[Federal Register Volume 68, Number 216 (Friday, November 7, 2003)]
[Proposed Rules]
[Pages 63042-63052]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 03-28103]


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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Parts 122 and 133

[FRL-7584-5]


National Pollutant Discharge Elimination System (NPDES) Permit 
Requirements for Municipal Wastewater Treatment Discharges During Wet 
Weather Conditions

AGENCY: Environmental Protection Agency (EPA).

ACTION: Request for comment on proposed policy.

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SUMMARY: Today, EPA is inviting comment on a proposed policy regarding 
NPDES permit requirements for treatment plants in publicly owned 
treatment works (POTWs) under peak wet weather flow conditions. 
Regulatory agencies, municipal operators of POTWs, and representatives 
of environmental advocacy groups have expressed uncertainty about the 
appropriate regulatory interpretation for such situations. Today's 
document describes both a proposed interpretation of regulations, as 
well as draft guidance to implement such an interpretation. EPA's 
intention is to ensure that NPDES requirements be applied in a 
nationally-consistent manner that improves the capacity, management, 
operation and maintenance of POTW treatment plants and collection 
systems and protects human health and the environment.

DATES: Written comments on this proposed policy must be received by EPA 
or postmarked by January 9, 2004.

ADDRESSES: Comments may be submitted electronically, by mail, or 
through hand delivery/courier. Follow the detailed instructions as 
provided in section I.B. of the SUPPLEMENTARY INFORMATION section.

FOR FURTHER INFORMATION CONTACT: For questions about the substance of 
this proposed policy, contact Kevin Weiss (e-mail at 
[email protected] or phone at (202) 564-0742) at Office of Wastewater 
Management, U.S.

[[Page 63043]]

Environmental Protection Agency (Mailcode 4203M), 1200 Pennsylvania 
Ave., NW., Washington, D.C. 20460.

SUPPLEMENTARY INFORMATION:

I. General Information

A. How Can I Get Copies of This Document and Other Related Information 
?

    1. Docket. EPA has established an official public docket for this 
action under Docket ID No. OW-2003-0025. The official public docket 
consists of the documents specifically referenced in this action, any 
public comments received, and other information related to this action. 
Although a part of the official docket, the public docket does not 
include Confidential Business Information (CBI) or other information 
whose disclosure is restricted by statute. The official public docket 
is the collection of materials that is available for public viewing at 
the Water Docket in the EPA Docket Center, (EPA/DC) EPA West, Room 
B102, 1301 Constitution Ave., NW., Washington, DC. The EPA Docket 
Center Public Reading Room is open from 8:30 a.m. to 4:30 p.m., Monday 
through Friday, excluding legal holidays. The telephone number for the 
Public Reading Room is (202) 566-1744, and the telephone number for the 
Water Docket is (202) 566-2426. You may copy 266 pages per day free of 
charge. Beginning with page 267, you will be changed $0.15 per page 
plus an administrative fee of $25.00.
    2. Electronic Access. You may access this Federal Register document 
electronically through the EPA Internet under the ``Federal Register'' 
listings at http://www.epa.gov/fedrgstr/.
    An electronic version of the public docket is available through 
EPA's electronic public docket and comment system, EPA Dockets. You may 
use EPA Dockets at http://www.epa.gov/edocket/ to submit or view public 
comments, access the index listing of the contents of the official 
public docket, and to access those documents in the public docket that 
are available electronically. Once in the system, select ``search,'' 
then key in the appropriate docket identification number.
    Certain types of information will not be placed in the EPA Dockets. 
Information claimed as CBI and other information whose disclosure is 
restricted by statute, which is not included in the official public 
docket, will not be available for public viewing in EPA's electronic 
public docket. EPA's policy is that copyrighted material will not be 
placed in EPA's electronic public docket but will be available only in 
printed, paper form in the official public docket. To the extent 
feasible, publicly available docket materials will be made available in 
EPA's electronic public docket. When a document is selected from the 
index list in EPA Dockets, the system will identify whether the 
document is available for viewing in EPA's electronic public docket. 
Although not all docket materials may be available electronically, you 
may still access any of the publicly available docket materials through 
the docket facility identified in section I.A.1. EPA intends to work 
toward providing electronic access to all of the publicly available 
docket materials through EPA's electronic public docket.
    For public commenters, it is important to note that EPA's policy is 
that public comments, whether submitted electronically or in paper, 
will be made available for public viewing in EPA's electronic public 
docket as EPA receives them and without change, unless the comment 
contains copyrighted material, CBI, or other information whose 
disclosure is restricted by statute. When EPA identifies a comment 
containing copyrighted material, EPA will provide a reference to that 
material in the version of the comment that is placed in EPA's 
electronic public docket. The entire printed comment, including the 
copyrighted material, will be available in the public docket.
    Public comments submitted on computer disks that are mailed or 
delivered to the docket will be transferred to EPA's electronic public 
docket. Public comments that are mailed or delivered to the docket will 
be scanned and placed in EPA's electronic public docket. Where 
practical, physical objects will be photographed, and the photograph 
will be placed in EPA's electronic public docket along with a brief 
description written by the docket staff.
    For additional information about EPA's electronic public docket 
visit EPA Dockets online or see 67 FR 38102 (May 31, 2002).

B. How and To Whom Do I Submit Comments?

    You may submit comments electronically, by mail, or through hand 
delivery/courier. To ensure proper receipt by EPA, identify the 
appropriate docket identification number in the subject line on the 
first page of your comment. Please ensure that your comments are 
submitted within the specified comment period. Comments received after 
the close of the comment period will be marked ``late.'' EPA is not 
required to consider these late comments. Late comments may be 
considered if time permits.
    1. Electronically. If you submit an electronic comment as 
prescribed below, EPA recommends that you include your name, mailing 
address, and an e-mail address or other contact information in the body 
of your comment. Also include this contact information on the outside 
of any disk or CD ROM you submit, and in any cover letter accompanying 
the disk or CD ROM. This ensures that you can be identified as the 
submitter of the comment and allows EPA to contact you in case EPA 
cannot read your comment due to technical difficulties or needs further 
information on the substance of your comment. EPA's policy is that EPA 
will not edit your comment, and any identifying or contact information 
provided in the body of a comment will be included as part of the 
comment that is placed in the official public docket, and made 
available in EPA's electronic public docket. If EPA cannot read your 
comment due to technical difficulties and cannot contact you for 
clarification, EPA may not be able to consider your comment.
    i. EPA Dockets. Your use of EPA's electronic public docket to 
submit comments to EPA electronically is EPA's preferred method for 
receiving comments. Go directly to EPA Dockets at http://www.epa.gov/edocket, and follow the online instructions for submitting comments. To 
access EPA's electronic public docket from the EPA Internet Home Page, 
select ``Information Sources,'' ``Dockets,'' and ``EPA Dockets.'' Once 
in the system, select ``search,'' and then key in Docket ID No. OW-
2003-0025. The system is an ``anonymous access'' system, which means 
EPA will not know your identity, e-mail address, or other contact 
information unless you provide it in the body of your comment.
    ii. E-mail. Comments may be sent by electronic mail (e-mail) to [email protected], Attention Docket ID No. OW-2003-0025. In contrast to 
EPA's electronic public docket, EPA's e-mail system is not an 
``anonymous access'' system. If you send an e-mail comment directly to 
the Docket without going through EPA's electronic public docket, EPA's 
e-mail system automatically captures your e-mail address. E-mail 
addresses that are automatically captured by EPA's e-mail system are 
included as part of the comment that is placed in the official public 
docket, and made available in EPA's electronic public docket.
    iii. Disk or CD ROM. You may submit comments on a disk or CD ROM 
that you mail to the mailing address

