EPAs Proposed Policy on Wastewater Blending: Background and Issues

CRS Report for Congress
EPA’s Proposed Policy on Wastewater Blending:
Background and Issues
Updated May 24, 2005
Claudia Copeland
Specialist in Resources and Environmental Policy
Resources, Science, and Industry Division

Congressional Research Service ˜ The Library of Congress

EPA’s Proposed Policy on Wastewater Blending:
Background and Issues
In November 2003 the Environmental Protection Agency (EPA) proposed a
policy concerning a wastewater treatment practice called blending. The policy was
intended to clarify when the practice can be allowed and still adhere to Clean Water
Act regulations and requirements. Some cities use blending to manage peak flows
of water and waste into wastewater treatment plants during and after storms as a way
to prevent conditions that otherwise result in raw sewage backups into homes and
other buildings or overflows into nearby waters. Blending involves routing excess
wastewater around the plant’s biological treatment processes and recombining this
excess flow with fully treated wastewater before discharging it to a stream or lake.
Although blending has been standard engineering practice for several decades
as a way to manage peak stormwater flows, controversy exists about the practice,
both among stakeholder groups and also internally at EPA, where enforcement
officials have challenged the practice and in some cases opposed allowing cities to
use it. Others at EPA believe that, with certain restrictions, the practice is legal and
environmentally protective. Controversies and uncertainties led EPA to announce
on May 19, 2005, that it will not finalize the policy that it proposed in 2003.
This report provides background on blending, why and how it is practiced, the
proposed policy that EPA now says it will not finalize, associated issues, and
congressional interest in the topic. It will be updated as warranted.
Criticism of blending focuses on three concerns: legality of the practice, impacts
on public health and the environment, and other policy issues. A number of groups
and interests weighed in on all of these issues, especially in comments on the
November 2003 proposed policy. Environmental advocates say that the practice of
blending is inconsistent with existing rules that prohibit intentional bypass of a
treatment facility. These groups have also raised substantial concern about public
health and environmental impacts from discharges of wastes that contain pathogenic
organisms. Many cities and municipal organizations supported the EPA policy and
practice of blending, saying that if cities are barred from blending, they are forced to
make costly infrastructure investments, with limited benefit. While a number of
states supported the EPA policy, others opposed it for reasons including concern that
the policy would undermine incentives for cities to remedy the infrastructure
problems that result in sewage overflows.
In Congress, these issues have drawn some attention. In January 2004,
Members with differing views wrote to EPA to express concerns about the proposed
policy. A House subcommittee held a hearing on the topic in April 2005.
Legislation intended to bar EPA from issuing blending rules or guidance has been
introduced in the 109th Congress (H.R. 1126). Also, in acting on FY2006
appropriations for EPA (H.R. 2361), the House adopted an amendment prohibiting
EPA from using funds to finalize or implement the 2003 proposed blending policy.

In troduction ......................................................1
Background ......................................................2
Wastewater Treatment Processes..................................2
Federal Law and Regulations.....................................3
Wet Weather Pollution Problems.................................4
Administrative Actions: CSO and SSO Policies......................5
What Is Blending?.............................................6
EPA’s Blending Policy.........................................8
Issues with Respect to Blending......................................9
Legality ....................................................10
Public Health and Environmental Impacts..........................11
Water Quality Criteria for Bacteria...........................13
Other Policy Concerns.........................................14
Congressional Interest and Status of the Proposal........................15
List of Figures
Figure 1. Blending at a Sewage Treatment Facility During a Storm..........7

EPA’s Proposed Policy on Wastewater
Blending: Background and Issues
In November 2003, the Environmental Protection Agency (EPA) issued a
proposed policy concerning a wastewater treatment practice called blending. It is a
type of operational practice that is used to prevent conditions that result in sewage
backups into homes and other buildings, or overflows of untreated waste into nearby
waters. The proposal was intended to clarify when the practice can be allowed and
still adhere to Clean Water Act regulations and requirements. Blending has been
used for several decades to manage peak flows of water and waste into wastewater
treatment plants during storms, but it recently has become controversial. The
practice involves routing excess wastewater from domestic, commercial and
industrial sources around the plant’s biological treatment processes and recombining
this excess flow with fully treated wastewater before discharging it to a stream or
lake (see Figure 1, on page 7). On May 19, 2005, after reviewing nearly 100,000
public comments on the proposal — many favoring it, but many others opposing it
— EPA announced that it would not finalize the 2003 proposal and will continue to
work on alternatives.
This report provides background on blending, why and how it is practiced,
EPA’s proposed policy, associated issues, and congressional interest in the topic.
Controversy exists about whether the practice is lawful under water quality
regulations, whether it is harmful to human health or the environment, and whether
it is good from a policy perspective. Supporters of the proposed policy, including
many cities, municipal organizations and some states, say that if blending is restricted
or prohibited, cities will be forced to spend limited public resources on costly water
infrastructure improvements that are used infrequently. Such critics as environmental
advocates and other states say that blending allows treatment plants to discharge
wastewater that could contain harmful pathogenic microorganisms. Many critics also
said that EPA’s proposed policy would have allowed treatment plants to blend even
when other more environmentally protective technological options are available. A
key issue was whether the policy would have clarified EPA regulations to allow the
safe use of blending by cities, as EPA intended, or would have fostered wider use of
wastewater management practices that critics believe will harm public health and the
The particular issues concerning blending also arise in the broader context of
policymakers’ efforts to control pollution associated with wet weather discharges that
happen only during and after major precipitation events. EPA believes that these
sources, including combined sewer overflow discharges, stormwater, separate
sanitary sewer overflows, and nonpoint source runoff, are the leading cause of water

