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HomeMy WebLinkAboutSTAFF REPORT_RHODODENDRON RIDGE_LUA17000565DEPARTMENTOFCOMMUNITYANDECONOMICDEVELOPMENT..._.._.s_u.a00”j.enton3PLANNINGDIVISIONCERTIFICATEOFEXEMPTIONFROMCRITICALAREASREGULATIONSEVALUATIONFORM&DECISIONDATE:September05,2017PROJECTNUMBER:LUA17-000565PROJECTNAME:RhododendronRidgeStormDrainageCriticalAreasExemptionPROJECTMANAGER:AngeleaWeihs,AssistantPlannerOWNER:LeviRowse,iCapRhodyRidge,LLC3535FactoriaBlvdSE#Suite5000Bellevue,WA98006CONTACT:EmilyLarson,Goldsmith1215114thAveSEBelllevue,WA98004LOCATION:4343LINCOLNAVENEDESCRIPTION:Theapplicantisrequestingapprovalofacriticalareasexemptionforaproposaltoextendastormlinewestfromanapprovedshortplat,withintheCityofNewcastle.ThesubjectpropertyislocatedeastofLincolnAveNE,withinunimprovedCityofRentonright-of-waytothenorthof4348LincolnAveNE.Thproposedstormdrainagelinewouldbeconstructedasasurface-mountedHDPEpipeleadingdownasteeplysloping,unimprovedportionoftheCityofRentonright-of-wayforSE80thStreet.Thestormlinewouldbeextendedthroughtheunimprovedright-of-wayandwouldconnecttoanexistingstormlineinLincolnAveNE.Sensitiveandcriticalslopes,andhigherosionhazardsaremappedonsiteoftheproposedstormline.ATypeFstreamandWetlandsaremappedoffsitebasedoncityrecords.Notreeremovalisproposedwiththisproject.Thesurfacepipeisproposedtobeinstalledbetweenclearinglimitstoavoidtrees.InstallationofnewstormdrainagelinesinanygeologichazardareaisexemptwhenageotechnicalreportdemonstratesthattheinstallationwouldcomplywiththecriterialistedinRMC4-3-050J.3andthattheinstallationwouldbeconsistentwitheachofthepurposesofthecriticalarearegulationslistedinRMC4-3-050.A.Also,toqualifyfortheexemption,thereportmustproposeappropriatemitigationforanypotentialimpactsidentifiedinthereport.TheapplicantsubmittedageotechnicalstudypreparedbyAssociatedEarthSciences,Inc.(datedMay26,2016)withtheapplication.ThestudystatesthattheslopingareapresenttothewestofthesubjectsiteandtheSE80thStreetright-of-waydonotshowevidenceofrecentdeep-seatedlandsliding.ThePage1of4 CityofRentonDeportmentofCommunity&EconomicDevelopmentCertificoteofExemptionfromCriticalAreosRegulationsRhododendronRidgeStormDrainoqeCriticolAreasExemptionLUA17000565reportalsostatesthattheslopeshouldnotbeadverselyaffectedbytheproposedimprovements,includingtheproposedsurface-mountedHDPEstormwaterpipeleadingdowntheSEBothStreetright-of-way,usingcurrentengineering,architectural,andplanningstandards.ThestudystatesthatsitesoilsshouldbesuitabletosupporttheanticipatedHDPEstormwaterpipe,andinaddition,theproposedstormwaterdetentionanddischargesystemwouldremoveaportionofstormwatervolumefromanareaabovethetopoftheslopingground,reducingtheriskofsaturationoftheslopeduetorunofffromupgradientlocationsduringorsubsequenttosignificantrainfallevents.Thereportstatesthatriskoflandslidesorslopeerosionposedbytheproposedimprovementsislowforthesiteprovidedcurrentengineeringstandardsandtherecommendationscontainedthegeotechnicalstudyarefollowed.Therepocincludesarecommendationrelatedtopreservationofvegetationofthefaceoftheslopesinordertopreventsoilerosion,aswellasarecommendationtopreventstormwaterrunofffromflowingtowardsthesteepslopes.Tobeconsistentwiththerecommendationsofthegeotechnicalstudy,staffrecommendsasaconditionofapprovalthatthevegetationonthesteepsslopesremaininplacetoprovidearootsupportforthenear-surfacesoilsalongtheslopes,andthatthestormwaterrunofffromimpermeablesurfacesbecollected,routed,anddischargedthroughaproperlydesignedstormwatersysteminordertopreventuncontrolleddischargefromimpermeablesurfacesflowingtowardsorontothesteepslopes.Necessarystormdrainageconveyancesystemsareexemptwithinstreamandwetlandbuffersprovided:theyaredesignedtominimizeimpactstothebufferandcriticalareas,theyaresitedtoreduceimpactsbetweenthecriticalareasandsurroundingactivities,thesitetopographyrequirestheirlocationwithinthEbuffertoallowhydraulicfunction,andthestandardbufferzoneareaassociatedwiththecriticalareaclassificationisretainedpursuanttoRMC4-3-050G2.TheapplicantsubmittedastandardstreamstudyandwetlandreconnaissancepreparedbyAltmannOliverAssociates,LLC.