[Federal Register Volume 61, Number 216 (Wednesday, November 6, 1996)]
[Notices]
[Pages 57425-57429]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 96-28430]
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ENVIRONMENTAL PROTECTION AGENCY
[FRL-5646-6]
Questions and Answers Regarding Implementation of an Interim
Permitting Approach for Water Quality-Based Effluent Limitations in
Storm Water Permits
AGENCY: Environmental Protection Agency.
ACTION: Notice.
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SUMMARY: Notice is hereby given that the Environmental Protection
Agency (EPA) has developed a set of questions and answers to assist
municipalities and permitting authorities in implementing its recent
policy outlining an interim approach for incorporating water quality-
based effluent limitations into storm water permits.
Background and Purpose
On August 26, 1996, the EPA published in the Federal Register (61
FR 43761) a policy outlining an interim approach for incorporating
water quality-based effluent limitations into National Pollution
Discharge Elimination System (NPDES) storm water permits. The policy
was developed to address the variable nature of storm water discharges,
and the typical lack of information on which to base numeric water
quality-based effluent limitations (expressed as concentration and
mass). The policy addresses issues related to the type of effluent
limitations that are most appropriate for NPDES storm water permits to
provide for the attainment of water quality standards. Since the policy
only applies to water quality-based effluent limitations, it is not
intended to affect technology-based limitations, such as those based on
effluent guidelines or the permit writer's best professional
judgements, that are incorporated into storm water permits.
Based on numerous requests for additional information regarding the
implementation of the policy, the EPA has developed the following set
of questions and answers. For convenience, the policy is also reprinted
below.
Policy Statement
In response to recent questions regarding the type of water
quality-based effluent limitations that are most appropriate for
National Pollutant Discharge Elimination System (NPDES) storm water
permits, the Environmental Protection Agency (EPA) is adopting an
interim permitting approach for regulating wet weather storm water
discharges. Due to the nature of storm water discharges, and the
typical lack of information on which to base numeric water quality-
based effluent limitations (expressed as concentration and mass), EPA
will use an interim permitting approach for NPDES storm water permits.
The interim permitting approach uses best management practices
(BMPs) in first-round storm water permits, and expanded or better-
tailored BMPs in subsequent permits, where necessary, to provide for
the attainment of water quality standards. In cases where adequate
information exists to develop more specific conditions or limitations
to meet water quality standards, these conditions or limitations are to
be incorporated into storm water permits, as necessary and appropriate.
This interim permitting approach is not intended to affect those storm
water permits that already include appropriately derived numeric water
quality-based effluent limitations. Since the policy only applies to
water quality-based effluent limitations, it is not intended to affect
technology-based limitations, such as those based on effluent
guidelines or the permit writer's best professional judgement, that are
incorporated into storm water permits.
[[Page 57426]]
Each storm water permit should include coordinated and cost-
effective monitoring program to gather necessary information to
determine the extent to which the permit provides for attainment of
applicable water quality standards and to determine the appropriate
conditions or limitations for subsequent permits. Such a monitoring
program may include, ambient monitoring, receiving water assessment,
discharge monitoring (as needed), or a combination of monitoring
procedures designed to gather necessary information.
This interim permitting approach applies only to EPA, however, EPA
also encourages authorized States and Tribes to adopt similar policies
for storm water permits. This interim permitting approach provides
time, where necessary, to more fully assess the range of issues and
possible options for the control of storm water discharges for the
protection of water quality. This interim permitting approach may be
modified as a result of the ongoing Urban Wet Weather Flows Federal
Advisory Committee policy dialogue on this subject.
Questions and Answers
Question 1: Must EPA require that storm water dischargers,
industrial or municipal, be subject to numeric water quality-based
effluent limitations (expressed as concentration and mass) in order to
attain water quality standards (WQS)?
Answer 1: No. Although National Pollutant Discharge Elimination
System (NPDES) permits must contain conditions to ensure that water
quality standards are met, this does not require the use of numeric
water quality-based effluent limitations. Under the Clean Water Act
(CWA) and NPDES regulations, permitting authorities may employ a
variety of conditions and limitations in storm water permits, including
best management practices, performance objectives, narrative
conditions, monitoring triggers, action levels (e.g., monitoring
benchmarks, toxicity reduction evaluation action levels), etc., as the
necessary water quality-based limitations, where numeric water quality-
based effluent limitations are determined to be unnecessary or
infeasible.
