Raspberry Falls and Selma Estates Community Water Systems Study of Long Term Options January 2015 Table of Contents Executive Summary ....................................................................................................................................... 1 1.0 Background ............................................................................................................................................. 5 1.1 Study Area ..................................................................................................................................... 5 1.2 Water Sources and Previous Studies ............................................................................................ 5 1.2.1 Water Supply Sources ........................................................................................................... 5 1.2.2 Previous Studies .................................................................................................................... 9 1.3 General Regulatory Requirements .............................................................................................. 11 1.3.1 Sampling and Treatment ..................................................................................................... 11 1.3.2 Annual Withdrawal Reporting ............................................................................................ 12 1.4 Purpose of the Study of Long‐Term Water Supply Options ........................................................ 12 2.0 Water Demands and Supply ................................................................................................................. 15 2.1 Water Connections, Flow Rates, and Total Demand .................................................................. 15 2.2 Comparison of Water Supply Needs and Availability ................................................................. 16 3.0 Water Treatment, Storage and Distribution ......................................................................................... 19 3.1 Membrane Filtration ................................................................................................................... 19 3.1.1 Membrane Filtration Overview ........................................................................................... 19 3.1.2 Raspberry Falls / Selma Estates Combined Membrane Facility Concepts .......................... 19 3.1.3 Membrane Cleaning ............................................................................................................ 21 3.1.4 Waste Flows ........................................................................................................................ 23 3.1.5 Treatment Chemical Requirements .................................................................................... 26 3.2 Granular Activated Carbon (GAC) ............................................................................................... 29 3.2.1 GAC Contactor Configuration.............................................................................................. 29 3.2.2 GAC Contactor Size ............................................................................................................. 29 3.3 Finished Water Storage ............................................................................................................... 30 3.4 Irrigation Storage ........................................................................................................................ 33 3.4 Water Distribution ...................................................................................................................... 34 3.4.1 Hydraulic Modeling and Design Data .................................................................................. 34 3.4.2 Treated Water Distribution ................................................................................................. 35 3.4.3 Irrigation Water Distribution .............................................................................................. 39 4.0 Summary of Treatment and Distribution System Concepts ........................................................... 41 i 4.1 Supply and Treatment Option No. 1: Combined Potable Water Treatment with Separate Irrigation.................................................................................................................................................. 41 4.2 Supply and Treatment Option No. 2: Combined Mixed Use Water Treatment ......................... 42 4.3 Preliminary Cost Estimates ......................................................................................................... 43 5.0 Triple‐Bottom Line Sustainability Analysis – Financial, Social and Environmental ............................... 45 5.1 Introduction ...................................................................................................................................... 45 5.2 Criteria, Scoring and Weighting ........................................................................................................ 45 5.3 Evaluation using Economic Criteria ................................................................................................... 46 5.4 Evaluation using Environmental Criteria ........................................................................................... 47 5.4.1 Impact on Carbon Emissions ...................................................................................................... 47 5.4.2 Impact on Aquifer Sustainability ................................................................................................ 48 5.5 Evaluation using Social Criteria ......................................................................................................... 49 5.5.1 Public Health .............................................................................................................................. 49 5.5.2 Quality of Life ............................................................................................................................. 50 5.6 Summary of Triple Bottom Line Analysis of the Water Supply and Treatment Options .................. 50 5.7 Treatment Option Recommendation ................................................................................................ 51 List of Tables Table ES.1: Comparison of Selma Estates Well Capacity to Potable Water Needs .................................. p. 2 Table ES.2: Summary of Criteria Scoring for the Two Water Supply and Treatment Options ................. p. 4 Table 1.1: Raspberry Falls Community System: Aquifer Characteristics and Well Construction Records p. 6 Table 1.2: Summary of Raw Water Quality Parameters for Raspberry Falls ............................................ p. 7 Table 1.3: Aquifer Characteristics and Well Construction Records for Selma Estates ............................. p. 8 Table 1.4: Summary of Raw Water Quality Parameters for Selma Estates .............................................. p. 9 Table 2.1: Supply and Treatment Option 1 ‐ Potable Water Demands for Raspberry Falls and Selma Estates ................................................................................................................................... p. 15 Table 2.2: Supply and Treatment Option 1 ‐ Irrigation Demands for Raspberry Falls and Selma Estates .............................................................................................................................................. p. 16 Table 2.3: Supply and Treatment Option 2 ‐ Mixed Use Water Demands for Raspberry Falls and Selma Estates ................................................................................................................................... p. 16 Table 2.4: Comparison of Selma Estates Well Capacity to Potable Water Needs .................................. p. 16 Table 3.1: Membrane Sizing Parameters ................................................................................................ p. 20 Table 3.2: Typical Membrane Cleaning Chemicals ................................................................................. p. 22 ii Table 3.3: Treatment Option 1 Waste Flow Volumes and Rates ............................................................ p. 24 Table 3.4: Treatment Option 2 Waste Flow Volumes and Rates ............................................................ p. 25 Table 3.5: Membrane Cleaning Processes Frequencies and Associated Chemical Constituents ........... p. 26 Table 3.6: Maximum Waste Stream Chemical Loads – Citric Acid ......................................................... p. 27 Table 3.7: Maximum Waste Stream Chemical Loads – Chlorine ............................................................ p. 27 Table 3.8: Maximum Waste Stream Chemical Loads – Caustic .............................................................. p. 28 Table 3.9: Preliminary GAC Design Summary ......................................................................................... p. 30 Table 3.10: Supply and Treatment Option No. 1 Potable Water Storage Tank Requirements .............. p. 32 Table 3.11: Supply and Treatment Option No. 2 Potable Water Storage Tank Requirements .............. p. 33 Table 3.12: Supply and Treatment Option No. 1 Non‐Potable Water Storage Tank Requirements ...... p. 33 Table 3.13: Supply and Treatment Option 1 Total Potable Water Demands and System Design Criteria .............................................................................................................................................