Subpart 1.
Applicability.
The provisions in this subpart apply to establishing total
maximum daily loads (TMDLs) for all Great Lakes Initiative (GLI) pollutants and
pollutant parameters in surface waters of the state in the Lake Superior Basin,
with the exception of whole effluent toxicity (WET), which is addressed in part
7052.0240.
A. TMDLs must be established in accordance
with the listing and priority-setting process provided by section 303(d) of the
Clean Water Act, United States Code, title 33, section 1313(d) and Code of
Federal Regulations, title 40, section 130.7. Where water quality standards are
not immediately attainable, TMDLs must assure that water quality standards will
be attained in a reasonable period of time. Some TMDLs may be based on
attaining water quality standards over a period of time, with specific controls
on individual sources being implemented in stages. Determining the reasonable
period of time in which water quality standards will be met is a case-specific
determination based on the following factors:
(1) receiving water
characteristics;
(2) persistence,
behavior, and ubiquity of GLI pollutants of concern;
(3) type of remediation activities
necessary;
(4) available regulatory
and nonregulatory controls;
(5)
individual agency requirements for attainment of water quality standards;
and
(6) technical and economic
feasibility of attainment.
B. TMDLs must include the following elements,
the sum of which must not exceed the
loading capacity of the water for the GLI
pollutants addressed by the TMDLs:
(1) waste
load allocations (WLAs) for point sources;
(2) load allocations (LAs) for nonpoint
sources including natural background sources; and
(3) a margin of safety (MOS), which includes
a portion reserved for future growth.
C. If the agency develops an assessment and
remediation plan that meets the provisions of this part, meets the public
participation provisions of subpart
6, and has been approved by
the
EPA as meeting the requirements under Code of Federal Regulations, title
40, section 130.6, then the assessment and remediation plan may be used in lieu
of a
TMDL if one of the following conditions is met:
(1) the agency determines that the assessment
and remediation plan will result in attainment of water quality standards in a
reasonable period of time as defined in item A;
(2) concurrent pollutant reductions will
result from an assessment and remediation plan used in lieu of a TMDL;
or
(3) implementation costs will be
reduced if an assessment and remediation plan is used in lieu of a
TMDL.
Assessment and remediation plans include lakewide management
plans, remedial action plans, and state water quality management plans.
Any part of an assessment and remediation plan that also
satisfies one or more requirements in section 303(d) of the Clean Water Act,
United States Code, title 33, section 1313(d), or implementing regulations may
be incorporated by reference into a TMDL as appropriate. Assessment and
remediation plans must be tailored to the level of detail and magnitude
appropriate for the watershed and GLI pollutant being assessed.
Subp. 2.
Determination of TMDL allocations.
The agency must determine TMDL allocations as described in
this subpart.
A. The sum of the WLAs
for point sources is the portion of the loading capacity not assigned to
nonpoint sources, including background, or to a MOS. Methods to apportion WLAs
are identified in Table 4-1 of the EPA Technical Support Document for Water
Quality-Based Toxics Control (EPA-505-2-90-001, March 1991), which is adopted
and incorporated by reference in part
7052.0015, item E.
B. LAs for nonpoint sources, including
natural background, must be based on:
(1)
existing GLI pollutant loadings if changes in loadings are not anticipated to
occur;
(2) increases in GLI
pollutant loadings that are anticipated to occur; or
(3) decreases in GLI pollutant loadings if
such decreased loadings are technically feasible and are anticipated to occur
within a reasonable time period as a result of implementation of best
management practices or other load reduction measures, considering the
technical and institutional factors involved.
C. The MOS must account for technical
uncertainties in establishing the TMDL and must describe the manner in which
the MOS is determined and incorporated into the TMDL. The MOS may be provided
by leaving a portion of the loading capacity unallocated or by using
conservative modeling assumptions to establish WLAs and LAs. If a portion of
the loading is left unallocated to provide a MOS, the amount left unallocated
must be described. If conservative modeling assumptions are relied on to
provide a MOS, the specific assumptions providing the MOS must be
identified.
