Tools to interpret and implement

On March 29, 2019, we issued a short-term modification to the WAC 173-201A-200(1)(f) total dissolved gas (TDG) criteria for areas on the lower Snake and lower Columbia rivers. A final environmental impact statement (EIS) on the short-term modification was developed to evaluate the risks of adjusting the total dissolved gas criteria to allow more spill in the Columbia and Snake rivers.

The short-term modification applies to the lower Snake and Columbia rivers, which encompasses the following eight federal dams:

• Lower Granite Dam
• Little Goose Dam
• Lower Monumental Dam
• Ice Harbor Dam
• McNary Dam
• John Day Dam
• The Dalles Dam
• Bonneville Dam

We acted on requests from the Washington Department of Fish and Wildlife, the Columbia River Inter-Tribal Fish Commission, and a coalition of Northwest Sportfishing Industry Association, Columbia Riverkeeper, and Save Our Wild Salmon to adjust our total dissolved gas criteria for dams that spill water to aid fish passage. Providing a short-term modification could help facilitate increased spill at dams during portions of the day to help juvenile salmonids migrating to the ocean.

Timeline

March 29, 2019: Issued short-term modification to WAC 173-201A-200(1)(f). 

March 21, 2019: Issued final EIS (SEPA Register).

Jan. 29 – Feb. 28, 2019: Short-term modification comment period

• Read the comments we received on the draft EIS and draft short-term modification language.
• We held two public hearings (dates and locations below). View the hearing presentation. 
  • Feb. 13, 2019: Vancouver, Wash. 
  • ​​Feb. 19, 2019: Public hearing via webinar

Nov. 16 – Dec. 14, 2018: Draft EIS scoping period

• Environmental Impact Statement (EIS) scoping notice
• ​Read the scoping comments we received

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 use attainability analysis (UAA) is a process that considers the physical, chemical, biological, and economic factors that affect meeting a designated use. The UAA process can result in changing a designated use in the water quality standards.

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.