Washington State's Water Quality Assessment [303(d)]

Introduction

About the 303(d) List

Washington’s 303(d) list of polluted waters is now found under Category 5 of the 2008 Washington State Water Quality Assessment.

Section 303(d) of the federal Clean Water Act requires Washington State to periodically prepare a list of all surface waters in the state for which beneficial uses – such as for drinking, recreation, aquatic habitat, and industrial use – are impaired by pollutants. These are water quality limited estuaries, lakes, and streams that fall short of state surface water quality standards, and are not expected to improve within the next two years.

Waters placed on the 303(d) list require the preparation of Total Maximum Daily Loads (TMDLs), a key tool in the work to clean up polluted waters. TMDLs identify the maximum amount of a pollutant to be allowed to be released into a waterbody so as not to impair uses of the water, and allocate that amount among various sources. In addition, even before a TMDL is completed, the inclusion of a water on the 303(d) list can reduce the amount of pollutants allowed to be released under permits issued by Ecology.

Ecology’s assessment of which waters to place on the 303(d) list is guided by federal laws, state water quality standards, and the Policy on the Washington State Water Quality Assessment (PDF). This policy describes how the standards are applied, requirements for the data used, and how to prioritize TMDLs, among other issues. The goal is to make the best possible decisions on whether each body of water is impaired by pollutants, to ensure that all impaired waters are identified and that no waters are mistakenly identified.

In the previous lists, the primary water quality problems in our state’s waters were temperature and fecal coliform bacteria. Both are generally associated with nonpoint source pollution – that is, pollution which comes from many diffuse sources, not just from the end of a pipe.

Temperature is significant for the health of aquatic life. Salmon, especially, and other fish need cooler temperatures to survive and spawn. High temperatures can occur due to the discharge of hot water from power plants and industrial sources or, more often, from loss of vegetation along streams that used to shade the water and from new land uses (buildings and pavement) from which rainfall picks up heat before it runs off into the stream.
Fecal coliform bacteria is significant for human health as an indicator of the presence of disease-carrying organisms. It commonly comes from livestock and failing septic tanks.

Other water quality problems which lead to 303(d) listings in Washington State include:

Toxic substances from industrial and other sources, which can collect in sediments on the bed of the water or in the tissues of aquatic life.
Erosion from roads, construction, and agriculture, which increases sediment in streams that can cloud the water and cover aquatic habitat.
Too much organic waste decaying in the water, which can lower the levels of dissolved oxygen that fish and other aquatic creatures need to survive.
Excessive nutrients, such as phosphorus and nitrogen, are the primary problem in Washington's lakes. Sources include irrigated agriculture, gardening practices, and urban and suburban property development. The nutrients cause algae and other aquatic plants to grow in lakes, which deprive aquatic life of vital oxygen. Algae can also make lakes unusable for recreation.

305(b) Report

The Section 305(b) report, required by the Federal Clean Water Act, describes the current conditions of the state's waters to the U.S. Congress and the public. It is a state-wide assessment of the status of all the state's waters, whereas the 303(d) list reports just on the impaired waters of the state.

Please see the Historical Information on Washington State’s Water Quality Assessments, 303(d) Lists & 305(b) Reports to view previous 303(d) and 305(b) reports.

Last updated February 2008