D. The representative
background concentration for a GLI pollutant in the specified watershed,
waterbody, or water segment must be established on a case-by-case basis as the
geometric mean of water column data, water column concentrations estimated
through the use of available caged or resident fish tissue data, or water
column concentrations estimated through the use of existing or projected GLI
pollutant loading data. Commonly accepted statistical techniques must be used
to evaluate data sets consisting of values both above and below the detection
level. If all of the available data in a data set are below the detection level
for a GLI pollutant, then all the data in the data set must be assumed to be
zero.
E. Where sufficient data are
available to quantify the transport of GLI pollutants to sediments, TMDLs must
account for and prevent such accumulations that preclude attainment of
specified designated uses.
F. Where
sufficient data are available to quantify loadings of GLI pollutants resulting
from wet weather events, TMDLs must account for these loadings.
G. The maximum allowable loading consistent
with the attainment of each standard or criterion of a given GLI pollutant is
determined by multiplying the applicable standard or criterion by the stream
design flow at the farthest downstream location in the tributary watershed. The
loading is then compared to the loadings at discharge sites within the
watershed to assure that standards or criteria for a given GLI pollutant are
not exceeded. The lowest load is then selected as the loading
capacity.
H. TMDLs and WLAs in the
absence of a
TMDL must be based on the assumption that a
GLI pollutant does not
degrade unless both of the following occur:
(1) field studies or other information
demonstrate that degradation of the GLI pollutant is expected to occur under
the full range of environmental conditions expected to be encountered;
and
(2) field studies or other
information address other factors that affect the level of GLI pollutants in
the water column including sediment resuspension, chemical separation, and
biological and chemical transformation.
I. If the agency establishes separate TMDLs
for different segments of the same watershed, and if each of these separate
TMDLs includes WLAs for the same GLI pollutant for one or more of the same
point sources, then water quality-based effluent limits (WQBELs) for the GLI
pollutant and point sources must be consistent with the most stringent of those
WLAs to assure attainment of all applicable water quality standards and
criteria.
Subp. 3.
Waste load allocations for GLI pollutants in the absence of a
TMDL.
For purposes of determining WLAs in the absence of a TMDL or
for determining the need for WQBELs, calculations must be made using the
methods in items A to C.
A. The agency
must develop acute and chronic WLAs for streams and rivers for each applicable
aquatic life, human health, and wildlife standard and
criterion using dynamic
models found in chapter 4 of the
EPA Technical Support Document for Water
Quality-Based Toxics Control (
EPA-505-2-90-001, March 1991), which is adopted
and incorporated by reference in part
7052.0015, item E, or using the
following equation:
|
WLA = (Qd + Qr)(Cs) - (Qr)(Cb) _____ |
|
|
(Qd) |
|
Where:
| Cs |
= |
Water quality standard or criterion developed for the GLI
pollutant in question |
| Qr |
= |
Stream design flows for steady state models, including
corresponding acute or chronic mixing zone allowances determined in part
7052.0210 |
|
|
Applicable flows are: |
|
|
(1) the 1-day, 10-year stream design flow (1Q10) for
a maximum standard or criterion; |
|
|
(2) the 7-day, 10-year stream design flow (7Q10), or
the 4-day, 3-year biologically based stream design flow for an aquatic life
chronic standard or criterion; |
|
|
(3) the 90-day, 10-year flow (90Q10) for a wildlife
chronic standard or criterion; and |
|
|
(4) the harmonic mean for the human health chronic
standard or criterion. |
|
|
Where a discharger has an intake upstream of the
point of discharge, but downstream of the stream location used to determine Qr,
the value of Qr must be reduced by that flow volume. |
| Qd |
= |
Effluent design flow
|
| Cb |
= |
Background receiving water concentration of the GLI
pollutant calculated according to subpart
2, item D. |
B.
