The Department shall establish appropriate discharge
prohibitions, effluent limits and monitoring requirements in waste discharge
licenses if a discharge contains pollutants that are or may be discharged at
levels that cause, have reasonable potential to cause, or contribute to an
ambient excursion in excess of a numeric or narrative water quality criteria or
that may impair existing or designated uses. The licensee must also control
whole effluent toxicity (WET) when discharges cause, have a reasonable
potential to cause, or contribute to an ambient excursion above the narrative
water quality criteria. In determining if effluent limits are required, the
Department shall consider all information on file and effluent testing
conducted during the preceding 60 months. However, testing done in the
performance of a Toxicity Reduction Evaluation (TRE) approved by the Department
may be excluded from such evaluations.
A.
Specific pollutant approach.
When specific toxic pollutants of known action and interaction are
identified in a discharge or potential discharge, the water quality-based
effluent limit is determined by use of the applicable numerical water quality
criteria for the pollutants to protect aquatic life and human health and using
the appropriate dilution described in section 4(A) below.
NOTE: See section 4(F) for procedures to address multiple
discharges into a common receiving water.
B.
Whole effluent approach. When
the existing or proposed discharge contains two or more pollutants whose
actions or interactions are unknown or when toxic components cannot be
identified, WET effluent limits may be required for the protection of aquatic
life. Whole effluent toxicity limits are the "acute no observed effect level"
(A-NOEL) and the "chronic no observed effect level" (C-NOEL), expressed as
percent effluent (the mathematical inverse of the applicable dilution factor),
and must be greater than the actual receiving water concentrations (percent of
effluent in receiving water at the appropriate dilution pursuant to section
4(A)).
C.
Determination of
Exceedence of Criteria. The results of all testing required by this rule
must be submitted to the Department not later than the next discharge
monitoring report required by the discharger's license, provided, however, that
the discharger may review the toxicity reports for up to 10 business days of
their availability before submitting them. Using information and guidance
provided by the Department, dischargers shall evaluate test results being
submitted and identify to the Department possible exceedences of applicable
water quality criteria. The Department shall review all testing data as
received. If these data indicate that the discharge is causing an exceedence of
applicable water quality criteria, then: (1) the licensee must, within 45 days
of becoming aware of an exceedence, submit a TRE plan for review and approval
and implement the TRE after Department approval; and (2) the Department must,
within 180 days of the Department's written approval of the TRE plan, modify
the waste discharge license to specify effluent limits and monitoring
requirements necessary to control the level of pollutants and meet receiving
water classification standards. Evaluations of the reasonable potential for
exceedence of criteria must be conducted upon any license action, following the
provisions of section 3(E). The Department shall utilize mass discharge
criteria for evaluating individual exceedences of specific chemical pollutants.
When considering the need for license limits, the Department
may exclude from evaluations tests in a series done for an individual pollutant
or WET test during five years only if the discharger satisfactorily
demonstrates through implementation of a TRE pursuant to this subsection that
the cause(s) for a high result have been identified and corrected.
Additionally, tests subsequent to the high test(s) must not show reasonable
potential for exceedence of water quality criteria. In making these
determinations, the Department shall not exclude tests solely because the
values are higher than other values obtained by the discharger.The Department
shall issue a license limit in situations where an exceedence is recorded due
to a valid test and a cause for the exceedence cannot be identified and
corrected.
D.
Expression of effluent limits. Where the need for effluent limits
has been determined, limits derived from acute water quality criteria must be
expressed as daily maximum values. Limits derived from chronic or human health
criteria must be expressed as monthly average values.
(1) For specific chemicals, effluent limits
must be expressed in total quantity that may be discharged. Unless required by
an applicable effluent limitation guideline adopted by the Department, all
permit limitations for metals shall be expressed only as mass-based limits. If
required, in establishing concentration, the Department may increase allowable
values to reflect actual flows that are lower than permitted flows and/or
provide opportunities for flow reductions and pollution prevention provided
water quality criteria are not exceeded. With regard to concentration limits,
the Department may review past and projected flows and set limits to reflect
proper operation of the treatment facilities that will keep the discharge of
pollutants to the minimum level practicable.
(2) WET test effluent limits must be
expressed as the maximum percent effluent that will not cause observable
adverse effects on test organisms.
E.
Determination of Reasonable
Potential to Exceed Receiving Water Quality Criteria. For effluent
monitoring data and the variability of the pollutant in the effluent,
the Department shall apply the statistical approach in Section 3.3.2 and
Table 3-2 of USEPA's "Technical Support Document for Water Quality-Based Toxics
Control" (USEPA Publication 505/2-90-001, March, 1991, EPA, Office of Water,
Washington, D.C.) to data to determine whether water-quality based effluent
limits must be included in a waste discharge license. Where it is determined
through this approach that a discharge contains pollutants or WET at levels
that have a reasonable potential to cause or contribute to an exceedence of
water quality criteria, appropriate water quality-based limits must be
established in any licensing action.
F.
Procedures for data analysis and
effluent limit calculations
(1) When a
test result for a specific chemical is reported as not found in concentrations
at a detection level specified by the Department pursuant to section 2(C)(6),
the compound must be considered to be not present for the purposes of
determining exceedences of water quality criteria.
NOTE: Concentrations of compounds detected below levels
specified by the Department must still be reported.
(2) When the no observed effect level in a
WET test is reported as being below the lowest dilution of effluent tested, the
effluent is considered to be in exceedence of water quality criteria.
(3) When all results are reported as below a
detection level specified by the Department, the compound must be considered to
have no reasonable potential to exceed water quality criteria. For the purposes
of determining the coefficient of variation in calculating reasonable potential
to exceed water quality criteria pursuant to section 3(E), when some results
are reported as below a detectable amount, those values must be considered to
be present at a level of one half of the detection level specified by the
Department.
(4) Flows used in
calculations are to be governed by the following. For exceedence determinations
with specific chemicals, calculations must be based on the facility's flow on
the day the sample was collected for acute criteria and the monthly average
flow for the chronic and human health criteria. Allowable discharge quantities
must be calculated based on the facility's licensed flow and the appropriate
design stream flow and water quality criteria. In situations where a
discharger's flow augments the stream flow (as is the case with most POTW's),
the Department's calculation of allowable mass limits must reflect the
differences in dilution factors resulting from actual flows being less than the
facility's full license amount. For determination of WET test exceedences and
all reasonable potential determinations, the discharger's licensed flow must be
used.
