Publication Summary

Chapter 173-205 WAC Whole Effluent Toxicity Testing and Limits became effective on November 6, 1993. The short name for this rule is the whole effluent toxicity (WET) Rule. Chapter I. Whole Effluent Toxicity Testing Regulatory Guidance of this document has been prepared to assist labs in providing toxicity testing services to permittees who must meet the requirements of the WET Rule. The guidance will help provide the regulatory context for WET testing and other services provided by labs. Having an understanding of the purpose of WET testing in Washington State can help labs provide better service to permittees.

On November 6, 1993, a new rule became effective in the state of Washington: Chapter 173-205 WAC Whole Effluent Toxicity Testing and Limits. The short name for this rule is the whole effluent toxicity (WET) Rule. Chapter I. Whole Effluent Toxicity Testing Regulatory Guidance of this document has been prepared to assist labs in providing toxicity testing services to permittees who must meet the requirements of the WET Rule. The guidance will help provide the regulatory context for WET testing and other services provided by labs. Having an understanding of the purpose of WET testing in Washington State can help labs provide better service to permittees.

Chapter II. Whole Effluent Toxicity Test Review of this document has been prepared to assist accredited labs to provide acceptable toxicity tests for permittees who are regulated under the WET Rule. Only WET tests and rapid screening tests from accredited labs can be used to fulfill these requirements.

A National Pollutant Discharge Elimination System (NPDES) permit will describe which requirements of the WET Rule apply to each individual permittee and what specific actions the permittee must take to meet these requirements. An administrative order can also be used to communicate these requirements. This document does not supersede or modify the requirementsof any valid permit unless the permit references an outdated test manual. If this document seems to conflict with the requirements in a permit, it is likely that the permit was written before the WET Rule or this guidance was written. These older permits, including expired permits, are still valid permits. If a lab believes that any permit requirement could be improved by making it more consistent with this document, then the permittee can be advised to contact the Department of Ecology (Ecology) to request a change. (See WAC 173-205-080(1)©.) However, labs should not deviate from the instructions in any valid permit unless the deviation has been approved by Ecology.

All questions concerning this document or the WET testing program should be directed to Randall Marshall, (360) 407-6445, or rmar461@ecy.wa.gov