to Kake will bring an interconnection opportunity for the Takatz Project. Kake is approximately 40 miles east of Takatz Bay. An interconnection to Kake would require 35 miles of submarine cable plus a short length of overhead line and associated termination facilities at each end. 1.8 Future Studies Development of the Takatz Project will require a series of site investigations for geotechnical conditions at the intake area, dam site, tunnel alignments, powerhouse area, and along the transmission line. The transmission line portion of the project will also require further studies by meteorologists and avalanche specialists to evaluate and refine wind/ice design criteria and to define specific avalanche locations/risk. The meteorologist and avalanche specialists would recommend appropriate mitigation measures that can be incorporated into the transmission line design. Additional environmental and engineering studies will likely be required as part of a FERC license application process and to confirm the optimum arrangement and design of the Project elements. Both engineering and environmental studies should be completed according to a timeline based on the FERC licensing process and the final design/procurement/construction program. In early 2015 the City of Sitka will complete the Blue Lake Expansion Project, boosting Sitka’s average annual hydro energy generation to 156 million MWH, vs. a current annual system load of about 120 million MWH. Thus, development of the Takatz Project is not an urgent priority for the City. It likely will require a period of years before the City’s system energy demand sufficiently exceeds the available hydro energy by a large enough margin to merit development of the Takatz Project. A comprehensive electrical load analysis and load development plan will be needed to ensure that a sufficient demand for power is present when the Taktaz Project is ultimately completed. The isolated nature of Sitka’s electric grid makes this a particular challenge. A regional intertie to the Ketchikan area may greatly facilitate the City’s ability to market the project’s energy and may ultimately provide the impetus for development of the Takatz Lake Hydroelectric Project.


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Table 1-1 Takatz Project Development Alternatives

(Summary of Project Characteristics, Annual Energy Generation, & Estimated Costs)

Alternative: No. 1 No. 2 No. 2 No. 2 No. 3

Basic Project Plan Description: 1968 APA Phase 1 only Phase 2 only Phases 1&2 Single-Stage

Intake Type (Invert Elev, mllw1) Conv (880) Lake Tap (717) NA Lake Tap (717) Conv (860)

Main Dam Crest El. (ft mllw) 1040 None 990 990 990

Lake Minimum WSEl (mllw) 900 747 747 747 890

Lake Maximum WSEl (mllw) 1040 905 990 990 990

Active Storage (ac-feet) 80,910 52,970 44,605 97,575 50,643

Main Dam Max WSEl (mllw): 1040 NA 990 990 990

Saddle Dam Max WSEl (mllw): 1040 NA NA NA NA

Installed Gen. Capacity (MW): 29.3 25.0 4.2 29.2 27.8

Annual Energy Firm (MWH): 94,354 70,221 19,406 89,627 79,277

Annual Energy Avg (MWH): 102,558 87,548 6,292 93,840 98,691

Est. Total Construction Cost2,3 ($M): $372 $254 $81 $309 $307

Est. Other Project Costs4 ($M) $64 $44 $15 $54 $54

Est. Total Project Cost2,3 ($M): $436 $298 $96 $363 $361

Installed Cost per kW, $ $14,880 $11,920 $24,000 $12,430 $12,980

Capital Cost per firm annual MWH, $ $4,620 $4,240 $4,950 $4,050 $4,550

Notes:1. Mean Lower Low Water (mllw) is Southeast Alaska datum.2. Includes state and local sales taxes (if applicable), equipment markups, Contractors overhead and profit, and construction bonding and construction loan financing.3. Does not include interest costs during construction, legal services, land acquisition or easement costs. Costs are based upon concept level design, and should be considered accurate to within -20% to +30%.4. Includes geotechnical investigations (for both transmission line and hydro projects), all design engineering services, environmental studies and permitting services (for both transmission line and hydro projects), FERC licensing services, bid and construction management services, and Owner's administration needs. Does not include cost of mitigation and enhancements possibly required by the FERC license.


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SECTION 2 – INTRODUCTION 2.1 Project Setting Takatz Lake is located on Baranof Island about 18 miles east of Sitka. The lake location relative to Sitka and the proposed transmission line route are shown in Figure 2-1. This figure represents the City’s initial proposal for project development at the time of their Preliminary Application Document, filed with the Federal Energy Regulatory Commission (FERC) in late 2009. Takatz Lake represents one of the most attractive hydropower development sites on Baranof Island, with a high glacial-fed lake near tidewater. The 400 acre lake is at El. 905 ft, with a lake outlet less than one mile from tidewater on Takatz Inlet. The site has been studied previously and has been generally characterized as both technically and environmentally feasible. However, Takatz Lake has not yet been developed primarily due to its remote location relative to the nearest electric loads in Sitka, Alaska. 2.2 Study Scope The City and Borough of Sitka, Alaska (Sitka or the City) currently holds a Federal Energy Regulatory Commission (FERC) preliminary permit to study the potential development of a hydroelectric site at Takatz Lake. A series of mapping, environmental, and engineering feasibility studies were undertaken in the 2009 to 2013 time frame to help define the impacts, technical feasibility, and cost of the Takatz Lake Project. These studies included environmental resource studies in the project area and transmission line corridor, bathymetric surveys of Takatz Lake, and hydrology-power operations studies to define an optimum reservoir storage capacity and installed generating capacity for the Project. As part of these current studies the City sought to confirm whether the arrangement of the Project’s generating facilities, as proposed in past engineering studies, is still appropriate for the City’s future needs. These needs include the possible phased development of the Project to defer capital costs where possible. Also, these studies examined the optimum arrangement of the Takatz generating facilities, if the Project were to be interconnected to communities other that Sitka in Southeast Alaska. Beginning in 2014, Sitka’s electric loads will be served by a fundamentally different set of generation resources compared to the City’s 1960’s electric system. The current generating resources include: the Green Lake hydro plant (16 MW capacity); a recently expanded Blue Lake hydro project (15.9 MW capacity to be on-line in 2014); and 27 MW of back-up diesel generators owned by the City. The Alaska Pulp Corporation (APC) pulp mill closed in 1993 and is no longer a source of generation for the City. In 2013 the City commissioned Currents Consulting to review the appropriate reservoir storage capacity, hydraulic capacity, installed megawatts, and number of generating units for the Takatz Lake development. A basic goal of this study is to determine what reservoir storage capacity and generating capability is most appropriate at Takatz to both develop its hydrologic resource and to augment the City’s existing hydro generation resources.


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The 2013 study effort included:

Expansion of the Takatz Creek hydrology data set to include 2008 to 2013 flow data, Updated power operations runs with the new hydrology, Confirmation of the recommended powerhouse location, A feasibility review of a possible lake tap in Takatz Lake, and Summaries of the environmental resources and constraints in the Project area, as defined

by the 2009 through 2013 resource study programs. Reconnaissance level cost estimates for various development alternatives.

