Click here for

DISCLAIMER

Document starts on next page
EPA 

United States 

Environmental Protection 

Agency 

Office of Water 

(WH-553) 

Washington, D.C. 20460 

EPA 440/4-91-001 

April 1991 

Guidance for Water 

Quality-based Decisions: 

The TMDL Process 
Guidance for Water 

Quality-based Decisions: 

The TMDL Process 

Assessment and Watershed Protection Division 

U.S. Environmental Protection Agency 

Washington, D.C. 20460 
This document provides guidance only. It does not establish or affect legal rights or 

obligations. This guidance may be reviewed and revised periodically to reflect 

changes in EPA’s strategy for the implementation of water quality-based controls, to 

include new information, or to clarify and update the text. Decisions in any particular 

case will be made by applying the Clean Water Act and implementing regulations. 

Comments are invited and will be considered in future revisions. Comments or 

inquiries should be directed to : 

Watershed Branch 

Assessment and Watershed Protection Division (WH-553) 

U. S. Environmental Protection Agency 

Washington, D.C. 20460 
FOREWORD 

This document, “Guidance for the Implementation of Water 

Quality-based Decisions: The TMDL Process,” is intended to define 

and clarify the requirements under section 303(d) of the Clean Water 

Act. Its purpose is to help State water quality program managers 

understand the application of total maximum daily loads within the 

water quality-based approach to establish pollution control limits for 

waters not meeting water quality standards. 

Water quality management has become increasingly more 

complicated. Problems such as toxic contaminants, sediments, 

nutrients, and habitat alteration result from a variety of point and 

nonpoint sources. The TMDL process is established under the Clean 

Water Act as the mechanism to address these problems in a 

comprehensive manner in situations where technology-based controls 

are not adequate. 

Through this guidance we hope to reduce the uncertainties 

associated with TMDLs and to establish the TMDL process as an 

effective water quality management tool for both point and nonpoint 

source pollution control. 

Martha G. Prothro, Director 

Office of Water Regulations and Standards 

US Environmental Protection Agency 

Washington, D.C. 
TABLE OF CONTENTS 

Page 

CHAPTER 1 - INTRODUCTION ........................................................... 1 

Purpose and Summary ...................................................................... 

Policies and Principles 

1 

....................................................................... 2 

Clean Water Act Section 303(d) ............................................................... 4 

Water Quality Planning and Management Regulation ............................................. 6 

CHAPTER 2 - THE WATER QUALITY-BASED APPROACH ‘l-0 

POLLUTION CONTROL ....................................................... 9 

Step One: Identification of Water Quality-Limited Waters ........................................ 11 

Step Two: Priority Ranking and Targeting ..................................................... l3 

step Three: TMDL Development ............................................................ 14 

Step Four: Implementation of Control Actions ................................................. 16 

Step Five: Assessment of Water Quality-Based Control Actions ................................... 16 

CHAPTER 3 - DEVELOPMENT AND IMPLEMENTATION OF THE TMDL ..................... 19 

Development of the TMDL .................................................................. 19 

The TMDL objective ............................................................... 19 

The TMDL Process ................................................................. 19 

Selection of Approach ................................................................ 

20 

The Phased Approach ............................................................... 22 

Approval of TMDLs by EPA ......................................................... 23 

Implementation of the TMDL ................................................................ 23 

NPDES Process for Point Sources ..................................................... 23 

State or Local Process for Nonpoint Sources ............................................ 24 

Assessment of the TMDL ................................................................. 25 

CHAPTER 4 - EPA AND STATE RESPONSIBILITIES ......................................... 27 

EPA/State Agreements ...................................................................... 27 

State Responsibilities ....................................................................... 27 

Identification of Water Quality-Limited Waters Still Requiring TMDLs .................... 27 

Identification and Scheduling of Targeted Waterbodies ................................... 29 

TMDL Development ................................................................ 29 

Continuing Planning Process ......................................................... 29 

Water Quality Management Plan ..................................................... 30 

Public Notice and Participation ....................................................... 30 

Reporting ...................................................................... 31 

Other Specific Responsibilities ..................................................... 31 

EPA Responsibilities ....................................................................... 32 

Review of 303 (d) lists ................................................................ 32 

TMDL Review and Approval ...................................................... 32 

Program Audits .................................................................. 33 

Technical Assistance and Training .................................................... 33 

Guidance Documents and Reports .................................................... 33 

EPA Headquarters Responsibilities ................................................... 33 

EPA Regional Responsibilities ..................................................... 33 

ii 
Page 

APPENDIX A- RELATIONSHIP TO OTHER GUIDANCE .................................... 35 

Monitoring Guidance ................................................................ 35 

Cooperative Monitoring/Citizen Volunteer Monitoring Guidance .......................... 35 

Waste and Allocation Technical Guidance .............................................. 36 

Technical Support Document for Water Quality-Based Toxics ..................... Control 36 

Permit Writers Guidance ............................................................ 37 

Nonpoint Source Guidance ........................................................ 37 

APPENDIX B - SUPPORTING PROGRAMS ................................................. 38 

EPA Water Quality Criteria and Standards ............................................. 38 

Section 305(b) -- Water Quality Assessment ............................................ 39 

Section 304(l) - Impaired waters ..................................................... 40 

Section 319 - Nonpoint Source Program ............................................... 40 

Section 314 - Clean Lakes Program ................................................... 41 

Section 320 - National Estuary Program ............................................... 41 

Monitoring Program ................................................................ 41 

Effluent Limitation Guidelines and Standards ........................................... 41 

NPDES Permits and Individual Control Strategies ....................................... 42 

Marine and Estuarine Waters ....................................................... 42 

Groundwater ..................................................................... 43 

CERCLA .......................................................................... 43 

SARA ............................................................................. 44 

APPENDIX C - SCREENING CATEGORIES ................................................. 45 

APPENDIX D - SELECTED TECHNICAL CONSIDERATIONS ................................. 48 

Design Conditions .................................................................. 48 

Mathematical Models ............................................................... 48 

Pollutant Allocation Schemes ....................................................... 51 

Multiple Discharges ................................................................. 51 

Allocation Tradeoffs .............................................................. 52 

Persistent and/or Highly Bioaccumulative Toxic Pollutants ................................ 52 

Use of Two-Number Criteria ......................................................... 52 

Sediment Results ..................................................................... 53 

APPENDIX E- MATHEMATICAL MODEL SUPPORT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54 

APPENDIX F - GENERAL EPA/STATE AGREEMENT OUTLINE FOR 

DEVELOPMENT OF TMDLS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56 

APPENDIX G - CAUSES AND SOURCES OF POLLUTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57 

LIST OF ACRONYMS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58 
CHAPTER 1 - INTRODUCTION AND 

EXECUTIVE SUMMARY 

Purpose and Summary 

The purpose of this guidance document 

is to explain the programmatic elements and 

requirements of the TMDL process as established by section 303(d) of the Clean Water 

Act and by EPA’s Water Quality Planning 

and Management Regulations (40 CFR Part 

130). A TMDL, or total maximum daily load, 

is a tool for implementing State water quality 

standards and is based on the relationship 

between pollution sources and in-stream 

water quality conditions. The TMDL establishes the allowable loadings or other quantifiable parameters for a waterbody and 

thereby provides the basis for States to establish water quality-based controls. These 

controls should provide the pollution reduction necessary for a waterbody to meet water 

quality standards. 

Section 303(d) of the Act establishes the 

TMDL process to provide for more stringent 

water quality-based controls when technology-based controls are inadequate to 

achieve State water quality standards. When 

implemented according to this guidance, the 

TMDL process can broaden the opportunity 

for public participation, expedite water quality-based National Pollutant Discharge 

Elimination System (NPDES) permitting, 

and lead to technically sound and legally 

defensible decisions for attaining and maintaining water quality standards. In addition, 

the TMDL process provides a mechanism 

for integrating the management of both the 

point and nonpoint pollution sources that 

together may contribute to a waterbody’s 

impairment. 

Chapter Two of this guidance document 

provides a description of the TMDL process 

in the context of the water quality-based approach to pollution reductions. This approach includes the identification and 

priority ranking of water quality-limited waters, the targeting and scheduling of high 

priority waters, the development of TMDLs, 

and the implementation of control actions 

that should result in the attainment of water 

quality standards. Assessment for water 

quality standards attainment provides the information needed to identify water qualitylimited waters and for the evaluation of the 

TMDL and control actions. 

The development and implementation 

of the TMDL establishes the link between 

water quality standards assessment and 

water quality-based control actions. The 

third chapter of this document describes how 

a State should proceed with developing 

TMDLS once waters are targeted for action 

and then how to implement them. Special 

consideration is given to such issues as adequacy of data and information, how to consider nonpoint source contributions, and 

when to use a modified approach, called the 

phased approach, that results in a TMDL 

with special requirements. Implementation 

of the TMDL is discussed in terms of the 

mechanisms that are available to reduce 

both point and nonpoint loads. 

The final chapter of this guidance describes the specific roles and responsibilities 

1 
that the States and EPA have in implementing CWA section 303(d). EPA review and 

approval of lists of waters submitted by the 

States, the priority rankings of these waters, 

and the TMDLS are set forth in the Water 

Quality Planning and Management Regulation. This guidance presents a detailed discussion of the submission of lists and 

TMDLs, and the review and approval processes. The States’ responsibility to involve 

the public in the TMDL process is also highlighted in this chapter. The value and importance of public participation is also 

emphasized throughout the document. 

This guidance focuses on the programmatic aspects rather than the technical issues 

of the TMDL process. Numerous technical 

guidance manuals have been developed by 

EPA to assist States in calculating wasteload 

allocations (WLA). A list of these manuals 

can be found in Appendix A along with a 

description of other relevant guidance documents. A brief description of selected technical considerations can be found in 

Appendix D and information about EPA 

supported models can be found in Appendix 

E. The other appendices provide the reader 

with useful and relevant information such as 

descriptions of related water quality programs (Appendix B) and a general outline of 

an EPA/State agreement for TMDL development (Appendix F). 

Policies and Principles 

To achieve the water quality goals of the 

Clean Water Act, EPA’s first objective is to 

ensure that technology-based controls on 

point sources are established and maintained. Where such controls are insufficient 

to attain and maintain water quality standards, water quality-based controls are required. Under the authority of section 

303(d) of the Clean Water Act, EPA expects 

States to develop TMDLs for their water 

quality-limited waters where technologybased effluent limitations or other legally 

2 

required pollution control mechanisms are 

not sufficient or stringent enough to implement the water quality standards applicable 

to such waters. 

More intensive assessments of water 

quality and an evaluation of pollution 

sources should be conducted where water 

quality standard violations occur or where 

indications of declining water quality or habitat loss are observed A TMDL should be 

developed and appropriate control actions 

taken on all pollution sources and follow-up 

monitoring should be conducted to assure 

that water quality standards are met. If follow-up monitoring indicates that water quality standards are not or will not be met, a 

revised TMDL is required. 

Lack of information about certain types 

of pollution problems (for example, those 

associated with nonpoint sources or with certain toxic pollutants) should not be used as a 

reason to delay implementation of water 

quality-based controls. When developed according to a phased approach, the TMDL 

can be used to establish load reductions 

where there is impairment due to nonpoint 

sources or where there is a lack of data or 

adequate modeling. EPA regulations provide that load allocations for nonpoint 

sources may be based on “gross allotments” 

(40 CFR 130.2(g)) depending on the availability of data and appropriate techniques 

for predicting loads. In addition, before approving a TMDL in which some of the load 

reductions are allocated to nonpoint sources 

in lieu of additional load reductions allocated to point sources, there must be specific 

assurances that the nonpoint source reductions will in fact occur. Therefore, this guidance provides that in specific situations, the 

TMDL must include a schedule for the implementation of control mechanisms, monitoring, and assessment of standards 

attainment. If standards are not attained, a 

TMDL revision is required. Data collected 

through monitoring would then be useful in 

revising the TMDL. While this phased ap- 
PRINCIPLES 

Biedd Sobmissioo of L&s. Every two years, States will submit their required 303(d) identification of water 

quality-limited waters still nccdingTMDL6 including apriority ranking of waterbodies to EPA. These lists may 

be included with a State’s bier&l 305(b) report or as a separate report submitted at the same time as the 305(b) 

report. (*pageW 

Priority TMDI.8. Along with the biumial submission of 303(d) lists, States will identify high priority waters 

targeted for TMDL development over the next two years. (See page 29.) 

Approach far TMDL Development. When specific criteria are met, a TMDL with additional specifi~tions for 

monitoring and implementation under the phased approach should be developed to provide for immediate 

pollution reduction and for collection of additional information. (See page 14 and 22.) 

Impluncntath of Controls Based on TMDLS. States will continue to improve and maintain point soura 

controls through WLAs and NPDES permits while implementing and mahhing nonpoint source controls 

through LAS and State or local requirements (see page 23.) 

Nonpdot Source Controls. LAs for nonpoint sources will be accompanied by a description of nonpoiut source 

load reduction goals and the procedure for reviewing and revising nonpoint source controls. Such descriptions 

will be referenced in reviewing TMJJLS for approval (See page 24.) 

lbe Schedolc. TMDLS will be developed on a schedule negotiated with EPA Regional offices. Tie schedules 

for the review of TMDLs will also be negotiated with EPA Regional 05ce5, but will occur within the statutory 

requirement of 30 days. (See pages 29 and 32.) 

Geography Targeting. States should develop TMDLs that account for both point and nonpoint sources on a 

geographically targeted waterbody basis. Geographically targeted waterbodies could include segments, basins, 

and watersheds as defined by the States. (See page 14.) 

‘Ikreatened Good Quality Waters. States are expected to include threatened good quality waters in their 

identifxation and prioritization of waters still needing TMDLs. (See page 12) 

Publk putid~thn. States are expected to eusure appropriate public participation in the TMDL development 

and implementation process. (See page 30.) 

EO~~IIIWO~~ Indicators. States should measure the effectiveness of control adions by monitoring changes 

in ambient water quality or biological conditions. Measuring environmental progress or showing environmental 

results is a critical need and has become a key element in EPA’s strategic planning process. 

preach requires additional monitoring of the 

waterbody to evaluate the effectiveness of 

nonpoint source management measures or 

more stringent effluent limitations, it does 

not delay the establishment of such control 

mechanisms where there is a lack of information. 

As required by the Clean Water Act, 

States are to identify and report to EPA their 

water quality-limited waters. These waters 

are to be identified according to the provisions established in EPA’s Water Quality 

Management and Planning Regulation at 40 

CPR 130.7(b). The identified waters should 

include those impaired due to point and nonpoint sources and may include threatened 

good quality waters. EPA is establishing 

with this guidance that States should submit 

to EPA, in conjunction with the 305(b) water 

quality assessment reports, in April of 1992, 

the list of water quality-limited waters that 

still require TMDLs. Every two years thereafter, a State should update its list of 303(d) 

waters and submit it with the 305(b) report. 

This guidance describes in detail the identification process and the specific information 

that should be submitted to EPA 

3 
As required by the Clean Water Act, 

States are to rank by priority all waters needing TMDLS. Since each State has a unique 

organizational arrangement for the protection of water quality, this guidance does not 

prescribe how a State should set its priorities. 

However, priority ranking should result in 

the identification of targeted waterbodies 

for which immediate TMDL development 

should be undertaken. In the biennial sub 

mission of their updated list of 303(d) waters, 

EPA expects States to identify the waters 

targeted for TMDL development in the 

forthcoming two years. 

Historically, the water quality-based pollution control program has focused on reducing the load of chemical contaminants 

(e.g. nutrients, biochemical oxygen demand, 

metals) to waterbodies. EPA has defined 

the terms load, loading capacity, and load 

allocation in regulations and technical guidance documents so that wasteload allocations can be calculated. Chemical 

contaminant problems will continue to constitute a major portion of pollution control 

efforts and the terms “load” and “load reduction” are used throughout this document. 

However, it is becoming increasingly apparent that in some situations water quality standards - particularly designated uses and 

biocriteria - can only be attained if nonchemical factors such as hydrology, channel 

morphology, and habitat are also addressed. 

EPA recognizes that it is appropriate to use 

the TMDL process to establish control measures for quantifiable non-chemical parameters that are preventing the attainment of 

water quality standards. Control measures, 

in this case, would be developed and implemented to meet a TMDL that addresses 

these parameters in a manner similar to 

chemical loads. As methods are developed 

to address these problems, EPA and the 

States will incorporate them into the TMDL 

process. 

The principles (see page 3) established 

by EPA in this guidance reflect these policies 

4 

and reaffirm the existing regulatory requirements. They are intended to help States 

manage their surface water quality programs 

in a manner consistent with the intent and 

requirements of section 303(d) of the CWA 

and the Water Quality Planning and Management Regulations in 40 CFR 130. These 

principles are discussed throughout this 

guidance. 

t&an Wafer Act Sextin 303(d) 

Section 303(d) of the Act (see next page) 

requires States to identify waters that do not 

or are not expected to meet applicable water 

quality standards with technology-based 

controls alone. Waters impacted by thermal 

discharges are also to be identified. States 

are required to establish a priority ranking 

for these waters, taking into account the pollution severity and designated uses of the 

waters. 

Once the identification and priority 

ranking of water quality-limited waters are 

completed, States are to develop TMDLS at 

a level necessary to achieve the applicable 

State water quality standards. Completed 

TMDLS must allow for seasonal variations 

and a margin of safety that accounts for any 

lack of knowledge concerning the relationship between effluent limitations and water 

quality. 

