Draft Osakis Lake Area Excess Nutrients Total Maximum Daily Load Report Prepared for: Sauk River Watershed District Minnesota Pollution Control Agency Original May 2013 Revision December 2016 wq-iw8-39b Draft Osakis Lake Area Excess Nutrients Total Maximum Daily Load Prepared for: SAUK RIVER WATERSHED DISTRICT MINNESOTA POLLUTION CONTROL AGENCY Prepared by: WENCK ASSOCIATES, INC. 1800 Pioneer Creek Center P.O. Box 249 Maple Plain, Minnesota 55359-0249 (763) 479-4200 Original May 2013 Wenck File #0147-251 Revision December 2016 Minnesota Pollution Control Agency 520 Lafayette Road North St. Paul, Minnesota 55155 2 Table of Contents ACRONYMS…………………………………………………………………………………………………………………………………………8 TMDL SUMMARY……………………………………………………………………………………………………………………………… 9 EXECUTIVE SUMMARY…………………………………………………………………………………………………………………… 10 2016 Revisions to Faille Lake TMDL ............................................................................................... 11 1.0 Introduction ..................................................................................................................................... 12 1.1 Purpose ............................................................................................................................. 12 1.2 Problem Identification ...................................................................................................... 12 2.0 Watershed and Lake Characterization ............................................................................................ 13 2.1 Impaired Waters and Minnesota Water Quality Standards ............................................. 13 2.2 Lake and Watershed Descriptions .................................................................................... 13 2.3 Land Use ............................................................................................................................ 17 2.4 Lake Water Quality ........................................................................................................... 19 2.4.1 Introduction ...................................................................................................... 19 2.4.2 Lake Monitoring Efforts..................................................................................... 19 2.4.3 Lake Monitoring Data Processing...................................................................... 21 2.4.4 Temperature and Dissolved Oxygen ................................................................. 21 2.4.5 Total Phosphorus .............................................................................................. 22 2.4.6 Chlorophyll-a ..................................................................................................... 23 2.4.7 Secchi Depth ...................................................................................................... 24 2.4.8 Conclusions ....................................................................................................... 26 2.5 Lake ecology ...................................................................................................................... 26 2.5.1 Fish Populations ................................................................................................ 26 2.5.2 Carp ................................................................................................................... 30 2.5.3 Aquatic Plants .................................................................................................... 30 2.5.4 Shoreline Habitat and Conditions ..................................................................... 33 2.6 Stream monitoring ............................................................................................................ 33 3.0 Nutrient Sources and Lake Response .............................................................................................. 34 3.1 Introduction ...................................................................................................................... 34 3.2 Modeling Approach .......................................................................................................... 34 3.2.1 Watershed Model ............................................................................................. 34 3.2.2 Internal Loading ................................................................................................ 35 3.2.3 Atmospheric Load ............................................................................................. 35 3.2.4 BATHTUB Model (Lake Response) ..................................................................... 36 3.3 Estimation of Source Loads ............................................................................................... 37 3.3.1 Atmospheric Load ............................................................................................. 37 3.3.2 Watershed Phosphorus Loading ....................................................................... 37 3.3.2.1 Upstream Lakes ................................................................................ 37 3.3.2.2 Loading by Land use ......................................................................... 38 3 3.3.2.3 Animal Agriculture............................................................................ 40 3.3.3 Septic Systems ................................................................................................... 44 3.3.4 Internal Phosphorus Loading ............................................................................ 45 3.4 Linking Water Quality Targets and Sources ...................................................................... 46 4.0 TMDL Allocation ............................................................................................................................... 50 4.1 Total maximum daily load calculations ............................................................................. 50 4.1.1 Total Loading Capacity ...................................................................................... 50 4.1.2 Load Allocations ................................................................................................ 50 4.1.3 Wasteload Allocations ....................................................................................... 50 4.1.3.1 Construction and Industrial Stormwater ......................................... 51 4.1.3.2 Confined Animal Feeding Operations (CAFOs) ................................ 51 4.1.4 Margin of Safety ................................................................................................ 51 4.1.5 Summary of TMDL Allocations .......................................................................... 52 4.2 Lake Response Variables ................................................................................................... 54 4.3 Seasonal and Annual Variation ......................................................................................... 57 4.4 Reserve Capacity ............................................................................................................... 57 5.0 Public Participation .......................................................................................................................... 58 5.1 Introduction ...................................................................................................................... 58 5.2 Stakeholder Meetings ....................................................................................................... 58 6.0 Implementation ............................................................................................................................... 59 6.1 Introduction ...................................................................................................................... 59 6.2 Implementation Framework ............................................................................................. 59 6.2.1 Watershed and Local Plans ............................................................................... 59 6.2.2 Adaptive Management ...................................................................................... 59 6.3 Nutrient Reduction Strategies .......................................................................................... 59 6.3.1 External Nutrient Load Reductions ................................................................... 60 6.3.2 Studies and Biological Management Plans ....................................................... 62 6.3.3 Education........................................................................................................... 62 7.0 Reasonable Assurance ..................................................................................................................... 63 7.1 Introduction ...................................................................................................................... 63 7.2 Sauk River Watershed District .......................................................................................... 64 7.3 Todd and Douglas County SWCDs .................................................................................... 64 7.4 Monitoring ........................................................................................................................ 65 8.0 Literature Cited ................................................................................................................................ 66 9.0 Faille Lake 2016 Addendum: ...........................................................................................................