EXH0329020946

Subject: Comments on Recently Received Documents Pertaining to Seattle Tacoma International Airport Project ThirdRunway- Low Flow Analysis GeoSyntecConsultants(GeoSyntec)has been retainedon behalfof the Airport CommunitiesCoalition(ACC) toprovidea technicalreviewof investigation,analysis anddesignrelatingtogeotechnicalandhydrogeologicalelementsoftheproposedThird Runway ExpansionProjectattheSeattleTacoma InternationalAirport.GeoSyntechas previouslycommentedon seismicandgeotechnicalaspectsoftheembankmentfilland MechanicallyStabilizedEarthWail.Inmy October2001declarationinsupportofACC's •motionforstay,I raisednumerousconcernsrelatingtothePort'sLow Flow Analysis. Thisletterpresentsan expansionon theissuesraisedinthedeclarationbasedlargelyon reviewoftheNovember27,2001reportbyPacificGroundwaterGroup(PGG)tided"Port of Sear'de- Sea-TacThirdRunway - Embankment FillModelinginSupportofLow Streamflow Analysis." Introduction The purpose of the low flow analysis is to evaluate the impact that construction of the Third Runway Embankment will have on the rate at which runoff and inf'fltration recharge the creeks. The impact of the embankment is that it stores infiltrating water and subsequently releases it to recharge the low stream flows at different times than if the embankment were not in place. To mitigate the impact of the embankment, excess water must be stored and released to the creeks to maintain conditions that existed prior to the construction of the embankment. The analysis must be able to predict the magnitude of the impact of the embankment and provide a sound basis for calculating l:WR0380(SmTac)kSubmittalGeoSyntec SmTac Comment Letter #3.doc AR 020946 J Walker/Terzi ,J'-_= C,_oSvmecConsult_.ts February 2002 Page 2 the required storage to maintain flows in the creeks. Like any work of this type, the results of the analyses must consider the:reliability of the analytical method and the uncertainty of the parameters input into the analyses. If the analyses are not conservative then other sources of water must be available to make up any shortcomings in the water supply. In the discussion that follows, several key points…

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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 [...]