vvEPA
            United States
            Environmental Protection
            Agency
            Office Of Water
            (4204)
EPA 832-B-95-008
September 1995
Combined Sewer Overflows
Guidance For Permit Writers

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                                                         EPA 832-B-95-008
                         For
                Office of Wastewater Management
              U.S. Environmental Protection Agency
                       401 M Street, SW
                     Washington, DC
                          August 1995
Recycled/Recyclable * Printed with Vegetable Based Inks on Recyeted Paper (20% Postconsumer)

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                                NOTICE

The statements in this document are intended solely as guidance.  This document
is not intended, nor can it be relied on, to create any rights enforceable by any
party In litigation with the United States.  EPA and State officials may decide to
follow the guidance provided in this  document, or to act at variance with the
guidance, based on an analysis of specific site circumstances.  This guidance may
be revised without  public notice  to reflect changes  in  EPA's  strategy for
implementation of the Clean Water Act and its implementing regulations, or to
clarify and update the text.

Mention  of trade names or  commercial products in this document does not
constitute an endorsement or  recommendation for use.

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                 UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
                                WASHINGTON, D.C. 20460   "
                                                                           OFFICE OF
                                                                            WATER

MEMORANDUM

SUBJECT:   CSO Guidance for Permit Writers

FROM:      Michael B. Cook, Director (420
             Office of Waste water Managem

TO:          Interested Parties

       1 am pleased to provide you with the Environmental Protection -\:cr,^\ % d.PA's)
guidance document for permit writers involved in developing National l\ '..^r.:  D.icharge
Elimination System (NPDES) permits with Combined Sewer Overflow tC'Su. ..inJmons.
This docoment is one of several  being prepared to foster implemeniatu>-  t>: i S'A's CSO
Control Policy. The CSO Control Policy, issued on April 11, 1994, c/-:>;.. v.-s  j rational
approach under the NPDES permit program  for controlling discharges ;:,'.  r » *:,,:u»n"s
waters from combined sewer systems.

       To facilitate implementation of the CSO Control Policy, EPA i^ pr.-vr.r ; guidance
documents that can be used  by NPDES permitting authorities, aft'eckv; - -* ..,;i..«,:ies, and
their consulting engineers in planning and implementing CSO control- n.,.-  *.,  -Itimately
comply with the requirements of the Clean Water Act.

       Specifically, this manual  provides guidance to NPDES permitiir:; ^,.::;on:ies and
permit writers to develop and issue NPDES permits to control CSOs in a.,\»:o^.nje with the
expectations of the National CSO Control Policy.  It recommends procedures ar.i! provides
example permit language that permit writers can use to develop defensible and enforceable
NPDES permit requirements. This guidance  assumes the permit writer is responsible for
ensuring coordination and involvement with WQS  authorities, enforcement authorities, the
public, and the permittee,

       This guidance has been reviewed extensively within the Agency as well as by
municipal groups, environmental groups, and other CSO stakeholders,  I am  grateful to all
who participated in its preparation and review, and believe that it will further the
implementation of the CSO  Control Policy.

       If you have any questions regarding the manual or its distribution, please call Tony
Smith in  the Office of Wastewater Management, at (202) 260-1017.
                                                                    Pnraad ««Ui SoyiCs/wia W< en (taoot that
                                                                        at toast 50% r»cyd«£f Rber

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                        TABLE OF

                                                               Page


1    INTRODUCTION	,	1-1

     1.1   BACKGROUND	1-1
     1.2   HISTORY OF THE CSO CONTROL POLICY  	1-1
     1.3   KEY          OF THE CSO CONTROL POLICY  ,	1-3
     1.4   GUIDANCE TO SUPPORT IMPLEMENTATION OF THE CSO
          CONTROL POLICY	1-6
     1.5   PURPOSE OF MANUAL AND TARGET AUDIENCE	,	1-6
     1.6   ORGANIZATION OF MANUAL  	1-7

2    INTRODUCTION TO CSO PERMITTING	2-1

     2.1   OVERVIEW OF CSO PERMITTING APPROACH	2-1
     2.2   RESPONSIBILITY OF       PERMITTING AUTHORITIES	2-3
     2.3   CSO PERMITTING          AND WATERSHED
          CONSIDERATIONS	2-4
     2.4   MECHANISMS FOR REQUIRING CSO CONTROLS	2-5
     2.5   COMPLEX  COMBINED      SYSTEMS  	2-6
     2.6   PREVIOUS  OR ONGOING CSO CONTROL EFFORTS	  2-9
     2.7   COMBINED      SYSTEMS IN SMALLER JURISDICTIONS ....  2-9
     2.8   MEASURES OF SUCCESS	2-10
     2.9   COORDINATION WITH STATE WATER QUALITY STANDARDS
          AUTHORITY	,	  2-12

3    PHASE I PERMITTING  	3-1

     3.1          I                	3-1
     3.2   INFORMATION  NEEDS  	3-1
     3.3   IDENTIFICATION OF CSO OUTFALLS IN THE        	3-3
     3,4   NINE MINIMUM CONTROLS	3-3
          3.4.1  Implementation Considerations	3-6
          3.4.2  Documentation and Reporting	  3-9
     3.5   LONG-TERM CONTROL PLAN	  3-10
          3.5.1  Components of the Long-Term Control Plan	  3-13
                3.5.1.1  Public Participation	  3-14
                3.5.1.2  Characterization, Monitoring, and Modeling of the
                       CSS and Receiving Waters 	  3-18
                                                          August 1995

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                       TABLE OF            (Continued)

                                                                          Page

                  3.5.1.3   Consideration of Sensitive Areas	  3-19
                  3.5.1.4   Evaluation of Control Alternatives	  3-20
                  3.5.1.5   Cost/Performance Considerations  	  3-26
                  3.5.1.6   Operational Plan  ,	  3-27
                  3.5.1.7   Maximization of Treatment at the POTW Treatment
                           Plant	  3-27
                  3.5.1.8   Implementation Schedule  	  3-28
                  3.5.1.9   Post-Construction Compliance Monitoring Program  . .  3-29
            3.5.2  Schedule for Development of the Long-Tenn Control Plan  ....  3-30
            3.5.3  Considerations for Previous or Ongoing CSO Control Efforts
                  and Small Combined Sewer Systems	  3-32
                  3.5.3.1   Recognition of Previous or Ongoing Efforts at
                           Controlling CSOs	,...,".	  3-32
                  3.5.3.2   Small System Considerations	  3-34
      3.6   EFFLUENT LIMITATIONS	  3-34
            3.6.1  Technology-Based Requirements	  3-35
            3.6.2  Water Quality-Based Requirements	  3-36
      3.7   MONITORING .	  3-37
      3.8	  3-40
      3.9   SPECIAL CONDITIONS	  3-40
            3.9.1  CSO-Related Bypass  	  3-40
            3.9.2  Permit Reopener Clause	  3-41
      3.10  ADDITIONAL ACTIVITIES DURING PHASE I PERMITTING  ....  3-41

4     PHASE H PERMITTING	4-1

      4.1   PHASE II  PERMIT PROCESS	 4-1
      4.2   INFORMATION	4-2
      4.3   IDENTIFICATION OF CSO OUTFALLS IN THE PERMIT	4-3
      4.4   NINE MINIMUM CONTROLS	4-3
            4.4.1  Review of Permittee's Implementation of the Nine Minimum
                  Controls	4-4
                  4.4.1.1   Proper Operation and Regular Maintenance Programs
                           for the CSS and CSO Outfalls	 4-5
                  4.4.1.2   Maximum Use  of the Collection System for Storage  ... 4-6
                  4.4.1.3   Review and Modification of Pretreatment  Programs  ... 4-6
                  4.4.1.4   Maximization of Flow to Publicly Owned Treatment
                           Works Treatment Plant  .  ,	4-7
                  4.4.1.5   Prohibition of CSOs During Dry Weather Flow
                           Conditions	 4-7
                                       ii                            August 1995

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                              OF CONTENTS (Continued)

                                                                           Page

                  4.4.1.6   Control of Solid and Floatable Materials in CSOs   ....  4-8
                  4.4.1.7   Pollution Prevention Program  	4-8
                  4.4.1.8   Public Notification	4-9
                  4.4.1.9   Monitoring to Effectively Characterize CSO Impacts
                           and Efficacy of CSO Controls  	4-9
            4.4.2  Permit Conditions	  4-10
                  4.4.2.1   Documentation for Fact Sheet/Statement of Basis ....  4-14
      4.5    LONG-TERM CONTROL PLAN		  4-14
            4.5.1  Review of Long-Tenn Control Plan	  4-15
                  4.5.1.1   Public Participation	  4-17
                  4.5.1.2   CSS Characterization, Monitoring, and Modeling ....  4-17
                  4.5.1.3   CSO Control Alternatives  .	  4-19
                  4.5.1.4   Selected CSO Controls	  4-19
                  4.5.1.5   Implementation Schedule   	  4-20
                  4.5.1.6   Operational Plan  	  4-21
                  4.5.1.7   Post-Construction Compliance Monitoring	4-22
            4.5.2  Implementation of the Long-Term Control Plan	4-22
                  4.5.2.1   Selected CSO Controls	  4-23
                  4.5.2,2   Operational Plan	  4-24
                  4.5.2.3   Post-Construction Compliance Monitoring	4-25
                  4.5.2.4   Documentation for Fact Sheet/Statement of Basis ....  4-25
      4.6    EFFLUENT LIMITATIONS	  4-26
            4.6.1  Technology-Based Requirements		4-26
            4.6.2  Water Quality-Based Requirements	 .  4-26
                  4.6.2.1   Presumption Approach	  4-28
                  4.6,2.2   Demonstration Approach   	  4-29
      4.7    MONITORING	  4-30
      4.8    REPORTING .	  4-33
      4.9    SPECIAL CONDITIONS	4-34
            4.9.1  CSO-Related Bypass	  4-34
            4.9.2  Reassessment of Sensitive Areas 	  4-37
            4,9.3  Permit Reopener Clause	4-38

5     POST-PHASE II PERMITTING	 5-1

      5.1    CONTINUATION OF        II	 5-1
      5.2   SUBSEQUENT  CSO PERMITTING	5-2
                                       iii                            August 1995

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                  TABLE OF CONTENTS (Continued)

                                                            Page

APPENDIX A COMPILATION OF EXAMPLE CSO PERMIT CONDITIONS	A-l

APPENDIX B DEVELOPMENT AND REVIEW OF MONITORING AND MODELING
           PLAN	B-l

APPENDIX C SUGGESTED NINE MINIMUM CONTROLS EVALUATION
           CHECKLIST	C-l

APPENDIX D SUGGESTED LONG-TERM CONTROL PLAN EVALUATION
           CHECKLIST	D-l

GLOSSARY	 G-l

REFERENCES	R-l
                               iv                      August 1995

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                                LIST OF


                                                                              Page

Exhibit 1-1.   Roles and Responsibilities	1-5

Exhibit 2-1.   Categories of CSO Permitting Conditions	2-7

Exhibit 3-1.   Example Permit Language for Identifying CSO Outfalls in the Phase I
             Permit  	3-3
Exhibit 3-2.   Summary of the Nine Minimum Controls	 3-5
Exhibit 3-3.   Example Permit Language to Require Immediate Implementation of the
             Nine Minimum Controls  	3-7
Exhibit 3-4.   Example Permit Language for Requiring Documentation and Reporting
             of the Nine Minimum Controls	  3-10
Exhibit 3-5.   Example Types of NMC Documentation	  3-11
Exhibit 3-6.   Example Permit Language for Requiring the Development of a Long-
             Term Control Plan	*!	  3-15
Exhibit 3-7.   Sensitive Areas Identified in the CSO Control Policy .	  3-19
Exhibit 3-8.   Example Permit Language for Requiring Compliance with Narrative
             Water Quality Standards	  3-37
Exhibit 3-9.   Example Permit Language for a Phase I Reopener Clause   	  3-41

Exhibit 4-1.   Example Permit Language for Identifying CSO Outfalls in a Phase II
             Permit	4-3
Exhibit 4-2.   Example Permit Language for Continued Implementation  of the Nine
             Minimum Controls	•	  4-11
Exhibit 4-3.   Example Permit Language for Implementing Selected CSO Controls .  . .  4-25
Exhibit 4-4.   Example Permit Language for Performance Standards for  the
             Presumption Approach	  4-29
Exhibit 4-5.   Example Permit Language for Site-Specific Monitoring  Activities  ....  4-32
Exhibit 4-6.   Example Permit Language for Requiring Submission of Progress
             Reports	  4-33
Exhibit 4-7.   Example Permit Language for a CSO-Related Bypass	  4-37
Exhibit 4-8.   Example Permit Language for Sensitive Area Reassessment	4-38
Exhibit 4-9.   Example Permit Language for Reopener Clauses	  4-39
                                                                       August 1995

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                                    CHAPTER 1
                                  INTRODUCTION

1.1
       Combined sewer systems (CSSs) are wastewater collection systems designed to cany
sanitary sewage (consisting of domestic, commercial, and industrial wastewater) and storm water
(surface drainage from rainfall or snowmelt) in a single pipe to a treatment facility.  CSSs serve
about 43 million people in approximately  1,100  communities nationwide.   Most of these
communities are located in the Northeast and Great Lakes regions.  During dry weather, CSSs
convey domestic, commercial, and industrial wastewater.  In periods of rainfall or snowmelt,
total wastewater flows can exceed the capacity of the CSS and/or treatment facilities. When this
occurs, the CSS is designed to overflow directly to surface water bodies, such as lakes, rivers,
estuaries, or coastal waters. These overflows—called combined sewer overflows (CSOs)—can
be a major source of water pollution in communities served by CSSs.

       Because CSOs contain untreated domestic, commercial, and industrial wastes, as well as
surface runoff, many different rypes of contaminants can be present. Contaminants may  include
pathogens,  oxygen-demanding  pollutants, suspended solids, nutrients,  toxics, and floatable
matter.  Because of these contaminants and the volume of the flows, CSOs can cause a variety
of adverse impacts on the physical characteristics of surface water, impair the viability of aquatic
habitats, and pose a potential threat to drinking water supplies.  CSOs have been shown to be
a major contributor to use impairment and aesthetic degradation in many receiving waters and
have contributed to shellfish harvesting restrictions, beach  closures, and even occasional fish
kills.

1.2               OF THE CSO CONTROL POLICY
       Historically, the control of CSOs has proven to be extremely complex.  This complexity
stems partly from the difficulty in quantifying CSO impacts on receiving water quality  and the
site-specific variability in the volume, frequency, and characteristics of CSOs. In addition, the
financial considerations for communities with CSOs can be significant. The U.S. Environmental

                                         1-1             "                 August 1995

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Chapter 1	Introduction

Protection Agency (EPA) estimates the CSO abatement costs for the 1,100 communities served
by CSSs to be approximately $41.2 billion.

       To address these challenges, EPA's Office of Water issued a National Combined Sewer
Overflow Control Strategy  on August 10, 1989 (54 Federal Register 37370).  This Strategy
reaffirmed  that CSOs  are  point source discharges  subject to National Pollutant Discharge
Elimination System (NPDES) permit requirements and to Clean Water Act (CWA) requirements.
The CSO Strategy recommended that all CSOs be identified and categorized according to their
status of compliance with these requirements.  It also set forth three objectives:

       *   Ensure that if CSOs occur, they are only as a result of wet weather
       •   Bring all wet weather CSO discharge points  into compliance with the  technology-
          based and water  quality-based requirements of the CWA
       *   Minimize the impacts  of CSOs on water quality, aquatic biota, and human health.

In addition, the CSO Strategy charged all States with developing state-wide permitting strategies
designed to reduce, eliminate,  or control CSOs.

       Although the CSO Strategy was successful in focusing increased attention on CSOs, it
fell short in  resolving many  fundamental issues.   In mid-1991, EPA  initiated a process  to
accelerate  implementation  of  the  Strategy.     The  process  included  negotiations  with
representatives of the regulated community. State regulatory agencies, and environmental groups.
These negotiations were conducted through the Office of Water Management Advisory Group.
The initiative resulted in the development of a CSO Control Policy, which was published in the
Federal Register on April 19,  1994 (59 Federal Register 18688).
                                          1-2                              August 1995

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Chapter 1                                                                 Introduction


      The intent of the CSO Control Policy is to:


      8   Provide  guidance to permittees with CSOs, NPDES permitting and enforcement
          authorities, and State water quality standards (WQS) authorities

      *   Ensure coordination among the appropriate parties in planning, selecting, designing,
          and implementing CSO management practices and controls to meet the requirements
          of the CWA

      •   Ensure public involvement during the decision-making process,


      The CSO Control Policy contains provisions for developing appropriate, site-specific

NPDES permit requirements for all CSSs that overflow due to  wet weather events.  It also

announces an enforcement initiative that requires the immediate elimination of overflows that

occur during dry weather and ensures that the remaining CWA requirements are complied with
as soon as possible.


1.3   KEY              OF      CSO CONTROL POLICY

      The CSO Control Policy contains four key principles to ensure that CSO controls are

cost-effective and meet the requirements of the CWA:
       •  Provide clear levels of control that would be presumed to meet appropriate health and
          environmental objectives

       *  Provide sufficient flexibility to municipalities, especially those that are  financially
          disadvantaged, to consider the site-specific nature of CSOs and to determine the most
          cost-effective  means of  reducing  pollutants  and meeting  CWA objectives  and
          requirements

       *  Allow a phased approach  for implementation  of  CSO controls considering  a
          community's financial capability

       *  Review and revise, as appropriate, WQS and their implementation procedures when
          developing long-term CSO  control plans  to reflect the site-specific  wet weather
          impacts of  CSOs.
                                          1-3                              August 1995

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Chapter 1                                                                  Introduction


       In addition,  the CSO Control Policy clearly  defines expectations  for permittees, State
WQS authorities, and NPDES permitting  and  enforcement authorities.   These expectations
include the following:
       •  Permittees should immediately implement the nine minimum controls (NMC), which
          are technology-based actions or measures designed to reduce CSOs and their effects
          on receiving water quality, as soon as practicable but no later than January 1, 1997,

       •  Permittees should give priority to environmentally sensitive areas,

       •  Permittees should develop long-term control plans (LTCPs)  for controlling CSOs.
          A permittee may use one of two approaches:  1) demonstrate that its plan is adequate
          to  meet  the  water  quality-based requirements  of  tie  CWA  ("demonstration
          approach"),  or 2) implement a  minimum  level  of treatment (e.g.,   primary
          clarification of at least 85 percent of the collected combined sewage flows) that is
          presumed to  meet the water  quality-based requirements of the  CWA, unless data
          indicate otherwise ("presumption approach"),

       *  WQS authorities should review and revise, as appropriate. State WQS during the
          CSO long-term planning process.

       •  NPDES permitting authorities should consider the financial capability of permittees
          when reviewing CSO control plans.
       Exhibit 1-1 illustrates the roles and responsibilities of permittees, NPDES permitting and
enforcement authorities, and State WQS authorities.


       In addition to these key elements and expectations, the CSO Control Policy also addresses

important issues such as ongoing or completed CSO control projects, public participation, small

communities,  and watershed planning.
                                           1-4                              August 1995

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                                                 Exhibit  1-1.  Roles and Responsibilities
            Permittee
    NPDES Permitting Authority
   NPDES Enforcement Authority
      State WQS Authorities
* Evaluate and implement NMC

» Submit documentation of NMC
  implementation hy January 1,
  1997

* Develop LTCP and submit for
  review to NPDIiS permitting
  authority

• Support the review of WQS in
  CSO-impacted receiving wafer
  bodies

• Comply with permit conditions
  hascd on narrative WQS

* Implement selected CSO controls
  from LTCP

* Perform post-construction
  compliance monitoring

• Reassess overflows to sensitive
  areas

* Coordinate alt activities with
  NPDBS permitting authority.
  State WQS authority, and Slate
  watershed personnel
*  Reassess/revise CSO permitting
   strategy

*  Incorporate into Phase i permits
   CSO related conditions (e.g., NMC
   implementation and documentation
   and LTCP development)

«  Review documentation of NMC
   implementation

*  Coordinate review of LTCP
   components throughout the LTCP
   development process and
   accept/approve permittee's  LTCP

*  Coordinate the review and  revision
   of WQS as appropriate

«  Incorporate into Phase II permits
   CSO-related conditions (e.g.,
   continued  NMC implementation and
   LTCP implementation)

*  Incorporate implementation schedule
   into an approptiate en
   mech.tniMn
  if p *rH >r t
* Ensure that CSO requirements and
  schedules for compliance are
 " incorporated into appropriate
  enforceable mechanisms

9 Monitor adherence to January I,
  1997, deadline for NMC
  implementation and documentation

• Take appropriate enforcement action
  against dry weather overflows

» Monitor compliance with Phase I,
  Phase II, and post-Phase II permits
  and take enforcement action as
  appropriate
* Review WQS in CSG-impacted
  receiving water bodies

• Coordinate review with LTCP
  development

* Revise WQS as appropriate:

  Development of site-specific
  criteria

  Modification of designated use to

  - Create partial use reflecting
    specific situations
  - Define use more explicitly

  Temporary variance from WQS

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Chapter 1	  	Introduction


1.4   GUIDANCE TO             IMPLEMENTATION OF THE CSO CONTROL
      POLICY

      To help permittees and NPDES permitting and WQS authorities implement the provisions

of the CSO Control Policy, EPA is developing the following guidance documents:
      •  Combined Sewer Overflows—Guidance for Long-Term Control Plan (EPA, 1995a)
         (EPA 832-B-9S-002)

      *  Combined Se\ver Overflows—Guidance for Nine Minimum Controls (EPA, 1995b)
         (EPA 832-B-95-GG3)

      •  Combined Sewer Overflows—Guidance for Screening and Ranking (EPA, 1995c)
         (EPA 832-B-95-Q04)

      •  Combined Sewer Overflows—Guidance for Monitoring and Modeling (EPA, 1995d)
         (EPA 832-B-95-OOS)

      *  Combined Sewer   Overflows—Guidance far Financial  Capability  Assessment
         (EPA, 1995e) (EPA 832-B-95-006)

      •  Combined Sewer Overflows—Guidance for Funding Options  (EPA, 1995f) (EPA
         832-B-95-Q07)

      ?  Combined Sewer Overflows—Guidance for Permit  Writers  (EPA,  1995g) (EPA
         832-B-95-008)

      •  Combined Sewer Overflows—Questions and Answers on Water Quality Standards and
         the CSO Program (EPA, 1995h)  (EPA 832-B-95-Q09),
1.5              OF MANUAL AND TARGET AUDIENCE

      This manual provides guidance to NPDES permitting authorities and permit writers on

developing and issuing NPDES permits to control CSOs in accordance with the expectations of
the CSO Control Policy.  Whenever possible, the manual translates the CSO Control Policy into
instructions, procedures, and example permit language that permit writers can use to develop

defensible and enforceable NPDES permit requirements. The document emphasizes the role of

the permit writer as the  facilitator and coordinator of the CSO control program in achieving
compliance with the CWA, including attainment of WQS. This guidance assumes the permit
                                       1-6                            August 1995

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                                                                         Introduction
writer  is  responsible  for  ensuring  coordination and  involvement with  WQS  authorities,
enforcement authorities, the public, and the permittee.

       This manual is designed to be used by EPA and State NPDES permit writers who possess
a working knowledge of the CWA and NPDES permit regulations and requirements to control
point source discharges. Therefore, it provides guidance only for developing CSO-related permit
conditions; it does not provide the more general information available in other NPDES permit
guidance manuals, such as the training manual for NPDES  permit  writers.  In addition, this
manual does not provide technical guidance on the operation of CSSs and the control of CSOs,
Information on these topics is contained in other CSO guidance manuals. EPA recommends that
the permit writer obtain all of the CSO guidance manuals listed previously and use them in
conjunction with this manual during the development and issuance of permits.

1,6    ORGANIZATION OF MANUAL
       Chapter 2 presents an overview of the approach to CSO permitting as envisioned by the
CSO Control Policy. The chapter explains the responsibilities of NPDES permitting authorities,
setting of permitting priorities, and various strategies available to EPA Regions  and States for
ensuring that the CSO Control Policy objectives are  met.  Chapter 3 presents guidance on and
example permit language for developing initial (Phase I) permit requirements for implementing
minimum technology-based control measures and initiating the development  of long-term  plans
for CSO controls.   Chapter 4 provides the  procedures, requirements,  and example permit
language for the second round (Phase U) of CSO permits, which implement the selected  long-
term CSO  control measures. Chapter 5 discusses  the development of post-Phase II permit
requirements, including completion of the construction and implementation of the long-term CSO
controls, as well as post-construction monitoring.  The manual concludes with  appendices,
including  a compilation  of example  CSO permit  conditions  and suggested  checklists for
evaluating the  NMC and LTCP.
                                          1-7                              August 1995

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                                     CHAPTER 2
                      INTRODUCTION TO CSO

       The Combined Sewer Overflow  (CSO) Control Policy provides a national strategy for
the control of CSOs.  It presents a uniform, nationally consistent permitting  approach that
should, for the first time, result in the establishment of both technology-based and water quality-
based requirements for all CSOs.  Although the permitting approach envisioned  for CSOs still
fits into  the  regulatory structure of the National  Pollutant Discharge Elimination System
(NPDES) program at 40 CFR Part  122 and is similar to the permitting approach that most
NPDES permit writers are familiar with and have routinely employed for other point source
discharges, it is unlike the conventional NPDES permitting  approach in many ways.  This
chapter is designed to provide the permit writer with a clear understanding of the approach for
controlling CSOs that is envisioned by the CSO Control Policy. The remainder of this guidance
manual is designed to provide the permit writer with a more detailed understanding of how to
integrate CSO controls into the NPDES permitting process.

2.1    OVERVIEW OF CSO
       The CSO Control  Policy envisions  that CSO control requirements typically will be
implemented  through NPDES permits.  Generally,  NPDES permits include both technology-
based and water quality-based effluent limitations.  In the absence of national effluent guidelines
for CSOs, the CSO Control Policy envisions that technology-based controls (i.e., best  available
technology economically achievable/best conventional pollutant control technology) will be
established on a case-by-case basis using the permit writer's best professional judgment  (BPJ)
and be expressed in the form of best management practices. The technology-based controls will
include,  at a minimum, the nine minimum controls (NMC) as determined on a BPJ basis by the
NPDES  permitting authority. In addition, the CSO Control Policy recommends that, initially,
water  quality-based  effluent limits be  expressed in the  form of  narrative  requirements and
performance-based standards for the combined sewer system (CSS).   Ultimately,  the  water
quality-based effluent limits may also be expressed as numeric effluent limits  when data are
sufficient to support  their development.

                                          2-1                              August 1995

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Chapter 2                                              Introduction to CSO Permitting

       The CSO Control Policy expects that CSO controls will be incorporated into NPDES
permits in a two-phased process.  A Phase I permit will require the permittee to implement the
NMC, which are technology-based effluent limits as determined on a BPJ basis, and to document
that this requirement has been met.  The Phase I permit will also  require the permittee to
develop a  long-term control plan (LTCP).  The U.S. Environmental Protection Agency (EPA)
expects that implementation of the NMC during Phase I will achieve an interim level of CSO
control during the time the permittee is developing an LTCP.  EPA expects that Phase I permit
requirements will be included  in NPDES permits, either as permits become due for reissuance
during the usual NPDES permitting cycle or. where appropriate, on an accelerated schedule
through the permit modification process.

       The Phase II permit typically will be the next permit issued after the Phase I permit.  In
Phase II, the permittee will be required to implement the CSO controls identified in the LTCP.
Typically,  water quality-based  controls will be  expressed as  performance standards,  and
technology-based controls will be  the NMC,  which  may  be refined  to reflect site-specific
conditions. Whereas Phase I typically continues for only one permitting cycle. Phase II might
continue for several cycles until all selected CSO controls identified in the LTCP have been
constructed and implemented.

       Although the two-phased approach may be appropriate if a permittee has not implemented
any CSO controls, in many instances,  the separation between permit phases may not be distinct
and permits may contain both Phase I and Phase II elements. For example, a permittee may
have already evaluated and selected CSO controls for a portion of its CSS but not evaluated and
implemented the appropriate NMC. Thus, the next permit may include  the Phase I requirement
to evaluate, implement,  and document the implementation of the NMC  and may also include a
Phase II requirement to implement the selected CSO controls.   The  CSO Control Policy is
designed  to accommodate these variations in the  development and implementation of CSO
control programs.
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Cfegpter'2      	Introduction to CSO Permitting

       After the selected CSO controls have been implemented, the NPDES permitting authority
should Issue the post-Phase II permit.  This permit should generally  contain requirements to
continue NMC implementation, properly operate and maintain the completed CSO controls in
accordance with the operational plan, and implement the post-construction monitoring program.

2,2                       OF
       The permit writer plays a critical role in the CSO permitting process, one  that differs
from the NPDES permit writer's traditional role in several important aspects.  First, the permit
writer  plays a coordination role comparable to that of a team leader.   In setting permitting
priorities and facilitating the development of CSO permit requirements,  the permit writer has the
opportunity to develop a broad base of support for the CSO planning process and proposed CSO
controls.  The permit writer should serve  as the focal  point for coordination with  State WQS
authorities  and should also work with enforcement authorities, as appropriate,  to  incorporate
compliance schedules into enforceable mechanisms.  The permit writer  will also coordinate with
local agencies, environmental groups, and other interested or CSO-affected members of the
public.

       The second difference is  that the CSO permit writer's role is ongoing.  Even after the
issuance of the  Phase I permit,  the permit writer  should continuously  review  interim LTCP
deliverables and other submissions, participating in the ongoing consensus-building process, and
developing and preparing for the issuance  of Phase II permits.

       The permit writer may also be able  to assist communities in coordinating aspects of their
CSO control programs with each other. This might be particularly beneficial for adjacent small
communities discharging to the same receiving water. These communities might save significant
resources by coordinating the characterization of their sewer systems and monitoriBg of the  CSO
impacts on the receiving water quality rather than pursuing these activities independently.   The
permit writer may encourage community coordination by advising adjacent communities of their
mutual interests and opportunities for coordination.
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                                                         Introduction to CSO
2.3    CSO                              AND
       In response to the 1989 EPA National Combined Sewer Overflow Control Strategy, 30
States have received approval  or conditional approval for CSO  permitting strategies.  These
strategies usually provided a priority-setting plan for CSOs.  EPA expects States to evaluate the
need to revise their CSO strategies for consistency  with the 1994 CSO  Control Policy.  This
represents an opportunity for NPDES permitting authorities to reconsider their CSO permitting
priorities in light of current or suspected environmental impacts, watershed permitting initiatives,
and other factors.   States and EPA Regions should review these  strategies and  establish
appropriate permitting priorities for implementation of the CSO Control Policy.

       In  establishing  CSO permitting  priorities,  the  NPDES permitting authority should
consider factors such as the environmental impacts of CSOs (e.g. , beach closings, human health
hazards, and potential risk to endangered species). The NPDES permitting authority should also
consider requiring immediate action  for CSOs to areas that meet the CSO Control Policy's
definition  of "sensitive areas,"  To  assist NPDES permitting authorities in establishing CSO
permitting priorities consistent with the  CSO Control Policy, EPA developed the Combined
Sewer Overflows—Guidance for Screening and Ranking (EPA, 1995c).  This document provides
guidance on establishing permitting priorities for CSSs and provides permittees with a tool for
prioritizing individual CSOs within their CSSs to allow for effective allocation of resources.

       EPA encourages States to use a watershed approach to  set permitting priorities. Under
a  watershed approach,  all  surface  water,  ground water,  and  habitat  stressors  within  a
geographically  defined area are understood and addressed hi a coordinated fashion,  as an
alternative to addressing individual pollutant sources in isolation.  To support States that want
to implement a comprehensive statewide watershed approach, the Office of Water has developed
guidance and training designed to assist communities and natural resource agencies that are
pursuing a watershed approach. One part of this effort is the release of the NPDES Watershed
Strategy.  This Strategy encourages NPDES permitting authorities to evaluate water pollution
control needs on  a watershed basis and to coordinate CSO control program efforts with other
point and nonpoint source activities within the watershed.

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Chapter 2                          	      Introduction to CSO Permitting

       Applying a watershed approach to the CSO control program is particularly timely and
appropriate since an ultimate goal of the CSO Control Policy is development of long-term CSO
controls that will provide for the attainment of WQS. Since pollution sources other than CSOs
are likely to be contributing to the receiving water and affecting whether WQS  are achieved, the
NPDES permitting authority needs to consider and understand these other sources.

       Total maximum daily loads (TMDLs)  provide  the basis  of equitably allocating cost-
effective controls on a watershed basis.  By  examining the contribution  of both point and
nonpoint sources, the TMDL process ensures better use of limited resources in achieving WQS.
To assist in the development of TMDLs for episodic, wet-weather events, EPA plans to publish
technical guidance for estimating TMDLs that address integration of steady state and episodic
point and nonpoint sources.

2.4    MECHANISMS FOR              CSO CONTROLS
       The CSO Control Policy envisions that, in most cases, CSO requirements and controls
will  be incorporated into a municipality's existing NPDES permit for its discharge from the
publicly owned treatment  works (POTW), much like  the incorporation of pretreatment and
sewage sludge requirements. CSO conditions may be incorporated into the NPDES permit in
several ways:   1) by including the conditions hi the permit during the next five-year permit
renewal cycle, 2) by modifying the permit for cause in  accordance with the criteria in 40 CFR
122.62(a) or (b)  (most  likely  through a major permit modification),  or 3)  by  revoking and
reissuing the permit for cause in accordance  with the criteria  in  40 CFR 122.62(b).  EPA
assumes that, in most cases, CSO conditions will be incorporated into NPDES permits through
permit expiration and reissuance during the five-year permit cycle, (This document assumes this
scenario  for  illustrative purposes.)  Unless the  permit writer  intends to incorporate CSO
conditions into an NPDES permit immediately,  the permit writer should inform affected parties
of the impending changes and encourage them to take steps to implement the  CSO  Control
Policy recommendations, especially the NMC.  voluntarily.
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Chapter 2                                               Introduction to CSO Permitting

       EPA recommends that the permit writer integrate CSO conditions into an existing NPDES
permit in one of two ways.  The CSO conditions can be grouped together and contained in a
separate section  of she NPDES  permit  the  same  way  that sewage  sludge or pretreatment
requirements are  often placed in a separate section.  Appendix A illustrates how CSO conditions
can be grouped together in a separate section of an NPDES permit.  Alternately, individual CSO
conditions can be integrated into  separate sections of the NPDES permit.  For example, CSO
conditions can be integrated into the effluent limitations,  monitoring requirements,  and special
conditions sections of the  permit, as appropriate.   Exhibit 2-1 contains  an overview  of the
categories of CSO permitting conditions,  which are discussed throughout the manual.

