On Nov. 19, 2021, EPA notified Ecology of a disapproval on our previously approved natural condition provisions in our Surface Water Quality Standards. The natural conditions provisions recognize that some water bodies have poorer water quality due to natural (not human caused) conditions like climate or landscape. Although these provisions have been a part of state water quality standards since 1967, EPA agreed to reconsider whether this part of our standards are currently sufficient. As a result, EPA disapproved the following sections of our surface water quality standards:
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A general provision that allows a water body’s natural conditions to serve as the water quality standard. [WAC 173-201A-260(1)(a)]
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A specific provision that sets the temperature requirement of how cool a water body would be without human alterations. This provision also limits temperature increases caused by human activity to less than 0.3 degrees Celsius. [WAC 173-201A-200(1)(c)(i); -210(1)(c)(i))]
- A specific provision that sets the dissolved oxygen requirement to be at the highest levels a water body can achieve without human alterations. This provision also states that human activity cannot cumulatively cause dissolved oxygen in a water body to decrease more than 0.2 mg/L. [WAC 173-201A-200(1)(d)(i); -210(1)(d)(i)]
The numeric water quality criteria for temperature, dissolved oxygen, and all other parameters still remain in place. This disapproval only removes our ability to include the natural variations of water conditions in some of our water quality decisions.
We are considering revisions to address EPA's 2021 disapproval of Washington's natural condition provisions in our standards, including for fresh and marine dissolved oxygen and temperature (excluding lakes).
In addition, on Sept. 30, 2021, EPA notified Ecology of a disapproval on our previously approved water quality standards provision that allows short-term modifications of the standards for some qualifying activities in WAC 173-201A-410. In 2006, we added additional options to allow the standards to be modified during major watershed restoration activities that may take a longer amount of time than previously defined as short-term, this is no longer allowed using the short-term modification provision.
In this action, EPA also disapproved water quality temperature limits on discharges that create a thermal plume in the receiving water body [WAC 173-201A-200(1)(c)(vii)(C); -200(1)(c)(v)(C)]. Although this limit is used for some discharges, protective numeric temperature limits still apply.