quality impairment in the United States.1 The nation’s initial efforts to control water
pollution focused on conventional point sources from municipal, commercial, and
industrial wastewater treatment plants that are typically characterized by predictable
flows and identifiable discharge points. Since the mid-1980s, policymakers have
turned attention to other, non-traditional wet weather pollution sources that are more
difficult to control because the sources are numerous and geographically dispersed,
and waste flows are intermittent and largely unpredictable. Managing these diverse
sources presents major policy and technological challenges.
Wastewater Treatment Processes
In the United States, wastewater is discharged from sources such as homes or
industrial plants and is transported via collection systems consisting of sewers and
pumping facilities to a wastewater treatment facility. The wastewater components
of major concern are organic and inorganic materials that will deplete the oxygen
resources of the stream or lake to which they are discharged, those which may
stimulate undesirable growth of plants or organics (such as algae) in the receiving
water, or those with potential undesirable aesthetic effects or adverse health effects
on downstream water uses. Another important wastewater treatment concern is
removal of pathogenic bacteria and viruses that can cause disease.
Treatment plants generally work in two stages. Primary treatment mechanically
separates the coarser solids from the water, generally by screening and settling,
typically removing about 60% of solids and 35% of BOD from the untreated waste.2
The core element of wastewater treatment, called secondary treatment, follows
primary treatment; it typically involves biological processes. The biologic process
most often used today is the activated sludge process, which utilizes microorganisms
in an aerobic environment to remove a majority of the primary pollutants found in
wastewater. The microorganisms (bacteria and protozoa) use the remaining nutrients
and organic material in the wastewater as their food supply. Although secondary
treatment may remove more than 85% of the remaining BOD and suspended solids,
it fails to remove significant amounts of nitrogen, phosphorus, or heavy metals, nor
does it completely remove pathogenic bacteria and viruses. If further treatment such
as nutrient removal is required to meet water quality standards, tertiary biologic or
chemical treatment processes can be used. Following secondary or tertiary treatment,

1 U.S. Environmental Protection Agency. National Water Quality Inventory, 2000 Report.
EPA-841-R-02-001. August 2002. P. ES-3.
2 BOD, or biochemical oxygen demand, is a measure of the oxygen-consuming organic
matter and ammonia-nitrogen in wastewater and is used to determine how well a treatment
plant is working. The higher the BOD loading, the greater the resulting depletion of oxygen
in the waterway. The ability of a body of water to support life depends mainly on
maintaining a certain amount of dissolved oxygen (DO) because, for example, DO is what
fish breathe. Thus, federal regulations (and facility-specific permits that implement those
rules) specify maximum amounts of BOD that wastewater treatment plants may discharge,
as measured by the oxygen consumed in a stated period of time, usually five days (BOD5).

the final effluent generally is disinfected before it is released to a receiving water,
most commonly by chlorination, ultraviolet irradiation, or ozonation.
Federal Law and Regulations
The 1972 Federal Water Pollution Control Act Amendments (P.L. 92-500,
commonly referred to as the Clean Water Act, or CWA) established a framework for
upgrading the nation’s wastewater infrastructure as one key element in the act’s
wide-ranging objective to restore the quality of the nation’s waters. The CWA
established a minimum pollution control standard for municipal wastewater
infrastructure, applicable nationwide, based on the application of secondary
treatment. It mandated application of more stringent treatment standards and
pollution control technology where necessary to protect local water quality and
established a permit program to ensure implementation of standards.
These requirements are implemented through regulations promulgated by the
EPA that define minimum levels of effluent quality for publicly owned treatment
works (POTWs) prior to discharge. The requirements of the secondary treatment
regulations are expressed as concentration limitations (seven-day and 30-day average
effluent concentration limits for total suspended solids (SS) and BOD5), percentage
removal requirements for both SS and BOD5, as well as a limitation on pH. For most
types of POTWs, the federal regulations establish a 30-day average percentage
removal requirement of 85% for SS and BOD5. The percent removal requirements
were established to achieve two basic objectives, according to EPA: (1) to encourage
cities to correct excessive infiltration and inflow I/I problems in their sanitary sewer
systems,3 and (2) to help prevent intentional dilution of influent wastewater as a
means of meeting permit limits.4
EPA regulations also define standard permit conditions to be included in all
Clean Water Act discharge permits. One of those standard conditions addresses
“bypasses,” which are defined as “the intentional diversion of waste streams from any
portion of a treatment facility” (40 CFR §122.41(m)). Under these rules, a bypass
is prohibited unless: it is unavoidable to prevent loss of life, injury, or severe
property damage; there are no feasible alternatives, such as use of auxiliary treatment
or backup facilities or retention of untreated wastes; and proper notice is provided to
the appropriate permitting authority. The bypass cannot cause effluent limitations to
be exceeded.

3 Infiltration occurs from too much rainfall or snowmelt percolating through the ground into
leaky sewers which are not intended to collect rainfall or to drain property. Infiltration can
also occur as a result of groundwater seeping directly into leaky sewers. Excess water can
also inflow through roof drains connected to sewers and broken or badly connected sewer
service lines.
4 68 Federal Register 216, Nov. 7, 2003, p. 63047.

