EXH0154018323

The proposedThird Runwaywill be constructed in part on an embankment of compacted earth fill,so that the new runway el*.vation matches the existing airfield. Part of the runway will alsobe located on native soilsnear the south end of the existingairfield. To accommodate the slope of the existingterrain, the new embankment will vary up to a maximum fill thicknessof about 165 feet. The new embankment is beingconstructedasa zoned earth fill,with specifictypes of soil materialsand compaction requirementsusedin different areasto provide necessarystability, drainage andsettlement characteristics.Overall, the new embankment will includeabout 17,000,000 cubic yardsof compacted earth fill. Approximately _" 3,000,000 cubic yardswill be excavatedonsite, leaving 14,000,000 cubic yards of fill to be imported. The new embankment will be constructed on the west side of the existing airfield,see Figure1. New embankment sideslopeswill have an average inclinationof 2H:IV. Three retainingwallswill be usedto limit the extent of . embankment slope from impactingsensitiveportionsof Miller Creek and adjacenttributarywetlands. Thesewallswill have exposed facesthat range up •_ to maximumheightsof 50 to 135 feet above ground. ., The proposedretainingwallswill be constructedof "mechanicallystabilized earth" usingengineeringtechniquesmore than 30 years old that usesteel or other material to reinforcesoil (FHWA 2001). The Port of Seattle evaluated eight types of retainingwall, and more than 60 wall and slope geometric arrangementsbefore selecting the proposedMSE wallsfor the projecL The methodsand resultsof that evaluation are presentedin the report entitled: Draft Evaluation of Retaining Wall/Slope Alternatives to Reduce Impacts to A4iller Creek Embankment Station 174+00 to I86+00, Third Dependent Runway, that was prepared for the Port by HNTB Corporation,Hart Crowser, Inc., and…

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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 [...]