States are required to submit to EPA the 

titers identified and loads established” for 

review and approval by EPA If disap 

proved, EPA will establish the TMDLs at 

levels necessary to implement the applicable 

water quality standards. For waters that are 

not identified under sections 303(d)(l)(A) 

and (l)(B) as being water quality-limited, 

States are to estimate TMDLS for information purposes. 

Subsections 4(A) and (B) were added to 

CWA section 303(d) with the 1987 amendments in order to ensure consistency with the 

water quality standards process for use clas- 
FEDERAL WATER POLLUTION CONTROL ACT 

Section 303(d) 

(l)(A)~Sratcshall~thoJcwataswithinitrbollndaricsforwhichrhc~limiroaionrnquindbyscction 

3Ol(b)(l)(A)andsection3Ol(b)(l)(B)amnotstrtngentenoughwim@ementanywaterqualirys@ndatd applicable 

w such waters. Thc State shall establish apiarirV rankingforsuch watm, taking info accounlthcsev~oftht 

pollu&andtheuseswbcmadeofsuchwaters. 

(C)EochStcrtcshallcnablihforthcwotasidaujFdin~a~~(l)(A)ofrhirsubsccrioyandinaccadancrwith 

thepriodyr~gthetotalmmrimwn daily&ad,forthosepol&ntswhichtheAdministratoridemif%undersectum 

304(a)(2) as mitabk fbr such calada~ Such &ad shall be established at a level necessary to implement the 

applicablr waterqualitystanda& withswoMIv~~andammgnofs~which~okcrintooccbwuanyIack 

ofknow&dgeconcemingtherelationshipbetweencffluMlimita&nsand waterquality. 

(2) Each State shall submit to theAdmini.stratorfnun tune to tinq with the first such submission not later than one 

hundred and eighty days ajier the date of publication of the )?rst identification of pollutants under section 

304(a)(2)(D), fop his approval the waters iden@ed and the loads established under paragraphs (l)(A), (I)(B), 

(I)(C), and (I)(D) of this subsection Ihe Administrator shall either opptove or d&p-e such identtfiation and 

