Permit Writer’s Manual: Water Effect Ratio (WER) Determination Guidelines

Notes

This document is an excerpt from Washington State’s Permit Writer’s Manual (July 1999) covering the determination of Water Effect Ratios (WERs) for discharge permits. It outlines procedures for WET testing, sampling methods for fresh and salt water, design flows, toxicity testing species requirements, and guidance on whether acute or chronic WERs should be determined. The manual provides technical direction for permit writers evaluating receiving water quality and effluent impacts.

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