[[Page 63044]]

identified in section I.B.2. These electronic submissions will be 
accepted in WordPerfect or ASCII file format. Avoid the use of special 
characters and any form of encryption.
    2. By Mail. Send an original and three copies of your comments to: 
Water Docket, Environmental Protection Agency, Mailcode 4101T, 1200 
Pennsylvania Ave., NW., Washington, DC 20460, Attention Docket ID No. 
OW-2003-0025.
    3. By Hand Delivery or Courier. Deliver your comments to: EPA 
Docket Center, EPA West, Room B102, 1301 Constitution Ave., NW., 
Washington, DC, Attention Docket ID No. OW-2003-0025. Such deliveries 
are only accepted during the Docket's normal hours of operation as 
identified in section I.A.1.

C. How Should I Submit CBI To the Agency?

    Do not submit information that you consider to be CBI 
electronically through EPA's electronic public docket or by e-mail. You 
should send information that you consider to be CBI in one of two ways: 
(1) By U.S. Mail to: Kevin Weiss, Office of Wastewater Management, U.S. 
Environmental Protection Agency (Mailcode 4203M), 1200 Pennsylvania 
Ave., NW., Washington, DC 20460--Attention Docket ID No. OW-2003-0025; 
or (2) By courier or delivery to: Kevin Weiss, Office of Wastewater 
Management, U.S. Environmental Protection Agency, EPA East Building 
(Room 7334), 1301 Constitution Ave., NW., Washington, DC 20004--
Attention Docket ID No. OW-2003-0025. You may claim information that 
you submit to EPA as CBI by marking any part or all of that information 
as CBI (if you submit CBI on disk or CD ROM, mark the outside of the 
disk or CD ROM as CBI and then identify electronically within the disk 
or CD ROM the specific information that is CBI). Information so marked 
will not be disclosed except in accordance with procedures set forth in 
40 CFR part 2.
    In addition to one complete version of the comment that includes 
any information claimed as CBI, a copy of the comment that does not 
contain the information claimed as CBI must be submitted for inclusion 
in the public docket and EPA's electronic public docket. If you submit 
the copy that does not contain CBI on disk or CD ROM, mark the outside 
of the disk or CD ROM clearly that it does not contain CBI. Information 
not marked as CBI will be included in the public docket and EPA's 
electronic public docket without prior notice. If you have any 
questions about CBI or the procedures for claiming CBI, please consult 
the person identified in the FOR FURTHER INFORMATION CONTACT section.

D. What Should I Consider as I Prepare My Comments for EPA?

    You may find the following suggestions helpful for preparing your 
comments:
    1. Explain your views as clearly as possible.
    2. Describe any assumptions that you used.
    3. Provide any technical information and/or data you used that 
support your views.
    4. If you estimate potential burden or costs, explain how you 
arrived at your estimate.
    5. Provide specific examples to illustrate your concerns.
    6. Offer alternatives.
    7. Make sure to submit your comments by the comment period deadline 
identified.
    8. To ensure proper receipt by EPA, identify the appropriate docket 
identification number in the subject line on the first page of your 
response. It would also be helpful if you provided the name, date, and 
Federal Register citation related to your comments.

Acronyms Used

BOD5 five-day biochemical oxygen demand
CSO combined sewer overflow
EPA Environmental Protection Agency
I/I infiltration and inflow
NPDES National Pollutant Discharge Elimination System
POTW publicly owned treatment works
SS total suspended solids
SSO sanitary sewer overflow

II. Background

A. Why Is EPA Taking This Action?

    Wastewater collection systems collect domestic sewage and other 
wastewater from homes and other buildings and convey it to wastewater 
sewage treatment plants for proper treatment and disposal. The 
collection and treatment of municipal sewage and wastewater is vital to 
public health in our cities and towns, and to the viability of our 
receiving waters. The proper functioning of wastewater systems is among 
the most important factors responsible for the general level of good 
health enjoyed in the United States. The United States Centers for 
Disease Control and Prevention named clean water and sanitation 
technology one of the twentieth century's great public health 
achievements (see Morbidity and Mortality Weekly Report, April 2, 1999, 
v. 48, no. 12, pp. 241-243), while the National Academy of Engineering 
included such technology on its list of the 20 engineering achievements 
that had the greatest impact on quality of life in the twentieth 
century. (National Academy of Engineering, press release, February 22, 
2000).
    Municipal collection systems and treatment facilities are an 
extensive, valuable, and complex part of the nation's infrastructure. 
In the last twenty years, communities have spent $1 trillion in 2001 
dollars on drinking water treatment and supply and wastewater treatment 
and disposal (see The Clean Water and Drinking Water Infrastructure Gap 
Analysis, EPA, September 2002). Another source estimates that 
wastewater treatment and collection systems represent about 10-15 
percent of the total infrastructure value in the United States. 
(Fragile Foundations: A Report on America's Public Works. Final Report 
to the President and Congress. National Council on Public Works 
Improvement. February 1988.) The collection system and treatment 
facilities of a single large municipality can represent an investment 
worth billions of dollars.
    The efficiency of wastewater treatment at a wastewater treatment 
plant depends strongly on the design and performance of the collection 
system. Many collection systems in the United States are subject to 
high volumes of infiltration (including rainfall-induced infiltration) 
and inflow during wet weather conditions. High levels of infiltration 
and inflow (I/I) increase the hydraulic load on treatment plants, which 
can reduce treatment efficiency, can exceed the capacity of components 
within the treatment process, and in extreme situations make biological 
treatment facilities inoperable (e.g., wash out the biological 
organisms that treat the waste).
    In 1972, the Federal Water Pollution Control Act, also referred to 
as the Clean Water Act (CWA), dramatically increased the role of the 
Federal government in protecting water resources by establishing a 
framework for upgrading the nation's wastewater infrastructure. With 
respect to the municipal wastewater infrastructure, the 1972 Act: 
established a minimum pollution control standard based on the 
application of secondary treatment; mandated the development of more 
stringent standards where necessary to protect water quality; 
established the National Pollutant Discharge Elimination System (NPDES) 
permit program to ensure implementation of standards; and dramatically 
increased Federal funding for municipal treatment works.