Analysis
A. The Clean Water Act does not require numeric effluent
limitations.
Section 301 of the CWA requires that discharger permits include
effluent limitations necessary to meet State or Tribal WQS. Section 502
defines ``effluent limitation'' to mean any restriction on quantities,
rates, and concentrations of constituents discharged from point
sources. The CWA does not say that effluent limitations need be
numeric. As a result, EPA and States have flexibility in terms of how
to express effluent limitations.
B. EPA's regulations do not always require numeric effluent
limitations.
EPA has, through regulation, interpreted the statute to allow for
non-numeric limitations (e.g., ``best management practices'' or BMPs,
see 40 CFR 122.2) to supplement or replace numeric limitations in
specific instances that meet the criteria specified at 40 CFR
122.44(k). This regulation essentially codifies a court case addressing
storm water discharges. NRDC v. Costle, 568 F.2d 1369 (D.C. Cir. 1977).
In that case, the Court stated that EPA need not establish numeric
effluent limitations where such limitations were infeasible.
C. EPA has interpreted the statute and regulations to allow BMPs in
lieu of numeric limitations.
EPA has defended use of BMPs as a substitute for numeric
limitations in litigation involving storm water discharges (CBE v. EPA,
91-70056 (9th Cir.)(brief on merits)) and in correspondence (Letter
from Michael Cook, EPA, to Peter Lehner, NRDC, May 31, 1995). EPA has
found that numeric limitations for storm water permits can be very
difficult to develop at this time because of the existing state of
knowledge about the intermittent and variable nature of these types of
discharges and their effects on receiving waters. Some storm water
permits, however, currently do contain numeric water quality-based
effluent limitations where adequate information exists to derive such
limitations.
Question 2: Has EPA provided guidance on a methodology for deriving
numeric water quality-based effluent limitations?
Answer 2: Yes, but primarily for continuous wastewater discharges
at low flow conditions in the receiving water, not intermittent wet
weather discharges during high flow conditions. Regulations at 40 CFR
122.44(d) specify the requirements under which permitting authorities
establish water quality-based effluent limitations when a facility has
the ``reasonable potential'' to cause or contribute to an excursion of
numeric or narrative water quality criteria. In addition, EPA guidance
in the Technical Support Document for Water Quality-Based Toxics
Control (TSD) and the NPDES Permit Writers Training Manual,
supplemented with total maximum daily load (TMDL) and modeling
guidance, supports issuing permits that include numeric water quality-
based effluent limitations. This guidance was based on crafting numeric
water quality-based effluent limitations using TMDLs, or calculations
similar to those used in developing TMDLs, and wasteload allocations
(WLAs) derived through modeling. EPA expects the Urban Wet Weather
Flows Federal Advisory Committee (60 FR 21189, May 1, 1995) will review
this issue at greater length and may provide recommendations on how to
proceed.
Question 3: Why can numeric water quality-based effluent
limitations be difficult to derive for storm water permits?
Answer 3: Storm water discharges are highly variable both in terms
of flow and pollutant concentrations, and the relationships between
discharges and water quality can be complex. The water quality impacts
of storm water discharges are related to the uses designated by States
and Tribes in their WQS, the quality of the storm water discharge
(e.g., conventional or toxic pollutants conveyed to the receiving
water) and quantity of the storm water (e.g., erosion and loss of
habitat caused by increased flows and velocity). Uses may be impacted
by both water quality and water quantity. Depending on site-specific
considerations, some of the water quality impacts of storm water
discharges may be more related to the physical effects (e.g., stream
bank erosion, streambed scouring, extreme temperature variations,
sediment smothering) than the type and amount of pollutants present in
the discharge. For municipal storm water discharges in particular, the
current use of system-wide permits and a variety of jurisdiction-wide
BMPs, including educational and programmatic BMPs, does not easily lend
itself to the existing methodologies for deriving numeric water
quality-based effluent limitations. These methodologies were designed
primarily for process wastewater discharges which occur at predictable
rates with predictable pollutant loadings under low flow conditions in
receiving waters. Using these methodologies, limitations are typically
derived for each specific outfall to be protective of low flows in the
receiving water. Because of this, permit writers have not made wide-
spread use of the existing methodologies and models for storm water
discharge permits. In addition, wet weather modeling is technically
more difficult and expensive than the simple dilution models generally
used in the permitting process.
