Lower Payette River Subbasin Assessment and Total Maximum Daily Load December 1999 Prepared For State of Idaho by Idaho Division of Environmental Quality, Boise Regional Office 1445 North Orchard Boise, Idaho 83706 Principle Author: Michael J. Ingham Table of Contents List of Tables ................................................................................................................................... 1 List of Figures.................................................................................................................................. 1 1.0. Executive Summary.................................................................................................................. 2 1.1. Addressing Waterbody verses Hydrological Unit Area .................................................... 4 1.2. Public Involvement............................................................................................................. 4 1.3. Acknowledgment................................................................................................................ 5 2.0. Watershed/Water Quality Assessment...................................................................................... 7 2.1. Watershed Description ....................................................................................................... 7 2.1.1. Hydrology............................................................................................................... 12 2.1.2. Climate.................................................................................................................... 15 2.1.3. Geology................................................................................................................... 15 2.1.4. Fisheries.................................................................................................................. 19 2.1.5. Current Land Use.................................................................................................... 20 2.1.6. Land Ownership ..................................................................................................... 22 2.1.7. Historic Presence of Man........................................................................................ 25 2.1.8. Economic and Social Base...................................................................................... 25 2.2. Beneficial Use Designation History ................................................................................. 26 2.2.1 Current Beneficial Use Status.................................................................................. 26 2.3. Designated Beneficial Uses Rationale/Justification ......................................................... 27 2.3.1. Agricultural Water Supply...................................................................................... 27 2.3.2. Domestic Water Supply .......................................................................................... 27 2.3.3. Industrial Water Supply.......................................................................................... 28 2.3.4. Wildlife Habitat ...................................................................................................... 28 2.3.5. Aesthetics................................................................................................................ 28 2.3.6. Cold Water Biota .................................................................................................... 28 2.3.7. Salmonid Spawning ................................................................................................ 28 2.3.8. Recreational Use ..................................................................................................... 29 2.4. Water Quality Monitoring History................................................................................... 29 2.4.1. In-River Monitoring ............................................................................................... 29 2.4.2. Point Source Monitoring Requirements.................................................................. 30 2.4.3. Tributaries-Irrigation Return Drain Monitoring. ................................................... 30 2.5. Data Gaps ........................................................................................................................ 31 2.5.1. Urban-Suburban Areas ........................................................................................... 31 2.5.2. Waste Water Treatment Plants............................................................................... 31 2.5.3. Rural Areas ............................................................................................................. 32 2.5.4. In-River Biological Indicators (Bio-Monitoring) ................................................... 32 2.5.5. Ground Water Contribution.................................................................................... 32 2.6. Pollutant(s) of Concern/Water Quality Impairment ......................................................... 34 2.6.1. Nutrients................................................................................................................. 34 2.6.2. Temperature............................................................................................................ 37 2.6.3. Bacteria ................................................................................................................... 38 2.7. Source Identification ........................................................................................................ 40 2.7.1. Point Sources .......................................................................................................... 40 2.7.2. Nonpoint Sources.................................................................................................... 40 2.7.3. Background............................................................................................................. 41 2.7.4. Natural Contribution............................................................................................... 41 2.8. Carriers/Linkage............................................................................................................... 42 2.8.1. Sediment .................................................................................................................42 2.8.2. Ground Water ......................................................................................................... 42 2.9. Stressors ........................................................................................................................... 42 2.9.1. Stream/River Bank Modification............................................................................ 42 2.9.2. Flow Modification .................................................................................................. 43 3.0. Pollution Control Efforts ........................................................................................................ 43 3.1. Ongoing Projects .............................................................................................................. 43 3.1.1. Nonpoint Sources.................................................................................................... 43 3.1.2. Point Sources .......................................................................................................... 44 4.0 Bacteria Loading Analysis and Load Reduction ..................................................................... 45 4.1. Introduction ...................................................................................................................... 45 4.1.1. Review of Data ....................................................................................................... 45 4.1.2. Data for Bacteria Load Determination.................................................................... 46 4.2 Loading Calculations......................................................................................................... 46 4.2.1 Methods for Calculations:........................................................................................ 46 4.2.2. Die off Rates/Disappearance Rates......................................................................... 47 4.3. Load Reductions............................................................................................................... 48 4.3.1. Load Analysis ......................................................................................................... 48 4.3.2. Wasteload Allocation.............................................................................................. 49 4.3.3. Load Allocation ...................................................................................................... 50 4.3.4. Margin of Safety ..................................................................................................... 51 4.3.5. Wasteload Allocation, Load Allocation and Total Maximum Daily Load............. 51 5.0. Reasonable Assurance ............................................................................................................ 53 5.1. Point Sources................................................................................................................... 53 5.2. Non-Point Sources............................................................................................................ 53 5.3. Time frame for Compliance ............................................................................................. 55