(datedDecember28,2016)withtheapplication.Perthereport,Thesouthwesternportionofthesiteconsistedofamowedandmaintainedlawnassociatedwiththeoff-siteresidencetothesouth.Inaddition,amowedcorridorofgrassesextendsuptheslopewithintheright-of-wayadjacenttheexistingsanitarysewerline.Thestudystatesthatnohydrophyticplantcommunitieswereobservedonorimmediatelyadjacenttothesiteduringthereconnaissance.Boringstakenthroughoutandadjacenttotheundisturbedportionsofthesiteduringthereconnaissancerevealedhighchroma,non-hydricsoils,withnoevidenceofpondingorprolongedsoilsaturation.Thestudyidentifiesoneoff-sitestream(TypeF)tothesouthwest,whichincludesa115footbufferthatextendsintothesouthwestportionoftheSE80thStreetright-of-way.Thestudyconcludesthatpotentialoff-sitewetlandtothesouth,asmappedontheCitymappingsystem,wasnotobservedandappearstobemiss-mapped.Thestudyconcludesthattheproposedstormlineisdesignedtoavoidalldirectimpactstocriticalareas.Thereportstatesthatthepipewouldbeinstalledwithintheexistingmowed/maintainedlawnareasoftheright-of-wayandwouldnotrequiretheremovalofanysignificantbufferD,ao)nfit CityofRentonDeportmentofCommunity&EconomicDevelopmentCertificateofExemptionfromCriticalAreasRegulationsRhododendronRidgeStormDroinogeCriticalAreasExemptionLUAI7-000565vegetation,therebyminimizingimpactstowildlifeandsignificantvegetationCRITICALAREA:sensitiveandProtectedslopes,HighErosionHazards,StreamandWetlandsEXEMPTIONJUSTIFICATION:RentonMunicipalCode,Section4-3-050C.4.a.iii.StormwaterConveyanceinBuffer:Necessaryconveyancesystemsincludingstormwaterdispersionoutfallsystemsdesignedtominimizeimpactstothebufferandcriticalarea,wherethesitetopographyrequirestheirlocationwithinthebuffertoallowhydraulicfunction,providedthestandardbufferzoneareaassociatedwiththecriticalareaclassificationisretainedpursuanttoRMC4-3-05062,andissitedtoreduceimpactsbetweenthecriticalareaandsurroundingactivities.FINDINGS:TheproposeddevelopmentisconsistentwiththefollowingfindingspursuanttoRMCsection4-3-OSOC.2.d:i.TheactivityisnotprohibitedbythisoranyotherprovisionoftheRentonMunicipalCodeorStateorFederallaworregulation;ii.TheactivitywillbeconductedusingbestmanagementpracticesasspecifiedbyindustrystandardsorapplicableFederalagenciesorscientificprinciples;iii.Impactsareminimizedand,whereapplicable,disturbedareasareimmediatelyrestored;iv.Wherewaterbodyorbufferdisturbancehasoccurredinaccordancewithanexemptionduringconstructionorotheractivities,revegetationwithnativevegetationshallberequired;v.Ifahazardousmaterial,activity,and/orfacilitythatisexemptpursuanttothisSectionhasasignificantorsubstantialpotentialtodegradegroundwaterquality,thentheAdministratormayrequirecompliancewiththeWellheadProtectionArearequirementsofthisSectionotherwiserelevanttothathazardousmaterial,activity,and/orfacility.SuchdeterminationswillbebasedDECISION:AnexemptionfromtheCriticalAreasRegulationsisherebyApprovedwithConditions*.CONDITIONS:1.Thevegetationonthesteepsslopesofthepublicright-of-wayshallremaininplacetoprovidearootsupportforthenear-surfacesoilsalongtheslopes.Anyvegetationthatisremovedshallbereplantedtobeconsistentwithpre-developmentconditions.Page3of4 CityofRentonDepartmentofCommunity&EconomicDevelopmentCertificateofExempdonfromCriticalAreasRegulationsRhododendronRidgeStormDrainageCriticalAreasExemptionLUAI7-000565CONDITIONS:2.Thestormwaterrunofffromimpermeablesurfacesshallbecollected,routed,anddischargedthroughaproperlydesignedstormwatersysteminordertopreventuncontrolleddischargefromimpermeablesurfacesflowingtowardsorontothesteepslopes.3.Iftheuseofanyheavyequipmentisneededforthisproposal,treeprotectionfencingshallbeinstalledaroundthedriplinesofthetreesnearwheretheuseoftheheavyequipmentwilloccur.SIGNATURE&DATEOFDECISION:______________________________________________September05,2017JenniferHenning,PlanningDiredtrDateTheabovelandusedecisionwillbecomefinalifthedecisionisnotappealedwithinthe14-dayappealperiod(RCW43.21.C.075(3);WAC197-11-680).APPEALS:AnappealofthisadministrativelandusedecisionmustbefiledinwritingtogetherwiththerequiredfeetotheCityofRentonHearingExaminer,CityofRenton,1055SouthGradyWay,Renton,WA98057,onorbefore5:00p.m.,onSeptember19,2017.RMC4-8-110governsappealstotheHearingExaminerandadditionalinformationregardingtheappealprocessmaybeobtainedfromtheRentonCityClerksOffice,(425)430-6510.RECONSIDERATION:Within14daysofthedecisiondate,anypartymayrequestthatthedecisionbereopenedbytheapprovalbody.Theapprovalbodymaymodifyhisdecisionifmaterialevidencenotreadilydiscoverablepriortotheoriginaldecisionisfoundorifhefindstherewasmisrepresentationoffact.Afterreviewofthereconsiderationrequest,iftheapprovalbodyfindssufficientevidencetoamendtheoriginaldecision,therewillbenofurtherextensionoftheappealperiod.Anypersonwishingtotakefurtheractionmustfileaformalappealwithinthe14-dayappealtimeframe.EXPIRATION:Five(5)yearsfromthedateofdecision(datesigned).Attachments:Vicinity/NeighborhoodDetailMap,SitePlan,StreamandWetlandStudyP2a0zinfA P I I I •:r 43r5 - --- PROPOSED STORMWATER EXTENSION LOCATION (PROJECT SITE) I-- -- —= 1 ‘—— - -i -?rrt 4—4y’c- I r cc ,7r451 -, Legend City and County Boundary L Cily oF Renlon Parcels Notes Rhododendron Ridge Stonnwater Extension --‘:r--I Information Technology -GIS This map is a user generated static output from an Internet mapping site and 272 0 1 36 272 Feet is for reference only.Data layers Ihat appear on Ihis map may or may noL be City of Fteiitii_$1i1RentonMapsupport@Renlonwagovaccurate,current,or otherwise reliable.