(A) In order to provide for the survival and propagation of a balanced community of aquatic flora and fauna as set forth in Regulation 61-68 in a manner consistent with § 48-1-20, the department shall, where necessary to protect aquatic life, impose NPDES permit limitations for whole effluent toxicity (WET) based on the mixing zone authorized in subsection (C), where the department determines that a discharge causes or has the reasonable potential to cause or contribute to an excursion of a water quality criterion in Regulation 61-68, other than numeric criteria for specific pollutants, that apply to the protection of aquatic organisms.

(B) As directed by this section, the department may promulgate regulations to implement WET tests that calibrate EPA’s standard toxicity testing species and methods to the natural water chemistry representative of the lakes, streams, groundwater, and stormwater runoff of this State. In developing these regulations the department may use the findings of any scientifically defensible study it may conduct and may use other pertinent peer reviewed studies or conclusions. In the interim, this section shall not be construed to limit the department’s authority to impose WET limits.

(C) For purposes of performing WET reasonable potential determinations for a specific discharge and, where justified, setting WET permit limitations for that discharge, the department, notwithstanding any other provision of law shall:

(1) develop procedures to allow up to one hundred percent dilution in waterbodies, based on the 7Q10 flow as defined by Regulation 61-68, where justified by the permittee or permit applicant and approved by the department;

(2) use stream flow conditions other than those described in item (1) where justified by hydrological controls that are capable of ensuring critical flow conditions higher than the respective ten-year flows identified in item (1), to evaluate acute and chronic exposure;

(3) use, for stormwater discharges, a representative flow greater than 7Q10 flow, as demonstrated on a site-specific basis, with any resulting WET permit limitations comprising only those expressed in terms of acute survival endpoints;

(4) consider such mixing calculations as described in items (1), (2), and (3) to be consistent with its policy set forth in Regulation 61-68 for minimizing mixing zones;

(5) give consideration to compliance with numeric criteria and actual instream biological conditions, in the absence of a valid scientific correlation between sublethal WET test results and the biological integrity of representative lakes, streams, and estuaries in this State, wherein biological integrity includes the richness, abundance, and balanced community structure of indigenous aquatic organisms;

(6) allow, at the request of the permittee, the use of ambient receiving waters as control and dilution waters in WET tests;

(7) exempt once-through, noncontact cooling water, which contains no additives, from toxicity requirements; and

(8) allow dischargers to use WET testing protocols that utilize alternative species in accordance with applicable EPA regulations and guidance.

(D) No part of this section shall be construed to limit the department’s authority to adopt water quality criteria, to impose permit limits for specific chemical pollutants, to obligate the department to revalidate existing water quality criteria, or to establish additional water quality criteria for specific chemical pollutants. The department, whenever appropriate, shall utilize the flexibility of interpretation concerning WET testing and the use of WET test results provided by EPA.

(E) For the purpose of implementing § 48-1-20 and Regulation 61-68:

(1) "propagation" is defined in Regulation 61-68;

(2) "biological integrity" means a measure of the health of an aquatic or marine ecosystem using the richness and abundance of species as the primary indicator, and "biological integrity" is a key component of an "instream bioassessment";

(3) "sublethal toxicity tests" means laboratory experiments that measure the nonlethal biological effects, including, but not limited to, growth or reproduction, of effluents or receiving waters on aquatic organisms;

(4) "calibrate" means a process to establish the baseline control condition based on the normal range of biological responses likely to occur when standard test organisms are exposed to various nontoxic waters sampled from streams and lakes throughout the State.

(F) For any NPDES permit that was taken over by EPA due to provisions of Act 258 of 2004 from July 1, 2004, through the effective date of this subsection as revised by the provisions of this 2005 act, the department shall convey to EPA, through the certification process (40 C.F.R. part 124.53), any additional requirements mandated under state law. Moreover, notwithstanding any other provision of law or regulation, the requirement for a counterpart state permit for any such discharge is waived. Alternatively, at the request of the permittee, the department may waive the certification process and issue a state permit. However, affected permittees shall submit applications for reissuance to the department in accordance with Regulation 61-9, at least one hundred eighty days in advance of the expiration of the federal permits. At the discretion of the department, the annual fees for NPDES permits in Regulation 61-30 may continue to be charged, when certifying a federal permit, if the department waives the certification fee.

(G) The department shall reduce or eliminate WET monitoring requirements, as appropriate, in accordance with permit modification processes contained in Regulation 61-9, where dischargers demonstrate that their effluents do not demonstrate reasonable potential.