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    During the 1970's and 1980's the nation's municipal wastewater 
infrastructure dramatically expanded and improved, particularly with 
respect to treatment plants. In 1968, 72 percent of the Nation's 
municipal wastewater plants were providing secondary treatment and less 
than one percent were providing greater than secondary treatment (out 
of 14,051 facilities). By 1996, 59 percent of the Nation's municipal 
wastewater plants were providing secondary treatment and 27 percent 
were providing greater than secondary treatment (out of 16,024 
facilities). During this time, the overall number of people served by 
municipal wastewater treatment facilities increased from 140.1 million 
in 1968 to 189.7 million in 1996 (a 35 percent increase).
    In the mid-1980's and 1990's EPA increased its emphasis on 
addressing wet weather conditions and discharges from municipal 
collection systems and at treatment facilities. In 1989, EPA published 
the National Combined Sewer Overflow (CSO) Control Strategy which 
provided recommendations for NPDES permits for CSOs. See 54 FR 37370 
(September 8, 1989). In 1994, EPA issued the CSO Control Policy to 
provide greater national clarity and consistency in the way NPDES 
requirements apply to flows in combined sewers and to CSO discharges. 
See 59 FR 18688 (April 19, 1994). In addition, the Agency increased 
compliance assistance and enforcement activities associated with 
sanitary sewer overflows (SSOs) during the 1990s. In 2000, EPA issued 
the Compliance and Enforcement Strategy Addressing Combined Sewer 
Overflows and Sanitary Sewer Overflows. This strategy called for each 
EPA Region to develop an enforcement response plan, including an 
inventory of SSO violations and a description of how 20% of the 
priority systems with SSO violations would be addressed each year.
    Reducing the frequency and volume of collection system overflows 
and backups of sewage into buildings, and improving the structural 
integrity of collection systems have been some of the major objectives 
of EPA's emphasis on wet weather discharges. Typically, an important 
component of strategies to reduce collection system overflows and 
backups into buildings is to increase the conveyance of wet weather 
flows to the treatment plant. The volume of wet weather flows delivered 
to treatment facilities can also be increased by measures that reduce 
exfiltration of wastewater out of a collection system. Increased wet 
weather flow volumes at treatment plants, along with increased 
attention to water quality problems caused by wet weather flows have 
lead to increased attention to the manner by which POTWs manage wet 
weather flows.
    As these issues received greater attention, regulatory agencies, 
municipal operators of POTWs, and representatives of environmental 
advocacy groups have expressed confusion over and requested 
clarification regarding the proper interpretation of certain regulatory 
provisions in the context of wet weather flow management at POTW 
treatment plants. Of particular concern are National Pollutant 
Discharge Elimination System (NPDES) permit requirements for peak wet 
weather discharges from a publicly owned treatment works (POTW) 
treatment plant when the portion of the flow that exceeds the capacity 
of the biological treatment units is routed around biological treatment 
units and blended with the flows from the biological units (or other 
advanced treatment units) prior to discharge. Such re-routing where the 
capacity of biological (or other advanced) treatment units is exceeded 
might be necessary to avoid damaging the treatment units. Questions 
have focused primarily on the situation where the final discharge of 
these blended waste streams would meet effluent limitations based upon 
the secondary treatment regulations and any more stringent limitations 
necessary to meet water quality standards.
    Today's proposed policy may affect certain actions under 
consideration by NPDES permit authorities to address comprehensive 
sewer collection system and treatment activities by POTWs. The Agency 
seeks comment on what, if any, impact today's proposed policy may have 
on Federal or State enforcement actions under the CWA or citizen suit 
actions under section 505 of the Act, including assurance of 
implementation of the various criteria identified in the proposed 
interpretation and draft guidance.
    After review of public comments, and following any appropriate 
revisions, EPA intends that ultimately such policy would provide a 
framework that (1) ensures appropriate management of wet weather flows 
at a POTW consistent with generally accepted good engineering practices 
and criteria for long-term design, (2) clarifies technology-based 
requirements (3) uses water quality-based effluent limitations to 
address residual site-specific health and environmental risks, and (4) 
provides appropriate safeguards, including comprehensive monitoring and 
protection for sensitive waters.

B. Sewage Treatment Issues Associated With Wet Weather Flows

    Although a number of sewage treatment processes are used to comply 
with Clean Water Act requirements, most municipalities typically use a 
series of unit operations and processes to treat wastewater prior to 
discharge. The typical series of unit processes includes: preliminary 
treatment or screening to remove large solids; primary clarification 
(or preliminary sedimentation) to remove floating and settleable 
solids; and biological treatment units (also referred to as secondary 
treatment units) to remove biodegradable organic pollutants and 
suspended solids. The most common type of conventional biological 
treatment unit, an activated sludge process, typically consists of 
aerator tanks (also called reactors) followed by separate settling 
basins or clarifiers. Many treatment facilities also provide 
disinfection to deactivate pathogens and achieve microbial water 
quality standards. Some facilities also provide advanced treatment 
which are designed to reduce constituents, such as nitrogen and 
phosphorus, that are not significantly removed by biological treatment 
processes, or are designed to provide greater solids and pathogen 
reductions than traditional biological treatment processes.
    During periods of wet weather, flows received by a POTW's 
collection system and treatment facility typically increase. 
Significant increases in influent flow caused by wet weather conditions 
(e.g., due to infiltration and/or inflow of water into the collection 
system) can create operational challenges for treatment facilities and 
potentially adversely affect treatment efficiency, reliability, and 
control of unit process operations with a treatment plant. Activated 
sludge systems are particularly vulnerable to high volume peak flows. 
Peak flows that approach or exceed design capacity of an activated 
sludge unit can shift the solids inventory from the aeration basin to 
the clarifier(s), and can result in excessive solids losses from the 
clarifier(s) (i.e., wash out the biological mass necessary for 
treatment). The shifting of solids from an aeration basin to a 
clarifier diminishes treatment rates until after flows have decreased 
and the solids are returned to the aeration basin. If a clarifier 
experiences excessive loss of solids, treatment efficiencies can be 
lowered for weeks or months until the biological mass in the aeration 
basins is reestablished. In addition to these

[[Page 63046]]