loadnorlaurthan~daysafrarhcdau~~mirsionIfthcAdminimarovappwcrsuch~and1004 

such State shall incorporate them into its aurotr p&n under subsection (e) of this section If the Administrator 

~~~suchidauiForiovrandroacl,hcJhollnotlara~~dCIyfathCdCltCOfSllCh~ap~~~~ 

suchwaraJinswhStarcandcnablihJuch~fotsuchwarasarhc&~ nuessary w implement the water 

qualrjlsrandardtapplicab&wsudrwataJ~upovtsuch~~~andcstab~~cnrthcStatcshallincovporatc 

them into its cutrent plan under subsection (e) of this section 

(3) For the specific purpose of developing inf~tion, each State shah idcnrjfL all waters within its bour&&s which 

it has not identzw unda paragraph (l)(A) and (I)(B) of this subsection and tstimauforsuchwattrsthetotd 

-dailyloadwithseasonalv- and matgim of safety, fat those pol&mts which the Administrator 

ident@ unda section 304(a)(2) as suitable for such calculation and for thamal dischaqes, at a level that would 

assurepmtution andpqmgation ofa balanced indigenouspoyndation OfFh, shellftsh and wikilife 

(4) LLMIZATIONS ONREVISION OF CEBTMNEFFLUENTLIM7ZATIONS.--- 

(A) STANDABD NOT AlXAINED.-For waters iden@ed under paragraph (I)(A) whar the applicable water 

QualiryJrandardhasnoJyabun~any~~barcdonatosalmmimwndai?,locldorothawarrr 

loodallocaabvrurablirhcdunda~sccnbnmrrybrmtirc4~jf(i)rhcnunulative~~orfallsrrchnvircdcfflucnt 

Iimitations based on such totalmaximum dailyloadorwasteloada&xatumwillassuretheattainment of such wata 

qualiy standard or (ii) the designated use which it not being attained is ronoved in acco&nce with reguhuions 

established unda this section 

(B)STANDARDAlTAINED.--Forwatersidentt$uiunderparagraph (l)(A) wherethequalityofsuch watersequals 

or aceeds levels necessaty w ptxrtect the designatrd use for such waters or othenvise q&d by applicable wata 

qua&y standard, any e@ent limitation based on a total maximum dOi&lOdtWoshaWtlSt~hldt.llhUh 

established unda this section, or any wata quality standard established under this section, or any otherpemtimig 

~zndard may be revised or$v if such revision is subject to and consistent with the ant&gradation poliq estabtlishea 

unda this section 

5 
sification and with the NPDES antibacksliding requirements. 

EPA’s Water Quality Planning and Management Regulation at 40 CPR Part 130 establishes the program and policies that 

implement CWA section 303(d) requirements. Section 130.7 describes the TMDL 

process and the State’s responsibility for 

identifying waters still requiring TMDLs, 

setting priorities and developing TMDLS, 

submitting the waters identified with priority 

rankings and the TMDLS to EPA for approval, and the incorporation of the TMDLS 

into the State’s Water Quality Management 

Plan. 

To implement the program, the regulation establishes the following definitions for 

loading capacity, load allocation, wasteload 

allocation, total maximum daily load, water 

quality-limited segments and water qualitylimited segments still requiring TMDLs. A 

definition for margin of safety (MOS) is also 

provided. 

Loading capacity (LC) - The greatest 

amount of loading that a water can receive 

without violating water quality standards. 

(40 CFR 1302(f)) 

Load allocation (LA) - The portion of a 

receiving water’s loading capacity that is attributed either to one of its existing or future 

nonpoint sources of pollution or to natural 

background sources. Load allocations are 

best estimates of the loading, which may 

range from reasonably accurate estimates to 

gross allotments, depending on the availability of data and appropriate techniques for 

predicting the loading. Wherever possible, 

natural and nonpoint source loads should be 

distinguished. (40 CFR 130.2(g)) 

Wasteload allocation (WLA) -The portion of a receiving water’s loading capacity 

that is allocated to one of its existing or future point sources of polhrtioa WLAs constitute a type of water quality-based effluent 

limitation. (40 CF’R 1302(h)) 

Total maximum daily load (TMDL) - 

The sum of the individual WLAs for point 

sources and LAs for nonpoint sources and 

natural background. If a receiving water has 

only one point source discharger, the TMDL 

is the sum of that point source WLA plus the 

L&i for any nonpoint sources of pollution 

and natural background sources, tributaries, 

or adjacent segments. TMDLS can be expressed in terms of either mass per time, 

toxicity, or other appropriate measure that 

relate to a State’s water quality standard. If 

Best Management Practices (BMPs) or 

other nonpoint source pollution control actions make more stringent load allocations 

practicable, then WLAs can be made less 

stringent. Thus, the TMDLprocess provides 

for nonpoint source control tradeoffs. (40 

CFR 1302(i)) 

In pactice, the terms lXfDL and U2.A 

have at times been incorrectly used interchangeably instead of considering both LA 

and WLA as components of a XUDL. A 

TiUDL, as tefeteced in thir guidance, includes both WUs and LAS, estublirhea’ in 

accordance with EPA ‘s regularionr 

Water quality-limited segments --Those 

water segments that do not or are not expected to meet applicable water quality standards even after the application of 

technology-based effluent limitations required by sections 301(b) and 306 of the Act. 

(40 CPR 130.20’)) Technology-based controls include, but are not limited to, best 

practicable control technology currently 

available (BFT) and secondary treatment. 

Water quality-limited segments still requiring TMDLs -- Segments identified 

through a process established by paragraph 
130.7(b)(l) of EPA’s Water Quality Planning and Management Regulation. Waters 

need TMDLS when certain specified pollution reduction requirements (identified in 

the regulation under subparagraphs 

(b)(l)(i), (ii), and (iii)) are not stringent 

enough to implement water quality standards for such waters. The specified pollution controls include technology-based 

effluent limitations required by sections 

301(b) and 306 of the Clean Water Act and 

other appropriate requirements that can 

provide a more stringent level of treatment 

than federally-required technology-based 

effluent limitations. (40 CFR 130.7(b)( 1)) 

ThFF abcumem contaim the terms 303(d) 

waters and 303(d) kts. 7hese waters (and 

waters on the 303(d) l&s) are those water 

quality-limited segments that still require 

7MDLs as defined by the regulation l?tus, a 

watersegmenthat meets its waterquulitystandam5 afier the implementation of water quulity-based control actions would retain its water 

quality-limited status but would no longer be 

on a State’s 303(d) list of waters still requiring 

EUDLS. 

Margin of Safety (MOS) - A required 

component of the TMDL that accounts for 

the uncertainty about the relationship between the pollutant loads and the quality of 

the receiving waterbody. (CWA section 

303(d)(l)(C)) The MOS is normally incorporated into the conservative assumptions 

used to develop TMDLs (generally within 

the calculations or models) and approved by 

EPA either individually or in State/EPA 

agreements. If the MOS needs to be larger 

than that which is allowed through the conservative assumptions, additional MOS can 

be added as a separate component of the 

TMDL (in this case, quantitatively, a TMDL 

= LC = WLA + LA + MOS). 

7 
CHAPTER 2 - THE WATER QUALITY-BASED APPROACH 

TO POLLUTION CONTROL 

The Water Quality Planning and Management Regulation (40 CFR 130) links a 

number of Clean Water Act sections, including section 303(d), to form the water qualitybased approach to protecting and cleaning 

up the nation’s waters (diagrammed in Figure 1). This chapter describes the overall 

approach for the development of TMDLs 

and subsequent implementation of water 

quality-based point and nonpoint source 

pollution control measures based on water 

quality standards. Other related guidance 

on various aspects of the water quality-based 

approach are described in Appendix A. 

are identified through the development of a 

TMDL under section 303(d). 

The water quality-based approach emphasizes the overall quality of water within a 

waterbody and provides a mechanism 

through which the amount of pollution entering a waterbody is controlled based on the 

intrinsic conditions of that body of water and 

the standards set to protect it. This approach 

begins with the determination of waters not 

meeting (or not expected to meet) water 

quality standards after the implementation 

of technology-based controls (such as BIT 

and secondary treatment). Waters identified through this process are considered 

water quality-limited and must be prioritized. An overall plan to manage the excess 

pollutants in each waterbody can then be 

developed. The necessary limitations on the 

introduction of pollutants to the waterbody 

Previous practices for implementing 

303(d) have focused primarily on point 

sources and wasteload allocations (WLA). 

All water quality-based permit limits are 

based on a WLA. The WLA is either reviewed individually by EPA or where there 

exists a State/EPA technical agreement, is 

developed consistent with that agreement.1 

In recent years nonpoint source contributions to water quality problems have become 

better understood and it is now clear that 

EPA and State implementation of 303(d) 

must encompass nonpoint source pollution 

problems and seek to address problems occurring over large geographic areas. As a 

consequence, this document describes a 

more rigorous process for implementing 

303(d) and reinforces the need to develop 

TMDLs that include load allocations (LA) 

as well as wasteload allocations. 

As shown in Figure 1, the water qualitybased approach contains the following steps: 

1. Identification of water qualitylimited waters still requiring TMDLs. 

2. Priority ranking and targeting. 

3. TMDL development. 

1 USEPA. 1985. Guidance for State Water Monitoring and Wasteload Allocation Program. OW/OWRS, 

EPA 440/4-85-031. Washington, D.C. 
Figure 1 

General Elements of the 

Water Quality-Based Approach 

10 
Identi@ing Waters Still Requiring 

TMDLs: 40 CFR 130.7(b) 

(b)(l) Each State shall identify those :crrz 

segments still requiring WLAsaAs 

within its boundaries for which: 

(i) Technology-based efhent hitations requir&byscctions301(b),306,307,0rother 

sections of the au; 

(ii) More stringent cfZlucat limitations (ichding prohibitions) required by either State 

or local authority prcscned by section 510 

of the AU, or Federal authority (e.g., law, 

regulation, or treaty); aad 

(iii) Other pollution control requiremeats (e.g., 

best management practices) rquired by 

lod, State, or Federal authority 

are not stringent enough to implement any water 

quality standard applicable to such waters. 

4. Implementation of control actions. 

5. Assessment of water quality-based 

control actions. 

Steps 1, 2, and 3 are addressed by the 

CWA in section 303(d). Steps 4 and 5 are 

integral parts of the process and are briefly 

described in this document. 

States are to review and revise water 

quality standards, as necessary, every three 

years and NPDES permits are to be re-evaluated and issued every five years. The water 

quality-based approach links these two processes and is, therefore, an ongoing process 

of evaluation and modification. In addition 

to standards and permits revisions, section 

319(b) nonpoint source (NPS) management 

plans can and should be continually updated 

as well. 

step one: Iih@c~hn of wuter 

Qtdity-limited Waters 

The water 

lution control 1 

uality-based approach to polegins with the identification 

of problem waterbodies. State water quality 

standards form the basis and “yardstick” by 

which States can assess the waterbody status 

and implement needed pollution controls. 

State water quality standards include three 

elements: designated uses for the waterbody, criteria (physical, chemical, and biological) to protect the designated uses, and 

an antidegradation statement. States need 

to identify those waters not meeting any one 

of these components of water quality standards. 

EPA’s Water Quality Planning and Management Regulation establishes the process 

for identifying water quality-limited segments still requiring TMDLS. Waters requireTMDLswhen certainpollutioncontrol 

requirements (see box) are not stringent 

enough to implement water quality standards for such waters. 

The most widely applied water pollution 

controls are the technology-based effluent 

limitations required by section 301(b) and 

306 of the Clean Water Act. In some cases, 

a State or local authority may establish enforceable requirements beyond technologybased controls. Examples of such 

requirements may be those that (1) provide 

more stringent NPDES permit limitations to 

protect a valuable water resource or (2) provide for the management of certain types of 

nonpoint source pollution. 

To exempt a water quality-limited water 

from the TMDL process, the pollution control requirements cited in the regulation 

under 130.7(b)(i),(ii), and (iii) (see box) 

must be established and enforced by Federal, State, or local laws or regulations and 

be stringent enough that, when applied, the 

receiving waterbody will meet water quality 

standards. These requirements must also be 

specifically applicable to the particular water 

quality problem and, if not yet implemented, 

a schedule for the timely implementation of 
such requirements must be established. 

Chapter 4 contains more specific requirements pertain@ to identification of water 

quality-limited waters still requiring TMDLs 

(see p. 27). 

Identification of threatened good quality 

waters is an important part of thrs approach. 

Adequate control of new discharges from 

either point or nonpoint sources should be a 

high priority for States to maintain the existing use or uses of these waterbodies. In the 

identification of threatened waters it is important that the 303(d) process consider the 

water quality standards program to ensure 

that a State’s antidegradation policies as established in State law are followed. 

By identifying threatened good quality 

waters, States take a more proactive, “pollution prevention” a 

management (see & 

preach to water quality 

low). 

Pollution Prevention Advantages 

consistent with 40 CFR 130.7 (c)(l)@) which requircsthatTMDLsbcestablishedforallpollutants 

thatprevcntorafcclqKxtedtoprcvcntwataquality standards from being achieved. 

Encourages States to maintain and protect cxkting 

water quality. 

Easier and less costly in the long term to prevent 

impairments rathcr than retrofit umtrols to clean 

up pollution proMeM. 

Meets EPA objectives to support the State’s mllcuion of data on impaucd or thrcatcncd waters. 

Each State may have different methods 

for identifying and compiling information on 

the status of its waterbodies depending on its 

specific programmatic or cross-programmatic needs and organizational arrangements. Typi 

=!? 

) states utilize both existmg 

information an new data collected from ongoing monitoring programs to assess 

whether water quality standards are being 

met, and to detect trends. 

States assess their waters for a variety of 

purposes, including the targe 

Y 

of cleanup 

activities, assessing the extent 0 contamination at potential Superfund sites, and for 

meeting federally mandated reporting requirements. While the identification of 

water quality-limited waters may appear to 

be a major task for the States, a significant 

amount of this work has already begun or has 

been corn leted under sections 305(b), 

304(1),314 P a),and319(a)oftheCleanWater 

Act as amended in 1987. (Appendix B rovides a summary of these supporting CL A 

Prw=.) 

Section 3!5(b) requires States to prepare 

a water quahty mventoxy every two years to 

document the status of waterbodres that 

have been assessed. Under section 304(l), 

States identified all surface waters adversely 

affected by toxic (65 classes of compounds), 

conventional (such as BOD, total suspended 

solicls, fecal coliform, and oil and grease), 

and nonconventional (such as ammonia, 

chlorine, and iron) pollutants from both 

point and nonpoint sources. Under section 

314(a), States identified a list of publicly 

owned lakes for which uses are known to be 

impaired by point and nonpoint sources. 

Section 319 State Assessment Reports identified waters adversely affected by nonpoint 

sources of pollution. Lists prepared to satisfy re uirements under section 30S(b), 

304(l), %4(a) and 319 should be very useful 

in preparing 303(d) lists. 

Other existing and readily available data 

and information sources should be utilized 

in preparing section 303(d) lists. See, for 

example, Appendix C, which presents 

screening categories similar to those found 

in current regulatiqns. promulgating the 

304(l) requirements. Figure C-l m the Appendix depicts a sample process for identify2 40 CFR DO.10 (d)(6) 

12 
ing 303(d) waters. Other data sources are 

Amended, March 1988. The Toxic Chemical Release Inventory (TRI) developed 

under Title III, Superfund and Reauthonzation Act (SARA) is an important information source as well as any relevant State-run 

database. 

Section 303(d) requires States to identify 

those water quality-limited waters needing 

TMDLs. States should regularly update 

their lists of waters (or the databases which 

store the information to produce the lists) as 

assessments are made and report these lists 

to EPA once every two years. States should 

include, in their biennial 303(d) lists, information on which waterbodies have been 

added or deleted from the list and which 

waterbodies were assessed since the last reporting period. (See page 27 for further details on submission of lists to EPA) 

Step Two: Priority RanRing and 

Targeting 

Once waters needing additional controls 

have been identified, a State prioritizes its 

list of waters using established ranking processes that should consider all water pollution control activities within the State. 

Priority ranking has traditionally been a process defined by the State and may vary in 

complexity and design. A priority ranking 

should enable the State to make efficient use 

of its available resources and meet the objectives of the Clean Water Act. 

The Clean Water Act states that the priority ranking for such waters must take into 

account the severity of the pollution and the 

uses to be made of such waters. Several 

documents (see box) are available from EPA 

to assist States in priority setting. 

Priority Setting Documents 

to NPnpnmtSPutrx; 

Control (OWRS, Jti 1987). 

Betttr (OW and OPPE, August 

1989, EPA 506I2-89~). 

e 

First Edition (OWRS, EPA 440/Stiite!g 

Second Edition (OWRS, EPA 

According to EPA’s State Clean Water 

Strategy document: “Where all water quality 

problems cannot be addressed immediately, 

EPA and the States will, using multi-year 

approaches, set priorities and direct efforts 

and resources to maxim& environmental 

benefits by dealing with the most serious 

water quality problems and the most valuable and threatened resources first.” 

Targeting high priority waters for TMDL 

development should reflect an evaluation of 

the relative value and benefit of waterbodies 

within the State and take into consideration 

the following: 

l Risk to human health and aquatic 

life. 

l Degree of public interest and support. 

l Recreational, economic, and aesthetic importance of a particular 

waterbody. 

l Vulnerability or fragility of a particular waterbody as an aquatic habitat. 

13 
Immediate programmatic needs such 

as wasteload allocations needed for 

permits that are coming up for revisions or for new or expanding discharges, or load allocations for 

needed BMPs. 

Waters and pollution problems identified during the development of the 

section 304(l) long list.” 

Court orders and decisions relating 

to water quality. 

National policies and priorities such 

as those identified in EPA’s Annual 

Operating Guidance. 

States are required to submit their priority rankings to EPA for review. EPA expects 

all waters needing TMDLs to be ranked, 

with “high” priority waters - targeted for 

TMDL development within two years following the listing process - identified. (See 

page 29 for further details on submission of 

priorities to EPA) 

In order to effectively develop and implement TMDLs for all waters identified, 

States should establish multi-year schedules 

that take into consideration the immediate 

TMDL development for targeted waterbodies and the long-range planning for addressing all water quality-limited waters still 

requiring TMDLS. While it would be expected that these schedules would change 

when a State’s priorities change in response 

to “hot spots” or critical situations at any 

given time, a long-range schedule provides 

several advantages to a State (see box). 

Step IVtme: TMDL Development 

For a water qualit@nited water that 

still requires a TMDL, a State must establish 

a TMDL that quantifies pollutant sources 

and allocates allowable loads to the contribAdvantages to Long-range Schedules 

0 En~int~witllthcpermitting 

cyclq the water quality standards revision& 

and other required water quality managcment activith. 

0 Allows for long-term monitoring which may 

be needed to assess control action. 

l Sets consistency in developing lT4DI.s. 

0 Establishcsabasisforscttingovcm.llwater 

quality-priorities 

0 Supports a geographic approach for TMDL 

dcvclopmcaUfortargctcdwaferbodies. 

uting point and nonpoint sources so that the 

water quality standards are attained for that 

waterbody. The development of TMDLS 

should be accomplished by setting priorities, 

considering the geographic area impacted by 

the pollution problem, and, in some cases, 

using a phased approach to establishing control measures based on the TMDL 

The TMDL is developed using one or a 

combination of three technical approaches 

to protect receiving water quality: the chemical specific approach, the whole effluent 

toxicity approach, and the biocriteria/bioassessment approach. The chemical 

specific approach is one where loadings are 

evaluated in terms of the impact on physicalchemical water quality conditions (e.g., dissolved oxygen or toxicant concentrations). 

While an integrated approach that considers 

all three techniques is preferred for the protection of aquatic life, the chemical specific 

approach is usually the one used to address 

loads that affect those water quality standards which protect human health. 

Many water pollution concerns are areawide phenomena that are caused by multiple 

dischargers, multiple pollutants (with poten14 
tial synergistic and additive effects), or nonpoint sources. Atmospheric deposition and 

ground water discharge may also result in 

significant pollutant loadings to surface waters. As a result, EPA recommends that 

States develop TMDLS on a geographical 

basis (e.g., by watershed) in order to efficiently and effectively manage the quality of 

surface waters. 

The TMDL process is a rational method 

for weighing the competing pollution concerns and developing an integrated pollution 