Wet Weather Pollution Problems
The collection system that conveys wastewater to the treatment plant is a key
element of the overall wastewater infrastructure system. Collection systems are
either combined sewer systems, which are designed to carry domestic and industrial
sanitary waste plus rainwater; or separate sanitary sewer systems, designed to collect
only domestic and industrial sanitary waste.5 Treatment plants and collection
systems are designed to handle the flows up to certain volumes under routine or
predictable operating conditions. A more difficult challenge is that of managing
flows that occur under peak flow conditions, during what is referred to as “wet
weather” events (rainfall, as well as snowmelt).
Extreme wet weather events can introduce larger volumes of water and waste
than the plant and collection system can adequately manage, resulting in collection
system overflows and backups of sewage into buildings, and water quality problems
from discharges of inadequately treated waste. During storm events, both combined
and separate sewer systems can experience overflows when the capacity of a sewer
is exceeded as a result of blockages, bottlenecks and/or undersized pipes. The
discharge of untreated or partially treated sewage contains pathogenic organisms that
represent a health risk and also may contain toxic and/or oxygen-demanding
pollutants. Infiltration/inflow of rainwater into sewers is believed to be the primary
factor causing peak flows in sewers, especially separate sanitary sewers. Aging
infrastructure and associated maintenance challenges can also lead to excess water
in sanitary sewer systems. High levels of I/I that reach the treatment plant increase
the hydraulic load on the plant, which can reduce treatment efficiency, exceed the
capacity of components within the plant, and in extreme situations make biological
treatment facilities inoperable. Treatment plant operators use a combination of
strategies to manage these peak flows, including implementing operation and
maintenance programs, enlarging pipes, adding or increasing storage capacity,
building additional treatment facilities, or using alternative treatment techniques to
move peak flows through the treatment.
Operators of treatment plants and collection systems have long faced these
challenges, and for the last 15 years or so, policymakers have been addressing various
wet weather pollution issues, including developing strategies to reduce overflows and
backups, as well as establishing appropriate regulatory and enforcement policies.
By definition, sewer overflows are unauthorized discharge points that violate the
Clean Water Act’s prohibition on discharges that are not in compliance with the
limitations and conditions of a discharge permit issued pursuant to the CWA.
Nevertheless, municipal officials and sanitary engineers say that it is practically
impossible to design a system that will never overflow. Even under the best of
conditions, engineers say, natural disasters and even pipe failures will lead to

5 Combined sewer systems are remnants of the nation’s early infrastructure and are found
in about 900 communities, primarily in older cities in the Northeast, Great Lakes region, and
the Pacific Northwest. Most combined sewer systems were constructed before 1900 when
the necessity for separate wastewater treatment was not readily apparent.

unavoidable releases of sewage. However, chronic overflows result from inadequate
system maintenance and deterioration, not unavoidable circumstances.
Recognizing the view that sewer overflows are unavoidable, at least to a degree,
some permitting authorities have issued Clean Water Act permits to POTWs
allowing overflow discharges — despite the statutory prohibition on discharges that
do not meet secondary treatment requirements. For example, some permits authorize
overflows when they are not feasible to avoid, such as circumstances beyond the
control of the system operator. In rare cases, other permits may allow discharges at
specified locations, when specific permit requirements are met, such as meeting
effluent limitations, monitoring, and reporting. However, in other cases, state and
federal enforcement officials have held to the view that overflow discharges are
inconsistent with the Clean Water Act and have brought actions against
municipalities for overflows from combined and separate sewers, thus raising
questions about the clarity of EPA regulations and consistency of enforcement.
Administrative Actions: CSO and SSO Policies
In part because of perceptions of inconsistent policy and rules, in 1994, after
lengthy consultations with stakeholder groups, EPA issued a national strategy on
controlling overflows from combined sewers (CSOs). Designed to reduce CSO
discharges that often contain high levels of organic and toxic wastes, it outlined
conditions under which combined sewer systems that overflow as a result of wet
weather events may be authorized through permits or other enforceable mechanisms,
including a requirement that systems adopt nine minimum controls and long-term
control plans.
Soon after issuance of the CSO policy, EPA and a group of stakeholders
initiated discussions for development of similar national policy on controlling
overflows from separate sanitary sewers (SSOs). The discussions about an SSO
policy were based on certain principles: desire to clarify a general prohibition on
overflows; to establish stringent but feasible standards and require specific actions
that would help eliminate avoidable overflows; and to define circumstances for
enforcement against unavoidable overflows.6 EPA officials and stakeholders were
unable to reach consensus on SSO policy issues, and eventually EPA decided to
move ahead with regulations to control SSO discharges. The Clinton Administration
approved an SSO rule proposal late in 2000. The proposal was not published in the
Federal Register before Inauguration Day in January 2001, and the incoming Bush
Administration suspended it for review. However, it was widely circulated and was
available to the public for some time on EPA’s website.

6 Combined sewer systems are, in fact, designed to discharge excess wastewater directly into
surface waters, when the capacity of the sewer system is exceeded during heavy rainfall or
snowmelt. In regulating CSOs, the key concern is first to eliminate overflows during dry
weather conditions and then to minimize impacts of storm-related discharges. The issues
involving SSOs are somewhat different, because separate sanitary sewers are not designed
to overflow. When storm sewer overflows occur, they usually are from undesigned outfall
points. Prohibiting and eliminating all overflows to the extent feasible is key.

