*- ". - "" -=. __ I --- . -- --. . -- -- 3 - - 'P 

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UNITED STATES ENVIRONMENTAL PROfECTlON AGENCY 

Office of Air Quality Planning and StanUards 

Research Triangle Park. North Carolcna 2771 1 

4 SEP 1992 * 

SUBJECT: Procedures for Processing ignate meas 

to Attainment 

FROM : . John Calcagni, Direc 

Air Quality nantsgeme 

'TO: Director, Air, Pesti s and Toxics 

Division, Regions 

Director, Air and Waste Management Division, 

Region I1 

Dirbctor; Air, Radfazi~n and Toxics Division, 

Region 1x1 

Director, Air and Radiation Division, 

Region V . Director, Air, Pesticides and Toxics Division, 

Region VI 

Director, Air and Toxics Division, 

* Regions VXI, VIII, IX, and X 

mse 

The dffice of Air ~uality Planning and Standards (OAQPs) 

eipects mat a n&r of redesignation requests will be submitted 

in the near future. Thus, Regions will need to have quidance on 

the applicable procedures for handling these requests, including 

maintenance plan prwisfons. This m;amora.ndup~, therefore, 

consolidates the ~nviromentkl Protection Agency's (EPAfs) 

guidance regarding the processing sf requests for redesignation 

of nonattair~a~t areas to attainment far ozone (Oj), carbon 

monoxide (CO), particulate matter (QM-IQ), sulfur dioxide (SO2), 

nitrogen dioxide [NO ), and lead (Pb).. Regions should use thzs 

guidance as a genera? framework for drafting Federal mtex 

notices pertaining to red~tsi~natian requests. Special concerns 

for areas seeking redesignation from unclassifiable t~ attainment 

will be addressed on a case-by-case basis, 

Section 187(dj(31(~) sf the clean Air Act, as amended, 

ignated to attainment %@PIW 
1. The EPA has determined that the national anbient air 

quality standards (NMQS) have been attained. 

2. The applicable implementation plan nas hen fully 

approved by EPA under section llO(k), -..ILLI 

__LI 

3, The EPA has determined that the improvement in air 

quality is due to permanent and enforceable reductions in 

emissions. 

8, The State fias met dl'i app22~~Je er~i~~vts fnr llbe 

area under saction 110 and Part DI 

5, 'The EPA has fully approved a maintenance. plan, including 

a contingency plan, far the area under section 175A. 

-A. - +he- czitsda is discus~ed in more detail in the 

following paragraphs, -Particular attention is.given to 

maintenance plan provisio~s at.-khe.end of this docunant since 

maintenance glans constitute a new requirement under the amended 

Clean Air Act. .Exceptions to the guidance will be considered on 

a case-by-case basis. 

The State must show that the area is attaining the 

applicable NMQSo There are tw components involved in making this demonstration which should be considered interdependently. - 

The fixst component relies upon The 

e 

product of ambient monitoring Mat is representative of the area 

og highest concentration. These monitors ~h~~ld remain at the 

saae location for the duration of the monitoring period required 

for demonstrating attainment. The data should be collected md 

quality-assured in accordance with 40 CFR 58 and recorded in the 

Aercmetxic ~nformation Retrieval System (AIRS) in order for it to 

be available to the public for review. For purposes of 

redesi-qnation, the Regional Offiar sbuld verify that the . 

integrity of the air quality monitoring net:mrR &as 2wm 

preserved. 

Sa3tP 3ymms df 

7 W3.T "mw, Wxpp*~ to 40 eER 

Wd~&*# ke &-"may*@' a *a ;a*** For d3, the must 

that the average anrmal number of expected exce&anees, according 

t;o 40 CFR 50.9, is less than or equal t~ Z.0 baaed an data from 

all monitoring sites in the area or its affected downwind 

environs. xrr making this showing, btb PH-10 and O3 aust rely an 

3 complete. consecutive calendar years of quality-assured air 

quality lnanitoring data, callacted in accordance with BO CPR 50, 

~ppcndices K and K. For CO, an area oay be considered attaining 

&he NMOS if there are no violations, as aatsnnined in acrcotdance 
with 40 CFR 50.8, based on 2 complete, consecutive calendar years 

