(1) A discharge from a facility is considered to have a risk for aquatic toxicity and to need an effluent characterization for acute and chronic whole effluent toxicity if the facility or discharge meet any of the following criteria:

(a) Uses, stores, produces as a product or waste, or transfers any hazardous substance listed in 40 C.F.R. 302.4 with a statutory code of 1 or 2 (referring to Sections 311 (b)(4) or 307(a) of the Clean Water Act) unless:

(i) The permittee demonstrates to the department's satisfaction that the facility is designed and managed so that these substances are kept physically separated at all times, including spills or any other accidental release, from any part of the wastewater collection, treatment, or discharge system; or

(ii) The amount of any hazardous substance at the facility is never more than the statutory reportable quantity listed in 40 C.F.R. 302.4;

(b) Discharges in its effluent any toxic pollutant listed in Appendix D of 40 C.F.R. Part 122 for which there are no water quality criteria for aquatic life protection listed in 40 C.F.R. 131.36 (b)(1) or WAC 173-201A-040(3);

(c) Belongs to an industry category identified in 40 C.F.R. Part 122, Appendix A;

(d) Is a municipal sewage collection and treatment system which receives a discharge from any industry category identified in 40 C.F.R. Part 403, Appendix C;

(e) Except for permittees with whole effluent toxicity limits or permittees that have no whole effluent toxicity limit because of the determination in WAC 173-205-120(1), any facility which exceeded the acute or chronic whole effluent toxicity performance standard within the last five years;

(f) Any facility with suspected toxicity because of apparent damage to aquatic biota; or

(g) Any other discharger that the department determines has the potential to discharge toxics in toxic amounts.

(2) The following types of discharges are excluded from requirements for whole effluent toxicity characterization unless subsection (1) of this section applies:

(a) Once-through noncontact cooling water without biocides;

(b) Drinking water treatment plant effluent;

(c) Dewatering of sand or gravel mining operations;

(d) Sump pump discharges of groundwater or rain water only;

(e) Construction dewatering;

(f) Discharges from fish hatcheries and other aquaculture;

(g) Seafood processors; or

(h) Any other discharge that the department determines does not have the potential to contain toxics in toxic amounts.

(3) A chronic whole effluent toxicity characterization is not necessary in any permit if the effluent has been or will be characterized for acute whole effluent toxicity and if the discharge receives at least one thousand to one dilution at the edge of a mixing zone assigned in accordance with WAC 173-201A-100.