       Other tools are available to the NPDES permitting authority in cases where the NPDES
permit is not the appropriate mechanism  to initiate or require CSO control.  In some cases, it
might be necessary for the NPDES permitting authority to include the CSO conditions in an
appropriate enforceable mechanism.  An  enforceable order can be issued,  either independently
or in conjunction with an NPDES permit,  when a permittee cannot comply immediately with the
terms of the NPDES permit and compliance dates have passed.  For example, an enforceable
order that requires compliance with the NMC (and submittal of appropriate documentation) no
later than January 1,  1997, might be necessary in cases where immediate compliance cannot be
achieved.

       In addition, the NPDES permitting authority may request information on a community's
CSS under Section 308 of the Clean Water Act (CWA) (or State equivalent).  Much of the
example NPDES permit language can be incorporated into a Section 308 information request.

2.5
       In  the most common and simple case, a single system-wide permit is issued  for all CSO
outfalls from a single authority. For example, a municipality or a small sanitary,sewer authority
with one POTW treatment plant should be issued one NPDES permit that addresses requirements
for the POTW, as well  as for CSOs, storm water, sewage sludge, and a pretreatment program,
as appropriate.

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                                    Exhibit 2-1.  Categories of CSO Permitting Conditions
                TIME
                                                 Years after Phase I Permit Issuance
  NPDES Permit Requirement
            Phase I
            Phase II
          Post Phase II
A,   Technology - Based
• NMC, at a minimum
* NMC, at a minimum
* NMC, at a minimum
B.   Water Quality-Based
* Narrative
  Narrative + performance-based
  standards
« Narrative + performance-based
  standards 4- numeric water
  quality-based cffluent limits (as
  appropriate)
C.  Monitoring
* Characterization, monitoring.
  and modeling of CSS
* Monitoring to evaluate water
  quality impacts

* Monitoring to determine
  effectiveness of CSO controls
  Post-cons!ruction compliance
  monitoring
D.   Reporting
» Documentation of NMC
  implementation

* Interim LTCP deliverables
  Implementation of CSO controls
  Report results of post-
  construction compliance
  monitoring
E.  Special Conditions
» Prohibition of dry weather
  overflows (DWO)

• Development of LTCP
* Prohibition of DWO

* Implementation of LTCP

* Reopener clause for WQS
  violations

* Sensitive area reassessment
» Prohibition of DWO

* Reopener clause for WQS
  violations

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Chapter 2                                                            to CSO
       If a large municipality or sewerage control authority owns and/or operates two or more
POTW treatment plants served by CSSs (also owned by the municipality) and each      has its
own NPDES  permit,  the  NPDES  permits generally  should  require  an integrated  and
comprehensive  approach  to  CSO  control.   This is  similar to  integrated  requirements for a
system-wide pretreatment program, where  one  municipality owns  several POTW  treatment
plants.  Each permit should be renewed, modified,  or  revoked and  reissued to  include CSO
conditions.  For example, if a municipality has  three POTW treatment plants with individual
permits that will be renewed in different years (e.g.,         plant A's permit will be renewed
in 1995, B's permit will be renewed  in 1996, and C's permit will be  renewed in  1997),
conditions addressing all  CSOs can. be incorporated into each permit  upon renewal.  To begin
the LTCP development process without having  to wait for all  of the permits to be reissued,
treatment  plant A's permit should address  CSOs  within the entire jurisdictional boundaries,
including the areas discharging to  treatment plant B and treatment plant C, and should require
development of an  LTCP for the entire system.  Correspondingly,  the NPDES permits for
treatment plant B and          plant C should contain the     requirements. As an alternative
in this same situation, the permit writer may choose to incorporate  aO  conditions addressing
CSOs only into the first permit to be reissued (i.e., treatment plant A's permit).  Incorporating
the CSO conditions into only one permit can preclude any confusion or inconsistencies resulting
from including  the      conditions in several different permits.

       In  some cases, different parts of a CSS, as  well as the treatment plant, might be owned
or operated by  different sewerage control authorities. In this situation, the permit writer may
issue each authority its own permit,'containing CSO conditions applicable to the portion of the
CSS owned or operated by that authority.   The  permits  should  require  synchronization,
coordinated preparation, and implementation of CSO controls among all authorities within the
CSS.  Each authority should be  responsible for its collection  system and CSOs and should
cooperate with the treatment plant permittee receiving the flows  from the CSS.  If a  CSS is
permitted separately from the treatment plant, the fact sheets for the different permits should
cross reference each other for informational purposes.  Alternately, the permit writer can issue
                                          2-8                              August 1995

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Chapter 2                                               Introduction to CSO Permitting

a single permit to all co-permittees,  incorporating CSO conditions unique to each CSS and
treatment plant.   Such  co-permittee  arrangements are  subject to consent by the respective
co-permittees,

2.6                OR ONGOING CSO CONTROL
       Some permittees might have already completed portions of the CSO control planning and
implementation process.  The CSO Control Policy recognizes these ongoing CSO control efforts
and does not expect duplication of effort.  If the permittee has 1) completed or substantially
completed construction of CSO control facilities that are designed to meet the water quality-
based requirements of the CWA, 2) substantially developed or is implement in*: a CSO control
program pursuant to an existing permit or enforcement order, and such program is considered
by the NPDES permitting agency to be adequate to meet the water qualt:> ha-^-d requirements
of the CWA, or 3) has previously constructed CSO control facilities in an eft -~ i.« comply with
water quality-based requirements of the CWA but has failed to comph JJK  ; remaining CSOs,
the permit  writer should take these efforts into account in determmin.-  »r ..f. nf the LTCP
elements are  still appropriate and  consistent  with the goals  of the  rv >  (  <;urol Policy,
However, such a permittee would still be expected to develop an LTCP  V,:, •:, ~<  5 3 presents
additional discussion of ongoing efforts.

2.7                                     IN            JURISDICTIONS
       The  CSO Control  Policy  recognizes that  the development and  implementation of a
comprehensive LTCP might be difficult or inappropriate for some small municipalities. At the
discretion of the permit writer, jurisdictions with total populations under ~5,UX) may  not need
to complete all of the formal steps involved in developing an LTCP.  Certain provisions of the
CSO Control Policy should not be waived, however, such as  implementation of the NMC, public
participation under  the LTCP, and sensitive  area considerations.   Although the CSO Control
Policy is intended to provide some relief for  small municipalities,  the permit writer should
discuss the  scope of the LTCP with the penniEee and the WQS authority to ensure that the
LTCP includes  sufficient  information to select appropriate  CSO controls.    Section  3.5.3
discusses considerations for smaller jurisdictions in greater  detail.

                                          2-9                              August 1995

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Chapter 2	   	Introduction to CSO Permitting

2,8                 OF
       As municipalities, NPDES permitting authorities, and the public embark on a coordinated
effort to address CSOs, serious considerations should be given to "measures of success."  For
purposes of this discussion, measures of success are objective, measurable, and quantifiable
indicators that illustrate trends and results over time.  Measures of success generally fall  into
four categories:

       •  Administrative measures that track programmatic activities;
       •  End-of-pipe measures that show trends in the discharge of CSS flows to the receiving
          water body, such as reduction of pollutant loadings, the frequency of CSOs, and the
          duration of CSOs;
       •  Receiving water body measures that show trends of the conditions in the water body
          to which the CSO occurs, such as trends in dissolved oxygen levels and sediment
          oxygen demand; and
       •  Ecological, human health, and use measures that show trends in conditions relating
          to the use of the water body, its effect on the health of the population that uses the
          water body, and the health of the organisms that reside in the water body, including
          beach  closures,  attainment  of designated  uses,  habitat improvements, and  fish
          consumption advisories,

EPA's  experience  has  shown that measures  of success should include a balanced mix of
measures from each of me  four categories.

       As municipalities begin to collect data and information on CSOs and CSO impacts,  they
have an important opportunity to establish a solid understanding of the "baseline" conditions and
to consider what information and data are necessary to evaluate and demonstrate the results of
CSO control.  Municipalities and NPDES permitting authorities  should agree early  in the
planning stages on the data and information that will be used to measure success and on the
extent to which the permit  and monitoring plan should include such indicators.

       The following list presents examples of potential measures of success for CSO control,
organized by the four categories discussed above:

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Chapter 2                                              Introduction to CSO Permitting
      *   Administrative measures:

             Number  of NPDES  permits  or  other  enforceable mechanisms  requiring
             implementation of the  NMC
             Number of NPDES permits or other enforceable mechanisms issued requiring
             development of LTCPs
             Number of municipalities meeting technology-based requirements in permits
             Number of municipalities meeting water quality-based requirements in permits
             Compliance rates with CSO requirements in permits
             Dollars spent/committed for CSO control measures
             Nature and extent of CSO controls constructed/implemented.

      •   End-of-pipe measures:

             Number of dry weather overflows eliminated
             Number of CSO outfalls eliminated
             Reduction in frequency of CSOs
             Reduction in volume of CSOs
             Reduction in pollutant loadings (conventional and toxics) in CSOs.

      •   Receiving water body measures:

             Reduced in-stream concentrations of pollutants
             Attainment of  narrative or numeric water quality criteria.

      *   Ecological, human health, and use measures:

             Improved  access to water resources
       •   -  Reduced flooding and drainage problems
             Reduced costs  and treatment of drinking water
          -  Economic benefits (e.g., value of increased tourism, value of shellfish harvested
             from beds previously closed)
             Restored habitat
             Improved biodiversity indices
             Reduction in beach closures
             Reduction in fish  consumption advisories.
       (Note:   These  measures  are  included as examples  only;  EPA is  supporting  the
       development of national measures of success for CSOs through a cooperative agreement
       with the Association of Metropolitan Sewerage  Agencies  (AMSA).  The results of

       AMSA's efforts are expected to be available in late 1995.)
                                         2-H                             August 1995

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Chapter 2	Introduction to CSO Permitting

       When establishing  CSO measures of success, municipalities and NPDES permitting
authorities should consider a number of important factors:
       •  Data quality and reproducibility—Can consistent and comparable data be collected
          that allow for comparison over time (e.g., trend analysis) and from different sources
          (e.g., watershed  analysis)?  Do standard data collection procedures exist?
       •  Costs—What is the cost of collecting and analyzing the information?
       •  Comprehenslbility to the public—Will the public understand and agree with the
          measures?
       •  Availability—Is  it reasonably feasible for the data to  be collected'*
       •  Objectivity—Would different individuals evaluate the data or inh»rmauon similarly,
          free from bias  or subjectivity?
       •  Other uses in  wet-weather and watershed planning and  management—Can the
          data be used by  State agencies  as support for other  CSC) arsJ watershed planning
          efforts?
       Careful selection, collection, analysis, and presentation of informal! •: rc.jtcJ to measures
of success should allow municipalities, States, and EPA to demonstrate t!u "vrKtii^ and long-
term successes of CSO control efforts.  Notwithstanding the effort u> tk\„, <:  rational measures
of success, municipalities should identify measures, document  baseline ... nJiu-mv and collect
appropriate information that demonstrates the cause and effect of CSO impja- and the benefits
and success of CSO control.  It is likely that measures of success \\ ill \an from municipality
to municipality and will be determined by the environmental impacts 01  CSOs on site-specific
basis.

2.9    COORDINATION WITH                 QUALITY STANDARDS AUTHORITY
       A primary  objective of the LTCP is  to develop and evaluate a range of CSO control
alternatives that will  be  sufficient to provide for the attainment of WQS, including designated
uses of CSO-impacted receiving waters.  To ensure  that the LTCP will meet this objective, the
WQS authorities, along with the NPDES permitting authorities, EPA, and the  permittee, should


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Chapter 2	Introduction to CSO Permitting

be involved throughout the LTCP development process.  This will enable everyone to have an
opportunity to review the proposed type and extent of data and information to be  collected
during LTCP development.  Such data and information should be used to assess the attainability
of the designated uses and might  assist States in more precisely defining the use(s) of the CSO-
impacted waters.  For example,  the information could be used to refine the existing WQS to
reflect the site-specific wet weather conditions for CSO-impacted receiving waters.  The CSO
Control Policy recognizes that the review and appropriate revision of WQS is, in many  cases.
an integral part of LTCP development.

       The CSO Control Policy discusses several types of WQS revisions in the WQS program
that potentially could be used to address wet  weather conditions.  These types of  revisions
include the following:

       *   Development of site-specific criteria
       •   Modification  of a designated use to include a partial use reflecting situations  where
          a certain event (e.g., a storm) precludes the designated use from occurring
       •   Modification  of a designated use to define the use with greater specificity (e.g., warm
          water fishery in place  of aquatic  life use protection)
       •   Temporary variances from water quality standards.

       These mechanisms are described in detail in the Combined Seiver Overflows—Questions
and Answers on Water Quality Standards and the CSO Program  (EPA, 1995h). The decision
regarding the mechanism to pursue when considering the  WQS  revisions will be  based on a
variety of factors.  Thus, the permittee should consult with the NPDES permitting authority and
State  WQS personnel to determine the most appropriate option.

       Data needs, monitoring protocols, and models to be used for system characterization and
compliance monitoring should be agreed on early in the process.  The water quality impacts of
the existing CSOs can then be evaluated to establish a baseline,  which can be used to assess the
effectiveness of CSO controls once they are  implemented.  These models and protocols can also

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Chapter 2	Introduction to CSO Permitting

be used lo predict whether WQS are likely to be attained after the LTCP has been implemented.
The information and data collected should assist States in assessing the need for revising WQS
and implementation procedures to better reflect site-specific impacts of CSOs.   In addition,
coordinating the LTCP development and the review and revision, as appropriate, of WQS and
implementation procedures should  ensure  that the permittee's LTCP  and  the  requirements
included  in the  NPDES permit will be sufficient to comply  with the water  quality-based
requirements of the CWA.

       Any review and revision of WQS to reflect wet weather conditions should be conducted
with full participation of stakeholders within the affected watershed.  This should include the
sharing of CSO, storm water,  and other point and nonpoint source  data among  stakeholders.
This will enable NPDES permitting authorities and permittees to implement a comprehensive
watershed management approach and allow permittees to  coordinate  the development and
implementation of their individual LTCPs with one another.
                                         244                             August 1995

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                                    CHAPTERS
                              PHASE I PERMITTING

      Consistent with the Combined Sewer Overflow  (CSO) Control Policy, the National
Pollutant Discharge Elimination System (NPDES) permitting authority and the individual permit
writer should approach the CSO permitting process as  a two-phased process.  This chapter
provides guidance on developing and issuing initial or Phase I NPDES permits for CSOs,  In
particular, it discusses how  to develop permit conditions  for implementation  of the nine
minimum controls (NMC) and development of the long-term control plan (LTCP) to meet the
technology- and water quality-based requirements of the  Clean Water Act (CWA).

3.1   PHASE I PERMIT PROCESS
      The Phase I permit should require the permittee  to immediately implement the NMC,
document implementation of the NMC, and develop the LTCP. The Phase I permit should also
require  the permittee to gather data to establish the baseline conditions against which CSO
controls will be measured.

3.2   INFORMATION NEEDS
      In general, the permit writer can draft and issue a  Phase I permit with a minimal amount
of CSO  information, because he or she can require the implementation and documentation of the
NMC and development of the LTCP without site-specific data in a generic manner,  Much of
the data collection should occur during implementation  of the NMC and development of the
LTCP, and the Phase I permit will contain requirements to obtain those data.  Although the CSO
information  base might not be extensive at the outset of the Phase I permitting process, the
information  base should  grow and evolve during the term of the Phase I permit.

       To draft and issue a Phase I permit, the permit writer should have a clear understanding
of the jurisdictional boundaries and responsibilities for the combined sewer system (CSS). This
information is necessary to determine which NPDES permittees should  be  subject to CSO
requirements.  Generally,  where the CSS and publicly  owned treatment works  (POTW) are

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Chapter 3	Phase I Permitting

operated by a single municipality, the permit wiE be issued to that municipality.  Frequently,
however, the relationship is more complicated; several municipalities might own part of the CSS
but discharge to a single POTW treatment plant.  In this case, CSO permits may  be issued to
several different municipalities.

       In addition, the permit writer should have a thorough understanding of the permittee's
past and current progress toward controlling CSOs.  First, the permit writer should know which,
if any, of the NMC have already been implemented. If any of the NMC have been implemented,
the permit writer may determine that site-specific rather than generic permit language is more
appropriate for continued implementation of those minimum controls.  (See Section 4,4.2 for
a discussion of site-specific permit language for the NMC.)  The permit writer should also know
whether the permittee has substantially developed a CSO control plan, is implementing a CSO
control program, or has substantially completed construction of CSO control facilities.  If the
permittee has completed efforts to control CSOs, the permit writer should consider  mis progress
when drafting the Phase I permit,  (Section 3.5,3 provides more information on addressing
ongoing CSO control efforts).

       The permit writer should also know the approximate population of the community served
by the CSS.  If the CSS serves a population of less than 75,TOO. the permit writer may give
special consideration to the permittee in developing the LTCP.  (Section 3.5,3 provides more
information on small system considerations.)

       In some instances, pertinent CSO information might be difficult to obtain. In any event,
the permit writer should, using readily available information, develop permit conditions requiring
the permittee to implement the NMC, document NMC implementation,  and develop the  LTCP
as soon as practical.

        Information may be obtained from  the NPDES permit application or through informal
requests by letter, telephone, or in-person visits. In a limited number of cases, the permit writer
may use a more formal mechanism, such as a  CWA  Section 308 information request or State
                                          3_2                              August 1995

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Chapter 3      	Phase I PemtMng

equivalent.  The Section 308 information request is likely to be an effective approach to obtain
information because failure to comply with a Section 308 information request may result in an
enforcement action. The permit writer should follow the EPA Regional or State-specific policies
regarding such information requests.

3.3    IDENTIFICATION OF CSO OUTFALLS IN THE PERMIT
       The  permittee might not have identified the locations of all CSO outfalls prior to the
issuance of the Phase I permit, although this is a desirable goal.  To the extent that the CSO
outfalls are  known, the permit writer should list them  in the permit.   If the exact location and
number of all outfalls are not known, however, the permit writer should not wait to issue the
Phase I permit until this information is available but should include generic permit language to
encompass all CSOs.  All CSO outfalls should be identified as the municipality characterizes its
CSS during LTCP development.  Exhibit 3-1 provides example permit language for a CSS for
which all CSO outfalls are not known prior to issuance of the Phase I permit.  The permit writer
should evaluate this language carefully to ensure that it is appropriate for the permittee.
       Exhibit 3-1.  Example Permit Language for Identifying CSO Outfalls in the
                                    Phase I Permit
  He permittee is authorized to discharge,from the CSO outfalts listed below and additional CSO outfalls
  within the boundaries of the permittee's jurisdiction identified after the effective date of the permit. The
  permittee shall ensure thai all CSOs from the CSS comply with the requirements of [Insert appropriate
  permit $eetion(s) containing CSO requirements] and other pertinent portions of this permit.
    ,  -•  "Outfall Number  •  •.   •••K-.   .Overflow^Outfall	Location    :\;,   Receiving Water Body
      -   [insert number}  "   •:-^.^j.:-': [insert latitede/loiigitode    ;;i"' :...^;;^  tiasert name of
         "•  .. ''   '   '   '• ••   ;f;f|-Ki (street address optional)]    :  '  ''^'receiving water-body}"
3.4    NINE MINIMUM CONTROLS
       The Phase I permit should require all permittees to immediately implement technology-
based requirements (best available technology economically achievable (BAT)/best conventional
pollutant control technology (BCT)) which, in most cases, are expected to be the NMC, as
determined on a best professional judgment (BPJ) basis by the NPDES permitting authority. The
NMC are controls that are designed to reduce the magnitude, frequency,  and duration of CSOs

                                           3.3                              August 1995

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Ctopter 3	^	Pirns e I Permitting

and  their effects on  receiving water quality.   Typically, they do not require  significant
engineering studies or major construction and can be  implemented  in a relatively short time
period.   Section 301 (b) of the CWA requires immediate compliance with technology-based
controls (i.e., BAT or  BCT). Thus, if immediate compliance with the NMC cannot be achieved,
an  appropriate enforceable mechanism should  accompany the permit.   The  enforceable
mechanism should contain a compliance schedule for implementing the NMC as  soon as
practicable, but no later than January I, 1997.  (See Section 3.4.1 for more detail.) Section 2.4
describes additional mechanisms for implementation of NMC in cases where the permit is not
expected to be reissued in the normal five-year cycle prior to January I, 1997.

       The NMC are  intended to provide technology-based controls, applied on a site-specific
basis, that will immediately reduce CSO impacts on water quality and that can be implemented
early in  the control process without  the type of in-depth  studies  necessary for the LTCP.
Exhibit 3-2 lists examples of NMC measures. Section 3.6 further discusses the use of the NMC
to satisfy the  BAT/BCT requirement on a BPJ  basis.  The U.S.  Environmental Protection
Agency (EPA)'s Combined Sewer Overflows—Guidance for Mne Minimum Controls  provides
a detailed description  of each minimum control, example measures for each control, and their
associated advantages  and limitations (EPA, 1995b). Although the permittee will be responsible
for implementing technology-based control measures that satisfy each of the NMC, EPA does
not expect that a separate set of control measures will necessarily be required for each control
Rather, EPA encourages a holistic approach to addressing the NMC. For example, the same
control measure(s) could satisfy both "Control of  Solid and Floatable Materials"  and "Pollution
Prevention."
                                          3.4                              August 1995

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                                     Exhibit 3-2.  Summary of the Nine Minimum Controls
 Minimum Control
Proper Operation
and Maintenance
Maximum Use of
Collection System
for Storage
Review and Modify
Prctrcatment
Requirements
Maximum Flow to
the POTW for
Treatment
Eliminate Dry
Weather Overflows
        Examples of Control Measures
   Maintain/repair regulators
   Maintain/repair tidegates
   Remove sediment/debris
   Repair pump stations
   Develop inspection program
   Inspect collection system
  Maintain/repair tidegates
  Adjust regulators
  Remove small system bottlenecks
  Prevent surface runoff
  Remove flow obstructions
  Upgrade/adjust pumping operations
Volume Control
* Diversion storage
* Flow restrictions
• Reduced runoff
« Curbs/dikes
Pollutant Control
•  Process modifications
•  Storm water treatment
«  Improved
  housekeeping
•  BMP Plan
  Analyze flows
  Analyze unit processes
  Analyze headloss
  Evaluate design capacity
  Modify internal piping
  Use abandoned facilities
  Analyze sewer system
  Perform routine inspections
  Remove illicit  connections
  Adjust/repair regulators
  Repair tidegates
  Clean/repair CSS
  Eliminate  bottlenecks
                            Minimum Control
                            Control of Solid
                            and Floatable
                            Materials  in CSOs
                            Pollution
                            Prevention
Public Notification
                           Monitoring
                            '' Examples of Control Measures
                      Screening - Baffles, trash racks, screens (static and
                      mechanical), netting, catch basin modifications
                      Skimming - booms, skimmer boats, flow balancing
                      Source controls - street cleaning, anti-Sitter, public
                      education, solid waste  collection, recycling
                      Source controls (see above)
                      Water conservation
Posting (at outfalls, use areas, public places)
TV/newspaper notification
Direct mail notification
                      Identify all CSO outfalls
                      Record total number of CSO events and frequency
                      and duration of CSOs for a representative number
                      of events
                      Summarize locations and designated uses of
                      receiving waters
                      Summarize water quality data for receiving waters
                      Summarize CSO impacts/incidents
                                                                                                                                                  I

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Chapter 3                                                           Phase 1 Permitting

       Implementation of the NMC should enable the permittee to achieve an intermediate level
of CSO control while the LTCP is being developed.  Implementation and documentation of the
NMC should involve the following steps:
          Evaluate alternative control  measures for  implementing each of the NMC.  The
          permittee should be required to evaluate alternatives and select appropriate control
          measures to meet the NMC.
          Implement the most appropriate control measures. The permittee should be required
          to implement those control measures  that  are most  appropriate for the site.  The
          control  measures should be  refined  in Phase  II,  as appropriate, to reflect the
          information obtained during the Phase I permit term.  These control measures should
          eventually become  part of the long-term CSO control program.
          Document implementation of the selected  control measures.  This documentation
          should detail the baseline conditions prior to NMC implementation, the permittee's
          evaluation of the efficacy of CSO controls after implementation of the NMC, the
          baseline conditions upon which the LTCP  should be  developed, and the degree to
          which  the NMC are  sufficient to provide attainment of water  quality  standards
          (WQS).
          Report on implementation.  The permittee  should be required to submit appropriate
          documentation to illustrate implementation of the NMC (discussed in Section 3,4.2).
3.4.1  Implementation Considerations
       Because the compliance date contained in the CWA for technology-based requirements
has lapsed, the permit writer should require the  NMC to be implemented immediately.  When
the permittee cannot comply with such permit conditions, the permit writer should coordinate
with enforcement authority staff to prepare an enforcement order,  including a compliance
schedule with fixed dates.  In accordance with  the CSO Control Policy, the NMC should be
implemented  with  appropriate  documentation  as soon  as  practicable,  but no  later than
January L 1997.

       Exhibit 3-3 provides example permit language  requiring  implementation of the NMC.
The permit writer should evaluate this language carefully to ensure that it is appropriate for the
permittee.  The permit writer must also prepare a fact sheet or statement of basis associated with
the implementation of the NMC.  The permit writer must show that the permittee's NMC satisfy

                                          3-6             "                 August 1995

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Chapter 3
                                                                                  Phase I Permitting
  Exhibit 3-3.  Example Permit Language to Require Immediate Implementation of the
                                      Nine Minimum Controls
L  ' Effluent I4auts            :'"''/'   '.•'.•          .-
A. Technology-based teipikeineEnte for CSQs. 'The -permittee
   recpiremenis:      '           '.  •,":•' ..  • '     •         .•     V  s    .  '.*••       .  <
.  ..I. The -permittee- Mall inipfeiiientpraipero^                                                       •  . •
      GS0 outfalls- to reduce the jnajpihude^.ix'equeacy, and" deratfen.-Of CSOs,. , The. program shall consider- . • .  . •
      ' regular sewer " inspectioBs;: *wer , • caieh. basin, and t egulitor-deaaaig; «pipjnem asd se wer collection •
    •  systtm.:«pak Qr-repiaee«itt, :where necessary; and. diaofflwciofetiflllegatcoBnections.         ; " ' ''"
   2. lliue pejtxaidee-sh^jinpleira                                                system for wasiewattr.
   . .  -.storage -that can- fce-a&coi&mqditted:- by 'the- storage capacttpibf tbe;':coileetioi! system in order to reduce the
      magnitude,, feqneney, -and dtestisiwrf CSQs.       •   V/:::'-vi  .----•                     •
   3, 1Tie-;-.per!3ppee shall' review and modify, 'as'.i^ropriatB, iis;-e3dsting..ptetreaHnent prop rim  iv minimize CSQ
      impttB: ftom te dfec}jatjes--froiii:-B0iKlotisestic esers,   ;:    : • ;.                                 ^
  :    ' [AJteraativg iauguage for a jpsermirtee without an approved pretreatmeut program:) Tht  permittee -shall
      evaluate the CSO impacts: from 'aondomesttc. users aml^take-Jippiopriate steps 10 miRinn.'t  suvh impacts. ,^  .
   -4. The- 'peooitiee- shall operate  t3fe'P0TW treatment plant -at maximum tttaable flew  ju-ir.-  *!;
   -   fl(jw--:coHd!tions. to reduce the-raSfnitude, .frequencyi, and.duration:,-:0f'CSOs. the pcrnntus-
•   ..   •Qogws --to- the treatment plant ••within: the •<»iistraiiitsofte,tteasnjeat^catpacmi ol UK f-nru
   5.' Dry- weather overflows -from: CSC) 'outfalls.: ajfc'proMbitefl, 'Each dry weather i«crfi •». n-.- be ftrHjrted to-
 - -    the.,i»rMtfiag:-.atttbot%;aS-SC»a^-flie:pecnfittee-be«^
      detects a- diy weaflser 0verfl6writt».peiBiktee shaft begin ooirtaive action imnK-u
      shall 'itt^eiet fi»-«iry -weather.. overfiow :.e.aic.h sufesejpeaf'day «wM-;flie ovcrflfw. h4
  -• 6, The penoittee shall -'implement measires to control 'solid and floatable matem;- a  c**> *
  - 7, The petmittte shall impIeiBent4"|»ltoUion-pre»aMiQn-prograiB'.locused on rcJu, ir   tii-  >r;tf **t «•! CSOs on
     . ^receiving -waters.      .'     :"- "'  '•'''..'.
   8. The 'p^Etoinee shall iinplem^ffi.s-puWic'«ottHcation.proc«s;td iafonn citizen*. «•: »u • *-•»• »ttrrr CSOs ^
      •occar;  -The process' must include- (a) a mechanism to alertpersons of the rtuurrr!* - •: C  s >. jinJ (b) a '•- .
 ''"' '   system to determine- the aature and duration of -.conditions' 'tot are potentialK h*rm*i. t f  u^rr^ n( receiving
                   GSOs. '    .   ;-  ' ";"  -    :- -  .
                                                                                              weather.
                                                                                             deliver all
                                                                                      ui» permittee
                                                                                       T"hc fcrmmee
                                                                                       ;tr:ruicd.
     9, Thspsxmjttst ^^mammt-CSQ:Og^i^::W-cliXxtma&O-mp^ctsaRd tiv. ctu.j.t >i- TSft controls'.
        "Ms •shall/include collection. of daa fliai 'will be. used to; documettt the existing hjvlin? <•> -nJitions. evalaate-
      "the. efficacy: of the -JectooIogy-based.controis.'and-detBnriHJtthe -baseline conJiti<'.oiit&)Is'inttie CSS"'  ''   -.;••'                                 "''
        'b. Total number of CSO evenls-'asid-'fc.-.freqiKncy-'and:di!fadon. of CSOs for a representative number of  ''" ^
        ' --events  •              '            !1-          '      ..       •'"                           -= -5': :f"
        c. Lec-arioas aaid designated uses:of-receiving.watet-bodies'     •.''•'.:;;  .                      .-$-£
        d. Water qualiy data for/receiving:' water -bodies- •      •'-.-...>..:•    -                      :^:!ii  •
        e. 'Water quality- impacts..Jdtrecfly- related to-CSOs (e.g., beach'qloskg,'featables wash-up episodes, fish ';'^;
         ''kills),'      ;,         :     -:;::'-:    :'-   '•'     .  '   .  :-'..-';.:         -     ';           ;.    ^
                                                   3-7
                                                                                          August  1995

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Ctuyter 3	      '	^	Phase 1 PermMng

the BAT/BCT requirements based on BPJ of the permit writer, considering the factors presented
in 40 CFR  125,3(d).  These  factors include the age of equipment and  facilities involved.
engineering  aspects  of the application  of various types  of control  measures, and the
reasonableness of the relationship between the costs of attaining a reduction in effluent and the
effluent reduction benefits achieved. The Training Manual for NPDES Permit Writers contains
additional details on the use of BPJ in developing permit conditions (EPA, I993g).

       When the permittee is already implementing some or all of the NMC, the permit writer
should customize  the permit language to address site-specific conditions.  For example, if the
permittee is  already implementing an operation and maintenance (O&M) program, the permit
writer  might craft language that specifically addresses CSS inspection frequency,   If the
permittee is already controlling solid and floatable materials, the permit writer may augment the
general language to address the specific controls being implemented.  Where the permittee has
already selected long-term CSO controls, the permit writer should coordinate the development
of the permit language requiring NMC implementation with implementation of such controls.
This is because some of the control measures might not be appropriate when the selected long-
term CSO controls have been implemented (e.g., if a CSO outfall is being eliminated). Section
4.4.2 addresses potential site-specific permit conditions in greater detail. Most importantly, the
permit writer should ensure  that  the  permit language reflects the permittee's  site-specific
conditions, is consistent with the CSO Control Policy, and is enforceable.

       It  is important to  note some  additional implementation considerations pertaining  to
specific minimum controls:

       Pretreatment:  In the case where the permittee does not have an approved pretreatment
program under 40 CFR Part 403, the permit writer should require the permittee to identify  its
nondomestic users, evaluate the impacts of such users on CSOs, and take steps, as  appropriate,
to minimize these impacts within the CSS "up-pipe" of the CSOs,  Alternative language for this
situation is presented in Exhibit 3-3.
                                          3-8                              August 1995

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Chapter 3	^	Phase I Permitting

       Maximizing flow: In developing a permit condition for maximizing flow to the POTW
for treatment, the permit writer should consider the secondary treatment regulations in 40 CFR
Part  133, which specify numeric  effluent limits for biochemical  oxygen demand and total
suspended solids, as well as a minimuin percent removal (85 percent) for secondary treatment.
Secondary treatment requirements are enforceable conditions in POTW permits.

       Section 133.103(a) and (e) provides relief for POTWs with CSSs that process elevated
flows (and more dilute influents) by allowing for the possibility of a waiver of the percent
removal requirement.  Waivers from effluent concentration limits are not available, however.
The decision to apply a waiver and the recalculation of the percent removal are made on a case-
by-case basis.
                                                       i
3.4,2  Documentation and Reporting
       The Phase I permit should require the permittee to submit documentation demonstrating
the implementation of each of the NMC. The CSO Control Policy recommends that the NPDES
permitting authority require this documentation to be submitted as  soon  as practicable but no
later than two years after permit issuance.  The purpose of the documentation is to 1) verify that
the permittee has evaluated, selected, and implemented CSO controls for each of the NMC,
2) document the existing baseline conditions, evaluate the efficacy of the CSO controls after
implementation of the NMC, and determine the baseline conditions upon which the LTCP should
be developed, and 3) evaluate the  degree to  which the NMC are sufficient to provide for the
attainment of WQS.

