A P R I L 2 0 0 7 C A L L E G U A S C R E E K W A T E R S H E D M A N A G E M E N T P L A N Calleguas Creek Watershed Boron, Chloride, TDS, and Sulfate TMDL Public Review Technical Report Prepared by LARRY W ALKER ASSOCIATES Submitted to LOS ANGELES REGIONAL W ATER QUALITY CONTROL BOARD AND THE UNITED STATES ENVIRONMENTAL PROTECTION AGENCY Table of Contents Table of Contents ........................................................................................................................... i List of Tables ................................................................................................................................. v List of Figures.............................................................................................................................. vii List of Acronyms........................................................................................................................viii Definitions...................................................................................................................................viii Section 1. Introduction .............................................................................................................. 3 1.1. Regulatory Background .................................................................................................... 5 1.1.1. Chloride Regulatory History...................................................................................... 6 1.2. Calleguas Creek TMDL Stakeholder Participation Process ............................................. 8 1.3. Elements of a TMDL ........................................................................................................ 9 Section 2. Problem Statement ................................................................................................. 10 2.1. Environmental Setting .................................................................................................... 10 2.1.1. Climate and Hydrology............................................................................................ 11 2.1.2. Land Use .................................................................................................................. 12 2.1.3. Urban Land Use ....................................................................................................... 12 2.1.4. Agricultural Land Use.............................................................................................. 13 2.1.5. Surface Waters......................................................................................................... 17 2.1.6. Simi and Las Posas Subwatershed........................................................................... 18 2.1.7. Conejo and Camarillo Subwatershed....................................................................... 19 2.1.8. Pleasant Valley Subwatershed ................................................................................. 20 2.1.9. Mugu Lagoon........................................................................................................... 20 2.1.10. Groundwater .......................................................................................................... 21 2.1.11. Anthropogenic Alterations..................................................................................... 21 2.1.12. Flow Diversion Project .......................................................................................... 22 2.1.13. Reach Designations................................................................................................ 22 2.2. Regulatory Background .................................................................................................. 24 2.2.1. Water Quality Objectives......................................................................................... 24 2.2.2. Antidegradation........................................................................................................ 25 2.2.3. Water Reclamation Policy ....................................................................................... 26 2.2.4. Beneficial Uses ........................................................................................................ 26 2.2.5. 303(d) Listings......................................................................................................... 34 Calleguas Creek Watershed i 6/4/2007 Salts TMDL First Stakeholder Draft Technical Report 2.2.6. Basis of 303(d) listings ............................................................................................ 35 2.3. Water Resources Problem Statement.............................................................................. 38 Section 3. Numeric Targets ..................................................................................................... 39 Section 4. Source Assessment.................................................................................................. 40 4.1. Conceptual Model........................................................................................................... 40 4.2. Source Analysis .............................................................................................................. 42 4.2.1. Sources of Salts to Watershed (Salt Inputs)............................................................. 42 4.2.2. Transportation of Salts to Surface Waters ............................................................... 53 4.3. Fate and Transport of Salts ............................................................................................. 57 Section 5. Linkage Analysis..................................................................................................... 59 5.1. Model Descriptions......................................................................................................... 59 5.1.1. Calleguas Creek Modeling System (CCMS) ........................................................... 59 5.1.2. Salts Balance Model ................................................................................................ 61 Section 6. TMDL and Allocations........................................................................................... 63 6.1. Allocation Approach....................................................................................................... 63 6.2. Critical Conditions and Loading Capacity...................................................................... 64 6.2.1. Loading Capacity Calculation.................................................................................. 65 6.3. Wasteload Allocations .................................................................................................... 66 6.3.2. Permitted Stormwater Dischargers .......................................................................... 72 6.3.3. Other NPDES Dischargers....................................................................................... 73 6.4. Load Allocations............................................................................................................. 74 6.4.2. Background Load Allocations ................................................................................. 75 6.5. Determining Compliance with Allocations .................................................................... 76 Section 7. Margin of Safety ..................................................................................................... 77 Section 8. Future Growth........................................................................................................ 78 8.1. Growth Management Efforts .......................................................................................... 79 8.2. Effects of Growth on Salts Loading................................................................................ 80 Section 9. Implementation Plan.............................................................................................. 81 9.1. Overarching Implementation Elements .......................................................................... 82 9.1.1. Regional Salinity Management Conveyance (RSMC) ............................................ 82 9.1.2. Description............................................................................................................... 82 9.1.3. Water Conservation ................................................................................................. 84 9.1.4. Water Softeners........................................................................................................ 85 Calleguas Creek Watershed ii 6/4/2007 Salts TMDL First Stakeholder Draft Technical Report 9.1.5. Best Management Practices for Irrigated Agriculture ............................................. 87 9.2. Implementation Elements-Southern Reaches of the CCW............................................. 88 9.3. Implementation Elements-Northern Reaches of the Calleguas Creek Watershed.......... 91 9.4. Summary of Implementation Elements .......................................................................... 94 9.4.1. Preparation of Environmental Documents............................................................... 97 9.4.2. Preliminary Design .................................................................................................. 97 9.4.3. Preparation of Plans & Specifications ..................................................................... 98 9.4.4. Permitting................................................................................................................. 98 9.4.5.