- WGS_1984_Web_Mercalur_Auxiliaiy_Sphere Finance &iT Division06/21/2017 THIS MAP IS NOT TO BE USED FOR NAVIGATION Neighborhood Map 55 77th P1 St ‘77,pg C C - 7, N N DEVELOPMENT SITE CI SI SC re-‘r 81-SI m ra l.a 0 VAULTACCESSI)ACCESSRiSERSARE4DIMEMfloHECOxIKCONETOPSLQIONLASNECESSARY(FEC—2’HICHIECORDCJ’11101SLaIoNIOVERRINI’OiAIj.HTEEINVMLTWIDSOKCRAVELNCUGELPROVIDEEARDRSST0RITTONOFVAULTPIEDETAILSETSD2-PROVIDEEVENTLEWEINEMANHOLECOVDESPOEAUACCESSROCKSLIII’REMOVASEELOCTINCPANELSAlADELIETTTHE2009ECS*DMREQUIREMENTSNa-—wnflErflYAULTSECTIONA-AICAILl•_ITIAIE‘-tajAPPROVEDFORCONSTRUCTIONIT:______________________BAIL___________CI’OFNLACASIILjrsr2nr2)IIa,—Th-n—I113)E,I,Az—IliltlIE—GREaIno—--)5fl•,,,17’/URpm‘U’mbIUa—ee-/rLRRASEMAGH—IEUR‘AoRIIREMiTPrrnfl—-SEI;4,SEI4SECTION29.TOWNSHIP24N,RANGESE,WN.CITYOFNEWCASTLE,KINGCOUNTY.WASHINGTONVAULTVLNnEAOON;v,;III’-rRAMRENTOPENNESARERElAtEDClimESENECWRAL,:‘IIPWASII12,UI21VENTSIPAE10WIDSCAPIAAEASSEALL1112DAMPS509I40PVCPIPEOREVJALJWSTKLIGHTDUTYDEOP-INclAm.‘‘I‘ISlABINPAEEDARIASSLIJECTTO550CLOAKSRAHTICSHALL‘VLTACCDXrITIi’HJiCLASSSIDTCSTLSIRONOVE(RHIFEMilCAST_,4__—°OWEIjHI5.IRONENOMIDCOVERIaTMHC,OUNORT.INC.PARTNORHO./‘FaDDLI‘.(..00REQUHUKH2001AIEII’DEPSHCoNCaSDICSELAA5J‘W20LI5,,’.IIII—6.\,,.‘\‘I‘IIVHWTSmG’___Ii-.1111\‘.TRTP‘4-.5i\IPSSIMITPIçIHIi‘Ls;44çjg,7I%\xIi..,.I‘IN.L-______(1fli“-•I4Tt1L:tt5tn,,.IeLi’rc±rAI‘cEirIFnovAat\aE’Jtr-——“•“t’—VAItTAS4.Sf1052’.‘k,-Ji’S:‘*VE;4il3MIM3M3ML2±r1IEESJEEEEli==-,-——/*mteL-£fl------Illmx==-r.—---1RpmlIlTct&TlnMUIPIPIrmATM—EMSflWIILI•SIt;4IonHHPEDI5RThH&ITII4O—_MDIIa11131*E7—1’-DETENTIONVAULTPLAN&SECTIONGDLDSMITH—RHODODENDRONRIDGESD—iLANDDEVELOPMENHSEEVICES‘.—.tERPPLANSET(IIIIARUIRERS’THOaimlKIlMo-T,;IREiOWOFNLSROSUERiNGJNWWASHINGSIEnROllSC—uvSVraIronpM.-zo’BA-—-.3M- AYThOVIOFORCONSTRUCTiON___________________________DAIL_____________OTT1WNECASTU;r:.\SLIEVECONNECTIONDETAIL<t>ía-ô‘7-0-0:,!,,OPTHOU’PICCI.UtI””SE14.SE1/4SECTiON29.TOWNSHIP24N,RANGESE.V.M.CITYOFNEWCASTLE,KINGCOUNTY,WASHINGTONS‘/1,‘IIifII‘SS1,‘4,I,.I6/—I;:51otOIITInTacoIWIoIIIIItflflfSISSS1PWITóTITO’•2flTtcawWIflMOflSflC•.cu,n..cnnmoLonncs-4I.WI1T0,z/r°e”INcTTJflaCIJVs?’00f\.-9Q\j--€ir——-C--t”L——zc2t.’—Z’((vsii-:/4,k\‘.L’a.¶‘j,‘o\\_Wflke0L—“Vccso•-o.ne.::it’.‘:=‘)r,-,-,.tt’‘S—‘I-ot’tI,Ti!,::iIazI,,___________--I4000ScahI-so--IHI/Inn.h-Ill..-,.—c”!0(1011ISlETNnm.:Jr.--/-—-—————————————c_‘—I.--—-.M_C•-.-—--ui,oe‘.,,,,4I—..—iaE’‘—“.--‘-In—TW0C00(0(1P0CCIa---ISOala,HUTOW.—06—Th:-;-Iiijr—‘1!$T7—-FdiJ!W——4f’gt—-f-----——-N,j.4TOO!TCNF6000l.’flWTO—-HH.040010IS.00-—a44oI-hO0140440GDLDSMIThLANDDEVELOPMENiSLRVICESII06400tLr‘-06140GIsT7107.4000Callo.,..jaOnor401WASTUOFF-SITESTORMDRAINOUTFALLRHODODENDRONRIDGEERPPLANSETElI-C0501410SD-3l,,50l,cTO assaciatedearthsciencesEXHIBIT3iicorparatedMay26,2016RevisedJune7,2016ProjectNo.KE160152AiCapRhodyRidge,LLC3535FactoriaBoulevardSE,Suite500Bellevue,Washington98006Attention:Mr.LeviRowseSubject:GeologicDocumentReviewandSiteReconnaissanceRhododendronRidge11230SE80thStreetNewcastle,WashingtonDearMr.Rowse:ThisletterpresentstheresultsofAssociatedEarthSciences,Inc.’s(AESI’s)sitereconnaissanceforthepropertyreferencedaboveat11230SEg0thStreetinNewcastle,Washington.ThesitereconnaissancewasperformedingeneralconformancewithAESI’sscopeofworkoutlinedinourproposaldatedMarch30,2016.Ourstudywasintendedtoprovideinformationregardingtheproposedresidentialdevelopment,particularlytheproposedstormdrainageoutfalltobeconstructedasasurface-mountedHDPEpipeleadingdownasteeplysloping,unimprovedportionoftheCityofRentonright-of-wayforSE80thStreet.PROJECTDESCRIPTIONThesubjectsiteistheexistingresidentialpropertylocatedat11230SE80thStreetinNewcastle,Washington(KingCountyParcelNos.334330048-0,-2,-3).Weunderstandthattheproposedprojectincludes15residentiallots,withassociatedgrading,access,andutilities,includingaproposedstormdrainageoutfalltobeconstructedasasurface-mountedRDPEpipeleadingKirklandOfficeI911FifthAvenueIKirkland,WA95033PI425.827.7701Fl425.827.5424EverettOfficeI29114HewittAvenue,Suite2IEverett,WA98201PI425.259.0522FI425.827,5424TacomaOfficeI1552commerceStreet,suite102ITacoma,WA98402PI253.722.2992FI253.722.2993www.aesgeo.corn