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ÐÌÔ#†JµZIIJ÷Ž¡#Ôà  àThis€paper€provides€guidance€for€using€information€from€photochemical€grid€modeling€andÐ !q Ðambient€air€quality€monitoring€to€estimate€additional€levels€of€emission€reductions€needed€toÏsupport€the€1„hour€NAAQS€for€ozone€beyond€the€reductions€contained€in€the€demonstrationsÏsubmitted€by€the€States€in€1998.€€Procedures€for€estimating€improvements€expected€with€theÏimplementation€of€the€Tier€2€low€sulfur€program€and€benefits€towards€attainment€are€also€provided.€ÏTwo€techniques€are€described€for€estimating€additional€emission€reductions,€each€with€its€ownÏstrengths€and€weaknesses.€Use€is€made€of€the€fact€that,€since€1999€is€more€than€half„way€from€theÏmodel€base€year€(1990)€to€the€attainment€year€(2005€or€2007€in€most€areas),€air€quality€data€fromÏ1990€to€1999€allows€modelers€the€opportunity€to€determine€the€representativeness€of€the€modeledÏpredictions.Ô‡J÷ŽIIJµZÔ€€Ô#†JµZIIJ÷ŽÖ#ÔÔ‡XF!XIJµZÔÔ‡XÈåXXXF!ÔThese€techniques€identify€the€additional€percentage€reduction€in€NOx€and€VOCÐ d´ Ðfrom€the€1990€emissions.€€€Ô#†XF!XXXÈå9#ÔÔ#†JµZIXXF!#ÔÔ‡XF!XIJµZÔÐ c³ ÐÌò òGeneral€Procedures€for€Improving€Weight€of€Evidence€Through€Identification€ofÐ I!™ ÐAdditional€Emission€Reductions,€Not€Modeled,€Including€Tier€2.ó óÐ :"Š ÐÌà  àTo€strengthen€the€weight€of€evidence€and€account€for€high€modeled€peaks,€estimateÏadditional€measures€that€at€a€minimum€bring€the€model€estimated€future€design€value€to€124€ppbÏor€below.€€This€is€done€by€first€estimating€a€future€design€value€using€the€model€predicted€peaks.€€ÏMultiply€the€base€design€value€by€a€ratio€(average€of€model€predicted€peaks€(across€all€days),Ïafter€controls€divided€by€before€controls).€€The€base€design€value€is€an€average€of€three€years€ofÏmonitored€design€values€that€represent€the€modeled€base€case€emissions.€€If€the€model€estimatedÏfuture€design€value€is€at€or€below€124€ppb,€additional€emission€reductions€should€not€be€needed.ÌÌà  àIf€the€model€estimated€future€design€value€is€greater€than€124€ppb,€estimate€additionalÐ ¤+ô&) Ðmeasures€by€using€two€ratios€1)€modeled€change€in€design€values€to€modeled€change€inÏemissions€and€2)€air€quality€design€value€changes€to€NET/local€emissions€changes€between€twoÏreference€years€(e.g.,€1990€and€1996).€€Do€not€include€biogenic€emissions.€€First,€subtract€124Ïppb€from€estimated€future€design€value€to€identify€additional€ozone€reduction€needed.€€ThenÏmultiply€each€ratio€by€the€ozone€reduction€needed€to€estimate€additional€VOC€and€NOx€emissionÏreductions€needed€to€strengthen€the€weight€of€evidence€argument€for€attainment.€€This€results€inÏthe€additional€percent€reduction€needed€from€the€1990€emissions.ÌÌà  àTo€calculate€the€level€of€emission€reductions€needed€(in€tons€per€dayÔ#†JµZIXXF!#ÔÔ‡XF!XIJµZÔ)€multiple€the€1990Ð 8 ˆ Ðbase€emissions€by€the€percent€reductions.