Modeling Approach and Quality Assurance Project Plan, Flathead

Flathead Lake Basin LSPC Modeling Approach and Quality Assurance Project Plan Technical Advisory Group Review Draft DO NOT CITE OR QUOTE February 9, 2012 Prepared for: U.S. Environmental Protection Agency Montana Operations Office Project Manager: Jason Gildea Prepared by: Tetra Tech, Inc. This quality assurance project plan (QAPP) has been prepared according to guidance provided in EPA Requirements for Quality Assurance Project Plans (EPA QA/R-5, EPA/240/B-01/003, U.S. Environmental Protection Agency, Office of Environmental Information, Washington, DC, March 2001) and EPA Guidance for Quality Assurance Project Plans for Modeling (EPA QA/G- 5M, EPA/240/R-02/007, U.S. Environmental Protection Agency, Office of Environmental Information, Washington, DC, December 2002) to ensure that environmental and related data collected, compiled, and/or generated for this project are complete, accurate, and of the type, quantity, and quality required for their intended use. Tetra Tech will conduct the work in conformance with the quality assurance program described in the quality management plan for Tetra Tech’s Fairfax Center and with the procedures detailed in this QAPP. Flathead Lake Basin LSPC Modeling Approach and QAPP Revision 2 Date: 2/9/2012 Page ii Revision History Document Name Revision Release Date Revisions Flathead Basin Modeling and 1.0 May 19, 2011 Submitted to EPA and DEQ for Nutrient TMDL Development – initial, internal review Modeling Approach and Quality Assurance Project Plan – Preliminary Review Draft Flathead Lake Basin LSPC 2.0 February 9, 2012 Addressed comments provided by Modeling Approach and Quality EPA and DEQ including a Assurance Project Plan – significant re-write of Section 4.5 Technical Advisory Group Review Draft DRAFT REPORT – DO NOT DISTRIBUTE Flathead Lake Basin LSPC Modeling Approach and QAPP Revision 2 Date: 2/9/2012 Page iii Approvals DRAFT REPORT – DO NOT DISTRIBUTE Flathead Lake Basin LSPC Modeling Approach and QAPP Revision 2 Date: 2/9/2012 Page iv Contents Contents ...................................................................................................................................iv 1.0 Introduction ........................................................................................................................ 1 1.1 Description of the Watershed .......................................................................................................... 3 1.2 Modeling Purpose and Need ........................................................................................................... 5 1.3 Project/Task Organization ............................................................................................................... 6 2.0 Modeling Goals and Objectives ........................................................................................ 9 3.0 Model Selection .................................................................................................................11 3.1 Prior Studies .................................................................................................................................. 11 3.2 Model Needs ................................................................................................................................. 12 3.3 LSPC Watershed Model ................................................................................................................ 13 4.0 LSPC Model Setup ............................................................................................................15 4.1 Simulation Period .......................................................................................................................... 17 4.2 Supporting Documentation ........................................................................................................... 17 4.3 Watershed Segmentation ............................................................................................................... 19 4.4 Waterbody Representation ............................................................................................................ 23 4.4.1 Streams ........................................................................................................................... 23 4.4.2 Lakes ............................................................................................................................... 24 4.5 Weather Data ................................................................................................................................. 28 4.6 Land Use/Land Cover Representation .......................................................................................... 29 4.6.1 Time-Variable Land Use ................................................................................................. 31 4.6.2 Roads .............................................................................................................................. 35 4.6.3 Timber Harvest ............................................................................................................... 36 4.6.4 Forest Fires .................................................................................................................... 38 4.6.5 Septic Systems ................................................................................................................. 39 4.6.6 Urban Stormwater .......................................................................................................... 42 4.6.7 Bank Erosion and Mass Wasting .................................................................................... 43 4.6.8 Agriculture ...................................................................................................................... 45 4.6.9 Golf Courses ................................................................................................................... 47 4.7 Point Sources ................................................................................................................................. 50 4.7.1 Wastewater Treatment Plants and Other Non-stormwater NPDES Dischargers .......... 50 4.7.2 Non-MPDES Dischargers ............................................................................................... 51 5.0 Model Calibration and Uncertainty Analysis ...................................................................52 5.1 LSPC Model Calibration ............................................................................................................... 52 5.1.1 Flow Calibration............................................................................................................. 53 5.1.2 Water Chemistry Calibration Sites ................................................................................. 55 5.1.3 Acceptance Criteria for Model Calibration .................................................................... 58 5.1.4 Model Validation ............................................................................................................ 60 5.2 Uncertainty Analysis ..................................................................................................................... 61 5.3 Reconciliation with User Requirements ........................................................................................ 63 6.0 Nondirect Measurements (Secondary Data Acquisition Requirements) .......................64 6.1 Quality Control for Nondirect Measurements ............................................................................... 64 6.2 Data Management and Hardware/Software Configuration ........................................................... 64 7.0 Model Uses and Scenarios ...............................................................................................65 7.1 Existing Condition Scenario ......................................................................................................... 65 7.2 Natural Occurring Scenario ........................................................................................................... 66 7.3 Water Quality Standards Compliance ........................................................................................... 66 7.4 BMP Scenarios .............................................................................................................................. 66 8.0 Assessment and Response Actions and Reports to Management ...............................67 8.1 Assessment and Response Actions ............................................................................................... 67 DRAFT REPORT – DO NOT DISTRIBUTE Flathead Lake Basin LSPC Modeling Approach and QAPP Revision 2 Date: 2/9/2012 Page v 8.1.1 Model Development Quality Assessment ........................................................................ 68 8.1.2 Software Development Quality Assessment .................................................................... 68 8.1.3 Surveillance of Project Activities .................................................................................... 69 8.2 Reports to Management ................................................................................................................ 69 9.0 Model Documentation .......................................................................................................70 10.0 Schedule ..........................................................................................................................71 11.0 References .......................................................................................................................73

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