### Memo Clarifying EPA\'s Position on the Use of Daily Time Increment When Establishing Total Maximum Daily Loads for Pollutants 

Dated Nov. 15, 2006

MEMORANDUM

SUBJECT: Establishing TMDL \"Daily\" Loads in Light of the Decision by
the U.S. Court of Appeals for the D.C. Circuit in Friends of the Earth,
Inc. v. EPA, et al ., No. 05-5015, (April 25, 2006) and Implications,
for NPDES Permits

FROM: Benjamin H. Grumbles Assistant Administrator

TO: Director, Office off Ecosystem Protection, Region 1 Director,
Division of Environmental Planning and Protection, Region 2 Water
Division Directors, Regions 3-7 and Region 9 Director, Office of
Ecosystems Protection and Remediation, Region 8 Director, Office of
Environmental Cleanup, Region 10

The purpose of this memorandum is to clarify EPA\'s expectations
concerning the appropriate time increment used to express \"total
maximum daily loads\" (TMDLs) in light of the recent decision by the
U.S. Court of Appeals for the D.C. Circuit in Friends of the Earth, Inc.
v. EPA, et al ., No. 05-5015 (D.C. Cir. 2006). In Friends of the Earth ,
the D.C. Circuit held that two TMDLs for the Anacostia River (one
established by EPA and one approved by EPA) did not comply with the
Clean Water Act because they were not expressed as \"daily\" loads.

The Friends of the Earth decision has raised some questions regarding
the establishment of both TMDLs and effluent limits in National
Pollutant Discharge Elimination System (NPDES) permits that implement
wasteload allocations established in TMDLs. As explained in more detail
below, EPA recommends that all future TMDLs and associated load
allocations and wasteload allocations be expressed in terms of daily
time increments. However, EPA does not believe that the Friends of the
Earth decision requires any changes to EPA\'s existing policy and
guidance describing how a TMDL\'s wasteload allocations are implemented
in NPDES permits.

EPA\'s Expectations Regarding \"Daily\" Loads in TMDLs

EPA continues to believe that the use of the word \"daily\" in the term
\"total maximum daily load\" is not an unambiguous direction from
Congress that TMDLs must be stated in the form of a uniformly applicable
24-hour load. However at this time, there is significant legal
uncertainty about whether courts across the country will follow the
reasoning of the D.C. Circuit decision in Friends of the Earth or that
of the U.S. Court of Appeals for the Second Circuit in their decision in
NRDC v. Muszynski .

1 In NRDC v. Muszynski , 268 F.3d 91 (2\"d Cir. 2001), NRDC challenged
EPA\'s approval of nutrient TMDLs with annual loads established by New
York for reservoirs. The Second Circuit held that \"the term \`total
maximum daily load\' is susceptible to a broader range of meanings\"
than loads calculated on a daily basis. 268 F.3d at 98-99. The D.C.
Circuit decision in Friends of the Earth is controlling legal precedent
for cases brought in the District of Columbia Circuit while the Second
Circuit decision in Musrynski is controlling legal precedent in cases
brought in the Second Circuit, which includes the States of New York,
Connecticut, and Vermont. EPA encourages the three States within the
Second Circuit, to submit TMDLs with \"daily\" loads in a manner
consistent with this memorandum. EPA also recognizes that, while the
Second Circuit did not vacate the TMDLs in question merely because they
did not contain \"daily\" loads, it required a reasoned explanation for
the choice of any particular \"non-daily\" load.

\+ If consistent with the applicable water quality standard and
technically suitable for the pollutant and water body type in question,
a TMDL and associated load allocations and wasteload allocations may be
expressed as both minimum and, maximum daily loads, or as average daily
loads. For example, a TMDL for the pollutant parameter pH may include
both minimum and maximum values consistent with how the applicable WQS
for the parameter pH is expressed (commonly as a range.)

\+ If technically appropriate and consistent with the applicable water
quality standard, it may also be appropriate for the TMDL and associated
load allocations and wasteload allocations to be expressed in terms of
differing maximum daily values depending on the season of the year,
stream flow (e.g., wet v. dry weather conditions) or other factors. In
situations where pollutant loads, water body flows, or other
environmental factors are highly dynamic, it may be appropriate for
TMDLs and associated allocations to be expressed as functions of
controlling factors such as water body flow. For example, a
load-duration curve approach to expressing a TMDL and associated
allocations might be appropriate, provided it clearly identifies the
allowable daily pollutant load for any given day as a function of the
flow occurring that day. Using the load-duration curve approach also has
the advantage of addressing seasonal variations as required by the
statute and the regulations.

