1. Total Maximum Daily Loads (TMDLs): An Overview of TMDLs in Texas
2017 EPA Region 6 Stormwater Conference
San Antonio, Texas
Roger Miranda, P.G.
Total Maximum Daily Load Program
Texas Commission on Environmental Quality
September 18, 2017
Good afternoon. I’m going to be presenting a brief overview of the TCEQ’s Total Maximum Daily Load program in Texas with an emphasis on the role TMDLs play in urban stormwater regulation and management.

2. The Law requires us to ask…
What are the problems?
How bad are they?
How can they be corrected?
The federal Clean Water Act requires all states to monitor water quality and compare it to criteria set up to protect everything from aquatic plants and animals to people.
This monitoring covers many things, from specific toxic chemicals to temperature to pH to bacteria.

3. 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).
States must develop a TMDL for each pollutant that contributes to the impairment of a listed waterbody
Information on impaired water bodies in Texas can be found on the TCEQ website on the Integrated Report page. The list of impaired water bodies is called the 303(d) list, named after the section of the CWA that requires it
This list includes several broad categories including categories 4 and 5 that together comprise the list of all impaired waterbodies
Specifically:
4A – TMDL has been completed and approved by EPA
5A – TMDLs are underway, scheduled or will be scheduled for one or more parameters
5B – a review of the water quality standards for one or more parameters will be conducted before a management strategy is selected
5C – additional data or information will be collected and/or evaluated for one or more parameters before a management strategy is selected
Standards example:
Bacteria causing non-support of the contact recreation use

4. TMDL: Total Maximum Daily Load
How much is too much?
How bad is the problem?
Where is it coming from?
The first part of this process of addressing water quality impairments is the development of Total Maximum Daily Loads – TMDLs.
A TMDL is like a pollution budget that is based on the assimilative capacity of a water body — it determines the amount of a particular pollutant that a water body can receive and still meet its applicable water quality standards. Many of the examples I’ll discuss today are associated with bacteria impairments. Indicator bacteria, such as E. coli and Enterococcus, are used to determine impairments due to potential pathogens in surface water. A TMDL is a way of calculating the highest, allowable amount of all pollutants in surface waters, including indicator bacteria. It’s a target for meeting water quality.
And we also look, in broad terms, for the sources of the problem.

5. Texas TMDL Program TMDL – Total Maximum Daily Load
CFR Title 40 Section 130.7
Determines the maximum amount (load) of a pollutant a water body can receive and still maintain uses (expressed in load/day)
Allocates this load to broad categories of sources in the watershed
Adopted by TCEQ
Approved by EPA
The primary objective of the TMDL program is to restore and maintain the beneficial uses of surface water bodies. Uses include recreation, support of aquatic life, drinking water supply and others.

6. Typical TMDL Pollutants
Bacteria
Bacteria (Oyster Waters)
Chloride, Sulfate, Total Dissolved Solids
Depressed Dissolved Oxygen pH
PCBs in in Water, Sediment or Aquatic Life Tissue
Dioxins in Water, Sediment or Aquatic Life Tissue
Metals in Water, Sediment or Aquatic Life Tissue
Volatile Organic Compounds (VOCs) in Water, Sediment, or Aquatic Life Tissue
Over 40% of the impaired water bodies in Texas waterbodies are impaired for bacteria. Every river basin in the state has at least one bacteria impairment. And we have lots of experience working with stakeholders, contractors, water quality partners in addressing bacteria impairments
*Typically, dissolved, suspended and sediment-attached pollutants may be most effectively addressed by MS4 permittees.

7. TMDLs in Texas As of August 2017 TMDLs Stream Segments Stream Miles
Watershed Area (Mi2)
225 59
2,412
25,618
The TCEQ’s TMDL Program is in its 19th year and, in that time, the program has developed 225 TMDLs in 413 Assessment nits in Texas.

