EXH1200045977

Groundwater Flow Characteristics of the Perched Zone 4 How the Perched Zone Sustains Area 3 Wetlands 5 EFFECTS OF BORROW AREA DEVELOPMENT B Proposed Plan for Borrow Area Excavation 8 How the Excavation Will Affect Groundwater Flow 9 USE OF THIS REPORT 11 REFERENCES 13 TABLES Water Level Data for PerchedZone in Borrow Area 3 14 Water Level Data for Perched Zone in Borrow Area 4 1S Summary of SurveyedWater Levels 16 Resultsof ModFIow Calibration 16 FIGURES Site Location Map ElevationContour Map of Top of PerchingLayer Flow Net for ExistingConditions (Groundwater Elevation Contour Map) Hydrographs of Surveyed Water Levels .5 Cross Section A-A' Modeled ExistingConditions Exposure in Proposed Borrow Area Excavation Development of Seepage Face Modeled Post-Mining Conditions Swale to Collect Perched Zone Seepage Modeled Post-Mining Drawdown Contour Map Cross SectionsC-C' and D-D' Hart Crowser "sPa" e iF4978-13 AR 045978 EVALUATION OF PERCHED ZONE INTERCEPTION AND POSSIBLE IMPACTS TO WETLAND HYDROLOGY BORROW AREA 3 SEA-TAC THIRD RUNWAY INTRODUCTION Construction of the proposed Third Runway at Sea-Tac International Airport for the Port of Seattle requires the placement of a substantial embankment composed of fill materials (a mixture of gravel,sand, silt,and clay). The Port plans to obtain some fill materialsfrom borrow areaslocated just to the south of the Airport (see Figure1). Excavationof fill materialsfrom Borrow Area 3 will intercept part of the natural groundwater flow occurringin a shallowperched zone. Currently, part of the groundwater flow from thisperched water-bearing zone supplieswater to wetlands located in Area 3. A recent report by PacificGroundwater Group…

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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 [...]