This is a digital document from the collections of the Wyoming Water Resources Data System (WRDS) Library. For additional information about this document and the document conversion process, please contact WRDS at [email protected] and include the phrase “Digital Documents” in your subject heading. To view other documents please visit the WRDS Library online at: http://library.wrds.uwyo.edu Mailing Address: Water Resources Data System University of Wyoming, Dept 3943 1000 E University Avenue Laramie, WY 82071 Physical Address: Wyoming Hall, Room 249 University of Wyoming Laramie, WY 82071 Phone: (307) 766-6651 Fax: (307) 766-3785 Funding for WRDS and the creation of this electronic document was provided by the Wyoming Water Development Commission (http://wwdc.state.wy.us) OF WYOMING 849 ZntStreet, Sdte 201 &-ton, Wpmiy 82930 (307) 789-6735 TABLE OF CONTENTS 1.0 EXECUTIVE SUMMARY This Section is provided under separate cover. 2.0 INTRODUCTION 2.1 Afton Water Supply System Description 2.2 Project History 2.3 Authorization 2.4 Study Area Description and Population 2.5 Study Objectives 2.6 Previous Studies 2.7 Acknowledgments 3.0 WATER SUPPLY CONSIDERATIONS 3.1 Identification of Water Use 3.1.1 Service Area Population 3.1.2 Water Use 3.1.3 Comparative Usage and Water Conservation Measures 3.2 Existing Water Supply Source - Periodic Spring 3.2.1 Water Quality 3.2.2 Spring Recharge Area 3.2.3 Spring Classification 3.2.4 Available Spring Discharge 3.3 Periodic Spring Collection System 3.3.1 Collection Pipe Condition and Capacity 3.4 Water Rights Considerations 3.4.1 Existing Water Rights 3.4.2 Other Potential Senior Water Rights 3.4.3 Needed Water Rights Filings and Petitions 3.4.4 Available Water vs. Legal Supply Table of Contents - Page 1 3.5 Other Potential Water Supply Sources 3.5.1 Additional Canyon Springs 3.5.2 Direct Filtration Treatment Plant 3.5.3 Groundwater Well(s) 4.0 STORAGE CONSIDERATIONS AND CONVEYANCE 4.1 General 4.2 Periodic Spring Collection Tank 4.2.1 Collection Tank Capacity 4.2.2 Collection Tank Condition 4.3 System Storage 4.3.1 Existing 1 MG Tank and Feedline 4.3.2 Storage Capacity 4.3.3 Tank Site Location 4.3.4 Modifications Required for Continued Use of Existing Tank 4.4 Canyon Transmission Line 4.4.1 Description of Existing Line 4.4.2 Pressure Control Valving 4.4.3 Condition of Existing Line 4.4.3.1 Swift Creek Crossings 4.4.3.2 "Slide Lake" Considerations 4.4.4 Canyon Geology and Soils 4.4.4.1 Construction Considerations 4.4.4.2 Soil Corrosivity 4.4.5 Pipeline Capacity 4.4.5.1 Existing Capacity 4.4.5.2 Future Canyon Transmission Line Sizing 4.4.5.3 Future Lower Transmission Line Sizing 5.0 ALTERNATE EVALUATIONS 5.1 Primary Water Supply 5.2 Project Alternatives 5.2.1 Alternate No. 1 : Periodic Spring Supply - Immediate Needs 5.2.2 Alternate No. 2: Periodic Spring Supply - Long Term Needs 5.2.3 Alternate No. 3: Swift Creek Collection - Water Treatment 5.3 Estimated Alternative Project Costs 5.4 Operation and Maintenance 5.5 "Life Cycle" Cost Comparison Table of Contents - Page 2 6.0 HYDROELECTRIC FACILITY I 6.1 General 6.2 Facility Siting 6.3 Optimizing PipelineIHydroelectric Station 6.4 Conceptual Design 6.5 Operation Plan 6.6 Licensing and Power Sales Agreements 7.0 SUMMARY OF RECOMMENDATIONS AND CONCLUSIONS 7.1 General 7.2 Recommended Water Supply System Improvements 7.2. 1 Periodic Spring Renovation 7.2.2 Spring Collection Tank Renovations 7.2.3 Upper Canyon Transmission Line 7.2.4 Flow Control/Pressure Reduction Station 7.2.5 1 MG Canyon Storage Tank 7.2.6 Lower Canyon Transmission Line 7.2.7 Booster Pump Station 7.2.8 Supplemental/Back-up Well Supply 7.2.9 System Telemetry and Control 7.3 Recommended Hydro-electric Generation Facility 7.4 Project Economic Data 7.4.1 Recommended Project Budgets 7.4.2 Financing 7.4.3 User Rate ImpactJAbility to Pay 7.5 Project Permitting Requirements 7.5.1 U.S. Forest Service Special Use Permits 7.5.2 Wyoming DEQ Permit to Construct 7.5.3 U.S. Army Corps of Engineers 404 Permit 7.5.4 Right-of-way Acquisition 7.5.5 Archeological Clearance 7.5.6 Water Rights 7.5.7 FERC Permit 7.5.8 Power Sales Agreement Table of Contents - Page 3 Appendix A - Detailed Cost Estimates Appendix B - Water Quality Data Appendix C - Swift Creek Canyon Transmission Line Inspection Log Appendix D - Groundwater Investigation Report Appendix E - Afton Water Rights Documentation Table of Contents - Page 4 LIST OF TABLES Table 3.1 Afton Population History Table 3.2 Afton Water Usage (present) Table 3.3 Water Usage Comparisons Table 3.4 Afton Water Rights Summary Table 3.5 Swift Creek Drainage - Afton Legal Yield vs. Month Table 4.1 Criteria for Evaluating Corrosion Potential in