of quality-assured monitoring data. Ear SQ2, ~ccuH%TW~ tcr 80 CFR 

m.4, ah &tea mm&i dww nB MY& Wan ons aseeedanca anntkaliy and 

for Pb, accorrling to section 50.12, an area may show no .- 

exceedances on a quarterly badpis- 

~ent relies upa 

No such 5uppl 

areas seeking retiesignation. Modeling Pay ine the representativsness af the amnitored 

data. For pol1u- such as SO2 and CO, a soall number of 

monitors typically is not representative of areawide air quality 

or areas .of highest cancentratian. When dealing with SoZ, Pb, 

PW-10 (except fur a liaited number of initial Poderate 

nonattairunent dds), and CO (except moderate areas with -sign 

values of 12.7 par% per lillion or.lo#er et the time of passgge of the Clean Air Act AaenUments of 1990), ;rX$~~znim Weiinq . wB-U genqwPly be m&smasjp tm~wid~3ua$e ~r~Qvcrly s4prcesc impebs and W de4sc~spfna the -'as oS iWfmcfiI& h&gB 

&&me&*- baa apcm aurruht ;?i()ndi%isnt. Ueas which were . designated nonattaiment bcrsea on modeling will generally not be 

redesignated to attainaent.unless an acceptable modeling analysis 

indicates attainment. .~egions should consult with OAQPS for 

further guidance addressing the need for madeling in specific 

circunstances. 

Thf SIP for +h. area must be fully apprwd under section 

110(k), and must satisfy all requirements that apply to the 

area. It should be noted that approval action on SXP elements 

and the redesignation request aay occur ~imultaneau~ly. An area 

cannot be redesignatd if a required element of its plan is the 

subject of a disappraval; a finding of failure to submit or to 

fnpiemt the SZP~ or partial, - condit" , or limited apnroval. However. thisdoes not mean uut earlwssues with raJard to ' 

the SIP will be reopaned, Regions shmld not reconsider those 

tnings, that have already been approved and far which the Clean 

Air ~ct &enaterats did not altar what is required. In contrast, 

to the axtent the Aaendments add a requirement or alter an 

existing requirement so that it adds sonething more, Regions 

should cansider those issues. In addition, requests from areas 

hewn to b 8ffecteri by dispersion techniques which are 

incorksistent with EPA guidance will continue to be eonsidered 

unappmvable undtt aection 110 and will not qualify far 

redesignation. 

%section 110tk) contains the requitemenes for IWA aotibln on 

plan subraissions- It aadresses completeness, deaQlines, full and 

partial approval. conditional approval, and disapproval, 
. - 3. Perinanent and Enforceable Im~eovement in Air ~uality 

The State must be able to reasonably attribute the - 

improvement in air quality to emission reductions which are 

permanent and enforoeablee2 ~ttainment resulting from temporary 

reductio'ns in eh~ission rates (-e. g, , reduced production or ' 

shutdown due to temporary adverse economic conditions) or ' 

unusually favorable meteorolqgy would* not Qu&lify as an air 

quality improvement due to permanent and enforceable emission - 

reductions. 

In making this showing, the State should estimate,th& 

percent reduction ($rom the year that was.'used to determiqe.the 

design value far designation and classi-fication) achieved from , 

' Federal measures such as the -Federal.Motor ~ehiele."~bntrol 

-Program and fuel volatilfiy rules as well--as 'pohf rol measareq ' . ' f 

that have been adopt& and implemented by the State. his ' . estipate should consider emission rates, production capacities, 

and. other related information to. clearly .shac\! that the air 

-quality improvements are the result of implemented- controls- The ' 

analysis should assume that sources nre- operating at permitted. . . 

levels . (or histof ic .peak 'levels) unless evidence 1s presented.- . . ' . . .. .. . that such an assumption is '.unrealistic. 

i - - *. - -. - 4 , - Seetion 118 and Part D Requirements : , . 