reduction strategy for point and nonpoint 

sources. The TMDL process allows States to 

take a holistic view of their water quality 

problems from the perspective of instream 

conditions. Although States may define a 

waterbody to correspond with their current 

programs, it is expected that States will consider the extent of pollution problems and 

sources when defining the geographic area 

for developing TMDLs. In general, the geographical approach for TMDL development 

supports sound environmental management 

and efficient use of limited water quality 

program resources. In cases where TMDLs 

are developed on watershed levels, States 

should consider modi@@ permitting cycles 

so that all permits in a given watershed expire at the same time. 

For traditional water pollution problems, such as dissolved oxygen depletion and 

nutrient enrichment, there are well validated 

models that can predict effects with known 

levels of uncertainty. This is not true for such 

non-traditional pollution problems as urban 

stormwater runoff and pollutants that involve sediment and bioaccumulative pathways. Predictive modeling for these 

problems therefore uses conservative assumptions, but in many cases the degree of 

certainty cannot be well quantified until 

3 4ocFR Em(g). 

more data becomes available to develop sensitivity analyses and model comparisons. 

For TMDLS involving these non-traditional 

problems, the margins of safety should be 

increased and additional monitoring required to verify attainment of water quality 

standards and provide data needed to recalculate the TMDL, if necessary. 

EPA regulations provide that load allocations for nonpoint sources and/or natural 

background “are best estimates of the loading which may range from reasonably sccurate estimates to gross allotments... A 

phased approach to developing ‘IMDLS may 

be appropriate where estimates are based on 

limited information. The phased approach 

is aTMDL that includes monitoring requirements and a schedule for re-assessing TMDL 

allocations to ensure attainment of water 

quality standards. Uncertainties that cannot 

be quantified may also exist for certain pollutants discharged primarily by point 

sources. In such situations a large margin of 

safety and follow-up monitoring is appropriate. 

Where nonpoint source controls are involved, the phased approach is also necessary. Under the CWA, the only federally 

enforceable controls are those for point 

sources through the NPDES permitting process. In order to allocate loads among both 

nonpoint and point sources, there must be 

reasonable assurances that nonpoint source 

reduction will in fact be achieved. Where 

there are not reasonable assurances, under 

the CWA, the entire load reduction must be 

assigned to point sources. With the phased 

approach, the TMDL includes a description 

of the implementation mechanisms and the 

schedule for the implementation of nonpoint source control measures. 
By pursuing the phased approach where 

applicable, a State can move forward to implement water quality-based control measures and adopt an explicit schedule for 

implementation and assessment. States can 

also use the phased approach to address a 

greater number of waterbodies including 

threatened waters or watersheds which 

would otherwise not be managed. Specific 

requirements relating to the phased ap 

preach are discussed in Chapter 3. 

Step Four: Imp~mentation of Coned 

Actins 

Once a TMDL or a phased TMDL has 

been established for a waterbody (or watershed) and the appropriate source loads developed, implementation of control actions 

should proceed. The State or EPA is responsible for implementation, the first step being 

to update the water quality management 

plan. Next, point and nonpoint source controls should be implemented to meet 

wasteload allocations and load allocations, 

respectively. Various pollution allocation 

schemes (i.e., determination of allowable 

pollution among different pollution sources 

in the same waterbody) can be employed by 

States to optimize alternative point and nonpoint source management strategies. 

The NPDES permitting process is used 

to limit effluent from point sources. Chapter 

3 provides a more complete description of 

the NPDES process and how it fits into the 

water quality-based approach to permitting. 

Construction decisions regarding publicly 

owned treatment works (PUIWs) and advanced treatment facilities must also be 

based on the most stringent of technologybased or water quality-based limitations. 

These decisions should be coordinated so 

that the facility plan for the discharge is consistent with the limitations in the permit. 

In the case of nonpoint sources, both 

State and local laws may authorize the implementation of nonpoint source controls 

such as the installation of Best Management 

Practices (BMPs). Section 319 State management programs can be a useful tool to 

implement nonpoint source control measures and ensure improved water quality. 

Many BMPs, however, may be implemented 

even where regulatory programs do not exist. 

In such cases, a State needs to document the 

coordination which may be necessary among 

State and local agencies, landowners, operators, and managers and then evaluate BMP 

implementation, maintenance, and overall 

effectiveness to ensure that load allocations 

are achieved. Chapter 3 dkcusses some of 

the technical issues associated with implementation of nonpoint source control 

measures. 

Step Five: Assessment of W&r 

Qualify-Based Control 

Actions 

Throughout the previous four steps, 

monitoring is a crucial element of water 

quality-based decision making. In this step, 

monitoring provides data for an independent evaluation of whether the TMDL and 

control actions that are based on the TMDL 

protect or improve the environment and are 

sufficient to meet changing waterbody protection requirements such as revised water 

quality standards or changing pollution 

sources (e.g., urbanization). 

Monitoring programs often begin with 

baseline monitoring. Such monitoring 

should not be regarded as a prerequisite to 

implementing control measures for a waterbody. If monitoring has not yet begun, control measures and monitoring should be 

implemented simultaneously to assure that 

pollution abatement activities are not delayed. 

In the case of point sources, assessments 

are facilitated in that dischargers are required to provide reports on compliance 

16 
with NPDES permit limits. In some instances, dischargers may also be required in 

the permit to assess impact of their discharge 

on the receiving water. A monitoring requirement can be put into the permit as a 

special condition as long as the information 

is collected for purposes of writing a permit 

limit. States are also encouraged to use innovative monitoring programs (e.g., cooperative mo 

J 

itoring and volunteer 

monito * ) to provide for adequate point 

and nonpoint source monitoring coverage. 

States should also ensure that effective 

monitoring programs are in place for evaluating nonpoint source control measures. 

EPA recognizes monitoring as a high priority 

activity in a State? nonpoint source management program. To facilitate the implementation and evaluation of NPS 

States should consult current guid4 USEPA. 1984. PIarm& and Manag& Cooperative Monitoring Projects. OWiOWRS. EPA 

440/4-84418. Washingto& DC. 

5 USEPA. 1990. Vduntccr Water Monitoring A Guide for State Managers. OW, EPA 440/4-90410. 

Washington, D.C. 

6 55 FR 35265 August 28,199O. 

7 USEPA. February, 1988. Draft Nonpoint Source Monitoring and Evaluation Guide. OW/NPS Branch. 

Washington, D.C. 

8 USEPA. September 19,l989. Nonpoint Source Monitoring and Reporting Requirements for Watershed 

Implementation Grants. OW/NPS Branch. Washington, D.C. 

17 
CHAPTER 3 - DEVELOPMENT AND IMPLEMENTATION 

OF THE TMDL 

Development of the TMDL 

The TMDL process is an important element of the water quality-based approach. It 

links the development and implementation 

of control actions to the attainment of water 

quality standards. This chapter expands the 

discussion introduced in Chapter 2 on how 

to develop TMDLs and implement controls 

for water quality-limited waters. Appendix 

D and E provide supporting information on 

some important technical considerations 

and EPA supported models for TMDL development. 

The TMDL Process 

The TMDL Objective 

As stated in 40 CFR 131.2, “[water quality] standards serve the dual purposes of establishing the water quality goals for a 

specific waterbody and serve as the regulatory basis for the establishment of waterquality-based treatment controls and 

strategies beyond the technology-based levels of treatment required by section 301(b) 

and 306 of the Act.” Standards also contain 

antidegradation provisions to prevent the 

degradation of existing water quality. 

The objective of a TMDL is to allocate 

allowable loads among different pollutant 

sources so that the appropriate control actions can be taken and water quality standards achieved. The TMDL provides an 

estimate of pollutant loadings from all 

sources and predicts the resulting pollutant 

concentrations. The TMDL determines the 

allowable loads and provides the basis for 

establishing or modifying controls on pollutant sources. 

The total pollutant load to a waterbody is 

derived from point, nonpoint, and background sources. Pollutant loads may be 

transported into waterbodies by direct discharge, overland flow, ground water, or atmospheric deposition. The TMDL concept 

has successfully been applied to develop 

wasteload allocations for point source discharges in low flow situations where nonpoint sources are not a concern. TMDLs can 

and should be used, however, to consider the 

effect of all activities or processes that cause 

or contribute to the water quality-limited 

conditions of a waterbody. Activities may 

relate to thermal changes, flow changes, sedimentation, and other impacts on the aquatic 

environment. Control measures to implement TMDLs, therefore, are not limited to 

NPDES authorities but should also be based 

on State and local authorities and actions to 

reduce nonpoint source pollution 

An example of how to apply such a 

TMDL might be in the control of excess 

sediment which causes loss of a beneficial 

use of a waterbody. If standards, established 

to protect against the loss of a beneficial use 

(e.g., fish spawning), are not met and, if the 

process causing the problem (i.e., excess sedimentation) can be quantified, then it may be 

appropriate to use the TMDL process to 

assess the adverse impacts and potentially 

set controls on the problem activity. In this 

19 
example, the activity might be urban development for which effective controls can be 

implemented to reduce sediment loading to 

the impacted waterbody. 

The TMDL process distributes portions 

of the waterbody's assimilative capacity to 

various pollution sources - including natural 

background sources and a margin of safety - 

so that the waterbody achieves its water quality standards. The analyst may use predictive 

modeling procedures to evaluate alternative 

pollution allocation schemes in the same 

waterbody. By optimizing alternative point 

and nonpoint source control strategies, the 

cost effectiveness and pollution reduction 

benefits of allocation tradeoffs may be evaluated (see Appendix D). The approach normally used to develop a TMDL for a 

particular waterbody or watershed consists 

of five activities (see box). 

TMDL Development Activities 

• 

• 

• 

• 

• 

Selection of the pollutant to consider. 

Estimation of the waterbody assimilative capacity. 

Estimation of the pollution from all sources 

to the waterbody. 

Predictive analysis of pollution in the waterbody and determination of total allowable 

pollution load. 

Allocation (with a margin of safety) of the 

allowing pollution among the different pollution sources in a manner that water quality 

standards are achieved. 

In developing a TMDL it is important to 

keep in mind certain constraints on the WLA 

portion that are imposed by antibacksliding 

regulatory provisions. The WLA will normally result in new or more stringent water 

quality-based limits than those contained in 

a previously issued permit. In a limited number of cases, however, it is conceivable that 

less stringent water quality-based limits 

could result. In these cases, permit limits 

must conform to the antibacksliding provisions contained in section 402(o) of the CWA. 

Selection of Approach 

Figure 2 illustrates the critical decisions 

and the appropriate steps in the TMDL process for developing load allocations and implementing and evaluating control actions. 

In some cases, as illustrated by the left side 

of the diagram, TMDL development can be 

straight-forward and relatively simple. In 

other cases, as depicted by the right side of 

the diagram, a phased approach may be 

more appropriate. Regardless of which path 

is followed, the allocation of loads and establishment of control actions should ensure 

that all water quality-limited waters will 

meet their standards. 

Once a waterbody is selected for action, 

an analyst must decide if the available data 

and information about the sources, fate, and 

transport of the pollutant to be controlled is 

adequate. The level of effort and scientific 

knowledge needed to acquire adequate data 

and perform meaningful predictive analyses 

is often a function of the pollutant source, 

pollutant characteristics, and the geographical scale of the pollution problem. As described in Chapter 2, modeling the fate and 

transport of conventional pollutants (e.g. 

biochemical oxygen demand) and point 

source contributions is better developed 

than modeling for non-traditional pollution 

problems. For certain non-traditional problems, if there are not adequate data and 

predictive tools to characterize and analyze 

the pollution problem with a known level of 

uncertainty, a phased approach may be necessaryThe phased approach is required when 

the TMDL involves both point and nonpoint 

20 
Rgura 2 D8vvt of TMWS for Tug8t8d W*tubodo8 

IdontJfy 303(d) Tar@etod Watorbody 

lord roductbm? 

o*vdop TMDL hclu&g: 

l WLA8 for PS 

l LA8 for NPS 8nd B8tkglourd 

SOurC88 

l M8rfJifl Of 88f l ty 

. 

oovolop TMDL lndudh~ 

R8~OmOnt8 

. WLA8 for PS which 

- mt8h l titbfj tilllit Or 

.8t8bi&h l3.W mt8 

l ~8for~SWhkh 

- M8hbh or 

NPS control8 TiliEEPW 

. hrf#fb Of uf8ty 

form 

l h8t8ll8tlon 8nd l v8k8tbn 

of NPS control8 

.D8t8 CdkctiOfl 

. wQ8 888.8-t 

l Addltloml modolhg If naodad 

n of Schq&& 

I 

I 

Approval 

by EPA 

Lngkmmt Control. 8nd Comgkt. RoqUrod D8t8 colkction 

0 m p8rl’dt8 fOr #bOht 8-C. COntrOh 

0 8t8tO ot iOCti vOCO88.8 fOr mt 8-C. COntrdr 

l Addltb~Imonltuhg 

l Fhd C8l&dONl Of mOdd8 

WQS8 not rchioved of W&or QuaMyt W088 8chkv.d 

R8mOVO W8terbOdy from 303(d) Ll8t 
sources and the point source WLA is based 

on a IA for which nonpoint source controls 

need to be implemented. There must be 

assurances that nonpoint source control 

measures will achieve expected load reductions in order to allocate a wasteload to a 

point source with a TMDL that also allocates 

expected nonpoint source load reductions. 

In this case, a phased approach is required 

because the TMDL that is developed has 

additional requirements that provide these 

assurances. 

Despite the additional requirements of 

the phased approach, States may actually 

prefer it because the additional data collected can be used to verify expected load 

reductions, evaluate effectiveness of control 

measures, and ultimately determine whether 

a Th4DL needs to be revised. 

The Phased Approach 

Under the phased approach, the TMDL 

has LAs and WLAs calculated with margins 

of safety to meet water quality standards. 

The allocations are based onestimateswhich 

use available data and information, but monitoring for collection of new data is required. 

The phased approach provides for further 

pollution reduction without waiting for new 

data collection and analysis. The margin of 

safety developed for the TMDL under the 

phased approach should reflect the adequacy of data and the degree of uncertainty 

about the relationship between load allocations and receiving water quality. 

The Th4DL under the phased approach, 

includes (1) WLAs that confirm existing limits or would lead to new limits for point 

sources and (2) IAs that confirm existing 

controls or include implementing new controls for nonpoint sources. This TMDL requires additional data to be collected to 

determine if the load reductions required by 

the TMDL lead to attainment of water quality standards. Data collection may also be 

required to more accurately determine as22 

similative capacities and pollution allocatiOIlS. 

In addition to the allocations for point 

and nonpoint sources, a TMDL under the 

phased approach will establish the schedule 

or timetable for the installation and evaluation of point and nonpoint source control 

measures, data collection, the assessment for 

water quality standards attainment, and, if 

needed, additional predictive modeling. 

The scheduling with this approach should be 

developed to coordinate all the various activities (permitting, monitoring modeling 

etc.) and involve all appropriate local authorities and State and Federal agencies. 

The schedule for the installation and implementation of control measures and their 

subsequent evaluations will include descriptions of the types of controls, the expected 

pollutant reductions, and the time frame 

within which water quality standards will be 

met and controls re-evaluated. 

Where no monitoring program exists, or 

where additional assessments are needed, it 

is necessary for States to design and implement a monitoring plan The objectives of 

the monitoring program should include assessment of water quality standards attainment, verification of pollution source 

allocations, calibration or modification of selected models, calculation of dilutions and 

pollutant mass balances, and evaluation of 

point and nonpoint source control effectiveness. In their monitoring programs, States 

should include a description of data collection methodologies and quality assurance/quality control procedures, a review of 

current discharger monitoring reports, and 

be integrated with volunteer and cooperative monitoring programs where possible. If 

properly designed and implemented, the 

monitoring program will result in a sufficient 

data base for assessment of water quality 

standard attainment and additional predictive modeling if necessary. 
Approval of TMDLs by EPA 

TMDLS developed for all water qualitylimited waters are submitted to EPA for review and approval. States are encouraged to 

coordinate with EPAprior to formal submission of their Th4DLs. Chapter 4 explains 

EPA and State responsibilities for the review 

and approval process. 

Implementation of the TMDL 

After identifying the necessary pollutant 

load reductions through the development of 

TMDLs and after approval by EPA, State 

water quality management plans should be 

updated and control measures implemented. 7’his section provides a brief review of point and nonpoint source control 

implementation. Additional guidance is 

available and is referenced throughout the 

remainder of this chapter. 

NPDES Pnxess for Point Somes 

Both technology-based and water quality-based controls are implemented through 

the National Pollutant Discharge Elimination System (NPDES) permitting process. 

Permit limits based on TMDLs are called 

water quality-based limits. 

Wasteload allocations establish the level 

of effluent quality necessary to protect water 

quality in the receiving water and ensure 

attainment of water quality standards. Once 

allowable loadings have been developed 

through WLAs for specific pollution 

sources, limits are incorporated into NPDES 

permits. It is important to consider how the 

WLA addresses variability in effluent quality. On the one hand, allocations for nutrients or bioaccumulative pollutants could be 

expressed as the required average effluent 

quality because the total loading of these 

pollutants is of concern. On the other hand, 

an allocation for toxic pollutants should be 

expressed as a shorter-term requirement because the concentration of these pollutants 

is typi 9 y of more concern than the total 

loading. 

As a result of the 1987 Amendments to 

the Act, Individual Control Strategies (ICSs) 

were established under section 304(1)( 1) for 

certain point source discharges of priority 

toxic pollutants. ICSs consist of NPDES permit limits and schedules for achieving such 

limits, along with documentation showing 

that the control measures selected are appropriate and adequate (i.e., fact sheets including information on how water 

quality-based limits were developed, such as 

total maximum daily loads and wasteload 

allocations). Point sources with approved 

ICSs are to be in compliance with those ICSs 

as soon as possible or in no case later than 

three years from the establishment of the 

ICS (typically by 1992 or 1993). 

The Clean Water Act (and corresponding State statutes) authorizes imposition of 

monitoring and data collection requirements on the owner or operator of a point 

source discharge. Requirements may include ambient and biological assessments, 

toxicity reduction evaluations, in-plant monitoring, etc. Needed data collection may be 

initiated through a direct request under Section 308 if there is a reasonable need for the 

information for EPA to carry out the objectives of the Clean Water Act The request 

must also meet the Paperwork Reduction 

Act requirements. Information may also be 

9 The reader is referred to the Permit Writer’s Guide to Water QuaIity-based Permitting for Toxic 

Pollutants (July, 1987) and the Technical Support Document for Water Quality-based Toxks Control 

(1985) for additional information oo deriving actual permit limits 

23 
Examples of Best Management Practices 

AGRICULTURE 

Animal waste management 

corlscrvation tillage 

contourfiuming 

coIltour strip cropping 

Cover crops 

Crop rotation 

Fertilizer management 

Integrated pest management 

Livestock exclusion 

R 

?I 

e and pasture management 

Sod- ased rotations 

Terraces 

CON!3TRUCl’ION 

Disturbed area limits 

Nonve etative soil stabilization 

Runo f! detention/retention 

Surface roughening 

URBAN 

Flood storage 

Porous pavements 

Runoff detention/retention 

Street cleaning 

SILVICULTURE 

Ground cover maintenance 

Limiting disturbed areas 

Log removal techniques 

Pesticide/herbicide management 

Proper handling of haul roads 

Removal of debris 

Riparian zone management 

Road and skid trial management 

MINING 

Block-cut or haul-back 

Underdrains 

Water diversion 

MULTICATEGORY 

Buffer strips 

Detention/sedimentation basins 

Devices to encourage infiltration 

Grassed watenvay 

Interception/diversion 

