1. Total Maximum Daily Load (TMDL)
Cara Cowan Watts
Graduate Student
Biosystems Engineering

2. Source of Class Materials
Presentations and Handouts
adapted from
The U.S. EPA’s
Water Quality Standards Academy
November 27-December 1, 2006
Washington, DC

3. Total Maximum Daily Load (TMDL)
Strategy for achieving WQS
303(d) Process
Based on the relationship between pollutant sources and the condition of a water body
Describes an allowable pollutant load and allocates it among several sources

4. Pollutant Dredged spoil Solid waste Incinerator residue
Filter backwash
Sewage sludge
Munitions
Chemical wastes
Biological materials
Cellar dirt
Sand
(Some) radioactive materials
Heat
Wrecked or discarded equipment,
Rock
Industrial, municipal, and agricultural waste discharged into water

5. TMDLs
Amount of specific pollutant a waterbody can receive and assimilate to still meet water quality standards
States and tribes are required to develop TMDLs for waters on their 303(d) lists
TMDLs are approved or disapproved by EPA
IF disapproved, EPA develops the TMDL

6. TMDL Components Allowable pollutant load (cap)
Allocation of cap among sources
Margin of safety (MOS)
TMDL = ΣSWLAi + ΣSLAi + MOS
ΣSWLAi: Sum of waste load allocations (point sources)
ΣSLAi: Sum of load allocations (nonpoint sources)
MOS
Extra measure of protection due to uncertainty
Can be explicit (percentage) or implicit (safety factors and assumptions in modeling)

7. Components of TMDL
Wasteload allocations (WLAs) assigned to each point source
Load allocations (LAs) assigned to nonpoint sources
WLAs and LAs established so predicted receiving water concentrations do not exceed water quality criteria
Other Loads
(Nonpoint Background)
Reserve
Capacity
Point Source #1 #2 #3 #4

8. TMDL “Caps” For specific pollutants For pollutant indicators
Sediment, nitrogen, phosphorus, temperature, copper, mercury, etc.
For pollutant indicators
Biochemical Oxygen Demand (BOD)
Chemical Oxygen Demand (COD)
Not necessarily daily
Weekly, monthly or yearly
May vary seasonally

9. TMDL Allocations
Each point source with individual NPDES permit receives a wasteload allocation (WLA)
Point sources covered under general permits can also get a wasteload allocation (WLA)
Individual sources, categories, subcategories of nonpoint sources are represented by a load allocation (LA)
No EPA rules on how to allocate

10. NPS Source Category 2 (LA) NPS Source Category 1 (LA)
TMDL Allocation
Sub Watershed 1
MOS
Reserve Capacity
Sub Watershed 2
Natural Background
Point Source 1 (WLA)
NPS Source Category 2 (LA)
NPS Source Category 1 (LA)
Point Source 2 (WLA)

11. TMDL Pollutants Completed
TMDL Review
Recent TMDLs
Pathogens
36%
25%
Nutrients/BOD/Dissolved Oxygen/Algal
20%
14%
Pesticides (incl. DDT)
11% 4%
Turbidity/Sediment/TSS 9% pH 6%
2.7%
Thermal modifications 5%
Metals (not incl. Mercury)
12%
PCBs 3%
1.0%
Mercury
1.3%
Conductivity/TDS/Chlorides
<2%
Chlorine
<1%
1.2%
Sulfates
Unionized ammonia
<0.5%
2.5%
Noxious aquatic plants
0.1%

12. Load Calculations & Reductions
78% of TMDLs calculate existing load even though not required by regulations
Reductions range from 0 to 100%
Pathogen TMDLs most often require very high percent reductions
30% of TMDLs refine LA into more than one category
Up to 18 subcategories (median = 3)

13. “319” Programs Available to states, territories and tribes
40% “state” match required (dollars and/or in-kind)
EPA allocation formula
population, farmland, water quality problems, etc
In FY06, Congress appropriated $204 million
Down from high of $238 in ’02

14. 319 Grant Opportunities 104.6 Dollars (Millions) 21.9 18.2 17.5
Type of Activity

15. $100M “310” Funds Incremental
Cannot use for on-the-ground BMP implementation until
Watershed plan developed
Show how BMPs fit into that plan
“Waivable ceiling” of 20% of incremental funds can be used to develop watershed plans

16. Load Reduction Impact Trends
Reductions allocations
TMDL Review
Only PS TMDL, PS reduced
2%*
Only NPS TMDL, NPS reduced
38%
PS/NPS, NPS load reduced
15%**
PS/NPS, PS load reduced 1%
PS/NPS, Both loads reduced
39%
No allocations made; no load reductions required; or indeterminate 4%

17. Questions?