1. Total Maximum Daily Load Program
TMDLs and Stormwater
Chris Loft
Total Maximum Daily Load Program
Texas Commission on Environmental Quality

2. Texas TMDL Program
Texas is required under Section 303(d) of the federal Clean Water Act to list impaired waters and to take action to restore them.
Impaired waters are identified every two years on the Texas Integrated Report of Surface Water Quality.
A surface water body is considered impaired if it does not meet the criteria for support of one or more of its beneficial uses, as defined in the Texas Surface Water Quality Standards ( TAC).

3. Texas TMDL Program TMDL – Total Maximum Daily Load
Determines the maximum amount (load) of a pollutant that a water body can receive and still maintain uses
Allocates this load to broad categories of sources in the watershed
Adopted by TCEQ
Approved by EPA

4. Typical TMDL Pollutants
Bacteria
Bacteria (Oyster Waters)
Chloride, Sulfate, Total Dissolved Solids
Dioxin in Edible Tissue
Depressed Dissolved Oxygen
Impaired Aquatic Life
Mercury in Edible Tissue
Metals in Water
PBCs in Edible Tissue pH
Sediment Toxicity
Water Toxicity

5. Texas TMDL Program Implementation Plan
A stakeholder developed plan to improve water quality
Includes a description of regulatory and voluntary management measures
Includes a plan for sustaining the implementation effort over time
Approved by TCEQ

6. Texas TMDL Program Update
New Strategy CWA 303 (d) Vision
Developed by the states and EPA in
New performance measure replaces the current number of TMDLs per year measure
The goal is the number of watershed acres covered by a TMDL or other approved plan
7 year effort

7. TMDL Allocations
TMDL (MPN/day) = Criterion * flow (cfs) * conversion factor
Expressed in units per day

8. TMDL Allocations TMDL = WLAWWTF + WLAPSW +LA + MOS
WLAWWTF – Waste Load Allocation for WWTF Discharges
WLAPSW – Waste Load Allocation for Permitted Stormwater Discharges
LA – Load Allocation
MOS – Margin of Safety
Expressed in units per day

9. TMDL Allocations Waste Load Allocations – Regulated Sources
Load allocation for wastewater treatment facilities
Load allocation for all permitted stormwater sources
Load Allocations – Unregulated

10. TMDL Allocations WLAWWTF Required by EPA
Individual facilities receive load allocations based on target concentrations
Based on full permitted flow
Based on a criterion (Enterococci or E. coli)
Updated quarterly through the Water Quality Management Plan

11. TMDL Allocations WLAPSW = (TMDL – WLAWWTF – FG – MOS) * FDASWP
WLAPSW – Sum of all Regulated Stormwater Loads
TMDL – Total Maximum Daily Load
WLAWWTF – Sum of all WWTF Loads
FG – Sum of Future Growth Loads from Potential Permitted Facilities
MOS – Margin of Safety
FDASWP – Fractional Portion of Drainage Area under Jurisdiction of Stormwater Permits

12. AU Subwatershed Area (mi2) Percentage Stormwater Regulation (%)
TMDL Allocations
FDASWP
Urbanized Area / Subwatershed Area AU
AU Urbanized Area (mi2)
AU Subwatershed Area (mi2)
Percentage Stormwater Regulation (%)
5505_01
2.68
15.81
16.95
5506_02 88
120.5
73.02
5506A_01
12.7
40.56
31.31
Table showing examples for three AUs of AU Urbanized Area, AU Subwatershed Area, and Percentage Stormwater

13. TMDL Allocations WLAPSW Single aggregate load limit
For municipal, industrial, and construction stormwater permits combined
Loads are not assigned to individual permits
Determination of allocation based on proportion of urbanized area in watershed covered by a municipal separate storm sewer system (MS4) entity