RhododendronRidgeGeologicDocumentReviewNewcastle,WashingtonandSiteReconnaissancedownasteeplysloping,unimprovedportionoftheCityofRentonright-of-wayforSE80thStreet.WeunderstandthattheCityofRentonhasrequiredageologicreconnaissanceofthisslopetoprovideanopinionregardingthesuitabilityoftheproposedoutfallconfiguration.ThepurposeofAESI’sstudyistoperformasitereconnaissancedowntheslopingportionoftheSE80thStreetright-of-waytoprovideouropinionregardingstabilityorerosionissuesalongthedrainagealignmentundercurrentconditions,giventheproposedsurface-mounteddrainsystem.Also,ourstudyincludesreviewofavailableinformation,includingpastexplorations,wetlanddelineationsbyothers,andLightDetectionandRanging(LiDAR)imagery,toprovideanopinionregardingtheoverallstabilityofthesubjectsiteandtheslopesleadingdowntothewest,giventheproposedimprovements.Aspartofapreviousstudy,AESIobservedanexplorationboringadvancedintheareaofthenorthwestcornerofthesubjectsite.Also,forouruseinpreparingthisletter,wehavebeenprovidedwith“GeotechnicalEngineeringStudy—RhododendronRidge,”preparedbyEarthSolutionsNW,tIC(EarthSolutions)anddatedJanuary29,2015,whichdocumentedexplorationscompletedbyothersatthesubjectsite.RESEARCHRESULTSInadditiontoperformingoursitereconnaissance,AESIresearchedavailablepublishedgeologic,soils,andgroundwaterinformationaboutthesiteandareaimmediatelyadjacenttotheproperty.Theresourcesthatweconsultedwere:•KingCountyWebsite(iMAP)•PreviousgeotechnicalreportsbyAESIandothers(seebelow)•U.S.GeologicalSurvey(USGS)GeologicMapsSitegeologyandgeomorphologywereformedfromglacialdepositionalprocessesandsubsequenterosiontoformthecurrenttopographiclandforms.Theresultsofourresearcharepresentedbelow.AerialPhotographReviewNon-stereographicaerialphotographsavailablefromiMAPwerereviewedforthesite.Wereviewedselectedphotographstakenfrom1936to2013.Theobjectivefortheaerialphotographreviewwastodeterminethegeneralhistoryofdevelopmentinthevicinityofandwithinthesite.Moy26,2016;Revisediune7,2016ASSOCIATEEARTHSCIENCES,INC.JPMd—K6160152A3—Projerts2O16O152KEWPPage2 RhododendronRidgeGeologicDocumentReviewNewcastle,WashingtonandSiteReconnaissance•1936-Thisblackandwhitephotographindicatesthatthesubjectsite,alongwiththeSE8QthStreetright-of-wayandtheslopestothewestofthesubjectsite,isvegetatedwithwhatappeartobedeciduoustreesandshrubs.Severalrowsoforchardtreesarelocatedtotheeastofthesubjectsite.Therearenoobviousindicationsofslopeinstabilityonthesite.However,theresolutionofthephotographislow.•1998-Thisblackandwhitephotographindicatesthatthecurrentresidenceexists,alongwithvegetatedgardenareas(rhododendrons?),andtheslopetothewestisvegetatedwithwhatappeartobedeciduoustreesandshrubs.Amultifamilyresidentialdevelopmentislocatedbelowtheslopetothewest.Therearenoobviousindicationsofslopeinstabilityonthesite.However,theresolutionofthephotographislow.•2000-Thiscolorphotographindicatesnonoticeablechangesfromthe1998photograph.Thecoloringsuggestsbothdeciduousandevergreentreesarepresentontheslope.Therearenoobviousindicationsofgroundwaterseepage,erosion,orslopeinstabilityonthesite.However,aswiththe1998photograph,theresolutionofthephotographisrelativelylow.•2002-Theresolutionofthisphotographisgoodincomparisonwiththe1998and2000photographs.Thiscolorphotographindicatesnoobviouslynoticeablechangesfromthe2000photograph.Bothevergreenanddeciduoustreesarepresentonthewesternslope.Therearenoobviousindicationsofgroundwaterseepage,erosion,orslopeinstabilityonthesite.•2005,2007,and2009-Theresolutionofthesephotographsisgoodincomparisonwiththepreviousphotographs.Thesecolorphotographsindicatenoobviouslynoticeablechangesatthesubjectsitefromthe2000or2002photographs.Theresidentialplattotheeastofthesubjectsitewasconstructedduringthistime,alongwithanimprovedSE80thStreetsegmentleadingtotheeastofthesite.Therearenoobviousindicationsofgroundwaterseepage,erosion,orslopeinstabilityonthesite.