According to 40 CFR 131.13, States
may, at their discretion, include in their State standards, policies generally
affecting their application and implementation, such as mixing zones, low flows
and variances. Such policies are subject to U.S. EPA review and approval. If
the State adopts a policy applicable only to Surface Waters of the State that
are not also Waters of the United States, such policy is not subject to U.S.
EPA review and approval.
A.
Natural Conditions: Natural conditions are defined as
background water quality conditions due only to non-anthropogenic sources. The
criteria herein apply specifically with regard to substances attributed to
sources (permitted discharges, nonpoint sources, or in-stream activities) as
opposed to natural phenomena. Some waterbodies may have characteristics that
are naturally outside the limits established herein. Therefore, naturally
occurring conditions that preclude attainment of these criteria should not be
interpreted as violations of the criteria.
B.
Applicable Flow:
All criteria contained herein shall apply to all stages of stream flow greater
than or equal to the 7-day, 10-year minimum flow (7Q10) in unregulated, natural
streams, and the legally guaranteed minimum flow in regulated streams, unless
otherwise provided in these regulations. This requirement shall not be
interpreted to permit any unusual waste discharges during periods of lower
flow.
Notwithstanding the above, a stream flow equal to the 7-day,
2-year minimum flow (7Q2) in unregulated, natural streams shall be utilized in
establishing permit limitations for stormwater permits. In cases in which
either (1) the data are indefinite or inconclusive, or (2) the 7-day, 2-year
minimum flow and/or the 7-day, 10-year minimum flow are inappropriate because
of the hydrology of the area, other appropriate State and federal agencies will
be consulted in order to establishing the appropriate and applicable stream
flow.
C.
Mixing
Zones: It is recognized that limited areas of mixing are sometimes
unavoidable; however, mixing zones shall not be used as a substitute for waste
treatment. Mixing zones constitute an area whereby physical mixing of a
wastewater effluent with a receiving waterbody occurs. Application of mixing
zones shall be made on a case-by-case basis and shall only occur in cases
involving large surface waterbodies in which a long distance or large area is
required for the wastewater to completely mix with the receiving waterbody.
The location of a mixing zone shall not significantly alter
the designated uses of the receiving water outside its established boundary.
Adequate zones of passage for the migration and free movement of fish and other
aquatic biota shall be maintained. Toxicity and human health concerns within
the mixing zone shall be addressed as specified in the U.S. EPA
Technical Support Document for Water Quality-Based Toxics
Control (U.S. EPA-505/2-90-001, March 1991) and amendments thereof.
Under no circumstances shall mixing zones overlap or cover tributaries, nursery
locations, locations of threatened or endangered species, or other ecologically
sensitive areas.
D.
Schedules of Compliance:
When appropriate, the State, UIC, or NPDES permit issued by
the Permit Board pursuant to Rule
1.1.3.H may contain a schedule of
compliance leading to compliance with the Federal Water Pollution Control Act
and the Mississippi Air and Water Pollution Control Law. Additional information
and requirements regarding schedules of compliance can be found within 11 Miss.
Admin. Code Pt. 6, R.
1.1.4.A(9).
E. Water Quality Standards Variances:
As defined in
40
CFR 131.3(o), a water
quality standards variance is a time-limited designated use and criterion for a
specific pollutant(s) or water quality parameter(s) that reflect the highest
attainable condition during the term of the variance. A water quality standards
variance must meet certain provisions according to
40 CFR
131.14 and must meet certain
public participation requirements within
40 CFR
131.20(b). A WQS variance is
a water quality standard subject to U.S. EPA review and approval or
disapproval. MDEQ will apply the same provisions of
40 C.F.R. §
131.14 in considering a WQS variance for
State waters that do not meet the definition of Waters of the United States and
will use the same public participation requirements within § 131.20(b) for such
waters. A WQS variance to Surface Waters of the State which do not meet the
definition of "Waters of the United States" will not be subject to U.S. EPA
review and approval or disapproval.
