Santiago Hills II Planned Community And East Orange Planned Community Area 1 Runoff Management Plan Volume 2: Surface Water Quality Prepared for The Irvine Community Development Company Prepared by GeoSyntec Consultants Oakland, California Portland, Oregon May 02, 2005 Prepared by The Irvine Company for Consideration by the City of Orange Table of Contents 1 Introduction................................................................................................................. 1 2 Environmental Setting................................................................................................ 1 2.1 Physical Setting................................................................................................... 1 2.2 Study Area Vegetation, Soils and Land Uses ..................................................... 2 2.3 Receiving Waters and Natural Drainages........................................................... 3 2.3.1 Receiving Waters and Beneficial Uses........................................................4 2.3.2 Natural Drainages........................................................................................6 2.4 Existing Receiving Water Quality .................................................................... 11 2.4.1 Irvine Lake.................................................................................................12 2.4.2 Peters Canyon Reservoir............................................................................14 2.4.3 Santiago Creek...........................................................................................18 3 Regulatory Setting.................................................................................................... 20 3.1 Clean Water Act................................................................................................ 20 3.2 MS4 Permit ....................................................................................................... 21 3.2.1 Receiving Water Limitations .....................................................................21 3.2.2 Technology-based Standards.....................................................................22 3.2.3 Local Implementation Plan........................................................................24 3.3 NPDES Construction General Permit............................................................... 26 3.4 General Waste Discharge Requirements for Non-Stormwater Discharges Associated with Construction ............................................................................................. 27 3.5 Basin Plan......................................................................................................... 27 3.6 California Toxics Rule...................................................................................... 27 4 Pollutants of Concern, Hydrologic Conditions of Concern, and Significance Criteria28 4.1 List of Pollutants of Concern ............................................................................ 28 4.2 Other Pollutants................................................................................................ 30 4.3 Hydrologic Conditions of Concern................................................................... 32 4.4 Significance Criteria......................................................................................... 32 4.5 Thresholds for Significance .............................................................................. 33 5 Project Design Features ............................................................................................ 34 5.1 Site Design BMPs............................................................................................. 35 5.2 Source Control BMPs ....................................................................................... 36 5.2.1 Non-Structural Source Control BMPs .......................................................36 5.2.2 Structural Source Control BMPs ...............................................................39 5.3 Treatment Control BMPs.................................................................................. 40 5.3.1 Drainage 1..................................................................................................42 5.3.2 Drainage 2..................................................................................................42 5.3.3 Drainage 3..................................................................................................42 5.3.4 Drainage 4..................................................................................................43 5.3.5 Drainage 5..................................................................................................43 5.3.6 Drainage 6 and 7 ........................................................................................44 5.4 Hydrologic Impacts Control PDF ..................................................................... 46 6 Water Quality Modeling Approach .......................................................................... 47 i Prepared by The Irvine Company for Consideration by the City of Orange 6.1 Model Description............................................................................................ 47 6.2 Area Modeled....................................................................................................49 6.3 Pollutants Modeled........................................................................................... 50 6.4 Pollutants Addressed Without Modeling.......................................................... 51 7 Water Quality Impact Assessment............................................................................ 51 7.1 Impact Assessment for Modeled Pollutants of Concern................................... 52 7.1.1 Stormwater Runoff Volumes .....................................................................52 7.1.2 Total Suspended Solids..............................................................................55 7.1.3 Nutrients.....................................................................................................59 7.1.4 Copper, Lead, & Zinc ................................................................................66 7.1.5 Total Dissolved Solids ...............................................................................74 7.2 Impact Assessment for Pollutants and Basin Plan Criteria Addressed Without Modeling .......................................................................................................... 76 7.2.1 Turbidity ....................................................................................................76 7.2.2 Pathogens ...................................................................................................76 7.2.3 Hydrocarbons.............................................................................................79 7.2.4 Pesticides....................................................................................................80 7.2.5 Trash and Debris........................................................................................81 7.3 Summary........................................................................................................... 82 7.4 MS4 Permit Requirements for New Development as Defined in the DAMP .. 84 7.5 Dry Weather Impacts ........................................................................................ 88 7.5.1 Dry Weather Flow Quantity.......................................................................88 7.5.2 Dry Weather Flow Quality.........................................................................89 7.5.3 Summary....................................................................................................90 7.6 Construction-Related Impacts........................................................................... 91 7.7 Other Considerations........................................................................................ 92 7.7.1 Operation and Maintenance.......................................................................92 7.7.2 Monitoring .................................................................................................99 7.7.3 Vector Control.........................................................................................100 7.7.4 Pollutant Bioaccumulation.......................................................................100 7.7.5 Impacts to Irvine Lake as a Water Supply and Drinking Water Source..102 7.8 Hydrologic Impact Analysis........................................................................... 104 7.8.1 SHII Drainages (The South Tributary, the North Tributary, ETC-6 Drainage and ETC-7 Drainage)......................................................................................104 7.8.2 Black Willow Forest Lacustrine Area......................................................105 7.8.3 Overland Flow Area within Irvine Regional Park ...................................105 7.8.4 ETC-9 Drainage.......................................................................................105 7.8.5 Woody’s Tributary...................................................................................106 7.8.6 Santiago Creek Reach 1...........................................................................106 7.9 Cumulative Impact Analysis........................................................................... 106 7.9.1 Irvine Lake...............................................................................................107 7.9.2 Peters Canyon Reservoir..........................................................................108