Tools to interpret and implement

The Chelan Public Utility District is requesting revisions to the water quality standards for the Chelan River. These revisions include:

• Aquatic life use designation to reflect highest attainable use in the river
• Site-specific temperature and dissolved oxygen criteria that protect the proposed aquatic life use designation

We hope to initiate the public process for this rulemaking with a rule announcement (CR-101) later this year. This decision to announce a CR-101 must first be approved by Ecology's director.

Application materials:

• Application cover letter
• Chelan River Use Attainability Analysis report

Ecology response letter:

• Ecology letter to Chelan Public Utility District, Feb. 18, 2020

Mixing zones are areas adjacent to an effluent outfall or in-water activity where water mixing causes dilution of the effluent with the receiving water. Permitted dischargers may have a specified boundary at the outside edge of the mixing zone where they must meet the water quality standards.

Site-specific criteria are criteria adopted for a waterbody that is different from the established criteria based on local conditions and/or key species. The site-specific criteria should fully protect existing and attainable uses for the waterbody.

A water quality offset is a tool used to reduce pollution levels for a specific water quality parameter in a waterbody in order to allow new or expanded permitted discharges.

Intake credits is a procedure for establishing effluent limits that takes into account the amount of a pollutant that is already present. When a facility releases a discharge into the same water body the pollutant must be equal or less than the starting level.