This study was authorized by City of Sitka Purchase Orders 14-0000027 and 14-0000440, dated July 3, 2013 and October 17, 2013, respectively. Paul Carson of Currents Consulting, Matt Moughamian of McMillen LLC and Mike Frantz of MF Solutions led the study team identified in this report. Our appraisal study work is based on the following resources:

The 1968 Department of Interior (Alaska Power Administration) Study report, The Currents Consulting, 2011 Project Capacity Analysis Study Report, USGS stream flow records for Takatz Creek, Modern topographic maps developed from a 2009 LiDAR survey of the Takatz Lake area, The 2013 bathymetric and sub-bottom geophysical surveys of Takatz Lake, prepared by

David Evans and Associates, A preliminary on-site tour and visual assessment of Takatz Bay and Takatz Lake conducted

by P. Carson, K. de Rubertis, and M. Moughamian, and A series of environmental resource reports, as described in Section 4.

Confirming the final technical feasibility of the Project arrangement recommended in this study will require site investigations and final engineering feasibility studies. Specific recommendations for follow-on investigations and studies are included in Section 14 of this report.

Takatz Lake Hydroelectric Appraisal Study October2014

8

Figure 2-1 Takatz Lake Project Location

Source: City and Borough of Sitka Electric Department, FERC Preliminary Application Document, 2009.


9

2.3 Reference Documents and Prior Engineering Studies The first known assessment of the hydropower potential at Takatz Lake is the seminal 1947 report “Water Powers, Southeast Alaska” prepared by the Federal Power Commission and U.S. Forest Service. That study suggested a 15,000 hp (11 MW) facility could be constructed at Takatz along with a “drawdown tunnel” and 75 ft high dam near the lake outlet. The authors estimated that an active storage volume of 80,000 ac-ft would be required for “complete regulation” of the lake inflows. This led to their suggestion of a reservoir operating range between El. 767 and the top of dam at El. 1,002. These levels were expected to provide the suggested “complete regulation” of the lake’s storage volume. This 1947 study was used as a reference in estimating a suitable reservoir storage volume at Takatz. This historical study was also used as a benchmark for comparing the reservoir capacity and generating capability of other projects in the Southeast Alaska region. The primary development plan reference for this 2013 study work is the: “Plan of Development, Takatz Creek Project, Alaska” by the Alaska Power Administration, U.S. Department of the Interior dated January 1968, which is herein referred to as “the 1968 Study”. That proposed project development and its supporting appendices were the result of a comprehensive investigation of the Takatz Creek site, undertaken in the 1965 to 1967 time frame. The study included field investigations of hydrology and geology at the site, preliminary design of the project facilities, and power studies which predicted firm and average annual energy from the Project. See Section 8 for a summary and figures from the 1968 Study. Topographic maps were developed in 2010 for the Takatz Lake area. These maps were developed from a LiDAR aerial survey conducted on September 29, 2009 by Aero-Metric, Inc., Anchorage, AK under contract to the City of Sitka (Aero-Metric job no. 6090905). Satellite images used in development of the City’s GIS database for the Takatz area were also used as reference documents in this study work. Bathymetric mapping of Takatz Lake was completed by David Evans and Associates (DEA), Portland OR, in July 2013. Using the bathymetric survey, merged with above-water topographic data, DEA developed topographic mapping and a reservoir area-capacity curve for the project, which were used in this 2013 Appraisal study. The DEA mapping work included sub-bottom geophysical surveys of the lake to assess how much sediment and loose material may overlay areas where an underwater lake tap might be located. Our assessment of the feasibility of a lake tap and its likely location within the lake are based on the information gathered by DEA. 2.4 Engineering Site Assessment In July, 2013, Paul Carson (Currents Consulting), Kim DeRubertis, Matt Moughamian (McMillen LLC), and Karl Wolfe (City subcontractor) conducted a one-day on-site preliminary site investigation to better understand the engineering limitations and constraints of the Takatz Lake project. The site visit included a float-plane landing at near high-tide in the tidewater bay for a visual survey of the bay, powerhouse and ancillary facilities area. The team also flew to the lake


10

to perform a visual on-ground survey of the inlet delta located on the west end of the lake and the dam site areas at the west end of the lake. 2.5 Hydrology Hydrology data for Takatz Creek at the outlet of Takatz Lake (USGS gage 15099900) is available from the USGS only for the period from November 2008 to present. Prior to 2008 the only recorded flows in the Takatz basin were at the mouth of Takatz Creek, (USGS gage 15110000) which was in place from 1951 to 1969. The hydrology data set used in the 1968 study included an 18 year record, comprised of 4 years of estimated flow developed from a correlation with Sawmill Creek (near Sitka) and 14 years of estimated flows at the lake outlet based on a correlation of the drainage areas at the mouth of Takatz creek vs. the outlet of the lake. The hydrology data for this 2013 study effort was extended to include 9 years of additional streamflow data (four years of estimated flows for 1965 thru 1968 and five years actual flows for 2008 to 2013). Details of the changes made by the USGS in the hydrology record, the recent 5 years flow measurements, and the estimated flows available for power generation are described in detail in Section 3 of this report. 2.6 Development Alternatives Considered Three primary alternatives were evaluated for development of power generating facilities at the Takatz Lake site. These include:

A full development of the site, based upon the 1968 development plan. This would include both a main dam and saddle dam at the outlet of the lake creating a maximum lake water surface level of El. 1040 ft. A tunnel and penstock system would lead from the lake to a leading to a two-unit 29.3 MW powerhouse at tidewater.

A phased development of the site, using a lake tap in Phase 1 to defer the cost of constructing a dam at the lake outlet. This lake tap would allow regulation of lake levels between El. 747 ft and El. 905 ft. The Phase 1 configuration would include a two-unit powerhouse at tidewater rated at 25 MW. The Phase 2 construction would include extending the access road to the lake and building a dam to raise the maximum lake level from El. 905 ft to El. 990 ft. This increase in operating head would boost the generating capacity of the project to 29.2 MW.

A single-stage development of the site with a single dam and a conventional tunnel intake structure. In this alternative the lake operating levels would range from El. 900 to 990 ft, the dam’s spillway level. A two-unit 27.8 MW powerhouse would be included with this alternative.

For all of the above alternatives, a common transmission line arrangement has been considered. This transmission system is based upon the transmission corridor, structure types and connection points as described for the Project by Commonwealth Associates, Inc. in a feasibility study completed in 2012.