€€This€results€in€the€total€tons€per€day€reduction€whichÏare€additional€reductions€needed€in€the€attainment€year.€€To€incorporate€the€impact€of€Tier€2Ïsubtract€the€emission€reduction€estimates€being€applied€towards€attainment€for€Tier€2€from€theÏadditional€reductions.€€The€remaining€reductions€may€be€adjusted€to€reflect€other€unmodeledÏcontrol€measures€which€have€been€quantified.€€The€following€are€more€details€of€the€proceduresÏwith€examples.à ¸ àÔ#†JµZIXXF! #ÔÐ Þ.  ÐÔ€XF!XIJµZÔò òÌEstimating€Additional€Emission€ReductionsÌÌó óà  àEach€of€the€ò òó ómethods€described€in€the€remainder€of€this€paper€begins€with€a€monitoredÐ ¢ò Ðozone€concentration€which€can€be€extrapolated€to€the€attainment€year€and€compared€with€theÏstandard.€€€If€the€attainment€year€concentration€is€over€124€ppb,€the€methods€described€in€thisÏpaper€can€be€used€to€estimate€what€would€constitute€additional€emission€reductions€needed€toÏsupport€a€weight€of€evidence€argument€for€attainment.€€The€differences€among€the€methods€lie€inÏthe€factors€used€for€this€extrapolation.€€These€are€summarized€in€Table€1.ÌÌÔ‡ XÈåXXXF!Ôà  àBoth€methods€are€based€on€the€assumption€that€we€can€estimate€the€relationship€betweenÐ 9‰ Ðozone€and€its€precursors€(VOC€and€NOx).€€We€can€estimate€this€relationship€by€either€(1)Ïcomparing€changes€in€model€predicted€ozone€to€changes€in€modeled€emissions€or€(2)€comparingÏchanges€in€observed€air€quality€to€changes€in€actual€emissions.€€Both€methods€for€estimating€aÏrelationship€are€equally€valid.€€Both€have€inherent€uncertainty€in€estimates€of€emissionsÏinventories€and€estimates€of€the€change€in€ozone€air€quality.€€Utility€of€either€method€isÏdependent€on€the€availability€of€data€which€shows€a€response€in€ozone€due€to€a€decrease€in€VOCÏand€NOx€emissions.€€For€example,€if€an€area€wants€to€apply€method€2€using€the€NET€inventoriesÏfor€the€1990€and€1996€reference€years,€the€VOC€and€NOx€totals€for€the€nonattainment€area€mustÏshow€a€decrease€in€VOC€and€NOx€between€1990€and€1996.€€If€this€is€not€the€case€then€use€of€theÏNET€data€for€those€two€reference€years€in€not€appropriate.Ô#†XF!XX XÈå#ÔÐ Ë%!# ÐÌò òÐ  ±'#% ÐTable€1.€€Summary€of€Methods€for€Estimating€Additional€Emission€Reductions€ó óÐ ° ÐÌÔ*‹ƒ&ddd Xdd Xdd X°(#°(#‹ÔÔ,„dd"ÔÔ,/ dd ÔÔ,Å dd ÔÔ+  ÔÐ *€jy ’â „„*ÐMethodÐ öF ÐÐ A€jy,!ç7"jy „„AÐOzone€Concentration€BeingÏExtrapolatedÐ A€jy,!ç7"jy „„AÐExtrapolation€RatioÐ öF Ð(normalized€reduction€factor)Ð LB!ç7"jy  ð?1‰ð?‰LÐ1Ð 4*(g ·   ð?1 ð? 4ÐFuture€Air€Quality€Design€ValueÐ  g ·  Ѐ€€€€€€Change€in€modeled€emissionsòòÐ g ·  Ðóó€€€òò€€€€€From€base€to€attainment€year€€€€Ð X ¨  Ðóó€€€€Change€in€modeled€concentrationÐ 4* I ™   @2‰@‰4Ð2ÌÐ 4*(º   @2 @ 4ÐFuture€Air€Quality€Design€ValueÌÐ  º  Ѐ€€€€€€€€Change€in€actual€emissionsòòÐ É  Ѐ€€€€€€€Between€two€reference€years€€€€óóÐ º  ЀChange€in€monitored€concentrationÐ «û   Ðà  àÌò òó óò òò òó óÌEstimate€a€Future€Air€Quality€Design€Value€ó óÐ ©ù  ÐÌà  àBoth€methods€make€use€of€the€results€of€past€modeling€to€derive€a€modeled€response€ofÏozone€design€values€to€VOC€and€NOx€controls€to€estimate€a€future€air€quality€design€value.