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EXH AR024630: WAC 173-201A-100 Mixing Zones WA Water Quality Standards Surface Waters

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This Washington State administrative regulation establishes rules for 'mixing zones,' which are designated areas in bodies of water where pollutant discharges are allowed to mix and dilute before meeting water quality standards. The rules set strict size limits for mixing zones in rivers, estuaries, lakes, and ocean waters, and require that dischargers apply all available pollution-reduction technology before a mixing zone is approved. Special provisions are also included for storm water discharges and combined sewer overflows.

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WAC 173-201A-100, Washington Administrative Code, Title 173, Chapter 173-201A: Water Quality Standards for Surface Waters of the State of Washington. Establishes rules for mixing zones for surface water discharges, including requirements for AKART, critical discharge conditions, maximum mixing zone sizes in rivers, streams, estuaries (including Puget Sound, Strait of Georgia, San Juan Islands, Fidalgo Island, Orcas Island, Deception Pass, Admiralty Head, Point Wilson, Cape Flattery, Columbia River), oceanic waters, and lakes/reservoirs. Specifies size limits as percentages of flow and width, distance from discharge ports, acute criteria exceedance zones, overlap of mixing zones, storm water discharge exemptions, and combined sewer overflow provisions. Current with amendments through September 5, 2001. Filed as Exhibit AR024630 in PCHB third runway EIS proceedings.

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