EXH0106017877

FROM; Dave Garland,NWRO Water Qua_ e , SUBJECT: Sea-Tac Third Runway Borrow Area 3 Wetland Impacts Recommendations for Wetland Preservation BACKGROUND; This memo constitutes my final review comments on potential wetland impacts from the Port of Seattle proposal to excavatesand and gravel fill material from a borrow pit locatedjust south of Sea- Tac Airport. The borrow pit, known as Borrow Area 3, is proposed to be excavated to provide some of the material needed for the proposed Sea-Tac Third Runway fill embankment. Concern for hydrologic impacts from mining in Borrow Area 3 began when independent hydrologic s'udies conducted for Ecology by Pacific Groundwater Group (PGG,2000) concluded that the pro_::v_ed excavation "would likely have substantial impacts to wetland water flows, and possibly biot:,."(pg. 74) There are three wetlands located in Borrow Area 3 that are over one-half acre in area. und fot,r smaller wetlands less than 0.1 acre. The proposed excavatio:: in Area 3 is designed to n,rrowly avoid these sevenwetlands and excavate sand and vavel to depths slightly lower {10- 20 feeT_than the elevations of the wetlands. Groundwater flow direction near Borrow Area 3 _as uncertain at :'_e time of the PGG report, but now has been determined to be generally from the northwest. Recharge to the wetlands is believed to be partially dependent on water from a perchedwater-bearing zone. The excavation proposal is to remove the perched water-bearing zone and perching horizor, on the north and east of the wetlands, but not to the west. Since the Sea-Tat Runway…

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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 [...]