€€ÏRelative€reduction€factors€are€derived€and€used€similarly€to€what€is€described€in€U.S.€EPA,€Ï(1999),€òòDraft€Guidance€on€the€Use€of€Models€and€Other€Analyses€In€Attainment€DemonstrationsÐ ^® Ðfor€the€8„Hour€Ozone€NAAQSóó,€EPA„454/R„99„004.€€If€the€estimated€future€design€value€is€<€124Ð OŸ Ðppb,€no€additional€emission€reductions€are€needed€to€strengthen€the€weight€of€evidence€argumentÏfor€attainment.€€€ÌÌ(1)€Calculate€an€average€(over€all€modeled€days)€predicted€daily€maximum€(within€theÏnonattainment€area€and€the€down€wind€plume,€or€domain€wide)€1„hour€ozone€concentration,€firstÏwith€the€base€emissions€(e.g.,€1990)€and€then€with€the€future€emissions€(e.g.,€2007).€ÌÌ(2)€Using€results€from€step€1,€calculate€the€relative€reduction€factor,€RRFòòóó,€€by€taking€the€ratio€ofÐ ×'$ Ðthe€average€daily€maximum€1„hour€ozone€concentration€obtained€with€future€emissions€to€thatÏobtained€with€the€base€emissions.ÌÌà  àRRFòòóó€=€AVGfòòóó€/€AVGcòòóó€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€(1)Ð ›"ë( ÐÌwhere€ÌÌà  àAVGfòòóó€=€average€(across€all€days)€predicted€daily€maximum€1„hour€ozone€concentrationÐ _&¯!, Ðfor€future€emissions,€ppb.ÌÌà  àAVGcòòóó€=€average€(across€all€days)€predicted€daily€maximum€1„hour€ozone€concentrationÐ 2)‚$/ Ðfor€base€emissions,€ppb.ÌÌ(3)€Calculate€the€base€design€value,€DVB,€as€the€average€of€3€nonattainment€area€ozone€designÐ ,U'2 Ðvalues€that€represent€the€period€used€to€predict€ozone€for€base€emissions€(e.g.,€if€1990€emissionsÏare€used,€average€design€values€for€1990,€1991€and€1992)׃5×Ý ƒ #ÃÝòòÚ  Ú1Ú  ÚóóÝ  Ý×  ×.€€€The€nonattainment€area€ozoneÐ ¡ñ Ðdesign€value€is€the€maximum€monitored€design€value€from€all€sites€in€the€nonattainment€area.€ÌÌ(4)€Estimate€the€future€design€value,€DVF,€for€the€nonattainment€area€as€the€product€of€theÏrelative€reductions€factor€(step€2)€and€the€base€design€value€(step€3).€€If€the€future€design€value€isÏ<€124€ppb€additional€emission€reductions€should€not€be€needed,€no€additional€steps€are€required.€ÏIf€the€future€design€value€is€>€124€ppb€proceed€to€apply€method€1€and€method€2€(below)€toÏidentify€additional€emission€reductions.€€ÌÌòòExample€1:€Estimate€Future€Air€Quality€Design€ValueóóÐ j  ÐÌGiven:€Past€results€from€modeling€indicate€predicted€peaks€(for€three€days)€before€controls€inÏ1990€are€195,€180,€and€165€ppb€and€after€controls€in€2007€are€155,€150€and€145€ppb.€€There€areÏtwo€monitor€sites€in€the€nonattainment€area.€€The€monitored€air€quality€design€values€for€eachÏsite€are€185€and€176€in€1990,€145€and€152€in€1991,€and€155€and€140€in€1992.€€ÌÌFind:€Estimate€the€future€air€quality€design€value€in€2007.€ÌÌSolution:ÌÌ(1)€Compute€the€base€and€future€average€1„hour€daily€maximum€concentration.