Material ground cover 

Sediment traps 

Streamside management zones 

Vegetative stabilization/mulching 

collected through permit reporting requirements, or an administrative order. These 

authorities can be used to collect data from 

point sources when developing or assessing 

the effectiveness of a TMDL 

Permit requirements for data collection 

should be established when longer term data 

(e.g., for several seasons) are needed. The 

permit should include a statement that the 

permit can be modified or revoked and reissued if the data indicate an exceedance of 

State water quality standards. 

State or Local Bvcess for Nonpoht Sources 

In addition to permits for point sources, 

nonpoint source controls may be established 

by implementing Best Management Practices (BMPs) so that surf& water quality 

objectives are met. These controls should be 

based on LAs developed using the TMDL 

process. When establishing permits for 

point sources in the watershed, the record 

should show that in the case of any credit for 

future nonpoint source reductions, (1) there 

is reasonable assurance that nonpoint source 

controls will be implemented and maintained or (2) that nonpoint source reductions 

are demonstrated through an effective monitoring program. Assurances may include 

the application or utilization of local ordinances, grant conditions, or other enforcement authorities. For example, it may be 

appropriate to provide that a permit may be 

reopened for a WIA which requires more 

stringent limits because attainment of non24 
point source load allocation was not demonstrated. 

In order to fully address waterbodies that 

are impaired or threatened by nonpoint 

source pollution, States should implement 

their nonpoint source management programs and ensure adoption of control measures (best management practices) by all 

contributors of nonpoint source pollution in 

those watersheds. Example BMPs are listed 

on the following page. State nonpoint 

source management programs may include, 

as appropriate, nonregulatory or regulatory 

programs for enforcement, technical assistance, financial assistance, education, training, technology transfer, and demonstration 

projects. 

It is difficult to ensure, a prioi that implementing nonpoint source controls will 

achieve expected load reductions. Nonpoint 

source control measures may fail to achieve 

projected pollution or chemical load reductions due to inadequate selection of BMPs, 

inadequate design or implementation, or 

lack of full participation by all co~tibuting 

sources of nonpoint pollution. States 

should describe nonpoint source load reductions and establish a procedure for reviewing 

and revising BMPs in TMDL documentation. The key objective for documenting 

load reduction goals and review procedures 

is to establish a rational procedure for sitespecific evaluation of waterbodies with significant nonpoint source pollution loads. 

States should consult additional nonpoint 

source guidance for assistance in developing 

appropriaff fs onitoring and evaluation ap 

proaches. 

Assessment of the TMDL 

Once control measures have been implemented, the impaired waters should be 

assessed to determine if water quality standards have been attained or are no longer 

threatened. The monitoring program used 

to gather the data for this assessment should 

be designed based on the specific pollution 

problems or sources. For example, past experience has shown that several years of data 

are necessary from agricultural nonpoint 

source watershed projects to detect trends 

(i.e., improvements) in water quality. As a 

result, long term monitoring efforts must be 

consistent over time in order to develop a 

data base adequate for analysis of control 

actions. 

As shown in Figure 2, a TMDL that allocates loads and wasteloads to meet water 

quality standards must be established. If the 

waterbody does achieve the applicable State 

water quality standards, the waterbody may 

be removed from the 303(d) list of waters 

still needing TMDLS. If the water quality 

standards are not met, the TMDL and allocations of load and wasteloads must be modified. This modification should be based on 

the additional data and information gathered as required by the phased approach for 

developing a TMDL, where appropriate, as 

part of routine monitoring activities, and 

when assessing the waterbody for water 

quality standards attainment. 

10 USEPA. July, 1987. Setting Priorities The Key to Nonpoint Source Control. OW/OWRS, EPA. 

Washington, D.C. 

11 USEPA. February, 1988. Draft Nonpoint Source Monitoring and Evaluation Guide. OW/NP!5 Branch, 

Washington, D.C. 

12 USEPA. September 19.1989. Nonpoint Source Monitoring and Reporting Requirements for Watershed 

Implementation Grants. OW/NPS Branch, Washington, DC. 

25 
CHAPTER 4 - EPA AND STATE RESPONSIBILITIES 

Effective implementation of water quality-based controls requires an integrated and 

cooperative partnership between EPA and 

the States. The main responsibility for water 

quality management resides with the States 

in the implementation of water quality standards, the administration of the NPDES program (where the State has received EPA 

approval to do so), and the management of 

nonpoint sources of pollution. When the 

authority to implement nonpoint source 

control measures. is at the local level, interagency and intergovernmental coordination 

is especially important. The State should 

take the lead in facilitating and encouraging 

the cooperation of local authorities. EPA is 

responsible for ensuring that the Clean 

Water Act requirements are met through the 

enactment and enforcement of regulations, 

issuing program guidance, and providing 

technical assistance. The partnership developed between States and EPA should be 

tailored to meet individual State needs while 

also meeting the requirements of the Clean 

Water Act. This chapter describes specific 

State and EPA responsibilities in the partnership. 

EPA/State Agreements 

EPA and the State should agree on the 

process to develop TMDLs and this process 

should be consistent with EPA technical 

guidance documents unless deviation from 

the guidance is technically justified. An 

agreement should be written which describes technical and administrative procedures (i.e., how background data are applied, 

how and which models are to be used, how 

TMDLs are developed, how loads should be 

allocated, etc.). (See Appendix F for a general EPA/State Agreement outline.) This 

agreement reduces the administrative burden of the EPA review and approval process 

(see "TMDL Review and Approval,” p. 30). 

State Responsibilities 

Identification of Water Quality-Limited Waters Still Requiring TMDLs 

According to section 303(d) of the Clean 

Water Act and EPA water quality planning 

and management regulations, States are required to identify waters that do not meet or 

are not expected to meet water quality standards even after technology-based or other 

required controls are in place. The 

waterbodies are considered water qualitylimited and require TMDLs. 

When a State reports its list of 303(d) 

waters, it is important that this list contain 

only those water quality-limited waters that 

still require TMDLs. Some water qualitylimited waters may already have had sufficient controls established for them and 

currently meet water quality standards. 

These should not be on the list. In addition, 

the EPA regulations (40 CFR 130.7(b)) recognize the applicability of other appropriate 

pollution control requirements that can provide a more stringent level of control than 

technology-based effluent limitations. 

When not listing a water quality-limited 

water a State must show that the controls 

specified by 40 CFR 130.7(b) (see p. 11) are 

enforceable, specific to the pollution problems, and stringent enough to meet water 

27 
quality standards. If the controls are not yet 

implemented, a State must provide a schedule for timely implementation. 

The waters identified should be reported 

to EPA in the 305(b) water quality assessment reports due April 1 every even year. If 

a State prefers, the 303(d) list of waters can 

be submitted separately at the same time. 

While initially it may be convenient to build 

upon the reporting processes described in 

Chapter 2, the 303(d) list should be updated 

to reflect the latest monitoring and assessment data available. 

To facilitate the reporting of 303(d) waters, the current section 305(b) Waterbody 

System (WBS), a tool used for reporting 

305(b) information, contains fields already 

designated for this identification. The WBS 

provides a geographically based framework 

for entering, documenting, and reporting information on the quality of individual 

waterbodies as they are defined by each 

State. The primary function of the WBS is to 

document water quality 

f 

assessments and the 

water quality status o waterbodies, including causes and sources of use impairment. 

As a convenience to the States, the WBS has 

been modified and will continue to be updated to include data fields on whether 

TMDLs are still needed or are in place. The 

WBS will also provide information to EPA 

to assist in tracing the development of 

TMDLs and overall program implementation. 

Identification of Causes and Sources of 

Pollution - When identifying the 303(d) waters, the causes of the impairment also 

should be identified for each segment listed. 

The Waterbody System has two separate 

fields that provide further information on a 

particular water segment: “nonattainment 

causes” and “nonattainment sources.” The 

“cause” field consists of a list of constituents 

or conditions that are causing nonattainment 

of water quality standards by a waterbody. 

The Waterbody System’s Users Guide (third 

edition, version 20) contains 23 standard 

causes (see Appendix G) and includes such 

parameters or categories as pesticides, metals, ammonia, and pathogens. States may 

28 

develop their own user-defined codes by 

specifying additional codes under each standard cause. 

Similarly, a field exists in the Waterbody 

System for identifying the sources of the pollutants or conditions that are listed under 

causes for the nonattainment of uses in the 

waterbody. Twelve general source categories are identified (see Appendix G) and 

include such things as industrial point 

sources, municipal point sources, combined 

sewer overflow, agriculture, and silviculture. 

The User’s Guide also identifies 45 subcategories. Again the States may develop 

their own subcategories to describe causes of 

impairment of each water segment identified with this system States should consult 

with the Guidelines for the Preparation of 

the 305(b) Report (to be issue d every odd 

numbered year) and the Waterbody System 

User’s Guide for guidance in developing and 

formatting their information 

Documentation and Rationale for Listing - Along with the list of 303(d) waters 

submitted to EPA, adequate documentation 

to support the listing of waters should be 

submitted. States have a number of readily 

available sources of data and information to 

use when compiling their lists (see pages 12 

and 13). These sources, listed in Appendix 

C, should be used by States to develop their 

lists of 303(d) waters. However, additional 

information may be required under certain 

circumstances. 

Documentation for listing should also 

provide a description of the methodologies 

used to develop the list, a description of the 

data and information used to identify water 

quality-limited waters, and a rationale for 

any decision to not use any one of the categories listed in Appendix C. It is not expected that each and every waterbody listed 

by State a be accompanied by the detailed 

documentation as described. 

Adequate public participation should be 

a part of the listing process to make sure all 

water quality-limited waters are identified. 

This will support the State in defending its 

list of such waters should the need to do so 
arise, since, in its oversight responsibilities, 

EPA reserves the right to ask for additional 

information re arding the State’s decision to 

not list parti cuf ar waterbodies. 

Identijication and Scheduling of Targeted 

Waterbodies 

Targeted waterbodies scheduled for 

TMDL development over the next two years 

are to be identified and reported along with 

the 303(d) list of waters that are submitted 

during the 305(b) reporting process. These 

high priority TMDLs are to be based on 

State develo 

severity of tli 

ed priorities that consider the 

e impact and the uses of the 

water along with the other considerations 

described in Chapter 2. State submissions 

which include the identification of 303(d) 

targeted waters are subject to review and 

approval or disapproval by EPA EPA will 

expect the States to include 

tion in the development o P 

ublic participathe list of h@ 

priority targeted waterbodies. Tar eting 

waterbodies for control action shoul d be a 

key component of a State’s water quality 

management and plannin programs. Waters that are identified in i! tate annual work 

plans will be compared to the targeted 

waterbodies and will be considered by EPA 

during its review and approval of the annual 

work plans. 

7MDL Development 

Each State develops TMDLS for its water 

%4& 

uali -limited waters. The procedure for 

roval 

ure 3. T 

by EPA is depicted in Figtates should use EPA’s technical 

support document and WLA technical guidance series (see Appendix A) when developing TMDLS. Alternative approaches can be 

used if they are technically defensible and 

approved by EPA 

For their TMDL submissions, States 

should include the proposed TMDLs, 

WLAs, LA, and the supporting information 

that the Region will need to evaluate the 

State’s water quality analysis and determine 

whether to a prove or disapprove the submitted TMD E . Regions and States should 

reach an agreement on the specific information needed prior to their submission. For a 

T’MDL developed under the phased approach, States should also submit to EPA a 

description of the controls to be established, 

the schedule for data collection, establishment of the control measures, assessment for 

water uality standards attainment, and additio n3 modeling if needed. 

Quality assurance (QA) and uality control (QC) requirements should 3s 0 be met. 

Specific technical QA/QC is necessaxy in the 

use of environmental data and models. 

However, when using models, such as 

wasteload allocation models which involve 

“real” environmental data as well as parametric and mathematical relationships, model 

sensitivity studies can help establish the levels of QA/QC required for specific data. For 

example, the allowable range of uncertainty 

in the data can be established through model 

sensitivity studies. This allowable range of 

uncertainty may indicate, for example, the 

need for tight limits on precision for a particular pollutant 

sion 1s provide B 

ammeter. Ju#e~discuselsewhere. 

cotltinuhg Plannakgmces 

Each State is required to establish and 

maintain a continuing planning recess 

(CPP) as described in section 303(e 7 of the 

13 USEPA. September, 1980. Guidelines and Specifications for Preparing Quality Assurance Project Plans. 

QAMSM. Washington, D.C. 

14 USEPA. December, 1980. Interim Guidelines and Specifications for Preparing Quality Assurance Plans. 

QAMS-O05/80. Wzshington, D.C. 

15 USEPA. May, 1984. Guidance for Preparation of Combined WorWQuality Assurance Project Plans for 

l3wimnmed Monitoring. OWRS QA-1. Washington, D.C. 

29 
Clean Water Act. A State’s CPP contains, 

amo 

d& 

other items, a description of the prot the State uses to identify waters 

nefding uI8fer quality-based controls; a prio,~.y?gfgg~~~~~;~~~~ 

process used to receive public review of each 

TMDL Descri tionsmaybeasdetailedas 

the Regional o & ce and the State determine 

is necessary to descrik each step of the 

TMDL development process. ‘This process 

may be in&ded as art of the EPA/State 

Agreement for TMJJ E development. 

The State incorporates EPA approved 

and EPAestablished TMDti into its Water 

Quality Management Plan (WQMP). The 

Water Quality Management and Planning 

regulation provides that when EPA ap 

proves or establishes a TMDL under section 

303(d), the TMDL is automati P rated into the State’s WQMP.’ 

incorpoPublic NoticeandPardciphn 

In accordance with the Water Quality 

Management and Planning regulation and as 

16 50FR1777,Janury11,1!385and40CFRI3O. 

30 
described in a State’s CPP, the TMDLs 

should be made available for public comment. States and involved local communities should participate in determining which 

pollution sources should bear the treatment 

or control burden needed to reach allowable 

loadings. By involving the local communities in decision making, EPA expects that a 

higher probability of successful TMDL implementation will result. 

In the identification of water quality-limited waterbodies, States need to involve the 

public as part of their review of all existing 

and readily available data and information. 

This is especially true in such cases where a 

waterbody may be perceived as being at risk 

due to new dischargers and changes in land 

use. In such cases a waterbody’s water quality may be “threatened” and therefore should 

be given consideration for listing as a 303(d) 

water. EPA expects States to include public 

participation in its development of high priority targeted waterbodies that will proceed 

with TMDL development within two years 

following the listing process. 

In the development of a TMDL, a State 

should issue a public notice offering an opportunity for a public hearing pertinent to 

the TMDL under review. It is recommended that this be done in conjunctionwith 

public notices and hearings on NPDBS permits, construction of municipal wastewater 

treatment works, water quality standards revisions, and Water Quality Management 

Plan updates. Each notice should identify 

TMDLs as part of the subject matter.The 

State may wish to proceed to issuance of a 

final TMDLwithout a hearing once notice is 

given and there has been little or no response 

by the public. 

Also, if a State determines that the water 

quality-based controls may be controversial, 

the State should involve the EPA Regional 

office, as well as the public, early in the process and continue to involve them throughout the process. 

Reporring 

State submission of a list of waters still 

needing TMDLs and loads established is required by the Clean Water Act and the 

Water Quality Planning and Management 

regulations (40 CFR 130.7). These lists 

should complement EPA/State Agreements 

and the CPP, and be incorporated into the 

WQMP. States should submit the 303(d) 

lists either as part of or at the same time as 

the biennial section 305(b) reports. As part 

of this reporting requirement, States are expected to identify those waters targeted for 

TMDL development in the next two years. 

Targeted waterbodies are then scheduled for 

TMDL development through the annual 

work plan In addition, the pollutants or 

conditions causing violations of water quality 

standards and the point and nonpoint 

sources of the pollution causing those conditions should be identified for each waterbody on the 303(d) list (see page 28). States 

should consult the Section 305(b) Waterbody System’s Users Guide (August, 1989) 

to appropriately categorize sources and 

causes of pollutants. 

Other S’c@c Respnsibiliries 

Other State responsibilities are to 

l Ensure that needed environmental 

data are provided to EPA, including 

appropriate assessment data; appropriate screening data; and all regulatory data including data needed for 

approvals of the 303(d) lists and 

TMDLS, and 

o Ensure that appropriate quality assurance/quality control procedures 

are used for all data used in State 

decision making and for all data reported to EPA including data reported by dischargers. 

31 
EPA Resp~~ibilities 

Review of 303(d) L&s 

Section 303(d) and the Water Quality 

Planning and Management Regulation (40 

CFR 130.7(d)) requires EPA to review and 

approve or disapprove States’ lists of water 

quality-limited waters and the established 

pollutant loads. The lists are expected to be 

submitted biennially and will be approved or 

disapproved based in part on the State’s documentation and rationale for developing 

such lists as descriid under the State Responribilifi6 section of this chapter. 

K after reviewing the State lists and documentation, EPA is satisfied that the State 

has identified and appropriately listed all 

impaired waters and those targeted for action, EPA will then approve the lists and 

send a letter approving the submittal to the 

State. During this approval process, EPA 

may request a State to provide additional 

information if there is “good cause” to do so. 

“Good cause” may include, but is not limited 

to, more recent or accurate data; more accurate water quality modeling; flaws in the 

original analysis that led to the water being 

identified pursuant to 40 CFR 130.7; or 

changes in conditions (e.g., elimination of 

discharges). 

If the EPA disapproves (via a letter of 

disapproval to the State) a State’s list of waters needing new or revised TMDLs and 

those targeted for action, the Region (working closely with the State) then identifies 

those waters where new or revised, and targeted TMDLS are necessary. 

7iUDL Review andAppval 

Section 303(d) and the Water Quality 

Planning and Management regulation (40 

CFR X+0.7(d)) requires EPA to review all 

TMDLS for approval or disapproval. EPA 

may tailor its review to what is reasonable 

and appropriate. For example, where a State 

hasclearlydescribeditsTMDLprocess inits 

approved CPP (and EPA/State Agreement), 

EPA may conduct an indepth review of a 

sample of the State’s TMDLs to determine 

how well the State is implementing its approved process and conduct a less detailed 

review of the remaining Th6DLs. This indepth review of samples of the State submissions, in conjunction with a less detailed 

review of all other TMDLs submitted to 

EPA by the State, will provide a reasonable 

basis for EPA approval or disapproval of 

individual TMDLS. The in-depth sample review may include TMDLS supporting major 

construction projects and other major control measures. For those States that do not 

have an approved process, Regions are expected to conduct in-depth reviews of all 

TMDIs. The Region’s review should also 

consider how well the States are following 

applicable technical guidance for establishing TMDLS, WL&, and LAS. 

EPA must, at a minimum, determine 

whether the State’s TMDLS are “established 

at a level necessary to implement the applicable water quality standards with seasonal 

variations and a margin of safety that takes 

into account any lack of knowledge conceming the relationship be?fen effluent limitations and water quality. NoTMDLwillbe 

approved if it will result in a violation of 