After several months of review, in November 2001 EPA officials announced the
intention to propose the SSO rule developed by the Clinton Administration, but with
revised preamble language. During the review EPA considered a number of options,
including separate publication of noncontroversial parts of the Clinton proposal.
Chief among the controversies raised was whether EPA would open discussion of
alternatives to prohibiting SSOs or would retain the policy detailed in the Clinton
rule calling for strict enforcement against any overflows, regardless of fault. It
appears that these and other controversies persist, because as of May 2005, EPA has
not proposed or published an SSO control regulation.
During the SSO rule review, EPA staff also began working on draft guidance
on other wet weather peak flow management issues that was envisioned as separate
from but related to the SSO rule. In December 2001, EPA circulated among
stakeholders a draft guidance document addressing permit requirements and
enforcement procedures applicable under existing rules to three specific wet weather
situations. One of the three addressed the use of alternative peak flow treatment
schemes at the POTW (in contrast, for example, to procedures governing discharges
from emergency overflow structures located outside the boundary of a treatment
plant) — a practice generally referred to as “blending.” The December 2001 draft
was never formally proposed or finalized (although it was circulated to states, EPA
regional offices, and multiple other stakeholders). It evolved into a single proposal
published by EPA in November 2003 that focused only on blending.7
What Is Blending?
Blending is a wastewater flow operational technique used by some treatment
plants during and after storm events. In order to manage high flows in the collection
system at such times, a POTW operator modifies the flow of wastewater through the
treatment plant. During blending, primary treatment is provided for all flows coming
into the facility, and secondary treatment is provided for flows up to the capacity of
the secondary biological treatment units. The latter typically are designed with less
capacity than primary treatment units, which can handle significant variations in flow
and concentration of pollutants, while the microorganisms in biological units are
more sensitive and can be negatively affected by such changes. The excess flows are
diverted around the secondary biological treatment units and then recombined, or
blended, with flows that have been treated by the secondary units. The blended
effluent is usually disinfected prior to discharge to a lake, stream, or coastal
waterbody — particularly if the discharge will affect bathing or fishing waters.
Figure 1 illustrates the process.8
Sanitary engineers and municipal officials say that blending is necessary because
if surges of excess flow from storm events enter the secondary treatment units, they

7 U.S. Environmental Protection Agency. “National Pollutant Discharge Elimination System
(NPDES) Permit Requirements for Municipal Wastewater Treatment Discharges During
Wet Weather Conditions.” 68 Federal Register 216, Nov. 7, 2003, pp. 63042-63052.
8 A typical sewage treatment system schematic showing flows during non-storm conditions
would look the same as Figure 1 but would not show part of the flow being diverted around
secondary treatment units.

will wash out the bacteria which comprise the biological processes used during
secondary treatment. These bacteria are less tolerant of variations in flow volumes
and strength (i.e., more rainwater and more dilute/less sewage) than are systems used
in primary treatment units. If the bacteria are washed out, it can take weeks or
months for a biological treatment unit to recover by re-generating the necessary
microorganisms; in the mean time, excess pollutants may be discharged to the
environment. POTW officials say that it is not possible to build treatment plants to
a capacity where they could treat 100% of all wastewater during peak flows, because
during the more common dry periods, the biological component of the treatment
process would essentially starve to death.
Figure 1. Blending at a Sewage Treatment Facility During a Storm
Source: CRS.
As noted above, POTWs have a number of technological options for managing
peak wet weather flows beyond the boundary of the facility, ranging from correcting
infiltration and inflow in order to reduce the hydraulic load in the sewer system, to
constructing equalizing basins or storage tanks to hold rainwater off-line until flows
can be routed to the treatment plant. Milwaukee and Chicago, for example, have
built elaborate underground tunnel systems to temporarily hold peak flows. Some
cities also are investigating or constructing new or innovative technologies. One of
these is a high-rate clarification process with rapid settling of solids from the waste,
which both provides some initial treatment and reduces the volume of waste material.
Other technological options involve constructing secondary-equivalent treatment
units based on physical/chemical, not biological, processes, which can be started up
quickly and can sit idle between storm events. Depending on land availability, some
of these technologies may be used on-site at the POTW. Others are utilized remotely

and can provide sufficient treatment to comply with EPA’s secondary treatment
discharge limits for suspended solids and BOD5.9
Treatment plant operators view blending as another technological option, one
that is preferable to overflow discharges of untreated waste or sewage backups in
basements. In 2002, the Association of Metropolitan Sewerage Agencies,
representing many of the nation’s large POTWs, conducted a survey on wet weather
management. Thirty percent (78) of AMSA’s members responded, and 37
respondents (47%) said they do blend during wet weather conditions, generally only
a few times per year. Of 41 who do not currently blend, 24 (58%) said that blending
would enable the POTW to meet permit limits all or a majority of the time.10
Proponents of blending argue that, if blending is restricted, municipalities are forced
to spend public resources to build structures with limited public benefit, because of
their infrequent use during occasional storm events. While EPA has not estimated
the national cost of providing sufficient treatment to preclude blending, it has
estimated that the cost of correcting sanitary sewer overflow occurrences nationwide
— a rough surrogate — is $88.5 billion.11 Groups representing municipalities
believe that the cost is likely to be higher, perhaps from $200 to $300 billion.
EPA’s Blending Policy
Blending has been standard engineering practice since the 1970s, engineers say,
as a way to manage peak flows during storm events to prevent conditions that result
in backups into homes and other buildings or overflows of untreated waste into
nearby waters. Nevertheless, controversy exists about the practice, both among
stakeholder groups and also between several of EPA’s regional offices and some at
EPA Headquarters. EPA’s Office of Water has generally supported the practice, but
the Office of Enforcement and Compliance Assistance (OECA) has challenged it.
Officials in OECA have argued that, without certain restrictions, the practice of
blending is not enforceable. With appropriate restrictions, they say, permits
authorizing blending are possible, but crafting permits to do so is complex and
confusing. Others in EPA believe it is possible to write permits that lawfully allow
for blending, and the policy that EPA proposed in November 2003 was intended to
clarify how existing Clean Water Act regulations and permit requirements apply to
wet weather blending scenarios.

