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EXH AR024917: Draft Memo — Site-Specific WQC Status Update, Copper, Miller, Walker & Des Moines Creeks

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A February 2000 draft memorandum from environmental consultants to Keith Smith summarizes efforts to develop a site-specific water quality criterion for copper in Miller, Walker, and Des Moines Creeks near Seattle-Tacoma Airport, in anticipation of stormwater runoff from a proposed third runway. The memo outlines two technical approaches—the Water-Effect Ratio (WER) and the site-specific metals translator—for potentially raising copper discharge permit limits, and describes toxicity screening and range-finding studies conducted in 1999. The phased study approach was designed to avoid unnecessary costs if the WER method proved infeasible or if the Washington Department of Ecology would not permit its use in adjusting permit limits.

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Draft memorandum dated February 14, 2000, from Doug Henderson and Linda Logan to Keith Smith (project 556-2912-01, task 61A), summarizing efforts to develop a site-specific water quality criterion (WQC) for copper in Miller Creek, Walker Creek, and Des Moines Creek in connection with stormwater from the Sea-Tac Airport third runway (SDS-3 discharge). Covers the Water-Effect Ratio (WER) approach versus the site-specific metals translator method, initial toxicity screening using Ceriodaphnia dubia (January 14, 1999 samples), range-finding WER studies from February 23, 1999, and development of the WER Workplan for Developing a Site-Specific Water Quality Standard for Copper (July 13, 1999). References negotiations with Washington State Department of Ecology (Gary Bailey) and Ecology’s Water Effect Ratio guidance from the Permit Writer’s Manual. AR numbers AR024917–AR024919.

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