Question 4: Has EPA previously recognized the technical difficulty
in deriving numeric water quality-based
[[Page 57427]]
effluent limitations for storm water discharges?
Answer 4: Yes. EPA recognized the technical difficulty in deriving
numeric water quality-based effluent limitations for wet weather
discharges in its brief on the merits in Citizens for a Better
Environment (CBE) v. United States Environmental Protection Agency, 91-
70056 (9th Cir.) and in the Great Lakes Water Quality Guidance (58 FR
20841, April 16, 1993).
In the CBE case, EPA explained why it was technically infeasible to
derive numeric water quality-based effluent limitations for the
discharge of metals in storm water into South San Francisco Bay and
asserted that a water quality-based effluent limitation could take the
form of a narrative statement, such as a BMP, if it was infeasible to
derive a numeric limitation. In explaining its arguments in the CBE
case, EPA cited 40 CFR 122.44(k)(2), which provides that BMPs may be
imposed in NPDES permits ``to control or abate the discharge of
pollutants when * * * [n]umeric effluent limitations are infeasible.''
In the Great Lakes Water Quality Guidance, EPA did not extend the
method for calculating wasteload allocations, the basis for numeric
water quality-based effluent limitations, to storm water or combined
sewer overflow (CSO) discharges because the varying nature of these
discharges is inconsistent with the assumptions used in developing the
guidance. The Great Lakes Water Quality Guidance defers to national
guidance and policy on wet weather and does not seek to establish a
separate and distinct set of wet weather requirements. EPA expects the
Urban Wet Weather Flows Advisory Committee to provide recommendations
about how to address the broader technical issues involved in achieving
compliance with WQS in a wet weather context.
Question 5: What are the potential problems of using standard
methodologies to derive numeric water quality-based effluent
limitations for storm water permits?
Answer 5: Correctly derived numeric water quality-based effluent
limitations provide a greater degree of confidence that a discharge
will not cause or contribute to an exceedance of the WQS, because
numeric water quality-based effluent limitations are derived directly
from the numeric component of those standards. In addition, numeric
water quality-based effluent limitations can avoid the expense
associated with overly protective treatment technologies because
numeric water quality-based effluent limitations provide a more
precisely quantified target for permittees. Potential problems of
incorporating inappropriate numeric water quality-based effluent
limitations rather than BMPs in storm water permits at this time are
significant in some cases. Deriving numeric water quality-based
effluent limitations for any NPDES permit without an adequate effluent
characterization, or an adequate receiving water exposure assessment
(which could include the use of dynamic modeling or continuous
simulations) may result in the imposition of inappropriate numeric
limitations on a discharge. Examples of this include the imposition of
numeric water quality criteria as end-of-pipe limitations without
properly accounting for the receiving water assimilation of the
pollutant or failure to account for a mixing zone (if allowed by
applicable State or Tribal WQS). This could lead to overly stringent
permit requirements, and excessive and expensive controls on storm
water discharges, not necessary to provide for attainment of WQS.
Conversely, an inadequate effluent characterization could lead to water
quality-based effluent limitations that are not stringent enough to
provide for attainment of WQS. This could result because effluent
characterization and exposure assessments for discharges with high
variability of pollutant concentrations, loadings, and flow are more
difficult than with process wastewater discharges at low flows.
Question 6: How are water quality-based effluent limitations
developed for combined sewer overflow (CSO) discharges?
Answer 6: The CSO Control Policy issued by EPA on April 19, 1994
(59 FR 18688) provides direction on compliance with the technology-
based and water quality-based requirements of the CWA for communities
with combined sewer systems. The CSO Policy provides for implementation
of technology-based requirements (expressed as ``nine minimum
controls'') by January 1, 1997.
In addition, under the CSO Policy, communities are also expected to
develop long-term control plans that will provide for attainment of WQS
through either the ``presumption approach'' or the ``demonstration
approach.'' Under the presumption approach, CSO controls would be
presumed to attain WQS if certain performance criteria are met. A
program that meets the criteria specified in the CSO policy is presumed
to provide an adequate level of control to meet the water quality-based
requirements of the CWA, provided the permitting authority determines
that such presumption is reasonable based on characterization,
monitoring, and modeling of the system, including consideration of
sensitive areas. Under the demonstration approach, the permittee would
demonstrate that the selected CSO controls, when implemented, would be
adequate to meet the water quality-based requirements of the CWA.