hydraulic concerns, wastewater associated with peak flows may have low 
concentrations of oxygen demanding pollutants, which can also decrease 
treatment efficiencies.
    Generally, biological treatment units are designed and operated to 
maintain a relatively stable population of microorganisms. See 48 FR 
52258, 52275 (November 16, 1983). This means that biological treatment 
units generally cannot be designed to accommodate wide variations in 
flow volumes and influent strength. Primary clarification units are 
less sensitive to variations in flow volumes and influent strength. In 
addition, primary clarification units can be brought into operation and 
taken out of operation to respond to changes in flow volume.
    Many POTW treatment plants have been designed with primary 
treatment capacity that is significantly greater than the biological 
treatment capacity. These treatment plants often have multiple primary 
clarification units that are operated in parallel, with one or more 
primary clarification units not operating during low flow conditions, 
and brought into service during high flow conditions. These POTWs 
typically provide screening and primary clarification of all flows 
entering the plant, and, in order to protect their biological treatment 
units, route flows in excess of full capacity of the biological 
treatment unit around the biological treatment units. In some cases, 
chemicals are added to the portion of the flow that is routed around 
the biological treatment units to enhance solids and/or pathogen 
removal. Another option is to provide other forms of enhanced physical/
chemical treatment for the portion of the flow that is routed around 
the biological units. Some POTWs discharge flows routed around 
biological treatment units directly to a surface water, while others 
blend the flows routed around the biological treatment units with flows 
that have gone through the biological treatment unit (e.g., for 
disinfection or other advanced treatment) prior to discharge.
    Other design and operational options routinely employed to enhance 
treatment of wet weather flows without damaging biological treatment 
capabilities include:
    [sbull] Increasing the size of secondary clarifiers to accommodate 
a pre-determined amount of peak wet weather flow;
    [sbull] Providing alternative feed patterns in the aeration 
basin(s);
    [sbull] Increasing the returned activated sludge capacities 
relative to those needed for steady flow;
    [sbull] Providing flow equalization (i.e. short term storage) prior 
to the biological unit either at the plant or before flows get to the 
plant; and
    [sbull] Decreasing peak flow volumes through I/I removal, sewer 
separation or rerouting flows to a different treatment plant.
    See Design of Municipal Wastewater Treatment Plants Fourth Edition, 
1998, Water Environment Federal Manual of Practice 8, ASCE Manual and 
Report of Engineering Practice No. 76, Volume 2, page 11-5; Prevention 
and Control of Sewer System Overflows Second Edition, 1999, Water 
Environment Federation Manual of Practice FD-17.
    Other facilities may employ other modifications to manage peak wet 
weather flows. For example, some facilities divert dilute wet weather 
flows around primary clarifiers to the biological treatment units in 
order to ensure adequate organic loadings in the biological units. 
Given the complexity and site-specific nature of collection systems and 
treatment facilities, site-specific planning processes are necessary to 
identify the optimal mix of peak wet weather management measures.
    Many States have developed detailed design criteria and/or 
operating practices for municipal wastewater treatment facilities. EPA 
has also developed guidance on design considerations and operation of 
POTWs, including guidance on the composite correction program approach 
to identify and address performance limitations and to obtain improved 
performance at POTWs. EPA Technology Transfer Handbook: Retrofitting 
POTWs, 1989, Hegg, B.A., L.D. DeMers, and J.B. Barber. This guidance 
identifies specific low cost modifications that can be used to optimize 
an existing facility's performance which can result in significant 
improvements of performance at many wastewater treatment facilities 
without major capital improvements. Hegg, B.A., K.L. Rakness, and J.R. 
Schultz, 1979, A Demonstration Approach for Improving Performance and 
Reliability of Biological Wastewater Treatment Plants EPA 600/2-79-035, 
NTIS No. PB-300476, USEPA, Cincinnati, OH.

C. NPDES Requirements for POTWs

    The CWA requires that most POTWs achieve effluent limitations based 
upon secondary treatment as defined by EPA and any more stringent 
limitations necessary to meet water quality standards prior to 
discharging to waters of the United States. NPDES permits are issued by 
EPA or States, U.S. Territories, or Tribes authorized by EPA to do so. 
Currently, 45 States and one U.S. Territory administer the NPDES permit 
program. EPA issues NPDES permits in the remaining States and 
Territories, and in Indian country.
1. Secondary Treatment Regulations
    Section 301(b)(1)(B) of the Clean Water Act, 33 U.S.C. 
1311(b)(1)(B), requires that publicly owned treatment works (POTWs) 
achieve effluent limitations based upon secondary treatment as defined 
by the Administrator of EPA pursuant to section 304(d)(1) of the Act. 
Section 304(d)(1) of the Act directed EPA to publish information, in 
terms of amounts of constituents and chemical, physical, and biological 
characteristics of pollutants, on the degree of effluent reduction 
attainable through the application of secondary treatment. Section 
304(d)(4) of the Act, 33 U.S.C. 1314(d)(4), deems treatment facilities 
such as oxidation ponds, lagoons, ditches and trickling filters to be 
the ``equivalent'' of secondary treatment. That section directed the 
Administrator to provide guidance on design criteria for such 
facilities, taking into account pollutant removal efficiencies. Section 
304(d)(4) further requires that water quality not be adversely affected 
by deeming such facilities to be the equivalent of secondary treatment.
    EPA promulgated the secondary treatment information regulations at 
40 CFR part 133 to define minimum levels of effluent quality for 
publicly owned treatment works (POTWs) prior to discharge. The 
secondary treatment regulations were based on performance data for a 
sample of well-designed and well-operated secondary treatment plants. 
The 30-day average effluent limitations in the secondary treatment 
regulations were based on the 95th-percentile value of data 
representing well-operated POTWs, excluding values attributable to 
upsets, bypasses, operational errors, or other unusual conditions. With 
the exception of section 304(d)(4) facilities eligible for treatment 
equivalent to secondary treatment, the secondary treatment regulations 
do not otherwise specify the type of treatment process to be used to 
meet secondary treatment requirements nor do they preclude the use of 
non-biological facilities. Rather, the basic decisions on the choice of 
a technology or alternative waste management technique were left to a 
case-by-case cost-effectiveness analysis. See 48 FR 52258, 52260 
(November 16, 1983).
    The requirements of the secondary treatment regulations are 
expressed as concentration limitations (seven-day and 30-day average 
effluent

[[Page 63047]]