       The permit should  require the permittee to  document and report the evaluation and
selection of the most appropriate control(s) for each minimum control.   Exhibit 3-4 presents
example  permit language requiring such documentation.  The permit writer should evaluate this
language carefully to ensure that it is appropriate for the permittee.  Exhibit 3-5 and EPA's
guidance for nine rflinimum controls (EPA, 1995b) contain examples of NMC documentation.
The  permit writer should review the example types of documentation in Exhibit 3-5 and the
NMC guidance document and  choose the appropriate items to be required in the permit. NMC

                                         3-9                             August 1995

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Chapter 3                                                            Phase I Permitting
  Exhibit 3-4.  Example Permit Language for Requiring Documentation and Reporting
                            of the Nine Minimum Controls
 II, Reporting Requirements  v'       '  ..:-•-., •--     ,:  ,     "    /•      _      :*   ^    ^  ^jv..;
 A, Reporting implementation^of nine..imnimiiffl .controls." The permittee shall submit documentation that
    demonstrates implementation of each of the nine minimum-controls thai; includes the elements below. The
  :: permittee shall submit this documentation to the permitting authority oa or before [Insert due date).
            ;::    :, "    [insert appropriate list of documentation items]          """    :
documentation may come in a variety of forms. For example, the permittee may submit reports
and studies prepared for other purposes, such as operating or facility plans, revised sewer use
ordinances, sewer system inspection reports, technical studies, and pollution prevention program
plans; public notification plans; and contracts and schedules for minor construction programs for
improving the existing system's operation.
       The documentation required in the permit should be the mimmutr am vjm necessary to
demonstrate that appropriate NMC measures are being implemented  tr .iJJm,*n. ihe NPDES
permitting authority may choose to require the municipality to  keep s.«nu-  ri\>»rJs of NMC
implementation on site rather than requiring all documentation to  he sutnr.nc-J  In these cases,
NPDES inspectors can review documentation that is on file during  m^pv»;i -n-

       Although not reflected in the example permit language in Exhibit *-4. the permit writer
may require periodic reports on the implementation of me NMC through. HI; the lerm of the
permit. For example, the permit writer may require updates on am Mcmd-ant chances in NMC
implementation.  In addition, the permit writer  may require the submission of monitoring data
at a specified  frequency throughout the term of the Phase I permit.   In am case,  the permit
language should reflect the permittee's site-specific conditions.

3.5    LONG-TERM CONTROL PLAN
       The second major element of the Phase 1 permit is the requirement to develop an LTCP
that will ultimately  result  in  the permittee's compliance  with CWA requirements.  For this
reason, the LTCP should contain CSO controls that are adequate to provide for the attainment
                                          3-10                              August 1995

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Chapter 3                                                                                 J
                     Exhibit 3-5.  Example Types of NMC Documentation
 Proper opsrattes and' regular mantteaanc* programs-   1l  •''  . .     "'" ;%. .   '   •

 An jroentory of CSS components requiring: routine operation and maintenance      ..    '• ' •
 An evaluation of opeiatiouxand maintenance procedures :te include regular inspections; sewer, eaiefs basin, .and •
  -  regulator cleaning; •and equipment, and-«wer polleetioa system repair or replacement .where necessary  ••. ,;;:;:;:
 Copy of, -or excerpts- from, -an operatioa-'and -maintenance manual and/or procedures lor .the-CSS- and CJSO  ."-
  -,  stfuctares  ?!-       •      ;':--  -      .      ' "      ......  - $t^-&   v          • '''        *       ...,•••.-'::•'•
 Resources allocated. (masqKJwer^. -equipment, trainiflg)"for"BjafaienaKe-of the CSS and CSO-stracaffes   ,,...   -
 A 'summary- of. iitspecDixascon^                                s         ,. $  \         lr,.;._.  '  ""; '
               of us® of the- sewer collection system for storage
 An -analysis/study of alternatives to maximize collection system storage           ,;••  '>'.  '"  '       . :.. •
 A 'descnqptibn-df procedures in place' -for -xoanondng cpiiectjon system storage     '•'•  ,  '"'  ',  -   ..   •"•'
 AJQ impleioeiiatioo 'schedule --of mioor-eonsaucnba associated with maximbdng collectioB system storage  . :
 Deseriprion.of-actions taken to .nuotunize. storage •    ''.•'•'.   I                 •; ;•    t-,  "       •  '•'"'•  ~
 Identifiettiottof odsting-off-lme storage potential-           .. :s                    .          -••-     >
 Ideatifcation- of %sy: additioual potential actions w- increase' storage in the existing coltectiou ^ittia^ but-tbat   •'• :
    require further-' analysis; do«mefltatiofl.-thai they 'will be/were evaluated in hydraulic- studies conducted as part
    oftheLTCP'   '   .    .::-:'. ":'-;"' -   i:        ••-:-••    ^^          '          ^   .._.   ^   ,;.-:,:-  -.

 Re?riew:aad'iiiodffi£stioBi;-'0f .controls' on 'nondomesfic- sources   ,i::;;:              ,  ',        '....-:-
                                                 .    .                                          ...
        of an inventory of nondomestic discharges aoad-aswssment of the impact of such discharges .on -CSOs-
 Analysis of -feasibility of modifications to nondomesdc source. controls (including local pretreaimeni program, if
   'appropriate} to reduce the impact of sucft- discharges on-.CSOs                  '3V..  ,      '   l  --:
               of selected modifications :-.      •  ' ..,.   s                            \   %!?;    •&.  '.  ' ,,.  ''".
 M«lni4rati«ffl, of flow .to-tbe'FOnrW-'treatnwDt plan* for. teeatment                 ,"" .^,-,  ;i
  :-:-,    •                 .''  '             <;•                     •' ;                  '   ^''-
 Results of 'any study/analysis' ftf existing condidom and a comparison with the design capacity of 'the
    facility  v,          '      '           -                   "'"                  *   ••-   -jif' '"•-   : """''"
 Results or status of any engineering studies to increase treatment of -wet weather flows      '>'''•
 Documentation, of actions taken to maxlouze flow 'and the-ntagnitade of increase obtained or projeettd   '    :

 Einsfaatt&H -®f CSOs dsMriiig:dry weather flsw.eeiiditioiB  _,,;;:                    <-.   ^     .  .   ,--::  ••-

 A summary of dry weitheir overflows that occurred, Inclading -location, dwration. and frequency'             . =
 A -de^ription of procedates- for.. notifying pennitdng; authority of dry weather overflows  .         s;-f   .;•  '•  "::
 A summary of actions taien to identify dry weather oyerfiows--and progress toward eliminating -dry weather  p-
    overflows   '"'  '"'       -    . '"'              -.-  . '"'  '   -- :':-                     K;:  ;                    !»},
 A plan- for eomplete- eluninatton .of afl dry weaiher overflows. s.;  :-:                    ?:'.  -1 'f';    -:   ••'•  -•••'

 ConttMil of solid and Itoaiable materials- in. CSOs           (    „,,           " ..... '""  $''f. * i9  '--'  ;:

 An engmeeiing' evaluation -of procedures or technologies censideted for controlling sold «nd -ftoaiable - materials
 A description of CSO controls in place for solid 'and floatable materials         •' j'    w.Xs; . ;     • H;-;- -
 A- schedule for minor constractipB       .  x    '<*••'       •             „%&$• *'''•  f^S " ^ly-^.   •  " --
 DocamentaMon of -any -additional controls to be inswUed or: implemented       :'"':'5''     :'       ' ''*,
                                                   3-11                                    August 1995

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Clwpter 3
                                                                       Phase I Permitting
            Exhibit 3-5,  Example Types of NMC Documentation (Continued)
Pofiuiien preveetton
                            to^
 An evaluation of pollution prevention opportunities to include procedures to coBire! solid arid floatable
   materials     ~              ..'",'              . .    _                   ;       =
 A description of selected pollution preveatioa ojspommlti.es to include resources allocated
 f^blfe notification •              '-" • ;              '•  ;  "           :   •  .-     '", •   ::-'
 An evalaatioa of public nctifieafioa options,: incfadifig descriptioa of existing and/or proposed' public
   aotificaiicia procedures '•  •            _                 ;                      •• /, • "' •
 A *teserijKl0n: of. Elected paMe tmtificatioii mefiiods      ..:...-,'.'    •    -        •  ' •'   '•''••
 A k>g of CSO . "'  . '-  '
                                                             _
 A summary of reeei^iag water impacts droxtly relaled to CSOs (e.g., beadi dosing, fioatebles
   '                                  "            "'"
                                                      .
 • An assessniect of the effectivei^ss of any CSO control mEasuies ;alread>' itaplemented (e.g., reduakia of
   floatable®)-             "       ••                      . .   • ,           '  ...    / .  .-•   •
 '              a nwmsoiiag plaa fcsr th<CP, w an>ropriate  '  ;      ,       :.
of WQS—that is, they will ensure tiaat designatel uses are not impaired and the State's water
quality criteria are not exceeded.  The CSO Control  Policy recommends  that the permittee
develop and submit the LTCP as soon as practicable but generally within two years after the
requirement to develop the LTCP is incorporated into a permit, Section 308 information request,
or enforcement action.  The CSO Control Policy also recognizes that it may be appropriate for
the permit  writer to establish a  longer schedule for completion of the LTCP based on site-
specific factors.

        The LTCP development process is a comprehensive planning effort designed to evaluate
a range of CSO control alternatives and result in the selection of CSO controls that will provide
for  the attainment of WQS.  For this reason, the LTCP development process will  be an
incremental and, frequently, a sequential process.  For example, a permittee should assess the
impacts of CSOs on water  quality prior to identifying  a range  of feasible CSO  control
                                            3-12
                                                                              August 1995

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Chapter 3	Phase I Permitting

alternatives.  In establishing the requirements to develop an LTCP, the permit  writer should
consider  the site-specific  conditions of  the  permittee.   In  a limited  number  of cases,
implementation of the NMC may be sufficient to provide for the attainment of WQS and the
permittee's efforts to develop an LTCP should appropriately reflect this situation.  In other
cases, the permittee may have already begun the CSO planning process and the requirement to
develop an LTCP should be tailored to reflect ongoing efforts.

       TMs section provides guidance for the permit writer on how to require development of
the LTCP in accordance with the CSO Control Policy.  Section 3.5.1 describes each element of
the LTCP,  Section 3.5.2 presents the schedule for development of the LTCP, and Section 3.5.3
discusses considerations for small systems and ongoing CSO control efforts.  EPA's Combined
Sewer  Overflows—Guidance for Long-Term Control Plan contains technical guidance on the
development of LTCPs (EPA, 1995a).

3.5.1  Components of the Long-Term Control Plan
       The CSO Control Policy outlines the following minimum LTCP components:

       *  Characterization, monitoring, and  modeling of the  CSS  and receiving waters
          (including identification of sensitive areas)
       *  Public participation
       *  Consideration of sensitive areas
       •  Evaluation and selection of alternatives
       *  Cost/performance considerations
       *   Operational plan
       *   Maximization of treatment at the POTW treatment plant
       »  Implementation schedule
       •   Post-construction compliance monitoring program.
                                         3-13                             August 1995

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Chapter 3	Phase I Permitting

       In general, the permit should guide the development of the LTCP consistent with the
CSO Control Policy, establishing distinct Incremental actions, providing the permittee with
flexibility  in conducting the planning process, and ensuring enforceability of subsequent Phase
II permit conditions.

       Exhibit 3-6 provides example permit language requiring the development of an LTCP,
This exMbit was  intended to provide practical, realistic example language which should not
necessarily be considered as boilerplate language.  Thus, the permit writer should evaluate this
language carefully to ensure that it is appropriate for the permittee.  The permit conditions in
this exhibit include all the components of an LTCP outlined  in the CSO Control Policy.  The
permit writer should list specific LTCP components in the permit rather than simply require the
permittee to develop an LTCP consistent with the CSO Control Policy. A permit condition such
as,  "The permittee shall complete and submit to the permitting  authority an LTCP by [date
specified]..." may result in the submittal of an incomplete or poorly developed plan.  Listing
the individual components of the plan requires the permittee to consider all  of the necessary
LTCP components.

       The public participation component of the LTCP is discussed first in this section because
it is important for the permittee to identify potential stakeholders and formulate a process that
will facilitate their active involvement in LTCP development. This should be done as early as
possible in the LTCP development process.

3.5.1.1   Public Participation
       Under the CSO Control Policy,  the  permittee should employ a public  participation
process that actively involves the affected public in the decision-making to select the long-term
CSO control(s).  According to the CSO Control Policy, the affected public includes rate payers,
industrial users of the sewer system, persons who live adjacent to or use water bodies affected
by CSOs, and any other interested persons.  Public participation  is critical to the ultimate success
of  the CSO controls selected  by the permittee, given the potential financial impact (e.g.,
increased fees) to the  affected public.   Early and  constant  public participation  during the

                                          3-14                              August  1995

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Chapter 3
Phase I PermMng
                          Exhibit 3-6.  Example Permit Language for
                  Requiring the Development of a Long-Term Control Plan
 III.  Long-Term Control Plan ';.      .  "', «:->•!     •   ,                                ,,'"''
 Tie permittee shall develop a long-term control plm thai will include the elements- contained in Sections fH.A
 through 111,0 below and shall-. submit the plan elements In accordance with, the schedule contained •& Section
 IILE:;-,    ^.,o: (                   .,    ^ • '  •'   J   s* *  .               *  ^    ^   ^  v. •••

 A, Public Participation •'•    ;,              "  ""  .     ., '" .^   ,,..      ••"  :        .= -:;;¥;??;     ^     x

    .The permittee shall prepare- and implement a public parttdpatJon. plan -'that outlines- "how the -permittee will
    ensure participation of .the public tturougiiout the', long-term. control 'plan- development process;.     • • . •
 B. CSS Characterization    . .   t"H":: 'A.;,    %    ,.   .      ^J^             '..      '..    H        . .   .

    The permittee shall develop- and .implement a plan that will -result 'in a c»mprefaensive characterization of
    the CSS developed through -.records - review, monitoring, modeling, and-- other  means as' appropriate to
    establish' the existing baseline conditions, evaluate the efficacy of the CSO technology-based controls^ and
   x determine  the '  baseline conditions  upon  which : -the- long-term 'opnttpl • plain wUl  be based.'  The
   , characterization  shall adequately address the response/of the' CSS to various precipitation events; identify
  ;£:' die-number, ItKaiion, .-frequency, .and dtaracleristlcs 'of CSOs;- and'Meatify water- qaaMty.. impacts- -that result
 :,):.  ficom'CSOs,   .  :S:,A    _  '     X4p'ii"-         r    -     -     -                 .*              ;;

    To complete .the chaiacterizatioQ., -the penaittee. -shall enip-loy the following methods;  liyi.         :

    1. Ra^al|JRe<»ras Review..- - 'The permittee shall examine the-complete.;rajnfell iwoids for .tte- geographic
   ,';          of tise GSS and evaluate the flow Variations, in the-recetving water' body-: to -correlate "'between the
   "' •'   CSOs and receiving, water conditions,         ";            .*.      ''•''_,,               :.
    2, .CSS Records.- Review. Tie permittee -shall review -and evaluate all -available CSS records and undertake
  .. ..  -'field -'inspections, and other -necessary activities -.to Identify 'the nsmbet, location,; and frequency  Of CSOs
    -.;•  - and their location relative to  sensitive -areas, (as identified 'i&..UI;B14).'and to pollution, sources, such-.-as
       significant indnstrial users, in -the. collection system.-   '        :.            ;     ---.-  • '-.j-' K
     3 . ' 'CSP^jnd^WjMerQ^ityJ^pjyitpjEfe^.  Tie-permittee shall develop .and submit a monitoriag -program tot
       ' measures the frequency, duration, flow rate, volume, and pollutant -concentration .'of CSOs and
    " • -the impact of the CSOs on .receiving waters. -Monitoring shall be .performed -at. a"' representative number
       o-f CSOs for a  representative number of events.- The "monitoruig ' program shall -include 'CSOs and
       . ambient receiving .water -body monitoring and,- where appropriate-, 'other -monitoring protocols, such as
       biological assessments, loxicity testing, and sediment. sampling. ,,'R           "   '•"-'•

     4, Identification of i: Sensitive; Areas. -The permittee -shall identify -sensitive areas to which its CSOs: -occur.
       These' areas shall taclwte Outstanding National -Resource Waters, •• National -Manne Sanctuaries, waters
       with threatened  orendangered species and 'their designated' critical.- habitat, waters with primary, contact
    .   recreation, public drinking water intakes or their designated, protection, areas, shellfish-" beds* and any
       j other areas. identified" by -the. permittee or permitting authority, in -coordination with appropriate -Sate or
    .4;- Federal agencies.   ,-.?:<     .         -;;        ......                        .:.;   •
     5, CSS ...aftd..Receiying WatCT,ModeUn.g.  The permittee -may employ  models,, which include appropriate
       calibration aad. verification with field  measurements, to aid in the diaracterizatioii. . If models are used.
     :f they shall be identified by the pennittee  -along w.ifh an  explanation of why- the model' was selected and
    "• used in the characterization.    ...     '-P  •„  ..       .     „.-'-.  .;-       r'    •            •     .
                                                 3-15
        August 1995

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Chapter 3                                                                       Phase I Permitting
                           Exhibit 3-6.  Example Permit Language for
           Requiring the Development of a Long-Terra Control Plan (continued)
 C.  CSO Control Alternatives.   '    , „.,..   -;v - >s        *.."'•'•'.           1   ., _         .        . I
     L  Development	of _CSQ	Control Alternatives, - '•• The permittee- shall  -develop a range of  CSO -control j
        -alternatives that would- bt necessary to achieve- [insert appropriate range: of levels  of cojittol ,. 'JpSf;.;  : ..    •          ?«
 D.  Selected CSO Controls'        p'  _,,/;£   -   '   ;'v           --    . •   . f:!l.j|:: lk£^ •  •'
     Once the 'permittee  has selected -the CSO controls  to:-consultation with  the pemutriag authority, the
    . permittee .shall submit-the foEowIng: *-      ;  -,   '                  - :-:"--,.  :;   .; .,
  :-   L. Implemeaiariofl .Schedule.-  The  permittee shall submit a construction, schedule for  the selected;CSO
    -   'controls as part of-the implementation schedule. ' Such schedules m&y be phased based oa- the -relative
    M '  impoftance-of the adverse impacts on water quality standards and on the penalrtee's' -'financial capability.'
 ,j   2. Operational 'Plan. .The permittee, shall submit a revised- operation' Kid maintenance plan that addresses
 ;||f;'|:,-; implementation of  the  selected-CSO controls. 'The revised operation .and maintenance  plan  shall
 •;-   '•'''- maximize the removal of pollutants daring and after -each precipitation event "using all available "facilities
        within the collection aad treatment system.  H^       n=    -  ••-  o::|j||s;;.;  •         .        '.''..
     3. Post-Coiistructiori Compliance Monitoring Proggtm.  'The permittee -shall develop, and -submit -a  post-
        construction monitoring program- that- (a) is adte|uate to ascertain the-, effectiveness of die  CSO.controls
 .." \,;s>- and (b) can be used' to verify attainment of water quality standards."' The program.- shall-.include-'a plan
  *;^'"': that details, the monitoring protocols to be followed, -including CSO and ambient monitoring and, where
      .  appropriate, other monitoring protocols, such as-biological assessments, whole effluent toxieify testing,
 -J--W,  • and sediment .sampling.   -             ;    -1&  -.-»v        -   •     "r- -;-:.   4v;.>:.-.,-;;-       .   '  .%-.
                        *   **'                     ; _:,.>[_7"- •"•" •'.--•            '.;    •    -   •-- .•>:<• >;,, '            T -,\-,
  E. „ Schedule and Interim Deliverables fc  ""'"'    ••  '*'""'         K   '              ..   ''" '.:         .    ;::*s-
    ' The following reports  shall be developed in accordance with the requirements specified in 'Sections  III. A
     'through IILD and sabmitted to the'permitting authority' by the dates specified below:^        _          ;;
      1. PublK^aj^gajloj..^!^.  as required in  Section ID.A, shall- be submitted on or before [Insert due
    r   dtate]. ••--•'*'  -      > .:;i      ...   ;::    ,.x   ... -  %                     >^         ,_.    •'       •-..
  '"   2, CSS..ChgjrgcKmaiiop Moniioriag and Modeling plan^ as required in'Sectioa III.B, shall 'be submitted on.
        " or before pHsert.dee .date].  ..     ••'  -.  -,-                      ,       •        *«
                                                                                           August 1995

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Chapter 3                                                                     I Permitting
                       Exhibit 3-6.  Example Permit Language for
          Requiring the Development of a Long-Term Control Han (continued)
    3. CSS.Characlgrimion. Mopi|gmg:..and..Modeling Results. iocludiri|>identificauan of'sensitive areas, -as
       required in Section III'.B, shall be submitted on or .before [insert'duedate}..     ••  •   '  •   '
    4. •'C^CopUBJ^tenpgvgs.Idfliaific^gn.-'as required ia. Section lli.C.l, staff be s!ibmiwed.:.
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Chapters	Phase I Permittimg

not necessarily be required.  Acceptable documentation may also include summaries of public
comments received.

3.5.1.2   Characterization, Monitoring, and Modeling of the CSS and Receiving Waters
       Characterization, monitoring, and modeling activities provide the basis for the permittee
to choose and design effective CSO controls.  According to the CSO Control Policy,  the major
elements include;

       •  Examination of rainfall records
       •  Characterization of the CSS
       *  Monitoring of CSOs and receiving water quality
       *  Modeling of the CSS and the receiving water.

       As discussed in Section 3.7, initial  characterization and monitoring  activities are
conducted under one of the NMC (monitor to effectively characterize CSO impacts and efficacy
of CSO controls).   If the permittee has already characterized its CSS, CSOs, and impacts OD
receiving  waters,  permit  requirements for further characterization  may  not  be  necessary'
(although  long-term  compliance  monitoring  will  still  be  necessary,  as  discussed  in
Section 3.5,1.9). If the permittee has not sufficiently characterized the system, the permit writer
should determine whether further efforts are needed and establish permit conditions that specify
the characterization activities necessary to adequately complete this component  of the LTCP.
EPA's Combined Sewer Overflows—Guidance for Monitoring and Modeling (EPA, 1995d) and
Combined Sewer Overflows—Guidance for Long-Term  Control Plan (EPA, 1995a)  present
technical guidance related  to proper CSS characterization.

       EPA  recommends  that  the permit  writer  require  the permittee  to  develop  a
characterization and monitoring plan that includes the monitoring  protocols, procedures, and
associated time  periods for  collection of data that will be used to characterize the CSS and
receiving waters. (Section 3.5.2 discusses submittal of the plan and other interim deliverables.)
This  characterization and monitoring plan should be  reviewed by  the  NPDES permitting

                                         3_18                             August 1995

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                                                                       Phase I Pemuttimg
authority, Slate WQS authority, and EPA Region,  As part of this review, these parties should
agree on the data, information, and analyses needed to support the development of the LTCP
aad the review and revisions to WQS and implementation procedures to reflect site-specific wet
weather conditions, if appropriate.  In addition, the permittee's proposed characterization and
monitoring plan should be coordinated with other monitoring efforts within the same watershed.
Review and concurrence by these participants should ensure that the permittee collects adequate
but not unnecessary characterization and monitoring data.

3.5,1.3   Consideration of Sensitive Areas
       Sensitive areas should be identified as part of the CSS characterization as soon as  the
locations of all CSO outfalls are known.  The CSO Control Policy indicates that sensitive areas
should be given priority during LTCP development (see  discussion in next section). Examples
of sensitive areas are provided in the CSO Control Policy and listed in Exhibit  3-7.

                    3-7.                           in the CSO Control
                       'Resource Waters  •  ift'  ;'
   »  National                   ""        '•       ,.  •  ...
   *  Waters with.threatened, or endangered
   *'  fteers with primly contact-recreation,(e.g., swimming)
    •   «:                     •  ,.,j. 'S;>|S-r:.j,:   " ;?-
   *  -Public drinking water       :ii%  """'*   • a|F "•
   »                   *  '  -    ;?,,s    ': it  -,• ..  •"'
       The initial identification  of sensitive  areas  should  be made  by the  permittee  in
consultation with the  NPDES permitting authority and may require coordination with local,
State, and Federal agencies involved in the protection of such areas.  For example, the permittee
and permit writer should:
           Coordinate with the U.S. Fish and Wildlife Service to determine whether CSOs occur
           in waters with threatened or endangered species.
           Coordinate with the local public water  utility to ensure the designation of drinking
           water sources as sensitive areas.
                                           3-19                               August 1995

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Chapt&T 3	Phase I Permitting

       *  Evaluate the designated uses of each CSO receiving water because the State might
          have a designated use that corresponds to a sensitive area as defined by the CSO
          Control Policy.
The NPDES permitting authority will make the final determination of sensitive areas.

       Once sensitive areas have been identified, the permit should require the permittee to give
the highest priority to controlling overflows to these areas. Permit conditions should require the
LTCP to 1) prohibit new or significantly increased overflows to sensitive areas, 2) eliminate or
relocate  overflows  that  discharge  to sensitive  areas  wherever physically  possible  and
economically  achievable  (except  where  elimination  or  relocation  would  provide  less
environmental protection than additional treatment), or 3) where elimination or relocation is not
physically possible and economically achievable, or would provide less environmental protection
than additional treatment,  provide the level of treatment  for  remaining  overflows deemed
necessary to meet WQS for full protection of existing  and designated uses.

       Section ULC. 1 of Exhibit 3-6 contains example permit language requiring the permittee
to consider sensitive areas during LTCP development.

3.5.1.4    Evaluation of Control  Alternatives
       The primary objective of the  LTCP is  to evaluate CSO control alternatives that will
enable the permittee, in consultation with the NPDES permitting authority, the WQS authority,
and the public, to select CSO controls that will meet  CWA requirements.  To ensure that the
most cost-effective and protective CSO controls are selected, the permit writer should require
the permittee  to consider a reasonable range of CSO  control alternatives.   The CSO Control
Policy encourages the permittee to evaluate CSO control alternatives that provide varying levels
of control such as those that would achieve:
                                          3-20                              August 1995

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Chapter 3                                                            Pha$e I Permitting
       *  Example 1
          -  Zero overflow events per year (i.e., total elimination of CSOs via storage and/or
             sewer separation)
          -  An average of 1 to 3 overflow events per year
          -  An average of 4 to 7 overflow events per year
             An average of 8 to 12 overflow events per year,
       *  Example 2
             Controls that achieve 100-percent capture for treatment
          -  Controls that achieve 90-percent capture for  treatment
             Controls that achieve 85-percent capture for  treatment
          -  Controls that achieve 80-percent capture for  treatment
          -  Controls that achieve 75-percent capture for  treatment.
The permittee should develop an appropriate range of control alternatives based on site-specific
conditions.

       The CSO  control alternatives could include  total  sewer separation or retention of all
combined sewer  flows for subsequent treatment during dry  weather.   The  CSO control
alternatives also could include a combination of controls for an entire system (e.g., partial sewer
separation and retention).  In addition, the permittee should consider, among its CSO control
alternatives, expanding POTW treatment plant secondary  and primary capacity and associated
appurtenances to  enable additional treatment of combined sewage.  Thus,  the Phase 1 permit
should require the permittee to evaluate the maximization of treatment at the POTW treatment
plant  among its  CSO control alternatives.  EPA's guidance  on LTCPs  contains additional
technical guidance on evaluating CSO control alternatives (EPA, 1995a).

       The evaluation of alternatives will ultimately enable the permittee to select CSO controls,
in consultation with the NPDES permitting authority, WQS authority, and the public, that, when
implemented, will comply with water quality-based requirements of the CWA either through the
"presumption approach" or the "demonstration approach,"  It is unlikely that a permittee or a
permit writer will be able to determine the level of control  necessary to meet WQS requirements
prior to the initiation of the LTCP planning process.  Similarly, a permittee will probably not

                                          3-21                             August 1995

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Chapter 3	Phase I PetmMmg


be able to specifically adopt either the presumption or demonstration approach until after the

initial planning process has begun and more is known about its CSS  and CSOs. These two

approaches (contained in the CSO Control Policy) are described in the following  discussion,


Presumption Approach

       The  presumption  approach presumes  that the CSO controls  necessary  to  meet the

performance criteria presented in the CSO Control Policy will be sufficient to meet  the water

quality-based requirements of the CWA,  The permittee may consider the presumption approach

where  the level of control needed to protect WQS is  unknown, but the  permit writer and
permittee agree the approach is reasonable based on the data and analysis conducted  as part of

the characterization.  This approach is based on the permittee meeting  one ot  the  following

criteria presented hi the CSO Control Policy:
       *  No more than an average of four overflow events per year. pr«»x i JcJ th.it the NPDES
          permitting authority may allow up to two additional overflow event* per vear.  Thus,
          the permit  writer may allow four,  five, or six overflow event- per vear.  For the
         ' purpose of this criterion, the CSO Control Policy defines an overt,.-* event as "one
          or more  overflows from a CSS as  the result of a precipitant, event thai does not
          receive the minimum treatment specified below."
       *  The elimination or capture for treatment (as treatment is spcxiheJ tx.-l.-w t of no less
          than 85 percent by volume of the combined sewage colkvieJ in  the CSS during
          precipitation events on a system-wide annual average basis  1 1 > Jeterm me the volume
          of  combined sewage that must  be captured or  eliminated,  the permittee should
          calculate the total volume entering the combined sewer during precipitation events on
          a system- wide annual average basis.

       *  The elimination or reduction of no less  than the mass of pollutants identified as
          causing WQS exceedances through the sewer system characterization, monitoring,
          and modeling effort  for the volume(s) that would  be eliminated  or captured  for
          treatment,  as described under  the  previous  bullet.   Again,  the  permittee, in
          consultation with the permit writer, should determine  the appropriate  volume of
          combined sewage to be treated.  In addition, the permittee, in consultation with the
          permit writer, should identify the specific pollutants and their masses to be eliminated
          or reduced.
                                          3_22                             August 1995

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Chapter 3	Phase 1 PermMng

       For purposes of the first two criteria above, all combined sewer flows in the CSS
remaining after implementation of the NMC  should  be required  to  receive the following
minimum treatment:

       *  Primary clarification (or equivalent) for the removal of floatables and settleable solids
       •  Solids and floatables disposal
       *  Disinfection of effluent, if necessary, to meet WQS  and protect  human health,
          including removal of harmful disinfection chemical  residuals, where necessary  to
          meet WQS.

       For example, if the permittee chooses to capture 85 percent by volume of the combined
sewage collected on a system-wide annual basis during precipitation events, these flows should
receive the treatment listed previously.  The remaining 15 percent by volume should receive
treatment to the greatest extent practicable, and this should be addressed in the operational plan.
For  example,  in considering  what  type  of treatment constitutes  "to the greatest extent
practicable," the permittee may evaluate whether attaching nets as end-of-pipe controls for solid
and floatable materials in  the remaining 15  percent is achievable within technical and  financial
constraints.

       As  stated in the  CSO  Control Policy, the  controls  selected  under the presumption
approach are only "presumed" to meet the water quality-based requirements of the CWA
".. .provided the permitting authority determines that such presumption is reasonable in light of
the data and analysis conducted in the characterization,  monitoring and modeling of the system
and the consideration of sensitive areas...."  Therefore, the selected CSO control program should
be designed to allow  for cost-effective  expansion or  cost-effective retrofitting if additional
controls are subsequently  determined to be necessary to meet WQS.

Demonstration Approach
        As an alternative to the presumption approach, the permittee may choose to demonstrate
that the selected CSO controls, when  implemented, will be adequate to comply with the water

                                          3-23                              August 1995

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Chapter 3                        	Phase I Permitting


quality-based CWA  requirements.   An adequate demonstration should include each  of the
following:
       *  The planned control program is adequate to provide for attainment of WQS unless
          WQS cannot be attained as a  result of natural background conditions or pollution
          sources other than CSOs,

       *  The CSOs remaining after implementation of the planned control program will not
          preclude the attainment of WQS.  If WQS  are not met in part because of natural
          background conditions or pollution sources other than CSOs, a total maximum daily
          load (TMDL), including a wasteload allocation for  point sources, a load allocation
          for nonpoint sources, and  a margin of safety, should be used to apportion pollutant
         " loads to all source discharges.

       *  The planned control program will provide the maximum pollution reduction benefits
          reasonably attainable including the cost/performance considerations below.

       *  The planned control program is designed to allow cost-effective expansion or cost-
          effective  retrofitting  if additional controls are subsequently determined  to be
          necessary to meet WQS.
       it  is  important to note  some  additional considerations  pertaining  to  use of  the
demonstration approach:


       Naiural Background  Conditions:   The  decision as  to  whether natural  background

conditions preclude attainment of WQS is made during the WQS-setting process by the WQS
authority.  "Natural background conditions" of a receiving water body  include both naturally

occurring pollutant concentrations and channel and instreain characteristics (e.g., mean stream
width  and depth,  total  volume,  flow and water velocity, reaeration rates, seasonal changes,

turbidity, suspended solids, temperature, sedimentation, and channel stability, obstructions, or

changes).


       Decisions regarding pollutant sources other than  CSOs,  on the  other hand, are made

during the development of wasteload allocations during the TMDL process.  Other "pollution

sources" to a receiving water body could include additional municipal or industrial point source
                                          3-24                              August 1995

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Chapter 3	Ftoe / Permitting

dischargers, including facilities or operations with storm water discharges, and nonpoint sources,
such as agricultural and roadway runoff or drainage from abandoned mines.

       TMDL:  A TMDL is a technically sound and legally defensible tool used by a State to
calculate and apportion to identified sources the allowable amounts of pollutants that may be
discharged  into the water body without exceeding numeric criteria or another quantifiable
endpoint (e.g., temperature, riparian habitat).  The use of a TMDL to apportion pollutant loads
is illustrated by the following example:

       A river segment  at the lower end of a watershed is not meeting its designated use because
       of excessive concentration of one particular metal.  Studies determined that sources of the
       metal include a  metal finishing plant  (300 kg/yr), a PQTW (200 kg/yr), drainage from
       an abandoned mine (400 kg/yr), CSOs (500 kg/yr), and atmospheric deposition (5 kg/yr),
       The metal finishing plant is meeting its technology-based permit limits and little reduction
       in metal loadings can be anticipated without expensive upgrades. No further reductions
       in loadings can be achieved by the POTW without expensive upgrades.   The mine
       drainage can be treated using BMPs to remove  75 percent of the metal (leaving 100
       kg/yr). Design  changes to the CSS will reduce the metal loadings to 50 kg/yr.

       Modeling analyses would then be conducted, and  a margin of safety would be identified
       to accommodate potential ne\v development or lack of certainty in the modeling analysis.
       If this modeling indicates that the resulting WQSfor the particular metal can be achieved
       through implementation of those allocations (including the margin of safety), the analysis
       constitutes a TMDL.  The TMDL should then be submitted to EPA for review under CWA
       Section 303 (d).

