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EXH AR024923: Memo WADOE Position Low Hardness Toxicity and Hardness Adjustment

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Sea-Tac Airport
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A 2001 internal memo from Parametrix, Inc. summarizes a conversation with the Washington State Department of Ecology (WADOE) about water toxicity testing procedures. The memo reports that WADOE opposes adjusting lab water hardness to match site water, recommending instead that storm water tests target the hardness of the receiving water body, typically 40–60 mg/L as CaCO₃. It also notes that low water hardness (around 10 mg/L) may cause chronic reproductive effects in certain test organisms but not acute toxicity.

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Notes

Parametrix, Inc. internal memorandum dated March 26, 2001, from Jim Laughlin (Manager, Environmental Toxicology Laboratory) to Linda Logan and John Brooker, cc Scott Tobiason. Summarizes a phone conversation with Randall Marshall of the Washington State Department of Ecology (WADOE) regarding low hardness toxicity and lab water hardness adjustment for WER (Whole Effluent Runoff) studies. References a study by Mike Stanaway of CH2MHill finding no acute toxicity with C. dubia down to 10 mg/L as CaCO3 but chronic reproductive effects; no chronic effects with P. promelas. WADOE opposes adjusting lab water hardness to match site water; WER studies should test against moderately hard synthetic lab water. Storm water hardness not targeted; receiving water hardness typically 40–60 mg/L as CaCO3. Administrative Record number AR024923, filed in PCHB Third Runway EIS context.

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