water quality standards. 

If the State chooses not to develop the 

needed TMDLS for appropriate pollutants 

17 CWA scuba 303(d)(l) 

32 
on a timely basis or, if the TMDLS are unacceptable to EPA, EPA has a role under the 

Act to develo48the TMDLs in cooperation 

with the State. This wU be done by focusing available EPA resources on the most 

critical water quality problems. 

EPA must either approve or disapprove 

the State’s TMDL within 30 days after submission by the State. Where a Th4DL is 

approved, EPA transmits a letter of such 

approval. If EPA disapproves a State’s submission and the State does not agree to correct the problems, then EPA shall, within 30 

days of the disapproval date, establish such 

TMDLS as necessary to implement the water 

quality standards. EPA solicits public comment and after considering public comment 

and malting appropriate revisions, EPA 

transmits the revised TMDL to the State for 

incorporation in the State’s Water Quality 

Management Plan19 EPA prefers to discharge this duty through a cooperative effort 

with the States. 

ProgmmAUdi2.S 

EPA expects to measure performance on 

the basis of environmental results and administrative goals by means of program audits. To achieve this performance 

measurement, EPA will periodically conduct audits of State water quality programs 

primarily through Regional visits to the 

States, review of State toxics control programs, and State action plan summaries of 

EPA’~Surface Water Toxics Control Pro- 

&ram* These program audits will serve to 

determine where additional training or 

other assistance may be needed and to determine implementation of program objectives. 

TechnkulA.ktance and Thining 

EPA Headquarters and Regional offices 

are available to provide technical assistance 

and advice to tbe States in developing 

TMDLS. EPA Headquarters in coordination with the EPA Center for Exposure Assessment Modeling (CEAM) provides for 

training and assistance on modeling. EPA 

Headquarters also provides training and 

technical assistance to users of the Waterbody System (WBS). 

Guidance Documenrs and Repm 

EPA Headquarters is responsible for developing associated program guidance, tecbnical support with assistance from EPA 

research laboratories, and producing the biennial National Water Quality Inventory 

Report to Congress developed from the 

State section 305(b) assessment reports. 

EPA Headquarters is responsible for 

making sure the CWA mandates regarding 

TMDLs are carried out, providing oversight 

of the Regional offices and the States, developing program policy and guidance, supporting the development of computer software 

for calculating TMDLS, developing technical guidance documents, and providing technical training and assistance. Other 

responsibilities of EPA Headquarters are 

summarked on the next page. 

EPA &@bMl Respnstiiliries 

The EPA Regional offices are responsible for assisting Headquarters in developing 

policy and guidance, distributing policy and 

18 See Scott Decision: m 741 F.2d 992(7th Cir. 1984) 

19 40 CFR l30.7(d) 

2B 40 CFR 122,123, EQ Surface Water Toxk Control Program. 

33 
guidance totheStates,awardinggrantstothe 

States for developing and implementing 

water quality-based controh and providing 

technical assistmce to the Sta& In addition, the Regional offices are responsible for 

revicwingandapprovingor disapprovingthe 

following: each State’s TMDL process, the 

annual work program, the list of waters 

wbere TMDLS are needed, the list of targeted waters, and specific TMDLS, WI& 

and LAS. The EPA Regional offices are also 

responsible for reporting on State implementation to Headquarters. Other responsibilities of EPA Regional offices are 

summarized below. 

Other EPA Headquarters Responsibiites 

l Prepare pi&ace and ensure that approphte technical training and technical assistance is available for 

monitoring, water quality a&y& and data reporting. 

l Performnathalasx%nwU and wahmte the national water quality effects of CWA programs. 

l Make nathal data systems more usdid for national, regional, and State mecs by upgrading and 

mxdhkhg the uidng systems and dcvek+g interactive data retrieval and analy& mtchhnisms for 

line- QatinucsupportdthRiverRcachandIndustrialFaciiityDishrgcfh. 

l Ensurethat rppropriattq~~murct/qualitycontrolproccduFcsueusedioall;naticMaldata 

odlactioae&rcsandp~~~orysnpportforDItioiralscudicsofpolllurrnurequiringspecial 

l Prepare Headquarters budget rqucsts, and in axwhation with the Regions, prepare requests for 

Regional and State water quality moniaoring and analy& programs. 

l Peer review major agwxy program acdvities invohing water monitoring and consult with other program 

offices on water monitoring activities. 

Other EPA Regional Responsibiities 

l Easurc that the appropriate regulatory monitoring is performed by the States and discharges needed for 

developing and implcxnca~ water quality-based controls and identifying needed nonpoint source 

controls. This includes data rquircd to identify waters needingwater quality-based contrds, data needed 

to dcvclop contrds, and data Ix&cd to assess the eff~c5s of controls. 

0 Provide technical assistance and training to the States on watu quality monitoring and analyses. For work 

invdvirq toxic+ provide asdance in both the pollutant sp66c and the biomonitoring approaches and 

w&ok effluent toxicity. 

0 Ensure that appropriate quality assurauccYquality control procedures are used for all Regional and State 

wattrqualitydataandforalldatausedinRegionaldedsion~includingdatareportedbypumitttes. 

l Perform Regio~I water quahy assessments phmariiy based on State data as needed to prepare Environmental Mauagcmcnt Reports. 

l Ensure that Regional data systems are cotnpatible with and do not unnecessarily duplicate national data 

34 
APPENDIX A -RELATIONSHIP TO OTHER GUIDANCE 

Monitoring Guidance 

The Clean Water Act specifies that 

States and Interstate Agencies, in cooperation with EPA, establish water quality monitoring systems necessary to review and 

revise water quality standards, calculate 

TMDLs, assess compliance with permits, 

and report on conditions and trends in ambient waters. 

ance21 

EPA’s current program guiddiscusses the programmatic 

relationships of monitoring as an information collection tool for many program needs. 

NPS pollution concerns are discussed in 

draft guidance along with some means to 

monitor and evaluate NPSs.22 Revised 

Monitoring Program Guidance is planned 

for FY 1991. 

Cooperative Monitoring/Citizen 

Volunteer Monitoring Guidance 

Cooperative monitoring involves shared 

efforts by individuals or groups in assessing 

water quality conditions. Cooperative arrangements are encouraged by the Clean 

Water Act as referenced in section 104. Cooperative monitoring projects require careful planning and strong management 

controls. Current guidance 23 24 describes 

the factors to be considered in designing and 

implementing cooperative and volunteer 

monitoring projects so that specific provisions are made for the collection and analysis 

of scientifically valid water quality data, and 

so that the State water pollution control 

agencies have the necessary information for 

final review and approval of all projects. 

Cooperative monitoring projects can 

serve the same usefulness as other monitoring studies; however, they also provide a 

mechanism to maximize limited resources. 

In addition to “tapping” additional resources 

for monitoring, there are other incentives for 

States and the regulated community to cooperate, such as having more site-specific data 

from which to develop site-specific, scientifically-based water quality criteria. 

Citizen volunteer monitoring involves 

identifying sources of pollution, tracking the 

progress of protection and restoration projects, and/or reporting special events such as 

fish kills and storm damage. For more information on citizen monitoring programs, contact the EPA Office of Water Regulations 

21 USEPA. 1985. Guidance for State Water Monitoring and Wasteload Allocation Programs. OW/OWRS, 

EPA 440/4-85-031. Washington, D. C. 

22 USEPA. 1987. Draft Nonpoint Source Monitoring and Evaluation Guide. OW/OWRS, EPA. 

Washington, D. C. 

23 USEPA. 1984. Planning and Managing Cooperative Monitoring Projects. OW/OWRS, EPA 

440/4-84-018. Washington, D. C. 

24 USEPA. 1990. Volunteer Water Monitoring: A Guide for State Managers. OW, EPA 440/4-90-010. 

Washington, D. C. 

35 
and Standards (OWRS), Monitoring Branch 

at 202/382-7056. 

Technical Guidance Manuals for 

Performing Wasteload Allocations 

Wasteload Allocation Technical Guidance 

Technical guidance manuals prepared by 

EPA explain how to prepare wasteload allocations (WLAs). These manuals are listed at 

the right. Those available can be obtained 

from the OWRS Monitoring Branch at 

202/382-7056. 

Book Title 

I. General Guidance 

II. Streams and Rivers 

- Biochemical Oxygen Demand/Dissolved 

oxygen 

- Nutrient/Eutrophication 

- Toxic Substances 

Technical Support Document for 

Water Quality-based Toxics Control 

The Technical Support Document 

(TSD) for Water Quality-based Toxics Control 25 presents recommendations to regulatory authorities when they are faced with the 

task of controlling the discharge of toxic pollutants to the nation’s waters. Included in 

this document are detailed discussions on 

EPA’s recommended criteria for whole effluent toxicity, a screening analysis methodology for effluent characterization, human 

health risk assessment, the use of exposure 

assessments for wasteload allocations, and 

the development of permit requirements 

and compliance monitoring. The TSD provides guidance for assessing and regulating 

the discharge of toxic substances. It supports 

EPA’s initiative to control toxic pollution by 

involving the application of biological and 

chemical assessment techniques and proposes solutions to complex and site-specific 

pollution problems. Information on this 

document can be obtained from EPA’s 

Water Quality and Industrial Permits 

Branch at 202/475-9537. 

- Simplified Analytical Method for Determining NPDES Effluent Limitations for 

POTWs Discharging into Low-Flow 

Streams 

III. Estuaries 

- Estuaries and Wasteload Allocation 

Models 

- Application of Estuaries Waste Load Allocation Models 

- Use of Mixing Zone Models in Estuarine 

Waste Load Allocations* 

- Critical Review of Estuarine Waste Load 

Allocation Modeling 

IV. Lakes and Impoundments 

- Biochemical Oxygen Demand/Dissolved 

Oxygen 

- Nutrient/Eutrophication 

- Toxic Substances 

V. Technical Support Document for 

Water Quality-Based Toxics Control 

VI. Design Locations 

- Design Flow 

- Design Temperature, pH, Hardness, and 

VII. Permit Averaging 

VIII. Screening Manual 

- Biochemical Oxygen Demand/Dissolved 

Oxygen 

- Toxic Organics 

- Toxic Metals 

- Nutrient/Eutrophication 

IX. Innovative Wasteload Allocations* 

* not yet available 

25 USEPA. 1985. Technical Support Document for Water Quality-based Toxics Control. OW/OWRS and 

OWEP, EPA 440/4-85 Washington, D.C. A revised draft (April 23,1990) is available and will replace the 

1985 Guidance once it is finalized. 

36 
Permit W&KS Guidance 

The Permit Writer’s Guide to Water 

Qual&-based Permitting For Toxic Pollutants provides State and Federal NPDES 

permit writers and water quality management staff with a reference on water qualitybased permit issuance procedures. This 

guidance presents fundamental concepts 

and procedures in detail and refers to more 

advanced toxics control procedures, such as 

dynamic modeling of complex discharge situations, which may not yet be incorporated 

into many State programs. The guidance 

explains aspects of water quality-based toxits control in terms of what a permit writer 

currently needs to know to issue a water 

quality-based toxics control NPDES permit. 

The NPDES permits program is now focused on control of toxic pollutants and the 

guidance document is directed at supporting 

these control efforts. Water quality problems related to conventional pohutants, such 

as those associated with point source contributions to oxygen depletion, are addressed 

in other guidance documents. 

The Permit Writer’s guide addresses 

three areas of toxic effects: aquatic life, 

human health, and the bioaccumulation of 

specific chemicals. Each effect must be dealt 

with on an individual basis using available 

data and tools. This guidance also catalogues the principal procedures and tools 

available. 

The guidance supports an integrated toxits control strategy using both whole effluent 

toxicity-based assessment procedures and 

pollutant-specific assessment procedures. 

Roth procedures are needed to enforce State 

water quality standards. 

Nonpoint Source Guidance 

Section 319 of the Clean Water Act establishes direction and financial assistance 

for the implementatip of State NPS programs. NPS guidance encourages States to 

develop State Clean Water Strategies for 

integrating and unifying the States’ approach 

to water quality protection and clean-up. 

Three steps are identified for this process: 

comprehensive assessment of impaired or 

threatened waters, targeted protection of 

waters, and development of strategic management plans. States are to develop NPS 

programs which build upon related programs (e.g., Clean Lakes, National Estuaries, Stormwater Permits, Ground Water, 

Toxics Controls, State Revolving Funds, and 

Wetlands) and to coordinate their efforts 

with other federal agencies. 

The 1987 amendments to the CWA include provisions to encourage States to accelerate efforts to control nonpoint source 

pollution. The amendments require States 

to prepare a Nonpoint Source Assessment 

Report and a 4-year Management Program. 

Funds are provided to assist the States in 

implementing these programs. Information 

on this guidance can be obtained from EPA’s 

Nonpoint Source Control Branch at 

202082-7085. 

26 USEPA. 1987. Permit Writer’s Guide to Water @ml@-based Permitting for Toxic Pollutants. 

OW/OWEP, EPA 440&8%005. Washington, D.C. 

27 USEPA. 1987. Nonpoint Source Guidance. OW/OWRS, EPA. Washington, D.C. 

37 
APPENDIX B - SUPPORTING PROGRAMS 

EPA Water Quality Criteria and 

Standards 

The water quality standards program, as 

envisioned in Section 303(c) of the Clean 

Water Act, is a joint effort between the 

States and EPA The States have primary 

responsibility for setting reviewing revising 

and enforcing water quality standards. EPA 

develops regulations, policies, and guidance 

to help States implement the program and 

oversees States activities to ensure that State 

adopted standards are consistent with the 

requirements of the Act and the implementing Water Quality Standards regulation (40 

CFR Part 131). EPA has authority to review 

and approve or disapprove State standards 

and, where necessary, to promulgate Federal 

water quality standards. 

A water quality standard defines the 

water quality goals of a waterbody, or portion 

thereof, by designating the use or uses to be 

made of the water, by setting criteria necessary to protect the uses, and by preventing 

degradation of water quality through antidegradation provisions. States adopt water 

quality standards to protect public health or 

welfare, enhance the quality of water, and 

serve the purposes of the Clean Water Act. 

“Serve the purposes of the Act” (as defined 

in Sections 101(a), 101(a)(2), and 303(c) of 

the Act) means that water quality standards 

should: 1) include provisions for restoring 

and maintaining chemical, physical, and biological integrity of State waters, 2) provide, 

wherever attainable, water quality for the 

protection and propagation of fish, shellfish, 

and wildlife and recreation in and on the 

water (“fishable/swimmable”), and 3) consider the use and value of State waters for 

public water supplies, propagation of fish 

and wildlife, recreation, agriculture and industrial purposes, and navigation. 

In the current Water Quality Standards 

regulation, section 131.11 encourages States 

to adopt both numeric and narrative criteria. 

Criteria protect both short-term (acute ) and 

long-term (chronic) effects. Numeric criteria are important where the cause of toxicity is known or for protection against 

pollutants with potential human health impacts or bioaccumulation potential. Numeric water quality criteria may also be the 

best way to address nonpoint source pollution problems. Narrative criteria can be the 

basis for limiting toxicity in waste discharges 

where a specific pollutant can be identified 

as causing or contributing to the toxicity but 

there are no numeric criteria in the State 

standards, or where toxicity cannot be traced 

to a particular pollutant. Whole effluent toxicity (WET) testing is also appropriate for 

discharges containing multiple pollutants 

because WET testing provides a method for 

evaluating synergistic and antagonistic effects on aquatic life. Biological criteria provide a means to measure aquatic community 

structure and function. EPA considers a 

combination approach of narrative, numeric, and biological criteria necessary to 

protect beneficial uses fully from the broad 

range of point and nonpoint sources of pollution. 

In addition, the Clean Water Act in Section 303(c)(2)(B) requires States to adopt 

numeric criteria for priority toxic pollutants 

for which EPA has published criteria guid38 
ance when the discharge or presence of these 

pollutants could reasonably be expected to 

interfere with the designated uses in affected 

waters. States may adopt criteria with Statewide application or site-specific criteria. 

EPA’s regulation requires each State to 

adopt, as part of its water quality standards, 

an antidegradation policy consistent with 30 

CFR 131.12. The regulation also requires 

each State to have implementation methods 

for its antidegradation policies, i.e., decision 

criteria for assessing activities that may impact the integrity of a waterbody. Activities 

covered by the antidegradation policy and 

implementation methods include both point 

and nonpoint sources of pollution. Section 

131.12 effectively sets out a three-tiered approach for the protection of water quality. 

“Tier 1” (40 CFR 131.12 (a)(1)) of antidegradation maintains and protects existing 

uses and the water quality necessary to protect these uses. “Tier II” (section 

131.12(a)(2)) protects the water quality in 

waters whose quality is better than that necessary to protect “fishable/swimmable” uses 

of the waterbody. Outstanding national 

resource waters (ONRWs) are provided the 

highest level of protection under the antidegradation policy (‘Tier III”). 

States may, at their discretion, adopt policies in their standards affecting the application and implementation of standards. EPA 

specifically recognizes mixing zones, variances, low flow exemptions, and schedules of 

compliance for water quality-based permit 

limits. Guidance on these subjects is available from EPA’s Office of Water Regulations and Standards, Criteria and Standards 

Division. 

Section 305(b) -- Water Quality 

Assessment 

Section 305(b)28 establishes a process for 

reporting information about the quality of 

the nation’s water resources to EPA and 

Congress. Each State, Territory, and Interstate Commission develops a program to 

monitor the quality of its surface and ground 

waters and report the current status of water 

quality biennially to EPA This information 

is compiled into a biennial report to Congress. The 305(b) report allows EPA to: 

• 

• 

• 

• 

• 

• 

• 

• 

Determine the status of water quality. 

Identity water quality problems and 

trends. 

Evaluate the causes of poor water 

quality and the relative contributions 

of pollution sources. 

Report on the activities underway to 

assess and restore water quality. 

Determine the effectiveness of control programs. 

Ensure that pollution control programs are focused on achieving environmental results in an efficient 

manner. 

Determine the workload remaining 

in restoring waters with poor quality 

and protecting threatened waters. 

Use information from the lists of waters developed under sections 304(l) 

28 USEPA. 1989. Guidelines for the Preparation of the 1990 State Water Quality Assessment (section 

305(b) Report). OW/OWRS. Washington, D. C. 

39 
and 319 and continue to maintain and 

update the statutorily-required lists 

of waters identified under sections 

303(d) and 314. 

For each assessed waterbody, information is provided on the water quality-limited 

status, use nonattainment causes and 

sources, cause magnitude, and source magnitude. Much of the information from the 

305(b) assessments provide useful information for developing lists of water quality-limited segments asked for in section 303(d). 

Section 304fl) -Impaired Waters 

Section 304(UB required lists of impaired waters and sources to be submitted to 

EPA as a “one time” effort. These lists of 

waters (known as the short, long, and mini 

lists) provide three types of designations for 

impaired waters and source impacts. The 

mini list (section 304(l)(l)(A)(i)) is a list of 

waters that the State does not expect to 

achieve numeric water quality standards for 

priority pollutants (section 307(a)) after 

technology-based requirements have been 

met, due to point or nonpoint source pollution. The long list (section 304(1)( l)(A)(ii)) 

is a comprehensive list of waters that are not 

meeting the fishable and swimmable goals of 

the Act whether due to toxicity or other impairments; point or nonpoint sources; or 

toxic, conventional. or nonconventional pollutants. A waterbody which meets its designated use criteria and does not meet 

fishable/swimmable criteria would be listed 

on the section 304(l) long list but not necessarily on the section 303(d) list of waters 

needing TMDLs. It would be appropriate 

for a State to use the information on all 

waters from its long lists and apply these data 

in developing the section 303(d) list of waters that still do not meet applicable water 

quality standards. The short list (section 

304(l)(l)(B)) is a list of State waters that are 

not expxted to meet applicable standards 

after technology-based controls have been 

met, due entirely or substantially to discharge of toxic pollutants from point sources. 

A fourth list is the list of point source dischargers of priority toxic pollutants to waters 

listed under section 304(l). 

Se&n 319 - Nonpoint Source 

p%Pm 

One key initiative of the 1987 Water 

Quality Act Amendments to the Clean 

Water Act was the addition of section 319 

which established a national program to control nonpoint source pollution. Under this 

program, States are asked to assess their NPS 

pollution problems and submit that assessment to EPA These assessments include a 

list of “navigable waters within the State 

which, without additional action to control 

nonpoint sources of pollution, cannot reasonably be expected to attain or maintain 

applicable water quality standards or the 