. .. or. the purposes of redesignktiofi, a. State mustmeet ail '' ' 

requirements of section 110 'and Park. D. that were applikable pr2or , 

. . . .. . to. submi.tta1 of the complete redesi.gnation 'reqoest . . . Whbn .- ' -. - . evaluating a redesignation request, Regions should. not, cons%der 

'whether the State-has met requirements that &me due under the a.- 

-. Act af tair . submittal of ' a complete fed6signation request, ' '. '' 

- 

2~h.is is consjLstent with.. EPA" existing policy on 

redesigr~ations as stated i.n an April 21! 1983. memorandum titled . *'sect iorr .I07 Designation policy Stpunary; " This memuthndum. sgates .' 

that in order for an area to be redesignated. to ' attainmeng, the 

State must show 'that "actual enlEorceable emission reductions are 

respons ible for the recent air quality irnprovem.ent . This 

element of the policy retains its validity under the amended Act - pursuant: to section 193 INote: cothey aspects of the .April 21, 

1983 menorandum .have since been superseded by subsequent 

memoranc3lums; inkerested parties should co'nsult with OAQPS before 

relying on the'se aspects, e.g. those- relating ko required years 

of air cguality data,] 

3~nder section 175A(c) , however, the requirements of Part b 

remain :Ln force and effect for the area until such time as.it is. 

redesigraated. Upon redesignation to attainment, the requirements 

that became due under section 195A(c) after submittal of the 

complete redesignation request would no longer be applicable. 
Noweves, any requirements that came due prior to submittal of the 

redesignation request must be fully approved into the plan at or 

before the time EPA redesignates the area. m 

To avoid canfusian concerning what requirements will be 

applicable for purpcrses of rdlesi~nation, Re#ons should 

encourage States ta work closely with the appropriate Regional 

Office early in Me process. This will help to ensure that a 

redesignation request submitted by the State has a nigh likelihood of befng agprwed by EPA. Regions should advise 

States of the practical planning consequences if EPA disapproves 

the redesignstion request or if the request is invalidated 

because of violations recorded during EPA's review. Under such 

circurstdnces, EPA does not have the discretion +a adjust 

schedules for iqpleaenting SZP requirentnts. As aresult; an 

area aay risk s~ctione and/or Fsd?ral ihpXemenC&tion fr.'arr 

implementation that could result from failure to meet SIP 

submittal or implementation requirements. 

Section 110(a)(2) contains general requirements for 

nonattainment plans. Hust of the-provisions of this section ase 

the same as those containad in the pre-mended Act. We will 

provide guidance on these rquf rements as flaeded. 

Part D consists of general requirements applicable to all 

areas which are designated nonattainnent based on a violation of 

the MS. The general requirements are followed by a series of 

subparts specific to each pollutant. The general requirements 

appear in subpart 1. The requirements relating to 03, CO, PM-10, 

SOZ, NOZ, and Pb appear in subparts 2 through 5. In those 

instances where an area is subject to both the general nonattainment provisions in subpart 1 as well ass one of the 

pollutant-specific subparts,' the general provisions may be 

su&sumed within, or superseded by, the more specific requirements 

of subparts 2 through 5, 

If am area was not claecified under section 181 for 03, or 

section 186 for Co, men that area is only subject to the 

provisions of subpart 1, RNonattainment Areas in General," In 

addition to relevant provisions in subpart 1, an o3 and co area, 

which is classified, must meet all applicable requarements in 

subpart 2, RAdditional Provisions fer Ozone Nonattainment.Ueasem 

and subpart 3, nAdditional Provisions for Carbon Honoxide 

4General guidance regarding the requirements for SIP'S may 

be found in the @General Preamble. to Title I of the 1990 Clean 

Air Act mendment~,~ 57 FR 13498 (April 16, 15392). 
Nonattainment AreasDa@ respectively, before the area may be 

redesignated to attafnment. All PM-10 nonattafnnent areas 

(wilether classified as moderate or serious) must similarly meet 

the applicable general provisions of subpart 1 and the specific - 

Pn-10 provisions in subpart.4, *M&itimal Prwisims for 

Particulate Hatter Nonattainment Areas.' Likewise, SO2, NO , Pb nonattai~~nt areas are subject to +he applicable generat 