(1) Applicability:
(a) A WQS variance may be adopted for a
permittee(s) or waterbody/waterbody segment(s), but only applies to the
permittee(s) or waterbody/waterbody segment(s) specified in the WQS
variance.
(b) Where the State
adopts a WQS variance, the State must retain, in its standards, the underlying
designated use and criterion addressed by the WQS variance, unless the State
adopts and U.S. EPA approves a revision to the underlying designated use and
criterion consistent with
40 CFR
131.10
and
131.11. All other
applicable standards not specifically addressed by the WQS variance remain
applicable. U.S. EPA approval is not required for State waters that are not
waters of the United States.
(c) A
WQS variance, once adopted by the State and approved by U.S. EPA, shall be the
applicable standard for purposes of the Clean Water Act under
40 CFR
131.21(d) through (e), for
the following limited purposes. An approved WQS variance applies for the
purposes of developing NPDES permit limits and requirements under 301(b)(1)(C),
where appropriate, consistent with paragraph (1)(a) of this section. States and
other certifying entities may also use an approved WQS variance when issuing
certifications under section 401 of the Clean Water Act. U.S. EPA approval is
not required for Surface Waters of the State that are not Waters of the United
States.
(d) The State may not adopt
WQS variances if the designated use and criterion addressed by the WQS variance
can be achieved by implementing technology-based effluent limits required under
sections 301(b) and 306 of the Clean Water Act.
(2) Requirements for Submission to the
Commission and/or to U.S EPA:
(a) A WQS
variance must include:
(i) Identification of
the pollutant(s) or water quality parameter(s), and the waterbody or waterbody
segment(s) to which the WQS variance applies. Discharger(s)-specific WQS
variances must also identify the permittee(s) subject to the WQS
variance.
(ii) The requirements
that apply throughout the term of the WQS variance. The requirements shall
represent the highest attainable condition of the waterbody or waterbody
segment applicable throughout the term of the WQS variance based on the
documentation required in (2)(b) of this section. The requirements shall not
result in any lowering of the currently attained ambient water quality, unless
a WQS variance is necessary for restoration activities, consistent with
paragraph (2)(b)(i)(1) of this section. The State must specify the highest
attainable condition of the waterbody or waterbody segment as a quantifiable
expression that is one of the following:
(1)
For discharger(s)-specific WQS variances:
The highest attainable interim criterion; or
The interim effluent condition that reflects the greatest
pollutant reduction achievable; or
If no additional feasible pollutant control technology can be
identified, the interim criterion or interim effluent condition that reflects
the greatest pollutant reduction achievable with the pollutant control
technologies installed at the time the State adopts the WQS variance, and the
adoption and implementation of a pollutant minimization program.
(2) For WQS variances applicable
to a waterbody or waterbody segment:
The highest attainable interim use and interim criterion;
or
If no additional feasible pollutant control technology can be
identified, the interim use and interim criterion that reflect the greatest
pollutant reduction achievable with the pollutant control technologies
installed at the time the State adopts the WQS variance, and the adoption and
implementation of a pollutant minimization program.
(iii) A statement providing that
the requirements of the WQS variance are either the highest attainable
condition identified at the time of the adoption of the WQS variance, or the
highest attainable condition later identified during any re-evaluation
consistent with paragraph (2)(a)(v) of this section, whichever is more
stringent.
(iv) The term of the WQS
variance, expressed as an interval of time from the date of Commission and/or
U.S. EPA approval or a specific date. The term of the WQS variance must only be
as long as necessary to achieve the highest attainable condition and consistent
with the demonstration provided in paragraph (2)(b) of this section. The State
may adopt a subsequent WQS variance consistent with this section.
(v) For a WQS variance with a term greater
than five years, a specified frequency to re-evaluate the highest attainable
condition using all existing and readily available information and a provision
specifying how the State intends to obtain public input on the re-evaluation.