\+ For TMDLs that are expressed as a concentration of a pollutant, a
possible approach would be to use a table and/or graph to express the
TMDL as daily loads for a range of possible daily stream flows. The
in-stream water quality criterion multiplied by daily stream flow and
the appropriate conversion factor would translate the applicable
criterion into a daily target (TMDL).

EPA will issue additional technical guidance providing specific
information regarding the establishment of daily loads for specific
pollutants that will take into consideration the averaging period of the
pollutant, the type of water body, and the type of sources the TMDL
needs to address.

Facilitating Implementation of Wasteload Allocations through the NPDES
Permit Process

In certain circumstances (e.g., impairments caused by storm water), or
where the applicable water quality criteria are expressed as a long-term
average, it may be appropriate for TMDL documents or their supporting
analysis to clearly set forth the implementation-related assumptions
underlying any wasteload allocation expressed as a \"daily\" load. To
facilitate implementation of such a load in water bodies where the
applicable water quality standard is expressed in non-daily terms, it
may be appropriate for the TMDL documentation to include, in addition to
wasteload allocations expressed in daily time increments, wasteload
allocations expressed as weekly, monthly, seasonal, annual, or other
appropriate time increments. When this approach is taken, the TMDL and
its supporting documentation should clearly explain that the non-daily
loads and allocations are implementation-related assumptions of the
daily wasteload allocations and are included to facilitate
implementation of the daily allocations as appropriate in NPDES permits
and nonpoint source directed management measures. The supporting
documentation should discuss the reasons for, and assumptions behind,
the non-daily loads to facilitate their understanding and use in the
implementation phase.

Recommendations Concerning Existing TMDLs and TMDLs in Process

Through significant effort of the States and EPA regions, more than
20,000 TMDLs have been established, most of them in the last five or six
years. EPA\'s database also shows that approximately 65,000 causes of
impairment still need to be addressed by TMDLs. EPA believes that
continued development of TMDLs pursuant to State TMDL development
schedules is the highest priority at this time. If already existing
TMDLs need to be revised in the future, revision of the TMDLs and
allocations should be consistent with the recommendations in this
memorandum.

For TMDLs under development that have not yet been adopted by States or
established by EPA, EPA recommends that such TMDLs and allocations be
revised, if feasible, to be consistent with this memorandum prior to
their adoption or establishment. If States adopt and submit TMDLs
expressed solely in non-daily terms, EPA expects to ask the submitting
State to provide written documentation regarding how the submitted TMDLs
and allocations would be expressed in daily terms. Such documentation
provided by States could then be included in the administrative records
supporting EPA\'s decisions on the TMDLs. If it is unable to obtain such
documentation from a State, EPA may develop calculations for its
administrative approval record demonstrating how the State\'s TMDLs and
allocations would be expressed in daily terms. In this case, EPA would
make it clear that its approval of the State\'s TMDL is contingent on
the assumption that such TMDL contains the daily load calculations
developed by EPA.

We recommend that States consult with EPA regarding specific TMDL
projects early in the development process to determine appropriate
approaches to expressing the TMDLs and allocations. We are working to
provide technical support as soon as practicable. First, we will be
providing a draft of a technical document outlining an approach for
deriving daily limits for bacteria, TSS, sediments and nutrients using
the load duration curve approach. In addition, we are preparing a series
of technical fact sheets and case studies based on typical averaging
periods of criteria, types of water body and types of sources, to
provide technical support in developing daily loads for all pollutants.
These should be available for review and comment within the next few
months.

Implications of the Friends of the Earth Decision for NPDES Permits

The Friends of the Earth decision does not affect an NPDES permitting
authority\'s ability to use the discretion available to it under the CWA
and the NPDES regulations in establishing permit effluent limits and
conditions.

There is no express or implied statutory requirement that effluent
limitations in NPDES permits necessarily be expressed in daily terms.
The CWA definition of \"effluent limitation\" is quite broad (\"effluent
limitation\" is \"any restriction \... on quantities, rates, and
concentrations of chemical, physical, biological, and other constituents
which are discharged from point sources \...\"). See CWA 502(11). Unlike
the CWA\'s definition of TMDL, the CWA definition of \"effluent
limitation\" does not contain a \"daily\" temporal restriction. Indeed,
the central statutory requirement for water-quality based effluent
limits in NPDES permits is that they implement applicable water quality
standards. See CWA 301(b) (1) (C). Such water quality standards will
include water quality criteria for various pollutant parameters that are
expressed in terms of differing temporal periods of duration, including
hourly, daily, weekly, monthly, seasonal, and annual, as appropriate for
each pollutant parameter.