nonattaiment provisions in subpert 1 as well as the more 

specific requirmnents in sub* SD uAdditional Provisions for 

keas Designated Wonattainment for Sulfur Oxides, Witrogen 

Dioxide, and Leadam 

This section wntains general requ5rurents for nanattainment 

plans. A thorough discussion of these requirements my be found 

in the Prmle utle 3 (57 FR 13498 (April 16, 

1992)J. The EP& anticipates.that areas will already have met, 

most or all of these rquimments to .the extent that. they ara not 

superseded by more specific Part D.require~mks. me 

requirewnts Lor reasonable further progress, identification of 

certain emissions increases, and other mea6wes needed for 

attainment will not apply for redesignatfans kcawe they only 

have aeaning for araas mt attaining the standard. The 

requirements for an emission inventory will be satisfied by the 

inventory requirenents of the maintenance plan. ~Sm~~

&%%* W'"W * *-**aw&&?q@ m-- -&&&',&&*y*&g&~& & "a* 

The State must work with EPA %a show that its SIP 

provisians are wnsistent with section 176[c)(4) Canfo 

requirementsm The redssignation.request should include 

confonaity procedures, if the State already has these procedures in place. Additionally, we currently f-ntarpret the conformity 

requirement to apply tcl axtaimment areas. %awes-, EPb has wt 

yet issued its conformity regulations specifying what areas are 

subject to the conformity requirement. Therefore, fF a State 

daea not have canforntity procedures In place at the time that it 

submits a redesignation request, me State must c=ollrrit to folzow 

EPA's conformity regulation upon issuance, as applicahxe, ~f the 

State submits the redarsignatian request SUbSefpent tc EPArs 

issuance of the conformity regulations, and the conformity requirement became applicable to the area prior tea submission, 
the State laus% adopt the applicable conformity requirements 

before EPA can redesignate the area. 

Section 107(d)(3)(E) of the amended Act stipulates that for 

an area to be redesignatcd, EPA must fully approve a maintenance 

plan Which meets the requirements of section 175A. A State my 

submit both the redesignatian request and +he maintenance plan at 

the same time and rulemaking on both may praceed on a parallel 

track- Maintenance plans nay, of course, be submitted and 

approvsd by BPA -fore a redesignation is requested. However, according to section 175A'(c), pending ap roval of the maintenance 

requirements shall remain in prace. . plan apd'redesignation request, all appl P cable nanattainment area 

Section 175A defines the general framework of a maintenance 

plan. The naintenance plan will constitute a SIP revfsion and 

must provide for maintenance of the relevant NMQS in the area 

for at least 10 years.after redesignation. -yactfm 175h fukther 

states that the plan mall contain such additional nmasures, if 

any, as may be neccesary to ensure such msintenance. Because the 

Act requires a demonstration of maintenance for 10 years after an 

area is redesignated (not 10 years after mbmitt:aL of a 

redesignation request), the State should plan for some lead time 

for SPA action on the request. In other words, the maintenance 

demonstration should project maintenance for 10 years, beginning 

from a date which factors in the time.nacessary for EPA review . 

and approval action on the redesignation request- In determining 

the amount of lead time to allow, States should consider that 

sectfon 107(8)(3)(D) grants the Administrater up to 18 months 

frcrm rmceipt of a complete submittal to process a redesignation rwjuest. The statute also requires the State to submit a 

revision of the SIP 8 years after the original redesignatian 

request is approved to g'r2wcidids for maintenance of .the NMQS far. 

an additional 10 years following the first 10-year periad [see section 175A(b)'j. 

In addition, the maintenance plan shall contain such 

the Admfnistrator deems necessary to 

ensure prom* correction of any violation of the NAAQS [see 

will i&l&t aA1 maastx~es c~ata-in~ Xn the m&mainment SIP 

q&xbs %a x~iir~tbqa. Pallure CO mafnkaiir NAAQS and 

The follbwing is a list of core provisions that we 

anticipate will be necessary to ensure maintenance of the 

relevant NAAQS in an area seeking redesignatian from 
nonrttairrrent to attainment. We therefore recommend that States 

seeking redesignation of a nanattaiment area considasr these 

provisions. troy~ver, any final SPA detrr8ination reqarding the 

adequacy of a Wntenance plan will be matla following review af 

the plan sub3ittaZ in light of the psrticular circumstunces 

facing the area proposed for redesignation and based on all 

relevant inforration available at the time. 