The CSO Policy anticipates that it will be difficult in the early
stages of permitting to determine whether numeric water quality-based
effluent limitations are necessary for CSOs, and, if so, what the
limitations should be. For that reason, in the absence of sufficient
data to evaluate the need for numeric water quality-based effluent
limitations, the Policy recommends that the first phase of CSO permits
(``Phase I'') contain a narrative requirement to comply with WQS.
Further, so-called ``Phase II'' permits would contain water quality-
based effluent limitations, as provided in 40 CFR 122.44(d)(1) and
122.44(k), that may take the form of numeric performance or design
standards, such as a certain number of overflow events or a certain
percent volume capture. Generally, only after the long-term control
plan is in place and after collection of sufficient water quality data
(including applicable wasteload allocations developed during a TMDL
process) would numeric water quality-based effluent limitations be
included in the permit. This would likely occur only after several
permitting cycles.
Question 7: If BMPs alone are demonstrated to provide adequate
water quality protection, are additional controls necessary?
Answer 7: No. If the permitting authority determines that, through
implementation of appropriate BMPs required by the NPDES storm water
permit, the discharges have the necessary controls to provide for
attainment of WQS and any technology-based requirements, additional
controls need not be included in the permit. Conversely, if a
discharger (municipal or industrial) fails or refuses to adopt and
implement adequate BMPs, the permitting authority may have to consider
other approaches to ensure water quality protection.
If, however, the permitting authority has adequate information on
which to base more specific conditions or limitations, such limitations
are to be incorporated into storm water permits, as necessary and
appropriate. Such conditions or limitations may include an integrated
suite of BMPs, performance objectives, narrative standards, monitoring
triggers, numeric water quality-based effluent limitations,
[[Page 57428]]
action levels, etc. Storm water permits may also need to include
additional requirements to receive State or Tribal 401 certifications.
Question 8: What is EPA doing to develop information about the
linkage between BMPs and water quality and to facilitate a watershed-
based approach to storm water permitting?
Answer 8: The Agency has cooperative agreements with WERF (Water
Environment Research Foundation) and ASCE (American Society of Civil
Engineers) to research which BMPs are most effective under which
circumstances. The results of this research should provide permitting
authorities and permittees with information about how to evaluate the
effectiveness of different kinds of BMPs in different circumstances and
to select the most appropriate controls to achieve water quality
objectives. EPA also has cooperative agreements with the Watershed
Management Institute and other organizations to conduct research over
the next two to four years that will examine the capability of storm
water BMPs to improve receiving water quality and restore/protect the
biological integrity of those waters. EPA expects the Urban Wet Weather
Flows Federal Advisory Committee to provide recommendations on how to
permit storm water discharges on a watershed basis.
Question 9: The interim permitting approach states that permits
should include monitoring programs to generate necessary information to
determine the extent to which permits are providing for the attainment
of water quality standards. What types of monitoring should be included
and how much monitoring is necessary?
Answer 9: The amount and types of monitoring necessary will vary
depending on the individual circumstances of each storm water
discharge. EPA encourages dischargers and permitting authorities to
carefully evaluate monitoring needs and storm water program objectives
so as to select useful and cost-effective monitoring approaches. For
most dischargers, storm water monitoring can be conducted for two basic
reasons: (1) to identify if problems are present, either in the
receiving water or in the discharge, and to characterize the cause(s)
of such problems; and (2) to assess the effectiveness of storm water
controls in reducing contaminants and making improvements in water
quality.
