Water quality assessment Policy 1-11

Water quality Policy 1-11 is the guiding policy that we use to assess water quality data, determine if waterbodies are polluted, and decide if further action is needed. This policy also explains how to submit data, and the data quality necessary for inclusion in the water quality assessment

The policy is comprised of two chapters:

Chapter 1: Washington’s Water Quality Assessment Listing Methodology to Meet Clean Water Act Requirements

Chapter 1 describes how water body segments are assessed to determine if they meet surface water quality standards (WAC 173-201A) and sediment management standards (WAC 173-204). After undergoing assessment, the segments are placed in assessment categories. These categories identify the status of the water and determine future regulatory and restoration actions to bring the water back into compliance with the standards.

The chapter also provides specifications for submitting data and data quality necessary for inclusion in the assessment. This chapter — in combination with the guidance documents referenced therein — constitute the “Listing Methodology” for the Integrated Report required by the U.S. Environmental Protection Agency (EPA), which serves as the Section 303(d) list and 305(b) report as required by the federal Clean Water Act.

Chapter 2: Ensuring Credible Data for Water Quality Management

Chapter 2 describes the quality assurance measures, guidance, regulations, and existing policies that help ensure the credibility of data and other information used in agency actions on state surface water quality. This chapter meets the requirements of Washington's 2004 Credible Data Act.

Agency actions include:

  1. Determinations of whether a surface water is supporting its designated use, such as the 303(d) and 305(b) assessment processes.
  2. Establishment of a water cleanup plan, or total maximum daily load (TMDL), and the associated load allocations and wasteload allocations.
  3. Revisions to the water quality standards.

Current update to the policy

We are accepting public comments for the 2022 revisions of Policy 1-11, Chapter 1: Washington’s Water Quality Assessment Listing Methodology to Meet Clean Water Act Requirements. The public comment period is open from Nov. 7, 2022 to Jan. 6, 2023.

The proposed changes include a new methodology for evaluating freshwater harmful algae blooms, a temporary suspension of the natural conditions methodology, and non-substantial edits to improve clarity of the Water Quality Assessment, including listing based on narrative standards. The revisions are available in two documents: 

Make a comment online or visit the comment page for more information

Previous updates 

Major revisions to water quality Policy 1-11, Chapter 1 were completed in 2018. Further revisions in 2020 updated assessment methodologies for changes to the recreation use bacteria criteria.

We review the policy as the first step in the process to update the Assessment.