For lakes, WLAs based on acute aquatic life standards or criteria must not
exceed the
FAV unless a mixing zone demonstration is conducted and approved
under part
7052.0210. The agency must develop
chronic WLAs for lakes for each applicable aquatic life, human health, and
wildlife standard and
criterion using the following equation:
WLA = (Cs)(X) - (Cb)(X)
Where:
| Cs |
= |
Water quality standard or criterion developed for the GLI
pollutant in question |
| Cb |
= |
Background receiving water concentration of the GLI
pollutant calculated according to subpart
2, item D |
| X |
= |
10, which represents a receiving water volume to effluent
volume dilution ratio of 10 to 1, unless an alternative mixing zone
demonstration is provided under part
7052.0210, subpart
2, that includes a dilution
ratio other than 10 to 1 and results in a mixing zone that is no greater than
the area of discharge-induced mixing, in which case X equals the dilution ratio
established in the demonstration. |
C.
Where the background receiving water concentration (Cb) of a GLI pollutant
exceeds the most stringent applicable water quality standard listed or
referenced for that pollutant in part
7052.0100, or criterion for that
pollutant developed under part
7052.0110, the intake credit
provisions of part
7052.0220, subpart
5, apply.
Subp. 4.
Translating
dissolved metal standards to total recoverable WQBELs for metals.
For purposes of expressing dissolved metals standards and
criteria as total recoverable WQBELs, the methods in items A to C must be
used.
A. WLAs determined in subpart
3 must be calculated using
dissolved metal standards. Dissolved metal standards are determined by
multiplying the total metal standards, listed in part
7052.0100, by the corresponding
conversion factors listed in part
7050.0360. For metals not listed
in part
7050.0360, the conversion factor
is 1.0. Subsequent calculation of WQBELs requires the translation of the
dissolved metal WLAs to total recoverable metal WLAs as described in items B
and C.
B. In the absence of
site-specific data, the dissolved metal WLAs are translated to total metal WLAs
by dividing the dissolved metal WLAs by the corresponding conversion factors in
part
7050.0360.
C. The agency must use a total metal
translator based upon the collection of site-specific data if an existing or
proposed discharger submits a request to the agency and the request is
accompanied by a completed site-specific study conducted in accordance with the
EPA guidance "The Metals Translator: Guidance for Calculating a Total
Recoverable Permit Limit From a Dissolved
Criterion" (
EPA-823-B-96-007, June
1996), which is adopted and incorporated by reference under part
7052.0015, item F.
Upon receiving a study that the agency determines has
conformed with the metals translator guidance, the agency must use the
site-specific translator to convert the dissolved metal WLA into a total
recoverable WLA, if the antidegradation provisions under parts
7052.0300 to
7052.0330 and antibacksliding
provisions of section 402(o) of the Clean Water Act, United States Code, title
33, section 1342(o), are complied with. Subsequent WQBELs must be calculated
from the total recoverable WLA.
Subp. 5.
Calculating effluent
limitations from WLAs.
The agency must determine WLAs, including applicable mixing
zone determinations from part
7052.0210, for aquatic life, human
health, and wildlife water quality standards and criteria using the methods in
subparts
2 and
3. WQBELs are calculated from
these WLAs, or by using dynamic models based on methods in chapter 5 of the EPA
Technical Support Document for Water Quality-Based Toxics Control
(EPA-505-2-90-001, March 1991), which is adopted and incorporated by reference
in part
7052.0015, item E. The agency must
use the methods in items A to G to calculate WQBELs from the WLAs developed
under subparts
2 and
3.
A. Assume the effluent concentrations are
lognormally distributed and dominate in-stream concentrations and variability
after mixing.
B. Characterize the
variability of the effluent data by calculating the coefficient of variation
(CV), which is the ratio of the standard deviation divided by the mean, using a
99th percentile probability basis (z99 =
2.326).
C. Calculate the
long-term
average (LTA) for each applicable
WLA determined under subpart
2 or
3 as follows:
(1) calculate the
maximum standard LTA
(LTA
ms) protective of acute aquatic life effects as follows:
LTAms = exp(0.5[sigma]2
- z99[sigma]) . WLAms
Where:
[sigma]
2 = ln(CV2
+ 1)
WLAms = the maximum standard WLA
The WLAms is determined under subpart
2 or
3 and is expressed as a
one-day maximum;
(2)
calculate the chronic standards LTA (LTA
cs) protective of chronic
aquatic life effects as follows:
LTAcs =
exp(0.5[sigma]42 -
z99[sigma]4) .
