1. West Metro Water Alliance A Path to Clean Water – Understanding TMDLs and Watershed Planning September 21, 2011 Diane Spector Wenck Associates, Inc.

2.  What is a TMDL?  What are the most common impairments?  How are TMDLs calculated?  What is the difference between a wasteload and load and why should I care?  Biotic impairments: fish and bugs matter

3. 1972 Federal Water Pollution Control Act was intended: “… to restore and maintain the chemical, physical, and biological integrity of the Nation’s waters.”

4. As of 2008  2,575 total impairments  Restored 14 impairments (2 lakes and 12 river segments)  680 TMDLs in development (excl toxics)  220 approved TMDLs in implementation In the Upper Mississippi River Basin  69 rivers and 263 lakes are impaired  468 TMDL studies needed

5.  1,774 impairments on 388 rivers and 647 lakes.  3,049 total impaired waters

6.  A Total Maximum Daily Load is a calculation of the maximum amount of a pollutant that a water body can receive and still meet water quality standards, and an allocation of that amount to the pollutant sources.

7.  WLA = Wasteload Allocation (attributed to existing or future permitted sources)  LA – Load Allocation (attributed to existing or future non-permitted sources)  MOS – Margin of Safety  RC – Reserve Capacity (Future Capacity)

8.  Watershed runoff  Point sources  Septic systems  Lake bottom sediments  Stream sediment oxygen demand  Atmospheric deposition Identify and measure or quantify sources of pollutant load

9.  Hydrologic and water quality model: P8, XP- SWMM, SWAT, HSPF  Predicted runoff volume based on actual precip  Pollutant load Model watershed hydrology and pollutant loading

12.  Lake response model: BATHTUB, MNLEAP  Streams: QUAL2K  Inputs: annual runoff volume, load, lake volume, depth, stream morphometry, fitting factors  Adjust factors until model predictions match actual observed data Model lake or stream response

13. Using calibrated model, reverse calculate maximum load

14. AllocationSource Existing TP LoadTP TMDL AllocationsLoad Reduction (lbs/year)(lbs/day)(lbs/year)(lbs/day)(lbs/year) Wasteload Watershed Runoff2,1325.81,3233.6 809 (38%) Load Upstream Lakes1350.41330.4 2 (<1%) Atmosphere2540.72540.70 Internal Load1,9915.51810.5 1,809 (91%) MOS -- Implicit -- TOTAL4,51212.41,8905.2 2,620 (58%)

15.  A Wasteload is a permitted source  Industrial point source  Construction permit  MS4s: stormwater  Wasteload allocations are regulated in your NPDES Phase I and II permits  Load allocations are not regulated by permit: internal load, natural processes, atmospheric deposition, rural runoff

16.  Individual allocations  One or more permitted sources are allocated their own wasteload and reduction  Categorical allocations  Groups of permittees are allocated wasteloads and reductions

17.  Measure with an Index of Biotic Integrity  IBI reflects composition and health of the biotic community in comparison to a reference  Summary of metrics, e.g.:  # target species  % community composition by target species  % or # pollution intolerant or tolerant species  # individuals or species

18.  First step is Stressor Identification study  Often identify stressors other than conventional pollutants  May be a numeric TMDL or surrogate such as flow or impervious cover  May also include non-numeric targets

19. Numeric:  Sediment oxygen demand load allocations, channel reshaping standards  Chloride wasteload allocations Non-numeric:  Specific habitat enhancements  Removal of fish barriers  Desirable flow duration curve

20.  The purpose of a TMDL is to identify the load reductions necessary to restore water quality and biotic integrity  Also includes general implementation actions that will likely help meet those targets  Not expected to “solve the problem”  Implementation Plan contains more detailed actions