Sauk River Bacteria and Nutrients Total Maximum Daily Load March 2018 wq-iw8-47e Prepared for: SAUK RIVER WATERSHED DISTRICT 524 Fourth Street South Sauk Centre, Minnesota 56378 Prepared by: WENCK ASSOCIATES, INC. 1800 Pioneer Creek Center P.O. Box 249 Maple Plain, Minnesota 55359-0249 763-479-4200 Wenck File #0019-109 2 Table of Contents TABLE OF CONTENTS .............................................................................................................. 3 TABLES .................................................................................................................................. 6 FIGURES ................................................................................................................................. 7 APPENDICES .......................................................................................................................... 8 TMDL SUMMARY ................................................................................................................... 9 1 INTRODUCTION ......................................................................................................... 11 1.1 Purpose ................................................................................................................ 11 1.2 watershed study area .......................................................................................... 11 1.3 Land use summary ............................................................................................... 13 1.4 impairment summary .......................................................................................... 13 1.5 Beneficial use Classifications ............................................................................... 14 1.6 Criteria used for listing ......................................................................................... 16 1.6.1 State of Minnesota Standards and Criteria for Listing ......................... 16 2 BACTERIA IMPAIRMENTS ........................................................................................... 17 2.1 overview of E. coli impaired reach watershed ..................................................... 17 2.2 E. coli Watershed Land use/land cover ................................................................ 17 2.3 E. coli Data Sources .............................................................................................. 17 2.3.1 Water Quality Data .............................................................................. 17 2.3.2 Streamflow Data .................................................................................. 20 2.3.3 Impairment Criteria for Impaired Reaches .......................................... 20 2.4 E. coli Allocation methodology ............................................................................ 22 2.4.1 Overview of Load Duration Curve Approach ....................................... 22 2.4.2 Margin of Safety ................................................................................... 24 2.4.3 Wasteload Allocations .......................................................................... 25 2.4.4 Nonpoint Source Load Allocation......................................................... 26 2.5 E. Coli Total maximum daily loads ....................................................................... 26 2.6 E. Coli Pollutant source assessment..................................................................... 27 3 2.6.1 E. coli Background Conditions .............................................................. 28 2.6.2 E. coli by Season and Flow Regime ....................................................... 28 2.6.3 Bacteria Levels in Upstream Lakes ....................................................... 31 2.6.4 Potential Bacteria Source Inventory .................................................... 31 2.6.5 Manure Application .............................................................................. 37 2.6.6 Feedlots and Pastures Near Streams ................................................... 37 2.6.7 Human Sources .................................................................................... 37 2.6.8 Urban Stormwater Runoff .................................................................... 39 2.6.9 Pollutant Source Assessment Summary ............................................... 41 3 LAKE EXCESS NUTRIENT IMPAIRMENTS ...................................................................... 43 3.1 Nutrients in Impaired Lakes ................................................................................. 43 3.1.1 Permitted Sources ................................................................................ 43 3.1.2 Non-Permitted Sources ........................................................................ 43 3.2 Nutrient TMDL Methodology............................................................................... 44 3.2.1 Nutrients Loading and Lake Response ................................................. 44 3.2.2 BATHTUB Model (Lake Response) ........................................................ 46 3.2.3 Phosphorus Load Summary .................................................................. 47 3.2.4 TMDL Allocation Methodology ............................................................ 48 3.2.5 Load Allocation Methodology .............................................................. 48 3.2.6 Wasteload Allocation Methodology .................................................... 48 3.2.7 Margin of Safety ................................................................................... 49 3.2.8 Lake Response Variables ...................................................................... 49 3.2.9 Seasonal Variation ................................................................................ 49 3.2.10 Reserve Capacity .................................................................................. 49 3.2.11 TMDL Summary .................................................................................... 50 3.3 Juergens Chain of Lakes TMDL ............................................................................. 50 3.3.1 Watershed Description ........................................................................ 50 3.3.2 Lake Morphometry............................................................................... 53 3.3.3 Historic Water Quality .......................................................................... 53 3.3.4 Biological Conditions ............................................................................ 54 3.3.5 Nutrient Sources .................................................................................. 54 4 3.3.6 TMDL Summary .................................................................................... 55 3.4 Individual lakes TMDL .......................................................................................... 57 3.4.1 Watershed Description ........................................................................ 57 3.4.2 Lake Morphometry............................................................................... 65 3.4.3 Historic Water Quality .......................................................................... 66 3.4.4 Biological Conditions ............................................................................ 66 3.4.5 Nutrient Sources .................................................................................. 67 3.4.6 TMDL Summary .................................................................................... 68 4 IMPLEMENTATION ..................................................................................................... 71 4.1 Introduction ......................................................................................................... 71 4.2 Implementation Framework ................................................................................ 71 4.2.1 E. coli and Nutrient Load Reduction Strategies .................................... 71 4.2.2 Installation or Enhancement of Buffers ............................................... 71 4.2.3 Pasture Management ........................................................................... 71 4.2.4 Manure Management .......................................................................... 72 4.2.5 Septic System Inspections and Upgrades ............................................. 73 4.2.6 Internal Nutrient Load Reductions ....................................................... 73 4.2.7 Studies and Biological Management plans .......................................... 73 4.2.8 Education.............................................................................................. 74 4.2.9 Adaptive Management ......................................................................... 74 5 REASONABLE ASSURANCE.......................................................................................... 75 5.1 Introduction ......................................................................................................... 75 5.2 Sauk River Watershed District ............................................................................. 75 5.3 County soil and water conservation districts ...................................................... 76 5.4 Monitoring ........................................................................................................... 76 5.5 Strategic efforts ................................................................................................... 77 5.6 Public Participation .............................................................................................