•2012and2013-The2012photographappearstohavebeentakeninearlyspring,andmanyofthedeciduoustreesarebare,allowingforasomewhatbetterviewtotheforestflooralongtheslopestothewestofthesubjectsite.The2013photographincludesfullyleafeddeciduoustrees.Therearenoobviousindicationsofgroundwaterseepage,erosion,orslopeinstabilityonthesite.May26,2016;RevisedJune7,2016ASSOCIATEEARTHSCIENCES,INCJPMd—KE160152A3—Pmjects2O16OIS2KEWPPage3 RhododendronRidgeGeologicDocumentReviewNewcastle,WashingtonandSiteReconnaissanceTopography/GeomorphologyThetopographicmapsandLIDARimageryavailableoniMAPindicategentlytomoderatelyslopingterrainwithinthesubjectsite,andmoderatelytosteeplyslopingterraintothewest.BasedonourreviewoftheLIDARimage,theslopesleadingupwardfromtheareaofLakeWashingtontotheuplandencompassingthesubjectsiteincludeseveralbowl-shapedslidefeatures,includingtotheimmediatenorthandsouthofthesubjectsite.ThesefeaturesareshowninFigure1.However,basedonourreviewoftheabove-mentionedaerialphotographyandtheconditionsobservedduringoursitereconnaissance,itisouropinionthatthelandslidescarpssuggestedbytheLIDARimageneartothesubjectsitelikelyoriginatedintheancientpast,possiblyduringtheloweringoflakelevelsattheconclusionoftheVashonStadeoftheFraserGlaciation.Geology/GroundWaterThepublishedgeologicandsoilsliteraturereviewedduringthisphaseofourstudyincludesthefollowing:•GeologicMapofKingCounty,Washington,byDerekB.Booth,KathyA.Troost,andAaronP.Wisher(2006).•“GeotechnicalEngineeringStudy—RhododendronRidge”,EarthSolutionsNW,LLC(EarthSolutions),January29,2015.•“PreliminarySubsurfaceFindings”memorandum,AssociatedEarthSciences,Inc.(AESI),August6,2015.Accordingtopublishedgeologicmapandliteratureofthearea,thesiteisunderlainbyVashonlodgementtill(Qvt).TheQvtwasdepositeddirectlyfrombasal,debris-ladenglacialiceduringtheVashonStadeoftheFraserGlaciationapproximately12,500to15,000yearsago.Thehighrelativedensityoftheunweatheredtillisduetoitsconsolidationbythemassiveweightoftheglacialicefromwhichitwasdeposited.Thisverydensematerialisgenerallyconsideredsuitableforsupportoflighttoheavilyloadedfoundationswheninanintact,undisturbedcondition.Exposuresofpre-Frasersediments(Qpf)aremappedatthedownslope,westernportionoftheSE80thiStreetright-of-way.The2015EarthSolutionsreportincludedexplorationtestpitscompletedatthesubjectsite.Insummary,theEarthSolutionstestpitsencounteredsoilsdescribedasglacialtillatthesouthernportionofthesite,andsandiersoils,describedasglacialoutwashinthereporttext,atthenorthernportionofthesite.Anexplorationboringadvancedtoadepthof81.5feetwasMay26,2016;RevisedJune7,2016ASSOCIATEEARTHSCIENCES,INC.JPMd—KE26015243—Projects\2O16O1S2KE\WPPage4 RhododendronRidgeGeologicDocumentReviewNewcastle,WashingtonandSiteReconnaissanceobservedbyAESIatthenorthwestcornerofthesite.Theexplorationboringdescribedinthe2015AESImemorandumencounteredmaterialssimilartothatdescribedintheEarthSolutionsreporttoroughly13feetoverlyingverystifftohardsiltandclay.Thesesiltswereinterpretedaspre-Vashonglaciomarinesilts,possiblyofPossessionage,similartothepre-Frasersedimentsshownonthereferencedgeologicmap.Thesiltdisplayedafewfractures,althoughthedegreeoffracturingcanbevariable.Ourreviewoftheabove-mentioneddocumentssuggeststhatgroundwaterseepageacrossmuchofthesiteisanticipatedtobelimitedtointerflow.Interfiowoccurswhensurfacewaterpercolatesdownthroughthesurficialweatheredorhigher-permeabilitysedimentsandbecomesperchedatopunderlying,lower-permeabilitysediments.ThesiteislocatednearthesouthernextentofthemappedSeattleFaultZone.RecentstudiesbytheUSGS(USGS;e.g.,Johnsonetal.,1994,OriginandEvolutionoftheSeattleFaultandSeattleBasin,Washington,Geology,v.22,pp.71-74;andJohnsonetal.,iggg,ActiveTectonicsoftheSeattleFaultandCentralPugetSoundWashington-ImplicationsforEarthquakeHazards,GeologicalSocietyofAmericaBulletin,July1999,v.111,n.7,pp.1042-1053)haveprovidedevidenceofsurficialgroundrupturealonganorthernsplayoftheSeattleFault.Therecognitionofthisfaultsplayisrelativelynew,anddatapertainingtoitarelimited,withthestudiesstillongoing.AccordingtotheUSGSstudies,thelatestmovementofthisfaultwasabout1,100yearsagowhenabout20feetofsurficialdisplacementtookplace.Thisdisplacementcanpresentlybeseenintheformofraised,wave-cutbeachterracesalongAlkiPointinWestSeattleandRestorationPointatthesouthendofBainbridgeIsland.Therecurrenceintervalofmovementalongthisfaultsystemisstillunknown,althoughitishypothesizedtobeinexcessofseveralthousandyears.Duetothesuspectedlongrecurrenceinterval,thepotentialforsurficialgroundrupturealongtheSeattleFaultZoneisconsideredtobelowduringtheexpectedlifeoftheproposedstructures.RESULTSOFSITERECONNAISSANCEAnAESIengineeringgeologistperformedareconnaissanceofthesiteonMay3,2016.Thepurposeofourreconnaissancevisitwastoprovideavisualevaluationofthesiteconditions,includingtopography,drainage,geology,hydrology,andvegetation.Ourobservationsofthesiteconditionsduringoursitereconnaissanceareingeneralagreementwithsiteconditionssummarizedfromourliteratureresearchpresentedabove.Sitetopographyvariesfromlowreliefintheareaoftheexistinghouseonthesubjectsitetomoderatelysloping,withlimitedareasofsteeply(greaterthan40percent)slopingground,intheareasoftheSEg0tLStreetright-of-wayandthepropertytothewestofthesubjectsite.TopographicreliefalongtheportionoftheSEg0thStreetright-of-wayfromthesubjectsiteto110thAvenueNEisaboutMay26,2016;RevisedJune7,2016ASSOCIATEEARTHScIENCES,INCJPMd—KE160152A3—Projects2O16OI52KE;WPPage5 