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EXH AR023555: Letter Water Resources Consulting to WA Ecology — Lake Youngs Outlet Temp Data, Des Moines Creek Flow Augmentation Facility

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A water resources consultant wrote to the Washington State Department of Ecology in September 2000, arguing that Seattle Public Utilities' Lake Youngs water supply is too warm to effectively cool Des Moines Creek during summer months. Temperature data showed that Lake Youngs outlet water exceeds 16°C from mid-June through mid-October — the exact period when cooler stream temperatures are needed — reaching as high as 20°C in summer 2000. The letter concludes that the Port of Seattle's proposed flow augmentation facility for Des Moines Creek cannot rely on this water source for temperature improvement, undermining the Port's claims about its water supply plan.

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Letter dated September 15, 2000 from Peter Willing, Ph.D. of Water Resources Consulting L.L.C. (Bellingham, WA) to Tom Luster at Washington State Department of Ecology (P.O. Box 47600, Olympia), supplementing a prior September 5, 2000 letter regarding the Des Moines Creek Flow Augmentation Facility. Willing argues that Seattle Public Utilities’ Cedar River/Lake Youngs water supply is too warm to lower Des Moines Creek stream temperatures below 16°C during the critical summer interval (mid-June through mid-October), as the Lake Youngs outlet temperature rises above 16°C by mid-June and peaked at 20°C in summer 2000. Document challenges the Port Of Seattle’s claim that it has secured a suitable water supply for flow augmentation. Includes attached graph of Lake Youngs Outlet Temperatures (1999 data from Seattle Public Utilities), annotated with Jun 19 and Oct 15 crossover dates. Administrative Record number AR023555.

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