concentration limitations for total suspended solids and five-day 
biochemical oxygen demand (BOD5)), percent removal 
requirements (for total suspended solids and BOD5), as well 
as a limitation on pH. The regulations require that percent removal 
requirements for total suspended solids (SS) and the five-day measure 
of biochemical oxygen demand (BOD5) be determined according 
to a 30-day average. The percent removal requirements were originally 
established to achieve two basic objectives: (1) to encourage 
municipalities to correct excessive I/I problems in their sanitary 
sewer systems, and (2) to help prevent intentional dilution of influent 
wastewater as a means of meeting permit limits. See 50 FR 23382 (June 
3, 1985).
    For most types of POTWs, the secondary treatment regulations 
establish a 30-day average percent removal requirement of 85 percent 
for SS and BOD5. Facilities eligible for equivalent 
treatment considerations under section 304(d)(4) are subject to less 
stringent percent removal requirements. The secondary treatment 
regulations provide for case-by-case adjustments to the percent removal 
requirements to address several special considerations. Under Sec.  
133.103(a), for treatment works that receive flows from combined 
sewers, the decision must be made on a case-by-case basis as to whether 
any attainable percentage removal level can be defined when the plant 
receives highly dilute influent, e.g., during wet weather flows, and, 
if so, what the level should be. For treatment works that receive flows 
from separate sewers, Sec.  133.103(d) authorizes the permit issuing 
authority to substitute a less restrictive 30-day average percent 
removal requirement or a mass loading limit for the percent removal 
requirement if the permittee demonstrates that:
    (i) The treatment facility will consistently meet its permit 
effluent concentration limitations but its percent removal requirements 
cannot be met due to less concentrated influent,
    (ii) to meet the percent removal requirements, the facility would 
have to achieve significantly more stringent limitations than would 
otherwise be required by concentration-based standards, and
    (iii) the less concentrated influent is not the result of excessive 
I/I. Excessive I/I is the quantities of I/I that can be economically 
eliminated from a sewer system as determined by a cost-effectiveness 
analysis that compares the costs for correcting the I/I conditions to 
the total costs for transportation and treatment of the I/I to a 
treatment facility.
    For these separate sanitary sewer systems, the determination of 
whether the less concentrated wastewater is the result of excessive I/I 
uses the definition of excessive I/I in 40 CFR 35.2005(b)(16) plus the 
additional criterion that inflow is deemed nonexcessive if the total 
flow to the POTW (i.e., wastewater plus inflow plus infiltration) is 
less than 275 gallons per capita per day. See 40 CFR 133.103(d). The 
275 gallons per capita per day figure is only a threshold value, and 
permittees may determine that even higher values of I/I are 
nonexcessive through a cost-effective evaluation on a case-by-case 
sewer system basis. See 50 FR 23384 (June 3, 1985) and 54 FR 4225 
(January 27, 1989). Guidance for the cost-effectiveness analysis 
associated with demonstrating that I/I is not excessive is provided in 
Sewer System Infrastructure Analysis and Rehabilitation, (EPA, 1991, 
EPA/625/6-91/030).
    EPA adopted this approach to provide flexibility to address 
facilities experiencing various degrees of less concentrated influent 
that cannot meet the 85 percent removal requirement without significant 
additional construction, and, at the same time, encourage cost 
effective I/I reduction. See 40 CFR 133.101(m) and 133.103(d)(3). The 
approach was based on the following considerations: (1) In general, I/I 
programs had not been as successful in reducing excessive I/I as 
expected; (2) many treatment systems without excessive I/I had 
relatively low concentrations of BOD5 and SS in the 
influent; (3) certain treatment technologies could not achieve 85 
percent removal under all conditions; and (4) a mandatory requirement 
of 85 percent removal for all POTWs could have caused overly stringent 
levels of treatment and use of expensive advanced treatment processes 
in some cases. See 50 FR 23382 (June 3, 1985).
2. Bypass Provision
    The NPDES regulations define standard permit conditions which are 
to be included in all NPDES permits, except that authorized NPDES 
States are not precluded from omitting or modifying a standard permit 
condition to impose a more stringent requirement. 40 CFR 122.41 and 
123.25 (note). One of those standard permit condition is the ``bypass'' 
provision at 40 CFR 122.41(m).
    The bypass provision defines bypass to mean the ``intentional 
diversion of waste streams from any portion of a treatment facility.'' 
The regulation prohibits bypasses except for where necessary for 
essential maintenance to assure efficient operation. 40 CFR 
122.41(m)(2). In such cases, the bypass cannot cause effluent 
limitations to be exceeded. For all other bypasses, the Director of the 
NPDES program may take enforcement action against a permittee for a 
bypass, unless:
    (A) Bypass was unavoidable to prevent loss of life, personal 
injury, or severe property damage;
    (B) There were no feasible alternatives to the bypass, such as the 
use of auxiliary treatment facilities, retention of untreated wastes, 
or maintenance during normal periods of equipment downtime. This 
condition is not satisfied if adequate back-up equipment should have 
been installed in the exercise of reasonable engineering judgment to 
prevent a bypass which occurred during normal periods of equipment 
downtime or preventative maintenance; and
    (C) The permittee submitted the required notices. 40 CFR 
122.41(m)(4)(i).
    In order to satisfy the ``no feasible alternatives'' criterion, 
adequate back-up equipment should be installed in the exercise of 
reasonable engineering judgment to prevent a bypass. 40 CFR 
122.41(m)(4)(i)(B). The ``no feasible alternatives'' provision of 40 
CFR 122.41(m) requires, among other things, that consideration be given 
to the feasibility of additional construction to prevent any bypasses 
that occur because of inadequate capacity. See United States v. City of 
Toledo, Ohio 63 F.Supp.2d 834 (N.D. Ohio 1999).
    The regulation at 40 CFR 122.41(m) also provides that the Director 
of the NPDES program may approve an anticipated bypass, after 
considering its adverse effects, if the Director determines that it 
will meet the three conditions listed in the bypass provision at 40 CFR 
122.41(m)(4)(i). As discussed below, EPA provided guidance on approval 
of anticipated bypasses at POTWs served by combined sewers in the 1994 
Combined Sewer Overflow (CSO) Control Policy. An approved anticipated 
bypass would be a recognition that the permitting authority had 
considered the adverse impacts of the bypass and has found that the 
bypass would or does meet the criteria of 40 CFR 122.41(m)(4)(i)(A), 
(B) and (C), and would not take enforcement action against a permittee 
for the bypass. Compliance with 40 CFR 122.41(m)(4)(i), in and of 
itself, would not shield a permittee from citizen suits for conducting 
a prohibited bypass. Southern Ohio Coal Company v. Office of Surface 
Mining, Reclamation and

[[Page 63048]]

Enforcement, 20 F.3d 1418, 1427 (6th Cir. 1994).
    The bypass regulation does not dictate that any specific treatment 
technology be employed. Instead, the regulation requires that a system 
be operated as designed and according to the conditions of the NPDES 
permit. See NRDC v. EPA, 822 F.2d 104, 123 (D.C. Cir. 1987). For 
example, seasonal effluent limitations which allow the facility to shut 
down a specific pollution control process during certain periods of the 
year are not considered to be a bypass provided the variation in 
effluent limits is accounted for and recognized in the permit which 
allows a facility to dispense with some unit processes under certain 
conditions. See 49 FR 37998, 38037 (September 26, 1984).
    As noted earlier, all NPDES permits are required to contain a 
prohibition on bypasses consistent with or more stringent than 40 CFR 
122.41(m). See 40 CFR 123.25 (note). The bypass provision at 40 CFR 
122.41(m) defines bypass to mean the intentional diversion of waste 
streams from any portion of a treatment facility. However, the term 
``treatment facility'' is not defined in the bypass regulation. Today's 
action requests public comment on: (1) A proposed interpretation of the 
bypass regulations regarding the term ``treatment facility'' as it 
relates to the treatment plant at a POTW; and (2) draft guidance on how 
NPDES authorities can characterize the ``treatment facility'' in a 
specific permit for a POTW treatment plant to account for the flow 
routing scenario. The Agency's proposed policy would be restricted to 
POTW treatment plant discharges under peak wet weather conditions where 
flows in excess of the biological or advanced treatment units are 
routed around the biological or advanced treatment units and blended 
with the wastewaters from the biological units (or other advanced 
treatment units) prior to discharge, and where the final discharge 
would meet effluent limitations based upon the secondary treatment 
regulations and any more stringent limitations necessary to meet water 
quality standards.
3. Combined Sewer Overflow Control Policy
    EPA has provided guidance on the planning, selection and 
implementation of controls to meet technology- and water quality-based 
requirements for CSOs under the NPDES program in the National CSO 
Control Strategy, 54 FR 37370 (September 8, 1989), and the CSO Control 
Policy, 59 FR 18688 (April 19, 1994). The 1994 CSO Control Policy 
provides comprehensive guidance for developing site-specific NPDES 
permit requirements for combined sewer systems to address wet weather 
CSO discharges from designed overflow points. The Wet Weather Water 
Quality Act of 2000 amended the CWA to provide that each permit, order 
or decree issued after December 15, 2000, for a discharge from a 
municipal combined sewer shall conform to the CSO Control Policy. 33 
U.S.C. 1342(q)(1).
    Under the CSO Control Policy, permittees with combined sewer 
systems were to immediately undertake a process to accurately 
characterize their sewer systems, to demonstrate implementation of nine 
minimum controls identified in the Policy, and to develop and implement 
a long-term CSO control plan that would ultimately provide for 
compliance with the requirements of the CWA. See 59 FR 18688 (April 19, 
1994). The CSO Control Policy identifies EPA's major objectives for 
long-term control plans.
    When developing the CSO Control Policy, EPA recognized that some 
POTW treatment plants may have primary treatment capacity in excess of 
their biological treatment capacity. See 59 FR 18693, column 2. The 
Policy indicates that one effective strategy to abate pollution 
resulting from CSOs is to maximize the delivery of flows during wet 
weather to the POTW treatment plant for treatment. This strategy can 
maximize the use of available POTW facilities for wet weather flows and 
ensure that combined sewer flows receive at least primary treatment 
prior to discharge. In addition, this strategy may enable the permittee 
to eliminate or minimize overflows to sensitive areas. In recognition 
of the significant water quality benefits of maximizing flow to the 
POTW treatment plant, the CSO Control Policy includes it as a minimum 
element of a long-term control plan.
    To further the objective of maximizing treatment at the POTW 
treatment plant, the CSO Control Policy provides guidance on the use of 
an NPDES permit to recognize approval of anticipated bypasses where the 
criteria of the bypass provision for such approvals are met. The CSO 
Control Policy clarifies that normally it is the responsibility of the 
permittee to document, on a case-by-case basis, compliance with 40 CFR 
122.41(m) in order to have an anticipated bypass approved in a permit. 
The Policy indicates that for some CSO-related permits, the study of 
feasible alternatives in the long-term control plan, along with other 
information in the permit record, may provide sufficient support for 
approval of a CSO-related bypass in the permit, and to define the 
specific parameters under which a bypass can be approved. The Policy 
provides that where a permit includes an approval of a CSO-related 
bypass, the permit would define the specific wet weather conditions 
under which a CSO-related bypass would be allowed and would also 
specify what treatment, monitoring, and effluent limitations would 
apply to the bypass flow.
    The Policy provides that permits with approved bypasses should also 
make it clear that all wet weather flows passing the headworks of the 
POTW treatment plant will receive at least primary clarification, 
solids and floatables removal and disposal, and disinfection where 
necessary, and any other treatment that can reasonably be provided.
    The CSO Policy further indicates that the ``no feasible 
alternatives'' requirement of the bypass regulation can be met if the 
record shows 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 at 
the existing facilities for greater amounts of wet weather flow. See 59 
FR 18694, column 3. The feasible alternative analysis should include, 
for example, consideration of enhanced primary treatment--e.g., 
chemical addition and non-biological secondary treatment. Id. Other 
bases supporting a finding of ``no feasible alternatives'' may also be 
available on a case-by-case basis. As part of its consideration of 
possible adverse effects resulting from the bypass, the permitting 
authority should also ensure that the bypass will not cause exceedances 
of water quality standards. Id.