Such re-evaluations must occur no less frequently than every five years after
Commission and/or U.S. EPA approval of the WQS variance and the results of such
re-evaluation must be submitted to the Commission and/or U.S EPA within 30 days
of completion of the re-evaluation.
(vi) A provision that the WQS variance will
no longer be the applicable water quality standard for purposes of the Clean
Water Act if the State does not conduct a re-evaluation consistent with the
frequency specified in the WQS variance or the results are not submitted to the
Commission and/or U.S. EPA as required by (2)(a)(v) of this section.
(b) The supporting documentation
must include:
(i) Documentation demonstrating
the need for a WQS variance.
(1) For a WQS
variance to a use specified in section 101(a)(2) of the Clean Water Act or a
sub-category of such a use, the State must demonstrate that attaining the
designated use and criterion is not feasible throughout the term of the WQS
variance because:
One of the factors listed in
40 CFR
131.10(g) is met, or
Actions necessary to facilitate lake, wetland, or stream
restoration through dam removal or other significant reconfiguration activities
preclude attainment of the designated use and criterion while the actions are
being implemented.
(2) For
a WQS variance to a non-101(a)(2) use, the State must submit documentation
justifying how its consideration of the use and value of the water for those
uses listed in
40 CFR
131.10(a) appropriately
supports the WQS variance and term. A demonstration consistent with paragraph
(2)(b)(i)(1) of this section may be used to satisfy this requirement.
(ii) Documentation demonstrating
that the term of the WQS variance is only as long as necessary to achieve the
highest attainable condition. Such documentation must justify the term of the
WQS variance by describing the pollutant control activities to achieve the
highest attainable condition, including those activities identified through a
Pollutant Minimization Program, which serve as milestones for the WQS
variance.
(iii) In addition, for a
WQS variance that applies to a waterbody or waterbody segment:
Identification and documentation of any cost-effective and
reasonable best management practices for nonpoint source controls related to
the pollutant(s) or water quality parameter(s) and waterbody or waterbody
segment(s) specified in the WQS variance that could be implemented to make
progress towards attaining the underlying designated use and criterion. The
State must provide public notice and comment for any such documentation.
Any subsequent WQS variance for a waterbody or waterbody
segment must include documentation of whether and to what extent best
management practices for nonpoint source controls were implemented to address
the pollutant(s) or water quality parameter(s) subject to the WQS variance and
the water quality progress achieved.
(3) Implementing WQS variances in NPDES
permits.
A WQS variance serves as the applicable water quality
standard for implementing NPDES permitting requirements for the term of the WQS
variance. Any limitations and requirements necessary to implement the WQS
variance shall be included as enforceable conditions of the NPDES permit for
the permittee(s) subject to the WQS variance.
F. Designation of Uses and Use Attainability
Analyses:
(1)
According to
40 CFR
131.10(a), the
Commission will specify appropriate water uses to be achieved and protected.
The classification of Surface Waters of the State must take into consideration
the use and value of water for public water supplies, protection and
propagation of fish, shellfish and wildlife, recreation in and on the water,
agricultural, industrial, and other purposes including navigation. If adopting
new or revised designated uses other than the uses specified in section
101(a)(2) of the Clean Water Act, or removing designated uses, the State must
submit documentation justifying how its consideration of the use and value of
water for those uses listed in this paragraph appropriately supports the
State's action. A use attainability analysis may be used to satisfy this
requirement. In no case shall the State adopt waste transport or waste
assimilation as a designated use. The State shall also re-examine any waterbody
segment with water quality standards that do not include the uses specified in
section 101(a)(2) of the Clean Water Act every 3 years to determine if any new
information has become available. If such new information indicates that the
uses specified in section 101(a)(2) of the Clean Water Act are attainable, the
State shall revise its standards accordingly.