€€The€average€ofÏthe€model€predicted€peaks€(in€and€downwind€of€the€nonattainment€area)€for€the€base€beforeÏcontrols€is:€€(195€+€180€+€165)€/€3€=€180€ppb€and€for€the€future€after€controls€is:€(155€+€150€+Ï145)€/€3€=€150€ppb.€€€ÌÌ(2)€Using€the€results€in€step€1€the€relative€reduction€factor€is:€òòóó150/180€=€0.83.Ð *z ÐÌ(3)€Determine€the€nonattainment€area€design€values€representative€of€the€episode€used€in€the€baseÏemissions€and€calculate€the€base€design€value.€€The€nonattainment€area€design€value€for€1990€isÏMAX(185,€176)€=€185,€for€1991€is€MAX(145,€152)€=€152,€and€for€1992€is€MAX€(155,€140)€=Ï155€ppb.€€The€base€ozone€design€value€is€(185€+€152€+€155)€/€3€=€164€ppb.€€€€ÌÌ(4)€The€estimated€future€design€value€is€òòóó€(0.83)€(164)€=€136€ppbÐ Á#! ÐÌThis€is€>€124€ppb,€so€we€need€to€apply€the€following€methods€to€determine€additional€emissionÏreductions.€€Ìà  àà ` àà ¸ àÌò òÐ  v(Æ#& ÐMethod€1:€Estimate€Additional€Emission€Reductions€Using€Modeled€Responsesó óÐ ° ÐÌò òà  àó óMethod€1€usesò òó óÔ‡XÈåXXXF!Ô€the€change€in€nonattainment€area€monitored€base€ozone€design€value€andÐ ’â Ðestimated€future€ozone€design€value€along€with€Ô#†XF!XXXÈåj.#Ôò òó óchanges€in€modeled€emissions€before€controlsÐ —ç Ð(base€emissions)€and€after€controls€(future€emissions)€to€estimate€additional€emission€reductions.ÌÌ(1)€Calculate€the€change€in€air€quality€design€value€by€subtracting€the€estimated€future€designÏvalue€(e.g.,€2007)€from€the€base€air€quality€design€value€(e.g.,€1990).€€Estimate€the€percentÏreduction€in€NOx€emissions€and€VOC€emissions€which€occurred€within€the€nonattainment€areaÏbefore€and€after€controls.€€Do€not€include€biogenic€emissions.€€Divide€the€percent€reduction€inÏNOx€emissions€by€the€change€in€the€air€quality€design€value€and€divide€the€percent€reduction€inÏVOC€emissions€by€the€change€in€the€air€quality€design€value.€This€step€results€in€two€reductionÏfactors,€one€for€changes€in€NOx€emissions€and€one€for€changes€in€VOC€emissions.€€ÌÌ(2)€Estimate€the€amount€of€additional€ozone€reduction€needed€by€taking€the€difference€betweenÏthe€future€design€value€and€124€ppb,€the€maximum€ozone€design€value€consistent€with€meetingÏthe€NAAQS.ÌÌ(3)€Calculate€additional€necessary€emission€reductions€by€taking€the€product€of€each€of€theÏreduction€factors€(step€1)€and€the€amount€of€ozone€reduction€needed€(step€2).€ÌÌòòExample€2:€Calculate€reduction€factor€using€model€predictions€and€apply€to€model€estimatedÐ í Ðfuture€design€valueóóÐ ŽÞ ÐÌGiven:€Results€from€modeling€used€in€Example€1€indicate€an€estimated€future€design€value€isÏ136€ppb€and€the€monitored€air€quality€ozone€base€design€value€representative€of€theÏnonattainment€area€is€164€ppb.€€The€control€strategy€reflects€a€30%€reduction€in€VOC€and€a€35%Ïreduction€in€NOx€emissions.€€These€reductions€were€obtained€by€comparing€the€modeled€1990Ïbase€emissions€to€the€modeled€2007€attainment€year€emissions€for€the€nonattainment€area.