The State should dwalap an attaimt emissions inventory 

ta identify the leva1 of desi in the rc+a whicb. is 

sutiicieqt to attain WMgs.~~i~ imnwory sbculd 

censistent with =A's mot rscent guidencc on c8.issi.on 

inventories for mnattainment areas available at the! ti= and 

should tnclude the dssions during the tfl~~period .ssociacr(L . 

with the mn&torifig data showing rt+ainrcu\t. 

I ue 100 +ons/yeu for SO NO , and 

m-3 im ~t, b.8~ upon ro cFa'sl.f~o(u) 

- and 51.322, a8 wall a6 estublished practice for Aa3 data. The 

source size threshold for serious P!U-10 areas La 70 tons/yeah 

&re the State has made an adequate d#onstration that air 

quality bag iapcovod as; a ramult of the SIP (as di8~~86d 

previously),-the attainrent inventory will cp~nwally be +he 

actual inventory at the tine the -+a attain88 the stamhrd. 

BPA8s curie* guibrmcce ion tQm preparation eC emission 

inventories far 0 and CO nanattainnent areas is cclntained in the 

.following dwzimenb: *Procrdtm. for th. Rmparation of mission 

Invsntorisr for Carbon Monoxide and PmmuBOrs of Ozone: Value 

fm (EPA-450/4-91n016), aPrecedures fur thr Preparation of 

Emission Inventories for Carbon Monoxide and Prm~~.gom of Ozone: 

volune IT* (Ep~-450/+-91.-014), @smissfan fnventory ~wimenfor Ozone State Iirplsrantati~n Plansm (EPA-450/4-9!t-orQ), mBmieeion Inventory Xequirenents for Carbon Monaxirie 

Implamentation Plansa (BPA-450/4-91-Oil), *Guibslh~e far . 

Regulatmry A~licmtia of the Urban Aimhad -1" (gPA-45afa-0dl013), aPracaduros *or mission Inventory 919parath)n: woi 3F1%, 

c.U..bilm- SDL" . t EPA-450/4-81426d) and "P~~WIBS for 

Preparing E.iu.8ion - Inventory Pro$&zW.rSlu- "~~FPw~~~~~sP* ~ef p~ - 

Tha SF& does not cnrrrently hevc specific guidance #on attai~etlt 

missions inventories for so m liru #+reof, sktes me 

referred to a-guidan~t on &ssionm data to be us& as in* to 

.nd~ling d-SmtimS, wnrfrrt- 4b 9.1 af =A'S 

nGuibeline on Air Quality Wwls [Rettised)* I1BPA-450/2-7@-02m], 

July &987, which is gensrally applicable te all cziteria 

plollutants. Ermierion inventory proeredures and requirements doamente ara currently beiq prepared by OZIQPS fctr PLa-1.0 and pb: 

these ~OCUIUI~Q are due dm telearrrr by suuet 1092:- 
according to Clean Air Act section 189(B)(3). Hmever, the 

inventory should include sources belaw these size thresholds if 

thace smallmr sources were included in the SIP attainment 

demnsttrtion. Where eroeurces belaw the tO0, ?O, and S tons/year- sire thresholds (e.g,, anws with sraaller source site 

definitions) are sdbjQet to a StM.e8r mr source permit 

progr-, there rourocha need only kr 8ddreSssd in the aggregate to 

the extent that tnay reeult in areawide grouth.' 

For O3 nnrttaitment weas. the inventory sh6uld be based on 

actual rntyplcal rummaw day* emiesiuam of 0, grecurooxs (volatile 

organic compeunde and n&tsoQan oxides) durxng thc attainnent - year. Tbis will generrlly oorrt~opond to one of the priodic imr~teries raquLred fur nanattalnunt amas to r+c~ncile 