goals and requirements of this Act.” Other 

paragraphs of section 3 19 require the identification of categories and subcategories of 

NPS pollution which contribute to the identification of impaired waters; descriptions of 

the procedures for identifying and implementing BMPs; control measures for reducing NPS pollution; and descriptions of 

State and local programs used to abate NPS 

pollution. Based upon the assessments, 

State nonpoint source management programs are prepared and presented to EPA 

for approval. Once these programs are approved, grant funds are made available for 

the implementation of the program. 

29 USEPA. March, 1988. Final Guidance for Implementation of Requirements under section 304(l) of the 

Clean Water Act as Amended. OWRS and OWEP. Washington, D.C. 

40 
Section 319 assessments identify waters 

with impairments due primarily to NPSs for 

which TMDLs (including LAS) may need to 

be developed to establish protection of 

water quality. States are encouraged to use 

these tools where appropriate to achieve or 

protect beneficial uses of the water. 

Section 314 -- C&fan Lakes Progrrrm 

Historically, the Clean Lakes Program 

has been active in awarding grants for the 

study and restoration of publicly-owned 

lakes. Under this program, states are encouraged to develop integrated water quality 

strategies that include lake and reservoir 

management, restoration, and protection activities. EPA provides financial assistance as 

available; however, greater emphasis is now 

on developing technical support material 

(e.g., a Lake and Reservoir Restoration 

Guidance Manual). 

Section 320 -- Ndional Estuary 

Progmm 

Authorized by Congress in 1985, and formally established in 1987 by amendments to 

the Clean Water Act, the National Estuary 

Program (NEP) builds upon the lessons of 

the Chesapeake Bay, Great Lakes, and other 

earlier programs in a geographic, basin-wide 

approach to environmental management. 

The EPA Administrator selects estuaries for 

NEP participation through State governors’ 

nominations. To be selected estuaries must 

demonstrate a likelihood of success and evidence of institutional, &xmcial, and political 

commitment to solve their problems. 

Among the environmental problems addressed in the NEP estuaries are the loss of 

aquatic habitats, toxic contamination of estuarine sediments, increases in nutrient levels, bacterial contamination, and hypoxia. As 

methods for assessing and successfully managing these estuaries are developed, this national demonstration program aims to 

communicate its lessons to the more than 

150 estuaries located along our coasts. 

For approved estuaries, the Administrator convenes management conferences, a 

grouping of interested Federal, Regional, 

State, and local governments, affected industries, scientific and academic institutions, 

and citizen organizations. Management 

conferences strive for an open, consensusbuilding approach to defining program goals 

and objectives, identijing problems to address, and designing pollution prevention/control and resource management 

strategies to meet each objective. Management conferences are required to create and 

begin implementation of a Comprehensive 

Conservation and Management Plan 

(CCMP) designed to protect and restore the 

estuary. 

Monitoring Program 

Ambient water quality monitoring is a 

data gathering tool used for almost all water 

quality assessment. Monitoring programs 

serve to identify waters needing TMDLS, 

quantify loads, verify models, and evaluate 

effectiveness of water quality controls (including BMP effectiveness). Once TMDLs 

have been established for a given waterbody, 

follow-up monitoring is recommended to 

document improvement or lack of improvement. Since the TMDL process is iterative, 

monitoring data can provide the information 

for updating and revising current TMDLs. 

Ambient monitoring is used for setting permit conditions, compliance, and enforcement, and detecting new problems and 

trends. 

Emnt Limitation Guidelines and 

StUndatdr 

EPA develops effluent limitation guidelines and new source performance standards 

for industrial dischargers. These are uniform technology-based limitations for indus41 
trial facilities discharging directly into the 

nation’s waters. EPA also develops pretreatment standards for those facilities which discharge into Publicly Owned Treatment 

Works (POTWs). 

During the effluent guidelines promulgation process, EPA develops a profile of the 

industry to determine pollutant loadings of 

untreated wastewater for which effluent limitation guidelines are being developed. Pollutants of concern and technologies for 

treating them are then identified. EPA then 

prepares estimates of total investment, operation and maintenance costs of complying 

with each technology option, and evaluates 

the regulatory options, both technically and 

economically, to select a technology as the 

basis for the guidelines. 

Effluent limitations, guidelines, and 

standards are established for three types of 

industrial pollutants: conventional, toxic, 

and nonconventional. Effluent guidelines 

generally limit the amount of pollutant that 

can be discharged at an individual facility. 

The numerical limits in the guidelines are 

determined using industry-specific production data and the treatability data for the 

selected technology. 

NPVES Permits and Individual 

Control Stmtegies 

All discrete sources of wastewater must 

obtain a National Pollutant Discharge Elimination System (NPDES) permit that regulates the facility’s discharge of pollutants. 

The approach to controling and eliminating 

water pollution is focused on the pollutants 

determined to be harmful to receiving waters and on the sources of such pollutants. 

Authority for issuing NPDES permits is gtablished under section 402 of the CWA 

Point sources are generally divided into 

two types: “industrial” and “municipal.” Nationwide, there are approximately 50,000 industrial sources which include commercial 

and manufacturing facilities. Municipal 

sources, also known as POTWs, number 

about 15,700 nationwide. Wastewater from 

municipal sources results from domestic 

wastewater discharged to POT% as well as 

the “indirect” discharge of industrial wastes 

to sewers. 

Section 304(1)(1)(D) required, at a minimum, the development of individual control 

strategies (ICSs) for point source discharges 

of priority toxic pollutants to waters identified on the short list. (The short list is composed of State waters for which applicable 

section 307(a) priority pollutant standards 

are not expected to be achieved after technology-based controls have been met, due 

entirely or substantially to point sources.) 

An ICS consists of NPDES permit limitations and schedules for achieving established 

limitations, along with other documentation 

to demonstrate that the con ls selected are 

appropriate and adequate. ‘Ip 

Marine and Estuarine W&em 

In January 1990, EPA published its National Coastal and Marine Policy, which establishes EPA’s goals for coastal and marine 

protection. They include: 

l Recover full use of the nation’s 

shores, beaches, and water. 

30 USEPA. 1989. Overview of selected EPA Regulations and Guidance Affecting POTW Management. 

OW/OMPC, EPA 440/69-89AN8. Washington, D.C. (Hotline: 800-424-9346) 

31 USEPA. 1987. Permit Writer’s Guide to Water Quality-based Permining for Toxic Pollutants. 

OW/OWEP, EPA 440/4-87-005. Washington, D.C. 

42 
Restore the nation’s shell fisheries 

and salt-water fisheries. 

. . . Mmmze the use of coastal and marine water for waste disposal. 

Improve and expand coastal science. 

Support international efforts to protect coastal and marine resources. 

EPA’s programs to protect ocean and 

coastal waters and the Great Lalres from 

nutrient and toxic pollutants emanating from 

point and nonpoint sources are implemented under the Clean Water Act and 

the Marine Protection, Research, and Sanctuaries Act (Ocean Dumping Act). 

Marine and estuarine waters are, in many 

cases, the ultimate sink for pohtants which 

emanate from upland sources. Estuarine 

and marine waters are particularly complex 

and it is often d.i&ult to predict Pollutant 

fate and transport. To address the increased 

complexity and effect on aquatic life, water 

quality management efforts must increase 

accordingly. TMDLS can be a useful tool for 

management of marine and estuarine waters. Technical guidance is currently &ing 

revised to support estuarine modeling. 

Groundwuter 

Contaminated ground water discharge to 

surface water may be a source of contaminants in water quality-limited surface waters. 

While ground water and surface water are 

often treated as separate systems, they are in 

reality highly interdependent components of 

the hydrologic cycle. Subsurface interactions with surface waters occur in a variety of 

ways. In several studies, ground water discharge accounted for as much as 90% or 

more of stream flow in humid regions. 

Therefore, the potential pollutant contributions from ground water to surface waters 

should be investigated when developing 

TMDLS. Additional information is available from the EPA Office of Ground Water 

Protection. 

CERCLA 

The Comprehensive Environmental Response, Compensation, and Liability Act 

(CERCLA) or “Superfund” provides broad 

federal authority to respond directly to releases or threatened releases of hazardous 

substances. This law also provides for the 

cleanup of inactive or abandoned hazardous 

waste sites. Under CERCLA, EPA assesses 

the nature and extent of contamination at a 

site, determines the public health and environmental threats posed by a site, analyzes 

the potential cleanup alternatives, and takes 

action to clean up the site. In instances 

where a CERCLA site has impact on a 

nearby waterbody, the level of cleanup 

needed to maintain water quality standards 

of surface waters should have a direct relationship to the TMDL for the affected surface waters. As part of the CERCLA 

process, all “applicable or relevant and appropriate requirements” of statutes such as 

the CWA must be followed. Load allocations developed pursuant to section 303(d) 

may, in appropriate circumstances, be “applicable or relevant and appropriate.” 

PO’TWs that discharge CERCLA hazardous substances in effluent at levels that 

equal or exceed NPDES permit limitations, 

or for which no specific limitations exist, or 

in spills or other releases, may be subject to 

the notification requirements and liability 

provisions under CERCLA. In addition, 

32 USEPA. Technical Guidance Manual for Performing Wasteload AIbcations, Book III - Estuaries. 

43 
POTWs that disposed of sludge in impoundments or ladills that are Superfund 

sites may be required to pay for cleanup of 

those sites. At times, POTWs may be requested to accept wastewaters from Superfund cleanup activities. If discharge of 

CERCLA wastewaters to a POTW is 

deemed appropriate, the discharger must 

ensure compliance with substantive and procedural requirements of the national pretreatment program and all local 

pretreatment regulations before discharging 

wastewater to the POTW. 

The provisions of CERCLA extend well 

beyond the regulation of POTW discharges. 

The most common types of Superfund sites 

governed by CERCLA include abandoned 

hazardous waste sites and inactive mines, 

many of which do not discharge to POTWs. 

The Superfund Amendments and 

Reauthorization Act (SARA Hotline 80@ 

535-0202), which amended CERCLA, also 

established in Title III a new program to 

increase the public’s knowledge of and access to information on the presence of haxardous chemicals in their communities and 

releases of these chemicals into the environment. Title III (Community Right to Know 

Program) requires facilities to notify State 

and local officials if they have extremely hazardous substances present at their facilities 

in amounts exceeding certain “threshold 

planning quantities.” If appropriate, the facility must also provide material safety data 

sheets on hazardous chemicals stored at 

their facilities, or lists of chemicals for which 

these data sheets are maintained, and report 

annually on the inventory of these chemicals 

used at their facility. The law may also require facilities to submit information each 

year on the amount of toxic chemicals released by the facilities to all media (air, 

water, and land), if they fall within Standards 

Industrial Classification Codes 20 to 39 and 

meet certain threshold limits. 

44 
APPENDIX C - SCREENING CATEGORIES 

This list of screening categories is based on categories promulgated as the minimum data 

set a State should consider when developing their list of impaired waters pursuant to section 

304(l) of the Clean Water Act. When developing lists pursuant to this guidance and to meet 

the requirements of section 303(d), a State should, at a minimum, use these categories to 

identify their water quality-limited waters. States should also consider additional information, 

such as TRI data, streamflow information collected by USGS, locally available data, and public 

comments on proposed 303(d) lists. 

1. 

2. 

3. 

4. 

5. 

6. 

7. 

Waters where fishing or shellfish bans 

and/or advisories are currently in effect 

or are anticipated. 

Waters where there have been repeated 

fishkills or where abnormalities (cancers, 

lesions, tumors, etc.) have been observed 

in fish or other aquatic life during the last 

ten years. 

Waters where there are restrictions on 

water sports or recreational contact. 

Waters identified by the State in its most 

recent State section 305(b) report as either “partially achieving” or “not achieving” designated uses. 

Waters listed under sections 304(l) and 

319 of the CWA. 

Waters identified by the State as priority 

waterbodies. (State Water Quality Management plans often include priority 

waterbody lists which are those waters 

that most need water pollution control 

decisions to achieve water quality standards or goals.) 

Waters where ambient data indicate potential or actual exceedances of water 

quality criteria due to toxic pollutants 

from an industry classified as a primary 

8. 

9. 

industry in Appendix A of 40 CFR Part 

122. 

Waters for which effluent toxicity test 

results indicate possible or actual exceedances of State water quality standards, including narrative “free from” 

water quality criteria or EPA water quality criteria where State criteria are not 

available. 

Waters with primary industrial major dischargers where dilution analyses indicate 

exceedances of State narrative or numeric water quality criteria (or EPA 

water quality criteria where state standards are not available) for toxic pollutants, ammonia, or chlorine. These 

dilution analyses must be based on estimates of discharge levels derived from 

effluent guidelines development documents, NPDES permits or permit application data (e.g., Form 2C), Discharge 

Monitoring Reports (DMRs), or other 

available information. 

10. Waters with POTW dischargers requiring local pretreatment programs where 

dilution analyses indicate exceedances of 

State water quality criteria (or EPA 

water quality criteria where State water 

quality criteria are not available) for 

45 
toxic pollutants, ammonia, or chlorine. 

These dilution analyses must be based 

upon data from NPDES permits or permit applications (e.g., Form 2C), Discharge Monitoring Reports (DMRs), or 

other available information. 

11. Waters with facilities not included in the 

previous two categories such as major 

POTWs, and industrial minor dischargers where dilution analyses indicate exceedances of numeric or narrative State 

water quality criteria (or EPA water 

quality criteria where State water quality 

criteria are not available) for toxic pollutants, ammonia, or chlorine. These dilution analyses must be based upon 

estimates of discharge levels derived 

from effluent guideline development 

documents, NPDES permits or permit 

application data, Discharge Monitoring 

Reports (DMRs), or other available information. 

12. Waters classified for uses that will not 

support the “fishable/swimmable” goals 

of the Clean Water Act. 

13. Waters where ambient toxicity or adverse water quality conditions have been 

reported by local, State, EPA, or other 

Federal agencies, the private sector, pub14. Waters identified by the State as impaired in its most recent Clean Lake Assessments conducted under section 314 

of the Clean Water Act. 

15. Waters identified as impaired by non- 

. point sources in America’s Clean Water: 

. The States' Nonpoint Source Assessments 1985 (Association of State and Interstate Water Pollution Control 

Administrators (ASIWPCA)) or waters 

identified as impaired or threatened in a 

nonpoint source assessment submitted 

by the State to EPA under section 319 of 

the Clean Water Act. 

16. Surface waters impaired by pollutants 

from hazardous waste sites on the National Priority List prepared under section 105(8)(A) of CERCLA, 

lic interest groups, or universities. These 

organizations and groups should be actively solicited for research they may be 

conducting or reporting. For example, 

university researchers, the United States 

Department of Agriculture, the National 

Oceanic and Atmospheric Administration, the United States Geological Survey, and the United States Fish and 

Wildlife Service are good sources of field 

data and research. 
APPENDIX D -SELECTED TECHNICAL 

CONSIDERATIONS 

Design Conditions 

When developing a TMDL, design conditions are those critical conditions that must 

be specified in order to determine attainment of water quality standards. In specifying conditions in the waterbody, an attempt 

is made to use a reasonable “worst case” 

condition. For example, stream analysis 

often uses a low flow (e.g., 7-day low flow, 

once in 10-years commonly known as 7Q10 or 

biologically-based 4-day 3-year flows) high 

temperature design condition. 

In situations where nonpoint source 

loadings at wet weather flow conditions are 

more significant than the point source loadings, the use of low flow-related design conditions is inappropriate. Wet weather flow 

conditions may be appropriate for analysis of 

nonpoint and intermittent point source discharges such as storm sewers. Other factors 

such as rainfall intensity and duration, time 

since previous rainfall, pollutant accumulation rates, and stream flow previous to rainfall should be considered in selecting design 

conditions for nonpoint source analysis. In 

some instances (e.g., carcinogenic pollutants), it is appropriate to use the harmonic 

mean flow to estimate loading capacity. 

Often conditions of best management 

practices may be specified for factors other 

than physical conditions. For example, assumptions about cropping patterns, logging 

rates, or grazing practices may be necessary 

to determine the pollution loading estimates 

of a waterbody. Design conditions are less 

standardized for these factors and a reasonable worst case condition often must be developed on a case-by-case basis. 

In general for point sources, continuous 

discharges present the greatest stress under 

low flow, dry weather conditions. For pollutants transported in runoff, critical conditions will be rainfall-related, but may occur 

under a variety of flow conditions. For NPSs 

or intermittent point sources, generally, high 

flow, wet weather conditions need to be evaluated. For carcinogenic pollutants, harmonic mean flows may be appropriate. 

Additional details for selecting design conditions are provided in technical guidance. 

Mathematical Models 

When the analyst is calculating a numerical TMDL, several mathematical models 

can be used to evaluate alternative pollutant 

loading scenarios. Models supported by the 

EPA Center for Exposure and Assessment 

Modeling (CEAM) are summarized in Ap33 USEPA. 1985. Technical Support Document for Water Quality-based Toxics Control OW/OWEP and 

OWRS, EPA 440/4-85-032. Washington, D.C. A revised draft (April 23, 1990) is available and will 

replace the 1985 Guidance when finalized. 

47 
pendix E. While it is beyond the scope of this 

guidance to provide a detailed rationale for 

model selection, the following briefly presents a discussion on model characteristics 

and selection. • Specific constituents and processes 

Model characteristics 

Models can be characterized in numerous ways such as by their data requirements, 

ease of application, etc. This section summarizes models based on four categories: 

temporal characteristics, spatial characteristics, specific constituents and process simulated, and transport processes. 

• Temporal characteristics - This includes whether the model is steadystate (inputs and outputs constant 

over time), time-averaged (for example, tidally-averaged), or dynamic. If 

the model is dynamic, an appropriate 

time step needs to be selected. For 

example, streams may require short 

time steps (hourly or less) while 

lakes, which typically have residence 

times in excess of weeks, can generally be modeled with longer time 

steps (e.g., daily or more). Similarly, 

loads from NPS models are often 

lumped together into event or annual 

loadings. 

• 

• Spatial characteristics - This includes 

the number of dimensions simulated 

and the degree of spatial resolution. 

In most stream models, one-dimensional models are used since typically 

vertical and horizontal gradients are 

small. For large lakes and estuaries, 

two- or three-dimensional models 

may be more appropriate because 

both vertical and horizontal concentration gradients commonly occur. 

Segmented or multiple catchment 

models may be more appropriate for 

heterogeneous watersheds, whereas, 

Transport processes -These include 

advection, dispersion, runoff, interflow, ground water interactions, and 

the effects of stratification on these 

processes. Most river models are 

concerned only with downstream advection and dispersion. Lake and estuary models may include advection 

and dispersion in one or more dimensions, as well as the effects of density 

stratification. For toxic modeling, it 

may be important to use models 

which account for near-field mixing 

since many of these pollutants may 

exert maximum toxicity close to the 

point of discharge. To incorporate 

both point and nonpoint sources into 

TMDLs, it will be important to consider integrated watershed models: 

Model selection 

lumped single-catchment models are 

more appropriate for homogeneous 

or less complex situations. 

simulated-Models vary in the types 

of constituents and processes simulated and in the complexity of the 

formulations used to represent each 

process. For example, simple DO 

models include only reaeration and 

BOD decay while more complex 

models include other processes such 

as nitrification, photosynthesis, and 

algal respiration. 

A model should be selected based on its 

adequacy for the intended use, for the specific waterbody, and for the critical conditions occurring at that waterbody. While the 