       To help ensure that the demonstration by the permittee will be adequate, the permit writer
should consider defining how the above criteria for "adequate demonstration" will be met. If
the NPDES permitting  authority has particular policies or procedures for evaluating water quality
impacts, then the permit writer should place these requirements in the permit.
                                          3-25                         '    August 1995

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Chapter 3              	Phase I Permittimg

       If natural background conditions or pollution sources other than CSOs are contributing
to exceedances of WQS, then the permit writer should coordinate with the appropriate State
authorities to determine whether a TMDL has  been developed or is in the process of being
developed for the watershed in which the permittee is located. Effluent limitations for the CSO
outfall must be consistent with any WLA for that CSO prepared by the State and approved by
EPA pursuant to 40 CFR 130,7.  (See 40 CFR 122.44(d)(!)(vii)(B).)  The permittee should
demonstrate compliance with  such  WLA.   In the absence of a TMDL  for a pollutant or
pollutants, the permit writer should coordinate with appropriate State water quality personnel to
determine how a permittee will demonstrate compliance with WQS in light of the other source
of pollutants.

       Under the demonstration approach, the permit writer also should specify clearly what will
constitute a reasonable effort by the permittee  to demonstrate the maximum pollution reduction
benefits reasonably attainable.  Maximum pollution reduction that is  "reasonably attainable" is
the reduction that can be realized through the implementation of CSO controls determined to be
feasible for the individual permittee, recognizing factors such as the nature of the individual
CSS,  the characteristics of the receiving water body, and other factors specific to the CSO and
receiving water body.

       To provide an adequate demonstration,  the permittee should rely upon data collected both
during monitoring done as  part of NMC  implementation and the characterization, monitoring,
and modeling completed during the initial stages of LTCP development. Using these data, the
permittee should establish that its selected CSO controls will satisfy each of the demonstration
criteria.

3.5.1,5   Cost/Performance Considerations
       The  permit writer should require the permittee  to develop and submit with the LTCP
appropriate  cost/performance curves for each of the CSO control alternatives being evaluated.
The permittee develops the curves  to demonstrate the relationship between the anticipated
effectiveness of CSO control alternatives being considered and the cost of each.  Consistent with

                                          3-26                             August 1995

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Chapter 3	Phase I Permitting

the CSO Control Policy, the permittee should be required to include an analysis discussing the
point at which the increment of pollution reduction achieved in the receiving water diminishes
compared to increased costs (i.e., a "knee of the curve" analysis).  The permit writer may also
want to require the permittee to evaluate the environmental benefits associated with the cost/
performance curves (e.g., the reduction in the number of days per year that the receiving water
exceeds State bacteriological WQS). These analyses will ultimately help guide the selection of
CSO controls by the permittee, NPDES permitting authority, WQS authority,  and the public.
EPA's guidance on LTCPs contains detailed information related to the development and review
of cost/performance curves (EPA, 1995a).

3.5.1.6   Operational Plan
       The Phase  I permit should generally  include  a requirement that, once  the appropriate
CSO controls are  selected, the permittee will revise the O&M plan developed as part of the
NMC to include the selected CSO controls.  The operational plan, as it incorporates the O&M
program implemented as part of the NMC, will reduce the magnitude,  frequency, and duration
of CSOs.  As described hi the CSO Control Policy, the operational plan should be designed to
maximize the removal of pollutants during and after each precipitation event using all available
facilities within the collection and treatment  system.   The  operational  plan should also specify
methods to ensure that any flows in excess  of the volumes prescribed under the presumption
approach (e.g., flows in excess of 85  percent by volume of the combined sewage collected in
the CSS during precipitation events on a system-wide annual average basis) receive treatment
to the greatest extent practicable.  EPA's guidance on LTCPs presents additional information
on technical considerations in revising an O&M program (EPA, 1995a).

3.5.1.7   Maximization of Treatment at the POTW Treatment Plant
       As discussed in Section 3.5.1.4 (Evaluation of Control Alternatives), the permittee should
evaluate the maximization of treatment at the  POTW treatment plant as part of the LTCP.
As a component of the LTCP, maximization of treatment at the treatment plant is envisioned to
include the use of existing primary excess wet weather flow capacity rather than the construction
of additional treatment capacity. However, as part of evaluating whether the use of existing

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Chapter 3	Phase I Permitting

primary capacity  is an appropriate long-term alternative, the permittee  should evaluate the
feasibility of expanding either primary treatment capacity  or both primary and  secondary
treatment capacities.

       This component of the LTCP is distinguished from maamkation of flow to' the P0TW
for treatment,  one of the NMC,  The minimum control focuses on maximizing flow through
the treatment plant so that the combined sewage flow can receive secondary treatment.  Thus,
this minimum control takes  advantage of existing secondary treatment capacity,

       As stated in the CSO Control Policy, maximization of treatment has two  benefits:
       *  Treatment of increased flows during wet weather may enable the permittee to
          minimize overflows to sensitive areas
       *  Combined sewer flows would receive at least primary treatment.
In addition, use of existing primary treatment capacity at the treatment plant may prove to be
a cost-effective alternative based on the cost/performance analyses of CSO control alternatives.

       If a permittee determines during its LTCP development that utilization of excess primary
treatment capacity is a feasible long-term CSO control, the permit writer will need to consider
authorization of a CSO-related bypass for the permittee.  Section 4.9.1  contains a detailed
discussion  of CSO-related bypass, which is likely to be addressed in the special conditions
section of the Phase II permit.

3.5.1.8    Implementation Schedule
       The permit should require the  permittee to develop a schedule that will ensure timely
implementation of the  selected CSO controls.  The proposed CSO  implementation schedule
should include  construction schedules,  financing plans, and milestones for any other permitting
requirements (e.g., environmental reviews, siting of facilities, site acquisition, and Army Corps
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Chapter 3	 	   	      FJtoe 1 Permitting


of  Engineers  permits).   These schedules may  be phased depending  on  the  following
environmental and financial factors:


       *  Elimination of CSOs to sensitive areas as the highest priority

       »  Use impairment of receiving water

       *  Permittee's financial capability, including consideration of such factors as:

          -   Median household income
          -   Total annual wastewater and CSO control  costs per household as a percent of
              median household income
          -   Overall net  debt as a percent of full market property value
          -   Property tax revenues as a percent of full market property value
          -   Property tax collection rate
              Unemployment
          -   Bond rating

       *  Grant and loan availability

       •  Previous and current residential, commercial, and industrial sewer user fees and rate
          structures

       *  Other viable funding mechanisms and sources of financing,


       EPA's guidance documents on LTCPs (EPA, 1995a) and financial capability assessment

(EPA, 1995e) contain information on scheduling and financial capability.


3.5.1.9   Post-Construction Compliance Monitoring Program

       The post-construction compliance  monitoring plan should be submitted by the permittee

as part of the  LTCP and reviewed by the permit writer (see Section 4.5.2).  The permit writer

should require that this plan detail the monitoring protocols and associated schedules (including
the duration of the different monitoring activities). The monitoring protocols should include the
necessary effluent and ambient monitoring and, where appropriate, biological assessments, whole

effluent toxicity testing, and sediment sampling.
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Chapter 3
       The monitoring plan should  include ambient monitoring at locations appropriate to
determine the Ml range of CSO impacts on the water body.  The  types of pollutants and
parameters to be analyzed, which will depend on the WQS in the receiving water body, might
include chemical  (e.g., biochemical  oxygen demand, total suspended solids, metals,  oil and
grease, herbicides, and pesticides), physical (e.g., temperature, turbidity, sedimentation), and
biological (e.g., fish, benthic invertebrates, and zooplankton) parameters.   The monitoring
should be coordinated with any ongoing or planned State monitoring programs and programs of
other permittees within the same watershed,

       The permit writer should encourage the  permittee to develop appropriate measures of
success as part of its monitoring plan. The permittee's measures of success should be based on
site-specific circumstances.  Section  2.8 discusses potential measures of success for the CSO
program,

       Because construction of the selected CSO  controls may extend over several permit terms,
it  might be  appropriate  to  defer  all  or some  requirements for development of the post-
construction monitoring plan to later permits when construction of the CSO controls is complete,
The permit writer may  also  consider requiring the permittee to conduct certain types of
monitoring (e.g., for specified parameters) for the duration of the permit and other monitoring
for a time period shorter than the permit term.  EPA's guidance for monitoring and modeling
presents information on the development of a post-construction compliance monitoring program
(EPA, 1995d).

3.5.2  Schedule for Development of the Long-Term Control Plan
       The permit writer should establish a deadline for completing and submitting the LTCP.
According to the CSO Control Policy, this deadline should be within two years of the effective
date of the Phase I permit or other implementation mechanism (such as an enforcement order).
As stated in the CSO Control Policy, the permit writer may extend the two-year deadline on a
case-by-case basis to account for site-specific factors that might complicate the planning process
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Chapter 3	^	Phase I Permitting

for the permittee.  A schedule for completion of the LTCP should be included in an appropriate
enforceable mechanism.

       The permit writer should also consider establishing a periodic reporting schedule that
requires the permittee to report on progress related to LTCP development.  These progress
reports should describe progress made to date on each  of the primary LTCP  components,
identify problems that might affect completion of the LTCP, and describe remedial measures to
be taken when necessary. Depending on the specific circumstances and complexity of the CSS,
a permit writer may require submission of progress reports on a regular basis (e.g., quarterly,
biannually), customize  the  schedule to track critical path components (e.g., to ensure public
participation occurs early in the process or that CSS characterization is proceeding), or require
the submission of progress reports at the completion of each component of the LTCP.

       hi addition to progress reports, the permit  writer  should consider establishing interim
deadlines and deliverables for various components of the LTCP to ensure that the permittee is
making adequate progress during the term of the permit.  Example permit language requiring
the submission of interim  deliverables is provided in Exhibit  3-5, presented earlier.   The
submission of interim deliverables prior to completion of the LTCP gives the permit writer and
other key participants,  such as WQS authorities, an opportunity to review critical components
of the LTCP early in the planning process and avoid delays hi issuing the Phase II permit due
to the submission of inadequate information or analyses.  Generally, EPA expects the permit
writer to receive the following interim deliverables prior to completion of the LTCP;

       *  Public participation plan
       •  CSS characterization,  monitoring, and modeling plan
       •  CSS characterization,  monitoring, and modeling results, including identification of
          sensitive areas
       *  Identification of CSO control alternatives
       *  Evaluation of CSO control alternatives and cost/performance curves
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Chapter 3	Phase I Permitting

       »   Operational plan
       •   Proposed implementation schedule, including supporting analyses
       *   Post-construction compliance monitoring plan.

       Upon receipt of an interim deliverable, the permit writer should work closely with the
permittee to ensure that any inadequacies or other issues arc addressed prior to submittai of the
final LTCP and issuance of the Phase n  permit.  Section 3.10 provides more detail on the
responsibilities of the permit writer while reviewing interim deliverables.

       The specific deadlines in the permit or other enforceable mechanism will depend on the
circumstances  of the CSS being permitted.   For example, if a permit writer requires the
development of a public participation plan,  the permit  writer should impose deadlines for
completion  of  the plan and, after  review  by  the  NPDES permitting authority, for  its
implementation. In other cases, the information, such as CSS characterization data needed to
identify sensitive areas, might not be available prior to issuance of the Phase I permit. Due to
the importance of evaluating alternatives  to protect sensitive areas, the permit writer should
establish  a deadline for the  submission of information on sensitive areas early in the LTCP
development process.

3.5.3  Considerations for Previous or Ongoing CSO Control Efforts and Snail Combined
       Sewer Systems
       Generally, the permit writer should consider two special factors when establishing the
requirements to develop the  LTCP:  the permittee's previous efforts to control CSOs and the
limited resources of small communities,

3.5.3.1    Recognition 0f Previous or Ongoing Efforts  at Controlling CSOs
       The permit writer will probably determine that municipalities are at different stages of
CSO characterization and CSO control implementation. Some municipalities might have already
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Chapter 3	Phase I Permitting

begun planning, monitoring, and implementing CSO controls in response to EPA's 1989 CSO
Control Strategy and other initiatives.

       The CSO Control Policy recommends that the permit writer consider,  on a case-by-case
basis, the following efforts that a permittee might have undertaken prior to Phase I permitting:
1) substantial completion of construction of CSO controls that appear to provide for attainment
of WQS, 2) CSO control programs substantially developed or implemented pursuant to existing
permits or enforcement orders, and 3) previous construction of CSO control facilities designed
to provide  for attainment of WQS but where WQS have not been attained  due to remaining
CSOs.

       If the permit writer has determined  that the  permittee has "substantial!) completed"
construction of projects designed to provide for attainment of WQS, the permit Conditions for
LTCP development may be modified to reflect these efforts.  The permit unti" ma\ choose not
to require  the  initial planning and construction provisions of the LKT    The permittee,
however, should be required to complete the relevant components of the 1 Iff* ifut might not
have been addressed by the permittee's previous efforts or that represent on.* nnj ^.nnmitments,
including development of an O&M program and post-construction comp!u:v.i- its »mtormg plan.
If subsequent monitoring shows that the WQS are not being attained arwi CS< K continue to
contribute  to the  impairment of designated uses or exceedances of  u.tter quality  criteria,
notwithstanding efforts to coordinate with  WQS authorities,  then an enforceable order should
require a re vised/amended LTCP, and the permit should be modified as appropriate.

       If the permittee has substantially developed or is implementing  a CSO control program
pursuant to an existing permit or enforcement order but has not completed construction of the
selected CSO controls, and the control program is expected to provide for attainment of WQS
and is consistent with the objectives of the CSO Control Policy, the permit requirements should
be modified to require evaluation of sensitive  areas and financial capabilities, as well as
development of a post-construction monitoring plan.
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Chapter 3	Phase I Permitting

       If the permittee has previously constructed CSO facilities in an effort to attain WQS but
has failed  to  meet the applicable standards because remaining CSOs are not sufficiently
controlled,  the permit writer may consider these previous efforts when identifying further CSO
control planning activities. The previous construction of CSO control facilities, although not yet
attaining  WQS, may mitigate the need to complete each step in the LTCP. In some cases, a
permit writer may need to require the development of a complete, although  abbreviated, LTCP
(e.g., further CSS characterization might be needed or other alternative CSO controls identified
and costs and funding mechanisms developed).

3,5.3.2   Small System Considerations
       The CSO Control Policy acknowledges that portions of the  LTCP may prove to be
difficult to  implement for small municipalities and recommends that for CSSs in jurisdictions
with populations under 75, (XX), the permit requirement to develop the LTCP should reflect the
capabilities of such "small" jurisdictions. The permit writer should ensure that the permittee has
gathered enough information to implement effective CSO controls. The permit requirements for
developing a plan  should include consideration of sensitive areas, public participation in the
selection of the CSO controls, and a post-construction compliance rnonitormg program sufficient
to determine whether WQS are attained.  Thus,  for jurisdictions  with populations less  than
75,OCX), the permit writer may use discretion in deciding not to include specific requirements for
the following components of the LTCP:  system characterization, monitoring and modeling;
evaluation and selection of alternatives (including cost/performance analyses); operational plans-
maximization of treatment at the POTW treatment plant; and implementation schedule. Overall,
the permit writer should be aware that a delicate balance needs to be achieved between resources
spent on monitoring and modeling and resources spent on implementation of controls.

3.6    EFFLUENT LIMITATIONS
       The CWA requires that technology-based effluent limitations be established for all point
source discharges.  In addition, a point source may also be subject to more stringent limitations,
including those necessary to meet WQS.  During Phase I permitting, the permit writer should
establish technology-based requirements and any other limitations necessary  to meet WQS in the

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Chapter 3	^	Phase / Permitting

form of narrative requirements since  he or she will probably not have sufficient  data or
information to establish numeric effluent limitations. During subsequent CSO permitting phases,
as data and  information related to the CSOs and CSO controls implemented by permittees
improve, it may be appropriate to develop numeric effluent limitations.

3.6.1  Technology-Based Requirements
      Section 301 of the CWA requires effluent reductions based on various degrees of control
technology for all discharges of pollutants.  For existing nonmunicipal dischargers,  these
technology-based  effluent limitations  must reflect BAT/BCT for  toxic, conventional, and
nonconventional pollutants.

      NPDES regulations at 40 CFR 122.44(a) require the establishment of technology-based
effluent limitations for pollutants of concern discharged by point sources that will be regulated
under an NPDES  permit. Although CSOs are subject to technology-based requirements, they
are not subject to  secondary treatment standards applicable to POTWs.  According to  40 CFR
125.3(c), in the absence of national effluent guidelines and standards for point source discharges,
technology-based  effluent limitations are to be established on a case-by-case basis using the
permit writer's BPJ.

       The CSO  Control Policy  recommends the use of the NMC,  in the form of best
management practices (BMPs), as the technology-based requirements for CSOs.  The use of
BMPs  in  lieu of numeric  technology-based effluent limitations is allowed  under 40 CFR
122.44(k)(2)  where it is infeasible to calculate  a  numeric limit.  BMPs are considered
particularly applicable for CSOs because the types, concentrations, and quantities of pollutants
expected from a precipitation event are generally unpredictable.

       As stated in the CSO Control Policy, Phase I permits should at least require the permittee
to "immediately implement BAT/BCT, which includes the nine minimum controls, as determined
on a BPJ basis by the permitting authority."  Thus, where the permit writer determines on a BPJ
basis that the implementation of the NMC in Phase I and Phase JJ permits meets the technology-

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Chapter 3	Phase I Permitting

based requirements, he or she should not need to develop numeric technology-based effluent
limitations.  Exhibit 3-3, presented previously, provides example permit language requiring
implementation of the NMC.

       If the permit writer determines that numeric technology-based effluent limitations are
warranted for CSQs, EPA's Training Manual for NPDES Permit Writers (EPA,  1993)  should
be consulted for guidance on developing limits on a case-by-case basis using BPJ, Although mis
EPA manual is intended to address continuous discharges, it may provide useful information for
wet weather flows.

3.6.2  Water Quality-Based Requirements
       Section 301(b)(l)(C) of the CWA and  NPDES regulations at 40 CFR 122 44  <»t permitting to
determine whether numeric water quality-based effluent limitations art- rxxoxar}    This is due
to many factors including the lack of point source and ambient data tor u-mcnti >nal. loxic, and
nonconventional pollutants of concern. Thus,  it is likely to be very diiiuuls .»r inappropriate for
the permit writer, at this point, to "back-calculate" effluent limits based en WQS.

       As described in the CSO Control Policy, Phase I permits should at least require mat the
permittee immediately comply with applicable WQS  expressed in  the form of  a narrative
limitation. Such a requirement to comply with narrative WQS is justified for CSOs if, prior to
the development of the LTCP, sufficient data  are not available to evaluate the need for numeric
water quality-based effluent limits.

       Exhibit 3-8 provides example permit language requiring compliance with narrative WQS.
The specific narrative standards a permit  writer should include as permit conditions  will depend

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Chapter 3	Phase I Permitting

on, and should be consistent with, State WQS.  All State WQS have narrative criteria that
address aesthetic  qualities (e.g., all waters shall  be free  from discharges that settle to form
objectionable deposits).  Although State narrative standards can be incorporated into the permit
by reference, EPA recommends that the permit writer include the specific narrative  language in
the permit to ensure that the permittee understands exactly what standards it must meet.
                        Exhibit 3-8,  Example Permit Language for
             Requiring Compliance with Narrative Water Quality Standards
 L  'Effluent Limits '  '"  ?•'$•    '•'••               ,       -.-..       .       .          .'
                                     ';'      .;.-.-"        ,                        .
 B. Water 'quality-based requirements for CSOs.      •              '•           "'•.
 ..:::K The permittee, sfeaD not discharge any ...pollutant' 'at a level that: causes or contributes to an: j
  || excursion above numeric or narrative 'criteria developed- and adopted as /part • of {Insert • State namej water
    quality  standards,     •           "      :' ,v  ;'"'  '  ":  :i: •-•   .    ' ^ .       ~- .       • '•'-
    •Site-Specific Language;    •                     .  "\     •'    • '       :    •-.•'•.''.•
         .-.':•'.     .                             f             ' •        '         •:  ••
    /. The'' permittee- shall not discharge -any 'floating debris,, oil, 'grease, scum, foam, or Mher -.objectionable
     '. materials- tfut may. result .in amounts -sufficient to 'be unsightly or otherwise objectionable or to •
    .  •• constitute a"nui$ance under-State .faw.- -:             ••.".-  •         ;      .-.'...-..•.••
    2.; Jhe-.-permittee. shall not discharge .fefffea^le -solids* sediments, sludge deposits, or suspended
      ' particles that may coat or cover su&merged surfaces,  '                  .  .     .....-.•
    3. The permittee shall not discharge any pollutmts iftof msy impart, undesirable adors* tastes,' or  '. .  •
       colors to the receiving water body'- or to the -aquatic tife fiwftd'' therein, wary endang& public -health^
       or may- result in the domitiance ofaut^ance species.- •
3,7    MONITORING
       Phase I permit monitoring requirements should address both NMG implementation and
LTCP  development  activities.   Under  the NMC,  the CSO  Control Policy  recommends
monitoring to characterize CSO impacts and to determine the efficacy of CSO controls.   The
objectives of such monitoring include the Following:

        »  To map the drainage area for the CSS
        *  To identify  all CSO outfall locations and develop a record  of overflow occurrences
           (i.e., total number, frequency, and  duration)
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Chapter 3	^	Phase 1 Permitting

       *   To compile existing information about the receiving water (e.g., existing uses and
          water quality criteria) and whether WQS are currently being attained in the water
          body
       *   To compile  existing information on water quality impacts associated with CSOs
          (e.g., beach closing).
       The information collected as part of this control should be used to establish baseline
conditions both prior to and subsequent to implementation of the NMC.   Exhibit 3-3, given
previously, presents example permit language for the NMC morutoring requirement.

       The second aspect of Phase I monitoring is CSS characterization  as part of LTCP
development. The objectives of such monitoring include the following:
       *  To obtain a thorough understanding of the CSS,  including its response to various
          precipitation events
       *  To evaluate the impacts of CSOs on the receiving water
       *  To assess the effectiveness of various CSO control  alternatives in reducing the
          impacts of CSOs on the receiving water.
       Exhibit 3-5, given previously, contains example permit language for the monitoring
requirements associated with LTCP development.  During LTCP development, the permittee
should prepare a monitoring and modeling plan to be reviewed by the NPDES permitting
authority and other members of the review team (see Section 3.10) before conducting monitoring
and  modeling activities.   This review should ensure that adequate but  not unnecessary
information and data are collected to support LTCP development and the review and revision,
if appropriate, of WQS to reflect site-specific wet weather conditions.

       The permit writer and permittee should not view monitoring conducted as part of NMC
implementation  and LTCP development  as  independent activities,  but  rather as  related
components  in the CSO  control  planning  process.  In many cases, the permittee will be
conducting NMC implementation and LTCP development concurrently. Thus, where monitoring
objectives  overlap, the permit writer should coordinate the monitoring requirements into one

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Chapter 3	Phase I Permitting

comprehensive permit condition.   For example, the permit writer could put all  monitoring
requirements into one section of the permit.

       In some cases, monitoring associated with the NMC and the LTCP might require special
characterization studies (e.g., if existing site-specific information implies that CSOs  are causing
substantial water quality impacts).  These studies might include the following:

       •  Sediment studies
       *  Whole effluent toxicity testing
       *  Biological assessment.

       This type of monitoring can  be required  as a short-term  study special condition.
Typically, such a study is required in response to specific information indicating that the CSO
is impairmg the designated use or water quality.   The permit writer might want  to develop
permit conditions that require  1) a separate monitoring plan to be developed for each special
study, 2) the plan be submitted for review prior to performing the monitoring, and  3) me final
report to be submitted to the NPDES  permitting authority  within a specified time  after study
completion.

       The permit writer should review  the monitoring plans carefully to ensure that the CSO
information collected can be correlated with water quality impacts; otherwise, the studies might
not provide conclusive evidence of the  cause of impact.  Other studies might be needed in
conjunction with these special studies.  For example, sediment studies might not be  meaningful
without a contaminant transport modeling study, and a bioassay might not provide  meaningful
results without toxicity data and CSO data.  The permittee should include appropriate quality
assurance/quality control procedures as  part of these studies to ensure that the results can be
verified. EPA's guidance on monitoring and modeling contains additional information on these
types of studies (EPA, 1995d),
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Chapter 3	^	^	^	Phase 1 Permittwg ,

3.8    REPORTING
       Reporting requkements related to CSO controls that should be included in the Phase I
permit fall into two categories:   1) documentation of NMC implementation and  2) LTCP
development. Exhibit 3-4, presented previously, provides example permit language, and Section
3.4.2 contains a detailed discussion of the recommended reporting requkements associated with
the NMC.  Section 3.5 discusses the  recommended LTCP interim deliverables, as well as the
requirement to submit the completed LTCP, and provides example permit language.

       In addition to the CSO control-related reporting mentioned above, permittees should be
required to periodically report the results from monitoring  requirements established in the
permit, including any special monitoring studies.

3.9  •  SPECIAL CONDITIONS    '
       This section discusses two special conditions. The first, CSO-related bypass, should be
used in certain limited circumstances  to authorize  bypasses under 40 CFR 122.41(m).  The
second special condition, a  reopener clause, should appear in  every permit covering CSOs.

3.9,1  CSO-Related Bypass
       Some POTW treatment plants might have existing  primary  treatment capacity  that
significantly exceeds secondary treatment capacity.  The CSO Control Policy recognizes that
40 CFR 122.41(m) can be interpreted to allow an advance authorization of a CSO-related bypass
in the NPDES permit to take advantage of the opportunity to provide at least primary treatment
of most or all wet weather flows.   The CSO Control Policy envisions that the permittee would
evaluate the feasibility of this as part of the LTCP; for this reason, this special condition is most
likely  to occur  in the Phase II  permit.  If the permit writer believes that a CSO-related bypass
might be an effective CSO  control available for use in the Phase I permit,  however, he or she
should require  the permittee to  submit the  necessary information as part  of the permit
application.  Section 4.9.1  contains a detailed discussion of CSO-related bypass.
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Chapter 3	Phase I Pemuttmg

3,9.2  Permit Reopener Clause
       As with any NPDES permit, the permit writer should include an appropriate reopener
clause.  Exhibit 3-9 provides an example reopener clause generally appropriate for a Phase I
permit.  This reopener language allows the permit to be modified or revoked and reissued to
incorporate requirements to implement selected CSO controls in advance of the normal permit
reissuanee. This will assist the permit writer in accelerating the implementation of selected CSO
controls.   The  permit  writer should  evaluate this language  carefully to  ensure that it is
appropriate for the permittee. The permit writer might decide that the generic reopener clause
already included in NPDES permits is sufficiently broad to address CSOs,

         Exhibit 3-9.  Example Permit  Language for a Phase I Eeopener Clause
 This pennit may be modified ortevotoed.and reissued, as provided -pucsaant to-40 CFR.-122.162.'and'124,5,
 .for-the following reasons:    "  .•/".'.  "•    "
    * To include new:. or revised conditions 'developed 'to comply with. any State-orFederal-.:law0r
  s   regulation- that addresses CSCte. taat is, adopted orpronmlgated sifoseqnent to tlte•ei$^ve.dale.of••
  < •;  this permit •        •   .  .   ..'  '   '  "•   :; '. '   • • .':'.:'-'V  •     '   _  '-?.-  '..;_•  •: '• v.;:
  ..... * To- iaclude new or revised- conditions if new- information, not available -a toe-time of peitutjssuaiice.< .•
      indicates thai CSO cdmrols ''imposed -under -flje .-permit' .have failed to .ensure the attainment of -State' •  '
     ;. water: cjuafity standards.   '•    •  '         -     '   v   '•'.....-.    . '   •    •  " .""    '':
    * To. include .new or revised -conditions based on- new information -generated'- farta ihe long-term -coattol
                                                           ""
  to additi'0ft, this pennit may -be modified :or'.ievoked and . reissued .for any- reason .specified ''in 40':CFR .
  122.62.   -      ;S  :1  ,* ^      '  ' '  -    '       L-  ' -  .'     ' '• .....  •'
3.10   ADDITIONAL ACTIVITIES DURING PHASE I PERMITTING
       The permit writer should be responsible for ensuring the receipt and coordinating the
review of NMC documentation and all interim CSO-related documents submitted as part of the
LTCP development.  This will enable the permit writer to begin evaluating the permittee's
progress in implementing the NMC and developing an LTCP.  The early review during Phase
I will assist the permit writer in identifying and resolving issues prior to the development of the
Phase II permit.  If the review of progress made by the permittee during the Phase I permit term
is not performed until just  prior to the development of the Phase II pennit, significant delays

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Chapter 3	^	^	      pjua* I Permitting

might occur, particularly if a permit writer detects extensive deficiencies in the progress made
by the permittee.

       To ensure that the NMC documentation and all LTCP deliverables are reviewed properly
and to facilitate the expeditious review of these submissions, the permit writer should coordinate
among appropriate representatives of the NPDES permitting authority,  and should establish a
review team made up of NPDES permitting and enforcement personnel. State WQS personnel,
and State  watershed personnel (see  Section 4.5.1).  The permit writer should identify team
members and  coordinate with them to review the NMC documentation and LTCP interim
deliverables.  The review team may  also be useful in assisting the permit writer in developing
permit conditions.
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                                    CHAPTER 4
                              PHASE D PERMTTTING

       This chapter provides the permit writer with guidance related to developing and issuing
the Phase II permit.  It also discusses the review and evaluation of documentation that should
generally be required by the Phase I permit.

4.1    PHASE n PERMIT
       The primary objective of the Phase II permit  should be to require the  permittee to
implement the selected combined sewer overflow (CSO) controls in the long-term control plan
(LTCP) that  will  meet Clean Water Act (CWA)  requirements.   After the permittee  has
completed the development of the LTCP and has discussed and coordinated the selection of the
necessary  CSO controls with the permit writer,  the  State water quality  standards (WQS)
authority, and the public, the permit writer can embody the selected CSO controls into the Phase
n permit.

       To be consistent with the CSO Control Policy, the Phase n permit should generally
contain provisions that:

       *   Require the permittee to continue implementing the nine minimum controls (NMC)
       *   Direct the permittee to implement and  properly operate and maintain the  selected
          CSO controls from the LTCP
       *   Require the  permittee to  implement a  post-construction water quality monitoring
          program
       *   Require the  permittee to periodically reassess overflows to sensitive areas where
          elimination or relocation was not feasible
       *   Authorize the National Pollutant Discharge Elimination (NPDES) permitting authority
          to reopen and modify or revoke and reissue the permit when the CSO controls do not
          result in attainment of WQS.
                                         4-1                             August 1995

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Chapter 4	Phase II Permtitmg

      The permit writer should coordinate the development of the Phase E pennit with the
permittee and the State WQS authority to ensure that statutory and regulatory requirements are
met.  The permit writer should also ensure that the general public is involved in the decision-
making process leading to fmalization of the Phase E pennit conditions through the public notice
provisions of the NPDES permit regulations or the equivalent provision in approved NPDES
State permit issuance programs.

      In drafting the Phase n permit, the permit writer should work closely with the permittee
and the State WQS authority in reviewing the CSO control alternatives presented in the LTCP.
The permit writer should ensure that the permittee has shown, using either the presumption or
demonstration approach,  that the selected CSO controls will provide for the attainment of WQS
in the receiving water body.

      For the technology-based requirements in the Phase n permit, the permit writer should
require continued  implementation of the NMC  as appropriate.  The permittee's documentation
may be used to show that the NMC continue to satisfy best available treatment  economically
achievable (BAT)/best conventional pollutant control technology (BCT) requirements on the basis
of the permit  writer's best professional judgment (BPJ).  The permit writer may choose to
modify any or all of the NMC from the Phase I permit to be more site-specific, based on the
documentation submitted by the permittee.  For the water quality-based requirements in the
Phase n permit, the permit writer should require implementation of the CSO controls in the
LTCP.  The permit writer must document in the fact sheet or statement of basis how the Phase
n permit meets the technology-based and water quality-based requirements of the CWA.

4.2   INFORMATION NEEDS
       To develop a Phase II permit, the permit writer should rely on information and data that
the permittee has submitted in response to Phase I permit requirements.  This includes 1) the
documentation showing the permittee's implementation of the NMC, 2) the LTCP, including any
interim  deliverables  submitted during  the LTCP development, and 3) any other information
required by the Phase I permit.  In most cases, the permit writer will need this information, at

                                         4-2                             August 1995

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Cftqpftr 4
                                                                   Phase If PermMng
a minimum,, to develop an effective Phase II permit.  If this information is not adequate, the
permit writer should request additional information from the permittee,  Section 3,2 describes
available mechanisms for obtaining additional information and data.

4.3    IDENTIFICATION OF CSO OUTFALLS IN THE PERMIT
       The locations of ail CSO outfalls should have been documented prior to issuance of the
Phase II permit.  Therefore, the permit writer should specifically identify CSO outfalls in the
Phase II permit.  Exhibit 4-1  provides example permit language for authorization to discharge
from CSO outfalls. The permit writer should evaluate this language carefully to ensure that it
is appropriate for the permittee.
          Exhibit 4-1.  Example Penult Language for Identifying CSO Outfalls
                                  in a Phase H Permit
 HeperaiiRee:is.'»ttai2ed to discharge 'jfea.the,;ou.tM:lsristed:-l>elow'0i accordaik«- «.stf tjw requirements
                                                         aad other r*"-:.:«fr
•Overflow J&famber •
      . number]
Overflow 'Outfall. •Location'
.|ins«i;lafiftHl'ertoiigita«te
.(street adSress spttoaai)]
                                                                   '- "*. ..... Uj>'n
                                                            Iin>eri
                                                                          water body]
4.4          MINIMUM CONTROLS    •
       The permit writer should determine whether the permittee's actson^ io implement the
NMC under the Phase I permit are adequate to meet the technology based requirements of the
CWA. This can be accomplished by reviewing the information provided b> the permittee during
the Phase I permit term (i.e., NMC documentation and the LTCP).  Section 4.4.1 discusses
recommended evaluation criteria.  The Phase II permit should, as appropriate, require continued
implementation of the NMC. When preparing the Phase II permit, therefore, the permit writer
should develop permit language requiring the continued implementation of the NMC (including
site-specific language, as appropriate) and its associated documentation. Section 4.4.2 provides
example site-specific permit language.
                                          4.3
                                                                           August 1995

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Chapter 4	^	^	Phase II Permitting

4.4.1  Review of Permittee's Implementation of the Nine Minimum Controls
       As discussed in Section 3.10, the permit writer, in conjunction with other appropriate
personnel, should review the NMC documentation for completeness and compliance with Phase
I permit requirements.   The  documentation serves as  the basis  for  the  development  of
technology-based requirements in the Phase II permit, on a BPJ basis reflecting site-specific
considerations.  If a permit writer determines that certain components are incomplete or not
properly addressed by the permittee,  then the permit writer should follow up with the permittee
in one of two ways.   If the permit writer believes that missing or incomplete components are
relatively  significant  and that  the  permittee has not  acted  in good  faith to submit the
documentation, then the permit writer may coordinate with enforcement personnel to initiate an
enforcement  action for noncompliance  with a Phase I permit condition.   If only minor
components are  unclear or incomplete, the permit writer may simply request the missing or
incomplete data from the permittee in accordance with  the policies and procedures of the NPDES
permitting authority (e.g., informal telephone request or formal request letter).

