Marine dissolved oxygen methods

We have revised the draft performance-based approach methods document we provided for public comment during the natural conditions rulemaking in 2024. The first draft originally included methods to calculate natural conditions criteria for all five parameters that our rule allows methods for.

Based on the feedback we received during the rulemaking comment period and guidance from the EPA, we have revised the document and are focusing only on a method for marine dissolved oxygen at this time. We anticipate future chapters to address other conventional pollutants. 

Background

This document details the process Ecology will use to develop natural conditions site-specific criteria. It is not rule language – it supports the natural conditions provisions in the surface water quality standards. While this document is not rule language, the Environmental Protection Agency (EPA) requires that we hold a comment period and public hearing whenever we make changes to it.