8. 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 area covered by a TMDL or other approved plan
7 year effort ( )
Beginning in 2013, the EPA, in partnership with state and tribal governments, developed a new strategy or “vision” for addressing impairments in surface water bodies…new performance measures for state TMDL programs…7 year effort ( )

9. TMDLs and TMDL Allocations
The maximum amount (load) of a pollutant a water body can receive and still maintain its uses.
E. Coli example:
TMDL (MPN/day) = Criterion (MPN/100ml) * flow (cfs or cms) * conversion factor
Expressed in units per day
TMDLs are the best possible estimates of assimilative capacity of a waterbody for a specific pollutant under consideration.
Commonly expressed as a load with units of mass (or counts) per day but may also be expressed in other ways such as concentration, toxicity or even heat.
A simple example would be bacteria counts (often a statistical value like Most Probable Number) per day. In this example we start with the acceptable criterion instream and simply multiply it by a representative, or a protective, flow value (i.e., median flow or the median of high-range flows, or low flows such as 7Q2 or 7Q10).
Using conversion factors, we can express the loading limit in terms of numbers of bacteria per day. This equation is then used to allocate that maximum load into two broad categories of pollution sources, regulated sources and unregulated sources, plus a margin of safety. Future growth can also be incorporated into the equation, when feasible, but allocations for future growth are not required by federal regulations. Most of our TMDLs, in fact, contain an allocation for future growth.
What do “maximum” and “daily” mean? application to stormwater is a little different because the discharges authorized by stormwater permits are considered intermittent and variable.
Who or what receives “allocations” ? I’ll try to get into that in a little more detail later in this presentation.
TMDL = Σ WLA + Σ LA + MOS
TMDL = Σ WLA + Σ LA + FG + MOS

10. TMDL Allocations TMDL = Σ WLA + Σ LA + FG + Σ MOS
Waste Load Allocations (WLA) – Regulated Sources
Load Allocations (LA) – Unregulated Sources
Future Growth (FG) – Potential Regulated Sources
Margin of Safety (MOS) – Explicit or Implicit
So let me explain what some of these terms mean. The waste load allocation, or WLA, is the sum of loads from regulated sources (think NPDES regulations).
The load allocation, or LA, is the sum of loading from all unregulated sources. I’ve already mentioned future growth. A margin of safety is required of all TMDLs; it is used to address uncertainty in the TMDL analysis and it can be expressed explicitly or implicitly - explanation.

11. TMDL Allocations WLA = WLAWWTF + WLAPSW
WLAWWTF – Waste Load Allocation for Wastewater Treatment Facility Discharges
WLAPSW – Waste Load Allocation for Permitted Stormwater Discharges
Expressed in Units Per Day
There was a time, early in the TCEQ’s TMDL program, in which the waste load allocation referred strictly to the portion of the TMDL allocated to point source discharges, such as WWTFs.
However, with the advent of Phase II SW regulations and the establishment of the TCEQ’s stormwater program, we started splitting the TMDL WLAs into separate allocations for WWTFs and regulated storm water.

12. TMDL Allocations WLAWWTF
Individual facilities receive load allocations which can also be expressed in terms of effluent limits (i.e. effluent flows and concentrations)
Based on full permitted flow
Based on an instream criterion (for example E. coli or Enterococci to support PCR)
Updated quarterly through the Water Quality Management Plan
For the WLAWWTF, an aggregate TMDL allocation is made to permitted wastewater treatment facilities. The allocation is typically the sum of individual waste loads for existing WWTFs, calculated as their full permitted flow times the water quality criterion (or a high percentage of the criterion, in the case of an explicit MOS).
The criteria associated with primary contact recreation is 35 counts per 100 mL Enterococci and 126 counts per 100 mL for E. coli.
WWTFs discharging to the TMDL segments are assigned an effluent limit based on the TMDL allocation. The individual allocations for each WWTF in the watershed are specified in the TMDL document
Changes in WWTFs (a new permit, increase or reductions in permitted flow) are handled through updates to the water quality management plan

