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EXH AR023564: Letter Water Resources Consulting (Peter Willing) to Army Corps & Ecology — STIA Sec 404/401 Permit Low Flow Analysis & Flow Impact Offset Facility

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Sea-Tac Airport
Third Runway
PCHB
Box 10

A water resources consultant, writing on behalf of the Airport Communities Coalition, argues that the Port of Seattle's July 2001 Low Flow Analysis for Sea-Tac Airport expansion fails to provide reasonable assurance that the project will meet water quality standards in Miller, Walker, and Des Moines Creeks. The letter criticizes the submission as incomplete and rushed, noting missing figures, unfinished sections, and an unresolved plan to store the required 46 acre-feet of stormwater across the three watersheds. The consultant contends that the Port's proposed water quality protections—including filtration, aeration, and biofiltration swales—are unproven, inadequately designed, and fall short of the regulatory standard required for Section 401/404 permit approval.

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Letter dated August 6, 2001 from Peter Willing, Ph.D. of Water Resources Consulting L.L.C., filed on behalf of the Airport Communities Coalition (ACC), to U.S. Army Corps of Engineers (Muffy Walker, Gail Terzi) and Washington State Department of Ecology (Ann Kenny) regarding Section 404/401 permit application for Sea-Tac Airport third runway (Reference 1996-4-02325). Critiques the Port Of Seattle’s July 2001 ‘Low Flow Analysis – Flow Impact Offset Facility Proposal’ by Parametrix, citing incomplete document text, missing appendices, absence of structural water quality features, inadequate storage vault design (only 25% of required 46 acre-feet of storage shown — 18.8 acre-feet Miller Creek, 15 acre-feet Walker Creek, 12.2 acre-feet Des Moines Creek), reliance on unproven biofiltration swales for nutrient removal, propylene glycol at SDS3 (Des Moines Creek) at 407 mg/L, dissolved oxygen concerns, copper/zinc/cadmium metal remobilization, and failure to provide reasonable assurance of water quality standards compliance under Clean Water Act.

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