       After receiving the completed documentation, the permit writer should evaluate whether
the actions already taken or being  taken by the permittee are  adequate to meet the NMC
requirements in  the permit.  This section recommends some general criteria under which the
permit writer can evaluate the adequacy of the permittee's NMC,  Because of the site-specific
nature of the control measures, these criteria are not aU-inclusive but provide a  basis for
evaluation  by the permit writer.   EPA's Combined Sewer Overflows—Guidance  for  Nine
Minimum Controls contains additional detail on the NMC (EPA,  1995b),

       The permit writer should review the NMC documentation using the criteria recommended
in the following paragraphs (also provided in checklist form in Appendix C).  The permit writer
should note that  not all the criteria will apply to each permittee.  Applicable criteria  are based
on the control measures implemented by the permittee.
                                          4.4                             August 1995

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Chapter 4	Phase II Permitting


4.4.1.1   Proper Operation and Regular Maintenance Programs for the CSS and CSO
          Outfalls

       When evaluating the permittee's operation and maintenance (O&M) program, the permit
writer should consider whether the program:
       »  Describes the system, including an inventory of all CSO structures, equipment, and
          treatment facilities.  Provides procedures for keeping this inventory current.

       «  Includes  routine inspection, cleaning and maintenance,  and repair schedules for all
          inventoried CSO outfalls, interceptors, regulators, pumping stations, and equipment.
          Includes  schedules and inspection frequencies that are appropriate for the system.

       *  Includes  inspections for dry weather overflows and illicit connections.

       •  Provides operating  procedures  and specifications for all equipment, structures,
          facilities, CSO outfalls,  and off-line storage structures.  Describes the hydraulic
          capacities of the  coEection and treatment systems, the storage capacities of the
          collection and treatment  systems, and off-line storage capacity.

       •  Has in place operating procedures that reflect the best use of the system's flow and
          routing controls to minimize CSOs.  Includes procedures to identify and correct
          combined sewer system (CSS) and CSO problems.

       *  Requires logs or other documentation of completed activities and documentation of
          sewage blockages.

       •  Addresses the location of overflows where O&M is hindered (e.g., structures are
          under major thoroughfares, railroad yards, or other difficult-to-reach or safety hazard
          areas).

       *  Allocates resources for O&M program implementation, including staffing level and
          funding, equipment, and training.

       *  Will be effective in reducing the number, frequency, and pollutant loadings of CSOs.
       Note that an operational plan is also a component of the LTCP.  The O&M program
developed as part of NMC implementation essentially becomes the operational plan (i.e., the

revised O&M  program that includes  the permittee's  selected CSO controls).   Thus, the
operational plan can be reviewed using the above listed factors.
                                          4.5                             August 1995

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Chapter 4      	Phase II Permitting

4.4.1.2   Maximum Use of the Collection System for Storage
       The permit writer should consider whether the permittee has;

       •   Identified portions of the CSS usable for storage and determined the CSS storage
          capacity, including configuration, size, and pump station capacity
       «   Identified appropriate minor modifications to increase storage (e.g., raising existing
          weirs)
       *   Identified potential off-line storage at existing facilities
       •   Implemented procedures for maximizing CSS storage capacity.

       The permit writer should note that this control measure might increase the possibility of
"upstream" problems, such as basement flooding, and mat the potential tor  a permittee to
increase collection system storage varies. Increased sedimentation in the colk*au>n system, mote
frequent cleaning, odor potential, and other factors should be considered ut»cr  evaluating the
potential for collection system storage.

4.4.1.3   Review and Modification of Pretreatment  Programs
       This control applies primarily to permittees with approved pretrcjinu-nr programs. If the
permittee does not have  an approved pretreatment program, however,  11  should  nevertheless
attempt to determine  whether nondomestic  sources are contributing  u> CSO impacts.   In
evaluating the implementation of this control, the permit writer should con>tJcr  whether the
permittee has:

       *  Determined whether the CSS receives nondomestic wastewater discharges.
       *  Prepared an inventory of nondomestic users who discharge to the CSS.  Evaluated
          the discharge constituents and suspected impacts from such users.
                                          4-6                             August 1995

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Chapter 4                                                          Phase II Permittmg
          Evaluated the potential for regulating either the volume or pollutant loadings from
          nondomestic users to the CSS during wet weather flow conditions.  The evaluation
          should include a discussion of whether the modifications are feasible or of practical
          value for CSO control, For example, the permit writer might evaluate whether the
          permittee  has  considered requiring nondomestic  users with  appropriate storage
          capacity to temporarily hold wastewater during precipitation events or when notified
          by the permittee or has considered prohibiting new users from discharging storm
          water or uncontaminated water, such as non-contact cooling water, to the collection
          system,

          Modified the pretreatment program if appropriate.
4.4.1.4   Maximization of Flow to Publicly Owned Treatment Works Treatment Plant

       The permit writer should consider whether the permittee has:

             f
       *  Compared existing flow conditions to the design capacity of the collection system

       *  Identified  actions that could be taken to increase  flows to the publicly  owned
          treatment works (POTW) treatment plant during wet weather flow conditions without
          significantly affecting  treatment performance

       *  Conducted tests to determine the plant capability to treat higher flows during wet
          weather flow conditions or determined, using available historical data, the maximum
          flow that can be  treated

       *  Developed, implemented, and documented implementation of a flow maximization
          plan during wet weather flow conditions.


4.4.1,5   Prohibition of CSOs  During Dry Weather Flow Conditions

       The permit writer should  consider whether the permittee has:
       *  Developed adequate procedures to document where and when dry weather overflows
          occur, including follow-up inspections after dry weather overflows occur

       *  Developed md Instituted procedures to prevent and eliminate dry weather overflows,
          including routine inspection of regulators and CSO outfalls, as part of the O&M plan.
                                          4.7                             August 1995

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Chapter 4	Phase II Permitting


4.4.1.6   Control of Solid and Floatable Materials in CSOs

       The permit writer should consider whether the permittee has:
       »  Evaluated the following technologies for the control of solid and floatable materials
          in CSOs:  screening materials using baffles, screens, and netting; skimmer boats;
          skimming from water body surface with booms at outfalls  in confined areas;  and
          source control, which may be addressed under the pollution prevention program for
          CSO outfalls (see Section 4.4.L7—Pollution Prevention Program)

       *  Identified and addressed problems that might  be created by the installation of the
          control technology

       *  Implemented the appropriate control technology. considered and provided justification
          that the technology is appropriate for the site conditions, and is conducting associated
          inspections and  regular maintenance.
4,4.1.7   Pollution Prevention Program

       The permit writer should consider whether the permittee has:


       *  Evaluated source control measures both at the government level (e.g., street cleaning;
          banning or substitution of products, such as plastic food containers; controlled use of
          pesticides, fertilizers, and other hazardous substances at public facilities) and among
          the public (e.g., used oil recycling, household hazardous waste collection)

       »  Included a wide-reaching public education program

       *  Evaluated  mechanisms to encourage  water conservation (e.g., public outreach,
          structuring of water/sewer service charges, local ordinance provisions)

       *  Allocated adequate resources to conduct pollution prevention program activities

       »  Implemented and maintained detailed records of pollution prevention activities

       *  Promoted the use of industrial/construction best management practices  (BMPs) for
          storm water.
                                           4-g                              August 1995

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Chapter 4	Huge II Permitting


4.4.1.8   Public Notification

       The permit writer should consider whether the permittee has:


       •  Evaluated options to ensure that the public receives adequate notification of CSO
          occurrences and CSO impacts

       •  Implemented notification procedures regarding the presence of contaminants at critical
          levels in the receiving water bodies due to CSOs

       *  Implemented procedures that notify persons reasonably expected to be affected by the
          CSO

       »  Documented CSO occurrences and associated notifications

       «  Installed identification signs at each CSO outfall.


4.4.1.9   Monitoring to Effectively Characterize CSO Impacts and  Efficacy of CSO
          Controls

       The permittee  is  likely to have conducted monitoring recommended for this minimum
control in conjunction with CSS characterization associated with the LTCP development. Thus,
the permit writer should review the permittee's monitoring efforts as a whole and assemble all
applicable monitoring data prior to the evaluation.  In evaluating the permittee's monitoring data,

the permit writer should consider whether the permittee has:


       •  Characterized the CSS to identify all CSO locations and  receiving water bodies

       *  Collected data on the total number of overflow events and the frequency and duration
          of CSOs for a representative number of CSO events

       «  Collected water quality data  and information on chemicalt physical, and biological
          impacts resulting from CSOs (e.g., beach closings, floatabies, wash-up episodes, fish
          kills, impaired habitat for aquatic life)

       »  Conducted monitoring to determine baseline conditions prior to implementation of the
          NMC

       *  Conducted monitoring to determine baseline conditions subsequent to implementation
          of the NMC, which may be used in LTCP development.
                                          4-9                        •    August 1995

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Chapter 4      	Phase II Permitting

       It is  important to note that  the permittee should be considering  its NMC measures
collectively using a holistic  approach—that is, it may be possible to satisfy two or more of the
NMC through a single control measure.

4.4.2  Permit Conditions
       Once  the  permit writer has evaluated  the permittee's NMC  implementation and
documentation efforts, he or she should, where appropriate, develop Phase n permit language
that requires the continued implementation of the NMC. The permit language should be tailored
to the permittee's specific circumstances and should incorporate site-specific implementation and
recordkeeping requirements. The permit writer might need to coordinate the development of this
permit language with the LTCP implementation language because it is possible that some of the
NMC control measures  will be incorporated into the LTCP as selected CSO controls or that
some NMC control measures might DO longer apply when the selected CSO controls have been
implemented (e.g., if the system is being separated).

       The permit writer should establish technology-based requirements in the Phase n permit
based  on the  permittee's  documentation  of the  NMC and  any revisions  resulting  from
development of the LTCP,  Exhibit 4-2 provides example permit language for each of the NMC.
The permit writer should evaluate  this language carefully to ensure that it is appropriate for the
permittee.  A portion of this language should be applicable to all permittees implementing each
particular minimum control.  Additional site-specific language,  which should be tailored  to the
specific control measures implemented by the permittee,  is given in italics.  Although the site-
specific language might not be appropriate for all permittees, it is provided as an example of the
type of language and detail appropriate  for requiring implementation of the NMC in the  Phase
n permit. The permit writer may  be able to select language directly from the permittee's NMC
documentation or LTCP and incorporate it into  the permit.  Although this  guidance presents
numerous examples  of site-specific  permit conditions,  it may be appropriate in some cases to
write broader conditions.   This would  provide sufficient flexibility to allow the permittee to
identify and  implement other controls that are equally or more protective without the need to
modify the permit.

                                          4-10                              August 1995

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Chapter 4
                                                                        Phase H Pemuttittg
          Exhibit 4-2.  Example Permit Language for Continued Implementation
                                 of the Nine Minimum Controls
 A.
- Effluent Limits  .-    .,,,  -.<-.   """"""  j*  ••'"•   '-•  ',,•>  '    ... ^::\:1-;|!^=           <

 Tectraology-bsfied. requirements For CSOs. "Use permittee-, shall comply wilts die. following technology-
 based requirements:  ••;      ,      •    |||..       :'. . , '    >-  ''                    ' . •    >-      t
-1.  •Conduct proper operations and: regular.. mamMitmeeigrogyffliis:.  'The permittee shall implement .fte
  •" operation and maintenance plan for the 'CSS 'thai will include the elements listed below-.  The  - '
    permittee also shall update the plan' t0. incorporate -any changes to the system and shall. operate and
   ^ mMntain the system according to -the pSaa. The permittee -shall keep records -to document the
   s implementation of the plan,'   J-...         ,   ..,:,•••         '               "    .'    ...:.•

    Site*Spedfi c Language:-   "->='.•"" *...,,.. ^;-:V   ,.,.       ,,  : '           .. '  . ,   '•    '  ;,
         ,                       ..     ::':;^' ;:;': ;;«V   ;!|?:       '.     '•     ...     " •    ..  .*'-''
    Designation .-of. a Maaaeer_fyr Combined SewerrSy$tem^ The permittee 'shall designate a person to
    be responsible for the wastewaler collection., 'system md-'serve m the contact person, ••regarding the
                                                                             •  • •  -         •
            Inspection and M&intenanee of CSS.  The permittee sfyM. inspect. and nutinuetn'oll-CSO.    '*
           --structures, regtdtUQrs:t pumping statfonsf:and-tidegates to:ensure. that' they 'O&--mgop4'.working
            'condition . and 'adjusted to minimize CSOs .mid prevent'- tidal] inflow.  The pemime -shall- ' :     |
            inspect, or cause, to be inspected, mch.CSOmtfall:ai'.ait'Qppr^ruttefre^ency-to,.eMSttre-:nQ- "•
            dry veather overflows :are occurring, Theinspeaions]^f:mdude,buth-'notUmtM'iot
            ottering the regulator, ftruaare if accessible, determining the- extent &f:debris 'met. grit buildup,
            and -removing any debris rte may- -consrrict flow, cause Modsage, -or result in a. dry -weather-  .,
            overflow. -The' permittee shall record in a maintenance 'fog -book 'the results rf ^..inspections.
            For. CSO outfalls that are. inaccessible, the. permtme :«my-per/0rmn visual ''ches3c':'of.ihe
           • overflow pipe -to determine  whether of -not the -CSQ is occumng- during 'dry. veather flaw  • .-
            conditions.  " .          -._,.,'          i- ""..-•-••:'    .-,     •'      '     "  .'
            Provi-sion for Trained- -Staff,- The permittee shall emure:-the. avmtoMtify -af&Qmed.Maff. to  ' ;
            cany om the operation, 'maintenance^ repair, 'and -testing junctions required' 'to' ensure
            compliance with the terms .and conditions of this permit. . -'Eack staff member shall -receive
            appropriate training*  .  • ."•'.__        ,          ..--."          >    ...  .      .  •     .    "-:•:•
            Allocation of Funds- for Q
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Chapter 4
                                                            Phase II Permitting
        Exhibit 4-2.  Example Permit Language for Continued Implementation
                      of the Nine Minimum Controls (continued)
                  jiM^
             :|eMW
                                                                   '^

               ion: and implementation of ffie seleaed
         The permittee shall

       fl^jptt^^
• &:|
                     M^»i^^|y^
                                  ?^

                      v:-r5l^
                          e|i^                                              ii ?|

                        t^x^iii^;5^^
                                                     ............................... ' '"

                                  tal^lasGS^SiJ'-' 3$^;|ifFiii:i^^
                                       mm •yftiee-jo -^n^ftlm^^^^s:^^^^^
                                     ^^iu^^j^t^.t^jMu^^^^sii^ ;%;;S
                                        4-12
                                                                   August 1995

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Chapter 4                                                             Phase II Petmittmg
         Exhibit 4-2,                              for
                        of the Nine           Controls (continued)
                     imp^g|«tM^g§o^^!^Qttfonprogrant;i>-''ltfe fenpftte- sfcalL
                          ftguaad.on.        fte      of CS0s,«n:teeeiwng wates. . Jhc
                         to HkaBneotpottmtioa- pret^iaa-.-impfenaii^ OB aetivkfck. '  "       •'    :
          Site-Speafljt Laaguag®;
                Street
                f^
                'A               ^ro
                                 Ttee-jperaiitiee shall o^tiniki^^in^lflaaeat a

         •fe.; .. A>$ptesit0i«ennliiett3ie'-naSfflFe'att4duiatiffla;tff*|Sffiyistisat-aiiejxiieotiffl^llMiifriW-fe'
         Jy  tisers ol ftefce f

          Tie         dial]
          ' Wftiia J       of the           of'Ms fffnait* ihe'.peratitte®
              ftGetimMgn$-«a aO':£5<@:oa$it$ cnimed.and'^pa^t^^ify Ot
              . the. stgKt-at-er nmrAe-'C^./s^atts md «3wefMi<«fe,s%»$ are--easily.
          s&all regularly moaiteF CSQ outfalls to eifecmfely characterize. GSQ impacts and fc: efficacy of
                                            4-13                                      1995

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Chapter 4	Phase II Permitting

       Exhibit 4-2 does not provide site-specific permit language for the ninth minimum control:
monitoring to effectively  characterize CSO impacts and efficacy of CSO  controls.   This
monitoring should be integrated with the monitoring requirement to be placed in the Phase H
permit associated with implementation of the LTCP.   Section 4.7 contains information on
developing permit language for these monitoring requirements.

4.4.2.1   Documentation for Fact Sheet/Statement of Basis
       As required in 40 CFR 124.7 and 124.8, a fact sheet (or a statement of basis for minor
discharges) must be prepared for every NPDES permit.  The purpose of the fact sheet is to set
forth the principal technical facts and the significant factual, legal, methodological, and policy
questions considered in preparing an NPDES permit.  Although 40 CFR  124.8 establishes the
minimum requirements for a fact sheet, each permit writer should follow the format used by the
NPDES permitting authority.

       The fact sheet  must discuss  the basis of  all  Phase II  permit  conditions  requiring
implementation of the NMC.  The permit writer should use the permittee's NMC documentation
to record in the fact sheet the justification for implementation of the specific minimum controls
chosen by  the permittee.   Further, when NMC are imposed  in a specific permit, the permit
writer should discuss the fact that the NMC are being used to comply with the technology-based
requirements  of the CWA (see Section 3.6.1).  EPA's Training Manual for NPDES Permit
Writers contains more  information on preparing a fact sheet or statement of basis (EPA, 1993).

4.5    LONG-TEEM CONTROL PLAN
       The permit writer will generally be responsible for reviewing interim deliverables (see
Section 3.5.2) and for working closely with the permittee to ensure that any inadequacies,
problems,  or issues are addressed  in a timely fashion prior to submission of the completed
LTCP and the development and issuance of the Phase II permit.

       In preparing for the development and issuance  of a Phase II permit, the permit writer
should review the LTCP submitted by the permittee.  After reviewing the LTCP, the permit

                                         4-14                             August 1995

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Chapter 4	^	Phase II Permitting


writer should require, where appropriate, implementation of the selected CSO controls Identified
in the LTCP. The primary responsibility of the permit writer in developing Phase II permits
is to ensure that the CSO controls proposed by the permittee comply with the requirements of
the CWA, including  attainment of WQS.  The requirement to implement these controls should
be appropriately reflected  as enforceable  NPDES permit conditions or included in another
enforceable  mechanism.   This section provides guidance on how to review the LTCP  and
develop permit conditions to implement the LTCP.


4.5.1  Review of Long-Term Control Plan

       The permit writer should form and coordinate a review team thai will he responsible for
reviewing the LTCP  and ensuring that CWA requirements will be met. An appropriate review
team should include:
       *  WQS personnel to  assist in evaluating proposed CSO control*  ar>J  to  review and
          revise State WQS, as appropriate.  WQS personnel can alv» a^i^t in  evaluating any
          ambient or special monitoring conditions (e.g., toxicity icstim- • ttu* nu\  be required
          during the term of  the Phase II permit to monitor the efti-cma*.-^  <'n  o! the  selected
          CSO controls.  This will be particularly important if exiensiu- time i- required by the
          permittee to comply with Phase II permit requirements.

       *  Field personnel to help review monitoring plans and assist in the dc\ cloprnent of CSO
          monitoring  requirements.

       *  Watershed  personnel  to  ensure that the permittee's  CSO  control  efforts are
          coordinated with other point and nonpoint source control efforts within the watershed.
The review team should also include other types of personnel, as appropriate, depending on the
site-specific situation.
                                          445                              August 1995

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Chapter 4  	Phase II Permlttmg

       As discussed in Section 3.5.2, the permittee is likely to have submitted parts of the LTCP
as interim deliverables during the Phase I permit term. The permit writer and other members
of the review team should review these deliverables,  as well as the completed LTCP detailing
the permittee's selected CSO controls, as soon as they are submitted.

       Upon receipt of the LTCP, the permit writer should first determine whether it complies
with the requirements hi the Phase I permit. After initial review of the LTCP, if a permit writer
             !
determines  that certain components are incomplete or are addressed improperly, the permit
writer should follow up with the permittee.  Section 4.4.1 presents  information on followup
procedures.

       The permit writer, with support from other review team  members, should review the
LTCP to ensure consistency with the CSO Control Policy and to ensure that the selected CSO
controls are reasonable and will result in compliance  with CWA requirements.  Of the various
CSO control alternatives considered by the permittee during LTCP development, the LTCP will
identify one or a combination of CSO controls for  implementation.  The LTCP should discuss
all of the alternatives arid, more  importantly,  why  the  selected  CSO controls  were chosen.
There should also be a discussion related to the selected CSO controls, including maximization
of treatment  at the POTW treatment plant; the operational plan; integration  of the NMC;
monitoring; costs of the selected CSO controls and financing; and the implementation schedule,
possibly  including identification of milestones where re-evaluation and modifications would
occur.   All other  parts  of the LTCP, including the CSS and water quality characterisation
monitoring and modeling used during the development process, the other alternatives and costs,
and  public  participation,  ultimately become "historical"  material that should not be addressed
in the Phase II permit, because they are not part of the selected CSO controls.  This information
is generally critical for appropriate review of the LTCP,  however.

       The remainder of this section presents questions the permit writer should consider while
reviewing the LTCP.  These recommended evaluation criteria are also provided in a  checklist
hi Appendix D.  These review questions are based on the provisions of the CSO Control Policy
                                         4-16                              August 1995

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Chapter 4	Phase II Permitting

and the guidance provided in the Combined Sewer Overflows—Guidance for Long-Term Control
Plan (EPA, 1995a). Although the permit writer may use these questions as the basis for review,
he or she may need to supplement them to reflect the site-specific Phase I permit conditions
established for a particular permittee.  For example,  if a Phase I permit specifically required
monitoring and evaluation of certain pollutants of concern, then the permit writer should ensure
that the permittee has addressed these pollutants in its monitoring plan.

      In reviewing the LTCP, the permit writer should remember that the level of detail in the
LTCP can vary significantly depending on the permittee and its CSS. The overall intent of the
review is to ensure that the LTCP is a coherent, organized document and that the permit writer
can follow a logical step-by-step analysis that justifies selection of the CSO controls.

4.5.1.1    Public Participation
      When evaluating the public participation element of the LTCP, the permit writer and
other review team members should consider the following evaluation questions to ensure that the
proposed plan, once implemented, will result in an effective public participation program:
       »  Does the public participation process seek to actively involve rate payers, industrial
          users of the CSS, persons near the affected waters, and persons who use the affected
          waters?
       •  Does the public participation plan document how the public was notified of public
          participation events?
       •  Does the public participation plan include a record of the public participation events,
          including the number of people attending and a record or summary of comments?
       •  Does the public participation plan contain a summary of comments and the changes
          or decisions made in response to public comments?
4.5.1.2   CSS Characterization, Monitoring, and Modeling
       When the permittee submits a proposed monitoring plan as an interim deliverable during
LTCP development, the permit writer and other team members should review it to ensure that,
                                         4_17                             August 1995
                                         /it

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Chapter 4	Phase II Permitting


once implemented, the proposed plan describes an effective monitoring program that will provide
the necessary data.  The team should consider the following questions:
       *  Is there a general description of the CSS that includes the geographical area and
          population served?

       «  Is there a map of the CSS depicting the location of all CSO outfalls and receiving
          water bodies?

       •  Have sensitive areas and all outfalls located in these areas been identified?

       *  Is there a description of how the CSS responds hydraulically to rainfall events, and
          is it adequate to determine which rainfall events trigger CSOs?

       *  Is there information on the volume, flow rate, and frequency  of CSOs and the
          pollutants discharged?

       »  Is there information on the CSO pollutant loadings and their impact*, on receiving
          waters?

       *  Has all available  information on pollutant loadings from cither r*"ini and nonpoint
          sources in the watershed  and their impacts on receiving watcr^ been identified and
          compiled?

       •  Is there information on  designated uses  of  receiving uatcrv  and  whether the
          designated uses are being met?

       «  Does the CSS and CSO characterization provide informathm t»n the known effects of
          the CSOs on water quality during precipitation events, as ud! a-> provide the level
          of detail needed to model or project both the operation of the s> stem and the impacts
          of various overflow scenarios on the receiving waters?

       *  Is monitoring sufficient to document baseline conditions to allow  the permittee to
          demonstrate the long-term benefits of CSO controls?

       •  Has the monitoring been coordinated with any ongoing or planned  State programs and
          programs of other permittees within the same watershed?

       •  If modeling was conducted, is the model identified and described, and are the results
          provided?
 Appendix B contains additional information on reviewing monitoring plans.
                                          4-18                             August 1995
                                         SI,

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Chapter 4	^	^	Phase II PermMmg


4.5.1.3   CSO Control Alternatives

       The pemit writer and the rest of the review team should consider cfae following questions
when reviewing the CSO control alternatives:
       *  Did the permittee develop a comprehensive list of CSO control alternatives? Did this
          list include alternatives from each of the four general categories—source controls,
          collection system controls, storage, and treatment technologies—described in guidance
          for LTCPs (EPA, 1995a)?

       *  Did the permittee describe each CSO control alternative considered?

       *  Does the plan describe the process by which the CSO control  alternatives were
          developed?

       *  Does the plan compare the environmental benefits of the CSO control alternatives?

       *  Is cost/performance information (including curves) for each of the  CSO control
          alternatives provided?  Do the cost/performance analyses evaluate a range of levels
          of controls that were developed based on the permittee's site-specific conditions (e.g.,
          zero overflow events per year, and averages of 1 to 3,  4 to 7, and 8 to 12 overflow
          events per year)?

       *  Does the LTCP describe  the approach  used to screen the list  of  CSO control
          alternatives, including the recommended screening criteria?  Do the screening criteria
          include performance factors, implementation and operation factors, such as costs, and
          environmental impacts (described in EPA's guidance for LTCPs [EPA, 1995a])?
4.5.1.4   Selected CSO Controls

       When  evaluating the  CSO controls, the permit writer should  consider the following

questions:


       »  Is the presumption or demonstration approach used?

       •  Does the plan identify the reasons for selecting certain CSO controls and not others?
          Were reasons for rejecting specific CSO control alternatives appropriate?

       *  Have the NMC  been integrated into the permittee's description of its selected CSO
          controls?
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Chapter 4	Phase II Permitting


       «   Will the selected CSO controls eliminate all CSOs to sensitive areas?  If not, do the
          data support the permittee's conclusion that elimination is not physically possible or
          economically achievable?

       *   If CSOs to sensitive areas remain:

          - Will these CSOs receive treatment?
          - Will the CSO controls be sufficient to provide for the attainment of WQS?

       *   Have control efforts for other point and nonpoint sources of pollutants within the
          watershed been considered?

       *   Will the CSO controls provide treatment or removal of floatables and settleable solids
          equivalent to that achieved by primary clarification?  Is the mechanism for solids and
          floatables disposal described?

       •   Will the disinfection of effluent be necessary in order to  attain WQS?   If so,  is
          disinfection proposed as part of the CSO controls, and will  removal of harmful
          disinfection chemical residuals be necessary?

       »   Do the  selected  CSO controls provide the maximum  pollution reduction benefits
          reasonably attainable?

       *   Will the selected CSO controls provide for the attainment of WQS? If WQS cannot
          be met because of sources other than CSOs, has the permittee provided information
          on the other sources and natural background conditions?

       *   Has a total maximum daily  load (TMDL) been developed for the watershed?  If so,
          has the permittee considered the TMDL in developing its LTCP?

       *   Are the selected CSO controls designed to allow cost-effective expansion or  cost-
          effective retrofitting if additional controls are determined necessary to provide for the
          attainment of WQS?


4,5.1,5   Implementation Schedule

       In reviewing the  implementation schedule, the permit writer should use the data and

information supporting the prioritization of the CSO projects on the basis of their environmental

impacts,  as well as the analysis of financial status,   EPA's Combined Sewer Overflows-

Guidancefor Long-Term Control Plan (EPA. 1995a) and Combined Sewer Overflows—Guidance

for  Financial  Capability Assessment (EPA, 1995e)  recommend  criteria  to  evaluate the

reasonableness of construction schedules and financing plans  in the LTCP.  After reviewing


                                         4-20                             August 1995

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Chapter 4	Phase II Permitting


these documents, the permit writer should refer to the following questions when reviewing the
implementation schedule:


       *   Do any phased construction schedules consider:

          -  Elimination of CSOs to sensitive areas
          -  Use impairment?

       •   Do any phased construction schedules include an analysis of financial capability, such
          as the following  factors:

          -  Median household income
          -  Total annual  wastewater and CSO control  costs per household as a percent of
             median household income
          -  Overall net debt as a percent of full market property value
          -  Property tax  revenues as a percent of full market property value
          -  Property tax  collection rate
          -  Unemployment
          -  Bond rating?

       •   Did the permittee evaluate the following factors:

          -  Grant and loan availability
          -  Previous and current residential, commercial, and industrial sewer user fees and
             rate structures
          -  Other viable  funding mechanisms and sources of financing?

       *   Does the schedule  include milestones  for all  major  implementation activities,
          including environmental reviews, siting of facilities, site acquisition, and Army Corps
          of Engineers permitting?


       The permit writer should review the financing plan to determine whether it provides the

funds necessary to construct CSO controls and assess whether water quality considerations merit

revisions to the proposed implementation schedule.  If so, the permit writer may consider a

revised schedule.


4.5.1.6   Operational Plan

       In evaluating  the operational plan, the  permit writer should  consider whether me
permittee's O&M program addresses the evaluation criteria proposed in Section 4.4.1 for the


                                          4-21                              August 1995

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Chapter 4	Phase II Permitting


NMC, However, the permit writer should ensure the operational plan includes newly-selected
CSO control structures,


4.5.1.7  . Post-Construction Compliance Monitoring

       The permit writer should review the monitoring plan with members of the review team
who are  knowledgeable  about design and implementation of monitoring programs.  When

evaluating post-construction compliance monitoring, the permit writer should consider the
following questions;


       *   Does the monitoring program include monitoring of CSOs that are representative of
          the impacts to receiving waters?

       *   Does the monitoring program include ambient receiving water body monitoring at
          representative  CSOs,  as well as monitoring prior  to CSO  impacts?   Has the
          monitoring program for the receiving water body been coordinated with any ongoing
          or  planned  State programs  and programs  of other  permittees within the same
          watershed?

       *   Does the monitoring  program  include  any  biological  parameters  (e.g.,  fish,
          zooplankton)?

       *  Does the monitoring program address pollutants included in the water quality criteria
          for the specific designated  use(s)  of the receiving  water,  pollutants key to the
          attainment of the designated use(s), and pollutants affected by the CSO controls?

       •  Does the monitoring program include appropriate measures of success?


Appendix B contains additional information on the review of a monitoring plan.


4.5.2  Implementation of the Long-Term Control Plan

       As described in the CSO  Control Policy,  Phase I! permits  should contain "narrative
requirements  which ensure that the selected CSO  controls  are implemented, operated  and

maintained as described in the long-term CSO control plan."  Because the CSO controls will
have  been selected on a site-specific basis, the implementation conditions should also be site-

specific.  Thus, the permit writer should not simply develop a  generic permit condition that



                                         4-22                              August 1995

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Chapter 4	Phase II Permitting

requires implementation of the LTCP as developed, incorporating the LTCP into the NPDES
permit by  reference.   Rather, the permit should contain specific  conditions  that  require
implementation of the selected CSO controls, the proposed O&M program requirements, and
the proposed post-construction compliance monitoring program.  The  following subsections
briefly discuss each of these portions of the LTCP.

4.5.2.1   Selected CSO Controls
       The  permit  writer should  develop  permit conditions  that specifically  require  the
implementation of the selected CSO controls, once approved. As discussed above, due to the
differences among CSSs, the CSO controls identified in LTCPs will vary from system to system.
In many cases, the CSO controls will require major construction and implementation activities
that can only be completed over several five-year NPDES permit cycles.  The CSO Control
Policy recommends that the LTCP include the information necessary to  develop the fixed-date
schedules for funding and implementing the CSO control program.  The LTCP should prioritize
the individual projects within the overall control program on the basis of environmental impacts,
financial capability, and available funding. Section 3.5.1 provides additional discussions on the
permittee's development of implementation schedules.

       When the implementation schedules for the selected CSO controls, are established, the
permit writer should determine the  appropriate mechanism for  imposing the schedule on the
permittee.  As in the Phase I permit, the permit writer should require in the Phase n permit that
the permittee meet applicable WQS.   If implementing  regulations  explicitly  authorize  a
compliance schedule, the permit writer may incorporate such  a compliance schedule for the
attainment of water quality-based effluent limitations into the Phase II permit. In all other cases,
the Phase II permit must require immediate compliance with its technology- and water quality-
based  requirements.   When  the  permittee is unable to  comply immediately with  these
requirements (as will frequently be the  case), the permit writer  should include a fixed-date
implementation schedule in an enforceable mechanism issued simultaneously with the Phase n
permit. Appropriate enforceable mechanisms may include administrative  or judicial orders. The
                                         4-23                             August 1995

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Chapter 4  	^	  	Phase II Permitting

permit writer  should  discuss with the appropriate enforcement authority the choice of the
mechanism to use in each situation.

       Exhibit  4-3  provides  example  language  requiring  compliance  with  an  LTCP
implementation schedule for the selected CSO controls. The permit writer should evaluate this
language carefolly to ensure that it is appropriate for the permittee,  (The example provided
assumes that the permittee has successfully implemented the NMC, and that the schedule is only
to implement the CSO controls identified in the LTCP.) In this permit requirement, the permit
writer should list specific activities necessary to implement selected controls.  For example, if
one of the selected CSO controls is construction of a retention basin, the permit writer should
include specific language for the various activities necessary to complete the  construction, as
shown in the  italicized  site-specific language in Exhibit 4-3.   These activities  and the
corresponding completion dates should be taken directly from the LTCP  whenever possible. In
many instances, the LTCP might contain a combination of selected CSO controls, such as
construction of additional retention basins, separation of portions of the CSS, and maximization
of flow receiving primary treatment at the PQTW treatment plant.   In these cases, the permit
writer should include activities with corresponding completion  dates for implementing each of
the selected CSO controls.  In addition to identifying compliance dates within the implementation
schedule, the permit writer should also require progress reports  to demonstrate  compliance with
the various compliance dates.  Section 4.8 provides additional guidance on appropriate reporting
requirements for the Phase II permit.