13. TMDL Allocations WLAPSW = (TMDL – WLAWWTF – FG – MOS) * FDAPSW
WLAPSW – Sum of all Regulated Stormwater Loads
TMDL – Total Maximum Daily Load
WLAWWTF – Sum of all WWTF Loads
FG – Sum of Future Growth Loads for Potential Permitted Facilities
MOS – Margin of Safety
FDAPSW – Fractional Portion of Drainage Area under Jurisdiction of Stormwater Permits
To calculate WLAPSW, the portion of the total drainage area under the jurisdiction of stormwater permits (FDAPSW) must be determined to estimate the portion of the overall runoff that should be allocated to WLAPSW
Once this fraction is determined, it is applied to the total runoff load, which is what is left of the TMDL once all other allocations are made (WLAWWTF , FG and MOS).
WLAPSW is an allocation but it is difficult to call it a daily load because of the flow variability.

14. TMDL Allocations FDAPSW Urbanized Area = Subwatershed Area 20 mi2 =
100 sq. miles
20 sq. miles
FDAPSW
Urbanized Area
Subwatershed Area =
20 mi2
100 mi2 = =
20%
FDAPSW is calculated based on the combined area under the jurisdiction of regulated stormwater permits.
This figure shows an example of how FDAPSW is calculated. It is simple the ratio or percentage of the Urbanized Area in the TMDL watershed or subwatershed to the total area in the TMDL watershed or subwatershed.
For Phase 1 MS4 permits the jurisdictional area is defined by the city limits. Phase II jurisdictional area is defined as the intersection of the city limits and the 2000 or 2010 census urbanized areas.
WLAPSW = FDAPSW * Total Runoff Load

15. TMDL Allocations WLAPSW Single aggregate load allocation
For municipal, industrial, and construction stormwater permits combined
Loads are not assigned to individual permits
Determination of the aggregate WLAPSW is based on the proportion of urbanized area in the TMDL watershed
The WLAPSW is expressed as a single aggregate load for all permitted stormwater in the TMDL watershed or subwatershed; it subsumes all land permitted under municipal, industrial, and construction stormwater permits. Allocations for individual stormwater permitees are not specified in the TMDL

16. TMDL Allocations LA = TMDL – ΣWLA – FG – MOS
LA – Allowable loads from unregulated sources
TMDL – Total Maximum Daily Load
WLA – Sum of all WWTF Loads and all other regulated sources (includes WLAPSW)
FG – Sum of Future Growth Loads (i.e., Potential Permitted Facilities)
MOS – Margin of Safety
Unregulated sources are generally nonpoint sources and typically enter the impaired segment through distributed, nonspecific locations.
As mentioned previously future growth addresses the requirement to account for future loadings that may occur due to population growth and commensurate changes in community infrastructure and development.

17. Load Duration Curve Example
Flow Duration Curve
To illustrate how these allocations are typically made, I’d like to use a simple example using load duration curves. But, first I feel I should give a brief explanation of load duration curves.
Load duration curves start out as flow duration curves, which with some of you may be familiar. Flow duration curves are simply a frequency distribution of gaged flow values.
Flow values are plotted in with respect to their frequency of occurrence or duration. The values on the y-axis are flow values and the values on the x-axis are frequency percentiles.
The median flow is found at the 50th percentile.

18. Load Duration Curve Example
Flow Duration Curve
Highest
Flow
Mid-range
Lowest
For use in bacteria TMDLs, flow duration curves are often subdivided into flow ranges. It is the practice of the TCEQ’s TMDL program to calculate TMDLs using the median flow value in the highest flow range on the curve.