2 Section 2.l of EPA\'s Technical Support Document for Water
Quality-based Toxics Control (TSD) dated March 1991, describes the basis
for establishing water quality criteria. EPA\'s recommended water
quality criteria consist of three components: (1) magnitude, (2)
duration, and (3) frequency. Magnitude refers to the concentration of
the pollutant. Duration is the period of time (averaging period) over
which the in-water concentration is averaged for comparison with
criteria concentrations. This specification limits the length of time
that in-water concentrations may exceed the criteria concentrations.
Frequency is how often the criteria can be exceeded.

2 Accordingly, effluent limits in NPDES permits may be written in a form
that derives from, and complies with, applicable water quality standards
that use any of these various time measures. See 122.44(d)(1)(vii)(A).

EPA\'s regulations at 40 C.F.R. 122.44(d)(1)(vii) require the permitting
authority to ensure that: (a) the level of water quality to be achieved
by limits on point sources is derived from, and complies with, all
applicable water quality standards; and (b) effluent limitations
developed to protect a narrative water quality criterion, a numeric
water quality criterion, or both, are consistent with the assumptions
and requirements of any available wasteload allocation for the discharge
prepared by the State and approved by EPA pursuant to 40 C.F.R. 130.7 .
This provision does not require that effluent limits in NPDES permits be
expressed in a form that is identical to the form in which an available
wasteload allocation for the discharge is expressed in a TMDL. Rather,
permit limits need only be \"consistent with the assumptions and
requirements\" of a TMDL\'s wasteload allocation.

3 EPA\'s position on this issue was affirmed by the Environmental
Appeals Board in In re: City of Moscow, Idaho , 10 E.A.D. 135, 148 (July
27, 2001) (\"While the governing regulations require consistency, they
do not require that the permit limitations that will finally be adopted
in a final NPDES permit be identical to any of the WLAs that may be
provided in a TMDL.\")

3 To facilitate implementation of the TMDL, one of the stated
\"assumptions\" of a TMDL\'s daily load or daily wasteload allocation
might be that, for purposes of NPDES implementation in an appropriate
context (e.g., storm water), the permit writer has the flexibility to
express the permit\'s effluent limitation using a time frame in keeping
with, and appropriate to, the water body and pollutant in question and
the applicable water quality standard. Indeed, the TMDL submission might
even include such alternate temporal expressions of the total load or
the wasteload allocation as implementation assumptions.

The Friends of the Earth decision does not affect the NPDES permitting
authority\'s ability to use all available tools to translate TMDLs and
their wasteload allocations into enforceable effluent limitations in
discharge permits. For example, while the NPDES permitting regulations
require \"daily maximum\" limits for continuous discharges from some
point sources, the same regulations specifically authorize \"average
weekly\" and \"average monthly\" limitations\--rather than daily
limitations\--for discharges from publicly owned water treatment plants.
See 40 C.F.R. 122.45(d) . Moreover, the regulations further authorize
the permit writer to use other unspecified units of time if it is
impracticable to calculate daily, weekly or monthly limitations. Id .
For non-continuous discharges, the regulations provide flexibility as to
the manner in which such discharges are to be limited based on a
consideration of factors, including frequency, total mass, maximum rate
of discharge of pollutants and prohibition or limitation of specified
pollutants by mass, concentration or other appropriate measure. See 40
C.F.R. 122.45(e) .

NPDES permit regulations do not require that effluent limits in permits
be expressed as maximum daily limits or even as numeric limitations in
all circumstances, and such discretion exists regardless of the time
increment chosen to express the TMDL. Therefore, expressing a TMDL as a
daily load does not interfere with a permit writer\'s authority under
the regulations to translate that daily load into the appropriate permit
limitation, which in turn could be expressed as an hourly, weekly,
monthly or other measure.

EPA will continue to use existing guidance and policy memoranda to guide
the development of WQBELs that are consistent with both 40 CFR
122.44(d)(1)(vii) and 40 CFR 122.45(d) . These include: the Technical
Support Document for Water Quality-based Toxics Control (TSD) dated
March 1991, an EPA Memorandum titled Establishing Total Maximum Daily
Load (TMDL) Wasteload Allocations (WLAs) for Storm Water Sources and
NPDES Permit Requirements Based on Those WLAs dated November 22, 2002,
and a memorandum titled Annual Permit Limits for Nitrogen and Phosphorus
for Permits Designed to Protect Chesapeake Bay and its tidal tributaries
from Excess Nutrient Loading under the National Pollutant Discharge
Elimination System dated March 3, 2004.

Recommendation Concerning NPDES Permits

EPA recommends that NPDES permitting authorities continue to establish
effluent limits that implement wasteload allocations established in
approved TMDLs in accordance with existing regulation, policy and
guidance as described above.

cc: Ephraim King Steve Neugeboren Suzanne Schwartz James Hanlon