11

2.7 Power Operations Studies Power Operations studies were completed for each alternative developed in this study. These analyses defined likely rule curves for operation of each alternative, aimed at shaping the annual generation from the Project to fit the annual load shape of the Sitka electrical system. These power studies considered the Takatz Project operation both as a stand-alone project and integrated with operation of the City’s existing Blue Lake and Green Lake hydro projects. Simulations evaluated the average and firm energy from Takatz Lake with the reservoir storage volumes developed by each alternative. Section 9 describes this detailed analysis and the results for each alternative. 2.8 Cost Estimates Construction cost estimates were developed for each development alternative. Costs were based on recent southeast Alaska projects, either recently bid or in construction, along with vendor budgetary pricing provided for the turbine-generator equipment. Cost estimates developed by Commonwealth Associates, Inc. in 2012 for the cross-island transmission line were based on a 2012 construction period and were adjusted for inflation (at 3% per year) to establish the estimated transmission system cost. In addition to estimated direct construction costs, estimates were developed for engineering, permitting, construction management, and regulatory costs to help define a likely range for the overall development cost of the Project.


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SECTION 3 – HYDROLOGY 3.1 Overview In 2013, for the first time, sufficient direct streamflow measurements were available at the outlet of Takatz Lake to establish actual outflows from Takatz Lake and the energy potential of a hydroelectric development at Takatz Lake. This new data includes daily streamflow records from USGS Gage No. 15099900 (Takatz Creek at Takatz Lake Outlet near Baranof AK), for the period from October 2008 through 2013. The overall hydrology data set used in this Appraisal study includes these five years of direct measurements, combined with adjustments of the estimated hydrology data developed by the APA in the 1960’s. Streamflow data for the Takatz Creek Basin have historically been quite limited. The outflow from the mouth of Takatz Creek near tidewater (USGS gage No. 15100000) was originally gaged from July 1951 to September 1969. Over the initial 18 year period the average annual discharge from the basin was 256 cfs. The drainage area at this gage is 17.5 square miles, which is 62% larger than the 10.8 square mile drainage area at the outlet of Takatz Lake. In November 2010 the USGS re-established a gage at the mouth of Takatz Creek and is currently collecting streamflow data at the time of this 2013-2014 Appraisal report. At the time of the 1968 study program there was no direct USGS measurement of daily outflows at the outlet of Takatz Lake. The 1968 study hydrology work estimated the Takatz Lake outflows for the 1946 to 1964 period (a 19 year record). This record was developed from the 1952 to 1964 Takatz Creek (near tidewater) gage record, using an areal adjustment for flows at the mouth of Takatz Creek vs. flows at the lake outlet. This area-adjusted record was supplemented by estimated flows based on correlations between Takatz Creek and Sawmill Creek (on the west side of Baranof Island near Sitka) gage stream records for the years from 1946 to 1951. The estimating methodology was well documented in the 1968 study report. As a result, the 2013 study team was able to extend the Takatz Lake estimated outflow record to include a longer estimated record for the period 1951 to 1968, using the four years of flow data for Gage 15100000 from 1965 through 1968. In October 2008 the USGS installed a stream gage at the outlet of Takatz Lake (USGS gage No. 15099900 – Takatz Creek at Takatz Lake Outlet near Baranof, AK). Consequently just less than five years of direct streamflow data were available for the Takatz Lake outlet at the time of our hydrology analysis. This data was provisional at the time of our study effort, in part because the flow rating table for the gage site has not been fully developed by USGS staff. For this 2013 study effort, the provisional data for measured flows at the outlet of Takatz Lake proved very useful on two fronts. First, this directly measured flow data allowed us to confirm the reasonableness of APA’s flow correlations between the lake outlet and the gage at tidewater. And, second, these 5 years of data allowed us to extend the overall flow data set from the 19 year estimated record used in 1968 to a more robust 28 year record that includes a 5 year (18%) component of directly measured flows.


13

In October 2013 the City contracted for a stream gage to be installed on the “north tributary” in Reach 2 of Takatz Creek to record accretion flow from the north tributary into the proposed bypassed reach of Takatz Creek. Flow records from this gage are being collected to aid in fisheries, habitat and instream-flow studies related to the Takatz Project. These gage records were not used in the hydrology or power studies related to the Takatz generating facilities. Detailed summaries of the estimated and directly measured flow record from the two USGS stream gages follow below. 3.2 Hydrology Analyses in the 1968 Study Appendix A of the 1968 study report (pages A-1 to A-33) includes a discussion of the climate, typical hydrology and streamflow data available at the time of that study. The hydrological analysis included a comparison of precipitation and temperature records between the east and west sides of Baranof Island to help characterize the likely basin yield at Takatz Lake. The analysis compared the limited Takatz Creek streamflow record to other waterways on Baranof Island that had longer gage records, notably Sawmill Creek near Sitka and the Baranof River. The evaluation also compared the average runoff of 22 Southeast Alaska streams and rivers, based on the average elevation of each stream’s drainage basin (Figure 3-1). That analysis established a unit runoff for Takatz Lake of 12,300 acre-ft of water per square mile per year, which equates to an average annual runoff at the lake outlet of 17 cfs per sq mile. The 1968 study compiled available monthly flow distribution data for the following streams: Takatz Creek; Baranof River; Sawmill Creek; Green Lake outlet; Maksoutof River, Deer Lake outlet; and Coal Creek. This data was used to develop an areal correlation between the expected Takatz Lake outflows vs. the recorded flows of Takatz Creek at gage no. 15100000. That correlation determined that the estimated annual Takatz Lake outflow is 65.3% of the measured outflow at the Takatz Creek gage (i.e., the higher elevations of the Takatz Creek basin above the lake, which comprise 60.6% of the basin area, were estimated to account for 65.3% of the total basin flow). Note also that the 1968 analysis considered the basin area above Takatz Lake to be only 10.6 square miles. This reduction from 10.8 sq miles is due to the saddle dam proposed in the 1968 Study. The saddle dam actually cuts off 0.2 square miles of the natural drainage basin feeding the lake. A seasonal adjustment factor was developed in the 1968 Study, which accounted for the high elevation of the Takatz Lake basin. Runoff from these high elevations is characterized by very low flows in the November to April months, when the basin is largely frozen. Runoff from the basin is concentrated in the July to October period when warmer conditions, snowmelt, and rain produce most of the basin’s annual flow. That seasonal variation in flows was estimated as shown in Table 3-1.

Table 3-1 Seasonal Runoff Distribution for Takatz Lake (APA 1968 Study) Runoff, percent of annual flow Season Nov - Apr May - June July - Oct Percent of annual flow 15.0 20.7 64.3


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The 1968 hydrology development used the areal and seasonal runoff correlations described above to estimate the monthly flows at the Takatz Lake outlet, for the years from 1952 to 1964. Annual flows at the Takatz Creek gage site, from 1946 to 1951 were estimated using a streamflow correlation between Sawmill Creek and Takatz Creek flows. The correlation equation and its error from actual gage records are shown in Figure 3-2. The estimated annual basin flows derived from this equation were then distributed on a monthly basis using the correlation equations shown in Table 3-2. The resulting estimated 1946 to 1951 Takatz Creek monthly flows were then further adjusted for the areal and seasonal correlations to estimate the 1946 to 1951 monthly inflows to Takatz Lake. The combined data set, of monthly Takatz Lake inflows for the 1946 to 1964 period is shown in Table 3-3.