WLAcs
Where:
[sigma] 42
= ln((CV2/4) + 1)
WLAcs = the chronic standard WLA
The WLAcs is determined under subpart
2 or
3 and is expressed as a
four-day average; and
(3)
calculate the LTA
cs protective of chronic human health or wildlife
effects as follows:
LTAcs =
exp(0.5[sigma]302 -
z99[sigma]30) .
WLAcs
Where:
[sigma] 302
= ln((CV2/30) + 1)
The WLAcs is determined under subpart
2 or
3 and is expressed as a
30-day average.
D. Calculate the daily maximum and monthly
average WQBELs using the lowest determined LTA calculated in item C as follows:
(1) calculate the daily maximum WQBEL as
follows:
Daily maximum = exp(z99[sigma] -
0.5[sigma]2) . LTA
Where:
[sigma]
2 = ln(CV2
+ 1); and
(2) calculate the
monthly average WQBEL as follows:
Monthly average =
exp(z95[sigma]n -
0.5[sigma]n2) . LTA
Where:
[sigma] n2
= ln((CV2/n) + 1)
z95 = 1.645 (95th percentile
probability basis)
n = number of samples per month.
E. Establish the most stringent daily maximum
WQBEL from item D or the FAV applied under part
7050.0210, subpart
5; 7050.0211, subpart
1; 7050.0212, subpart
6; 7050.0214, subpart
1; 7052.0210, subpart
1; or 7052.0230, subpart
4, as the daily maximum
effluent limitation in the permit. When the applicable daily maximum WQBEL
determined from item D is established in the permit, the corresponding monthly
average WQBEL must also be established in the permit. When the FAV is
established in the permit as the daily maximum effluent limitation, no monthly
average effluent limitation is established in the permit.
F. For distributions other than lognormal:
(1) apply the most stringent
WLAcs of those determined under subpart
2 or
3 as the monthly average
WQBEL;
(2) apply the more stringent
of the WLAms determined under subpart
2 or
3 or the FAV applied under
part
7050.0210, subpart
5; 7050.0211, subpart
1; 7050.0212, subpart
6; 7050.0214, subpart
1; 7052.0210, subpart
1; or 7052.0230, subpart
4, as the daily maximum
effluent limitation in the permit. When the FAV is as stringent or more
stringent than the effluent limitation based on the WLAcs
determined in subitem (1), no monthly average effluent limitation is
established in the permit.
G. Whenever a WQBEL is developed, it must be
expressed as both a concentration value and a corresponding mass loading rate.
Both mass and concentration limits must be based on the same permit averaging
periods, such as daily or monthly averages. The agency must calculate the mass
loading rates using effluent flow rates that correspond to those used in
establishing the WQBELs expressed in concentration, except if adjustments for
wet weather flows have been accommodated in the WLA process on a case-by-case
basis. If wet weather flows have been accommodated, the agency must calculate
the mass loading rates using the adjusted flows.
Subp. 6.
Solicitation of public input
in development of TMDLs.
The agency must provide the following public notification and
opportunity for comment during the development and implementation of a
TMDL:
A. a public notice and
solicitation of comment on the intent of the agency to develop a TMDL for a GLI
pollutant where the agency has identified impaired water quality
uses;
B. a public notice and
solicitation of information and comments regarding preliminary source
identification and loadings for a GLI pollutant subject to a TMDL;
C. a public notice and solicitation of
comment on proposed source loadings and a proposed TMDL allocation method for a
reduction of loadings for a GLI pollutant subject to a TMDL; and
D. a public notice of an effluent limitation
in a permit for a GLI pollutant subject to a TMDL, pursuant to the public
notice requirements of parts
7001.0100 and
7001.0110.
