Water Quality Assessment & 303(d) List

Part of each Assessment cycle is to evaluate Policy 1-11 and determine if updates are needed. We only update Policy 1-11 when substantial updates are needed. Substantial updates may include updates to water quality standards that modify applicable criteria and our evaluation of data, adding methodologies to evaluate the health of designated uses or significant policy changes.

If we make updates to Policy 1-11, we hold both a Tribal and public review before we finalize the Policy for use in the next Assessment.  

While people can submit data anytime, we hold a specific call for data early in the update process to clarify the timeframe we are focused on for the next Assessment.

We accept data year-round. If you are interested in submitting data to Environmental Information Management (EIM) database email 303d@ecy.wa.gov and we will connect you with our EIM Data Coordinator.

We use data gathered by Ecology and credible data for fresh and marine water from Tribal, federal, state, and local governments, universities, and other organizations submitted to EIM or the federal Water Quality Portal. To help ensure that the data we use is accurate, all data must meet our credible data requirements in Policy 1-11. 

For the last Assessment, we collected over 85 million data points from many water bodies across the state, including 9,322 miles of streams, 449 lakes and 633 square miles of marine water. While this is a vast amount of water and data, the Assessment actually represents only a portion of Washington’s total water bodies – 17% of marine waters, 11% of lakes, 88% of the Columbia and Snake Rivers, and 4% of rivers and streams. Many of the state's more polluted water bodies are where monitoring is focused. Our work and the work of our clean water partners prioritizes areas where human activity could be impacting water quality. This helps us measure how water quality improvement efforts are working. We have minimal data in the Assessment for Washington’s more pristine, and often remote, water bodies. In other words, this is not a report card for water quality for all of Washington, but instead a snapshot in time of water quality for water where there is data.

Ecology staff maintain, update, and use a SQL based data automation tool to assist with data evaluation. Using the tool, we pull in millions of data points (often over 85 million) from EIM and the federal Water Quality Portal that represent ambient water conditions.

Check data quality

First, we use the tool to perform a broad quality review of data (QA/QC) to check that the studies, locations, and parameters all meet the credible data requirements in Policy 1-11. This check ensures that the data are high quality and that we are only using data that has been collected with standard methods.  

Next, the tool looks at the individual data points and flags unusual results, such as if a water temperature value is unusually low, that might be an error or an unseasonably cold day. This allows staff to take a closer look to determine if the data is accurate and reach out to data submitters, as needed, to verify. Both checks help us remove any data that is inappropriate for the Assessment.

Match data with location and limits

The Assessment staff assigns a water body section, or assessment unit based on where the data are located. Then, the tool matches how each water body is used (such as for recreation or fish habitat) with the correct water quality criteria or limits that applies for each pollutant for that use in that water body.

Assign category

Finally, based on how the water body is used, the water quality limits, and the data we have for that location, we use Policy 1-11 to place water bodies into one of five categories (more information about each category). These categories are the Assessment database and tell us the next steps for each water body. 

We follow our government-to-government relationship with federally recognized Tribes and offer early Tribal review and notice about Assessment updates.  In accordance with the Cooperative Management Agreement of Washington’s 303(d) List between the Tribes, Ecology and EPA, we provide early review and discussion on substantial Assessment documents including Policy 1-11 updates and draft Assessment results prior to public review and EPA submittal.

The public comment period is an opportunity for people to comment on the Draft Assessment. During the public comment period, we host informational webinars where we share the Assessment process, key changes in the Draft Assessment, data results, and provide a demonstration of how to use review tools and submit comments.

After the close of the comment period, we review and respond to the comments received with a document that is posted on our webpage.

After we make any necessary changes, the Draft Assessment now becomes the Candidate Assessment that we submit to EPA. EPA has 30 days from the time we submit the Candidate Assessment to take action. Once approved, the Candidate Assessment will become the new, Approved Water Quality Assessment for Clean Water Act regulatory purposes. 

Once we have submitted the Candidate Assessment we will begin the next Assessment cycle – starting again with reviewing Policy 1-11 and announcing the call for data.

Category 1 means a water body meets the state water quality standards. Being placed in this category does not necessarily mean that a water body is free of all pollutants.

Most water quality monitoring is designed to detect specific pollutant(s), so placement in this category means that the water body met standards for all the pollutants that had data. Specific information about the monitoring results may be found in the individual listings. Individual listings place the water body in a category based on data for a specific pollutant.

Water bodies in this category have some evidence of a water quality problem, but not persistent enough to put it in Category 5. These are water bodies that we want to continue to test.

There are several reasons why a water body would be placed in this category. A water body might have pollution levels that are not quite high enough to violate the water quality standards. Or there may not have been enough violations to categorize it as polluted according to our policy.

Water bodies have insufficient data to place them into any of the other categories.

Please see the Reviewing data section above for more information about our process to determine how the data is credible and what information is needed to be confident that there is a water quality issue.

Category 4 means the water body has a pollution problem, but the pollution is being addressed in one of three ways:

• Category 4A — already has an EPA-approved TMDL plan in place and implemented.
• Category 4B — has a pollution control program, similar to a TMDL plan, that is expected to solve the pollution problems.
• Category 4C — is impaired by causes that cannot be addressed through a TMDL plan. Impairments in these water bodies include low water flow, stream channelization, and invasive plants and aquatic life. These problems, while not pollutants, require complex solutions to help restore water bodies to more natural conditions.

Water Quality Assessment Category 4B

We recognize that communities do not have to wait for a formal TMDL planning process to begin improving water quality. They can take the initiative to clean up polluted water. Because these efforts are locally controlled, there is an opportunity to reduce overall costs, and the communities can exert greater control over the cleanup process.

Category 4B is intended for water bodies with a pollution control program in place that is expected to solve the pollution problems. While pollution control programs are not TMDLs they must have many of the same features. There must also be some legal or financial guarantee that the program will be implemented.

To be placed in the "has a pollution control project" category, the pollution control project must meet all of the following criteria:

• Be problem-specific and water body-specific
• Have reasonable time limits established for correcting the specific problem, including load reduction or interim targets, when appropriate
• Have a monitoring component to evaluate effectiveness
• Have adaptive management built into the plan to allow for course corrections, if necessary
• Have enforceable pollution controls or actions stringent enough to attain the water quality standard or standards
• Be feasible, with enforceable legal or financial guarantees that implementation will occur
• Be actively and successfully implemented and show progress on water quality improvements in accordance with the plan

In addition to the conditions above, the project is more likely to gain approval if the following elements are included:

• A description of management measures
• An implementation schedule and measurable milestones
• A description of criteria that are used to determine loading reductions achieved over time
• An information/education component

This is the list of polluted water bodies that are impaired, traditionally known as the 303(d) list. If a water body is in this category it means that we have data showing that the water quality standards have been violated for one or more pollutants impairing a designated use of that water (such as for drinking, recreation, harvesting, and habitat for aquatic life). Total Maximum Daily Loads (TMDLs) or other approved water quality improvement projects or pollution cleanup plans are required for the water bodies in this category. The goal of these plans is to reduce pollution sources throughout the watershed.

The 303(d) list, so called because the process is described in Section 303(d) of the Clean Water Act, lists water bodies in the polluted water category. Federal laws, state water quality standards, and Water Quality Assessment Policy 1-11 guide our Assessment of which water bodies to place on the 303(d) list.

To view the 303(d) list, go to the Water Quality Assessment database and select Category 5 (under Categories).