9 It is more problematic for these alternative technologies to achieve the percentage removal
requirement of EPA’s secondary treatment rules, because wastes are more diluted in higher
volume wet weather flows than in normal dry weather flows.
10 Association of Metropolitan Sewerage Agencies. “AMSA Wet Weather Survey, Final
Report.” May 2003. 37 p. Available at [http://www.amsa-cleanwater.org/advocacy/
wws urvey/ WetWeatherFinalReport.pdf]
11 U.S. Environmental Protection Agency. Clean Watersheds Needs Survey 2000, Report
to Congress. EPA-832-R-03-001, August 2003, pp. 4-1 - 4-3.

The proposed policy set forth six criteria for managing peak flows, including
blended discharges:
!The final blended discharge must meet effluent limitations based on
the secondary treatment regulation, including applicable percentage
removal requirements, or any more stringent limits necessary to
attain water quality standards.
!The facility’s permit application must specify the treatment scenario
that would be used for peak flow management.
!All flow must receive at least the equivalent of primary clarification.
!Peak flow treatment should be operated as designed and only be
used when flows exceed the capacity of storage units and biological
treatment units.
!The facility’s discharge permit must require sufficient monitoring to
ensure compliance with applicable Clean Water Act requirements.
!The permit also must require that the permittee’s collection system
be properly operated and maintained.
In addition, the policy stated that, where physically possible and economically
achievable, blended effluent should not be discharged to sensitive receiving waters,
such as beaches, public drinking water intakes, waters with threatened or endangered
species, or designated Outstanding National Resource Waters and National Marine
Sanctuaries. EPA’s proposed policy assumed that if blending is done under the
limited terms of the policy, the practice would be fully protective of human health
and the environment.
Issues with Respect to Blending
Criticism of blending encompasses three areas: legality of the practice, impacts
on public health and the environment, and other policy concerns.
As discussed below, a number of groups and interests have weighed in on these
issues, especially in comments on the November 2003 proposed policy.
Environmental advocates oppose the practice on legal grounds, and they and public
health professionals have raised substantial concern based on public health and
environmental issues. Proponents include many cities and municipal and local
government organizations, including the National League of Cities, National
Association of Counties, and Association of Metropolitan Sewerage Agencies
(AMSA). Among states, views differ. Several states supported EPA’s proposed
policy, others supported it with additional restrictions or clarification (such as barring
blended discharges into impaired waters where water quality standards have not yet
been attained), and others opposed the practice based on a variety of policy concerns.
In some instances, individual cities commented in support of the policy, but agencies
of these cites’ home states opposed it (for example, the Miami-Dade Water and
Sewer Department supported it, while the Water Resources Management Division
of Florida’s Department of Environmental Protection opposed it).

The focus of legal concerns over blending rests on whether the practice is
inconsistent with EPA’s existing “bypass” regulation which prohibits “intentional
diversion of waste streams from any portion of a treatment facility” and requires a
determination that “no feasible alternatives” to the bypass exist, including installation
of adequate backup facilities (40 CFR §122.41(m)). Critics argue that these
provisions preclude blending and mandate that POTWs provide larger plant
capacities, including temporary storage, so that all influent flows enter every
treatment process unit. Since secondary treatment units are clearly part of the
treatment unit, according to this view, blending violates the bypass rule’s prohibition
of intentional diversion. A bypass is allowed under EPA regulations when it is
unavoidable, but critics say that the proposed blending policy would have allowed
it as more routine practice. In the November 2003 proposed policy and guidance,
EPA interpreted the bypass rule to allow for blending that complies with the criteria
spelled out in the policy. Proponents of blending argue that, as long as the system is
operated as designed, and the planned operational regime is disclosed to the
permitting authority, it fully complies with the bypass regulation.
Concern over the legality of blending is the basis of actions brought by EPA
enforcement officials in several regions — especially Region III (Philadelphia),
Region IV (Atlanta) and Region VI (Kansas City) — challenging Clean Water Act
permits proposed by state permitting authorities that would allow for blending.12
These EPA regions, supported by states and environmental advocates, have declined
to authorize blending in discharge permits because they believe the practice violates
Clean Water Act rules mandating that all wastewater meet secondary treatment
standards. Some other EPA regions have not prohibited or limited blending in
POTW permits and have generally agreed with supporters of the practice that permits
could, under certain circumstances, authorize re-routing or recombination of waste
without being considered a bypass. For example, supporters say, if analysis of
feasible alternatives has been done and permitting authorities have been notified,
blending does not constitute a bypass. In 2002, a group of cities from Pennsylvania,
Tennessee, and Arkansas and AMSA brought legal action against EPA, alleging that
the prohibition on blending exercised by some EPA regions is not evenly applied
among its regional offices and is not supported by any national regulation. The
lawsuit was dismissed by a federal district court in November 2003, the court saying
that it lacked subject matter jurisdiction over regional guidance documents that do
not constitute final agency action by EPA Headquarters (Pennsylvania Municipal
Authorities Association v. Horinko, D.D.C., No. Civ. 02-01361, Nov. 20, 2003). An
appeal of the case is pending in the U.S. Court of Appeals for the District of
Columbia Circuit.

12 The Clean Water Act allows EPA to delegate permitting responsibility to qualified states,
and EPA has done so for 45 states and one territory. EPA issues permits in the remaining
states and territories. However, even after delegation, EPA retains oversight to ensure that
state-issued permits comply with the CWA’s requirements. If EPA objects in writing to a
permit, the permit may not be issued (§402(d)(2)).

