Water Quality assessment categories

The water quality assessment compares water data to requirements detailed in Policy 1-11. The assessed waters are placed into categories that describe the status of water quality.

The water quality assessment divides water bodies into the following impairment categories:

Category 1: Meets tested standards for clean waters

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 a specific array of pollutants, so placement in this category means that the water body met standards for all the pollutants for which it was tested. Specific information about the monitoring results may be found in the individual listings.

Category 2: Waters of concern

Waters in this category have some evidence of a water quality problem, but not enough to show persistent impairment. These are waters 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 impaired according to our listing policy.

Category 3: Insufficient data

There is insufficient data to place these waters in any of the other categories, according to Policy 1-11.

Category 4: Impaired waters that do not require a TMDL

Waters that have impairment problems that are being resolved 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 dams. These problems, while not pollutants, require complex solutions to help restore water bodies to more natural conditions.

Category 5: Polluted waters that require a water improvement project

This is the list of impaired water bodies traditionally known as the 303(d) list. Starting with the 2004 Water Quality Assessment, Washington’s 303(d) list of polluted waters were placed under category 5 in the approved assessment. TMDLs or other approved water quality improvement projects are required for the water bodies in this category.

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, and there is no TMDL— or pollution control program — in place.

Can we list a stream in more than one category?

A single water body segment may be listed multiple times, depending on how many tested pollutants violate the water quality standards.

For example:

  • A water body tested for a group of pollutants might be listed in category 5 because temperatures consistently violated standards.
  • It may also be listed in category 2 because some high bacteria counts were found, but not enough to list it as impaired.
  • In addition, it could be listed in category 1 because it tested well for dissolved oxygen.
Each listing will also include the medium in which the pollutant was measured — water, sediment, habitat, or tissue.

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 waters. 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