(2) In designating uses of a waterbody and
the appropriate criteria for those uses, the State shall take into
consideration the water quality standards of downstream waters and shall ensure
that its water quality standards provide for the attainment and maintenance of
the water quality standards of downstream waters.
(3) The State may adopt sub-categories of a
use and set the appropriate criteria to reflect varying needs of such
sub-categories of uses, for instance, to differentiate between cold water and
warm water fisheries.
(4) At a
minimum, uses are deemed attainable if they can be achieved by the imposition
of effluent limits required under sections 301(b) and 306 of the Clean Water
Act and costeffective and reasonable best management practices for nonpoint
source control.
(5) The State may
adopt seasonal uses as an alternative to reclassifying a waterbody or segment
thereof to uses requiring less stringent water quality criteria. If seasonal
uses are adopted, water quality criteria should be adjusted to reflect the
seasonal uses, however, such criteria shall not preclude the attainment and
maintenance of a more protective use in another season.
(6) The State may designate a use, or remove
a use that is
not an existing use, if the State conducts a use
attainability analysis that demonstrates attaining the use is not feasible
because of one of the six factors in this paragraph. If the State adopts a new
or revised water quality standard based on a required use attainability
analysis, the State shall also adopt the highest attainable use.
(a) Naturally occurring pollutant
concentrations prevent the attainment of the use; or
(b) Natural, ephemeral, intermittent or low
flow conditions or water levels prevent the attainment of the use, unless these
conditions may be compensated for by the discharge of sufficient volume of
effluent discharges without violating State water conservation requirements to
enable uses to be met; or
(c) Human
caused conditions or sources of pollution prevent the attainment of the use and
cannot be remedied or would cause more environmental damage to correct than to
leave in place; or
(d) Dams,
diversions or other types of hydrologic modifications preclude the attainment
of the use, and it is not feasible to restore the waterbody to its original
condition or to operate such modification in a way that would result in the
attainment of the use; or
(e)
Physical conditions related to the natural features of the waterbody, such as
the lack of a proper substrate, cover, flow, depth, pools, riffles, and the
like, unrelated to water quality, preclude attainment of aquatic life
protection uses; or
(f) Controls
more stringent than those required by sections 301(b) and 306 of the Clean
Water Act would result in substantial and widespread economic and social
impact.
(7) The State
may not remove designated uses if:
(a) They
are existing uses, as defined in
40
CFR
131.3, unless a use requiring more
stringent criteria is added; or
(b)
Such uses will be attained by implementing effluent limits required under
sections 301(b) and 306 of the Clean Water Act and by implementing
cost-effective and reasonable best management practices for nonpoint source
control.
(8) Where
existing water quality standards specify designated uses less than those which
are presently being attained, the State shall revise its standards to reflect
the uses actually being attained.
(9) The State must conduct a use
attainability analysis as described in
40
CFR
131.3(g), and paragraph
(F)(5) of this section, whenever:
(a) The
State designates for the first time, or has previously designated for a
waterbody, uses that do not include the uses specified in section 101(a)(2) of
the Clean Water Act; or
(b) The
State wishes to remove a designated use that is specified in section 101(a)(2)
of the Clean Water Act, to remove a sub-category of such a use, or to designate
a sub-category of such a use that requires criteria less stringent than
previously applicable.
(10) The State is not required to conduct a
use attainability analysis whenever:
(a) The
State designates for the first time, or has previously designated for a
waterbody, uses that include the uses specified in section 101(a)(2) of the
Clean Water Act; or
(b) The State
designates a sub-category of a use specified in section 101(a)(2) of the Clean
Water Act that requires criteria at least as stringent as previously
applicable; or
(c) The State wishes
to remove or revise a designated use that is a non-101(a)(2) use.
In this instance, as required by paragraph (1) of this
section, the State must submit documentation justifying how its consideration
of the use and value of water for those uses listed in paragraph (1)
appropriately supports the State's action, which may be satisfied through a use
attainability analysis.