19. Load Duration Curve Explicit 5% MOS 126 MPN * 0.95 = 120 MPN
Flow duration curves are transformed into load duration curves by multiplying the flow values by the pertinent water quality criterion, in this case the criterion used to protect the primary contact recreation use in fresh water (126 MPN E. coli). Notice that the y-axis now shows units of MPN/day.
If we have bacteria data, we can plot it on the load duration curve using the date of sample collection to pair the flow on the day of collection with the actual bacteria value measured on the same day; multiplying the two yields an instantaneous load that can be plotted on the curve.
We often apply the margin of safety upfront by using a fraction of the criterion (1-MOS * criterion), rather than the actual criterion, to convert the FDC into the LDC.

20. Load Duration Curve Allocation to Runoff (LA + Σ WLAPSW)
Σ WLA + FG
Allocation to Runoff
(LA + Σ WLAPSW)
Allocation to WWTFs
(Σ WLAWWTF + FG)
With Load Duration Curves, the curve itself represents the instream TMDL, so we can think of area under the curve as the allocatable load.
The load from WWTFs is fairly constant under most conditions so it can be represented as a straight horizontal line. Adding an allocation for future growth to the WWTF load allocation leaves only the load attributed to runoff (hatched).
It is this hatched portion of the curve that is apportioned into LA and WLAPSW using the FDAPSW.

21. TMDL Allocations Final TMDLAU
TMDL
WLAWWTF
WLAPSW LA FG
MOS
0666_01
100.0
10.0
16.0
64.0
5.0
Final TMDL
In this example, let’s assume our units are in billion MPN/day Enterococci
WLAWWTF = 10% of total load
FG = Population increase of 50% (5 billion counts)
Explicit MOS = 5%
Runoff load (LA+WLASWP) is 80% of total load
FDAPSW = 20%
This is a table you would typically see in one of our TMDLs, showing an example for AU 0666_01 of TMDL, WLAWWTF, WLASW, LA, FG and MOS with simple round numbers.
Let’s assume our TMDL is an even 100 billion MPN/day…(explain how values are estimated).
New WWTF permit or increased discharge results in shifting allocations from Future growth to WLAWWTF
Changes in areas under MS4 results in shifting allocations between WLAPSW and LA

22. TMDL Implementation Plans (I-Plans)
Designed to satisfy the TMDL regulatory requirements for “reasonable assurance” of implementation
Determines what will be required to manage the loads from all sources, including stormwater
Describe the activities that will be implemented over a specific time period by the stakeholders to improve water quality
I want to talk a little about TMDL Implementation Plans also known as I-Plans:
They are designed to satisfy the TMDL regulatory requirements for “reasonable assurance” of implementation
An I-plan determines what will be required to manage the loads from all sources, including stormwater
They describe the activities that will be implemented over a specific time period by the stakeholders to improve water quality

23. I-Plans (continued)
Developed by stakeholders in the affected watershed with support and guidance from the TCEQ
Collaborative effort involving a wide variety of stakeholders in a TMDL watershed
Citizens, watershed interest groups
State, local, and federal agencies
Regulated organizations
I-Plans are developed by stakeholders in the affected watershed with support and guidance from the TCEQ.
When we talk about stakeholders we are talking about individuals and organizations that:
Live in the watershed or use the resource
Contribute pollutant loadings or impact water quality
Are directly or indirectly effected by water quality problems
Have statutory or regulatory responsibilities linked to water quality
And/or can help develop or implement actions to improve water quality

24. I-Plans (continued) General Strategy for Development
Establish a Coordination Committee
Identify and organize Work Groups
Develop a Water Quality Improvement Plan
Promote Plan to gain support and cooperation in the watershed
Strategy for continuing the effort is also crucial
Stakeholders meet annually to review progress
The stakeholders revise the plan as needed
General strategy:
Establish a coordination committee with balanced representation
Identify and organize workgroups. These workgroups are responsible for identifying and selecting appropriate management measures for addressing the water quality impairment.
Typical workgroups can include:
Education & outreach
Science & technology
Agriculture
Research
Infrastructure & planning
OSSFs
Wastewater Treatment facilities
The activities or measures identified by the workgroups are typically based of feasibility, costs, support and timing. The activities can be implemented in phases
A crucial component of any I-Plan development strategy is planning for sustainability

