Tier III Antidegradation Eligibility
To be eligible for designation as outstanding resource water in
Washington, one or more of the following must apply:
- The water is in a relatively pristine condition (largely absent human
sources of degradation) or possesses exceptional water quality, and also
occurs in federal and state parks, monuments, preserves, wildlife refuges,
wilderness areas, marine sanctuaries, estuarine research reserves, or wild
and scenic rivers.
- The water has unique aquatic habitat types (for example, peat bogs) that
by conventional water quality parameters (such as dissolved oxygen,
temperature, or sediment) are not considered high quality, but that are
unique and regionally rare examples of their kind.
- The water has both high water quality and regionally unique recreational
- The water is of exceptional statewide ecological significance; or
- The water has cold water thermal refuges critical to the long-term
protection of aquatic species. For this type of outstanding resource water,
the non-degradation protection would apply only to temperature and dissolved
To determine whether or not to designate a waterbody as an outstanding
resource water, the Department of Ecology considers factors relating to the
difficulty of maintaining the current quality of the water body and the level of
support from affected parties.
Outstanding resources waters can be designated for either Tier III(A) or Tier
- Tier III(A) is the highest level of protection and allows no further
degradation after the waters have been formally designated.
- Tier III(B) is the second highest level of protection and conditionally
allows minor degradation to occur due to highly controlled actions. The
requirements for Tier III(B) are:
- Sources of pollution, considered individually and cumulatively, are
not to cause measurable degradation of the water body.
- Sources of pollution must use applicable advanced waste treatment
and control techniques (and best management plans [BMPs] for nonpoint
sources) that reasonably represent the state of the art in technology,
and must minimize the degradation of water quality to non-measurable
levels where total elimination is not feasible.
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Last updated October 2007
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