milestones. For co nanattafluent areas, the inventaiy 8hou.ld be 

basd on ac+ual mtypic.1 CO seam dayw emissions fer the 

attainment year. Thie will generally correspond to one of thcJ 

perf odic invmtorirs required for nonattainrent. areas - - 

b* s * 

A State.~y generelly demonstrata maintenance of the HAWS 

by eithar snminp that future dssiens of a pollutant or its 

precursors will wt exceed the level of the attainment inventory, 

Or by mocbling to show that the future mix of sources and 

erisoion rates will not cause a violation of the HAMS. Under 

the Clean Air Act, ~ny arers are required to stahit nodeled 

attairment dearomstrations to show that proposed reductions in 

enimsions will be sufficient to attain the applicable #Ms. or 

these areas, thr raintenmea daronstration shauld be based upon 

the came Level of modeling. In areas where no euch modeling was 

requited, the State should be ibls .to rely on the r.ttaiment 

inventory appmacb. In both instances, the denanstcation should 

k for a priad af 10 years fallawing the rrdesignatian. 

Where abdeling is relied upon to domonatrate maintenance, 

eacb plan should contain a shmary of the air quality 

concentratians expected to rmsult from application of the control 

strategy. In t4e prbc~ss, tbe plan should ibantify and describe 

the dispersim - a?- akWw &ir guality model used fo project 

ambient oaMIhntratfans (6- 40 CFR St.46). 

Xn eiuter case, to satisfy the deaonetration roguitrnent the 

State ehcnrld project emissiarus for the 10-year period fallowing 

redesignation, erther for tbe purpose air showing that edrtians 

will nut )rise oru the attaiwnt inventory or for conducting 

aodeling. The projected inventory should cansfdar future 

qrovth, including population atrd industry, slmuld be consistent 

'Gufdance for projactinp emissions may &e formd in the 

aissions fmrenkory quidawe cfted in footnote 6. . 

,. 
with the attainment inventory, and should dM?unent data inputs 

and assumptions, All elements of the de~po~~stration (e.g., 

emission pm$ections. new source growth, and .$cling) should b. 

ceneiotent wrth earrant EPA nodeling guidance. 8'or.o and CO, - 

+Ile -projec+rd ~uiom should reflect thc -czt~ .dual 

~E~SS~O~S met3 on emfarceable ~iarsiorr rates and typical 

production rates. 

For cO, 8 State shard address the sra~wide component of the 

raintenmce demmmtration either by elmwing that future CO 

dreionr will not increase or by conduetirtg ueawida lodeling* 

PreFarmb1yl tha Stare 6hoUU carry ~ut hot-spot robeling that is 

cansistent via the [RCIYised), in 

8-r to_.~*lil.r, if 

the nonattainuurt prob1em ia related to a pattern of hot-spats . 

then hat-spbt mdeling should generally be OOnductrLI.. However, hot-spot rodeling ir not2 autcmatically requirad. .For example, if 

+Rc nonattminnmnt problem warn relatsd molely to etationary point 

sources, or if highvay fasrovemmnts havrs been irparaented and the 

sssoc atcd omfarion reductions and travel characterimtics can tw? 

-lit i tively bacumantsd, them hot-spot~modrlinq is not required., 

m such cacree, adequate cbcumentation as well as the: concurrence 

of Headguartmrr is nded. 

Any aseumptimr concerning 6tmi~810n rates lumt reflect 

permanent, enforceable wasures. In ether words, a Shte 

generally cannot take credit in the maintekmce demonstration for 

rcrBuctions unl- th- .re mqulatierun An place -pairing those 

reductions or-- reducticms are otplrnsise &own ta be perarmant., 

Thmf ore, the State will be to raintatn its ipplmentml control stntmgy Qe8pite r*de= to attainment, unless such 

measures are ohawn to be umetz~~ssary for maim-e or are 

replecod with ~errsums that mchirnre equivalent recluctions [see 

additiamal disms8ion under *Centingency Plana). .Smbsin 

~sdo&ons fror: abu-5 bur bs to~~~amzad, nt and wt)u crt.nt mt atwe mlr-s tmwc:%ZY 

mS&acQM ia ma gZP! and all- applScable palmits hat'e been 

i*lt@ ac;corrlfngl$. 

