rJ9(ySTATEOFDELAWAREDEPARTMENTOFNATURALRESOURCES&ENVIRONMENTALCONTROLDIVISIONOFAIRQUALITY655S.BayRoad,Suite5NDOVER,DELAWARE19901July11,2011ShawnM.Garvin(3RAOO)RegionalAdministratorUnitedStatesEnvironmentalProtectionAgencyRegionIII1650ArchStreetPhiladelphia,PA19103-2029DearMr.Garvin:InlateJulyandAugust2010,fallentreescausedcompletepowerlossandsignificantdown-timeattheDelawareBrandywineairmonitoringstation(AQSID10-003-1010).AnextendedpoweroutageresultedinnovaliddatabeingcollectedfromJuly21throughAugust20,2010.OthermiscellaneousissuesresultedinsmallerdatalossonindividualdaysinMayandJune2010.Theresultingtotalvaliddatacapturefor2010atBrandywinewas85%.Previousyear’sdatacapturewas95%for2008and79%for2009,forathreeyearaverage2008-2010of86%.Section2.3(b)ofAppendixIto40CFRPart50requiresthreeconsecutiveyearsofdatawithdataavailabilityofatleast90%onaverage,withaminimumdatacompletenessinanyoneyearofatleast75%.Furthermore,thissectionalsostates:“...Whencomputingwhethertheminimumdatacompletenessrequirementshavebeenmet,meteorologicalorambientdatamaybesufficienttodemonstratethatmeteorologicalconditionsonmissingdayswerenotconducivetoconcentrationsabovethelevelofthestandard.Missingdaysassumedlessthanthelevelofthestandardarecountedforthepurposeofmeetingthedatacompletenessrequirement,subjecttotheapprovaloftheappropriateRegionalAdministrator.”Becausethemissingdataoccurredlargelyduringmid-summerwithassociatedhighdailyaveragetemperatures,meteorologicaldataalonewerenotsufficienttoestimatemissingdatabelowtheNAAQS.DelawarethereforeperformedacorrelationanalysisbetweentheBrandywinesiteandotherlocalregionalozonemonitorstodemonstratethatasuitablelinearregressionequationwithahighcoefficientofdeterminationcouldbeusedtogenerateestimateddaily8-hourozonemaximaforthemissingdaysin2010.TheDelawareDNRECDivisionofAirQuality(DAQ)thereforedeterminedthattheuseofthenulldatacode,“BG”,forthefollowing26daysin2010isappropriate:RECEIVEDJUL222011EPA.REGIONIIIOFFICEOFREGIONALADMiNISTRATORTelephone:(302)739-9402FaxNo.:(302)739-3106RECEIVEDJUL222011DivisionDirector(3APOO)PrintedonRecycledPaperIMr.ShawnGarvinPageTwoTheDelawareDNRECDivisionofAirQuality(DAQ)thereforedeterminedthattheuseofthenulldatacode,“BG”,forthefollowing26daysin2010isappropriate:DatesDayCount5/2115/2715/30-3126/1417/25—7/2737/29—8/9128/12—8/1658/181TOTAL26Addingthe26daystotheBrandywinedataresultsinadatacapturepercentageof97%for2010.InJuly2010,Delawarehadperformedamissingdataanalysisfor2009datafromtheBrandywinesite(DataSubstitutionAnalysis,2009Ozone,BrandywineAQSSiteID10-003-1010,DEDNREC,DivisionofAirQuality,July15,2010).Furtherreviewofthe2009ozonemonitoringdatafortheBrandywinesiteandnearbyregionalsitesindicatedthattherewereasignificantnumberofadditionalmissingdayslikelytobebelowtheNAAQS.Tosupplementtheearlieranalysis,Delawareexpandedthemeteorologicalassessmentforadditionalmissingdaysin2009.For2009,analysisofmeteorologicalconditions,precipitationrecords,andregionalozonemapsshowedthat16dayswerelikelytorepresentlowozoneconcentrationsformissingdaysattheBrandywinemonitoringsite.Inreviewingalltheprimaryandsupplementalinformation,16daysarebeingproposedbyDelawareasappropriatefortheuseofthenulldatacode“BG”aslistedbelow.2009Datesproposedforuseof“BG”5/14/20096/23/20096/30/20097/3/20097/4/20097/23/20098/6/20098/7/20098/13/20098/28/20098/29/20098/31/20099/1/200910/7/200910/9/200910/21/2009Mr.ShawnGarvinPageThreeWiththese16additionaldaysassumedtobelessthanthestandard,combinedwiththepreviouslyaccepted55days,datacompletenessforBrandywinein2009is86%.Combiningthe16additionaldaysassumedtobelessthanthestandardin2009withthe26additionaldaysassumedtobelessthanthestandardfor2010,thefinalthreeyearaveragedatacapturefor2008—2010forBrandywinewouldbe93%.Thismeetstheminimumrequirementof90%asstatedin40CFRPart50AppendixISection2.3(b).DelawareDAQhasdiscussedthisprocessanddatareviewwithAndrewHassofEPARegionIII.ThedatasubstitutionanalysisreportandrawdataonCDareattached.Arevised2009and2010DelawareDataCertificationpackagefortheupdatedozonedatawillalsobesubmittedtoEPARegionIII.PleasefeelfreetocontactBetsyFreyat302-323-4542ifyouhaveanyquestions.Sincerely,‘AuMirzahalili,P.E.DirectorEnclosurecc:ArnieHowell,EPARegionIIIWalterWilkie,EPARegionIIIAndrewHass,EPARegionIIIPaulineDevose,EPARegionIIIDavidLutz,DataCertificationContact,EPA(MailCodeC304-06)RonAmirikian,DAQBetsyFrey,DAQJoeMartini,DAQ