Volume 1 FINAL July 2018 [This page left blank intentionally.] Seattle Public Utilities 2019 Water System Plan July 2018 VOLUME 1 [This page left blank intentionally.] SPU 2019 Water System Plan Acknowledgements The following have contributed to the preparation of this 2019 Water System Plan: Seattle Public Utilities Executive Directors Mami Hara, GM/CEO Ken Snipes, CAO Madeline Fong Goddard Rick Scott Seattle Public Utilities Contributing Technical Staff Joan Kersnar, Project Manager Black, Kevin Fleming, Paul Lackey, Brent Blackwell, Tony Flory, Bruce Madura, Jalaine Capron, Cheryl Ford, Jon Mantchev, Eugene Carpenter, Regina Garcia, Elizabeth McNerney, Jim Chen, Alex Gladstone, Judi Meyer, Betty Chinn, Alan Goodwin, Ingrid Minsch, Kathy Cross, Judith Gregg, Terri Naess, Ralph Curry, Kathy Hanna, Paul Narog, Jesse Davis, Darian Harper, Wylie Nilson, Jim DeLaTorre-Evans, Tracy Heubach, Bill ORourke, Kelly Edgerly, John Holtz, Cyndy Orr, Matthew Effertz, Kris Hubbert, Bob Pepin-Cato, Ellen Faulds, Paul Igoe, Paige Ryan, Andy Findlay, Cameron Kirby, Lynn Wells, Bill Flagor, Suzanne LaBarge, Amy Worcester, Ned Special appreciation is extended to members of the Seattle Water Supply Operating Board and the Water System Advisory Committee who provided input and comments on preliminary work products for this Water System Plan. Acknowledgements i SPU 2019 Water System Plan [This page left blank intentionally.] ii Acknowledgements SPU 2019 Water System Plan [This page left blank intentionally.] iv Certification SPU 2019 Water System Plan Table of Contents 2019 WATER SYSTEM PLAN ACKNOWLEDGEMENTS ........................................................................................ i CERTIFICATION ................................................................................................... iii TABLE OF CONTENTS ......................................................................................... v ABBREVIATIONS ................................................................................................ xiii PLAN SUMMARY ............................................................................................... S-1 Chapter 1 – Introduction 1.1 SPU’s Drinking Water Line of Business ............................................................. 1-1 1.1.1 History of Water Business ....................................................................... 1-1 1.1.2 System Description .................................................................................. 1-2 1.1.3 Business Areas ......................................................................................... 1-4 1.1.3.1 Major Watersheds Business Area ................................................ 1-4 1.1.3.2 Water Resources Business Area .................................................. 1-4 1.1.3.3 Water Quality and Treatment Business Area............................... 1-5 1.1.3.4 Transmission and Distribution Business Area ............................. 1-5 1.2 Guiding Policies ................................................................................................... 1-5 1.3 Customer Service Levels ..................................................................................... 1-7 1.4 Planning Requirements ........................................................................................ 1-8 1.4.1 WSP Requirements .................................................................................. 1-8 1.4.2 Consistency with Other Plans .................................................................. 1-9 1.4.2.1 Coordinated Water System Plans................................................. 1-9 1.4.2.2 Wholesale Customers’ Individual Water System Plans ............. 1-10 1.4.2.3 King County Comprehensive Plan............................................. 1-10 1.4.2.4 City of Seattle’s Comprehensive Plan ....................................... 1-11 1.4.2.5 Adjacent Purveyors .................................................................... 1-11 1.4.2.6 Purveyors Beyond the Boundaries of SPU’s Service Area ....... 1-11 1.4.2.7 Regional Wastewater and Reclaimed Water Plans .................... 1-12 1.4.2.8 Groundwater Area Management Plans ...................................... 1-12 1.4.2.9 Watershed Plans ......................................................................... 1-12 1.4.2.10 Salmon Recovery Plans ........................................................... 1-13 1.5 Plan Organization............................................................................................... 1-14 Chapter 2 – Water Resources 2.1 Accomplishments Since 2013 WSP..................................................................... 2-1 2.2 Service Level Performance .................................................................................. 2-2 2.3 Existing System and Practices ............................................................................. 2-3 2.3.1 Service Area Characteristics .................................................................... 2-3 Table of Contents v SPU 2019 Water System Plan 2.3.1.1 Changes in Demographics ........................................................... 2-3 2.3.1.2 Retail Customers .......................................................................... 2-6 2.3.1.3 Wholesale Customers................................................................... 2-6 2.3.2 Historical Water Consumption ................................................................ 2-8 2.3.3 Water Conservation Programs ................................................................. 2-9 2.3.3.1 Regional Conservation 2013-2018 ............................................ 2-11 2.3.3.2 Seattle-Only Conservation 2013-2018 ....................................... 2-12 2.3.3.3 Water Use Efficiency Goal and Program 2013-2018 ................ 2-13 2.3.4 Existing Water Supply ........................................................................... 2-14 2.3.4.1 Supply Sources........................................................................... 2-14 2.3.4.2 Water Rights .............................................................................. 2-16 2.3.4.3 Firm Yield and Supply Reliability ............................................. 2-16 2.3.5 Operations .............................................................................................. 2-17 2.3.5.1 Morse Lake Pump Plant ............................................................. 2-18 2.3.5.2 Scour Protection Levels ............................................................. 2-19 2.3.5.3 Water Shortage Contingency Plan ............................................. 2-19 2.3.6 Maintenance ........................................................................................... 2-20 2.4 Needs, Gaps, and Issues ..................................................................................... 2-20 2.4.1 Future Water Demand and Supply ......................................................... 2-20 2.4.1.1 Water Use Efficiency Goal and Program 2019-2028 ................ 2-21 2.4.1.2 Water Demand Forecast ............................................................. 2-22 2.4.1.3 Climate Change and Future Supply Outlook ............................ 2-27 2.4.1.4 Future Supply Opportunities ...................................................... 2-33 2.4.1.5 Wildfire Risk Management in SPU’s Watersheds ..................... 2-34 2.4.2 Infrastructure Needs and Improvements ................................................ 2-34 2.4.2.1 Landsburg Flood Passage Improvements .................................. 2-35 2.4.2.2 Lake Youngs Cascades Dam ..................................................... 2-35 2.4.2.3 Tolt Valve 15 ............................................................................. 2-35 2.4.2.4 Tolt Dam Warning System ........................................................ 2-36 2.4.2.5 Tolt Dam Lob Boom .................................................................. 2-36 2.4.3 South Fork Tolt FERC Relicensing Support ......................................... 2-36 2.5 Implementation/Action Plan .............................................................................. 2-36 Chapter 3 – Water Quality and Treatment 3.1 Accomplishments Since 2013 WSP..................................................................... 3-1 3.2 Service Level Performance .................................................................................. 3-2 3.3 Existing Facilities and Practices .......................................................................... 3-3 3.3.1 Regulatory Requirements and Compliance ............................................. 3-3 3.3.1.1 Total Coliform Rule ..................................................................... 3-3 3.3.1.2 Surface Water Treatment Rule..................................................... 3-5 3.3.1.3 Groundwater Rule ........................................................................ 3-6 3.3.1.4 Disinfection By-Products Rule .................................................... 3-6 3.3.1.5 Lead and Copper Rule ................................................................. 3-7 3.3.2 Other Water Quality Monitoring ............................................................. 3-8 3.3.3 Source Water Protection Programs ........................................................ 3-10 3.3.3.1 Watershed Protection ................................................................. 3-10 vi Table of Contents SPU 2019 Water System Plan 3.3.3.2 Wellhead Protection ..................................................................