15

Figure 3-1 Takatz Lake Estimated Runoff per sq. mile, from 1968 Study


16

Figure 3-2 Flow Correlation between Takatz Creek and Sawmill Creek, from 1968 Study


17

Table 3-2 Monthly Flow Correlation: Takatz Creek to Sawmill Creek, from 1968 Study


18

Table 3-3 Computed Inflow to Takatz Lake 1946 to 1964 Water Years - 1968 Study

3.3 Extension of 1968 Estimated Hydrology Record For purposes of this 2013 study, it was determined that the 1968 methodology was adequate to further extend the estimated hydrology record. Essentially, the 1968 methodology was replicated to verify it, then a the series of calculations developed in 1968 were used to extend the estimated record from 1946-1964 by four years to include 1946-1968. Note that while the 1968 study work focused on water years, hydrology in this 2013 study report used calendar year records. This shift from a water year basis to a calendar year was made to be consistent with Sitka’s current hydro operations model. 3.3.1 Source Data The primary data sources used to extend the estimated portion of the Takatz Lake streamflow data were the USGS gages 15088000 Sawmill Creek Near Sitka, AK and 15100000 Takatz Creek Near Baranof, AK. 3.3.2 Methodology for Extension of Estimated Record As described in section 3.2, the 1968 report outlines the methodology for synthesizing an inflow record for Takatz Lake for water years 1946 through 1964. At the time of that study, the Takatz


19

Creek data beyond 1964 was still provisional. For the current study the team utilized the same methodology to extend the period of record to include 1965-1968 (incorporating the full record of the Takatz Creek gage data). The steps followed are summarized below: 1. Annual and seasonal correlations between Sawmill Creek flows and Takatz Creek flows are

used to extend the Takatz Creek period of record. After this step the Takatz Creek flow record extends from 1946-1968. The 1946-1951 data is the synthesized record from Sawmill Creek (see Table 3-4).

2. Seasonal/Areal flow ratios were used to synthesize Takatz Lake inflows from the Takatz Creek gaged flows. Reflecting the higher elevation and reduction of total basin size, this step transforms the monthly Takatz Creek flows developed in Step 1 into Takatz Lake monthly inflows. (see Table 3-5). Note that Table 3-5 presents calculated flows for a Takatz Lake drainage area of 10.6 sq miles. This is the effective drainage area if a saddle dam is constructed as part of the project. The saddle dam would cut off 0.2 sq miles of drainage area, reducing the net inflow by a bit less than two percent.

3. For development options that do not include the saddle dam the areal inflow ratio was increased

by 1.89%, effectivly increasing all estimated inflows to Takatz Lake by 1.89%. This adjustment reflects the difference between the lake’s gross drainage area (10.8 square miles) vs. the net area with the saddle dam (10.6 sq miles). The resulting estimated Takatz Lake inflows with no saddle dam are shown in Table 3-6.

It should also be noted that while the current hydrology analysis followed the same methodology as the 1968 study, some discrepancies were found. The Takatz Creek USGS gage data for 1951 to 1964 utilized in the 1968 report is different than the currently published USGS record for the Takatz Creek gage for the same time period, 1951 to 1964. The differences appear to be clustered around months with days of relatively high flows (greater than 800 cfs, or so). It is likely that at some point after the 1968 study was completed the Takatz Creek gage rating curve was revised by the USGS, with the majority of the adjustment occurring at the higher flow readings. The net effect of the changes made by the USGS aftter the APA study was to reduce the USGS-documented average flow at the Takatz Creek gage from 269.9 cfs to 255.1 cfs for the period from 1951 to 1964. This is a 5.5 percent reduction in average yield for the Takatz Creek basin during that 14 year period. The average flow reported by USGS for the 1965 to 1969 water years was 252.8 cfs. Combining this data for the last four years of the gage record with the revised USGS 1951 to 1964 data results in an average flow at the Takatz Creek gage of 254.5 cfs for the full 19 year estimated record. Using the correlation functions developed in the 1968 study work and the updated USGS 1951 to 1968 flow records for Takatz Creek gives an estimated average Takatz Lake inflow of 169.2 cfs (for a 10.6 sq mile drainage area). This is 5 percent less than the 177.9 cfs average inflow documented in the 1968 study.


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Table 3-4 Takatz Creek Estimated Monthly Average Flows

Takatz Creek Monthly Average Flows (cfs) ‐ 17.5 mi2 Drainage Area

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Ann Avg

Tak

atz

Cre

ek

Fro

m

Saw

mill

1946 50.7 30.4 36.4 45.5 307.3 529.4 478.0 390.9 397.3 476.2 314.4 46.5 259.8

1947 74.4 50.0 153.2 127.5 340.0 402.8 429.7 413.9 767.7 379.3 253.5 94.1 291.4

1948 148.0 39.1 30.1 33.8 333.6 520.1 588.8 437.4 710.8 395.9 332.7 52.3 303.0

1949 102.0 41.9 59.6 73.3 278.9 603.7 552.9 446.6 428.1 548.2 224.0 55.1 286.0

1950 27.9 27.1 26.0 37.5 168.7 524.3 577.6 387.3 350.5 239.5 67.5 26.8 206.1

1951 35.2 21.8 25.6 66.3 234.6 478.9 449.9 309.3 324.4 266.2 226.0 53.6 208.4

Tak

atz

Cre

ek f

rom

US

GS

Da

ta

1952 20.0 20.0 17.0 80.1 209.8 395.0 586.9 420.0 482.0 463.1 283.8 115.0 259.1

1953 56.5 58.6 68.8 90.4 372.5 547.3 523.3 441.5 456.6 519.3 226.3 128.8 292.3

1954 49.7 125.5 35.7 33.5 237.7 502.8 427.8 357.2 364.6 284.3 401.0 205.4 252.3

1955 62.8 47.3 39.1 54.1 144.0 370.9 544.0 466.1 426.6 282.3 100.4 36.9 215.7

1956 22.8 24.0 25.0 63.9 274.8 466.8 541.6 541.2 299.3 251.5 222.6 197.7 245.9

1957 66.2 40.3 33.4 65.6 300.8 512.0 447.6 363.5 348.3 233.9 302.7 73.1 233.0

1958 130.3 45.4 50.0 118.2 318.5 523.3 378.6 385.3 268.5 454.3 205.5 110.7 250.4

1959 47.4 44.9 62.6 77.4 277.3 607.7 580.3 438.4 294.9 269.3 186.8 108.3 250.8

1960 49.5 64.4 47.8 95.2 371.8 515.7 590.1 382.5 409.0 521.0 202.3 195.8 288.7

1961 85.0 72.1 86.7 106.9 286.2 585.9 492.1 467.0 355.4 411.6 121.2 45.2 260.8

1962 74.9 44.5 37.3 120.1 155.7 404.9 455.3 459.3 448.7 442.0 295.3 280.2 269.5

1963 175.9 195.9 70.0 88.4 242.2 362.0 352.4 281.1 779.5 673.8 184.3 213.8 301.9

1964 102.5 86.7 49.4 90.1 192.1 627.6 606.5 493.5 320.8 453.3 194.4 149.7 281.8

1965 128.8 50.0 59.1 85.6 144.2 412.7 489.5 334.9 278.5 587.8 116.5 80.6 232.3

1966 22.9 31.2 58.7 86.8 245.5 482.5 507.8 412.3 548.0 351.9 136.8 47.5 245.3

1967 53.5 45.6 22.5 37.0 250.4 520.1 468.5 441.0 685.9 309.5 280.3 63.3 265.3

1968 38.3 87.7 142.0 73.7 303.5 542.7 420.7 364.5 580.4 284.5 188.2 54.9 257.2

Average 70.7 56.3 53.7 76.1 260.4 497.4 499.6 410.2 448.9 395.6 220.3 105.9 259.0

