Code of Maine Rules › 06 - DEPARTMENT OF ENVIRONMENTAL PROTECTION › 096 - DEPARTMENT OF ENVIRONMENTAL PROTECTION - GENERAL › Chapter 530 - SURFACE WATERS TOXICS CONTROL PROGRAM › Section 096-530-3 - Water Quality-based Effluent Limits for Waste Discharge Licenses

Current through 2024-29, July 17, 2024
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.