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EXH AR023802: Ecology Internal Memo — Low Flow Info Required Before Third Runway Mitigation Concurrence

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Sea-Tac Airport
Third Runway
PCHB
Box 10

In a July 6, 2001 internal email, Ann Kenny outlines the technical information that the Washington State Department of Ecology required before approving any mitigation approach for low-flow water impacts related to a Port project. The requested materials included hydrological modeling files, 7-day low-flow analysis data comparing pre- and post-project conditions, a formal mitigation volume proposal, and documentation on the feasibility of vault filling as a mitigation method. Ecology also indicated that written documentation of outcomes would be required following a scheduled July 9 meeting with the Port.

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Internal email from Ann Kenny (Ecology) dated July 6, 2001, sent to Gordon White, Joan Marchioro, Raymond Hellwig, and Tom Young (ATG), listing the information Washington State Department of Ecology requires before concurring with any low-flow mitigation approach related to the Sea-Tac Airport third runway project. Required items include: HSPF input files to Hydrus, documentation on extrapolation of Slice sections across the embankment, Pacific Groundwater time series data graphs, HSPF aggregated output files for 2006 post-project scenarios, ranked and graphed 7-day low flow values for pre-project 1994 data, delta values for 1991–1994 period, Port Of Seattle mitigation volume and duration proposal, vault feasibility documentation for low-flow mitigation, and written documentation of July 9 meeting outcomes. References June 14 meeting Ecology comments on out-of-basin groundwater transfers and impervious area. AR 023802.

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