Some EPA enforcement officials reportedly were concerned that issuance of a
national policy would allow POTW operators to reopen consent decrees that now
prohibit blending among other wet weather management controls. Alternatively,
some were said to be concerned that POTWs could potentially sue EPA under the
Federal Tort Claims Act to receive compensation for having installed costly pollution
controls, or that they might petition EPA and states to revise their discharge permits.
Public Health and Environmental Impacts
The largest area of disagreement about blending rests on the issue of public
health and environmental impacts. Supporters of the practice contend that, so long
as the ultimate discharge from a POTW complies with EPA’s secondary treatment
rule or more stringent local water quality limits — as the proposed policy would have
required — public health and the environment are adequately protected.
Disease-causing pathogens, including bacteria, parasites and viruses, can be
found in domestic sewage, and may cause both chronic and acute illnesses, ranging
from cholera, gastroenteritis, infectious hepatitis, and shigellosis to respiratory and
skin infections. Outbreaks of waterborne diseases are associated both with exposures
to contaminated drinking water supplies (resulting from inadequate treatment,
disrupted treatment processes, or cross-contamination of wastewater and water
supplies lines) and exposure to contaminated recreational waters. According to
surveillance data compiled by EPA and the Centers for Disease Control and
Prevention (CDC), states report, on average, approximately 20 such outbreaks per
year linked to drinking water supplies and 30 per year linked to recreational water
exposure, in total causing illness in several thousand persons annually. Since 1989,
the number of gastroenteritis-related outbreaks involving recreational waters has been
gradually increasing.13 The concern of public health and environmental advocates
about blending and other peak flow management issues is whether effluent
containing pathogens is being adequately treated prior to discharge.
EPA’s secondary treatment rules do not specifically limit pathogens. While
primary wastewater treatment processes may remove about one-half of the suspended
solids and BOD from raw wastewater, these processes are not effective in removing
microbial pollutants. Secondary treatment removes about 85% of the organic matter
in sewage and is considerably more effective at removing microorganisms —
including up to 99% of viruses, which are known to cause a significant percentage
of all gastrointestinal illnesses, and 99% of bacteria and parasites.14 Two Canadian
studies reported that primary wastewater treatment removes on average 76% and

27%, respectively, of Cryptosporidium and Giardia lambia, parasites associated with

13 Lee, Sherline H., Deborah A. Levy, Gunther F. Craun, Michael J. Beech, Rebecca L.
Calderon. “Surveillance of Waterborne-Disease Outbreaks — United States, 1999-2000.”:
Nov. 22, 2002/(appears in Morbidity and Mortality Weekly Report) 51 (SS08);1-28.; online
at [http://www.cdc.gov/mmwr/preview/mmwrhtml/ss5108a1.htm].
14 U.S. Environmental Protection Agency. Office of Research and Development. Design
Manual: Municipal Wastewater Disinfection. EPA/625/1-86-021, 1986, Table 2-3, p. 6.

waterborne illness in the United States, and that secondary treatment was needed to
achieve 90% or greater reduction of both.15
When primary treatment alone is provided, very high doses of chlorine are
required to remove viruses or parasites. Moreover, when extra doses of chlorine are
needed to disinfect the primary-treated waste, the chlorine combines with certain
organic matter in the wastewater, creating compounds such as trihalomethanes,
which are hazardous chemicals. These disinfection by-products are carcinogenic and
may increase risk of cancer to humans, thus creating a secondary set of health
Supporters of blending respond to the arguments about public health impacts by
acknowledging that primary treatment alone does not remove all pathogens, but also
by pointing to the paucity of data to actually link human health impacts to discharges
of raw or partially treated sewage. For example, to understand the relative magnitude
of major sources to water contamination, a project by the Water Environment
Research Federation studied occurrence of the parasite Cryptosporidium in two
Wisconsin watersheds and found that contributions of Crypto oocysts from POTW
effluents were nearly insignificant compared with contributions from other sources,
especially wastes in uncontrolled runoff from farm lands and urban/suburban lands.16
While supporters and critics disagree on a number of issues, they are in broad
agreement on one point: more monitoring and investigation are needed to determine
the frequency of sewer overflows and assess the number of people made ill from
waterborne diseases related to such discharges. Data on the incidence of waterborne
diseases in the United States (and other impacts, such as closing of beaches and
shellfish beds) frequently are unable to pinpoint the source or sources of
contaminating agents. Both environmental advocates and groups representing
POTW operators want more study of the possible health problems — the latter saying
that, if there are only limited scientific studies documenting a problem, it is unwise
for the nation to spend scarce public resources to address it. Environmental
advocates say that the lack of data linking wastewater discharges to waterborne
illnesses does not mean that the connection does not exist — the problem is in
quantifying the health risk.
These questions were partly addressed in an August 2004 EPA report to
Congress that was mandated by the Wet Weather Water Quality Act of 2000 (P.L.

106-554) concerning human health and environmental impacts of CSOs and SSOs.

In that report, EPA said that there is an absence of direct cause-and-effect data
relating the occurrence of CSO and SSO discharges to specific human health impacts,
due to factors such as under-reporting of waterborne illness and the presence of
pollutants from other sources. But, based on data from a subset of the nation’s
swimming areas, EPA estimated that between 3,448 and 5,576 illnesses occur

15 Katonak, Rachel and Joan B. Rose. “Public Health Risks Associated with Wastewater
Blending.” Department of Fisheries and Wildlife, Michigan State University, Final report,
Nov. 17, 2003, pp. 22-23.
16 Water Environment Research Foundation. Sources and Variability of Cryptosporidium
in the Milwaukee River Watershed. Stock no. 99HHE2. 2003. 132 p.