selection of an appropriate model should be 

made by a water quality analyst, it is useful 

for program managers to be familiar with the 

decisions which must be made. Four basic 

48 
steps have been identified that an analyst 

would go through to select an appropriate 

model: 

l Identify models applicable to the situation. 

l Define the appropriate level of analysis. 

0 Incorporate practical constraints into 

the selection criteria. 

0 Select a specific model. 

. . to the sltuatlon . 

An obvious choice for narrowing the selection of an appropriate model is based on the 

waterbody type (river, estuary, or lake) and 

the type of analysis (BOD/DO, toxics, etc.) 

A preliminary list of models may also be 

screened by selecting models which consider 

the appropriate constituents and processes 

that are important for the pollutant being 

studied. 

. 

e of e . 

Four types of models are: 

m - These include dilution and mass balance calculations, Streeter-Phelps equations 

and modifications thereof, analytical 

solutions to transport equations, 

steady-state nutrient loading models, 

regression models, and other simplified modeling procedures that can be 

performed on desk top calculators. 

ter & 

These models compute average spatial profiles of constituents along a 

river or estuary assuming everything 

remains constant with time, including 

loadings, upstream water quality conditions, stream flow rates, meteorological conditions, etc. 

. l m - These models are a compromise between 

steady-state models and dynamic 

models. Quasi-dynamic models assume most of the above factors remain constant, but allow one or more 

of them to vary with time, for example 

waste loading rates or stream flow 

rates. Some of the models hold the 

waste loading and flow rates constant, 

but predict effects such as the diurnal 

variations in dissolved oxygen due to 

algal photosynthesis and respiration. 

. 0 s - These models predict temporal and spatial variations in 

water quality due to varied loadings, 

flow conditions, meteorological conditions, and internal processes within 

the watershed or waterbody. Dynamicmodels are useful for analyzing 

transient events (e.g., storms and long 

term seasonal cycles) such .as those 

important in lake eutrophication 

analyses. 

The above model types are listed in order 

of increasing complexity, data requirements, 

and cost of application. In addition, lognormal probabilistic models and Monte Carlo 

simulation techniques have been used to 

modify some of the above approaches. 

Probabilistic models use lognormal probability distributions of model inputs to calculate probability distributions of model 

output. Since this method does not incorporate fate and transport processes, it can only 

be used to predict the concentration of a 

substance after complete mixing and before 

decay or transformation significantly alters 

the concentration Monte Carlo simulations 

combine probabilistic inputs with deterministic models. A fate and transport model is 

run a large number of times based on ran49 
domly selected input values. The output 

from these models are then rank ordered to 

produce a frequency distribution. These frequency distributions may then be compared 

to instream criteria (e.g., criteria maximum 

concentration (CMC) and criteria continuous concentration (CCC)) to determine if 

water quality standards are met. 

. . 1 . In general, the analyst should consider the data 

requirements for each level of analysis, the 

availability of historical data, the modeling 

effort required for each level of analysis, and 

available resources. Availability of historical data for calibration and verification is one 

of the key cost savings considerations. 

. ctasDeclfic . The analyst should 

consider model familiarity, technical sup 

port and model availability, documentation 

quality, application ease, and professional 

recognition and acceptance of a model. 

PoWant AlLocahn Schemes 

Individual States use various load allocation schemes appropriate to their needs and 

may specify that a particular method be used. 

Methods of allocating loads have been historically applied to point sources. Application of these methodologies to nonpoint 

sources has not been well studied to date. 

Three common methods for allocating loads 

(equal percent removal, equal effluent concentrations, and a hybrid method) are discussed below. Other methods are detailed 

in another EPA document3 

The first method is equal percent removal and exists in two forms. In one, the 

overall removal efficiencies of the sources 

are set so they are all equal. In the latter, the 

incremental removal efficiencies beyond the 

current discharge are equal. This method is 

appropriate when the incremental removal 

efficiencies are relatively smal& so that the 

necessary improvement in water quality can 

be obtained by minor improvement in treatment at each point source, at little cost. 

The second common allocation method 

specifies equal effluent concentrations. This 

is similar to equal percent removal if influent 

concentrations at all sources are approximately the same. However, if one source has 

substantially higher influent levels, then 

equal effluent concentrations will require 

higher overall treatment levels than the 

equal percent removal approach. 

The third commonly used method of allocating loads can be termed a hybrid 

method. With this method, the criteria for 

waste reduction may not be the same from 

one source to the next. One source may be 

allowed to operate unchanged while another 

may be required to provide the entire load 

reduction. More generay, a proportionality rule may be assigned that requires the 

percent removal to be proportional to the 

input source loading or flow rate. 

Multiple Disduuges 

TMDLs are particularly critical for 

waterbodies when the effect from multiple 

pollution sources overlap. The key concern 

associated with multiple point or nonpoint 

pollution sources is the potential for combined impacts. To perform this analysis, it 

may be necessary to apply near-field mixing 

models (mixing zone analysis) in addition to 

34 USEPA. 1985. Technical Support Document for Water Quality-based Toxics ControL OWlOWEP and 

OWRS, EPA 440/4-85-032. Washington, D.C. A revised draft (April 23.1990) is available and will replace 

the 1985 Guidance when final&d. 

50 
a far-field model which considers pollutants 

from numerous point or nonpoint sources 

(after the mixing zone). A recommended 

procedure for evaluating toxicity from multiple ’ !P charges is summarizd in EPA guidance. 

AkYkatbn Tmzdkofls 

Where appropriate and technically feasible, certain cost-effective benefits may be 

gained by making tradeoffs among 

wasteload allocations. Such a practice is similar to what would be done during the initial 

considerations of tradeoffs of loads between 

point and nonpoint sources. In the case of 

watershed or estuary management, this may 

be particularly useful to achieve pollution 

reduction in the most cost-effective manner 

possible. 

The incentive for trading load allocations 

is to achieve the required level of control by 

choosing to control one pollutant source 

over another. Technological feasibility, economic issues, and regulatory authority are all 

factors to consider when trading allocations. 

For example, to reduce nutrient loads to a 

receiving water, nonpoint source controls 

that can be adequately maintained and enforced, may be much more cost effective 

than increasing the level of control on a point 

source discharger. 

Pollutant trades are most likely to occur 

between point and nonpoint sources. However, where effluents from different point 

source dischargers are comparable, trades 

may be acceptable so long as water quality 

standards (including antidegradation regulations and policies) and minimum applicable 

technology-based controls are met. Sirnilarly, tradeoffs between nonpoint sources 

are also acceptable. 

The Dillon Reservoir (west of Denver, 

Colorado) is an example of point and nonpoint source phosphorus load tradeoffs. In 

this example, the cost associated with point 

source reduction was $1.5 million per year, 

whereas the cost associated with NPS controls was $0.2 to $1.0 million per year. Because of this cost differential, tradeoffs 

allowed publicly-owned treatment works to 

achieve reductions in phosphorus loads to 

the Dillon Reservoir by controlling NPSs 

rather than expanding the sewage treatment 

system. 

Persistent and/or Highly 

BioaccumuCative Toxic Polhmts 

Persistent and/or bioaccumulative toxic 

pollutants require special attention during 

analysis of toxicity and TMDL development. 

The primary concern is that toxic pollutants 

that enter a waterbody at levels that are nontoxic in the water column may accumulate in 

sediment or aquatic life. These pollutants 

may then adversely affect aquatic&ildlife or 

pose a risk to humans by exposure to hazardous chemicals through consumption of contaminated fish or shellfish. Chemicals that 

bioaccumulate at high rates include some 

metals, organic compounds, and organometallic compounds. Current technical 

guidance for wasteload allocation (see Appendix A) summarize a number of models 

which are appropriate for modeling the fate 

and transport of toxics in streams/rivers, 

lakes, and estuaries. Additional details for 

assessing and controlling risk have been addressed in technical support documentation. 

35 USEPA. 1985. Tcchical Support Document for Water Quality-based Toxiu Control. OW/OWEP and 

OWRS, EPA 440/4-85-032. Washington, DC. A revised draft (April 23.1590) is available and will replace 

the 1985 Guidance when final&d. 

51 
Use of Two-nun&w Crircrio 

Because of inherent variation in effluent 

and receiving water flows and pollutant concentrations, specifying a concentration that 

must not be exceeded at any time or place 

may not be appropriate for the protection of 

aquatic life. The format usually selected for 

expressing water quality criteria to protect 

aquatic life consists of recommendations 

concerning concentration magnitudes, duration of averaging periods, and average frequencies of allowed excursions. Use of this 

magnitudeduration-frequency format allows water quality criteria for aquatic life to 

be adequately protective without being as 

overprotective as if criteria were expressed 

using a simpler format. In many cases, these 

considerations are evaluated during the 

standards setting process and TMDLS are 

used to develop controls that result in attainment of applicable water quality standards. 

Duration of exposure considers the 

amount of time organisms will be exposed to 

toxicants. It is expressed as that period of 

time over which the instream concentration 

is averaged for comparison with criteria concentrations. Frequency is defined as how 

often exposures that exceed the criteria can 

occur during a given period of time (e.g., 

once every three years) without unacceptably affecting the community. To account 

for acute toxic effects, States may adopt 

acute criteria expressed as the criteria maximum concentration (CMC) occurring in a 

one-hour averaging period. Similarly, 

chronic criteria expressed as the criteria continuous concentration (CCC) should be developed as toxicant concentrations which 

should not be exceeded over longer periods 

of time. For the purposes of modeling, the 

ambient concentration should not exceed 

the CMC more than once every three years. 

(If the biological community is under stress 

because of spills, multiple dischargers, or has 

a low recovery potential, or if a local species 

is very important, the frequency should be 

decreased.) 

Although these criteria are mostly used 

for application to low flow conditions, the 

toxicological basis for the criteria is equally 

valid for high flow conditions. It is important 

for States to protect designated water uses 

during all flow conditions; therefore, the 

two-number criteria should be used for all 

flow conditions unless separate guidance for 

adopting wet weather criteria is available. 

However, States should apply duration and 

frequency parameters to account for the high 

flow, intermittent nature of nonpoint source 

loadings. 

sediment Issues 

The problems associated with clean and 

contaminated sediment are not the same. 

Clean sediment can impair fish reproduction 

by silting-up spawning areas, and can increase turbidity. Draft (clean) sediment criteria have been developed in Idaho that 

include turbidity, inter-gravel dissolved oxygen, and cobble embeddedness. The criteria 

developed may be most appropriate for salmonid streams, but the framework may have 

wide application. The major concerns regarding contaminated sediment are pollutant releases to the water column, 

bioaccumulation, and biomagnification. 

Sediment criteria being developed by EPA 

have centered on evaluating and developing 

an understanding of the principal factors that 

influence the sediment/contaminant interactions with the water column (Equilibrium 

Partitioning Approach). (The Science Advisory Board will be reviewing methods for 

establishing sediment criteria for metal contaminants and procedures for establishing 

standardized bioassays in 1991.) Through 

such an understanding, exposure estimates 

of benthic and other organisms can be made. 

Chronic water quality criteria, or possibly 

other toxicological endpoints, can then be 

used to predict potential biological effects. 

52 
In some cases, sediment criteria alone 

would be sufficient to identify and to establish clean up levels for contaminated sedimerits. In other cases, the sediment criteria 

should be supplemented with biological or 

other types of analysis before clean-up decisions can be made. Additionally, ground 

water inputs through sediments should be 

distinguished from inputs from the sediment 

alone, so that proper control measures are 

implemented. 

53 
APPENDIX E - MATHEMATICAL MODEL SUPPORT 

The Center for Exposure Assessment 

Modeling (CEAM) was established in July, 

1987 to meet the water quality and exposure 

modeling needs of States and EPA program 

and Regional offices. CEAM provides exposure assessment technology, training, and 

consultation for analysts and decisions-makers operating under various legislative mandates, including the Clean Water Act. 

With support and resources from the 

Monitoring Branch in the Assessment and 

Watershed Protection Division, Office of 

Water Regulations and Standards, CEAM 

maintains a distribution center for water 

quality models and databases for the user 

community. Users are kept up to date 

through user group meetings, a newsletter, 

and an electronic bulletin board. For the 

major wasteload allocations models, CEAM 

offers 2- to 5-day training courses at EPA 

Headquarters, Regional sites, and the Athens Environmental Research Laboratory facility. Longer-term “on-the-job” training at 

CEAM for individuals is also available. 

Technical assistance and review are provided by CEAM scientists and engineers, as 

well as by affiliated academics and consultants. Exposure calculations and assessments for especially difficult or unusual 

discharge situations can be arranged as resources allow. 

The center currently distributes 21 simulation models and databases. These can be 

applied to urban runoff (SWMM4, HSPF9), 

leaching and runoff from soils (PRZM, 

HSPF9), transport through soil and ground 

water (MULTIMED, RUSTIC), conventional pollution of streams (QUAL2E, 

HSPF9, WASP4), toxic pollution of streams 

54 

(HSPF9, WASP4, EXAMS2, DYNTOX), 

toxic pollution of lakes and estuaries 

(WASP4, EXAMS2), conventional pollution of lakes and estuaries (WASP4), nearfield mixing and dilution in rivers, lakes, 

estuaries, and oceans (CORMIX1), cohesive sediment transport (SED2D-V), river 

and tidal hydrodynamics (DYNHYD5, 

RIVMOD, HYDRO2D-V, HYDRO3D), 

geochemical equilibrium (MINTEQA3), 

and aquatic food chain bioaccumulation 

(FGETS). Software and databases distributed to aid in data analysis include ANNIEIDE, DBAPE, and the CLC Database. 

Currently available models are summarized 

below. Those with no version number are 

available as test code, and will be routinely 

distributed when fully tested. 

Table E-1 CEAM Supported Models 

DYNTOX 1.0 

EXAMSII 2.94 

HSPF 9.01 

MINTEQA3/PRODEFA3 3.00 

PRZM 1.00 

QUAL2E-UNCAS 

SWMM 

3.11 

3.3 

WASP4/TOXI/EUTRO 

DYNHYD5 

4.22 

5.02 

GCSOLAR 

FGETS 

1.10 

1.00 

CORMIX1 1.00 

ANNIE-IDE 1.11 

DBAPE 1.05 

CLC Database 2.00 

RUSTIC - 

MULTIMED - 

HYDRO2D-V - 

SED2D-V - 

HYDRO3D - 

RIVMOD - 
CEAM operates an Electronic Bulletin 

Board System (BBS) to meet the increasing 

demand for supported exposure assessment 

models. It allows efficient communication 

between users with modem-equipped computers and CEAM support staff as well as 

immediate acquisition of models by those 

under extreme time pressure. The services 

presently offered are: 1) downloading of 

CEAM supported models, 2) uploading of 

user input data sets for staff review and problem solving, 3) a bulletin area listing current 

CEAM activities and events, such as training 

courses, helpful hints about the models, and 

model documentation, and 4) a message 

area for discussion of computer modeling 

problems and enhancements. To access the 

CEAM BBS, a user must call 404/546-3403 

or FTS 250-3402 and follow the interactive 

prompts. The communications parameters 

are 9600/2400/1200 baud, no parity, 8 data 

bits, and 1 stop bit. 

Information about obtaining the models 

may be obtained by writing the Center for 

Exposure Assessment Modeling. U.S. EPA, 

College Station Road, Athens, GA 30613, or 

by calling 404-546-3549. 

55 
APPENDIX F - GENERAL EPA/STATE 

AGREEMENT OUTLINE FOR 

DEVELOPMENT OF TMDLs 

Since conditions, procedures, and methodologies may vary between EPA Regions and their 

States, a general outline of an example agreement is provided. This outline can be used in 

conjunction with the referenced technical guidance documents to prepare EPA/State Agreements. 

I. General 

A. Purpose, Scope, and Authority 

B. Statement of Policy 

II. Water Quality Standards Considerations 

A. General 

B. Type of Stream Classifications 

III. Allocation Procedures and Policies 

A. Basic Approach for Establishing 

Boundaries for TMDL Development 

B. Determination of TMDL, WLA, and LA 

Using Water Quality Models 

C. Determination of TMDL, WLA, and LA 

Using Other Analytical Tools 

D. Special Case Policies 

IV. Public Participation Process 

V. Approval of TMDL, WLA, and LA 

VI. Incorporation of Allocations into NPDES Permits 

A. General 

B. Priority Considerations 

Appendix. State Continuing Planning Process (CPP) 
APPENDIX G - CAUSES AND SOURCES OF POLLUTION 

Causes and Sources: Section 305(b) Waterbody System User’s Guide, Third Edition 

(Version 2.0), August 1989, USEPA, Office of Water, Assessment and Watershed Protection 

Division, pages A-27 through A-31. 

Causes 

Causes are the pollutants or conditions 

that are causing or expected to a exceedances of water quality standards. One 

or more of the following categories should 

be used to identify causes of impairment: 

- 

- 

- 

- 

- 

- 

- 

- 

- 

- 

- 

- 

unknown toxicity 

pesticides 

priority organics 

nonpriority organics 

metals 

ammonia 

chlorine 

other organics 

nutrients 

pH 

siltation 

filling and draining 

- 

- 

- 

- 

- 

- 

- 

- 

- 

- 

- 

- 

organic enrichment/ 

DO 

salinity/TDS/chlorides 

thermal modifications 

flow alterations 

other habitat 

alterations 

pathogens 

radiation 

oil and grease 

taste and odor 

suspended solids 

noxious aquatic plants 

cause unknown 

Sources 

Sources are the point and nonpoint 

sources of the pollution categories that are 

listed as causes identified above. One or 

more of the following categories should be 

used to identify sources of impairment: 

- source unknown 

- industrial point - municipal point 

sources sources 

- combined sewer - agriculture 

overflow 

- silviculture - construction 

- urban runoff/storm - resource extraction 

sewers 

- land disposal - hydromodification 

- habitat modification 

Other categories: 

- atmospheric deposition - storage tank leaks 

- highway maintenance/ - spills 

runoff 

- in-place contaminants - natural 

- recreational activities - upstream impoundments 

- salt storage sites 

57 
LIST OF ACRONYMS 

ARAR 

AT 

BAT 

BCT 

BMP 

BOD5 

BPJ 

BPT 

CCC 

CEAM/BBS 

CERCLA 

CFR 

CLP 

CMC 

CPP 

CSO 

CWA 

DO 

EPA 

FR 

ICS 

LA 

LC 

MOS 

NCMP 

NEP 

NPDES 

NPS 

POTW 

QA/QC 

SARA 

TMDL 

TRE 

TRI 

TSD 

WBS 

WLA 

WQMP 

WWTP 

Applicable or Relevant and Appropriate Requirements 

Advanced Treatment 

Best Available Technology 

Best Conventional Technology 

Best Management Practice 

5-day Biochemical Oxygen Demand 

Best Professional Judgement 

Best Practicable Control Technology 

Criteria Continuous Concentration 

Center for Exposure Assessment Modeling/Electronic Bulletin Board System 

Comprehensive Environmental Response, Compensation, and Liability Act 

Code of Federal Regulations 

Clean Lakes Program 

Criteria Maximum Concentration 

Continuing Planning Process 

Combined Sewer Overflow 

Clean Water Act 

Dissolved Oxygen 

Environmental Protection Agency 

Federal Register 

Individual Control Strategy 

Load Allocation 

Loading Capacity 

Margin of Safety 

National Coastal and Marine Policy 

National Estuary Program 

National Pollutant Discharge Elimination System 

Nonpoint Source 

Publicly Owned Treatment Works 

Quality Assurance/Quality Control 

Superfund Amendments and Reauthorization Act 

Total Maximum Daily Load 

Toxic Reduction Evaluation 

Toxic Release Inventory 

Technical Support Document 

Waterbody System 

Wasteload Allocation 

Water Quality Management Plan 

Wastewater Treatment Plant 

58 
General Contact 

Phone Number 

GW 

OWRS 

OMEP 

OWEP 

OMPC 

ODW 

OGWP 

OWP 

SELECTED OFFICES, DIVISIONS, BRANCHES, 

AND SECTIONS WITHIN EPA 

Office of Water 382-5700 

Office of Water Regulations and Standards 382-5400 

AED Analysis and Evaluation Division 382-5389 ITD 

FE 

Industrial Technology Division 382-7120 

Criteria and Standards Division 382-7301 

AWPD Assessment and Watershed Protection Division 382-7040 

Monitoring Branch 382-7056 

Monitoring Management Section (TMDLs/WLAs) 

Monitoring Analysis Section 

Water Quality Analysis Branch 382-7046 

Information Services Section 

Special Studies Section 

Exposure Assessment Section 

Nonpoint Source Control Branch 382-7085 

Clean Lakes Section 

Nonpoint Source Control Section (BMPs/LAs) 

Office of Marine and Estuarine Protection 382-7166 

Office of Water Enforcement and Permits 475-8488 

Office of Municipal Pollution Control 382-5850 

Office of Drinking Water 382-5543 

Office of Ground Water Protection 382-7077 

Office of Wetlands Protection 475-7791 

All area cods are 202.