14. TMDL Allocations LA = TMDL – WLA – FG – MOS
LA – Allowable loads from unregulated sources
TMDL – Total Maximum Daily Load
WLA – Sum of all WWTF Loads and all regulated sources
FG – Sum of Future Growth Loads from Potential Permitted Facilities
MOS – Margin of Safety

15. TMDL Allocations Final TMDL
Units expressed as billion MPN/day Enterococci AU
TMDL
WLAWWTF
WLASW LA
MOS
5505_01
137.8
11.20
18.79
100.92
6.89
5506_02
150.3
10.5
0.05
132.7
7.5
Table showing examples for two AUs of TMDL, WLAWWTF, WLASW, LA, and MOS.

16. Implementation Plans
Water quality improvement plans developed by stakeholders in the affected watershed
Implementation plans are collaborative and involve a wide variety of stakeholders in the affected watershed
Citizens, watershed interest groups
State, local, and federal agencies
Regulated organizations

17. Implementation Plans General Strategy Develop a Coordination Committee
Identify and organize Work Groups
Develop a Water Quality Improvement Plan
Promote Plan to gain cooperation in the watershed

18. Implementation Plans
Plans describe the activities that will be implemented over a specific time period by the stakeholders to improve water quality
Strategy for continuing the effort is crucial
Stakeholders meet annually to review progress
The stakeholders revise the plan as needed

19. Implementation Plans in Texas
Map of Texas showing location of TMDL and I-Plan development and implementation watersheds

20. Implementation Plan
The Implementation part of the “TMDL” can establish the “consistent” requirements for WWTFs
Permitted municipal stormwater requirements agreed upon in the Implementation Plan may be submitted as part of a Stormwater Management Program for an MS4
Industrial Stormwater Permits and Construction Stormwater Permits may be affected.

21. Stormwater Management Measures Considered in an Implementation Plan
Generally the same measures an MS4 can use under its MS4 permit
Management of runoff (Best Management Practices or BMPs)
Detention basins, filter strips, infiltration basins, porous pavement, detention ponds, swales
Create and maintain an online library of best practices
Organize and conduct training sessions
Develop recognition program
Retrofit and inspect existing BMPs

22. Stormwater Management Measures Considered in an Implementation Plan
Generally the same measures an MS4 can use under its MS4 permit continued
Management of operations to decrease or eliminate pollutants in runoff
Spill prevention and control, source controls, public outreach, and education
Street sweeping
Storm drain stenciling
Support or encourage Low Impact Development

23. Other Management Measures That May Be Considered
Map stormwater system
Monitoring
Additional instream monitoring
Outfall monitoring to identify sources
BMP effectiveness sampling
Search for specific pollutant sources
Illicit Discharges
System mapping, detection, and elimination

24. Other Management Measures That May Be Considered
Sanitary Sewer Overflows
Reporting
Cleaning and inspection of collection system
Video surveys
Consider sanitary sewer overflow initiative
Develop, conduct Fats, Oil, and Grease (FOG) reduction program

25. Examples from other Implementation Plans
Consider instream structural modifications that do not increase flood risk
Decrease impervious cover
Incorporate bacteria reduction requirements as a secondary priority of flood control projects and any other new or retrofitted infrastructure projects
Modify outfalls to 'treat' water before it enters channels

26. Examples from other Implementation Plans
Conduct research to identify the biggest bacteria sources from stormwater
Apply implementation activities to the biggest sources that are most cost effective
Double the urban tree canopy
Construct treatment wetlands

27. Examples from other Implementation Plans
Install filters or vegetative strips at inlets to capture materials
Review animal control ordinances and implement measures to control nuisance animals
Install pet waste disposal stations
Clean sewer lines and outfalls and fit with stormwater wetlands

28. Implementation Plans
It is the stakeholders in the watershed who contribute to the development of the Implementation Plan that determine what will be required to manage the loads from all sources, including stormwater.

29. For More Information on TMDLs
TCEQ TMDL Program Website:
Chris Loft
(512)