4.5.2.2   Operational Plan
       As described in Section 4.4.2, the permittee should have developed an O&M program
as part of the NMC.  Once the permittee has selected CSO controls in its LTCP, the permittee
should revise  the O&M plan developed and implemented as part of the NMC  to include the
selected CSO controls. Example permit requirements for implementing the O&M program are
contained in Exhibit 4-2, given previously.
                                         4-24                              August 1995

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Chapter 4                                                            Phase II Permttmg
    Exhibit 4-3,  Example Permit Language for Implementing Selected CSO Controls
 II. ' Long-Term Control Plan,                           . : •
 ~g% The permittee stall implemeat and" effectively operate and maintain the -CSO -conttols identiiecS i
 ":':"" long-term control plait HeimpteineBtalion'rfialaiefor ihese-comftpte shall be -as fellows:-
           Activity            '"                 , "        -.
           [insert name of adhityj                -    '       {tent1 date]      :

    1 Site-Specific Language:     ••
     1.  JRetmtim 'basin                        '"            .
      •  »  Complete design of[neamuff retention basin.. •    '       fmsert 4eteJ •
        *  Submit construstion. drawings for fmsmeif mmxtott basin,' flusett^fiatej
        «  -Initiate constructum @f foamed] retention. baste.         ^jtmsert- intej
        *  C&aplste construction of fammMI maulm basin,  ''-   finMrtd@teJ-  "
     2.  [Naned*           separation            '     '        -       -
        *  Complete design,       -                     '      Jteert JoteJ      ,
        *  Solicit bids,'      "  .            /           " :;  ' fioaort duiej  "
                 cotttmcts*            •                   ,
 NOTE:  4 compliance schedule exceeding the ten of the permit may only be included 'in the permit if
         autlioraed la the applicable Stele WQS, "         ,^;   ^/           />"'    ''  •
4.5.2.3   Post-Construction Compliance Monitoring

       Implementation of the post-construction compliance monitoring program proposed by the

permittee as part of its LTCP generally is important for determining the overall effectiveness of

the selected CSO conttol(s) in achieving compliance with the CWA, It might not be appropriate

to require the implementation of a post-construction monitoring program until construction is

well underway  or completed.   Section 4.7 presents further guidance on  Phase II permit

monitoring requirements,


4.5,2.4   Documentation for Fact Sheet/Statement of Basis

       As discussed previously, the permit writer must prepare a fact sheet or statement of basis

that describes the basis for all NPDES permit conditions.  For Phase H permits that require the

implementation of CSO controls  selected in an  LTCP, the permit writer should use the

information from the LTCP to record in the fact sheet or statement of basis the justification for

implementation of the specific CSO controls chosen by the permittee. In cases where the permit


                                           4-25                              August 1995

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Chapter 4                                                         Phase II Pemattiag

writer has determined that the permittee's proposed control levels and selected CSO controls are
not adequate to provide for the attainment of WQS, the permit writer should document the basis
for such determination (i.e.,  explain why the CSO  controls  selected by the permittee are not
adequate).

4.6    EFFLUENT LIMITATIONS
       As with the Phase I permit and consistent with 40 CFR 122.44 (NPDES requirements),
both technology- and water quality-based effluent limitations are included in the Phase n permit.
However, these two permit phases  differ with respect to the type of effluent limitation each
permit phase should require.  The  CSO Control Policy provides that in Phase I, the permit
writer  should establish narrative water quality-based effluent limitations; by comparison, the
CSO Control Policy recommends  that Phase n water quality-based effluent limitations be
expressed as numeric performance standards (e.g., number of overflow events per year) for the
selected CSO controls. Wnen sufficient CSO-related information and data are available for the
permit writer to develop numeric  water quality-based effluent  limitations, the permit writer
should do so.  This information, however,  is not  likely to be  available for inclusion in the
Phase II permit.

4.6.1  Technology-Based Requirements
       Phase n  permits should  require CSO  permittees to  continue implementation of
technology-based controls.  These technology-based controls generally include the NMC on a
BPJ basis and may also include components of any additional technology-based controls selected
in the LTCP.    The permit writer should re-evaluate and incorporate appropriate NMC
requirements in the  Phase  n permit, as discussed in Section  4.4,  The  discussion  of the
technology-based requirements presented in Section 3.6.1 is also applicable to Phase n permits.

4.6.2  Water Quality-Based Requirements
       In developing water quality-based requirements for CSOs, the permit writer should have
a thorough understanding of the applicable State WQS and any specific guidance related to wet
                                         4-26                            August 1995

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Chapter 4	Pitase If Permitting

weather conditions. This information, in addition to the LTCP information, will provide the
basis for the permit writer to develop the appropriate water quality-based requirements in the
Phase II permit.

       As described in Section IV.B.2 of the CSO Control Policy, Phase II permits should
contain "Water  quality-based effluent limits under  40 CFR  122.44(d)(l)  and  122,44(k),
requiring, at a minimum,  compliance  with, no later than the date  allowed under the State's
WQS,  the numeric performance standards for the selected CSO controls...."  The CSO Control
Policy  assumes thai adequate data will  generally not be available at the beginning of the Phase
n permitting process for the permit writer to fully and accurately assess the need for numeric
water  quality -based effluent  limits.   Consequently, the CSO  Control Policy depends on
compliance with the performance standards of the selected CSO controls to a.hic%c water quality
goals.

       The performance standards to be applied to a permittee will dc-pcnJ > >r the selected  CSO
control approach.   The  CSO  Control  Policy specifies the perform-iiva-  vtarwiards for the
presumption approach.  To satisfy the demonstration approach, the permit u nti-r vhould establish
performance standards  for the selected CSO controls that will  prtnuk  » •: the attainment of
WQS.   The following subsections discuss the water quality-related v-rMJcrjiums for  each
approach.

       In addition to performance standards designed to meet WQS. ihc permit writer should
include narrative permit language providing for the attainment of applicable WQS.  In certain
circumstances, sufficient data may exist (e.g., the permittee may have substantially completed
construction of selected CSO controls) for  the permit writer to develop numeric water quality-
based  effluent limits.  EPA's  Technical Support  Document for  Water Quality-based Toxics
Control (EPA,  1991) might provide useful insights on determining appropriate water quality-
based  effluent limitations.  Although this EPA manual is intended to address  continuous
discharges, it may provide useful information for wet weather flows.
                                         4-27                              August 1995

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Chapter 4	Phase II Permitting

4.6,2,1   Presumption Approach
       Where a permittee chooses  (and the NPDES permitting authority authorizes)  the
presumption approach, he or she will likely be required to meet numeric performance standards
(e.g., a certain number of overflow events per year).  These criteria were established in the CSO
Control Policy  because "data and  modeling of wet  weather events often do not give a clear
picture of the level of CSO controls necessary to protect WQS,"  The  CSO Control Policy
presumes, therefore, that compliance with these numeric performance standards generally will
be sufficient to meet WQS.  The permit writer will be responsible, however, for ensuring that
this presumption is  reasonable  for the CSOs to be permitted.   To determine whether the
presumption approach is reasonable, the permit  writer should review the data generated and
analysis conducted to characterize,  monitor, and model the CSS and to review the consideration
of sensitive areas by the permittee,

       Exhibit 4-4 provides example permit language for a permittee that uses the presumption
approach.  The permit  writer should evaluate  this language carefully to ensure that it is
appropriate  for the  permittee.   (The example permit  language  addressing  disinfection
requirements specifically requires reduction of a pathogen indicator (e.g.,  E.  coli) to levels that
will provide for attainment of WQS. This example language assumes that such a standard exists.
In addition,  the example permit language assumes  that the  control of harmful disinfection
products (e.g.,  chlorine) might be necessary.  In both cases,  the permit writer should customize
the disinfection requirements to those required to meet State WQS.)

       The permit writer will be responsible for eventually reviewing the permittee's evaluation
of CSO controls and determining whether water quality will be adequately protected. It is likely
that an adequate demonstration and review for attainment of WQS will not be possible until the
permittee has implemented its selected CSO controls. Therefore, the permit writer might not
complete an  evaluation,  including  consideration  of the development of numeric water quality-
based effluent  limitations, until the post-Phase  H CSO permitting.  In  any case, use  of the
presumption approach does  not  shield a permittee from the possibility that additional controls
might eventually be necessary in order to attain water quality  objectives.

                                          4-28                             August 1995

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Chapter 4
                                      Phase II Permitting
       Exhibit 4-4.  Example Permit Language for Performance Standards for the
                                Presumption Approach

    llie ::pennitt€e ;shali ;coiBply with ;C!
t!ie;faH0wiBg;perfoimaa^
|6|j|iitt
                   shall eliminate or :captoie fer :tteaimenl,
       pn^l^j^
                                  ^  requawamES ::as
                                 cttraitSvSfeai! feevnla
4.6.2.2   Demonstration Approach
       Under the demonstration approach, the permittee should be required to show that the
selected CSO controls will not cause or contribute to the exceedance of WQS.  In a receiving
water with pollution sources other than the permittee's CSOs, this may be accomplished through
the watershed approach.  The permit writer will be responsible for ensuring that the permittee
demonstrates that the selected CSO controls are adequate to provide for the attainment of WQS.
The specific performance standards that should be included in a permit will depend on the CSO
                                         4-29
                                             August 1995

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Chapter 4	Phase II Permitting

controls selected.  This manual does not provide example permit language for the demonstration
approach because such language will be site-specific and based on the permittee's demonstration.
However, the permit writer should attempt to draft permit language in terms of performance
standards  or other  clear specific  standards similar in type  to  the  examples provided  in
Exhibit 4-4 for the presumption approach.  Not all selected CSO controls (e.g., extensive use
of BMPs) lend themselves to specific numeric performance  standards.  However, the permit
writer should still attempt to develop permit conditions that will hold die permittee accountable
for implementing CSO controls as planned  (e.g.,  specifying  implementation and scheduled
evaluation of BMPs).

4.7    M0NITOEING
       Monitoring is generally necessary to 1) evaluate the water quality tmp-uts from CSOs on
receiving waters and the effectiveness of CSO controls and 2) determine compliance with permit
conditions and ultimately the attainment of WQS.   The first type  of  rn.'nu.Tinp  should be
conducted during the Phase n permit term and should be  sufficient IP e%alujic water quality
impacts of CSOs on the receiving water bodies and to evaluate the effects L-HOA »>! CSO controls
during the construction/implementation period.  The latter type t»S ni.»nu.»nnj!  should be
conducted after construction of selected CSO controls has been completed anJ sh. 

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    Chapter 4	Phase H PermMng
    
           Permit monitoring conditions should be clear and concise, maintaining flexibility to
    account for site-specific factors.  Where possible, to ensure that the conditions are enforceable,
    the permit  writer should develop permit conditions that incorporate specific elements of the
    submitted plan rather than general requirements. The permit writer may copy specific portions
    of the proposed plans into the permit.
    
           Exhibit 4-5 presents an example of site-specific permit language. (The pollutants listed
    in Exhibit 4-5 are included as an example only and are not intended  as a  mandatory list of
    required monitoring parameters.  Permit language and  the list of pollutants to be monitored
    should be developed to reflect the permittee's site-specific characteristics.)  In addition, the
    permit writer should require the permittee to monitor appropriate measures of success, developed
    as part of the LTCP.
    
           EPA cautions the permit writer against requiring  implementation of the monitoring plan
    by  reference.  This approach might be  more difficult to enforce because of the possible
    ambiguity of such language.
    
           If CSOs are causing substantial  water quality impacts, the permit writer may want to
    require special characterization studies,  including the following:
    
           *  Sediment studies
           *  Whole effluent toxicity testing
           *  Biological assessments.
    
           This type of monitoring, generally a  short-term study,  can be required as  a special
    condition.  Typically, such a study is required in response to specific information indicating that
    water quality is being affected.  The permit writer may  want to develop permit conditions that
    require: 1) a separate monitoring plan to be developed for each special study, 2) the plan be
    submitted for review prior to performing the monitoring, and 3) the submission of a final report
    to the permitting authority within a specified time after  study completion.
                                              4-31                               August 1995
    

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    Chapter 4
    Phase II Permitting
                 4-5,           Permit           for Site-Specific
    Siu-Sjpeqjic Langmg e: : , ; '; . .; -:"
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    typmpnette aamteij times-per year* '•• . ' ' ' . ' ''-•''"
    2. The coaym$lt£ skatt fre from the staff -affib^ 'i!isiA®Fg€ umil if wift , the
    period mffi to 24 ftsars at the fattening Gl® otajalls j^eit^appmpfiate, MufttftcsSionj. 21e " .
    composite sample, shall be collected flasett ,8fpmprtate number] Ames. per year, lins&i appmpnale
    snwft«f during the, feriod. from Mo$ - October ofyi\ptu>eft' ttpjmjiriiiif mwimber] "during -the
    period fi-0m November ~ ApriL The permittee- sftsff sabwf--fhjt remits no later i&m Mevembfp Jftffr»rf
    May 3Ist, respective^* : vs'bjc^ ,
    ,. '" . :?"* : "': ' '"'
    *I^raraeters listed in tMs exhibit are e?carapl« oaiy. The list of parameters to raesillor mw& be
    developed ea a stle^pecifie basis, . ,:
           The permit writer should review the monitoring plans carefully to verify that the design
    ensures that CSO information is correlated with water quality impacts; otherwise, the results of
    the studies might not provide conclusive  evidence of the cause of impact,  In addition, other
    studies might be needed in conjunction with these special studies. For example, sediment studies
    might not be meaningful  without a contaminant transport modeling study,  and a bioassay
    performed without toxicity data and CSO data might not provide meaningful results.
                                              4-32
            August 1995
    

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    Chapter 4	 	Phase H Permitting
    
    
           For additional information on these types of testing, the permit writer is referred to the
    
    Combined Sewer Overflows—Guidance for Monitoring and Modeling (EPA, 1995d).
    
    
    4.8    REPORTING
    
           Four types of reporting requirements relating to CSO controls should be included in the
    Phase  B permit:  1) re-evaluations associated with and reports/recordkeeping to document
    
    continued implementation of the NMC, 2) progress reports associated with implementation of
    
    long-term CSO controls, 3) monitoring data, and 4) other pertinent information (e.g., sensitive
    
    area reassessment):
           «  NMC Implementation—Examples of recordkeeping requirements associated with the
              ongoing implementation of the NMC have been incorporated into the example permit
              language associated with  NMC implementation (see Section 4.3.2).   The permit
              writer may choose to require reporting of any of this information. In addition, if the
              permit  writer chooses to require any re-evaluations associated with  any of the
              minimum controls, such as a reassessment of the pretreatment program or additional
              revisions to the municipal ordinance, the permit writer may require reporting of these
              re-evaluations.
    
           *  LTCP  Implementation  - Progress Reports—Because the implementation of the
              LTCP may be phased, the permit writer may require progress reports associated with
              the implementation of CSO controls. Exhibit 4-6 presents example permit language
              for requiring the submission of progress reports.
    
     Exhibit 4-6.  Example Permit Language for Requiring Submission of Progress Reports
     Within 14 days of-each completion date specified in [Insert appropriate section] of this permit^ the
     permittee shall submit a written progress report to the permitting authority stating whether or aot the
     particular activity was completed.  If the activity was not completed, the report shall also include (1) an
     explanation of the faiiaxe to accomplish the. activity, (2) actions taken by the permittee to correct the
     situation,, and (3) an estimate of when the activity will be completed.
               Monitoring Data—Monitoring data collected during Phase n should be submitted to
               the NPDES permitting authority on a scheduled basis.  Exhibit 4-5 provides example
               permit language that includes reporting requirements for Phase II monitoring.
    
               Other Information—The permit writer should consider  other applicable reporting
               requirements.  Depending on whether the permittee has chosen to implement the
               presumption or the demonstration approach, for example, it might be appropriate to
               require the permittee to report  the number of overflow  events or document other
                                              4.33                         -     August 1995
    

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    Chapter 4	Phase II Permitting
    
    controls selected.  This manual does not provide example permit language for the demonstration
    approach because such language will be site-specific and based on the permittee's demonstration.
    However, the permit writer should attempt to draft permit language in terms of performance
    standards  or other  clear specific  standards similar in type  to  the  examples provided  in
    Exhibit 4-4 for the presumption approach.  Not all selected CSO controls (e.g., extensive use
    of BMPs) lend themselves to specific numeric performance  standards.  However, the permit
    writer should still attempt to develop permit conditions that will hold die permittee accountable
    for implementing CSO controls as planned  (e.g.,  specifying  implementation and scheduled
    evaluation of BMPs).
    
    4.7    M0NITOEING
           Monitoring is generally necessary to 1) evaluate the water quality tmp-uts from CSOs on
    receiving waters and the effectiveness of CSO controls and 2) determine compliance with permit
    conditions and ultimately the attainment of WQS.   The first type  of  rn.'nu.Tinp  should be
    conducted during the Phase n permit term and should be  sufficient IP e%alujic water quality
    impacts of CSOs on the receiving water bodies and to evaluate the effects L-HOA »>! CSO controls
    during the construction/implementation period.  The latter type t»S ni.»nu.»nnj!  should be
    conducted after construction of selected CSO controls has been completed anJ sh. 

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      Chapter 4	Phase H PermMng
      
             Permit monitoring conditions  should  be clear and concise, maintaining flexibility to
      account for site-specific factors.  Where possible, to ensure that the conditions are enforceable.
      the permit  writer should develop permit conditions  that incorporate specific elements of the
      submitted plan rather than general requirements. The permit writer may copy specific portions
      of the proposed plans into the permit.
      
             Exhibit 4-5 presents an example of site-specific permit language. (The pollutants listed
      in Exhibit 4-5 are included as an example only and are not intended as  a mandatory list of
      required monitoring parameters.  Permit language and  the list of pollutants to be monitored
      should be developed to reflect the permittee's site-specific characteristics.)  In addition, the
      permit writer should require the permittee to monitor appropriate measures of success, developed
      as part of the LTCP.
      
             EPA cautions the permit writer against requiring  implementation of the monitoring plan
      by  reference.  This approach might be  more difficult to enforce because of the possible
      ambiguity of such language.
      
             If CSOs are causing substantial  water quality impacts,  the permit writer may want to
      require special characterization studies,  including the following:
      
             *  Sediment studies
             *  Whole effluent toxicity testing
             *  Biological assessments.
      
             This  type of monitoring, generally a short-term study, can be required as a  special
      condition.  Typically, such a study is required in response to specific information indicating that
      water quality is being affected.  The permit writer may  want to develop permit conditions that
      require; 1) a separate monitoring plan to be developed for each special study, 2) the plan be
      submitted for review prior to performing the monitoring, and 3) the submission of a final report
      to the permitting authority within a specified time  after study completion.
                                                4-31                               August 1995
      

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      Chapter 4
      Phase II Permitting
                   4-5.           Permit           tor Site-Specific Monitoring ActifMes
      Site-^tedfic Lang wag e; :• • ~ ~" ,.; •'•"
      He penmttee shall 'monitor CSOs artel report results to the peimttmg authority in -accordance "»f A fte _
      jbltotoiifc:-- :..'". • • -.-;•'
      CbaisiEterisfle •
      Repertiig,
      Code-
      
      
      
      
      
      
      
      
      '
      ,;•;-
      
      
      
      
      
      
      
      JPtoamrtaf1'
      • j&nsinoiiiii
      •Anuuoniii
      :BODS- t:?;:
      BODS; ,
      
      Total ;SoqwttiM
      -'Solids'
      Total. Suspended
      Solids-
      Feoi-CtoMfoiin
      •- • Monitoring EeqtKreineafs • , .• :
      Measjiremeat ,,- . -,:
      fz^paMgr
      
      
      
      
      '.,;-.
      
      
      
      SasspteType
      Grab :
      Conqwite , , -
      <3iab-; '
      CoaaRoste
      CoD^a^te;.
      Giab /_ .-..-
      €onp»»1; '
      Gnfc.- .-:•"•" "
      1, 'The grab smtpte shall- be_ c@lle£tei within ffmsert. ^ffofrieae<:sm^&] •ofzke af 'fAe
      . follmmg^ CSO jteert,-i^f««piiafeM«^«aS0ii|. He ••gmb''simylff:.skalt ifte ffjimft ' ' °
      ajpnjpriate nmd^, times per yiiar* '• • . ••_•'. '•••'•''
      5. The - skai. be from rfte $mt -of :ite «tfi"I ir • waft . file _
      pm®$ -mt'to -exceed 24 hours at the foUftMttg &O 0taf@n$ jpsert -.ajitmjmate Metttijfata&mJ. Jibe.
      composite shall be -liiKett.-ttgpMprisie maaimj times. per yew,. ff®s&t-afipi9pri(ia®
      IUM&&J during the. period fivm May - 0&ober and^ltaserf @ppmprieite mv^erj tim&:^nng the
      period fi"0m Nammisier - Aprti. UK perm&tee-. sitofi' m%mif-:ifae'rgMt$"k& to^r than Jfowraifrgr. Jftfr-fi»l
      Afoy JI«, repeetivety, ' ' • ^---^ _ '. . ' '
      - ." ?;> • ' -- - - •--
      *Pararaeters listed In tMs exhibit are examples cmlf . The list of parameters to matte* misst. be
      dwdojprf ««astte»sp^fic:-basis» . ;• "",.:„
             The permit writer should review the monitoring plans carefully to verify that the design
      ensures that CSO information is correlated with water quality impacts; otherwise, the results of
      the studies might not provide conclusive evidence of the cause of impact,  In addition, other
      studies might be needed in conjunction with these special studies. For example, sediment studies
      might not be meaningful  without  a contaminant transport modeling study, and a  bioassay
      performed without toxicity data and CSO data might not provide meaningful results.
                                                4-32
              August 1995
      

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      Chapter 4	 	Phase H Permitting
      
      
             For additional information on these types of testing, the permit writer is referred to the
      
      Combined Sewer Overflows—Guidance for Monitoring and Modeling (EPA, 1995d).
      
      
      4.8    REPORTING
      
             Four types of reporting requirements relating to CSO controls should be included in the
      Phase  B permit:  1) re-evaluations associated with and reports/recordkeeping to document
      
      continued implementation of the NMC, 2) progress reports associated with implementation of
      
      long-term CSO controls, 3) monitoring data, and 4) other pertinent information (e.g., sensitive
      
      area reassessment):
             «  NMC Implementation—Examples of recordkeeping requirements associated with the
                ongoing implementation of the NMC have been incorporated into the example permit
                language associated with  NMC implementation (see Section 4.3.2).   The permit
                writer may choose to require reporting of any of this information. In addition, if the
                permit  writer chooses to require any re-evaluations associated with  any of the
                minimum controls, such as a reassessment of the pretreatment program or additional
                revisions to the municipal ordinance, the permit writer may require reporting of these
                re-evaluations.
      
             *  LTCP  Implementation  - Progress Reports—Because the implementation of the
                LTCP may be phased, the permit writer may require progress reports associated with
                the implementation of CSO controls. Exhibit 4-6 presents example permit language
                for requiring the submission of progress reports.
      
       Exhibit 4-6.  Example Permit Language for Requiring Submission of Progress Reports
       Within 14 days of-each completion date specified in [Insert appropriate section] of this permit^ the
       permittee shall submit a written progress report to the permitting authority stating whether or aot the
       particular activity was completed.  If the activity was not completed, the report shall also include (1) an
       explanation of the faiiaxe to accomplish the. activity, (2) actions taken by the permittee to correct the
       situation,, and (3) an estimate of when the activity will be completed.
                 Monitoring Data—Monitoring data collected during Phase n should be submitted to
                 the NPDES permitting authority on a scheduled basis.  Exhibit 4-5 provides example
                 permit language that includes reporting requirements for Phase II monitoring.
      
                 Other Information—The permit writer should consider  other applicable reporting
                 requirements.  Depending on whether the permittee has chosen to implement the
                 presumption or the demonstration approach, for example, it might be appropriate to
                 require the permittee to report  the number of overflow  events or document other
                                                4.33                         -     August 1995
      

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      Chapter 4                                                          Phase II Permitting
                performance standards.  The permit writer may also require the permittee to provide
                "measures of success" data not otherwise reported as part of the monitoring data.
                Such data might include a reduction in the number of overflow events, reduction in
                number of CSO outfalls, volume of untreated/treated CSOs, or other improvements
                in receiving water quality.  Section 2.9 discusses the different types of measures of
                success for the CSO program. In addition, any reassessments recommended by the
                CSO Control Policy, such as the reassessment of CSOs to sensitive areas, should also
                be submitted to the NPDES  permitting  authority.  Section 4.9.2 discusses special
                conditions regarding sensitive areas.
      4.9    SPECIAL CONDITIONS
             This section discusses three special conditions:   1) CSO-related bypasses, 2) sensitive
      area reassessment, and 3) reopener clauses.  The sensitive area reassessment special condition
      should appear hi any CSO permit where a CSO occurs to a sensitive area and the permittee is
      not planning to eliminate or relocate the CSO outfalls from that  area during the permit term.
      The reopener clause should appear in all Phase II permits.
      
      4.9.1  CSO-Related Bypass
             Some POTW treatment plants might have significant primary treatment capacity in excess
      of their secondary treatment capacity.  During development of the LTCP, a community might
      want to consider using this excess primary treatment capacity as  one CSO control alternative,
      which may be used in conjunction with other CSO control alternatives to ensure compliance with
      CWA  requirements.  The CSO Control Policy  outlines a process for "CSO-related bypass"
      whereby, under certain circumstances, the permit writer may allow wet weather flows to receive
      primary clarification at the POTW treatment plant and then be discharged, without these flows
      being subject to secondary treatment requirements.
      
             "Bypass." the  intentional diversion of waste  streams from any  portion of a treatment
      facility, is prohibited by NPDES regulations unless the requirements of 40 CFR 122.4l(m) are
      met. Under the regulations, to take advantage of the bypass provisions, the permittee must show
      that the bypass was unavoidable to prevent  loss of life,  personal  injury, or severe property
      damage, that there was no feasible alternative to the bypass, and that the permittee submitted the
                                               4.34                              August 1995
      

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      Chapter 4   	Phase M PermMmg
      
      required notices, After considering "its adverse effects," the NPDES permitting authority may
      approve an anticipated bypass if the permittee has met these three conditions.
      
             The  permittee is  normally responsible for documenting  compliance  with 40 CFR
      122.41(m)  on a case-by-case basis.   In  the  CSO Control  Policy,  EPA interpreted these
      regulations to allow authorization, by permit condition, of a CSO-related bypass of the secondary
      treatment portion of the POTW treatment plant in specific limited circumstances.  For permittees
      with excess primary  capacity at  the POTW  treatment  plant,  the permit writer may consider
      including a  CSO-related bypass provision  in the  permit.  When considering  whether such a
      condition is appropriate, the permit writer should consult the  information and justification for
      the bypass  submitted in the permittee's LTCP.  In addition to presenting information in the
      LTCP documenting compliance with the baseline requirements of 40 CFR 122.41(m), the CSO
      Control Policy states that, at a minimum, the LTCP "should provide justification for the cut-off
      point at which the flow will be diverted from the secondary treatment portion of the treatment
      plant, and provide a benefit-cost analysis demonstrating that conveyance of wet weather flow to
      the POTW for primary treatment is more beneficial than other  CSO abatement alternatives such
      as storage and pump  back for secondary treatment, sewer separation, or satellite treatment,"
      
             For purposes of applying the bypass regulation to CSOs, "severe property damage" could
      include situations where flows above a certain level could wash out the POTW's secondary
      treatment system. The "no  feasible alternative" requirement of the regulation can be met if the
      record demonstrates that the secondary treatment system is properly operated and maintained,
      that the system has been designed to meet secondary limits for flows greater than the peak dry
      weather flow plus an appropriate quantity of  wet weather flow, and that it is either  technically
      or financially infeasible to provide secondary treatment for greater amounts of wet weather flow.
      This analysis should include, for example, consideration of enhanced primary treatment and non-
      biological secondary treatment, as well as additional construction to increase plant capacity.  The
      NPDES permitting authority  may grant  interim authorization to bypass  that results from wet
      weather flows, which, in the absence of implementation of the nine minimum controls, would
      be  untreated from a CSO  without consideration of the feasibility  of additional construction.
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      Chapter 4	Phase II Permitting
      
      Where such interim authorization is granted, however, the permit must specify that the permittee
      is  required, as  part of its LTCP, to implement all  feasible alternatives to bypass,  including
      additional construction at the facility or other controls within the collection system.  Other bases
      supporting  a finding of no feasible alternative might also be available on a case-by-case basis.
      As part of  the consideration of possible adverse effects resulting from the bypass, the permit
      writer must determine that the bypass will not cause exceedances of WQS.
      
             Based on the technical justification developed  and submitted by the permittee, the permit
      writer should include in the permit the conditions under which a CSO-related bypass would be
      authorized, as well as specify any required treatment, monitoring, or effluent limitations related
      to the bypass event.   The  permit  writer should also include requirements for appropriate
      notification of the CSO-related bypass to the NPDES permitting authority.  The CSO Control
      Policy recommends that the permit require all wet weather flows passing the headworks of the
      PQTW treatment plant to receive at least primary clarification, solids and floatables removal and
      disposal, disinfection (where  necessary), and any  other treatment that can reasonably be
      provided.  The permit  writer may  specify monitoring requirements to determine whether a
      substantial  increase in the volume or character of pollutants introduced to the POTW occurs.
      If the POTW is required to  disinfect bypassed flows,  and if chlorine is used to disinfect, the
      permit writer may apply effluent limitations  for total residual chlorine to ensure protection of
      receiving water quality and attainment of WQS.
      
             As  stated  previously, the CSO Control Policy recommends that the LTCP provide
      adequate justification for the  CSO-related bypass and clearly define the wet weather flow
      conditions  and  flow rate at which secondary treatment capacity is exceeded.  In addition, the
      CSO Control Policy  recommends  that the  permittee demonstrate that conveying  combined
      sewage to the POTW treatment plant for primary treatment is more beneficial than other options,
      based on a cost/performance analysis.  The permit writer should use this  information to draft
      a site-specific CSO-related bypass provision that specifies the flow rate at which the CSO-related
      bypass will be allowed; any  appropriate treatment, monitoring, or effluent limitations; or other
      CSO-related bypass requirements. The permit language should indicate that bypasses that occur
                                                4-36                             August 1995
      

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      Chapter 4	Phase II PermMmg
      
      when the flow at the time of the bypass is under the specified flow rate are not authorized by
      the CSO-related bypass condition.   The permit writer should  compile  sufficient  data  and
      information in  the administrative record and  in the  permit fact sheet or statement of basis
      supporting all the requirements in 40 CFR 122,41(m)(4) for approval of an anticipated bypass.
      Exhibit 4-7 presents an example of permit language  for a CSO-related bypass.  The permit
      writer should evaluate this language carefully to ensure that is appropriate for the permittee,
      
                 Exhibit 4-7. Example Permit Language for a CSO-Related Bypass
       A CSO-related bypass of the secondary treatment portion of the POTW treatment plant is authorized when
       the flow rate to the POTW treatment plant as a result of a precipitation event exceeds [insert flow rate in
       MGD).  Bypasses thai occur when the flow at the time of the bypass is under the specified flow rate are not
       authorized under this condition and are subject to the bypass provision at 40 CFR I22.41(oi}«  In the event
       of a CSO-retated bypass authorized under this condition, the permittee shall minimize the discharge of
       pollutants to the environment.  At-a minimum.* CSO-related bypass flows must receive primary clarification,
       solids-.and floatables removal, and disinfection.  The permittee shall report any substantial changes urine
       volume.or character of pollutants being introduced into the POTW. Authorization of CSO-related bypasses
       under this provision may be modified or terminated when there is a substantial change in the volume or
       character of pollutants being introduced to the POTW,  The permittee shall provide notice 10 the permitting
       authority of bypasses authorized under this provision with 24 hours of occurrence of the bypass.
      4.9.2  Reassessment of Sensitive Areas
             Under the CSO Control Policy, the permittee's LTCP should give the highest priority to
      controlling CSOs to sensitive areas, as defined by the NPDES permitting authority.  The goal
      for controlling CSOs to these areas is  to eliminate the  CSOs or relocate them whenever it is
      physically possible and economically achievable.  If it is not possible, then the permittee should
      be required to treat the CSOs that are not eliminated or relocated to the degree necessary to
      provide  for the attainment of WQS,
      
             For CSOs to sensitive areas that were not eliminated or relocated, the permit writer
      should include in the initial Phase II permit, and  in subsequent permits,  a  special condition
      requiring the permittee to reassess the feasibility of doing so.  The permit writer should require
      the permittee to develop and submit a report  on this reassessment.  The permit writer should
      require  the permittee to evaluate the availability of new technologies that  might be useful in
      eliminating or relocating these CSOs and any changes in the permittee's economic situation that
      
                                                  4,37                               August  1995
      

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      Chapter 4                  	Phase II PermMng
      
      
      would enable the permittee to fund the required projects for eliminating or relocating the CSOs
      from sensitive areas.  Exhibit 4-8  provides example permit  language for reassessment  of
      sensitive areas  for use in Phase II and subsequent permits.  The permit writer should evaluate
      
      this language carefully to ensure that it is appropriate for the permittee.
      
      
               Exhibit 4-8. Example Permit Languap for Sensitive Area Reassessment
       [This permit condition is only appropriate for CSSs with CSOs to sensitive areas that have not been
       eMmtaated or relocated.]
      
       The pemittee shall reassess the feasibility of eliminating or relocating CSO outfalls [insert outfall
       identification numbers for CSOs to sensitive areas] discharging to [insert name of receiving water body
       or bodies corresponding to each outfall identified]/- The permittee shall consider new or improved
       techniques to eliminate or relocate overflows or changed circumstances that influence economic achievability,
       • The peitnittee shall prepare and submit to the petinitting authority a report that presents -the results of ffiis
       reassessment, including the pertnittee's recommendations regarding, the elimination or relocation of these
       outfalls. The pomittee shall submit such report no later than [insert date].
      4.9.3  Permit Reopener Clause
      
             As with any NPDES permit, the Phase II permit should include a reopener clause that
      
      authorizes the NPDES permitting authority to modify or revoke and reissue the Phase I! permit
      
      for cause,  Such cause could include a determination that the selected CSO controls fail to
      
      provide for the attainment of WQS or WQS are revised to address wet weather conditions on
      
      the basis of a use attainability analysis.
      