Maximum 175.9 195.9 153.2 127.5 372.5 627.6 606.5 541.2 779.5 673.8 401.0 280.2 303.0

Minimum 20.0 20.0 17.0 33.5 144.0 362.0 352.4 281.1 268.5 233.9 67.5 26.8 206.1

Median 56.5 45.4 47.8 77.4 274.8 515.7 492.1 413.9 409.0 395.9 222.6 80.6 259.1


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Table 3-5 Takatz Lake Estimated Monthly Average Inflows (with Saddle Dam)

Takatz Lake Monthly Average Flows (cfs) ‐ with Saddle Dam 10.6 sq mi


Tak

atz

Lak

e F

rom

S

awm

ill

1946 25.2 15.1 18.1 22.6 178.9 308.1 351.3 287.3 292.0 350.0 156.3 23.1 168.9

1947 37.0 24.8 76.1 63.4 197.9 234.4 315.8 304.2 564.3 278.8 126.0 46.8 188.5

1948 73.5 19.4 14.9 16.8 194.2 302.7 432.7 321.5 522.5 291.0 165.4 26.0 197.9

1949 50.7 20.8 29.6 36.4 162.3 351.4 406.4 328.3 314.7 402.9 111.3 27.4 187.0

1950 13.9 13.5 12.9 18.6 98.2 305.1 424.6 284.7 257.6 176.0 33.5 13.3 137.6

1951 17.5 10.8 12.7 33.0 136.5 278.7 330.7 227.3 238.4 195.7 112.3 26.7 134.8

Tak

atz

Lak

e –

esti

mat

ed f

rom

US

GS

Dat

a at

mo

uth

of

Tak

atz

Cre

ek

1952 9.9 9.9 8.4 39.8 122.1 229.9 431.4 308.7 354.2 340.4 141.1 57.1 171.0

1953 28.1 29.1 34.2 44.9 216.8 318.5 384.6 324.5 335.6 381.7 112.5 64.0 189.2

1954 24.7 62.4 17.7 16.6 138.3 292.6 314.4 262.6 268.0 208.9 199.3 102.1 158.8

1955 31.2 23.5 19.4 26.9 83.8 215.9 399.9 342.6 313.5 207.5 49.9 18.4 144.4

1956 11.3 11.9 12.4 31.7 159.9 271.7 398.1 397.8 220.0 184.9 110.6 98.3 158.8

1957 32.9 20.0 16.6 32.6 175.1 298.0 329.0 267.1 256.0 171.9 150.4 36.3 148.5

1958 64.8 22.6 24.9 58.7 185.4 304.5 278.3 283.2 197.3 333.9 102.1 55.0 159.2

1959 23.5 22.3 31.1 38.5 161.4 353.7 426.5 322.2 216.7 197.9 92.8 53.8 161.5

1960 24.6 32.0 23.8 47.3 216.4 300.1 433.7 281.1 300.6 382.9 100.5 97.3 186.1

1961 42.2 35.8 43.1 53.1 166.6 341.0 361.7 343.2 261.2 302.5 60.2 22.5 169.4

1962 37.2 22.1 18.5 59.7 90.6 235.7 334.6 337.6 329.8 324.9 146.7 139.3 173.4

1963 87.4 97.4 34.8 43.9 141.0 210.7 259.0 206.6 573.0 495.2 91.6 106.3 195.3

1964 51.0 43.1 24.5 44.8 111.8 365.3 445.8 362.8 235.8 333.2 96.6 74.4 182.8

1965 64.0 24.9 29.4 42.5 83.9 240.2 359.7 246.2 204.7 432.0 57.9 40.1 152.6

1966 11.4 15.5 29.2 43.1 142.9 280.8 373.2 303.0 402.8 258.6 68.0 23.6 162.4

1967 26.6 22.7 11.2 18.4 145.7 302.7 344.4 324.2 504.1 227.5 139.3 31.4 174.5

1968 19.0 43.6 70.6 36.6 176.6 315.9 309.2 267.9 426.6 209.1 93.5 27.3 165.9

Average 35.1 28.0 26.7 37.8 151.6 289.5 367.2 301.5 330.0 290.8 109.5 52.6 168.2

Maximum 87.4 97.4 76.1 63.4 216.8 365.3 445.8 397.8 573.0 495.2 199.3 139.3 197.9

Minimum 9.9 9.9 8.4 16.6 83.8 210.7 259.0 206.6 197.3 171.9 33.5 13.3 134.8

Median 28.1 22.6 23.8 38.5 159.9 300.1 361.7 304.2 300.6 291.0 110.6 40.1 168.9


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Table 3-6 Takatz Lake Estimated Monthly Average Inflows (without Saddle Dam)