25. I-Plans (continued)
Establishes requirements for WWTFs that are “consistent” with the TMDL
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 also be affected
An MS4 operator is trying to reduce discharges of pollutants in stormwater to the maximum extent practicable by developing and implementing a stormwater management program (SWMP).
The MS4 stormwater general permit contains language specifying that BMPs and other SW controls included in the SWMP are acceptable in lieu of effluent limitations
The language in our TMDL documents states that, for MS4 permits, the TCEQ typically establishes BMPs, which are a substitute for effluent limitations as allowed by federal rules where numeric effluent limitations are infeasible.
Instead of identifying specific implementation requirements applicable to a stormwater permit, the TCEQ may revise a stormwater permit, require a revised SWMP or Pollution Prevention Plan or other revisions in accordance with an approved I-plan.

26. I-Plans in Texas Area = 25,618 Mi2 Segments = 59 AUs = 413
Map of Texas showing location of TMDL and I-Plan development and implementation watersheds
Area = 25,618 Mi2
Segments = 59
AUs = 413
Not only urban areas but also large portions of rural areas. A significant amount of area in Texas.

27. Typical Storm Water Management Measures found in I-Plans
Structural BMPs
Detention basins, filter strips, infiltration basins, porous pavement, detention ponds, swales
Retrofitting of existing structures, street sweeping, storm drain marking, spill prevention and control programs, etc.
Non-Structural BMPs
LID incentives, spill reporting, surveillance
Public outreach, education, training and recognition programs
Typical storm water management measures found in I-Plans include structural controls, which I’m sure many in this room are familiar with, such as…
But, can they also include nonstructural BMPs such as incentives for Low Impact Development, spill reporting, surveillance, etc., and actions that facilitate access to information, such as public outreach, education, training and recognition programs.
Really, the sky’s the limit, as long as the BMPs or actions are recognized as effective measures to control pollution from regulated stormwater runoff.
Drain cleaning
Video surveys
Sanitary Sewer Overflow (SSO) Initiatives
FOG reduction programs
Sewer system mapping
Illicit discharge detection and elimination programs
Monitoring programs (outfalls, instream, upstream-downstream, etc.)

28. Adaptive Management Make Changes Make Changes Develop Plan
Implement Plan
Implement Plan
Evaluate Plan
Evaluate Plan
I-Plans must be thought of as living documents subject to adaptive management…
Language in our TMDL states that an adaptive management approach is used to address stormwater allocations in TMDLs. This approach encourages the implementation of structural or non-structural controls, implementation of mechanisms to evaluate the performance of the controls, and finally the allowance to make adjustments as necessary to protect water quality

29. Education & Outreach
We see education and outreach as one of our most important tools for stakeholder involvement in I-Plans. Meeting and event attendees often include elected officials and other local decision-makers.
We typically rely on our local partners to identify and recruit stakeholders. Local entities, including institutions of higher education, councils of government, river authorities and non-profits provide education and outreach and assist us by facilitating and organizing public meetings. These groups have provided a variety of workshops and events available to the public, including Watershed Stewards, feral hogs workshops, the Texas Well Owner Network, and the riparian & stream ecosystem workshops. They continue to host these events throughout Texas in addition to one-on-one meetings for stakeholder education and input.

30. Water Quality Educational Events & Exhibits
We are also improving stakeholder participation through water quality educational events and exhibits, sponsored directly by the TCEQ or through one of our local partners. Here’s an example of outreach and education for our youngsters of all ages.

31.
Our website provides a lot of the general information I have presented…

32. As well as detailed information about our program, including the water bodies we have worked on and are currently working on…program figures and stats

33. And, detailed information about each of our TMDL projects, including maps, documents and project summaries

34. For More Information on TMDLs
TCEQ TMDL Program Website:
Roger Miranda
(512)
Here is the web address, but you can also feel free to contact me anytime for information.
And, I’ll be glad to answer any questions you may have right now.