Modeling used to dcmanatrato attainment may be relied upn in Ule raintanance dcnnastratian where the lsodslincj aan 

ent EPA gui4arrce Uid uherm the !!itate has projected no 

ifiaant cbmqms in the KrdQling inputs during the i 

time. Where tQe original attainwnt denonstration nay no 

reabed upon, States will. bs WpCtaM to remoasr using 

+he ~~~-8pproved ling guidance may ba farcnd in +he 

following Wumente: abuidalina on Air Quality UadeLs 

(~evisud],~ OAQPS, R!CP, UC ~~A-450/2-'78-02?R)r Ju.ly 1984; and 

"P#-LQ SIP I)IMcslop~~t. Guideline,* WPS, RTP, #C (EPh-450/2-86- 

0013, Ywm 3983- 
EPA referenced tecbniquas.9 mis may he necessary Where, for 

example, there has been a change in emissions or a change in the 

siting of new 6ourcrcs or modifications such the+ air quality may 

no ~bnver- rk' &ezuw~5'p ..xv~entBd by the existing mdelirqg 

Once an area has Men lvdesignated, the State ehould 

continue to operate an appropriate air quality mnitoring netwurk, in accordance with 40 CFB Part 58, to verify the 

atanwnt status of ths area. The maintenance plan sbould 

contain provisions for eantinucd operation of air qu.ality ranitars.that will provide such verifiaation. In cwsas when 

masurd mobile source parameters (reg., vehicle miles traveled 

congeetien) bave changed over time, the hte may also need to 

pUfoZlE a saturation monitoring atudy ta determine Wm need for, 

and lacation of, aU6tiwral pcr'~~~cnIt memitors. 

. . d. - verlfliMItfan of 

Each should mure that 'i~-h.. the lagal arrthoriey to 

implement and enforce all reasurer necessary to attiin and to 

maintain the IOMQS. Sectians 110(a) (2) (B) and (P) ,of the Clean 

Air Act, 8s ammdeb, and regulations proaulgatea at 40 CPR 

Sl.llO(k), suggest #at one such measure is tha acquisition of 

ambient and souree- errSssion data to demonstrate attainment and 

maintenance. 

Regardless of whether the maintenance demonstration fs.based - 

on a showinu that future mission inventories will not eaccee4 the 

attainment inventory or on abodeling, the S-te suJmitta2 shouLd 

inbicsta the state will tra~k me aP +he maintenance 

Ip%&- This is necessary due to the faet.that the emission 

projections ~rade for the wlnt- demmmtration depend on 

rasunptions of point and we8 eource growth. 

one option for tractking the progress of tne maintenance 

demonstration, provided bere a8 an errample, wotikd lxs for the 

State to periafcally update the emisrions inventory. In this 

case, the maintsnancm plan should specify the frequency of any planned invanwry updates, Such an updata could be baaed, in 

part, on the annual AIRS update .nd could indicute nmw source 

growth and other &magus ffar the attainment inventary (e,g., changes in vehicle ailam travelled or in txaffic patterns), As 

an alternative to a complete update of the inventalry, the state 

may choose to do a ceaprehen.dvcl review of the fa~ters that were 

used in developing the attainrent inventory to shew no 

sfgnlficant cburqe. If as review does shew a 83-gnificant . 

change, the State should then perform an update of the inventory. 
Where the demomtzation is based on modeling, m option fob 

rrrcklnq prapress would be for th. State to periodically 

(typically every 3 years) reevaluate the model* uk~tians aM 

input data, In any event, the State should aonit~r the - 

inatcatoms for triggering contingency maeures (as dlectl&sed 

below). 

Section 1751 of the ~ct also requires that a aalntenance 

plan inc2uba, oontimgemcp provirlom, as necessaty, to pc08ptly 

correct any violation of t&e #MQS that occurs after 

rsdesignation mf tbr ar:m. These ~~ntingeney aeasmrr are 

distinguished from those generally rvguired for nonattairmrent 

anas undex seetion 172(c)(9).md those spadfioally mired for 

0 and CO notiattainment areas under nections 182(c)(9) dnd 

aa7(r)(3), rupecti.yely. Por tha.purpocms ot .-ion 175A. a ' 

State is not mired to have fulZy rdoptd amtingency measures 

th&t will taka eZ2em wWkmch FH- wa. hv, the State in 

order far the maintenance plan to be approved. Rowever. the 

continqancy plan,ir considered to be an anforceable part t?f Me 

SIP and should ensure that the contingency mommres ure adopted 

expediently once they are triggered. The plm .ehUULb cz-rly 

identify Ole Wa6UTes - to be abop-, a s&e&&r .nd pzase&ure far 

&option and iiap1-tation, and; a epe~iffc &me for action 

by the Stat& U r necmmazy of sthe Nut, the State shoaald 

alsa iddhtify rp.cifie indicators, or triqgerto, whir* will be 

used ?s deterwine when t.b contingurcy redSlures need to ba 

implementad. 