Under the NPDES storm water program, large and medium municipal
separate storm sewer system permittees are required to conduct
monitoring. EPA recommends that each such municipal permittee design
the monitoring effort to be supportive of the goals and objectives of
its storm water management program when developing such a program for
the term of its NPDES permit. To accomplish this, a municipal permittee
may use a variety of storm water monitoring tools including receiving
water chemistry; receiving water biological assessments (benthic
invertebrate surveys, fish surveys, habitat assessments, etc.);
effluent monitoring; including chemical, whole effluent and visual
examinations; illicit connections screening; and combinations thereof,
or other methods. Techniques that assess receiving waters will help to
identify the degree to which storm water discharges are contributing to
any water quality problems. Techniques that assess storm water
discharge characteristics will help to identify potential causes of any
identified water quality problems. The municipal permittee, in
conjunction with the applicable NPDES permitting authority, should
determine which monitoring approaches would be most appropriate given
the objectives of the storm water management program. If municipal
permittees conduct ambient monitoring, it may be most cost-effective to
pool resources with other organizations (including, for example, other
municipalities, States, and Tribes) conducting monitoring within the
same watershed. This could be best accomplished through a coordinated
watershed monitoring strategy.
For industrial storm water dischargers, monitoring may be required
under the terms of an NPDES permit for storm water discharges. For
those industrial storm water permits that do require monitoring, this
is typically done to characterize contaminants that might be found in
the industrial runoff and/or to assess the effectiveness of the
industrial storm water pollution prevention plan in reducing these
contaminants. This typically involves end-of-pipe chemical-specific
monitoring. End-of-pipe monitoring may be more appropriate for an
industrial facility than for a municipal permittee, given the
industrial facility's more discrete site characteristics, which make
management strategies such as collection and treatment more feasible.
Industries, for the most part, have readily defined storm water
conveyances into which runoff flows from discrete drainage areas.
Industries may more readily identify and control existing on-site
sources of storm water contamination or provide collection and
treatment within these discrete drainage areas to control pollutant
concentrations in their storm water discharges.
EPA and other organizations are currently working to improve
approaches for monitoring storm water and the potential effects upon
water quality. These new approaches are called storm water program
``environmental indicators.'' Environmental indicators are designed to
be more meaningful monitoring tools that storm water dischargers can
use to conduct storm water monitoring for the purposes described above.
A manual describing each of the recommended storm water program
environmental indicators is being prepared by the Center for Watershed
Protection in Silver Spring, Maryland. That manual is expected to be
ready by the end of August 1996 and should provide useful information
for storm water dischargers contemplating the need to develop a cost-
effective, meaningful storm water monitoring program. In addition, EPA
expects the Urban Wet Weather Flows Federal Advisory Committee to
provide recommendations on how to better monitor storm water and other
wet weather discharges using a watershed approach.
Question 10: Does this interim permitting approach apply to both
storm water discharges associated with industrial activity and storm
water discharges from municipal separate storm sewer systems?
Answer 10: Yes. The interim permitting approach is applicable to
both discharges from municipal separate storm sewer systems and storm
water discharges associated with industrial activity (as defined by 40
CFR 122.26(b)(14)). The interim permitting approach would not affect,
however, permits that already incorporate appropriately derived numeric
water quality-based effluent limitations. Since the interim permitting
approach only addresses water quality-based effluent limitations, it
also does not affect technology-based effluent limitations, such as
those based on effluent limitations guidelines or developed using best
professional judgement, that are incorporated into storm water permits.
In addition, particularly for some industries, adequate information may
already have been collected with which to assess the reasonable
potential for a storm water discharge to cause or contribute to an
excursion of a WQS, and from which a numeric water quality-based
effluent limitation can be (or has been) appropriately derived. An
adequate amount of storm water pollutant source information may also
exist with which to assess the effectiveness of the industrial storm
[[Page 57429]]
water control measures in complying with the limitations and in
reducing storm water contaminants for protecting water quality.
DATE: The policy was signed by the Assistant Administrator for Water on
August 1, 1996.
FOR FURTHER INFORMATION CONTACT: Copies of the policy with the
questions and answers are available by writing the U.S. Environmental
Protection Agency, Water Resources Center, Mail Code 4101, 401 M
Street, SW, Washington, D.C., 20460, or by calling (202) 260-7786. If
you have additional questions about the policy, please contact, Bill
Swietlik, Storm Water Phase I Matrix Manager, Office of Wastewater
Management, at (202) 260-9529 or William Hall, Urban Wet Weather Flows
Matrix Manager, Office of Wastewater Management, at (202) 260-1458, or
by Internet at hall.william@epamail.epa.gov.
Dated: October 11, 1996.
Michael B. Cook,
Director, Office of Wastewater Management, Designated Federal Official.
[FR Doc. 96-28430 Filed 11-5-96; 8:45 am]
BILLING CODE 6560-50-P