ÌÌFind:€The€amount€of€additional€VOC€and€NOx€reduction€needed€to€reduce€the€model€estimatedÏfuture€design€value€to€124€ppb,€so€that€a€convincing€weight€of€evidence€argument€can€be€madeÏfor€attainment.€ÌÌSolution:ÌÌ(1)€Calculate€the€change€in€air€quality€design€value€as€164€„€136€=€28€ppb.€€The€estimated€percentÏreduction€in€VOC€and€NOx€are€given€30%€VOC€and€35%€NOx.€€The€reduction€factor€for€VOC€isÏ30%€/€28€ppb€=€1%/€ppb€and€for€NOx€is€35%€/€28€ppb€=€1.2%/€ppb.€ÌÌ(2)€The€amount€of€additional€ozone€reduction€needed€is€(136€„€124)€=€12€ppb.ÌÐ q+Á&) Ð(3)€Therefore,€the€additional€reduction€needed€in€VOC€is€(1%)€(12)€=€12%€of€the€VOCÏemissions.€€And,€the€additional€reduction€needed€in€NOx€emissions€is€(1.2%)€(12)€=€14%€of€theÏNOx€emissions.€ÌÌò òMethod€2:€Estimate€Additional€Emission€Reductions€Using€Observed€Air€Quality€ChangesÔ‡XÈåXXXF!ÔÐ tÄ ÐÓWCÜÜ4Œ ä <”ìDœôL¤ü!ü!¬&)\+´- 0d2¼4°œXWÓó óÌÓ“Óà  àThis€method€uses€monitored€ozone€air€quality€design€values€and€emissions€estimates€forÏthe€nonattainment€area€to€calculate€the€reduction€factors€for€VOC€and€NOx.€€These€reductionÏfactors€are€then€applied€to€the€model€estimated€future€design€value€as€calculated€in€Example€1€toÏestimate€additional€emission€reductions.€ÌÔ#†XF!XXXÈåŽ9#ÔÔ‡XÈåXXXF!ÔÌ(1)€Calculate€the€percent€reduction€in€NOx€emissions€and€VOC€emissions€which€occurred€withinÏthe€nonattainment€area€from€an€earlier€year€(e.g.,€1990)€to€a€more€recent€year€(e.g.,€1996).€€€TheÏNational€Emissions€Trends€(NET)€inventory€provides€an€example€of€these€data.€€Do€not€includeÏbiogenic€emissions.€ÌÌ(2)€Calculate€the€change€in€the€nonattainment€areaððs€ozone€design€value€using€the€same€referenceÏyears.€€Ô#†XF!XXXÈå;#ÔTo€account€for€fluctuations€in€meteorology€average€three€years€of€design€values€toÐ Ö& Ðestimate€the€design€value€for€each€of€the€reference€years.€€The€nonattainment€area€average€designÏvalues€are€used€to€assess€the€observed€change€in€air€quality€from€the€ð ðearlyðð€time€period€to€aÏð ðrecentðð€time€period.€€Monitors€that€were€only€online€during€one€of€these€periods€may€not€beÏrepresentative€of€the€actual€change€in€air€quality.€Ô‡XÈåXXXF!Ô€Rationale€for€excluding€a€monitor€should€beÐ «û Ðdocumented.ÌÌ(3)€Divide€the€percent€reduction€in€NOx€emissions€by€the€change€in€the€areaððs€ozone€designÏvalue.€Divide€the€percent€reduction€in€VOC€emissions€by€the€change€in€the€areaððs€ozone€designÏvalue.€This€step€gives€two€Ô#†XF!XXXÈåD?#ÔÔ‡XÈåXXXF!Ôreduction€factorsÔ#†XF!XXXÈå®@#ÔÔ‡XÈåXXXF!Ô,€one€for€changes€in€NOx€emissions€and€one€forÐ €Ð Ðchanges€in€VOC€emissions.€€ÌÌ(4)€Calculate€the€additional€amount€of€ozone€reduction€needed€by€subtracting€124€ppb€from€theÏmodel€estimated€future€design€value€(see€Example€1).€ÌÌ(5)€Ô#†XF!XXXÈåA#ÔCalculate€additional€necessary€emission€reductions€by€taking€the€product€of€each€of€theÐ 8#ˆ  Ðreduction€factors€(step€1)€and€the€amount€of€ozone€reduction€needed€(step€2).€Ô‡XÈåXXXF!