Takatz Lake Monthly Average Flows (cfs) ‐ No Saddle Dam 10.8 sq mi


Tak

atz

Lak

e F

rom

S

awm

ill

1946 25.7 15.4 18.4 23.0 182.2 313.8 357.7 292.6 297.4 356.4 159.1 23.5 172.0

1947 37.7 25.3 77.5 64.5 201.5 238.7 321.7 309.8 574.6 283.9 128.3 47.7 192.0

1948 74.9 19.8 15.2 17.1 197.7 308.2 440.7 327.4 532.1 296.4 168.4 26.5 201.5

1949 51.6 21.2 30.2 37.1 165.3 357.8 413.9 334.3 320.5 410.3 113.4 27.9 190.4

1950 14.1 13.7 13.2 19.0 100.0 310.7 432.4 289.9 262.3 179.3 34.1 13.6 140.1

1951 17.8 11.0 12.9 33.6 139.0 283.8 336.8 231.5 242.8 199.3 114.4 27.2 137.3

Tak

atz

Lak

e –

esti

mat

ed f

rom

US

GS

Dat

a at

mo

uth

of

Tak

atz

Cre

ek

1952 10.1 10.1 8.6 40.5 124.4 234.1 439.3 314.4 360.8 346.6 143.7 58.2 174.2

1953 28.6 29.7 34.8 45.7 220.8 324.4 391.7 330.5 341.8 388.7 114.6 65.2 192.6

1954 25.1 63.5 18.1 17.0 140.9 298.0 320.2 267.4 272.9 212.8 203.0 104.0 161.8

1955 31.8 23.9 19.8 27.4 85.3 219.9 407.2 348.9 319.3 211.3 50.8 18.7 147.0

1956 11.5 12.1 12.7 32.3 162.9 276.7 405.4 405.1 224.0 188.3 112.7 100.1 161.7

1957 33.5 20.4 16.9 33.2 178.3 303.4 335.0 272.0 260.7 175.1 153.2 37.0 151.2

1958 66.0 23.0 25.3 59.8 188.8 310.1 283.4 288.4 201.0 340.0 104.0 56.0 162.2

1959 24.0 22.7 31.7 39.2 164.3 360.2 434.4 328.2 220.7 201.6 94.5 54.8 164.5

1960 25.0 32.6 24.2 48.2 220.3 305.6 441.7 286.3 306.1 389.9 102.4 99.1 189.6

1961 43.0 36.5 43.9 54.1 169.6 347.3 368.4 349.5 266.0 308.1 61.3 22.9 172.6

1962 37.9 22.5 18.9 60.8 92.3 240.0 340.8 343.8 335.8 330.8 149.4 141.8 176.6

1963 89.0 99.1 35.4 44.7 143.6 214.6 263.8 210.4 583.5 504.3 93.3 108.2 198.9

1964 51.9 43.9 25.0 45.6 113.9 372.0 454.0 369.4 240.1 339.3 98.4 75.8 186.2

1965 65.2 25.3 29.9 43.3 85.5 244.6 366.4 250.7 208.5 440.0 58.9 40.8 155.4

1966 11.6 15.8 29.7 43.9 145.5 286.0 380.1 308.6 410.2 263.4 69.2 24.1 165.4

1967 27.1 23.1 11.4 18.7 148.4 308.2 350.7 330.1 513.4 231.7 141.9 32.0 177.7

1968 19.4 44.4 71.9 37.3 179.9 321.7 314.9 272.8 434.5 212.9 95.2 27.8 168.9

Average 35.8 28.5 27.2 38.5 154.4 294.8 373.9 307.0 336.0 296.1 111.5 53.6 171.3

Maximum 89.0 99.1 77.5 64.5 220.8 372.0 454.0 405.1 583.5 504.3 203.0 141.8 201.5

Minimum 10.1 10.1 8.6 17.0 85.3 214.6 263.8 210.4 201.0 175.1 34.1 13.6 137.3

Median 28.6 23.0 24.2 39.2 162.9 305.6 368.4 309.8 306.1 296.4 112.7 40.8 172.0


23

3.4 Streamflow Measurements at Takatz Lake Outlet, 2009 - 2013 Streamflow measurements from the outlet of Takatz Lake, USGS Gage No. 15099900, have been recorded since November 2008 through the time of this 2013 study effort. The gage record available from the USGS was provisional at the time of our study. However, the study team considered this data the best available, being a direct measurement of flows from the lake, not reliant on any correlations to other gages or stream basins. The recorded flow data included some gaps in daily record all of which were in calendar year 2013. To estimate the 26 days of missing flows the days immediately preceding and following the missing day were averaged. As the daily variability plays a small part in the operations of the proposed plant, this method was believed to be adequate for study purposes. At the time of the hydrology evaluation, a total of 59 months of data were available to the study team, from November 2008 through September 2013. To create a five-year, calendar-year record the team elected to use the actual USGS calendar year hydrology data for 2009 through 2012 for the first four years of inflow. The 2013 flow record is partially estimated and uses the following: a) actual monthly flows for January 2013 through September 2013; b) an estimated October 2013 flow, taken as the average October monthly flows in 2009 through 2012; and c) estimated November and December 2013 flows which are equal to the recorded November and December 2008 flows. The resulting monthly flow record is shown in Table 3-7. As this record is the first direct measurement of lake outflows our study team compared this record to the APA’s historical estimated record to define the net variation and to gain insight into the likely accuracy of the APA’s 1968 estimating methods. This comparison shows that the 160.7 cfs average lake outflow from 2009 through 2013 is 10.6 cfs (6.2%) less than the estimated 171.3 cfs for the 1946 to 1968 period.

Table 3-7 Takatz Lake Outflows 2009 – 2013, based on USGS Gage 15099900 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Ann Avg

US

GS

Gag

e D

ata

2009 34.5 35.5 30.4 26.8 146.3 347.4 349.4 329.2 328.8 203.1 116.2 39.3 166.2

2010 61.6 67.9 70.4 118.1 218.8 328.8 309.9 271.1 222.6 240.6 145.1 30.6 174.3

2011 27.8 43.8 19.3 30.2 154.5 270.7 303.8 233.2 291.6 174.4 70.3 74.6 141.7

2012 34.8 30.6 26.2 56.8 161.1 325.3 347.5 316.4 301.8 139.6 73.6 32.6 154.5

2013 46.5 51.8 32.5 32.0 235.6 375.9 291.3 241.3 278.1 280.3 92.8 33.9 166.6

Average 41.0 45.9 35.8 52.8 183.3 329.6 320.4 278.2 284.6 207.6 99.6 42.2 160.7

Maximum 61.6 67.9 70.4 118.1 235.6 375.9 349.4 329.2 328.8 280.3 145.1 74.6 174.3

Minimum 27.8 30.6 19.3 26.8 146.3 270.7 291.3 233.2 222.6 139.6 70.3 30.6 141.7

Median 34.8 43.8 30.4 32.0 161.1 328.8 309.9 271.1 291.6 203.1 92.8 33.9 166.2

Note: A complete 2013 Calendar Year hydrology set was not available at the time of this 2013 study effort. The 2013 data shown in this table is actual data for January through September 2013. October 2013 data is the average of the four October months of 2009 through 2012. November and December 2013 are the actual monthly data from November and December 2008.


