EXH2099033695

TO: Kevin Fitzpatrick, Ecology NWRO Water Quality. Section Manager Ann Kermy, Ecology NWRO Shorelines and Environmental Assessment FROM: Dave Garland, Ecology NWRO Water Quahty Nonpoint Unit_k_ _,_ . SUBJECT: Review of "Sea-Tac Airport Master Plan Update Low Streamflow Analysis" Earth Tech, December 2000 BACKGROUND Comments are provided resulting from my review of the report, "Sea-Tac Airport Master Plan Update Low Streamflow Analysis" (Earth Tech, December 2000). This low streamIlow analysis is associated with the Port of Seattle's latest 401 Permit application for construction on the Sea-Tae Airport Third Runway in proximity to Des Moines, Walker, and Miller creeks. Earth Tech, Inc., performed the analysis which expanded upon analyses in recent studies conducted by Pacific Groundwater Group(PGG) and Earth Tech (Sea-Tac Runway Fill Hydrologic Studies Report, June 2000), Hart Crowser (Effects on lnfiltra_on and Baseflow, Proposed Third Runway. Embankment, October 2000) and Paxametrix (Stormwater Management Plans and HSPF streamflow modeling reports; November 1999, August 2000, and December 2000). The subject report uses the term "low streamflow'" to refer to total flow in a given stream during August and September, since those months are considered critical for minimum streamflows. After characterizing existing August and September streamflow conditions in Miller, Walker and Des Moines creeks, the report considers existing watersiled modeling of current and proposed (post-project) hydrologic condmons. The analysis performed for this report then incorporates factors not taken into account in the existing watershed modeling. WATERSHED MODELING Existing studies had determined that the base year for defining pre-project hydrologic conditions in streams…

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PSCAA Advisory Council Meeting Agenda
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 [...]