Portneuf River TMDL Revision and Addendum Lower Marsh Creek, upstream of the confluence with the Portneuf River Department of Environmental Quality February 2010 Final Version Portneuf River TMDL Revision and Addendum February 2010 ii Portneuf River TMDL Revision and Addendum February 2010 Portneuf River TMDL Revision and Addendum Prepared by: Andrew Ray Oregon Institute of Technology 3201 Campus Drive Klamath Falls, Oregon 97601 Pocatello Regional Office Department of Environmental Quality 444 Hospital Way #300 Pocatello, Idaho 83201 iii Portneuf River TMDL Revision and Addendum February 2010 iv Portneuf River TMDL Revision and Addendum February 2010 Acknowledgments The Pocatello Regional Office sincerely thanks all those who have participated in the Portneuf Watershed Advisory Group. Members include: Kim Gower - J. R. Simplot Co., Wilder Hatch - Caribou Soil Conservation District, Kevin Koester – Ag, Jim Mende – Idaho Department of Fish and Game, Hannah Sanger – formerly with Portneuf Greenway Foundation and now with the City of Pocatello, John Sigler - City of Pocatello, Brad Higginson – USDA Forest Service Caribou-Targhee NF, Roger Thompson – SEIFF, Keene Hueftle – SEIEN, Candon Tanaka - Shoshone-Bannock Tribes – WQ, Elliot Traher – Natural Resources Conservation Service , and Lin Whitworth - Bannock County. Input and/or participation by the following individuals was also very valuable: Amy Jenkins and Flint Raben - Idaho Association of Soil Conservation Districts, Sue Skinner, Ben Cope, Tracy Chellis, and Lindsay Guzzo - US EPA Region 10. The DEQ would also like to thank Wendy Greene Lowe with P2 Solutions for facilitating the WAG meetings, Richard Inouye for his continued assistance with sonde data management and summaries and for the cover photo of lower Marsh Creek, and Melissa Thompson for the production of the watershed and subwatershed maps contained herein. v Portneuf River TMDL Revision and Addendum February 2010 Table of Contents Acknowledgments.........................................................................................................v Table of Contents.........................................................................................................vi List of Equations..........................................................................................................ix List of Tablesx List of Figures .............................................................................................................xv List of Appendices .....................................................................................................xix Abbreviations, Acronyms, and Symbols ...................................................................xx Executive Summary ..................................................................................................xxv Subbasin at a Glance........................................................................................... xxv Key Findings ...................................................................................................... xxviii 1. Subbasin Assessment – Watershed Characterization............................................1 1.1 Introduction ........................................................................................................1 Background.......................................................................................................2 Idaho’s Role ......................................................................................................2 1.2 Physical and Biological Characteristics...............................................................3 Hydrology..........................................................................................................4 Climate..............................................................................................................6 Biological Assemblages.....................................................................................6 1.3 Cultural Characteristics ......................................................................................8 2. Subbasin Assessment – Water Quality Concerns and Status ...............................9 2.1 Water Quality Limited Assessment Units Occurring in the Subbasin ................21 About Assessment Units .................................................................................23 2.2 Applicable Water Quality Standards .................................................................24 Beneficial Uses................................................................................................24 Criteria to Support Beneficial Uses..................................................................28 2.3 Pollutant/Beneficial Use Support Status Relationships .....................................32 Temperature....................................................................................................32 Dissolved Oxygen ...........................................................................................32 Sediment.........................................................................................................33 Bacteria...........................................................................................................34 Nutrients..........................................................................................................35 Sediment – Nutrient Relationship ....................................................................36 Floating, Suspended, or Submerged Matter (Nuisance Algae) ........................36 2.4 Summary and Analysis of Existing Water Quality Data....................................37 Flow Characteristics ........................................................................................38 vi Portneuf River TMDL Revision and Addendum February 2010 Water Column Data.........................................................................................40 Biological and Other Data................................................................................72 Status of Beneficial Uses.................................................................................79 Conclusions.....................................................................................................79 2.5 Data Gaps........................................................................................................80 3. Subbasin Assessment–Pollutant Source Inventory .............................................81 3.1 Sources of Pollutants of Concern .....................................................................81 Point Sources..................................................................................................82 Nonpoint Sources............................................................................................85 3.2 Data Gaps........................................................................................................86 Point Sources..................................................................................................86 Nonpoint Sources............................................................................................87 4. Subbasin Assessment – Summary of Past and Present Pollution Control Efforts ...............................................................................................................89 5. Total Maximum Daily Loads ...................................................................................93 5.1 In-stream Water Quality Targets.......................................................................94 Target Selection and Applicable Criteria..........................................................96 Monitoring Points...........................................................................................103 Design Conditions .........................................................................................106 5.2 Estimates of Existing Pollutant Loads and Target Loads ................................109 5.2a Mainstem Portneuf River ..............................................................................109 Sediment.......................................................................................................112 Total Phosphorus ..........................................................................................120 Oil and Grease ..............................................................................................129 5.2b Tributaries ....................................................................................................132 Escherichia coli .............................................................................................132 Sediment.......................................................................................................135 Nutrients........................................................................................................142 Total Nitrogen................................................................................................143 Total Phosphorus ..........................................................................................144 Dissolved Oxygen .........................................................................................149 Construction Storm Water and TMDL Wasteload Allocations ........................150 5.2c Reasonable Assurance.................................................................................151 5.3 Implementation Strategies..............................................................................153 Time Frame...................................................................................................154