24

Also, a comparison of the monthly distribution of flows shows that the peak inflows during 2009 through 2013 are both smaller than peaks in the estimated record and the recent monthly peaks have shifted to earlier in the year. See Figure 3-4. In the APA estimated record, peak monthly inflows in 8 of the 23 years range from 400 to 550 cfs in September and October. The more recent 2009 – 2013 record has no monthly peak inflow above 370 cfs and the peak monthly flows during all five years occur in June or July of each year. These variations could be the result of inaccuracies in the APA’s seasonal flow distribution adjustments. Also, the variation could be the result of warmer spring and summer months in the more recent 2009 - 2013 record, causing an earlier basin thaw and earlier runoff. The variation could also be simply the result of the recent years’ having a short term trend of warmer spring and early summer than more long term conditions. Study staff believe that the five year duration of the recent flow record is not sufficiently long to draw conclusions about either the total basin flow yield or the distribution of flows within the year. We only note that the recent flow average is less than the historical estimate and that recently the basin runoff has occurred earlier in the year. The one strong conclusion that we make is that there is significant value in continuing stream gaging at both the lake outlet and at the mouth of Takatz Creek. If an additional 5 years of flow data were recorded at both gages, this would provide 10 years of actual flow records and 5 years of direct correlation between the lake outlet flows and the creek outlet. This data set would be sufficiently long to make adjustments in the APA estimating methodology for the 1952 to 1968 record. Also, if 5 years additional stream gage records are collected, the study team believes it would be appropriate to discard from the hydrologic record the 1946 to 1951 data, which was estimated from a cross-basin correlation to Sawmill Creek. This correlation from the east to west sides of Baranof Island is somewhat suspect due to the inherent variation in precipitation patterns between the east and west shores of the island. Also, as discussed in Section 9, the estimated flows from 1950 and 1951 represent the two driest years in the hydrologic record. These years therefore control the estimated firm energy output of the Takatz Project. It would be more appropriate to have the firm energy of the project be based on either direct measurements or the areal correlation between the two gages on Takatz Creek. 3.5 Water Right On July 24, 2014 the City of Sitka submitted an application for a water right to the Alaska Department of Natural Resources-Water for a hydropower development at Takatz Lake. That application was assigned the Land Administration System (LAS) number LAS-29821. The City’s application contains a request for sufficient water to meet the needs of the recommended development alternative as described in Section 11.

!(

!(

!(

!(

!(

!(

!(

FIGURE 3-3 TAKATZ CREEK DRAINAGE BASIN, FLOW GAUGE LOCATION MAP

LEGEND!( STREAM GAUGE LOCATIONS

!( REACH BREAK

REACH 1

REACH 2

REACH 3

TRIBUTARY

OFF-CHANNEL WATER

³0 500 1,000 1,500 2,000250Feet

SCALE

EASTTRIBUTARY

POND

REACH 1

LOWER WATERFALL(~25-30 FT)

REACH 2

LOWER BEAVER AREAUPPER BEAVER AREANORTH TRIBUTARY

CASCADE

UPPER WATERFALL BACKWATER

UPPER WATERFALL

REACH 3

LOWER TAKATZ LAKE

TAKATZ LAKE

TIDAL FLATAREA

PROPOSED POWERHOUSELOCATIONS

PROPOSED TUNNEL/LAKE TAP LOCATION

OXBOWAREA

LAKE OUTLET LEVEL/STREAM GAUGE (USGS, 2008)

STREAM GAUGE(CBS, 2013)

STREAM GAUGE (USGS, 2010)BELOW EAST TRIB.


26

Figure 3-4 Comparison of 2009 - 2013 Gage Record to APA Estimated Hydrology

3.5 Combined Hydrologic Data Set A compiled 28-year hydrology data set for the Takatz Lake outflows is shown in Table 3-8. This table includes updated estimated flows from a 23-year period from 1946 to 1968, based on the APA estimating methodology, combined with four years of actual flow data from 2009 through 2012 and an estimated 2013 calendar year’s data. Note that this table is based on a 10.8 sq mile drainage area, without the saddle dam. The average basin yield in this 28 year record is 169.3 cfs, compared to the APA’s 18 year estimated record of 181.3 cfs (adjusted for the 10.8 sq mile drainage area). Thus the 2013 estimate of basin flows is 7% less than that estimated by the APA in 1968. The flow exceedance curve for the 10.8 square mile basin is shown in Figure 3-5. Table 3-9 presents the 28-year data set for the Takatz Lake outflow adjusted for a drainage area of 10.6 sq miles. This data is used for power operations studies of the APA original development plan that includes a saddle dam which cuts off 0.2 square miles of the basin drainage area.

APA


27

Figure 3-5 Takatz Lake Flow Exceedance Curve, 10.8 sq mi Drainage Area


28

Table 3-8 Takatz Lake Monthly Average Inflows (without Saddle Dam), 28-Year Record

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Ann Avg1946 25.7 15.4 18.4 23.0 182.2 313.8 357.7 292.6 297.4 356.4 159.1 23.5 172.0