D. Water Quality Criteria for Bacteria

    In 1986, EPA published Ambient Water Quality Criteria for 
Bacteria--1986, which contained EPA's recommended water quality 
criteria for bacteria for protection of bathers from gastrointestinal 
illness in recreational waters. The water quality criteria established 
levels of indicator bacteria, namely Escherichia coli (E. coli) and 
enterococci, that demonstrate the presence of fecal pollution and which 
should not be exceeded in order to protect bathers in fresh and marine 
recreational waters. Prior to its 1986 recommendations, EPA recommended 
specific levels of fecal coliforms to be

[[Page 63049]]

used as the indicator organism to protect bathers from gastrointestinal 
illness in recreational waters.
    The data supporting the 1986 bacteria water quality criteria were 
obtained from a series of epidemiological studies that examined the 
relationship between swimming-associated illness (namely, acute 
gastrointestinal illness) and the microbiological quality of the waters 
used by recreational bathers. The epidemiological studies demonstrated 
that fecal coliforms, the indicator originally recommended in 1968 by 
the Federal Water Pollution Control Administration of the Department of 
Interior, are correlated less strongly with swimming-associated 
gastroenteritis than other possible indicator organisms. Two indicator 
organisms, E. coli and enterococci, exhibited a strong correlation to 
swimming-associated gastroenteritis, the former in fresh water only and 
the latter in both fresh and marine waters. The strong correlation is 
due to the indicator organisms being more similar to many of the 
pathogens of concern in their ability to survive treatment and in the 
environment. Enterococci are also resistant to saline environments, 
enhancing their utility as an indicator in marine waters. In addition, 
E.coli and enterococci are less frequently found than fecal coliforms 
in environmental settings where fecal contamination is known to be 
absent.
    The Beaches Environmental Assessment and Coastal Health (BEACH) Act 
was enacted on October 10, 2000. Public Law 106-284, 114 Stat. 870 
(2000). The BEACH Act addresses pathogens and pathogen indicators in 
coastal recreation waters. Among other things, the BEACH Act added 
section 303(i) to the Clean Water Act to require States and Tribes with 
coastal (and Great Lake) recreation waters to adopt new or revised 
water quality standards by April 10, 2004, for pathogens and pathogen 
indicators for which EPA has published criteria under section 304(a). 
The BEACH Act also directs EPA to promulgate standards for States and 
Tribes that fail to adopt standards for pathogens and pathogen 
indicators for coastal recreation waters that are as protective of 
human health as those published by EPA.

III. Proposed Policy

    EPA has received requests from many stakeholders to clarify the 
NPDES requirements for discharges from POTWs where peak wet weather 
flow is routed around biological treatment units and then blended with 
the effluent from the biological units prior to discharge where the 
final discharge meets permit effluent limitations based on the 
secondary treatment regulation (40 CFR part 133) or any more stringent 
limitations necessary to attain water quality standards. Today's 
proposed policy has two components, (1) a proposed interpretation of 
the bypass provision (40 CFR 122.41(m)) as it applies to alternative 
wet weather treatment scenarios at POTW treatment plants that involve 
blending; and (2) draft guidance on how such an interpretation should 
be implemented. EPA requests comments on both the proposed 
interpretation and the draft guidance.
    Peak wet weather discharges from POTWs that consist of effluent 
routed around biological or other advanced treatment units blended 
together with the effluent from the biological units (or from other 
advanced treatment units) prior to discharge would not be a prohibited 
bypass and could be authorized in an NPDES permit if all of the 
following principles were followed:
    1. The final discharge meets effluent limitations based on the 
secondary treatment regulation (40 CFR part 133), including applicable 
30-day average percent removal requirements, or any more stringent 
limitations necessary to attain water quality standards. For treatment 
works served by sanitary sewers, the Director of the NPDES permit 
program may substitute lower 30-day average percent removal 
requirements or a mass loading limit for the percent removal 
requirement only if the permittee demonstrates the criteria in Sec.  
133.103(d) are met, including that the less concentrated influent is 
not the result of excessive I/I. For treatment works served by combined 
sewers, Sec.  133.103(a) provides that the decision must be made on a 
case-by-case basis as to whether any attainable percentage removal 
level can be defined during wet weather flows, and, if so, what the 
level should be.
    2. The NPDES permit application for the POTW provides notice of, 
and specifically recognizes, the treatment scenario that would be used 
for peak flow management. The treatment scenario, including designed 
capacity of various units, should be consistent with generally accepted 
practices and long-term design criteria, and designed to ensure that 
discharges meet effluent limitations based on the secondary treatment 
regulation and any more stringent limitations necessary to meet water 
quality standards (including limitations necessary to meet applicable 
total maximum daily loadings). The application of the generally 
accepted practices and long-term design criterion typically would 
include an evaluation of changes to the base and peak design flows at 
the treatment plant from the time the peak flow treatment scenario was 
last recognized by the NPDES authority, and, if circumstances have 
materially and substantially changed, an evaluation of the cost-
effectiveness of a reasonable range of alternatives, which may entail 
construction of facilities to provide additional wet weather 
capabilities, such as equalization and/or storage facilities, or high-
efficiency physical/chemical treatment for diverted flows. The 
application of the generally accepted practices and long-term design 
criterion should be reevaluated as circumstances change materially and 
substantially, and at permit reissuance. Any permit issued after EPA 
evaluates public comments received and takes further action on today's 
proposed policy should specifically recognize or incorporate by 
reference the treatment scenario that would be used for peak flow 
management. EPA notes that requiring documentation of the treatment 
scenario in the permit would ensure that EPA would have an opportunity 
to review the documentation during its review of permits issued by an 
authorized NPDES State. In addition, the public would have an 
opportunity to review and comment on the specific conditions under 
which blending would be authorized prior to final approval and issuance 
of the permit.
    3. The treatment scenario that would be used for peak flow 
management should provide, prior to blending, at least the equivalent 
of primary clarification for the portion of flow routed around 
biological or other advanced treatment units.
    4. The peak flow treatment scenario chosen by the permittee for use 
when flows exceed the capacity of storage/equalization units, 
biological treatment units or advanced treatment units should be 
operated as it is designed to be operated and in accordance with the 
treatment scenario reflected in the permit record and conditions set 
forth in the permit. A portion of the flow should only be routed around 
a biological or advanced treatment unit when the capacity of the 
treatment unit is being fully utilized. Additionally, for permits 
issued after EPA evaluates public comments received and takes further 
action on today's proposed policy, such a peak flow treatment scenario 
should only be used when flows exceed the capacity of storage/
equalization units based on generally accepted good engineering 
practices and long-term design criteria aimed at protecting the 
structural integrity and function of the treatment units and

