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: Assessment of Water Quality for the Clean Water Act Sections 303(d) and 305(b) Integrated Report

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.

Updates to the policy

In Nov. 2018, we made major revisions to water quality Policy 1-11, Chapter 1Assessment of Water Quality for the Clean Water Act Sections 303(d) and 305(b) Integrated Report. These revisions incorporated the rulemaking in 2016 to the criteria in WAC 173-201A, surface water quality standards.

In 2019, in a separate process, we adopted and the EPA approved new bacteria criteria that protect Washington waters for recreation activities. This change in criteria meant we had to further update the bacteria methodology in Policy 1-11. In April 2020, we updated the policy, held a public review, and responded to comments received. We finalized the policy in July 2020.