Utmre the maintenance aemonetration is twmed en tb6 . 

inventory, the Stata may, for example, idenrify sn nmction level@ 

of emissions as the indicator, rf later invantary-updates show 

that the inventory has etcceeded the action level, the Sate would 

take tlse necessary steps to implement the oontingenoy measures. 

The.inUicators would allow a.State to take early action to 

address potential vdolations'of the NMOS beform they occur.. By taking early action, States ray be able to.preourt any actual 

violations of the NMQS and, therefore, rlirfnata the need on tka 

park of EPA to siqnate an area to nonattainment;, 

ez indicators ta consider include monitored or eeled 

violstions of tile PAAQS [due to the inadequacy of aronitoring da%a 

An same situations); xt is important to note that air quality 

data in excess of the WQs will not autoraticelly necrssitate a 

rwislon of the SfP mere implamentation of ccurtinqency ueaswes 

is adequate to rddrei~ t&e cause of the violation. The need fez 

a SlF revioisn is subject tm the AdPinistrator@r dieeretion. 

Tne SPA will review what constitutes a contingency plan err a 

case-by-case Baris. && c it, map!& d~equPfa--~ );ha State 

eiF1I fa&lenmt a&L nemtw(b8 amtained fn the 9- D nomttafnment 
aW&%m@Bm ' WWC ~~4,~~~~~~

1 2 

Thls language suggests that 8 State may submit a SIP revision at 

the tire of its rebesignation request to ~UOVQ or reduce the 

stringency of control masures. Such 8 revision can be approved - 

by EPA if it provfdes for compensating equivalent reductions. A 

deromtration thmt rrrirsures are equivalent would have to include 

ap-riate 8Wellng or m adrqwtm justificcrtiwr. Alternatively, a State right k able ta deamstrate (+hrough 

EPA-rppmved Waling) that the ma6ure.s ars met nacassary for 

8aintenance of the standard. In either case, the contingency plan wUU heve to provide for impleaendation of any reaeures 

that ware reduced or reaovsd after reUesignation of the area. 

AP stated previously, this memorandum coneolida.tes BPAos 

redesignistien and ralntemnat plan guidance Md Region6 should 

rely tlpan it as a general framwrk in drafting 

mathas. It -is atronqly suggoatad that the Rogional Off ices 

ahare this'docurent witb the appropriate States. Ttria should 

- give the Stat- a hettar Unaerstanding of what is o:geetQd from a 

redesfgnation request and maintenance plan under exj-sting policyMy nrcessary =hangas to existing Agency policy will be made 

through our action on specific rebesignation reques155 and the 

rev&- of saction 17SA maintenance plans for these lmrticular 

areas, bth of mich are subsect- tb notktt anuacoamrn~rp.r&aanki~qmdures. Thus, in applying thin memo&um to specific circurrstancas in a rulemaking, Regions should mnsider the 

applicability of the underlying policies to Me -icular facts 

and to comments submitted by any petson. If your si;rff.wmbers have questions which wire clar&ticatfon, they may contacrt 

Sharon Reindets at (919) 511-5284 for 03- md CCbre'1ated issues, 

and Eeio Ginsburg at (919) 541-0877 for SO2-, M-20.-. and 

Pb-related! issues. 

ec: Chief, Air Branch, rCegf f-X 

John Csbaniss, OMS 

Denise Devae, OAQPS 

Bill LwfoR, TSD 

Rich Oesias. OGC 

John Rasnic, 

Jahn seitz, 

Hike Shapira, OAR 

Lydia Weqaan, QAQPS