annually in people exposed to waters contaminated with bacteria and viruses from
sewer overflows. That estimate, the report said, captures only a portion of the likely
number of annual illnesses attributable to CSO and SSO contamination of
recreational waters.17 Uncertainty about public health impacts was a key factor that
affected finalization of EPA’s proposed policy, as critics contended that the bypass
of secondary treatment in a blending scenario may not adequately protect human
health and that current monitoring strategies do not accurately assess the amount of
harmful bacteria present in surface water after blending.
Water Quality Criteria for Bacteria. In the Federal Register Notice
announcing the proposed blending policy, EPA said that it encourages states to adopt
protective water quality criteria for bacteria in their water quality standards, since
standards based on scientifically sound methods are needed as indicators for
determining the human health risk from pathogenic microorganisms in waste18
discharges. The likelihood of states doing so voluntarily is uncertain, however.
EPA publishes water quality criteria which consist of scientific information on
the concentrations of specific constituents in water which protect aquatic life or
human health. The issue concerning water quality criteria for bacteria stems from the
fact that, in the early years following enactment of the 1972 Clean Water Act, EPA’s
recommended water quality criteria were based on specific levels of fecal coliform
to be used as the indicator organism to protect bathers from gastrointestinal illness
in recreational waters, and consequently most state-adopted water quality standards
have been based on that indicator since the 1970s. In 1986, EPA recommended that
states adopt criteria based on Escherichia coli (E. coli) and enterococci to
demonstrate the presence of fecal pollution, because newer epidemiological studies
have found a stronger correlation between swimming-associated gastroenteritis and
these organisms than with fecal coliform or other indicator organisms.
In the Beaches Environmental Assessment and Coastal Health Act of 2000
(BEACH Act, P.L. 106-284), Congress required the 30 coastal and Great Lakes states
to adopt EPA’s 1986 water quality criteria for pathogens by April 2004. As required
by that law, in July 2004 EPA proposed federal water quality criteria for 20 states
that missed the deadline for adopting more up-to-date criteria for pathogens in their
water quality standards. At that time, EPA said that 16 states were in the process of
adopting revised criteria, while four states had not moved forward on the criteria.
Most of the 20 states had standards in place, but EPA did not think they were
adequately protective of human health because they rely on fecal coliforms as the
pathogen indicator, rather than incorporating limits for E. coli. However, wastewater
treatment officials and some in the scientific community have questioned use of the
1986 criteria document because it relies on data that are more than 20 years old. EPA
acknowledges that problem and is working on additional epidemiological studies of
pathogen indicators of illnesses at beaches in order to develop new water quality
criteria to protect swimmers in recreational waters by October 2005, as mandated by

17 U.S. Environmental Protection Agency. Office of Water. Report to Congress, Impacts
and Control of CSOs and SSOs. EPA 833-R-04-001. August 2004. p. 6-9.
18 68 Federal Register 216, Nov. 7, 2003, p. 63051.

the BEACH Act. In the mean time, the law requires EPA to press states to adopt
standards based on the existing criteria for pathogens.
Other Policy Concerns
Critics of EPA’s November 2003 proposed policy, including environmental
advocates and a number of states, believe that the proposal would not have
definitively restricted blending to wet weather events only. Some state officials, for
example, said that allowing blending undermines the POTW’s incentive for
removing wet weather infiltration and inflow and otherwise improving the collection
system.19 These and other critics asserted that the policy would allow bypasses to
become routine and would relieve treatment plant operators from analysis to
determine if there are feasible alternatives to bypass/blending. According to these
critics, blending succeeds in meeting permit discharge limits by virtue of dilution
(mixing), not technological pollution control. Further, blending in effect shifts the
cost of treating wet weather flows to drinking water suppliers, who become
responsible for removing residual microorganisms or harmful disinfection byproducts
that enter the water supply after discharge by the POTW. Others recognize the need
for POTWs to blend wastewater in certain temporary circumstances but say that it
should not be used as a long-term solution in order to avoid treating peak and base
flows when treatment is feasible and can be done according to standard engineering
Yet, while some were critical that the proposed policy would be too flexible,
others believed that it would be too restrictive. Some of these critics, including
municipal officials and sanitary engineering professionals that support blending,
believed that the proposal contained a number of vague or excessively broad terms
that needed to be further refined, such as what is “generally accepted good
engineering practice” for design and operation of a POTW. They also charged that
the policy sought to restrict discharge of blended wastes into sensitive receiving
waters and that it would have required the system operator to utilize all peak flow
capacity of sewers and other storage devices before commencing blending. These
restrictions, they say, amount to EPA dictating design and operations of the treatment
facility, which is contrary to the Clean Water Act. They argued that ambiguities
would allow different EPA regions to interpret the policy differently, resulting in
inconsistencies much like those that EPA had hoped to resolve by issuing the policy.
These critics urged EPA to require that the policy be binding in all regions. On the
other hand, a number of commenters urged EPA to do the opposite: to clarify that
the final policy, as in the proposal, would allow states and regions the option to not
authorize POTWs to blend, if that is their preference.
A number of critics of EPA’s proposal — both those who oppose blending and
others who favor it — asserted that the policy represented more than just
interpretation of current rules, that it fundamentally would have changed existing

19 See, for example, Letter from Larson, Jeffrey H., Manager, Permitting, Compliance and
Enforcement Program, Environmental Protection Division, Water Protection Branch,
Georgia Department of Natural Resources. EPA Docket ID No. OW-2003-0025-0482, Jan.