Soils Table 4.2 Pipe Size Comparisons Table 4.3 Lower Transmission Line - Residual Fire Flow Pressures Table 5.1 Alternative Water Supply Project Cost Estimates Table 5.2 Economics Comparisons of Project Alternatives Table 6.1 Summary of Hydroelectric Performance Based on Different Pipeline Sizes Table 6.2 Summary of Additional Hydroelectric Project Costs Table 7.1 Recommended Project Budget - Water Supply System Improvements Table 7.2 Recommended Project Budget - Hydro-Power Facility Table 7.3 Recommended Project User Rate Impacts Table of Contents - Page 5 LIST OF FIGURES Figure 2.1 Project Location Map Figure 2.2 Project Vicinity Map Figure 2.3 Existing Water Supply System Configuration Figure 3.1 Periodic Spring Siphon Model Figure 3.2 Periodic Spring Existing Collection System Figure 3.3 Interim Spring Improvement Detail - Collection Line Vent Modification Figure 3.4 Estimated Lowest Discharge Spring Cycle - Flow vs. Time Figure 3.5 Afton Water Rights Duration Curve Figure 4.1 Reservoir Siting Map Figure 6.1 Hydroelectric FacilityIOne MG Reservoir Site Plan Figure 6.2 Hydroelectric Building Figure 7.1 Overview of Recommended Project Figure 7.2 Periodic Spring Improvement Figure 7.3 97,000 Gallon Tank Rehabilitation Figure 7.4 Flow ControliPressure Reduction System Table of Contents - Page 6 SECTION 1.0 EXECUTIVE SUMMARY SECTION 1.0 EXECUTIVE SUMMARY - This Section is provided under separate cover - SECTION 2.0 INTRODUCTION PROJECT VICINITY MAP FIGURE 2.2 SECTION 2.0 INTRODUCTION 2.1 AFTON WATER SUPPLY SYSTEM DESCRIPTION The Town of Afton is a community of approximately 1400 residents making it the largest community in the Star Valley area. Afton's only water supply comes from the "Periodic Spring" located approximately five miles east up Swift Creek Canyon. From the spring, Afton's water is carried 870 feet (170 foot drop) through a 14-inch steel conduit where it is collected in a 97000 gallon concrete tank. From that point, the water is carried to the Town of Afton through approximately 5 miles of transmission pipeline. The upper 18,000 feet of the pipeline is 12-inch diameter thin-walled steel pipe. The remainder of the line is 14-inches in diameter. Line pressures are controlled by two Pressure reducing valve stations and a pressure relief ("blow-off")valve located at the east edge of town, 0.6 miles up the canyon, and 1.I miles up the canyon respectively. There is a one million gallon concrete storage tank located in Graveyard canyon near the southeast corner of the town. This tank is fed from the Swift Creek Canyon transmission line through a 10-inch PVC pipeline approximately 4000 feet in length. The present spring development, collection tank, and transmission line were constructed in the late 1950's. The blow-off valve was added approximately 5 years ago to minimize maintenance problems associated with excessive line pressures. The existing 1 MG storage tank was constructed in 1982 to address fire storage concerns in the community. A map of Afton's existing water supply system is included as Figure 2.3. 2.2 PROJECT HISTORY In 1984, an unusually heavy winter and wet spring resulted in a major mud slide in Swift Creek Canyon. This slide, located approximately 112 mile downstream of the Periodic Spring, formed a lake which covered the Town's water transmission line and their access road to the spring. In 1986, the Town contracted to have the creek channel restored and the lake drained at a cost of almost $8000.00. Within one month of this restoration work, a second mud slide was experienced in the same area. Since that time, several more slides have occured. The creation of "Slide Lake" has eliminated the ability of the Town to adequately maintain their pipeline and spring area above the slide. There is particular concern about the age and condition of the pipeline under the lake. Damage and/or deterioration of that line will likely result in the introduction of untreated creek water into the Town's water supply unless the problem is corrected. == I I --F- = -=- ASSOCIATESFORSGREN / P .A. In October of 1989, the Town submitted an application to the Wyoming Water Development Commission for the primary purpose of addressing the problems associated with Slide Lake. As part of that application, the Town requested that the Commission also examine several other concerns and operational deficiencies noted by system operators. This study is a result of that application and it's subsequent approval by the Commission. 2.3 AUTHORIZATION Authorization for the Afton Water Supply Level II Study was granted by contract between the Wyoming Water Development Commission and Forsgren Associates dated June of 1990.