EXH0248019091

Dear Colonel Graves, Ms. Walker and Ms. Tezzi: Re: Corps Ref. No. 1996-4-02325; Port of Seattle Low Streamflow Analysis Northwest Hydraulic Consultants, Inc., (nh¢) has been retained on behalf of the Airport Communities Coalition (ACC) to provide a technical review of stormwater facilities and streamflow impacts from development activities at SeaTac airport. The purpose of this letter is to comment on the December 2001 "Low Streamflow Analysis and Summer Low Flow Impact Offset Facility Proposal" prepared by Parametrix, Inc., for the Port of Seattle. The December 2001 Low Streamflow Analysis has numerous flaws, including, but not limited to, being largely unresponsive to concerns we have raised previously. For exmnple, while the report now acknowledges poor upper-gage low flow calibration of the hydrologic models used for the analysis, there does not appear to have been any attempt to improve that calibration or to address the resultant uncertainty in the interpretation of model results. Low-flow impacts of Industrial Wastewater System (IWS) improvements and borrow area developments continue to be ignored. The report fails to provide the digital data f-des(as were provided with previous documents) which would give reviewers the opportunity to independently interpret the Port's simulation results and to assess the significance of apparent modeling errors. Also, there appear to be serious fundamental problems in the methodology and assumptions for the third runway embankment seepage analyses and in the integration of that seepage analysis with the HSPF modeling used to predict impacts. Each of the three streams considered by the Low Streamflow…

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Add to CalendarMWednesday Mar 11, 9:00am - 11:35am
1904 3rd Avenue, Suite 105, Seattle, WA 98101
Call to order – Roll Call – Quorum Established – Land Acknowledgement We would like to acknowledge that our Agency operates in four present-day counties, which are the traditional lands of the Coast Salish people, past and present. This acknowledgement does not take the place of authentic relationships with indigenous communities in our jurisdiction and [...]