“Ballona salt pan, pickleweed and ponded rainwater” Photograph by Jonathan Coffin (This page is left intentionally blank) Table of Contents Executive Summary ........................................................................................................................ 1 1 Introduction ............................................................................................................................. 3 1.1 Regulatory Background.................................................................................................... 3 1.2 Elements of a TMDL........................................................................................................ 4 2 Wetland Characteristics .......................................................................................................... 6 2.1 Environmental Setting ...................................................................................................... 6 2.2 Wetland Areas .................................................................................................................. 9 2.2.1 Area A ....................................................................................................................... 9 2.2.2 Area B ....................................................................................................................... 9 2.2.3 Area C ..................................................................................................................... 10 2.2.4 Constructed Freshwater Marsh ............................................................................... 10 2.2.5 Ballona Creek Channel ........................................................................................... 10 2.3 Physical Characteristics.................................................................................................. 10 2.3.1 Habitat, Flora, Fauna............................................................................................... 11 2.3.2 Wetland Hydrologic Processes ............................................................................... 11 2.4 Historical Wetland Condition......................................................................................... 12 2.4.1 Historical T-Sheet Maps ......................................................................................... 12 2.5 Historical Use ................................................................................................................. 15 2.6 Native American Cultural Resource .............................................................................. 17 2.7 Summary of Past Impacts ............................................................................................... 17 3 Problem Identification .......................................................................................................... 19 3.1 Water quality standards .................................................................................................. 20 3.1.1 Beneficial Uses ....................................................................................................... 20 3.1.2 Water Quality Objectives ........................................................................................ 22 3.1.3 Ecologically Functioning Wetland ......................................................................... 23 3.1.4 Impairment Listing.................................................................................................. 24 3.2 Overview of Stressors & Impairment Condition ........................................................... 25 3.2.1 Stressor Identification ............................................................................................. 26 3.3 Primary Cause of Impairment ........................................................................................ 37 3.4 Current Habitat Condition .............................................................................................. 38 3.5 Invasive Exotic Vegetation Condition ........................................................................... 43 3.6 Sediment Condition ........................................................................................................ 45 3.7 Hydrologic Condition ..................................................................................................... 46 4 Numeric Targets.................................................................................................................... 48 4.1 Selection of Water Quality Targets ................................................................................ 48 4.2 Basis for the Wetland Reference .................................................................................... 49 4.3 Basis for Numeric Targets.............................................................................................. 50 4.4 Tidal Elevation ............................................................................................................... 55 4.5 Exotic Vegetation ........................................................................................................... 57 Ballona Creek Wetlands TMDLs for Sediment and Invasive Exotic Vegetation i 5 Source Assessment................................................................................................................ 58 5.1 Point Sources .................................................................................................................. 58 5.1.1 Stormwater .............................................................................................................. 58 5.1.2 Caltrans ................................................................................................................... 59 5.1.3 Ballona Creek Watershed Sediment Loading ......................................................... 59 5.1.4 Playa Vista Freshwater Marsh ................................................................................ 62 5.1.5 Sanitary Storm Drains and Sewers ......................................................................... 63 5.2 Non-Point Sources.......................................................................................................... 63 5.2.1 Historic Sources ...................................................................................................... 63 5.2.2 Southern California Gas Company ......................................................................... 66 5.2.3 Fiji Ditch ................................................................................................................. 66 6 Linkage Analysis .................................................................................................................. 68 7 Total Maximum Daily Loads and Allocations...................................................................... 72 7.1 Wasteload Allocations for Sediment .............................................................................. 73 7.2 Load Allocations for Sediment ...................................................................................... 74 7.2.1 Alternative Load Allocations .................................................................................. 76 7.3 Load & Wasteload Allocations for Invasive Exotic Vegetation .................................... 77 7.4 Daily Load Expression of Total Maximum Daily Loads ............................................... 78 7.5 Seasonal Variation & Critical Condition ....................................................................... 78 7.6 Margin of Safety............................................................................................................. 79 7.7 Future Growth ................................................................................................................ 79 8 Implementation Recommendations ...................................................................................... 80 8.1 Ballona Wetland Restoration Project ............................................................................. 80 8.2 Cooperative Parties ........................................................................................................ 81 8.3 Sea Level Rise ................................................................................................................ 81 8.4 Monitoring ...................................................................................................................... 82 8.5 Future Study ................................................................................................................... 83 9 References ............................................................................................................................. 85 Appendix A ................................................................................................................................... 89 Ballona Creek Wetlands TMDLs for Sediment and Invasive Exotic Vegetation ii List of Tables Table 1. Summary of anthropogenic activities to the Ballona Creek Wetlands since 1900. Areas A, B, C and D refer to contemporary designations within the Ballona Creek Wetlands. ......................................................................................................................... 18 Table 2. Beneficial use designations for Ballona Creek Wetlands, Hydrologic Sub Area 405.13 (LARWQCB 1994). ........................................................................................... 22 Table 3. List of impairments identified for Ballona Creek Wetlands. ......................................... 26