ԀР=$! ÐÌÔ#†XF!XXXÈåöB#ÔòòExample€3:€€Calculate€reduction€factor€using€change€in€ozone€air€quality€design€values€andÐ 6&†!# Ðnonattainment€area€emissions,€and€apply€to€model€estimated€future€design€valueóóÔ‡XÈåXXXF!ÔÐ &'v"$ ÐÌÔ#†XF!XXXÈåD#ÔGiven:€There€are€two€monitors€in€the€nonattainment€area.€€The€monitored€air€quality€designÐ  )Z$& Ðvalues€for€each€site€for€reference€years€1990€and€1996€are€presented€in€Table€2.€€EmissionÏreductions€between€1990€and€1996€are€30%€reduction€in€VOC€and€a€35%€reduction€in€NOxÏemissions.€€These€reductions€were€obtained€by€comparing€the€1990€NET€inventory€to€the€1996Ð Ú+*') ÐNET€inventory€for€the€nonattainment€area.€€The€model€estimated€future€design€value€in€2007€isÏ136€ppb.€€ÌÌÔ*‹ƒ &dd„dd"„/ dd / Å dd Å &°(#°(#‹ÔÔ,dd ÔÔ,¶dd ÔÔ,dd ÔÔ,edd ÔÔ,dd ÔÔ,dd ÔÔ,èdd ÔÔ+  ÔÐ %€y €Ð ……%Ðà l àò òTable€2.€Air€Quality€Design€Values€(ppb)ó óÐ +!ä4y ……+ÐÓ  ÓÌMonitorÐ 3)#T ¤ 88 ……3ÐÓ  Ó1990€Reference€YearÐ %d ´  ……%ÐÓ  Ó1996€Reference€YearÐ .$d ´  „„…….ÐÐ C9 € Ð Ÿ@1990„„‰Ÿ@‰CÐ1990€Ð ka4ä 4 " Ÿ@1990 Ÿ@ Ÿ@1991„„‰Ÿ@‰kÐ1991Ð ka4ä 4 " Ÿ@1991 Ÿ@  Ÿ@1992„„‰ Ÿ@‰kÐ1992Ð ka4ä 4 "  Ÿ@1992  Ÿ@ 0Ÿ@1996„„‰0Ÿ@‰kÐ1996Ð ka4ä 4 " 0Ÿ@1996 0Ÿ@ 4Ÿ@1997„„‰4Ÿ@‰kÐ1997Ð ka4ä 4 " 4Ÿ@1997 4Ÿ@ 8Ÿ@1998„„‰8Ÿ@‰kÐ1998Ð h^4ä 4" 8Ÿ@1998 8Ÿ@  ð?1„„‰ð?‰hÐ1Ð g]1d ´"  ð?1 ð?  g@185„„‰ g@‰gÐ185Ð i_3d ´"  g@185  g@  b@145„„‰ b@‰iÐ145Ð i_3d ´"  b@145  b@ `c@155„„‰`c@‰iÐ155Ð i_3d ´" `c@155 `c@ €a@140„„‰€a@‰iÐ140Ð i_3d ´" €a@140 €a@ @b@146„„‰@b@‰iÐ146Ð i_3d ´" @b@146 @b@ `a@139„„‰`a@‰iÐ139Ð g]3d ´" `a@139 `a@  @2„„‰@‰gÐ2Ð g]1ä 4 "  @2 @ f@176„„‰f@‰gÐ176Ð i_3ä 4 " f@176 f@ c@152„„‰c@‰iÐ152Ð i_3ä 4 " c@152 c@ €a@140„„‰€a@‰iÐ140Ð i_3ä 4 " €a@140 €a@ à`@135„„‰à`@‰iÐ135Ð i_3ä 4 " à`@135 à`@  b@145„„‰ b@‰iÐ145Ð i_3ä 4 "  b@145  b@ @`@130„„‰@`@‰iÐ130ÐC97ä 4 " @`@130  @`@ CÐÌFind:€The€amount€of€additional€VOC€and€NOx€reduction€needed€to€reduce€the€future€designÏvalue€to€124€ppb,€so€that€a€convincing€weight€of€evidence€argument€can€be€made€for€attainment.€Ô‡XÈåXXXF!ÔÐ à0  ÐÌSolution:ÌÌ(1)€The€estimated€percent€reduction€in€VOC€and€NOx€are€given€30%€VOC€and€35%€NOx.ÌÌ(2)€Calculate€the€change€in€the€nonattainment€areaððs€ozone€design€value.€€Determine€the€designÏvalue€for€each€reference€year€by€first€taking€the€maximum€design€from€the€two€sites€for€each€ofÏthree€years€and€then€averaging€the€three€years€design€values.€€€The€nonattainment€areaððs€ozoneÏdesign€value€for€1990€is€(185€+€152€+€155)€/€3€=€164€and€for€1996€is€(140€+€146€+€139)€/€3€=€142Ïppb.€€TÔ#†XF!XXXÈåaR#Ôhe€change€in€air€quality€design€value€as€164€„€142€=€22€ppb.Ô‡XÈåXXXF!ÔÐ d´( ÐÌÔ#†XF!XXXÈåßT#Ô(3)€The€reduction€factor€for€VOC€is€30%€/€22€ppb€=€1.36%/€ppb€and€for€NOx€is€35%€/€22€ppb€=Ð ]­* Ð1.59%/€ppb.€ÌÌ(4)€The€amount€of€additional€ozone€reduction€needed€is€(136€„€124)€=€12€ppb.ÌÌ(5)€Therefore,€the€additional€reduction€needed€in€VOC€is€(1.36%)€(12)€=€16%€of€the€VOCÏemissions.€€And,€the€additional€reduction€needed€in€NOx€emissions€is€(1.59%)€(12)€=€19%€of€theÏNOx€emissions.