[[Page 63050]]

under the specific circumstances recognized in the permit.
    5. The permit must require monitoring, including type, interval and 
frequency sufficient to yield data which are representative of the 
final blended discharge to ensure compliance with applicable water 
quality-based effluent limitations. See 40 CFR 122.48(b). The permit 
should require reporting of the date and volume of blended discharges 
along with appropriate pollutant parameter concentrations. In addition, 
the permit should ensure that permittees develop additional information 
to support the development of water quality-based effluent limitations 
in subsequent permits, including information to: (a) Assess potential 
water quality impacts associated with blended effluent; (b) evaluate 
the effectiveness of the treatment of key parameters, such as 
pathogens, resulting from alternative flow routing scenarios; and (c) 
characterize ambient levels of such pollutant parameters.
    6. The permit must require, at a minimum, that the permittee 
properly operate and maintain all parts of the collection system over 
which the permittee has operational control in a manner consistent with 
40 CFR 122.41(e). For POTWs served by combined sewers, any permit 
issued after December 15, 2000, shall conform to the provisions of the 
1994 CSO Control Policy, including the development and implementation 
of a long-term control plan (LTCP), and appropriate requirements for 
the collection system. As applied to POTWs serving separate sanitary 
sewers, EPA would interpret ``proper operation and maintenance'' to 
include appropriate removal of infiltration and inflow from parts of 
the collection system over which the permittee has operational control 
as well as measures to evaluate the structural integrity of the system. 
Such a demonstration may be made with a program self-evaluation report, 
appropriate to the size of the system, which includes an identification 
of program deficiencies and steps to respond to them.
    In situations where one or more of the above principles would not 
be met, EPA would continue to interpret the ``intentional diversion of 
waste streams from any portion of a treatment facility'' at a POTW 
treatment plant to be a bypass subject to the restrictions of the 
bypass provision as reflected in the permit. The proposed policy upon 
which EPA invites comment today is not intended to modify the provision 
for approval of anticipated bypasses at 40 CFR 122.41(m)(4)(ii). See 59 
FR 18693, column 3.
    The principles described above for characterizing the ``treatment 
facility'' at a POTW plant (as it relates to the bypass provision) are 
not intended to address or apply to NPDES permit requirements for 
treatment of flows at a POTW during dry weather conditions or to 
discharges from facilities other than POTW plants, including industrial 
facilities where storm water is treated with non-storm water 
wastewater. The matters addressed in today's action focus on situations 
with elevated I/I levels in municipal collection system resulting from 
wet weather conditions. EPA has not evaluated and does not propose to 
interpret its regulations to apply to other circumstances.
    EPA requests comment on the use of the six principles listed above 
to define the conditions under which the blending of effluent routed 
around the biological treatment unit with effluent from the biological 
treatment unit, prior to discharge would not be a prohibited bypass and 
could be authorized in an NPDES permit. EPA specifically requests 
comment on the following issues:
    (1) Is the current interpretation of ``excessive I/I'' under 40 CFR 
133.103(d) adequate? What challenges, if any, would facilities face in 
meeting the percent removal requirements or obtaining an adjustment to 
percent removal requirements under Sec.  133.103(d), including the 
excessive I/I provisions, as a pre-condition for authorization of 
blending in an NPDES permit?
    (2) In principle 4, which would require that flow only be routed 
around the biological or advanced treatment unit when the capacity of 
treatment and storage units is being fully utilized, should EPA define 
the term ``fully utilized'? Are there situations where system operators 
might need to keep some treatment or storage capacity in reserve, for 
example, to help prevent overflows or address other peak flow concerns 
where exceedences of treatment capacity is likely but has not yet 
occurred? If so, the commenter should describe the situations.
    (3) Principle 5 of this draft policy is designed to ensure 
compliance with applicable water quality-based effluent limitations, 
including those based on water quality criteria for bacteria. Would 
this principle be sufficient to protect against discharges of 
pathogenic organisms or should principle 5 of this draft policy include 
an explicit requirement for disinfection of blended effluent prior to 
discharge, where appropriate?
    (4) In developing principle 6, what factors should be considered 
when evaluating if a permittee is properly operating and maintaining 
their collection system in a manner consistent with 40 CFR 122.41(e)?
    Additional considerations for permit writers addressing POTW plants 
that use peak flow treatment scenarios that consist of effluent routed 
around biological or other advanced treatment units blended together 
with the effluent from the biological units prior to discharge should 
include:
    A. To the extent practicable, NPDES permit requirements for 
discharges of peak wet weather flows at the POTW should be developed in 
a manner that encourages the permittee to consider the relationship 
between the performance of the collection system and the performance of 
treatment plants serving the system.
    B. Any POTW receiving wastes from an industrial user to which a 
categorical pretreatment standard applies may, at its discretion and 
subject to the conditions of 40 CFR 403.7, grant removal credits to 
reflect removal by the POTW of pollutants specified in the categorical 
pretreatment standard. The POTW may grant a removal credit equal to or, 
at its discretion, less than its consistent removal rate. The permit 
writer should ensure that the POTW's determination of the consistent 
removal rate adequately reflects the frequency of use of and treatment 
effectiveness of the peak flow treatment scenarios in a manner that is 
consistent with 40 CFR 403.7(b). In a similar manner, the permit writer 
should ensure that the POTW adequately reflects the frequency of use of 
and treatment effectiveness of the peak flow treatment scenarios in 
developing local limits for industrial users.