RhododendronRidgeGeologicDocumentReviewNewcastle,WashingtonandSiteReconnaissance160feet,slopingdowntothewest.Theareaofthesitesurroundingtheexistingresidenceisvegetatedwithlandscapingshrubbery,includingmanyrhododendrons,andsmall-tomedium-sizedtrees,andlarge(upto42inchesindiameter)evergreentrees.Theslopingareatothewestofthesubjectsiteisvegetatedwithabundantferns,brush,andmixeddeciduousandevergreentreesupto3feetindiameter.Thesizeandnatureofthesetreessuggeststhattheslopehasbeeninitscurrentconfigurationforsometime.AseriesofmanholecoverswereobservedatthegroundsurfacealongtheSE80thStreetright-of-way,suggestingthatutilityinstallationactivitieshavepreviouslybeencompleteddownthisslope.Nogroundwaterseepagewasobservedontheslopeatthetimeofoursitevisit.CONCI.USIONSANDRECOMMENDATIONSTheslopingareapresenttothewestofthesubjectsiteandtheSEg0thStreetright-of-waydonotshowevidenceofrecentdeep-seatedlandsliding.Inouropinion,theslopeshouldnotbeadverselyaffectedbytheproposedimprovements,includingtheproposedsurface-mountedHDPEstormwaterpipeleadingdowntheSEgQthStreetright-of-way,usingcurrentengineering,architectural,andplanningstandards.Basedonreviewofavailablepublishedgeologicinformation,itappearsthatsitesoilsshouldbesuitabletosupporttheanticipatedHDPEstormwaterpipe.Inaddition,theproposedstormwaterdetentionanddischargesystemwillineffectremoveaportionofstormwatervolumefromanareaabovethetopoftheslopingground,reducingtheriskofsaturationoftheslopeduetorunofffromupgradientlocationsduringorsubsequenttosignificantrainfallevents.Itisouropinionthattheriskoflandslidesorslopeerosionposedbytheproposedimprovementsislowforthesiteprovidedcurrentengineeringstandardsandtherecommendationscontainedthisletterarefollowed.Thesteepslopesattheareaofthesitewerepredominantlyvegetatedwithferns,otherbrushandtrees.Thisvegetationservestoprotectthefaceoftheslopesfromsoilerosion.Werecommendthatthisvegetationremaininplacetoproviderootsupportforthenear-surfacesoilsalongtheslopes.Stormwaterrunofffromimpermeablesurfacesshouldbecollected,routed,anddischargedthroughaproperlydesignedstormwatersystem.Uncontrolleddischargefromtheimpermeablesurfacesshouldnotbeallowedtoflowtowardsorontothesteepslopes.May26,2016;RevisedJune7,2016ASSOCIATEEARTHSCIENCES,INC.JPV(d—KEIGOIS2A3—Profeas\20160152\KE%WPPage6 RhododendronRidgeNewcastle,WashingtonCLOSUREGeologicDocumentReviewandSiteReconnaissanceThisassessmentisbaseduponvisualobservationofexistingsiteconditionsasallowedbycurrentvegetativecover,reviewofhistoricaerialphotographs,andpastdocumentspreparedbyAESIandothersforthesiteandissubjecttotheinherentlimitationsofthesemethods.Shouldyoudesirethatacomprehensiveriskassessmentbeperformed,additionalresearch,exploration(includingexplorationborings),andevaluationbyourfirmwouldbeneeded.Itshouldbenotedthatlivingadjacenttoasteepslopeisalwaysarisk,andthattheslopemayfail(orcontinuetoslowlyerode)inthefutureduetonaturalcauses.Reductionofpotentialslopehazardsusingslopesetbacksandcontrolofwatercanbecost-effectivesteepslopehazardmitigations.JeffreyP.-iáb,L.G.,LE.G.SeniorProjectEngineeringGeologistAttachments:Figure1-Lidar-BasedTopography-LandslideScarpsMay26,2016;RevisedJune7,2016iPijid—K6160152A3—Projqct,2O16Q152KE\WPASSOCIATEEARTHSCIENCES,NCWehaveenjoyedworkingwithyouonthisevaluation.questionsorifwecanbeofadditionalhelptoyou.Sincerely,ASSOCIATEDEARTHSCIENCES,INC.Kirkland,WashingtonPleasecontactusifyouhaveany..L.•Ih.F:L:‘(‘,eCuftisi.Koger,L.G.,L.E.G.,SeniorPrincipalCeologist/HydrogeologistBruceL.Blyton,P.ESeniorPrincipalEngineerPage7 ‘\\‘41‘.I%——,-.‘\—(I4ki.jrII‘K—‘-1’-*ZkL_//)/C--,—ipfr-—----;k.ij\)\1/‘3ih1ø/‘r(‘,Wê,&*1’Aw,7’__LJ’p4fr.War1ach*—c4.r.r..C.A--...I—..—iI-..r71•I:1--I—LEGEND:SIT!LANDSLIDESCAR?CONTOUR5FT‘N..CONTOUR20FtSTREETIIAIt[DATA5JRCE5AEFERENCES:UCARAGUIR!DAYPSLCCRIDCEaEEEIEFWASTATEPLMEICRTECOO2IATrEThTEN.NADAICTEAIHARNI.aEWTIoNENITSIlUSSIWWYFEET.NLNGC0ET1EETS,WATERPMCaStDCATICNEANDCITMIESISHCW?IAAEffiOXTMATEA500FmEUCKANOAAIETEAIMXIJCTIDIAFflhlicaDAFflrCThfAII225IIA!2•ICTIATflEFITO4a,soclaled.iartbsc’oncoiLIDARBASEDTOPOGRAPHYLANDSLIDESCARPSRHODODENDRONRIDGENEWCASTLE.WASHINGTONPROJNOIDAIr:-.