# Introduction to TMDLs with

**Examples from the**

**Chesapeake Bay**

Rich Batiuk

Associate Director for Science

U.S. EPA Region 3

Chesapeake Bay Program Office

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# What is a TMDL?

A calculation of a pollutant load that

assures that, when implemented, an

impaired segment will attain and

maintain all applicable water quality

standards.TMDLDefinition

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# What is a TMDL?

TMDL = WLA + LA + MOS

WLA = Sum of all point sources

LA = Sum of all nonpoint sources including natural

background

MOS = Margin of safety accounting for uncertainty

about the relationship between loads and water

qualityTMDLDefinition

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# TMDL Allocation

Considerations when making allocation

decisions:

– Source of the pollutant (point source or runoff)

– Controllability of the pollutant (i.e., atmospheric)

– Regulatory authority to control pollutant

– Cost of each allocation option

– Certainty of water quality impact in receiving water

– Reasonable assurance that allocation can be met

– Stakeholders objectivesTMDLProcess

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# TMDL Allocation (cont.)

• Each point source with an individual NPDES

permit receives an individual wasteload allocation

(WLA)

• Point sources covered under general permits

may get a gross wasteload allocation (WLA)

• All other sources and background must be

included in the load allocation (LA), which can be

one gross number or subdivided among

individual sources or categories.TMDLProcess

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# TMDL Allocation

Po int Source 1

(WL A)

NPS Source

Category 2

(L A) Explicit

MOS

Re serve

CapacityAllocationExample



# Po int Source 3

(WL A)

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# Listing of Impaired Waters

1. States identify waters not meeting WQS based

on “ all existing and readily available information 

# ”

2. States establish priorities for TMDLs on basis of

the use and severity of problem



# 3. States develop schedule of TMDLs to be

developed within 2 years



# 4. States provide long term plan

– complete

TMDLs 8 to 13 years from first listing



# 5. EPA has 30 days to approve or disapprove list

submitted April of each even year

– If EPA disapproves State list, EPA has 30 days to

develop list for the StateListingProcess

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# Adopt W **ater Quality Standards** 

**Monitor &**  **Assess Wa**  **ters**

**List Impaired & Threatened W aters** 

**Develop T**

**otal Maximum**

**Daily Loads (TMDL)**  

# CW **A Restoration Framework** 

**Implement Point & Nonpoint**

**Source Allocations** 

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# TMDL Implementation

• TMDLs are implemented through other

sections of the Clean Water Act

• Point Sources:

– Permit limits consistent with WLA are enforceable under CWA through National

Pollutant Discharge Elimination System (NPDES)

– Issued by EPA or States w/ delegated authority



# • Nonpoint Sources:

– No federal regulatory enforcement program

– Primarily implemented through State/local NPS

management programs (limited number w/regulatory enforcement)ImplementationStrategies

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# Low to no

**dissolved**

**oxygen in the**

**Bay and tidal**

**rivers every**

**summer**

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# Impact of a Pound of Nitrogen/Phosphorus **on Bay W**  **ater Quality**

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# Relative effectiveness (Riverine * Estuarine Delivery)

0 1 2 3 4 5 6 7 8UpES,MDUpES,DEMidES,MDSusq,MDLowES,MDWsh,MDUpES,PALowES,DESusq,PAPxtB,MDEshVA,VAPotB,DCMidES,DEPotA,DCPotB,MDPotB,VASusq,NYRapB,VAPotA,MDYrkB,VAPotA,VAWsh,PAPotA,WVPotA,PAPxtA,MDJmsB,VARapA,VAYrkA,VAJmsA,VAJmsA,WV 

# Major **Rivers by Jurisdiction**  **Ranked by P**  **ollution Impact on Bay**

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0 5 10 15 20 25 30 35 40 45

**1985 Base**  **2009 Target**  **Tributary Loading**  **Loading Loading**  **E3 Al**  **l**

**Scenario Calibration**  **Scenario Load A**  **Strategy Scenario**  **Scenario Scenario**  **Scenario Forest** 

**342TN 309TN**  **248TN 200TN**  **191TN 190TN**  **179TN 170TN**  **141TN 58TN** 

**24.1TP 19.5TP**  **16.6TP 15.0TP**  **14.4TP 12.7TP**  **12.0TP 11.3TP**  **8.5TP 4.4TP** **N u** **m b** **e r** **o f** **S e** **g m** **e n** **t s** **i n** **D O** **V i** **o l** **a t** **i o** **n** 

# Open W ater Violations

Deep W ater Violations

Deep Channel Violations 

# Dissolved Oxygen Criteria **Attainment**

Basin

- wi de load is

190 N and 12.7 P (MPY)

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www .epa.gov/chesapeakebaytmdl 

# Setting the Pollution **Diet**

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# Setting the Pollution **Diet**

www .epa.gov/chesapeakebaytmdl

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# 8 Watershed Implementation Plan Elements

• Nutrient and Sediment Target Loads

• Current Program Capacity

• Mechanisms to Account for Growth

• Gap Analysis

• Commitment to Fill Gaps: Policies, Rules, Dates for

Key Actions

• Tracking and Reporting Protocols

• Contingencies for Delayed or Incomplete

Implementation

• Detailed Appendix Supporting Bay TMDL Allocations

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# Phase I: 92 Bay **Segments Phase II: Counties** 

2010 201 1

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# Agriculture **and TMDLs**

• Ensures all sources get their share of the

reduction responsibility

• Reasonable assurance puts focus on

regulated point sources

• Has lead to efforts to fully account for and

credit non

- cost shared conservation practices

• Creates the potential for a large marketplace

for nutrient trading

• Provides a measure of certainty for producers

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# Questions & Comments

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