EXH1189045601

Groundwater Flow Characteristics of the Perched Zone 4 How the Perched Zone Sustains Area 3 Wetlands 5 EFFECTS OF BORROW AREA DEVELOPMENT 8 Proposed Plan for Borrow Area Excavation 8 How the Excavation Will Affect Groundwater Flow 8 USE OF THIS REPORT 11 REFERENCES 12 TABLES Water Level Data for Borrow Area 3 13 Water Level Data for Perched Zone in Borrow Area 4 14 Summary of Surveyed Water Levels 15 Resultsof ModFIow Calibration 15 FIGURES Site Location Map Elevation Contour Map of Top of Perching Layer Flow Net for ExistingConditions (Groundwater Elevation Contour Map) Cross Section A-A' Modeled Existing Conditions 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 Hart Crowser Page i J-4978-13 AR 045602 EVALUATION OF PERCHED ZONE INTERCEPTION AND POSSIBLE IMPACTS TO WETLAND HYDROLOGY BORROW AREA 3 SEA-TAC THIRD RUNWAY INTRODUCTION Constructionof the proposedThird Runwayat Sea-Tat InternationalAirport 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 materials from borrow areas located just to the south of the Airport (see Figure I ). Excavation of fill materials from Borrow Area 3 will intercept part of the natural groundwater flow occurring in a shallow perched zone. Currently, part of the groundwater flow from this perched water-bearing zone supplies water to wetlands located in Area 3. A recent report by Pacific Groundwater 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 [...]