      
             Modifying  the Phase  II permit will   require  the  modification of any enforcement
      
      mechanism issued with the Phase II permit to maintain consistency with the modified or reissued
      
      Phase II permit.   For this reason, the permit writer should coordinate with the appropriate
      
      NPDES enforcement  authority when a Phase II permit is reopened.
      
      
             Before exercising any reopener provision, the permit writer should consider the timing
      
      of the scheduled permit reissuance.  If it is late in the five-year permit cycle, the permit writer
      
      may want to address  the changes in the context of the normal permit reissuance process.   The
                                                  4-3 g                               August 1995
      

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      Chapter 4     	Phase II Permitting
      
      
      NPDES permitting authority might have standard procedures that govern the use of reopener
      clauses, and the permit writer should follow these procedures when appropriate.
      
      
             It is possible that a generic reopener clause used in other NPDES permits is sufficiently
      
      broad to address CSOs.  Alternatively, the permit writer may revise the generic reopener clause
      to specifically include the CSO-related causes for which the Phase fl permit may  be  reopened,
      or the permit writer may include a separate reopener clause that only identifies the CSO-related
      causes for which the Phase II permit may be reopened.  Exhibit 4-9  presents example language
      for the latter case.   The permit writer should evaluate this language carefully to  ensure that it
      is appropriate for the permittee, EPA's Training Manual for NPDES Permit Writers presents
      additional information on the use of standard reopener clauses in NPDES permits (EPA, 1993).
      
      
      
                            4-9.  Example                  for Rtopeier
                 may -be modified orrcvokedi aad xefesoed, as proviled-jmsuaatw 40 CFR 122,62' afl  -124.5,
       for Ae following reasons;, K- :       : '      .         ''.!••"•     .       •,•'•" t -   '.
      
          -,,  *  To iac&de new or revised conditions developed to .eoinply. wittt any     or. Federal law or.
            _ /•• regulation thai addresses. CSOs that is adopted' or pBbn^gate&subseqpent to ttr effective- '
          :"-K  date of this permit             '-, ;            '    , ' -:'    "•            ":"
      
            «  To iaetefe new or revised conditions if aew iofonoaiion, mt a^aiatte at the lime-
          :     • issoaiKe, ipdicates tot CSOr-coottols impost unier the perMt.have     to
               of State WQS$,      = ,              - '' •$% •     .....'"•'•'            '       .
      
        •= i- *  To iuclade new or itvised conditions based on nwlofonnattea        'from impleiwarticm of
               the loog-tenii-control
                 tMs permit -may be modified or revoked and reissued Ibr'aay reason specified- in
        40 X3F1 122.62.     -,' :   .                  ./:'  .  '        •  ;"               •  '
                                                 4-39                               August 1995
      

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                                          CHAPTERS
                                 POST-PHASE n PERMITTINiG
      
      5.1    CONTINUATION OF PHASE II
             The permit writer's responsibilities continue even after issuance of the first Phase n
      permit requiring implementation of the selected combined sewer overflow (CSO) controls from
      the long-term control plan (LTCP).  Phase II, in many cases, may extend through numerous
      five-year National Pollutant Discharge Elimination System (NPDES) permit cycles.  The number
      of cycles will depend on the length of time necessary to complete construction of the selected
      CSO controls. In cases where construction will take more than five years, the permit writer
      should coordinate with the NPDES enforcement authority to ensure thai a compliance schedule
      for implementation of CSO controls is contained in an appropriate enforceable mechanism.
      
             The permit writer should  continue  to  include in subsequent  Phase  II  permits any
      conditions  that require the  permittee to  implement the selected CSO  o'nirols.  continue
      implementation of the nine minimum controls and require reassessment of o\crtl »*\ to sensitive
      areas.  The requirement to implement the post-construction  compliance ni »n:i Ting program
      should be included in a Phase H permit to evaluate water quality impad- ?r.>n> CSOs and the
      effectiveness of CSO controls (in cases where some of the selected CSO  «..>n:rolv have been
      completed) and in the first post-Phase II permit to determine compliance u nf permit conditions
      and ultimately the attainment of WQS. Chapter 4 provides specific mfornijn.»n on these Phase
      II permit conditions.
      
             In addition, the permit writer should continue to work  closely with the permittee during
      these subsequent permit cycles.  The permit writer should continue to require the permittee to
      periodically report the status of implementation of the selected CSO controls (see Section 4.8).
      Continued involvement by the permit writer is critical to the development of the NPDES permit
      following implementation  of the selected CSO controls.
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      Chapter 5	Post^Phme II Permitting
      
      5.2    SUBSEQUENT CSO PERMITTING
             Prior to issuing the NPDES permit for the period in which the permittee's implementation
      of selected CSO  controls is expected to be completed,  (he permit  writer should reach an
      agreement  with the permittee  on  the  implementation  of a post-construction compliance
      monitoring program (prepared during development of the LTCP) that will generate information
      and data  necessary to determine whether the selected CSO controls are achieving compliance
      with applicable State water quality standards (WQS).  The permit  writer should generally
      incorporate the requirement to conduct this post-construction monitoring program into the first
      NPDES  permit issued  following  completed construction  of the  selected CSO controls.
      Additionally, when enough water quality data have been generated, the permit writer should use
      the data to develop numeric water quality-based effluent limits as appropriate for inclusion in
      subsequent NPDES permits.
      
             When using  the data and information generated by the permittee under the Phase II
      pemit(s) to  develop  numeric water quality-based effluent limits, the permit  writer should
      consider the following questions:
      
             «   Were CSO frequency, duration, and volumes estimated or measured?
             »   Were all  pollutants of  concern  identified, including toxics, and  were overflow
                concentrations/loadings for each pollutant estimated or measured?
             *   Did the permittee identify and  monitor for pollutants addressed by applicable State
                water quality criteria?
             *   Did the permittee obtain data on ambient background concentrations of pollutants of
                concern?
             *   Were appropriate flow values  for receiving water bodies  used?  State WQS may
                specify the flows under which water quality criteria must be achieved.
             »   If applicable,  were mixing zones calculated in accordance with State standards or
                policies?
             *  Was the cumulative  impact of multiple CSOs to the same receiving water body
                considered?
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      Chapter 5	Post-Phase B Permitting
      
             *   Were other point and  nonpoint  sources of pollutants  within the same  watershed
                considered?
             *   Was the model used suitable for wet weather episodic discharges?
             *   Were antecedent conditions appropriately used in setting up the model?
             *   Was information obtained  on the most sensitive and most affected  areas  (e.g.,
                shellfish propagation, drinjdng water supply)?
      
             The permit writer might need additional information and data depending on the policies
      and procedures used by the NPDES permitting authority to evaluate water quality impacts and
      develop numeric water quality-based effluent limits.  The scientific/technical issues affecting
      determination of the need for water quality-based effluent limits for CSOs might be different
      from those commonly used by permit writers for continuous  wastewater discharges from other
      point source categories.  For example, use of chronic criteria  designed for a particular low flow
      scenario might not apply during wet weather flow conditions when CSOs are likely to occur.
      In addition, State WQS might have been revised to better reflect receiving water  body uses
      during wet weather conditions.
      
             Therefore, the U.S. Bavironmental Protection Agency  recommends that the permit writer
      involve appropriate WQS  authorities in evaluating whether CSOs will achieve  WQS and
      developing numeric water quality-based effluent limits.  The Technical Support Document far
      Water Quality-based Toxics Control (EPA, 1991) might provide some insight in developing water
      quality-based effluent  limitations.  Although this EPA manual is intended to address continuous
      discharges, it may provide useful  information for wet weather flows.
      
             Due to the possible combined effect of pollutant sources (e.g., other point and nonpoint
      sources) or the existing condition  of the receiving water body, chemical-specific water quality-
      based effluent limits established specifically for CSOs might not result in the attainment of WQS
      for a particular receiving water body.  In these cases, the NPDES permitting authority should
      consider developing one or more  total maximum daily loads (TMDLs) for the receiving water
      body for the pollutants in CSOs exceeding WQS.  (See Section 3.5,1.4 for additional discussion
      
                                                5.3                              August 1995
      

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      Chapter 5 _ Post-Phme II Permitting
      
      of TMDLs.)  If a TMDL is established for a receiving water body to control  all pollutant
      sources of a particular pollutant, the numeric water quality-based effluent limits for that pollutant
      in a CSO must be consistent with the wasteload allocation established for the CSOs (see 40 CFR
             After the permittee has completed construction of the selected CSO controls, the permit
      writer can consider for the last Phase n permit or the first post-Phase II permit the use of
      biocriteria, sediment criteria, and whole effluent toxicity testing to evaluate the overall effect of
      CSOs on receiving water bodies. Use of these requirements will depend on the need to 1) assess
      toxicity in the receiving water body, 2) prevent future impacts, or 3) remediate existing receiving
      water body degradation.  Again, the  permit writer should consult with the appropriate State
      WQS authorities and enforcement staff to determine whether such requirements in the permit are
      warranted and to establish the specific requirements for the CSOs of concern.
                                                 5-4                               August 1995
      

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                                         APPENDIX A
                  COMPILATION OF EXAMPLE CSO PERMIT CONDITIONS
      This appendix is a compilation of all of the example CSO permit cofiditions contained in the
      exhibits in Chapters 3 and 4 of this manual, it is intended for reference purposes only, and does
      not necessarily represent the Agency's recommendations for CSO permit language in all cases.
      Permit conditions should be developed based on careful consideration of site-specific factors.
                                       PHASE I PERMIT
      
      The permittee is authorized to discharge from the CSO outfalls listed below and additional CSO
      outfalls within the boundaries of the permittee's jurisdiction identified after the effective date of
      the permit.   The permittee shall ensure  that all  CSOs  from the CSS comply with  the
      requirements of [Insert appropriate permit sections containing CSO requirements] and other
      pertinent portions of this permit,
      
             Outfall Number         Overflow Outfall Location      Receiving...W|ter.B.Qdy
      
             [insert number]         [insert latitude/longitude         [insert name of
                                    (street address optional)]      receiving water body]
      
      I.   Effluent Limits
      
      A.  Technology-based requirements for CSOs
      
      The permittee shall comply with the following technology-based requirements:
      
          1.    The permittee shall implement proper operation  and maintenance programs for the
                sewer system and all CSO outfalls to reduce the magnitude, frequency, and duration
                of CSOs. The program shall consider regular sewer inspections; sewer, catch basin,
                and regulator cleaning; equipment and sewer collection system repair or replacement,
                where necessary; and disconnection of illegal connections.
      
          2.    The permittee shall implement procedures that will maximize use of the collection
                system for wastewater storage that can be accommodated by the storage capacity of
                the collection system in order to reduce the magnitude, frequency, and duration of
                CSOs.
      
          3.    The permittee shall  review and modify,  as  appropriate, its existing pretreatment
                program to minimize CSO impacts from the discharges from Eondoinestic users.
      
                [Alternative  language for  a  permittee without aa  approved pretreatment
                program:] The permittee shall evaluate the CSO impacts from nondomestic users and
                take appropriate steps to minimize such impacts.
                                               A-l                             August 1995
      

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      Appendix A                              Compilation of Example CSO Permit CondM&m
          4.    The permittee shall operate the POTW treatment plant at maximum treatable flow
                during all wet weather flow conditions to reduce the magnitude,  frequency, and
                duration of CSOs.  The permittee shall deliver all flows to the treatment plant within
                the constraints of the treatment capacity of the POTW,
          5.    Dry weather overflows from CSO outfalls are prohibited.  Each dry weather overflow
                must be reported to the permitting authority as soon as the permittee becomes aware
                of the overflow.  When the permittee detects a dry weather overflow, the permittee
                shall begin  corrective action immediately.   The permittee shall inspect  the dry
                weather overflow each subsequent day until the overflow has been eliminated.
      
          6.    The permittee shall implement measures to control solid and floatable materials in
                CSOs.
          7.
      The permittee shall implement a pollution prevention program focused on reducing
      the impact of CSOs on receiving waters.
          8.    The permittee shall implement a public notification process to inform citizens of when
                and where CSOs occur.  The process must include (a) a mechanism to alert persons
                of the occurrence of CSOs and (b) a system to determine the nature and duration of
                conditions that are potentially harmful for users of receiving waters due to CSOs.
      
          9.    The  permittee shall  monitor CSO outfalls  to  characterize CSO  impacts and the
                efficacy of CSO controls.  This shall include collection of data that will be used to
                document the existing baseline conditions, evaluate  the efficacy of the technology-
                based controls, and  determine the baseline conditions upon  which the long-term
                control plan will be based.  These data shall include:
      
                a. Characteristics of combined sewer system including the population served by the
                   combined portion of the system and locations of  all CSO outfalls in the CSS
      
                b. Total number of  CSO events  and the frequency and  duration of  CSOs for a
                   representative number of events
      
                c. Locations and designated uses of receiving water bodies
      
                d. Water quality data for receiving water bodies
      
                e. Water quality impacts directly related to CSOs  (e.g.,  beach closing, floatables
                   wash-up episodes, fish Mis).
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      Appendix A                              Compilation of Example CS0 Permit CoiuKtwm
      B.  Water quality-based requirements for CSOs
      
      The permittee shall not discharge any pollutant at a level that causes or contributes to an in-
      stream excursion above numeric or narrative criteria developed and adopted as part of [insert
      State name] water quality standards,
      
          Site-Specific Language:
      
          1,    The permittee shall not discharge any floating debris,  oil, grease, scum, foam, or
                other objectionable materials that may result in amounts sufficient to be unsightty or
                otherwise objectionable or to constitute a nuisance under State law.
      
          2,    The permittee shall not discharge settleable solids, sedimentst sludge deposits,
                or suspended particles tftat may coat or cover submerged surfaces,
      
          5,    The permittee shall not discharge any pollutants thai may impart undesirable
                odors, tastes, or colors to the receiving water body or to the aquatic life found
                therein,  may endanger public health, or may result in the dominance of nuisance
                species.
      
      n.  Reporting Requirements
      
      A.  Reporting implementation of nine muiiminn controls
      
      The permittee shall submit documentation that demonstrates implementation of each of the nine
      minimum controls  that  includes the elements below.   The  permittee shall submit this
      documentation to the permitting authority on or before [insert due date],
      
                           [insert appropriate list of documentation  items] '
      
      HI. Long-Term Control Plan
      
      The permittee shall develop a long-term control plan that will include the elements contained in
      Sections HI.A through DJ.D below and shall submit the plan elements in  accordance with the
      schedule contained in Section IDLE:
      
      A,  Public Participation
      
          The permittee shall prepare and implement a public participation plan that outlines how the
          permittee will  ensure  participation of the  public throughout the long-term control plan
          development process.
                                                A-3                              August 1995
      

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      Appendix A                              Compilatwn of Example CSO Permit Conditions
      B.  CSS Characterization
      
          The permittee  shall develop and implement a plan that will result in a comprehensive
          characterization of the CSS developed through records review, monitoring, modeling, and
          other means as appropriate to establish the existing baseline conditions, evaluate the efficacy
          of the CSO technology-based controls, and determine the baseline conditions upon which
          the long-term control plan will be based.  The characterization shall adequately address the
          response  of the CSS to various precipitation events;  identify  the  number,  location,
          frequency, and characteristics of CSOs; and identify water quality impacts that result from
          CSOs.
      
          To complete the characterization, the permittee shall employ the following methods:
      
          1.    Rainfall	Records Review.  The permittee shall examine the complete rainfall records
                for the geographic areas of the CSS and evaluate the flow variations in the receiving
                water body to correlate between the CSOs and  receiving water conditions,
      
          2,    CSS Records Review.  The permittee shall review and evaluate all available CSS
                records and undertake field inspections and other necessary activities to identify the
                number,  location, and frequency of CSOs and their location relative to sensitive areas
                (as identified in 111.6,4) and to pollution sources, such as significant industrial users,
                in the collection system.
      
          3.    CSQ and Water  Quality Monitoring.  The  permittee shall develop and  submit a
                monitoring program that measures the frequency, duration,  flow rate, volume, and
                pollutant concentration of CSOs and assesses the  impact of the CSOs on  receiving
                waters.  Monitoring shall be performed at a representative  number of CSOs for a
                representative number of events.  The monitoring program shall include CSOs and
                ambient  receiving water body monitoring and,  where appropriate, other monitoring
                protocols, such as biological assessments, toxicity testing, and sediment sampling.
      
          4.    Identification of  Sensitive Areas.   The permittee shall identify sensitive areas to
                which its CSOs occur.   These areas shall include Outstanding National  Resource
                Waters,  National Marine Sanctuaries, waters with threatened or endangered species
                and their designated critical habitat, waters with  primary contact recreation, public
                drinking water intakes or their designated protection areas,  shellfish beds, and  any
                other areas  identified  by the permittee or permitting authority, in coordination with
                 appropriate State or Federal agencies.
      
           5.    CSS and Receiving Water Modeling.  The  permittee may  employ models, which
                 include appropriate calibration and verification with field measurements, to aid hi the
                 characterization.  If models are used, they shall be identified by the permittee along
                 with an explanation of why the model was selected and used in the characterization.
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      Appendix A                              Compttation of Example CSO Permit Conditions
      C.  CSO Control Alternatives
      
          1.    Development of CSO Control Alternatives.  The permittee shall develop a range of
                CSO control alternatives that would be necessary to achieve [insert appropriate
                range of levels of control (e.g., zero overflow events per year, an average of 1
                to 3, 4 to 7, and 8 to 12 overflow events per year)].  The permittee shall consider
                expansion of  the  POTW treatment plant secondary and  primary capacity  as an
                alternative.
                Alternatives presented must give the  highest priority to controlling CSOs to the
                sensitive areas identified in IILB.4 above.  For such areas, the alternatives included
                in the plan must (1) prohibit new or significantly  increased CSOs, (2) eliminate or
                relocate CSOs from  such  areas  wherever physically  possible and economically
                achievable, except where elimination or relocation  would provide less environmental
                protection  than  additional  treatment,  (3) where  elimination  or relocation is not
                physically possible or economically achievable or would provide less environmental
                protection than additional treatment, provide the  level of treatment for remaining
                CSOs deemed necessary to meet water quality standards for full protection of existing
                and designated uses.
      
          2.    Evaluation of CSO Control Alternatives. The permittee shall evaluate each of the
                alternatives developed in accordance with HI.C.I to select the CSO controls that will
                ensure compliance with CWA requirements.
      
          3.    Cost/Performaiice_Considerations.    The  permittee  shall  develop  and  submit
                cost/performance curves that demonstrate the  relationship among the  set of CSO
                control alternatives that correspond to  the ranges identified in III.C.I above,
      
      D.  Selected CSO Controls
      
      Once the permittee has selected the CSO controls in consultation with the permitting authority,
      the permittee shall submit the following:
      
           1.    Implementation Schedule. The permittee shall submit a construction schedule for the
                selected CSO  controls as part of the implementation schedule.  Such schedules may
                be phased based on the relative importance of the adverse  impacts on water quality
                standards and on the permittee's financial capability.
      
           2.    Operational Plan. The permittee shall submit  a revised operation and maintenance
                plan  that addresses  implementation of the  selected CSO  controls.   The revised
                operation and maintenance plan shall maximize the removal of pollutants during and
                after each precipitation event using all available facilities within the collection and
                treatment system.
      
           3.    Post-Construction Compliance MonitoringJ^rograni. The permittee shall develop and
                submit a post-construction monitoring program that (a) is  adequate to ascertain the
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      Appendix A                              Compilation of Example CSO Permit Conditions
                effectiveness of the CSO controls and (b) can be used to verify attainment of water
                quality standards,  The program shall include a  plan  that details the monitoring
                protocols  to  be followed, including  CSO and  ambient monitoring and,  where
                appropriate, other monitoring protocols,  such  as biological assessments,  whole
                effluent toxicity testing, and sediment sampling,
      
      E,  Schedule and Interim Deliverables
      
      The following reports shall be developed in accordance with the requirements specified  in
      Sections in. A through IJI.D  and  submitted to the permitting authority by the dates  specified
      below;
      
          1.    Public Participation Plan, as required in Section IE, A, shall be submitted on  or
                before [insert due date].
      
          2.    CSS Characterization Monitoring and Modeling Plan, as required in Section IILB,
                shall be submitted  on or before [insert due date].
      
          3.    CSS CbMacteri.2atiQn^onitoring and Modeling  Results, including identification  of
                sensitive areas, as required in Section III.B, shall be submitted on or before  [insert
                due date].
      
          4.    CSO  Control  Alternatives Identification, as  required in Section ffl.C.l, shall  be
                submitted  on  or before [insert due date].
      
          5.    CS_Q_CQJtttroU	Evaluation and Cost Performance	Curves  for  the  selected CSO
                controls, as required in Sections  IH.C.2 and 3,  shall  be  submitted on  or  before
                [insert due date],
      
          6.    Implementation..Schedule, as required  in Section III.D.I, including any supporting
                analyses, shall be submitted on or before [insert due date].
      
          7.    Operational Plan revised to reflect selected  CSO controls, as required in Section
                III.D.2, shall  be submitted on or before  [insert due date].
      
          8.    Post-Construction Compliance Monitoring Plan, as required in Section DGLD.3, shall
                be submitted  on or before [insert due date],
      
      IV, Special Conditions
      
      This permit may be modified or revoked and reissued, as provided pursuant to 40 CFR  122.62
      and 124.5, for the following  reasons:
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      Appendix A                              Compilation of Example CSO Permit Conditions
          •  To include new or revised conditions developed to comply with any State or Federal
             law or regulation that addresses CSOs that is adopted or promulgated subsequent to
             the effective date of this permit
      
          *  To include new or revised conditions if new information, not available at the time of
             permit issuance,  indicates that CSO controls imposed under rhe permit have failed to
             ensure the attainment of State water quality standards
      
          *  To include new or revised conditions based on new information generated from the long-
             term control plan.
      
      In addition, this permit may be modified or revoked and reissued for any reason specified in 40
      CFR 122.62.
                                                A-?                              August 1995
      

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      Appendix A                              Compilation of Example CSO Permit Conditions
                                       PHASED PERMIT
      
      The permittee is authorized to discharge from the outfalls listed below in accordance with the
      requirements of [insert appropriate permit sections containing CSO requirements] and other
      pertinent provisions of this permit.
      
            Overflow Number        Overflow Outfall Location      Receiving Water Body
      
             [Insert number]         [insert latitude/longitude     [insert receiving water
                                     (street address optional)]             body]
      
      I.  Effluent Limits
      
      A.  Technology-based requirements for CSOs
      
      The permittee shall comply with the following technology-based requirements;
      
          1.    Conduct proper operations and regular maintenance programs.  The permittee shall
                implement the operation and maintenance plan  for the CSS that will include the
                elements listed below.  The permittee also shall update the plan to incorporate any
                changes to the system and shall operate and maintain the system according to the
                plan.  The permittee shall keep records to document the implementation of the plan.
      
                Site-Specific Language:
      
                Designation of a Manager for Combined Sewer System.  The permittee shall designate
                a person to be responsible for the wastewater collection system and serve as the
                contact person regarding the CSS.
      
                Inspection and Maintenance of CSS.  The permittee shall inspect and maintain all
                CSO structures, regulators, pumping stations, and tidegates to ensure that they
                are in good working  condition and adjusted to minimize CSOs and prevent tidal
                inflow.  The permittee shall inspect, or cause to  be inspected, each CSO outfall
                at an appropriate frequency to ensure no dry weather overflows are occurring.
                The inspection shall include, but is not limited to,  entering the regulator structure
                if accessible, determining the extent of debris and grit buildup, and removing any
                debris that may constrict flow,  cause  blockage, or  result in  a dry weather
                overflow. The permittee shall record in a maintenance log book the results of the
                inspections.  For CSO outfalls that are inaccessible, the permittee may perform
                a visual check of the overflow pipe to  determine whether or not the CSO is
                occurring during dry weather flow conditions.
      
                Provision for Trained Staff.  The permittee shall  ensure the availability of trained
                staff to carry out the operation, maintenance,  repair, and testing Junctions required
                to ensure c&mpliance with the terms and conditions of this permit.  Each staff
                member shall receive appropriate training.
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      Appendix A                             Compilation of Example CSO Permit Conditions
                Allocation of Funds, for O&M.   The permittee shall allocate adequate funds
                specifically for operation and maintenance activities.  The permittee shall submit
                a certification of assurance from the appropriate local government entities that the
                necessary funds, equipment, and personnel have been or will be committed to
                carry out the O&M plan.
      
          2.    Maximize use of the collection system for storage.  The permittee shall maximize the
                in-line  storage  capacity.   The   permittee  shall  keep  records  to  document
                implementation,
      
                Site-Specific Language:
      
                The permittee shall 1) maintain all  dams or diversion structures at ifieir current
                heights {as of the date of permit issuance) or greater, 2) minimize discharges from
                the CSO outfall locations  designated as [insert appropriate designation] until the
                specified capacity of the /named] Combined Sewer Retention Bdstn t$ used to store
                the overflow for later treatment at the plant, and 3} keep m i «rjj  of the flow
                entering  and leaving the [named] Combined Sewer Retention /Lam
      
          3 .    Review and modify pretreatmeni program. The permittee shal U , »n: tnuc u > implement
                selected CSO controls to minimize the impact of nondome^iiv di^harces on CSOs.
                The  permittee  shall re-evaluate at  an appropriate frequent  u nether  additional
                modifications to its pretreatrnent program are feasible or of rr-*-tivj!  ^Sue,  The
                permittee shall keep records to document this evaluation anJ irnpk-meruauon of the
                selected  CSO controls  to  minimize CSO  impacts  result UK- tn»m n^ndomestic
                discharges.
      
                Site-Specific Language:
      
                The permittee shall require significant industrial users iSH's > <£ u turning :o the CSS
                to minimize batch discharges during wet weather
                [Alternative language  for a  permittee without  an  appro* ed  pretreatment
                program:]  Actions to minimize impact of nondomestic discharge*- on CSQs.  The
                permittee shall continue to implement selected CSO  controls to minimize CSO
                impacts resulting from nondomestie discharges.
      
           4.    Maximize flow to POTW treatment plant.  The permittee shall operate the POTW
                treatment plant at maximum treatable flow during wet weather flow conditions/events
                and deliver  all flows to the treatment  plant within the constraints of the capacity of
                the treatment plant. The permittee shall keep records to document these actions.
      
           5.    Prohibit combined sewer overflows during dry weather.  Dry weather overflows from
                CSO outfalls are prohibited.  All dry weather overflows must be reported to the
                permitting authority within [insert appropriate number of days] days of when the
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      Appendix A                              Compilation of Example CSO Permit Conditions
                permittee becomes aware of a dry weather overflow. When the permittee detects a
                dry weather overflow, the permittee shall begin corrective action immediately. The
                permittee shall inspect the dry weather overflow  each subsequent day until the
                overflow has been eliminated. The permittee shall record in the inspection log book
                dry weather overflows, as well as the cause, corrective measures taken, and the dates
                of beginning and cessation of overflow.
      
          6.    Control solid  and floatable  materials in CSOs.   The permittee shall  implement
                measures to control solid and floatable materials in CSOs.
      
                Site-Specific Language:
      
                These control measures shall include:
      
                   *   Measures to ensure that baffles are in place to control  overflows from the
                       diversion structures or that other means are used to reduce the volume of
                      floatables.
                   *   Inspection and maintenance of the sewer system so that solid or floatable
                       materials greater than [insert size] are not present in CSOs.
      
          1.    Develop and implement pQllution^pjre^eiitiQnj?rogram. The permittee shall implement
                a pollution prevention program focused on reducing the impact of CSOs on receiving
                waters.  The  permittee shall  keep  records to  document pollution  prevention
                implementation activities.
      
                Site-Specific Language:
      
                This program shall include:
      
                   •   Street sweeping and catch basin modification or cleaning at an appropriate
                       frequency to prevent large accumulations of pollutants and debris
                   •   A public education program that informs the public of the permittee's local
                       laws that prohibit Uttering and the use of phosphate-containing detergents and
                       pesticides.
                   •   An oil recycling program.
      
          8.    Notify the  public of CSOs.  The permittee shall  continue to implement a  public
                notification plan to inform citizens of when and where  CSOs occur.  The process
                must include:
      
                a. A mechanism to alert persons using all receiving water bodies affected by CSOs
      
                b. A system to determine the nature and duration  of conditions that are potentially
                   harmful to users of these receiving water bodies due to CSOs,
                                               A-10                             August 1995
      

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      Appendix A	Compilation of Example CSO Permit Conditions
      
      
                The permittee shall keep records documenting public notification,
      
                Site-Specific Language:
      
                Within 3 montlts of the effective date of this permil, the permittee shall install and
                maintain identification signs at all CSO outfalls owned and operated by the permittee.
                The permittee must place the signs at or near the CSO outfalls and ensure that the
                signs are easily readable by the public.
      
          9.    Monitor to effectively characterize CSO, impacts and	the .efficacy, of CSQ controls.
                The permittee shall regularly monitor CSO outfalls to  effectively  characterize CSO
                impacts and the efficacy of CSO controls.
      
      B.  Water quality-based requirements for CSOs
      
      The permittee shall not discharge any pollutant at a level  that causes or contributes to an in-
      stream excursion above numeric or narrative criteria adopted as  part of [insert State name]
      water quality standards.
      
      The permittee shall comply with the following performance standards.  These standards shall
      apply during {insert average design conditions upon wtiiefa controls are based].
      
          1.    [The permit writer should select the appropriate standard below.]
      
                The permittee shall  discharge no more than  an average of [insert appropriate
                number:  4? §, or 6] overflow events per year not receiving the treatment specified
                below,
                                               [or]
                The permittee shall eliminate or capture for treatment, or storage  and subsequent
                treatment, at least 85 percent of the  system-wide combined sewage volume collected
                in the combined sewer system during precipitation events under design conditions.
                Captured combined sewage shall receive the treatment specified below.
      
                The permittee shall eliminate or remove the following mass of pollutants from the
                combined  sewage volume collected in the combined sewer system during precipitation
                events under design conditions:
      
                 [insert x]  pounds of [insert pollutant]
                 [insert y]  pounds of [insert pollutant]
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      Appendix A                              Compilation of Example CSO Permit Conditions
                [Insert the following language only if the first or second alternative is chosen
                above.]
                Any combined sewage captured shall receive a minimum of the following treatment:
      
                *  Primary clarification or equivalent.
                *  Solids and floatables disposal
                   (Insert appropriate  dMnfection requirements as necessary  to meet State
                   WQS.]
                *  Disinfection.  Fecal coiiform counts shall be maintained below [insert applicable
                   level].
                [Insert appropriate dechlorination requirements if applicable based on State
                WQS,]
      
      II.  Long-Term Control Plan
      
      The permittee shall implement and effectively operate and maintain the CSO controls identified
      in the  long-term control  plan.   The implementation  schedule for these controls  shall be  as
      follows:
      
       Activity.                                       Completion ....... Date
      
       (insert name of activity]                                                 I insert date]  .
      
          Site-Specific Language:
      
          I.    Retention basin
             »  Complete design of [named] retention basin,                        [insert date]
             •  Submit construction drawings for [named} retention basin            /insert date]
             *  Initiate construction of [named] retention basin.                     /insert date]
             *  Complete construction of [named] retention basin.                   /insert date]
      
          2.    [Named street] se\ver separation
             •  Complete design,                                                /insert date]
             *  Solicit bids.                                                      [insert date]
             *  Award contracts.                                                /insert
      NOTE:  A compliance schedule exceeding the term of the permit may onl> be included in
      the permit if explicitly authorized in the applicable State WQS.
                                               A-12                             August 1995
      

      -------
      Appendix A
      Compilation of Example CSO Permit Conditions
      HI. Monitoring Requirements
      
      Site-Specific Language:
      
      The permittee shall monitor CSOs and report results to the permitting authority in accordance
      with the following:
      • •.;•., '- Characteristic • ":
      'Reporting;, v
      ; 'Coie ' ;
      
      
      
      
      
      
      
      
      •.' Units •
      
      
      
      
      
      
      
      
      ,- Parameter* •':
      Ammonia
      Ammonia
      BOD5
      BOD*
      «~?
      Phosphorus
      Total Suspended
      Solids
      Total Suspended
      Solids
      Fecal Coliform
      Bacteria
      Monitoring Requirements- • • >;:: .
      -Measurement ' ;;
      ; ; Frequency •'•'.'./,
      
      
      
      
      
      
      
      
      .'Sample Type
      Grab
      Composite
      Grab
      Composite
      Composite
      Grab
      Composite
      Grab
       /.   The grab sample shall be collected within (insert appropriate number] minutes of the
           discharge at the following CSO outfalls /insert appropriate identification].  The grab
           sample shall be  collected /insert appropriate number] times per year.
      , 2.   The composite sample shall be collected from the start of the discharge until it stops,
           with the sample period not to exceed 24 hours at the following CSO outfalls linsert
           appropriate identification].  The composite sample shall be collected /insert
           appropriate number] times per year, [insert appropriate number] times during the
           period from May - October and [insert appropriate number] times during the period
           from November - April.  The permittee shall submit the results no later than November
           30th and May 3Ist, respectively.
       *Parameters listed in this exhibit are examples only.  The list of parameters to monitor
       must be developed on a site-specific basis.
      
      IV.  Reporting Requirements
      
      Within 14 days of each completion date specified in [insert appropriate section! of this permit.
      the permittee shall submit a  written progress report to the permitting authority stating whether
      or not the particular activity  was completed.  If the activity was not completed, the  report shall
      also include (1) an explanation of the failure to accomplish the activity, (2) actions taken by the
      permittee to correct the  situation, and (3) an estimate of when the activity will be completed.
                                               A-13
                                        August 1995
      

      -------
      Appendix A	Compilation of Example CSO Permit Conditions
      
      
      V.  Special Conditions
      
      A.  CSO-related bypass.
      
          A CSO-related bypass of the secondary treatment portion of the POTW treatment plant is
          authorized when the  flow rate to the POTW treatment plant as a result of a precipitation
          event exceeds [Insert flow rate in MGD]. Bypasses that occur when the flow at the time
          of the bypass  is under the specified flow  rate are not authorized under this condition and
          are subject to the bypass provision at 40 CFR 122.41(m).  In the event of a CSO-related
          bypass  authorized under this  condition,  the permittee shall miiumize  the  discharge of
          pollutants to the environment.  At  a minimum, CSO-related bypass flows  must receive
          primary clarification, solids and floatables removal, and disinfection. The permittee shall
          report any substantial changes in the volume or character of pollutants being introduced into
          the POTW. Authorization of CSO-related bypasses under this provision may be modified
          or terminated when there is a  substantial  change in the volume or character of pollutants
          being  introduced to  the  POTW.   The permittee  shall provide notice to the permitting
          authority  of bypasses authorized under this provision with 24 hours of occurrence  of the
          bypass.
      