€ÌÌò òIncorporate€Tier€2€and€other€unmodeled€control€measuresó óÐ Í$ 3 ÐÌà  àOnce€the€percent€reductions€for€VOC€and€NOx€have€been€determined€they€can€beÏconverted€into€tons€per€day€reductions.€€Control€measures€used€to€address€these€additionalÏreductions€must€be€quantified€as€estimates€in€tons€per€day€reductions€and€compared€to€the€levelÏof€additional€reductions€needed.€€Sufficient€additional€measures€have€been€identified€when€theÏtotal€from€all€unmodeled€controls€are€equal€to€or€greater€than€the€estimated€additional€reductions.ÌÐ ]+­&: Ð(1)€Convert€the€estimated€percent€reduction€in€VOC€and€NOx€to€tons€per€day€by€taking€theÏproduct€of€the€percent€reduction€and€the€total€emissions€in€the€base€case€inventory€for€eachÏcategory€of€emissions,€VOC€and€NOx.€€This€results€in€tons€per€day€for€VOC€and€tons€per€day€forÏNOx.€€These€are€the€additional€level€of€controls€needed.ÌÌ(2)€Subtract€the€Tier€2€emission€reduction€estimates€being€applied€towards€attainment€from€theÏadditional€level€of€controls€for€each€category€of€emissions,€VOC€and€NOx.€€All€other€unmodeledÏcontrols€should€be€subtracted€as€well.€€Repeat€this€step€until€no€additional€reductions€remain.ÌÌòòExample€4:€Adjust€additional€emission€reductions€to€account€for€Tier€2óóÐ  p  ÐÌGiven:€The€nonattainment€area€total€emissions€in€1990€for€VOC€and€NOx€are€1197€tpd€and€927Ïtpd,€respectively.€€Also,€as€shown€in€Table€3€the€estimated€Tier€2€reductions€in€VOC€and€NOxÏare€10€tpd€and€25€tpd,€respectively.€€The€estimated€additional€emission€reductions€are€16%€VOCÏand€19%€NOx,€as€calculated€in€example€3.ÌÌÔ*׃&8dddd ¶dd ¶dd edd edd dd èdd è &°(#°(#×ÔÔ,bdd ÔÔ,dd ÔÔ,9dd ÔÔ,Ýdd ÔÔ,bdd ÔÔ,dd ÔÔ,îdd ÔÔ,6dd ÔÔ,hdd ÔÔ+  ÔÐ %€y ° … …%ÐÓ  Óò òTable€3:€Nonattainment€Area€Emissions€Summary€(tpd)€without€Tier€2ó óÐ =3$d y  „„……=ÐÓ  ÓYearÐ 3)#”ä ÀÀ  ……3ÐÓ  ÓVOCÐ %”ä  ……%ÐÓ  ÓNOxÐ %”ä  ……%ÐÐ  ° ÐPointÐ  d ÐAreaÐ  d ÐMobileÐ  d ÐTotalÐ  d ÐPointÐ  d ÐAreaÐ  d ÐMobileÐ  d ÐTotalÐ 7- d Ÿ@1990‰Ÿ@‰7Ð1990Ð XN+”ä Ÿ@1990 Ÿ@ y@400‰y@‰XÐ400Ð WM*”ä y@400 y@ ð{@447‰ð{@‰WÐ447Ð WM*”ä ð{@447 ð{@ àu@350‰àu@‰WÐ350Ð XN*”ä  àu@350 àu@ ´’@1197‰´’@‰XÐ1197Ð XN+”ä! ´’@1197 ´’@ Àr@300‰Àr@‰XÐ300Ð WM*”ä" Àr@300 Àr@ w@377‰w@‰WÐ377Ð WM*”ä# w@377 w@ @o@250‰@o@‰WÐ250Ð WM*”ä$ @o@250 @o@ øŒ@927‰øŒ@‰WÐ927Ð XN*”ä% øŒ@927 øŒ@ \Ÿ@2007‰\Ÿ@‰XÐ2007Ð XN+d& \Ÿ@2007 \Ÿ@  n@241‰ n@‰XÐ241Ð WM*d'  n@241  n@  q@282‰ q@‰WÐ282Ð WM*d(  q@282  q@ i@200‰i@‰WÐ200Ð WM*d) i@200 i@ ˜†@723‰˜†@‰WÐ723Ð WM*d* ˜†@723 ˜†@ Àb@150‰Àb@‰WÐ150Ð WM*d+ Àb@150 Àb@ €s@312‰€s@‰WÐ312Ð WM*d, €s@312 €s@ @_@125‰@_@‰WÐ125Ð WM*d- @_@125 @_@ X‚@587‰X‚@‰WÐ587Ð :0*d. X‚@587 X‚@ ……:Ѐ€€€€€€€€€€€€€€Estimated€Tier€2€Reduction€=Ð 8. ”ä/  $@10‰$@‰8Ð10Ð 9/)”ä0  $@10 $@ ……9ÐÐ 8. ”ä1  9@25‰9@‰8Ð25Ð9/-”ä2  9@25  9@ 9ÐÌFind:€What€are€the€additional€emission€reductions€in€tons€per€day€still€needed€after€incorporatingÏTier€2?ÌÌSolution:ÌÌ(1)€The€additional€reductions€are€(.16€*€1197€tpd)€€=€192€tpd€for€VOC€and€(.19€*€927)€=€176€tpdÏfor€NOx.