REcEIVEDJUN132Q11STATEOFDELAWAREEPA.REGIONIIIOFFICEOFTHEGOVERNOROFFICEOfREGIONALADMINISTRATORTATNALLBUILDING,SECONDFLOORJACKA.MARKELLWILLIAMPENNSTREET,DOVER,DE19901P1IoNI:302-744-4101GOVERNORFAx:302-739-2775Mr.ShawnMGarvin(3RAOO)RegionalAdministratorRECElvpRegionIIIU.S.EnvironmentalProtectionAgencyJUN1420111650ArchStreetPhiladelphia,PA19103-2029DivisionDirector(3APOO)DearAdministratorGarvin:OnJune2,2010,theU.S.EnvironmentalProtectionAgency(EPA)strengthenedtheNationalAmbientAirQualityStandards(NAAQS)forsulfurdioxide(SO2)byaddinganew1-hourprimarystandardof75partsperbillion(ppb)(3-yearaverageofthe99t1percentiledailymaximum1-hourconcentration).Section107(d)oftheCleanAirAct(CAA)requirestheGovernorofeachStatetosubmittotheEPAalistofallareas(orportionsthereof)intheState,designatingeachasnonattainment,attainment,orunclassifiable.ThisletterfulfillsDelaware’sobligationsunderSection107(d)oftheCAA.AreaDescriptionandMonitoringDataDelawareiscomposedofthreecounties,namelyNewCastle,KentandSussex,layingfromnorthtosouth.ThenorthernportionofNewCastleCountyliesabovetheChesapeakeandDelawareCanal,awaterwaythatconnectstheChesapeakeBaywiththeDelawareBay.ThispartofNewCastleCountyismoremetropolitanandindustrializedthantheremainderofDelaware.TheremainderofDelawareliessouthoftheChesapeakeandDelawareCanal,andcomprisesthesouthernportionofNewCastleCounty,andallofKentandSussexCounties.DelawarecurrentlymonitorsSO2atitsWilmington,Bellefonte,SummitBridge,andDelawareCitymonitoringsites,whicharealllocatedinNewCastleCounty.ThemeasuredambientSO2concentrations(1-houraverage,99t1percentile)for2007through2009’atthreeofthesemonitorsareshowninthetablebelow.SummitBridgedataisnotincludedduetoincompletedata,andthefactthatithashistoricallyrecordedthelowestSO2concentrations.99thpercentile1-houraverage(ppb)3-yearaverage(ppb)Site2007200820092007-2009Bellefonte69604156.7MLK/Wilmington58573048.3DelawareCity41512840.012010datahasnotundergonequalityassuranceandisincompleteatthistime.Mi.ShawnMGarvin(3RA00)May11,2011Page2DelawareunderstandsthatunderthisnewNAAQSwewillberequiredtoinstallandoperateanadditionalSO2monitorinSussexCounty/SeafordMSA,tobeoperationalbyJanuary1,2013.OncethisisdoneourSOmonitoringnetworkwillbecomplete.Attainment/NonattainmentRecommendationThedesignationapproachunderthisnewSO2NAAQSusesbothairqualitymonitoringandmodelinginformation.EPA’sMarch24,2011guidanceindicatesthatStatesshouldidentifyareasasattainment,nonattainmentorunclassifiableonthebasisofavailablemonitoringandmodelingmforniation.Basedonavailablemonitoringandmodelinginformation,DelawarerecommendsthateachofitsthreeDelawarecountiesbedesignatedas“unclassifiable”forthe75ppb1-hour°2NAAQs.•Delawarehasnoavailablemonitoringormodelinginformationthatsupportsanonattainmentdesignation.•Delaware’sexistingSO2monitoringnetworkisnotsufficienttosupportanattainmentdesignation.•Delawarehasnotcompletedalloftheairdispersionmodelingnecessarytosupporteitheranattainmentornonattainmentdesignation.ThisrecommendationisconsistentwiththeEPAexpectationoutlinedintheStephenD.Page,Director,EPAOfficeofAirQualityPlanningandStandards,March24,2011memorandum,“AraDesignationsforthe’2010RezisedPrimzrySulfiirDiaddeNationalAniientAirQualityStandrth.”Thismemorandumstates,“Gizitheam1ylinitedr’tzeokofSO2nvnitom,andcxtrexjmationthatstatesui/inot)ethazecoiçktedappivpriatenix/dingfa11sigificantSO2scwzrs,ueantiapawthatnxtawas(ftmtiyui/i/asignated‘mdassy9ableThankyouforyourconsiderationofthisrecommendation.Ifyouhaveanyquestionsconcerningthissubmittalorwouldliketodiscussitfurther,pleasecontactMr.AllMirzakhahui,P.E.,theDirectorofourDivisionofAirQuality;at(302)739-9402.Sincerely,JackA.MarkellGovernorpc:CoffinO’MaraDaveSmallAllMirzakhaliuiDianaEsher