      B.  Sensitive  area reassessment.
      
          [This permit condition is only appropriate for CSSs with CSOs to sensitive areas that
          have not  been eliminated or relocated.]
      
          The permittee shall reassess the feasibility of eliminating or relocating CSO outfalls [Insert
          outfall identification numbers for CSOs to sensitive areas] discharging to [insert name
          of  receiving water  body or  bodies corresponding to each outfal identffiedj.   The
          permittee shall consider new or improved techniques to eliminate or relocate overflows or
          changed circumstances that influence economic achievability. The permittee shall prepare
          and submit to the permitting authority a report that presents the results of this reassessment,
          including the permittee's recommendations regarding the elimination or relocation of these
          outfalls.  The permittee shall  submit such report no later than [insert date).
      
      C.  Reopener clause.
      
      This permit may be modified or revoked and reissued, as provided pursuant to 40 CFR 122.62
      and 124,5, for the following reasons:
      
          • To include new or revised conditions developed to comply with any State or Federal
             law or regulation  that addresses CSOs that is adopted or promulgated subsequent  to
             the effective date  of this permit
      
          * To include new or revised  conditions  if  new information, not available at the time of
             permit issuance,  indicates  that CSO controls imposed under the permit have failed to
             ensure the attainment of State WQSs
                                               A-14                             August 1995
      

      -------
      Appendix A                             Compilation of Example CSO Permit
          *  To include new or revised  conditions based on  new  information resulting from
             implementation of the long-term control plan.
      
      In addition, this permit may be modified or revoked and reissued for any reason specified in
      40 CFR 122,62.
                                              A-15                             August 1995
      

      -------
                                         APPENDIX B
          DEVELOPMENT AND REVIEW OF MONITORING AND MODELING PLAN
      
            The permit writer is likely to require the permittee to develop a monitoring and modeling
      plan.  This may be required during the application process prior to the development of the
      permit or as a permit condition.  If, during the review of the plan, the permit writer determines
      the plan is lacking information or the scope of the plan is inappropriate, the permit writer should
      note the deficiencies and require the plan to be modified and resubmitted.  Development of the
      monitoring and modeling plan may require an iterative approach to match data, informational
      needs, and available resources.  The plan may  need to change as more knowledge is gained
      about the CSS and CSOs through the early steps of data collection.
      
            Exhibit B-l outlines the major elements the  monitoring and modeling plan should
      generally contain. The permit writer should consider requesting that the permittee submit the
      monitoring and modeling plan in a specific format so that critical information can be taken from
      the plan  and incorporated into the permit  as  requirements, where  appropriate.   Extensive
      information on the development of a monitoring and modeling plan is contained in the Combined
      Sewer Overflows—Guidance for Monitoring and Modeling (EPA, 1995d).
      
            The monitoring and modeling plan should balance the costs of monitoring and modeling
      against the information needed to characterize  the combined sewer system (CSS),  combined
      sewer overflows (CSOs),  and the receiving water and to develop, implement, and  verify the
      effectiveness of CSO controls. Since monitoring data and modeling results are important factors
      in making CSO control decisions, it is crucial that collected monitoring data accurately represent
      the conditions that exist throughout the CSS, CSOs, and the receiving water. Monitoring date
      are used  as modeling  inputs and  for model calibration and verification, so accurate,
      representative monitoring data are also necessary if the permittee intends to perform modeling
      to assist in the selection of the most appropriate  CSO controls.  In some cases, a permittee may
      have a considerable amount of existing data from previous monitoring efforts and may only need
      to perform a limited amount of additional monitoring.  The permit writer should remember these
                                                                              August 1995
      

      -------
      Appendix B
      Development: and Review of Monitoring and Modeling Plan
                    Exhibit B-l. Outline of M^jor Monitoring Plan Elements
                                             B-2
                                               August 1995
      

      -------
      Appendix B                    Development and Review of Monitoring and Modeling Plan
      
      factors when reviewing any proposed monitoring and modeling plan. Although the permit writer
      should provide flexibility to allow for scheduling and budget constraints, he or she should not
      accept an inadequate monitoring and modeling plan.
      
             A review team that  has members knowledgeable in developing and  implementing
      monitoring programs should be convened to review a proposed monitoring and modeling plan.
      If the proposed monitoring and modeling plan does not meet the established goals, the permit
      writer should raise these issues  and work with the permittee to develop a monitoring and
      modeling plan that meets the established objectives. In addition, in some instances, the permit
      writer and/or the permittee may  need  to establish priorities to perform the most  critical data
      collection first and schedule additional monitoring activities within a reasonable  time period.
      
             When reviewing a monitoring and modeling plan and developing monitoring requirements
      in the permit, the permit writer should consider sampling locations, pollutants to be monitored,
      frequencies, duration including periods of rainfall  or other seasonal issues, sample types, and
      analytical methods, among other appropriate factors as listed in Exhibit B-l.  These factors are
      described in the following  discussion using examples.   The specific sampling details are
      important because the permit writer may want to incorporate them into the permit:
             *   Sampling Location—Generally, the permittee will need to collect rainfall data, flow
                 data, and pollutant data to define the CSS's hydraulic  response  to  rainfall and
                 determine CSG flows and pollutant loadings.
                 -  If sufficient existing rainfall data are  not available, the permittee may need to
                    install rain gages to collect the data.   Rain gages should be located so that they
                    provide data that are representative of the entire CSS drainage area.
                 -  To assess flow patterns and volume in the CSS, the permittee may need to select
                    some sampling locations along various trunk lines of the collection system if flow
                    data from existing monitors and at hydraulic controls (e.g., pump stations) are not
                    sufficient.  The permittee should also sample the portions of the collection system
                    that  are likely  to  receive  significant pollutant  loadings  (e.g., areas where
                    significant industrial users are located) to obtain flow and loading data.
                                                 B-3                   .           August 1995
      

      -------
      Appendix B                    Development and Review of Monitoring and Modeling Plan
                -   When monitoring CSOs, if it is  not feasible to monitor all CSOs, a defined
                    percentage of the total outfalls in the system should be sampled,  The specific
                    number of outfalls to be monitored should be based on the size of the collection
                    system, the total number of overflow locations, the number of different receiving
                    water bodies, and potential and known impacts.  If only selected locations are
                    sampled, they should represent the system as a whole or represent the worst-case
                    scenario.  For example, if all CSOs are not monitored, selected locations could
                    be chosen that represent overflows that occur most frequently, have the largest
                    pollutant loading or flow volume, or discharge to sensitive areas.
      
                -   For receiving water monitoring, the selection of appropriate locations depends on
                    the characteristics of the receiving water (e.g., size of the water body, horizontal
                    and vertical  variability), the pollutants of concern, and the location of sensitive
                    areas,
      
             •  Pollutants—CSSs need to be monitored for pollutants of concern, including pollutants
                with  water quality criteria for the specific designated use(s) of the receiving water
                and pollutants key to the attainment of the  designated use(s).  The pollutants or
                classes of pollutants recommended for monitoring in most cases include biochemical
                oxygen  demand or dissolved  oxygen, total suspended  solids,  settleable solids,
                nutrients,  toxic pollutants reasonably expected to be present, and bacteriological
                indicators.  In some cases, specific pollutants should be measured; in other cases,
                surrogates of a  pollutant  class may be used.  For example, heavy metals may be
                addressed  by only monitoring copper, lead,  and zinc because these  are the metals
                most commonly found in  CSOs.  If water quality standards for mercury and arsenic
                are being  exceeded,  however, then they should  be monitored.   The selection of
                pollutants  to be  monitored should  also be based  on the characteristics of the
                nondomesttc discharges to the collection system or watershed.   Receiving water
                monitoring may include biological assessment and sediment monitoring in addition
                to the pollutants listed above.
      
             *  Frequency of Monitoring—Frequency of monitoring should reflect the type and
                amouot  of data needed to achieve the program goals.  Monitoring programs may
                include:
      
                -  Sampling a certain size precipitation event (e.g.,  3-month,  24-hour storm)
                -  Sampling all precipitation events that result in overflows
                -  Sampling a certain number of precipitation events (i.e,, monitor until five storms
                    are collected of a certain minimum size)
      
                The precipitation events to be sampled should be separated by  an adequate duration
                so that  a  sample of worst-case conditions  is collected.   The National Pollutant
                Discharge Elimination System (NPDES) Storm Water Program uses the criterion that
                the duration between the beginning of die precipitation event sampled and the end of
                the previous measurable precipitation event be  at least 72  hours.
                                                 B-4                              August 1995
      

      -------
      Appendix B                   Development and Review of Monitoring and Modeling Plan
                An assessment  of the  monitoring  frequency  should  include consideration of  the
                following criteria:
      
                -  Relative risk of CSO impacts.  If facilities discharge to sensitive areas or high
                   quality waters, more frequent monitoring may be warranted. For example,  the
                   monitoring frequency should increase in an area  where human contact occurs
                   through swimming, boating, and other recreational activities.
                -  Variability  of discharge. CSOs with variable flows should be monitored more
                   frequently than CSOs with relatively consistent flows,
      
                For receiving water characterization, the monitoring plan should target seasons, flow
                regimes, and other critical environmental conditions.
      
             »  Duration  of Monitoring Program—The  duration of the monitoring program is
                generally based on sampling a number of storm events adequate to provide the data
                needed  to either  calibrate and  validate  the CSS  hydraulic model, or  to provide
                sufficient data to evaluate  CSO control alternatives  where a model  is not used.
                During  that period (which generally may be a season or several months), storms of
                varying intensity, antecedent dry  days, and total  volume should  be monitored to
                represent the range of conditions experienced by the CSS.  The duration should be
                sufficient to sample enough storm events to readily estimate means  and variations of
                pollutant concentrations in CSOs.  The sampling period  for flow and  occurrence
                monitoring may extend for the duration of the permit;  the  sampling  period  for
                instream monitoring or other special studies may be relatively short. When feasible,
                permit writers should coordinate monitoring requirements if the data will  be used for
                the same purpose (e.g., calculation of a wasteload allocation).
      
             *  Sample Type—The sample type  may  be composite or grab, depending on site-
                specific conditions and the intended use of the data. To determine  average loadings
                of pollutants to the receiving stream, it may  be most appropriate to  collect flow-
                weighted composites.  Because CSOs may be intermittent and the volume dependent
                upon precipitation events, however,  it may  not be appropriate to collect 24-hour
                composite samples, which  are used  for  continuous nondomestic and municipal
                wastewater discharges.  Instead it may be more appropriate to collect a composite
                over the duration of the entire discharge.  It is critical that the permittee  use sample
                types that will adequately characterize CSOs. However, the permit writer should be
                aware that the  composite samples are more resource intensive than grab samples.
                Grab samples may be appropriate if only approximate levels of pollutants are needed
                or if the most important concern is the impact of worst-case conditions (i.e., first 15
                or 30 minutes  of overflow).   In addition, grab  samples  should  be  collected  for
                pollutant parameters not amendable to compositing (e.g., pH,  bacteria).
                                                B-5                              August 1995
      

      -------
      Appendix B                    Development and Review of Monitoring and Modeling Plan
                Analytical Methods—Analytical methods should be selected pursuant to 40 CFR Part
                136, which references one or more of the following:
      
                -  Test methods in Appendix A  to 40  CFR Part 136 (i.e., Methods for  Organic
                   Chemical Analysis of Municipal and Industrial Wastewater).
                -  Standard Methods for the Analysis of Water and Wastewater (most current EPA-
                   approved edition)
                -  Methods far the Chemical Analysis of Water and Wastes
      
                The  analytical methods contained in Part 136 are test methods designed only for
                specified pollutants or parameters. For other parameters, it may be necessary for the
                permit writer to specify the analytical methods required on a case-by-case basis. For
                example,  Part 136 does not contain biomonitoring test procedures, therefore, the
                permit writer will need to specify the methods.  EPA has published recommended
                biomonitormg test protocols.
             In reviewing these elements of the monitoring and modeling plan, a"  well as the other
      
      elements listed in Exhibit B-l, the permit writer should consider the anv»un: *>t existing data the
      permittee has collected,  A permittee with  a substantial set of existtnr ii.itj  nu\ not need to-
      
      conduct additional monitoring for all the conditions addressed above
      
      
             The permit writer should also determine whether models or dau arus M<- methodologies
      specified in the monitoring and  modeling plan are appropriate for thi- CSS ark] the type of data
      
      being collected.   If the  monitoring and modeling  objectives  mduJi-  mi'»rnuunnal needs,
      modeling, or statistical, graphical, or other data analyses,  technique*- should he specified so
      
      reliable and consistent information is obtained. This wiU ensure that duu u'lleuton efforts meet
      
      the needs of the analytical methods.  Review by the appropriate member- ot the review team
      
      (i.e., statisticians or  other  experts in monitoring  and  modeling   plan  development  and
      
      implementation) will ensure that the proposed data collection and analytical methodologies will
      
      meet the stated objectives of the monitoring and  modeling plan.
      
      
             Each plan  will  need to  be evaluated on a case-by-case basis.   The permit writer may
      
      enlist the EPA permitting and/or monitoring staff in reviewing the monitoring and modeling
      plans submitted by the permittee.  If the  review team determines that the  proposed plan is
                                                B-6                              August 1995
      

      -------
      Appendix B	Development and Review of Monitoring and ModsUng Plan
      
      inadequate, then the permit writer should work with the permittee to address deficiencies in the
      plan.
                                               B-7                             August 1995
      

      -------
                                         APPENBKC
      
            The permit writer may find this checklist useful in reviewing NMC documentation
      submitted by the permittee.  However, because some items listed in the checklist may not be
      applicable to the permittee, there may not be a "yes" answer to every question.
                                              C-l                            August 1995
      

      -------
      Suggested Nine Minimum Controls Evaluation Checklist
      Evaluation Criteria
      Proper Operation and Regular Maintenance Programs for tlie
      CSS and CSO Outfalls .. • '
      Docs the O&M program describe the system, including an
      inventory of all CSO structures, equipment, and treatment
      facilities?
      Does the O&M program provide procedures for keeping this
      inventory current?
      Will the O&M program be effective in reducing the number,
      frequency, and pollutant loadings of CSOs?
      Does the O&M program:
      Include routine inspection, cleaning and maintenance, and
      repair schedules for all inventoried CSO outfalls, interceptors,
      regulators, pumping stations, and equipment including
      schedules and inspection frequencies that are appropriate for
      the system?
      Include inspections for dry weather overflows and illicit
      connections?
      Provide operating procedures and specifications for all
      equipment, structures, facilities, CSO outfalls, and off-line
      storage structures, including the hydraulic capacities of the
      collection and treatment systems, the storage capacities of the
      collection and treatment systems, and off-line storage
      capacity?
      Have in place operating procedures that reflect she hcst me of
      the system's flow and rouling control"; ?<» minimi/r C'MK.
      including procedures to identify and corral t'SS .«n! t s*>
      problems?
      Require logs or other documentation «»f i«»m|>U-u-il ,K
      -------
      Suggested Nine Minimum Controls Evaluation Checklist
      Evaluation Criteria
      Allocate resources for O&M program implementation,
      including staffing level and funding, equipment, and training?
      Evaluation Result (circle one)
      'Maximum Use of the Collection System for Storage
      Has the permittee:
      Identified portions of the CSS usable for storage and
      determined the CSS storage capacity, including configuration,
      size, and pump station capacity?
      Identified appropriate minor modifications to increase storage
      (e.g., raising existing weirs)?
      Identified potential off-line storage at existing facilities?
      implemented procedures for maximizing CSS storage
      capacity?
      Evaluation Result (circle one)
      Y* '
      
      Adequate
      
      
      
      
      
      Adequate
      No
      
      Inadequate
      
      
      
      
      
      Inadequate
      N/A .;
      
      Other
      
      
      
      
      
      Other
      Remarks
      
      
      
      
      
      
      
      
                                                                                          t
      

      -------
      Suggested Nine Minimum Controls Evaluation Checklist
      Evaluation Criteria ''"''*..'...
      Review and Modification of Pretreatraeist Programs
      ..;..•; ',...-. .. ...... :•::• 	 -. .<.•:. .... ;.•:.•„•....-..•..• -.-. 	 •_•:• _•. • , ;,<„• ,,*».•...-:-:•-,., •; 	 	 :
      Has the permittee:
      Determined whether the CSS receives nondomestic wastewater
      discharges?
      Prepared an inventory of nondomestic users who discharge to
      the CSS and evaluated the discharge constituents and suspected
      impacts from such users?
      Evaluated the potential for regulating either the volume or
      pollutant loadings from nondomestic users to the CSS during
      wet weather flow conditions?
      Modified the pretreatment program as determined appropriate?
      Evaluation Result (circle one)
      •y<*. :
      
      
      
      
      
      Adequate
      $*•;
      
      
      
      
      
      Inadequate
      N/A:?
      ••- '-.; ;:'•••'. •'
      
      
      
      
      Other
      '••'?Z'""n'- -;....^ Bemwlsa • .:,/:-: .
      -:"'"":;:;:.""'-:. : | ^ .v!.;.; . ...i-::.;:. ,-; .. '.' .. -'^ - - '
      
      
      
      
      
                                                                                          t
      

      -------
                                          Suggested Nine Minimum Controls Evaluation Checklist
      Evaluation Criteria
      Maximisation of Bloy to POTW Treatment Plant
      Has the permittee;
      Compared existing flow conditions to the design capacity of
      the collection system?
      Identified actions that could be taken to increase flows to the
      POTW treatment plant during wet weather flow conditions
      without significantly affecting treatment performance?
      Conducted plant tests to determine the plant capability to treat
      higher flows during wet weather How conditions or
      determined, using available historical data, the maximum flow
      that can be treated?
      Developed, implemented, and documented implementation of a
      flow maximization plan during wet weather flow conditions?
      Evaluation Result (circle one)
      Y«
      
      
      
      
      
      Adequate
      No
      
      
      
      
      
      Inadequate
      N/A.
      
      
      
      
      
      Other
      Remarks
      
      
      
      
      
      
                                                                                                                               a
                                                                                                                               I-
      O
      1
      Oi
      

      -------
      Suggested Nine Minimum Controls Evaluation Checklist
      Evaluation Criteria
      Prohibition of CSOs During. Dry Weather Flow Conditions
      Has the permittee:
      Developed adequate procedures to document where and when
      dry weather overflows occur, including follow-up inspections
      after dry weather overflows occur?
      Developed and instituted procedures to prevent and eliminate
      dry weather overflows, including routine inspection of
      regulators and CSO outfalls as part of the O&M plan?
      Evaluation Result (circle one)
      Y«. .
      
      
      
      Adequate
      N®
      
      
      
      Inadequate
      N;A
      
      
      
      Other
      Remarks
      
      •
      •*
      
                                                                                         t
      

      -------
                                          Suggested Nine Minimum Controls Evaluation Checklist
      Evaluation. Criteria
      Control of S,otkJ and Floatable Materials in CSO*
      Has the permittee;
      Evaluated the following technologies for the control of solid
      and floatable materials in CSOs:
      Screening materials using baffles, screens, and netting'.'
      Skimmer boats?
      Skimming from water body surface wish booms at outfalls
      in confined areas?
      Source control, which may be addressed under the
      pollution prevention program for CSO outfalls?
      Identified and addressed problems that may be created by the
      installation of the control technology?
      Implemented the appropriate control technology, considered
      and provided justification that the technology is appropriate for
      the site conditions, and is conducting associated inspections
      and regular maintenance?
      Evaluation Result 
      -------
      Suggested Nine Minimum Controls Evaluation Checklist
      -' • Evaluation Criteria.
      Pollution Prevention Program
      Has the permittee;
      Evaluated source control measures both at the government
      level (e.g., street cleaning; banning or substitution of
      products, such as plastic food containers; controlled use of
      pesticides, fertilizers, and other hazardous substances at public
      facilities) and among the public (e.g., used oil recycling,
      household hazardous waste collection)?
      Included a wide-reaching public education program?
      Evaluated mechanisms to encourage water conservation (e.g.,
      public outreach, structuring of water/sewer service charges,
      local ordinance provisions)?
      Allocated adequate resources to conduct pollution prevention
      program activities?
      Implemented and maintained detailed records of pollution
      prevention activities?
      Promoted the use of industrial/construction BMPs for storm
      water?
      Evaluation Result (circle one)
      Ye*
      
      
      
      •
      
      
      
      Adequate
      No
      
      
      
      
      
      
      
      Inadequate
      N/A
      
      
      
      
      
      
      
      Other
      Remarks
      
      
      
      
      
      
      
      
                                                                                        f
      

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      Suggested Nine Minimum Controls Evaluation Checklist
      Evaluation Criteria ' - • . • ,' •
      Public notification _ - , ' • . " •• • ; - , •
      Has the permittee:
      Evaluated options for public notification to ensure that the
      public receives adequate notification of CSO occurrences and
      CSO impacts?
      Implemented notification procedures regarding the presence of
      contaminants at critical levels in the receiving water bodies
      due to CSOs?
      Implemented procedures that notify persons reasonably
      expected to be affected by the CSO?
      Documented CSO occurrences and associated notifications?
      Installed identification signs at each CSO outfall?
      Evaluation Result (circle one)
      Y«s ' .
      
      
      
      
      
      
      Adequate
      No
      
      
      
      
      
      
      Inadequate
      : N/A1 ..
      
      
      
      
      
      
      Other
      • . . "• ' , Remarks' ' -
      
      
      
      
      
      
      
      
      

      -------
                                          APPENDEXD
      
            The permit writer may find this checklist useful in reviewing the long-term control plan
      submitted by the permittee.  However, because some items listed in the checklist may not be
      applicable to the permittee, there may not be a "yes" answer to every question.
                                                                               August 1995
      

      -------
      Suggeeted Long-Term Control Plan Evaluation Checklist
      'Evaluation Criteria
      Public Participation
      Does the public participation process seek to actively involve rate
      payers, industrial users of the CSS, persons near the impacted
      waters, and persons who use the impacted waters?
      Does the public participation plan document how the public was
      notified of public participation events?
      Docs the public participation plan include a record of the public
      participation events, including the number of people attending and a
      record or summary of comments?
      Does the public participation plan contain a summary of comments
      anti the changes or decisions made in response to public comments?
      Evaluation Result (circle one)
      Yes •
      
      
      
      
      
      Adequate
      . No
      
      
      
      
      
      Inadequate
      N/A
      
      
      
      
      
      Other
      Remarks
      
      
      
      
      
      
      

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                                           Suggested Long-Term Control Plan Evaluation Checklist
      - Evaluation Criteria- •, • rh
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      Suggested Long-Term Control Plan Evaluation Checklist
      Evaluation Criteria
      CSO Cdntrol Alternative • -
      Did the permittee develop a comprehensive list of CSO control
      alternatives?
      Did this list include alternatives from each of the four general
      categories— source controls, collection system controls, storage, and
      treatment technologies (described in Combined Sewer
      Overflows—Guidance far Long-1 «?» Control Plan fEPA, )995a{)?
      Are the CSO control alternatives that were considered described?
      Does the plan describe the process by which the CSO control
      alternatives were developed?
      Does this plan compare the environmental benefits of the CSO
      control alternatives?
      Is cost/performance information (including curves) for each of the
      CSO control alternatives provided?
      Do the cost/performance analyses evaluate a range of levels of
      controls that were developed based on the permittee's site specific
      conditions (e.g., zero overflow events per year, and averages of 1
      to 3, 4 to 7, and 8 to 12 overflow events per year)?
      Does plan describe the approach used to screen the list of CSO
      control alternatives, including the recommended screening criteria?
      Do the screening criteria include performance factors.
      implementation and operation factors, sue)) as COSH, ami
      environmental impacts (described in Combined AVurr
      Overflows—Guidance for Long-Tetm GWM/ I'lui (f I1 \ ) ''''* 
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      Suggested Long-Term Control Plan Evaluation Checklist
      Evaluation Criteria
      .Sel«d?tCeS0'Controk. ... . , ' • . .. . j , -.
      Is the presumption or demonstration approach used?
      Does the plan identify the reasons for selecting certain CSO
      controls?
      Were reasons for rejecting specific CSO controls reasonable?
      Have the NMC been integrated into the permittee's description of
      its selected CSO controls?
      Will the selected CSO controls eliminate all CSO points to sensitive
      areas?
      If not, do the data support the permittee's conclusion that
      elimination is not physically possible or economically
      achievable?
      If CSO outfalls to sensitive areas remain:
      Will these CSOs receive treatment?
      Will the CSO controls be sufficient to provide for the attainment
      of WQS?
      Have control efforts for other point and nonpoint sources of
      pollutants within the watershed been considered'?
      Will the CSO controls provide treatment or removal of floaiables
      and settleable solids equivalent to that achieved by primary
      clarification?
      Is the mechanism for solids and floatables disposal described?
      Will the disinfection of effluent be necessary based on applicable
      WQS?
      If yes, is disinfection proposed as part of the CSO controls?
      If yes, will removal of harmful disinfection chemical residuals
      be necessary?
      If no, does the infoiroation support the conclusion that
      disinfection is not necessary?
      Yes'
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      ... !*».."
      - -,
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      . it/A ...
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      Remarks •
      
      
      
      
      
      
      •
      
      
      
      *
      
      
      
      
      
      
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      Suggested Long-Term Control Plan Evaluation Checklist
      - Evaluation Criteria
      Do the selected CSO controls provide the maximum pollution
      reduction benefits reasonably attainable?
      Will the selected CSO controls provide for the attainment of WQS?
      If WQS cannot be met because of sources other than CSOs, has the
      permittee provided information on the other sources and natural
      background conditions?
      Are the selected CSO controls designed to allow cost-effective
      expansion or cost-effective retrofitting if additional controls are
      determined necessary to provide for the attainment of WQS?
      Has a TMDL been developed for the watershed?
      If so, has the permittee considered the TMDL in developing its
      LTCP?
      Evaluation Result (circle one)
      ' Yes
      
      
      
      
      
      
      Adequate
      No
      
      ^
      
      
      
      
      Inadequate
      N/A
      
      
      
      
      
      
      Other
      Remarks
      
      
      
      
      
      
      
      
      
      

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      Suggested Long-Term Control Plan Evaluation Checklist
      Evaluation Criteria
      Implementation Schedule
      Do any phased construction schedules consider:
      Eliminating CSOs to sensitive areas?
      Use Impairment?
      Do any phased construction schedules include an analysis of
      financial capability?
      Did the permittee evaluate the following faciors:
      Median household income?
      Total annual wastewiter and CSO control costs per household as
      a percent of median household income?
      Overall net debt as a percent of full market property value?
      Property tax revenues as a percent of fyll market property
      value?
      Property tax collection rate?
      Unemployment?
      Bond rating?
      Did the permittee evaluate the following factors:
      Grant and loan availability?
      Previous and current residential, commercial, and industrial
      sewer user fees and rate structures?
      Other viable funding mechanisms Mid sources of financing?
      Does the schedule include milestones for all major implementation
      activities, including environmental reviews, siting of facilities, site
      acquisition. Army Corps of Engineers permitting, etc.?
      Evaluation Result (circle one)
      Yes
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      Adequate
      No
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      Inadequate
      N/A
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      Other
      Remarks
      •.
      
      
      
      
      
      
      
      
      
      
      
      
      
      
      
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      Suggested Long-Term Control Plan Evaluation Checklist
      -• }:* * • Evaluation Criteria
      Post-Construction Compliance Monitoring
      Does the monitoring program include monitoring of CSOs that are
      representative of the impacts to receiving waters?
      Docs the monitoring program include ambient receiving water body
      monitoring at representative CSOs, as well as monitoring prior to
      CSO impacts?
      Has the receiving water body monitoring program been coordinated
      with any ongoing or planned State programs and programs of other
      permittees within the same watershed?
      Does the monitoring program include any biological parameters
      (e.g., fish, xooplankton)?
      Does the monitoring program address pollutants included in the
      water quality criteria for the specific designated uses(s) of the
      receiving water, pollutants key to the attainment of ihe designated
      water use(s), and pollutants affected by the CSO controls?
      Yes
      
      
      
      
      
      
      No
      
      
      
      
      
      
      N/A '
      
      
      
      
      
      
      Remarks
      
      
      
      
      
      
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      Suggested Long-Term Control Plan Evaluation Checklist
      Evaluation Criteria
      Does the monitoring program include appropriate measures of
      success?
      Evaluation Result (circle one) •
      Comprehensive Evaluation Result (circle one)
      ' ' **•__,
      
      Adequate
      Adequate .
      ".-!*» !
      
      Inadequate
      ^ Inadequate
      ... N*A".;
      
      Other
      Other-
      • •• • • ;\Rw«tarks , .'.
      
      
      
      

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                                           GLOSSARY1
      Average Number of Overflow  Events Per Year—The  total  number  of combined  sewer
      overflow events that occurred during the term of the permit divided by the permit term in years.
      
      Combined Sewer Overflow—The discharge from a combined sewer system to a receiving water
      of the United States prior to reaching the publicly owned treatment works treatment plant.
      
      Combined Sewer Overflow Event—The discharges from any number of points in the combined
      sewer system resulting from a single wet weather event that do not receive minimum treatment
      (i.e., primary clarification,  solids disposal,  and disinfection, where appropriate).  For example,
      if a storm occurs that results in untreated overflows from 50 different CSO  outfalls within the
      CSS, this is considered one overflow event.
      
      Combined Sewer System—A  wastewater collection system owned by a State or one  or more
      municipalities  (as defined by Section 502(4) of the Clean Water Act) which conveys sanitary
      wastewaters (domestic, commercial, and industrial wastewaters) and storm water through a
      single-pipe system to a publicly owned treatment works treatment plant  (as defined in 40 CFR
      403.3(p)),
      
      Dry Weather  Flow Conditions—Hydraulic flow conditions within the combined sewer system
      resulting from one or more  of the following:   flows of domestic sewage, ground water
      infiltration, commercial and industrial wastewaters, and any other non-precipitation event related
      flows (e.g.,  tidal infiltration under certain circumstances). Other non-precipitation event related
      flows that are included in dry weather flow conditions will be decided by  the permit writer based
      on site-specific conditions.
      
      Dry Weather Overflow—A combined sewer overflow that  occurs during dry weather flow
      conditions.
      
      Precipitation  Event—An occurrence of rain, snow, sleet, hail, or other form of precipitation.
      Precipitation events are generally characterized by parameters of duration and intensity (inches
      or millimeters per unit of time).   This definition will be highly site-specific.  For example, a
      precipitation event could be defined as 0.25 inches or  more of precipitation  in the form of rain
      or 3 inches or more of precipitation in the form of sleet or snow,  reported during the preceding
      24-hour  period at a specific gaging station.  A precipitation event could  also be defined by a
      minimum time interval between measurable amounts of precipitation (e.g., 6 hours between the
      end of rainfall and the beginning of the next rainfall).
      
      Primary Clarification or Equivalent—The level of treatment that would typically be provided
      by one or more treatment  technologies under peak wet weather  flow conditions.  Options  for
                 definitions were developed solely for the purposes of this guidance document.
      
      
                                                G-l                              August 1995
      

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      Glossary
      defining primary clarification include a design standard (e.g., side wall depth and maximum
      overflow rate), a performance standard (e.g., percent removal), or an effluent standard (e.g.,
      concentration of pollutants).  "Equivalent to primary clarification" is site-specific and includes
      any single technology or combination of technologies shown by the permittee to achieve primary
      clarification under the  presumption approach.   The  permittee is responsible  for  showing
      equivalency to primary treatment as part of the evaluation of CSO control alternatives during
      LTCP development, Primary clarification  is discussed in more detail in the Combined Sewer
      Overflows-Guidance for Long-Term Control Plan (EPA, 1995a).
      
      Sensitive  Areas—Areas of particular environmental significance or  sensitivity that could be
      adversely  affected by a combined sewer overflow, including Outstanding National Resource
      Waters, National Marine Sanctuaries, water with threatened or endangered species, waters with
      primary contact  recreation, public drinking  water intakes, shellfish beds, and  other areas
      identified  by  the permittee or National Pollutant Discharge Elimination System permitting
      authority, in coordination  with the appropriate State or Federal agencies.
      
      Solid and Floatable Materials—Solid or semi-solid materials should be defined on a case-by-
      case basis determined by  the control technologies proposed  by  the permittee to control these
      materials. The term generally includes materials that might impair the aesthetics of the receiving
      water body.
      
      Wet Weather Flow Conditions—Hydraulic flow conditions within the combined sewer system
      resulting from a precipitation event.  Since  the definition of precipitation event is site-specific,
      the permit writer should evaluate and define certain site-specific weather conditions that typically
      contribute  to  wet weather flow.   EPA encourages permit writers to include snowmelt as a
      condition that typically contributes to wet weather flow.
                                                G-2            "                  August 1995
      

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                                       REFERENCES
      U.S. Environmental Protection Agency (EPA). 1995a. Combined Sewer
             Overflows—Guidance for Long-Term Control Plan (EPA 832-B-95-OQ2).
      
      EPA.  1995b. Combined Sewer Overflows—Guidance for Nine Minimum Controls
             (EPA 832-B-95-QQ3).
      
      EPA.  1995c. Combined Sewer Overflows—Guidance for Screening and Ranking
             (EPA 832-B-95-Q04).
      
      EPA.  1995d. Combined Sewer Overflows—Guidance for Monitoring and Modeling
             (EPA 832-B-95-005).
      
      EPA.  1995e. Combined Sewer Overflows—Guidance for Financial Capability Assessment
             (EPA 832-B-95-006).
      
      EPA.  1995f. Combined Sewer Overflows—Guidance for Funding Options
             (EPA 832-B-95-0Q7).
      
      EPA.  1995g. Combined Sewer Overflows—Guidance for Permit Writers
             (EPA 832-B-9S-008).
      
      EPA.  1995h. Combined Sewer Overflows—Questions and Answers on Water Quality
             Standards and the CSO Program (EPA 832-B-95-Q09).
      
      EPA.  1993. Training Manual for NPDES Permit Writers.  (EPA 833-8-93-003).
      
      EPA.  1991. Technical Support Document for Water Quality-based Toxics Control.
             (EPA/505/'2-90-001), PB91-127415.
                                             R-l                            August 1995
      

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