ÌÌ(2)€After€subtracting€Tier€2€reductions€the€remaining€reductions€are€(192€„€10)€=€182€tpd€for€VOCÏand€(176€„€25)€=€151€tpd€for€NOx.Ìò òÌÐ  ð'@#> ÐUse€of€Results€ó óà ¸ àà  àà h àÐ ° ÐÌà  àThe€results€from€both€methods€should€be€considered€along€with€other€weight€of€evidenceÏpresented€in€the€technical€analyses€for€the€attainment€demonstration.€€For€example,€where€modelÏpredicted€peaks€show€greater€improvement€when€low€level€NOx€emissions€are€reduced€versesÏVOC€or€elevated€NOx,€substituting€an€equal€amount€of€low€level€NOx€reductions€for€the€VOCÏreductions€is€acceptable.€€Also,€where€modeling€demonstrates€substantial€improvements€in€modelÏpredicted€peaks€when€emission€reductions€are€applied€to€adjacent€counties,€the€area€of€controlsÏmay€be€extended€to€include€adjacent€counties.€€However,€if€emissions€from€adjacent€counties€areÏused€they€must€be€included€in€the€total€emissions€for€the€base€and€future.€€Modeling€theÏadditional€emission€reductions€would€normally€address€these€two€example€as€well€as€theÏfollowing:€change€in€boundary€conditions€due€to€transport,€location€of€emissions€(such€as€point,Ïarea€or€mobile),€elevated€vs€low€level€emission€reductions,€chemistry€and€wind€flow€patterns.€ÏModel€sensitivity€runs€may€be€used€to€help€identify€the€appropriate€controls€measures€to€fill€theÏadditional€emission€reductions€needed€to€provide€for€attainment€in€the€weight€of€evidenceÏanalyses.ÌÌà  àFor€guidance€on€VOC€and€NOx€substitution€use€the,€ð ðNOx€Substitution€Guidanceðð,€EPAÏ1993;€ð ðTransmittal€of€NOx€Substitution€Guidanceðð,€memorandum€from€John€Seitz,€1993;Ïð ðClarification€of€Policy€for€Nitrogen€Oxides€(NOx)€Substitutionðð,€memorandum€from€John€Seitz,Ï1994;€and€ð ðGuidance€for€Implementing€the€1„Hour€Ozone€and€Pre„Existing€PM10€NAAQSðð,Ïmemorandum€from€Richard€D.€Wilson,€1997.€€The€1993€and€1994€guidance€was€primarilyÏdesigned€for€the€post-1996€rate€of€progress€(3%/year€VOC€reduction)€requirement€and€allowedÏNOx€reductions€to€be€substituted€for€the€otherwise€mandatory€VOC€reductions€as€long€as€theÏNOx€reductions€were€shown€to€be€consistent€with€the€attainment€demonstration€(in€other€words,Ïif€the€attainment€demo€relied€only€on€VOC€reductions,€the€area€could€not€substitute€NOxÏreductions€for€the€3%/year€requirement,€and€if€the€attainment€demo€relied€on€both€VOC€&€NOxÏreductions,€NOx€could€be€substituted€in€part€).€€The€1994€guidance€document€(Guidance€on€theÏPost-1996€Rate-of-Progress€Plan€and€the€Attainment€Demonstration,€EPA-452/R-93-015,€Jan.Ï1994)€provided€equations€&€procedures€for€calculating€the€amount€of€NOx€reductions€that€couldÏbe€substituted€for€VOC€for€the€rate€of€progress€requirements.€€Also,€the€1997€guidanceÏestablishes€the€100€&€200€km€distances€for€substitution€of€emission€reductions€outside€theÏnonattainment€area.€€These€documents€are€located€on€the€EPA€website:Ïð ðwww.epa.gov/ttn/oarpg/t1pgm.htmlðð.ÌÌ