16 –TMDL Evaluation

1. 16 –TMDL Evaluation Virginia Tech Biological Systems Engineering Department 2013 DEQ TMDL Workshop

2. Overview/Objectives • Bacteria TMDL Report – Briefly review the contents of a typical bacteria TMDL report • TMDL Evaluation - Discuss ways to use the TMDL model to verify portions of the TMDL report • Exercise: TMDL Evaluation

3. Bacteria TMDL Report

4. Bacteria TMDL Report • Report and contents have evolved • More concise • Example: Maury River

5. Bacteria TMDL Report • Executive Summary • Do the tables (values) match tables (values) in Chapters? • Description of the Impairment • Are the impairment type, length, receiving waters, initial listing year, and basin correct? • Watershed Characterization • Are refinements developed during the project reflected in the reported characterization? • Distribution of Pollutant Sources • Do reported source distributions make sense? Do they agree with on-observations on the ground?

6. Bacteria TMDL Report • Model Development • Does model performance meet specified criteria? • Explanation of MOS • Implicit vs Explicit – does approach match stated MOS? • Existing & Future Conditions • Does the distribution of existing conditions bacteria load make sense? • Were adjustments made for future conditions? • Total Waste Load Allocations • WLATotal = WLAx + WLAy + WLAz + WLAFG • Do the data comprising the WLATotalsum? • TMDL Equations • Do the data defining the TMDL (TMDL = WLA + LA + MOS) sum? • Downstream TMDL > Upstream TMDLs

7. Bacteria TMDL Report • Reasonable Assurance • Are stormwater permits included and/or addressed? • Public Participation • Are all relevant meetings included? • Source Assessment • Are sufficent/significant details about sources provided? • Model Development • Are calibrated model parameters within expected ranges?

8. TMDL Evaluation

9. TMDL Evaluation Comparison of TMDL Report to the HSPF TMDL model Confirm assumptions & refinements made during the project Hydrology & Water Quality Models typically provided to DEQ Existing Conditions Future Conditions/TMDL Add Future Conditions – Run 00?

10. Hydrology Model Variety of options Hydrology model performance addressed Some items to examine: Modeling period Watershed characterization Upstream conditions, if applicable Calibrated model parameters Permitted withdrawals & discharges Implementation of contingencies, if applicable

11. Modeling Period GLOBAL Block Modeling 2003 - 2010 Warm-up period: 2003 – 2005 Simulation: 2006 – 2010 From TMDL Report:

12. Land Use & Watershed Area From TMDL Report: • Gen-InfoBlock

13. Land Use & Watershed Area From TMDL Report: • Gen-Info Block • SchematicBlock

14. Upstream Boundary Conditions Flow • EXT SOURCES Block Flow From TMDL Report: James R. & Beaver Crk. Watersheds

15. Calibrated Model Parameters From TMDL Report: • PWAT Module • Parm 3Block • Parm4Block

16. Permitted Withdrawals & Discharges From TMDL Report: • EXT Sources Block • SFHs not simulated in Calibration • Sources simulated using observed data Calibration

17. Permitted Withdrawals & Discharges From TMDL Report: • NETWORK Block • Withdrawals remain active in EXT SOURCESBlock • Sources at design flow & Geomean std. Allocation

18. Implementation of Contingencies: Low Flow

19. Water Quality Model Even more options! Water quality model performance addressed Some items to examine: Calibrated model parameters Permitted pollutant loads Future growth implementation Confirm WLATotal

20. Calibrated Water Quality Parameters From TMDL Report: • IMPLND Module • QUAL-INPUT Block • RCHRES Module • GQ-GENDECAY Block

21. Permitted Pollutant Loads (e.g. Biosolids) From TMDL Report: • PERLND Module • QUAL-PROPS • MUTSIN time series • SCHEMATIC Block

22. Future Growth Implementation NETWORK Block WLAFG determined after TMDL Consider model units From TMDL Report:

23. Confirm WLATotal Refer to Calculations – may not have some model runs (e.g. MS4 WLA isolation) • Other loads turned off • SCHEMATIC Block • IMPLND areas modified

24. Exercise: TMDL Evaluation

25. TMDL Evaluation Exercise • Source Assessment Evaluation (use Table “Estimated annual fecal coliform loadings to the stream and the various land use categories …”) • TMDL Equations Evaluation

26. Questions?