1947 37.7 25.3 77.5 64.5 201.5 238.7 321.7 309.8 574.6 283.9 128.3 47.7 192.0

1948 74.9 19.8 15.2 17.1 197.7 308.2 440.7 327.4 532.1 296.4 168.4 26.5 201.5

1949 51.6 21.2 30.2 37.1 165.3 357.8 413.9 334.3 320.5 410.3 113.4 27.9 190.4

1950 14.1 13.7 13.2 19.0 100.0 310.7 432.4 289.9 262.3 179.3 34.1 13.6 140.1

1951 17.8 11.0 12.9 33.6 139.0 283.8 336.8 231.5 242.8 199.3 114.4 27.2 137.3

1952 10.1 10.1 8.6 40.5 124.4 234.1 439.3 314.4 360.8 346.6 143.7 58.2 174.2

1953 28.6 29.7 34.8 45.7 220.8 324.4 391.7 330.5 341.8 388.7 114.6 65.2 192.6

1954 25.1 63.5 18.1 17.0 140.9 298.0 320.2 267.4 272.9 212.8 203.0 104.0 161.8

1955 31.8 23.9 19.8 27.4 85.3 219.9 407.2 348.9 319.3 211.3 50.8 18.7 147.0

1956 11.5 12.1 12.7 32.3 162.9 276.7 405.4 405.1 224.0 188.3 112.7 100.1 161.7

1957 33.5 20.4 16.9 33.2 178.3 303.4 335.0 272.0 260.7 175.1 153.2 37.0 151.2

1958 66.0 23.0 25.3 59.8 188.8 310.1 283.4 288.4 201.0 340.0 104.0 56.0 162.2

1959 24.0 22.7 31.7 39.2 164.3 360.2 434.4 328.2 220.7 201.6 94.5 54.8 164.5

1960 25.0 32.6 24.2 48.2 220.3 305.6 441.7 286.3 306.1 389.9 102.4 99.1 189.6

1961 43.0 36.5 43.9 54.1 169.6 347.3 368.4 349.5 266.0 308.1 61.3 22.9 172.6

1962 37.9 22.5 18.9 60.8 92.3 240.0 340.8 343.8 335.8 330.8 149.4 141.8 176.6

1963 89.0 99.1 35.4 44.7 143.6 214.6 263.8 210.4 583.5 504.3 93.3 108.2 198.9

1964 51.9 43.9 25.0 45.6 113.9 372.0 454.0 369.4 240.1 339.3 98.4 75.8 186.2

1965 65.2 25.3 29.9 43.3 85.5 244.6 366.4 250.7 208.5 440.0 58.9 40.8 155.4

1966 11.6 15.8 29.7 43.9 145.5 286.0 380.1 308.6 410.2 263.4 69.2 24.1 165.4

1967 27.1 23.1 11.4 18.7 148.4 308.2 350.7 330.1 513.4 231.7 141.9 32.0 177.7

1968 19.4 44.4 71.9 37.3 179.9 321.7 314.9 272.8 434.5 212.9 95.2 27.8 168.9

2009 34.5 35.5 30.4 26.8 146.3 347.4 349.4 329.2 328.8 203.1 116.2 39.3 166.2

2010 61.6 67.9 70.4 118.1 218.8 328.8 309.9 271.1 222.6 240.6 145.1 30.6 174.3

2011 27.8 43.8 19.3 30.2 154.5 270.7 303.8 233.2 291.6 174.4 70.3 74.6 141.7

2012 34.8 30.6 26.2 56.8 161.1 325.3 347.5 316.4 301.8 139.6 73.6 32.6 154.5

2013 46.5 51.8 32.5 32.0 235.6 375.9 291.3 241.3 278.1 280.3 92.8 33.9 166.6

36.7 31.6 28.7 41.1 159.5 301.0 364.4 301.9 326.8 280.3 109.4 51.6 169.4

89.0 99.1 77.5 118.1 235.6 375.9 454.0 405.1 583.5 504.3 203.0 141.8 201.5

10.1 10.1 8.6 17.0 85.3 214.6 263.8 210.4 201.0 139.6 34.1 13.6 137.3

32.7 24.6 25.1 38.2 162.0 308.2 354.2 309.2 299.6 271.9 108.3 38.1 167.8

Note: A complete 2013 Calendar Year hydrology set was not available at the time of this 2013 study effort. The 2013 data shown in this table is actual data for

January through September 2013. Octover 2013 data is the aveage of the four October months of 2009 through 2012. November and December 2013 are the actual

monthly data from November and December 2008.

Minimum

Median

Takatz Lake Monthly Average Flows (cfs) ‐ No Saddle Dam 10.8 mi2

Tak

atz

Lak

e F

rom

Saw

mil

lT

akat

z L

ake

fro

m U

SG

S D

ata

US

GS

Gag

e D

ata

Average

Maximum


29

Table 3-9 Takatz Lake Monthly Average Inflows (with Saddle Dam), 28-Year Record

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Ann Avg1946 25.2 15.1 18.1 22.6 178.9 308.1 351.3 287.3 292.0 350.0 156.3 23.1 172.0

1947 37.0 24.8 76.1 63.4 197.9 234.4 315.8 304.2 564.3 278.8 126.0 46.8 192.0

1948 73.5 19.4 14.9 16.8 194.2 302.7 432.7 321.5 522.5 291.0 165.4 26.0 201.5

1949 50.7 20.8 29.6 36.4 162.3 351.4 406.4 328.3 314.7 402.9 111.3 27.4 190.4

1950 13.9 13.5 12.9 18.6 98.2 305.1 424.6 284.7 257.6 176.0 33.5 13.3 140.1

1951 17.5 10.8 12.7 33.0 136.5 278.7 330.7 227.3 238.4 195.7 112.3 26.7 137.3

1952 9.9 9.9 8.4 39.8 122.1 229.9 431.4 308.7 354.2 340.4 141.1 57.1 174.2

1953 28.1 29.1 34.2 44.9 216.8 318.5 384.6 324.5 335.6 381.7 112.5 64.0 192.6

1954 24.7 62.4 17.7 16.6 138.3 292.6 314.4 262.6 268.0 208.9 199.3 102.1 161.8

1955 31.2 23.5 19.4 26.9 83.8 215.9 399.9 342.6 313.5 207.5 49.9 18.4 147.0

1956 11.3 11.9 12.4 31.7 159.9 271.7 398.1 397.8 220.0 184.9 110.6 98.3 161.7

1957 32.9 20.0 16.6 32.6 175.1 298.0 329.0 267.1 256.0 171.9 150.4 36.3 151.2

1958 64.8 22.6 24.9 58.7 185.4 304.5 278.3 283.2 197.3 333.9 102.1 55.0 162.2

1959 23.5 22.3 31.1 38.5 161.4 353.7 426.5 322.2 216.7 197.9 92.8 53.8 164.5

1960 24.6 32.0 23.8 47.3 216.4 300.1 433.7 281.1 300.6 382.9 100.5 97.3 189.6

1961 42.2 35.8 43.1 53.1 166.6 341.0 361.7 343.2 261.2 302.5 60.2 22.5 172.6

1962 37.2 22.1 18.5 59.7 90.6 235.7 334.6 337.6 329.8 324.9 146.7 139.3 176.6

1963 87.4 97.4 34.8 43.9 141.0 210.7 259.0 206.6 573.0 495.2 91.6 106.3 198.9

1964 51.0 43.1 24.5 44.8 111.8 365.3 445.8 362.8 235.8 333.2 96.6 74.4 186.2

1965 64.0 24.9 29.4 42.5 83.9 240.2 359.7 246.2 204.7 432.0 57.9 40.1 155.4

1966 11.4 15.5 29.2 43.1 142.9 280.8 373.2 303.0 402.8 258.6 68.0 23.6 165.4

1967 26.6 22.7 11.2 18.4 145.7 302.7 344.4 324.2 504.1 227.5 139.3 31.4 177.7

1968 19.0 43.6 70.6 36.6 176.6 315.9 309.2 267.9 426.6 209.1 93.5 27.3 168.9

2009 33.9 34.9 29.9 26.3 143.7 341.1 343.1 323.3 322.9 199.4 114.1 38.6 163.2

2010 60.5 66.6 69.1 116.0 214.9 322.9 304.3 266.2 218.6 236.3 142.5 30.0 171.2

2011 27.3 43.0 18.9 29.7 151.7 265.8 298.4 229.0 286.4 171.3 69.0 73.3 139.2

2012 34.2 30.1 25.8 55.8 158.2 319.5 341.3 310.6 296.3 137.1 72.3 32.0 151.7

2013 45.6 50.9 31.9 31.4 231.4 369.1 286.0 237.0 273.0 275.2 91.2 33.3 163.6

36.0 31.0 28.2 40.3 156.6 295.6 357.8 296.4 321.0 275.2 107.4 50.6 168.9

87.4 97.4 76.1 116.0 231.4 369.1 445.8 397.8 573.0 495.2 199.3 139.3 201.5

9.9 9.9 8.4 16.6 83.8 210.7 259.0 206.6 197.3 137.1 33.5 13.3 137.3

32.1 24.2 24.7 37.5 159.1 302.7 347.8 303.6 294.2 266.9 106.4 37.5 167.1

Takatz Lake Monthly Average Flows (cfs) ‐ With Saddle Dam 10.6 mi2

Tak

atz

Lak

e F

rom

Saw

mil

lT

akat

z L

ake

fro

m U

SG

S D

ata

US

GS

Gag

e D

ata

Average

Maximum

Minimum

Median