C. NPDES Permit Conditions That Are Clear and Enforceable.

    Under the interpretation proposed today, NPDES authorities would be 
able to characterize the term ``treatment facility'' in a specific 
permit for a POTW treatment plant to account for peak flow treatment 
scenarios that are consistent with generally accepted good engineering 
practices and criteria for long-term design in a manner consistent with 
the principles previously identified. Where all of the identified 
principles are followed, flows through a treatment system that is 
operated as designed and according to the permit would not be 
considered a bypass, and the permittee would not be required to make 
each of the demonstrations otherwise required under the bypass 
provision at 40 CFR 122.41(m)(4)(i),

[[Page 63051]]

including a demonstration that there were no feasible alternatives to 
the bypass.
    Where a POTW treatment facility has multiple primary clarification 
units operating in parallel to provide excess primary treatment 
capacity for high flow conditions, removing one or more primary 
clarification units from operation during low flo conditions would not 
be considered a bypass provided the capacity of the primary 
clarification units remaining in operation is not exceeded. Similarly, 
where chemical addition is used to enhance wet weather treatment 
performance (i.e., to enhance solids removal or disinfection), 
discontinuing chemical addition during low flow conditions would not be 
considered a bypass if the permit does not call for such chemical 
addition during low flow conditions.
    The NPDES regulations require that NPDES permits must include water 
quality-based effluent limitations to control all pollutants or 
pollutant parameters which the Director of the NPDES program determines 
are or may be discharged at a level which will cause, have the 
reasonable potential to cause, or contribute to non-attainment of any 
water quality standard (see 40 CFR 122.44(d)). The potential impact of 
either blended peak wet weather flows discharged from POTWs or peak wet 
weather flows that receive biological treatment may raise a number of 
site-specific water quality issues depending on the performance of 
treatment technologies under peak flow conditions, the volume of 
discharges, receiving water conditions, the uses of receiving waters 
and other factors. Ensuring appropriate characterization of potential 
human health and environmental risks associated with peak flows with 
enhanced effluent and ambient monitoring data describing peak flow 
conditions is important for discharges to receiving waters with 
designated uses for primary contact recreation and/or drinking water. 
Additional information may be needed to determine if POTW discharges 
that occur under peak wet weather flow conditions would cause, have a 
reasonable potential to cause, or contribute to non-attainment of a 
water quality standard. Modeling of the collection system, treatment 
facility and receiving water may be necessary to characterize the 
impact of peak wet weather flows on receiving water quality and to 
predict the improvements that would result from different treatment 
scenarios.
    The NPDES regulations authorize permitting authorities to modify 
permits for cause. See 40 CFR 122.62 and 124.5. In addition, permits 
often contain a reopener clause. Examples include general reopener 
clauses that mirror the causes for modification in the NPDES 
regulations. Permits also often contain specific reopener clauses for 
the purpose of modifying conditions based on results of specific 
pollutant monitoring required in the permit, such as for toxic 
pollutants. EPA requests comment on whether permits that authorize 
blending should contain a specific reopener clause. Such a reopener 
clause could address situations where additional controls are necessary 
to assure attainment of water quality standards or where new monitoring 
information justifies the application of different permit conditions.
    One of EPA's highest priorities in developing control strategies 
for wet weather discharges is ensuring adequate control of such 
discharges to sensitive receiving waters. Sensitive receiving waters, 
as determined by the NPDES authority in coordination with State and 
Federal agencies, as appropriate, include: Designated Outstanding 
National Resource Waters; National Marine Sanctuaries; waters with 
threatened or endangered species (and associated habitat;) waters with 
primary contact recreation (e.g., beaches and other points of public 
access); public drinking water intakes or their designated protection 
areas; and shellfish beds. See the 1994 CSO Control Policy (59 FR 
18688, April 19, 1994). Wherever physically possible and economically 
achievable, discharges of blended effluent to a sensitive area should 
not be authorized, except where prohibiting the discharge of blended 
effluent would provide less environmental protection than additional 
treatment. Where elimination of the discharge of blended effluent to a 
sensitive receiving water is not physically possible and economically 
achievable, the permitting authorities must ensure an adequate 
demonstration that the discharge will not cause or have reasonable 
potential to cause or contribute to non-attainment of applicable water 
quality standards. For such discharges, each subsequent permit term 
should require a reassessment based on new or improved techniques, or 
on changing circumstances that influence economic achievability.
    EPA strongly encourages States that have not already done so to 
adopt the recommendations set forth in Ambient Water Quality Criteria 
for Bacteria--1986 or other protective water quality criteria for 
bacteria based on scientifically defensible methods as their water 
quality standards to replace water quality standards based on total or 
fecal coliforms.
    Today's proposed policy would provide guidance to EPA Regional and 
State permitting authorities as well as to municipal permittees and the 
general public on how EPA intends to exercise its discretion in 
implementing the statutory and regulatory provisions related to 
discharges from POTWs where peak wet weather flow is routed around 
biological treatment units and then blended with the effluent from the 
biological units prior to discharge and where the final discharge meets 
permit effluent limitations based on the secondary treatment regulation 
(40 CFR part 133) or any more stringent limitations necessary to attain 
water quality standards. The guidance is designed to implement national 
policy on these issues.
    The statutory provisions and EPA regulations described in this 
document contain legally binding requirements. Today's document would 
not substitute for those provisions or regulations, nor is it intended 
to be a regulation itself. In fact, today's action invites public 
comment on a proposed interpretation of EPA regulations in a specific 
context and invites comment on guidance to implement such a proposed 
interpretation. Thus, this document would not impose legally binding 
requirements on EPA, States, or the regulated community, and may not 
apply to a particular situation based upon the circumstances. EPA and 
State decisionmakers would retain the discretion to adopt approaches on 
a case-by-case basis that differ from this proposed policy where 
appropriate. Any decisions regarding a particular facility should be 
made based on the statute and regulations. Therefore, interested 
parties are free to raise questions and objections about the substance 
of this proposed policy and the appropriateness of the application of 
this proposed policy to a particular situation. EPA intends to and 
States should, consider whether or not the recommendations or 
interpretations in the proposed policy are appropriate in that 
situation. EPA may revise today's proposed policy after consideration 
of public comment, or at some other time in the future. EPA welcomes 
public comments on this document and will consider those comments in 
any future revision of today's proposed policy.
    EPA's intention is to reduce confusion regarding appropriate 
consideration of blending at POTWs. Because of significant interest 
from various stakeholders, the Agency is inviting public comment on the 
proposed policy, including the proposed interpretation of

[[Page 63052]]

EPA regulations. To date, EPA has not established a national policy 
(either through rulemaking or through non-binding guidance to assist in 
the interpretation of the bypass regulation) regarding whether and 
under what circumstances wet weather blending at a POTW plant would not 
constitute a bypass. Prior to today's action, permitting agencies have 
interpreted and applied the bypass regulation on a case-by-case basis 
according to the facts and circumstances presented by a particular 
POTW. Therefore, by today's action, EPA also invites comment on whether 
or not it should conduct rulemaking to implement the proposed policy, 
specifically, whether the Agency should revise the text of the 
regulations specifically to address the matters discussed in today's 
proposal.

    Dated: November 3, 2003.
G. Tracy Mehan, III,
Assistant Administrator, Office of Water.
[FR Doc. 03-28103 Filed 11-6-03; 8:45 am]
BILLING CODE 6560-50-P