9, 2004, 6 p.

requirements, such as the bypass rule and the ability of operators (not EPA) to design
and operate plants in order to meet permit requirements. Some of these critics shared
the view that in the 2003 proposal, EPA had transformed the policy into a
rulemaking. As presented, the proposal was not a formal rulemaking (which would
be subject to the notice and comment procedures of the Administrative Procedure Act
(APA), although EPA did solicit public comments that it compiled in a docket), nor
did it contain changes to current regulations. EPA characterized the policy as an
interpretation of current rules and a draft guidance to implement such an
interpretation. In addition, so long as the policy was not considered by EPA to be a
rule, it was unlikely to be seen by EPA as subject to provisions of the Congressional
Review Act (CRA, 5 U.S.C. §§801-808), which requires that before a rule can
become final, it must be filed with the House and Senate and the General Accounting
Office. The CRA allows Congress to disapprove agencies’ rules by enacting a joint
resolution of disapproval.20
Congressional Interest and Status of the Proposal
In Congress, the issues and practice of blending have drawn some Members’
attention. In January 2004, during the public comment period on the proposed
policy, Members with differing views on the proposal wrote to EPA to express
concerns about it. In one letter, four House committee and subcommittee chairmen
urged EPA to issue the policy, but said that the draft needed to clarify inconsistent
regional enforcement. As drafted, the proposal would overstep federal authority and
bypass the role of states in clean water decisionmaking, the lawmakers said. Further,
they asserted that the proposal would establish “new back-door regulatory-type
requirements to be imposed at the discretion of the permitting authority [that] will21
lead to less, not greater, national consistency.” These Members called for EPA to
revise the guidance to make clear that blending is an acceptable practice and to make
sure that the policy is implemented in a reasonable and consistent manner nationally.
At the same time, a bipartisan letter from 64 House Members of the
Congressional Coastal Caucus criticized the draft policy as an environmental rollback
that would endanger public health. Focusing on the concern that blending may lead
to discharges of microbial pathogens into waterways, the letter faulted the draft
policy for not ensuring that disinfection be required when a POTW blends its

20 For additional information, see CRS Report RL32240, The Federal Rulemaking Process:
An Overview, by Curtis Copeland. It should be noted, however, that the CRA has a broad
definition of the term “rule” that encompasses not only formal notice and comment
proceedings under the APA but also policy statements, guidance, and other agency issuances
that may have a legal or practical binding effect on the regulated public. See CRS Report
RL30116, Congressional Review of Agency Rulemaking: An Update and Assessment After
Nullifcation of OSHA’s Ergonomics Standard, by Mort Rosenberg, pp. 2-3.
21 Letter from Don Young, Chairman, Committee on Transportation and Infrastructure, John
J. Duncan, Jr., Chairman, Subcommittee on Water Resources and Environment, Tom Davis,
Chairman, Committee on Government Reform, Doug Ose, Chairman, Subcommittee on
Energy Policy, Natural Resources, and Regulatory Affairs. EPA Docket No. ID OW-2003-

0025-0533, Jan. 7, 2004, 3 p.

effluent. This letter recognized the problem of excess flows during storms, but said
that blending sewage is an unacceptable alternative and that treatment facilities
should consider building additional capacity or short-term storage until all the sewage
can be treated with biological processes.22
Several developments have followed in the 109th Congress. On April 13, 2005,
the House Transportation and Infrastructure Committee’s Water Resources and
Environment Subcommittee held a hearing about the practice of blending and
received testimony from a number of municipal officials who support blending and
environmental advocates who discussed their opposition to it. Also, legislation has
been introduced that is intended to prohibit EPA from issuing rules or guidance that
would authorize blending, unless necessary to prevent loss of life, personal injury,
or severe property damage (H.R. 1126). (Congress took no action on a similar bill
that was introduced at the end of the 108th Congress, H.R. 5421.)
Further, in approving legislation providing FY2006 appropriations for EPA
(H.R. 2361), the House adopted an amendment that would prohibit EPA from
finalizing, issuing, implementing, or enforcing the 2003 proposed blending policy.
Supporters of the amendment, which the House approved by voice vote on May 19,
2005, said that the provision in the bill was not intended to have any impact on
existing policies of EPA regions and states that currently allow blending, or on any
Clean Water Act permit that allows blending. The amendment’s sponsor,
Representative Stupak, said it would maintain the status quo by preventing EPA from
adopting policies that would weaken environmental standards.23
After publication of the proposed policy in November 2003, EPA solicited
public comments for a 120-day period, compiling a docket with more than 98,000
comments. Many observers had expected EPA to issue a final version of the policy
in mid- or late-2004, but the agency did not do so. Issues that reportedly continued
to be unresolved included whether the policy would apply only to future CSO
settlements or also to past enforcement settlements (if applied retroactively, the
guidance could force the re-opening of consent decrees in a number of cases) and
whether the guidance must require municipalities to conduct a “no feasible
alternatives” analysis to prove that blending is necessary. On May 19, 2005 (the
same day that the House adopted the Stupak amendment to H.R. 2361), EPA officials
announced that, after reviewing the public comments and testimony presented to
Congress, the agency had decided to withdraw the November 2003 proposal and not
finalize the policy. The announcement said that EPA will continue to review
alternatives (i.e., a revised policy or perhaps a rulemaking) to develop the most
feasible approaches to treating wastewater and protecting communities.
Not surprisingly, environmental advocates were pleased with EPA’s decision
to abandon the proposal. On the other hand, municipal groups and other supporters
of blending and the proposed policy were disappointed. They indicated that EPA’s
failure to issue a definitive policy continues to leave communities in an uncertain

22 “Competing Hill Critiques Hand EPA Tough Choices on Blending Policy.” Inside EPA,
vol. 25 no. 5, Jan. 30, 2004, p. 16.
23 Congressional Record, daily ed., May 19, 2005, p. H3665.

position about whether and, if so, when treatment plant operators may use blending.
Until the agency clarifies these issues, these groups say, municipalities are unsure
about EPA’s legal interpretation and what treatment plant improvements cities must
make to ensure their compliance with the law.