-—IFIGURE, noccwotEtcZorn•I‘IS..,0zLU(3LU-J‘ILUSz AflAMtmannOliverAssociates,LLCAUAI—qfH)Box7SLr,iaiiin,,\V\9S1)Il(Wiii:(J5)33%fl%5Fix(12T)33%—flU’)EnvironmentalPlanning&I.andscapcAtchitectureDecember28,2016AOA-5136JillRouftGoldsmithLandDevelopmentServices1215—114thAve.SEBellevue,WA98004SUBJECT:StandardStreamStudyforRhododendronRidgeStormExtensionCityofRenton,WAFileNo.PRE16-000137DearJill:1.0INTRODUCTIONThisreportistheresultofawetlandandstreamreconnaissanceconductedalongtherouteofaproposedstormlinefromtheRhododendronRidgeShortPlatlocatedat11230SE80thStreetwithintheCityofNewcastle.ThisstormlinewouldbeconstructedwithintheSE80thright-of-wayandwoulddirecttreatedstormwaterrunofffromthesubdivisiontoapublicstormwatersystemownedbytheCityofRentonlocatedwithintheright-of-wayofLincolnAvenueNE.2.0GENERALPROPERTYDESCRIPTIONANDLANDUSETheSE80thStreetright-of-wayinthevicinityoftheproposedstormextensioniscurrentlyunimprovedexceptforasanitarysewerlinethattraversestheentireright-of-way.Theright-of-wayslopesmoderatelytosteeplydownfromeasttowestandconsistsofmixeduplandforestinterspersedwithareasofmowedlawn.3.0METHODOLOGYPriortoconductingthesitereconnaissancethefollowingmappingsystemswerereviewed:•WashingtonDepartmentofFishandWildlife’sSalmonscape•WashingtonDepartmentofNaturalResources’FPARSmapping•WashingtonDepartmentofFishandWildlife’sPriorityHabitatsandSpeciesMapping•CityofRentoncriticalareamapping•KingCountyiMAPEXHIBIT4 JillRouttDecember28,2016Page2OnMay25,2016IconductedawetlandandstreamreconnaissanceonthesubjectpropertyutilizingthemethodologyoutlinedintheMay2010RegionalSupplementtotheCorpsofEngineersWetlandDelineationManual:WesternMountains,Valleys,andCoastRegion(Version2.0).4.0RESULTSNoneofthecriticalareamapsreviewedindicatedanywetlandsorstreamslocatedonthesubjectproperty.TheCityofRentoncriticalareamappingdoesindicateaTypeFstreamandwetlandlocatedoff-sitetothesouth.Atthetimeofthefieldinvestigation,thesiteconsistedmostlyofamixeduplandforestthatslopesmoderatelytosteeplydownfromeasttowest.Vegetationincludedacanopyofbig-leafmaple(Acermacrophy!Ium),blackcottonwood(Populustrichocarpa),Douglasfir(Pseudotsugamenziesii,westernredcedar(Thujaplicata),andredalder(Alnusmbra).Commonlyobservedunderstoryandgroundcoverspeciesincludedhazelnut(Conjluscomuta),salal(Gaultheriashallon),tallOregongrape(Mahoniaaquifolium),Himalayanblackberry(Rubusarmeniacus),swordfern(Polystichummunitum),brackenfern(Pteridiumaquilinum),Englishivy(Hederahelix),Indianplum(Qemleriacerasiformis),snowberry(Symphoricarposalbus),andtrailingblackberry(Rubusursinus).Thesouthwesternportionofthesiteconsistedofamowedandmaintainedlawnassociatedwiththeoff-siteresidencetothesouth.Inaddition,amowedcorridorofgrassesextendsuptheslopewithintheright-of-wayadjacenttheexistingsanitarysewerline.Nohydrophybcplantcommunitieswereobservedonorimmediatelyadjacenttothesiteduringthereconnaissance.Boringstakenthroughoutandadjacenttheundisturbedportionsofthesiterevealedhighchroma,non-hydricsoilsandtherewasnoevidenceofpondingorprolongedsoilsaturation.Soilswithintheimmediatevicinityofthesanitarysewerlinewerehighlydisturbedandlikelyconsistofrelicback-fillplacedduringhistoricinstallationofthesewerline.4.1Off-siteStreamOnestreamwasobservedoff-sitetothesouthwest.Thestreamwithintheclosestproximitytothesiteislocatedwithinaditchedchannelalongthenorthsideofthedrivewaytotheexistingresidenceat4348LincolnAve.NE.Runoffwithinthestreamentersanon-fishpassableconcreteculvertunderLincolnAveNE.Althoughthestreamdoesnotcurrentlyappeartosupportsalmonids,itismyunderstandingthattheCityofRentonhasclassifiedthisstreamasaTypeFchannelduetothestreamspotentialforfishuse.TypeFstreamsrequireastandard115-footbufferperRMC4-3-050.G.2.ThisbufferextendsintothesouthwestportionoftheSE80thStreetright-of-way. JillRouttDecember28,2016Page34.2MappedOff-siteWetlandThepotentialoff-sitewetlandtothesouthasmappedontheCitymappingsystemwasnotobservedandappearstobemis-mapped.Thismis-mappingisconsistentwithawetlandandstreamreconnaissanceIrecentlyconductedonParcel334570-0020locatedfurtheroff-siteinwhichthesamemappedstreamwasobservedbuttherewasnolargewetlandsystemontheparcelasdepictedontheCitymapping.5.0HABITATASSESSMENTTheWashingtonDepartmentofFishandWildlife’sPriorityHabitatsandSpecies(PHS)databasedoesnotindicatethepresenceofanythreatened,endangered,sensitive,monitored,orpriorityhabitatsorspeciesonoradjacenttotheproperty.Whilethesitedoeslikelyprovidehabitatforavarietyofwildlifespeciestypicallyfoundwithinsuburbanenvironments,nothreatened,endangered,sensitive,monitored,orpriorityspecieswereidentifiedonoradjacenttothesiteduringthefieldinvestigations.AsdefinedinRMC4-11-030.C,CriticalHabitatisanareaassociatedwiththreatened,endangered,sensitive,monitored,orpriorityspeciesofplantsorwildlifeandwhich,ifaltered,couldreducethelikelihoodthatthespecieswouldmaintainandreproduceoverthelongterm.Sincenocriticalhabitathasbeenidentifiedonthesite,noHabitatDataReportisrequired.6.0PROPOSEDPROJECTIPACTSTheproposedstormlinehasbeendesignedtoavoidalldirectimpactstocriticalareas.Tofurtherminimizeimpactstowildlifeandsignificantvegetation,thepipewouldbeinstalledwithintheexistingmaintainedareas.Althoughcrossingthebufferfromtheoff-sitestreaminthesouthwesterncornerofthepropertyisunavoidable,thestormlinewouldbeinstalledwithinthemowedlawnportionoftheright-of-wayandwouldthereforenotrequiretheremovalofanysignificantbuffervegetation(Figure1).Allofthetemporarydisturbancewithinthebufferwillbefullyrestoredbyseedingwithnativegrassfollowinginstallationofthestormline. JillRouttDecember28,2016Page4Ifyouhaveanyquestions,pleasegivemeacall.Sincerely,ALTMANNOLIVERASSOCIATES,LLCJohnAltmannEcologist I - -Z-’.‘Th-t LIMITS/EDSOP I I —— ENl9rINë VEGETATiON ---.- ‘-.:--.-;;:z C r”LOCATIONOFTIPEF :-,.‘— -“/SWEAHDIGITIZEDFROMIHAP H - --,‘:i.:’’’’’’-’.’.,’_—_ .I.:; ‘‘I 4 ———if I —————— I ‘-- F 11.I - I - --%I --, I t//.’’,,/‘**\‘.U /;,:‘,- --.‘‘\‘.r,flZ -uJzzI N fluO GRAPHIC SCALE goo PLAN LEENO (IN FEET)7tN —--——-—PROPERTh’LINE /I \ -LOCATION OF ORDINARY H1G14 RAJER OF I TrPEFSTREAH 0 30 60 10-120 Iso 115 SUFFER SCALE ISO —‘—‘—“CLEARiNG LIMITS ‘—Th EDGE OF EXISTING VEGETATION I:nJ’iP0RARY IMPACTED SUFFER -TO SE RESEEDED Him RED FESCUE AT A RATE OF NOTES S’I/IpOO SF -4335 SF I.BASE INFORMATION PROVIDED BY GOLDSMITh,1215 114Th AVE.SE, SELLEVUE,I-tA q5004,(425)462-1060. 2.PRIOR TO EXCAVATION,EXISTING TOPSOIL TO SE CLEARED TO ON SIDE OF CLEARING LIMITS AND STOCKPILED FOR LATER REPLACE}€NT.UTILITY LINE TO SE EXCAVATED,LINE 0 INSTALLED AND SACK FILLED PER CIVIL PLAN.TOPSOIL TO BE REPLACED TO WRPACE AND SEEDED 1-11TH RED FESCUE. A RhododendronRidgeStormExtension11lWAveSESEDecember28,2016—AlSalmonScapeSpecies1:9,02800.0750.150.3miI•‘I’00.10.20.4kmSaimas:Esri,HERE.Lare,Inl&nnp.ñcmmaMPCa,GEBW,USGS,FAG,NPS,NRCkrGeoBe,ION.KadasterNLOrà,anceSwvey,EsdJan,ft€11,EsriCHris(HaigKonajsw’ast,Mapmylndà,©0penStma.lapccnfribits,andthe015Us&ComLsiityiDFW03tU31))..[JE48thSi-1.3.1’rsc—SEJ6LhSt.,..UiLfl123:3,If-.4a=Si:ISiNsHS’sISiteIrit]1232C4SIIii7%/n03-SE307ft&IhSI....(‘3PrtveHGSE82’.dStV0SE83rdHH&4L1hStUiInSE32tSi 12128/2016ForestPracticesApplicationMappingTool(FPAMT)ForestPracticesApplicationMappingTooIDataActive(17)j[LegendISearchforLayersActivityMap0TownshipsoISectionSurveyLinesVo1]MapRegistrationTicsVoWaterTypeBreakVØ:flRoads0JTrailsandRailroadsDNRHome(http://www.dnr.wa.gov/)FPARSHome(http://www.dnr.wagov/programs-and-services/forest-practiceslforest-practiceand-board-manual-guidelines)FPManual(h0dWatershedAnalysis WDFWTestMapSE76thSt0aOeegzi‘:-,:4‘4t9•%.‘‘r‘1NE36thSINE35thPtif:“Hif,’n1:19,8420.150.30.6miIII00.2750.55Sauces:Es&HEFE,DtrTm,USGS.Irdermap,INCREMENTP,MCan,EarlJaapn,ETI,EadChha(HaigKcng),CadKwea,Earl(Thrdlard),1ndSt/Sr€sCG’thSSE72n.JStSE73rdjS--b42ndVIr.‘3Sf:SitsstDecember28,2016PHSReportClipAreaPOLYPTASMAPPEDSECTIONDQTR-TWPTOWNSHIP1.1km—LN r-r r a.. 4 a rr Hr..] .7— .1h1 The hbrnaanhcbjdedonlhs m ts bei canpiedby KngcalysWf&twn a aiely ci earns a,dissotect In cIre ‘eithaiIndi.Ing Corny mrex ro mxrzortaa,sorvar,arte.express orienFlied.as U Jmcy,&enriSexs.IhieIns, rIt In We [soot mflr inkjrnebai.Tlisdo,j,ml i rd irerried use [sa &ney rmlIt I(irq Cjrty si1 not Iate Ia arIyga1B,spoc,nd,el.ircicNatorrxrmersenbaI datex tuthq.(UI rd IñiithdU IosIrr.eruexorbslprofib rusdtrg fran the LS8 msjso cite irt,mcibn ccs*ared ‘Ti Sic nw.Myso of the map orinbinaononIt nap Li p*bi1&acefl by wnllcai pwnsw,of )Vrq Cwny. King County GIS CENTER Rhododendron Ridge Storm Extension IT, 4 14 :1 i ‘4*4,-CityofRentonPrintmapTemp’ateNotesLegendNoneCityandCountyBoundary—TypeSOtherTypeF!CryofRent—TypeNpI3AddressesTypoNoParcelsElWetlandsErMronmentDesignations:-INatural128064128FeelDShorelineHighIntensityWGS_1984_Web_Mercator_Auxiliary_SphereDShoretnoIsolatedHighIntensityF•iShorelineResidentialsiReiftontFinance&ITDivisionInformationTechnology-015•rhismapisaunc,generatedstaticoutpulfromanInternetmappingsiloendaforielcrcncoocly.DiitalayernhatappearonthismapmayornicymidbeRentonMapSuppoftRentonwa.govacr.urnla.curreni,orcibenvisi,rnlrable.4122/2016THISMAPISNOTTOBEUSEDFORNAVIGATION