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EXH AR024406: Water Quality Cert #1996-4-02325 Draft Operational Stormwater Requirements pp.16–17

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Sea-Tac Airport
Third Runway
PCHB
Box 10

This August 2001 draft document outlines Water Quality Certification conditions for Sea-Tac International Airport (STIA), requiring the Port of Seattle to implement a Comprehensive Stormwater Management Plan covering treatment, flow control, and retrofitting of stormwater facilities. Key requirements include obtaining Ecology approval before discharging operational stormwater to state waters, conducting a Water Effects Ratio Study, and ensuring all runoff from impervious surfaces is treated using all known available and reasonable treatment methods. The Port must also retrofit existing stormwater facilities at a rate proportional to new impervious surface construction, with progress documented in quarterly reports.

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Notes

Draft pages 16–17 of 23 from Water Quality Certification #1996-4-02325, faxed August 3, 2001 by King County WLRD to Ecology (Ann Kenny). Covers operational stormwater requirements for Seattle-Tacoma International Airport (STIA) third-runway project, including the approved Comprehensive Stormwater Management Plan (CSMP) Volumes 1–4 (December 2000, revised July 2001), Table A-3 implementation schedule, retrofitting requirements (10% impervious surface trigger), regional detention facilities for Des Moines and Miller Creek, Water Effects Ratio Study (WERS) requirement before discharge to state receiving waters, NPDES permit effluent limitations, WAC 173-201A surface water quality standards, WAC 173-204 sediment management standards, WAC 173-200 groundwater quality standards, AKART treatment requirements, and King County Surface Water Design Manual (KCSWDM). Handwritten margin notes reference ValR, flow control comparison, and CSMP performance standards debate.

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