### •

October 

### 6,1995 MEMORANDUM SUBJECT: Limited Maintenance Plan Option f or Non classifiable CO Non attainment Areas 

### FROM: Joseph W. Paisie. Group Leader Integrated Policy and Strategies Group (MD· 15) 

### TO: Air Branch. Chiefs, R egions I

-X

On November 16, 1994, EPA issued guidance regarding a limited maintenance plan option for nonclassifiable OWlle nonattainment areas in a memorandum from Sally L Shaver, Diret:tor

. Air Quality Strategies and Standards Division

. to Regional Air Division Directors. EPA believes that such an option is also appropriate for nonclassifiable CO nonanainment areas and 

### tbe following questions and answers set forth EPA's guidanCC' regarding the availability of this option for soch areas. As this is guidance, final and binding determinations regarding the eligibility of areas for the limited maintenance plan option 

### will only 

### be made in the context of notice aod comment rulernaking actions regarding spedfic redesignation requests. If there are any questions concerning the limited maintenance plan option for nondassifiable CO areas, please COlltact me at (9 19) 541·5556 or 

### larry Wallace at (919) 541- 0906 Auachment
cc; 

### E. Cummings. OMS 

### K. Mclean. OGC C. Oldham L. Wall aceAQSSD: [PSG:LWAlJ..ACE: vwyau:xS628: MD-12: I0-6-95 WAU.ACE: A:\JOE.ABCI. 

### Question: 

### 1016195 Limited Maintenance Plan Option for Nonclassifiable CO Nonauainmcnt 

### areas

What requirements must CO**noncla.~sifiable** 

### areas, which 

### are auaining the CO NAAQS with a design value that is signifIcantly below thoe NAAQS, meet in order to have an approvable maintenance plan under section l15A of the Act? Answer: Nonclassifiable CO nonauainment areas seeking redesignation to aUainment whose design**~alues** 

### are at or below 7.65ppm (85 percent ofexceedance levels ofthe CO NAAQS) at the time of redesignation may choose to submit a less rigorous maintenance plan than was formerly required. This new option is being tenned a limited maintenance plan. Nonclassifiable CO areas with design values greater than 7.65ppm will continue to 

### be subject to full maintenance plan requirements described in too September 4, 1992**n~morandum,** 

### "Procedures for Processing Requests to Redesignate Areas to Attainmem," from John Calcagni, former Director of the 

### OAQPS Air Quality Management Division to the Regional Air Division Directors. The EPA now believes that it isjustifiable and appropriate to apply a different set of maintenance plan requirements to a nonclassifi able CO nonauainment areas whose monitored air quality is equal to or less than 85 percent ofexceedance**le~els** 

### ofthe ozone NAAQS. The EPA does not believe that the full maintenance plan requirements need be applied to these areas because they have achieved air quality levels well below the standard without the application ofcontrol measures required by tl.e Act for moderate and serious nonauainment areas. Also, these areas do not have either a recent history of monitored violation of the CO NAAQS or a long prior history of monitored air quality problems. The EPA believes that the continued applicability ofprevention of significant deterioration (PSD) requirements, any control measures already in the SIP. and Federal measures (such as the Federal motor vehicle control program) should provide adequate assurance of ntaintcnance for these areas.2 

### 2. Question :**Be~jdes** having a design value Iha! is equal to or less than 85% of 

### tbe CO NAAQS what OIlier requiremcms are IlCCCSsary f or a nonclassifiable 

### CO nonanainmcnt area 10 qualify for [he limited maintenance pl an opIion?

Answer: To qualify for the limited maintenance plan option. 

### the CO design value for 1be area, 

### based on the 8 COIl.'ie(:utive quaners (2 years ofdata) used \0 demonstrate attainment, mU$! 

### be at or below 7.65ppm (8S percent ofexceedanoe levels ortlle orone NAAQS). Additionally. the design value for the area muS( continue 10 

### be at or below 7.6Sppm unlil the time of final EPA action on the redesignation. 1be method for calculating design values is presented in the June 18, 1990 memorandum. "Oronc and Carbon Monoxide Design Value Calculations," fmm William G. Laxton, former Director of the OAQPS Technical Suppon Division 10 Regional Air Directors

_ The memorandum focuses primarily on determining design values for nonanainmenl areas in order 10 classify [he areas**a~** moderate or serious for CO. Therefore, the document discusses detennining lhe design value for an area based on the monitors which are exceeding the standllJ"d. In the case ofa nonauainment area seeking redesignation 10 auainment, all monitors must he meeting lhe standllJ"d. To assess whether a nooclassiliable area meets the applicability cutoff for the limited maintenance plan, a sepata1e design value must 

### be developed for every moniloring sile. 

### 1lIe highest of these design values is tlx: design value for the whole area. If the area design value is at or below 7.65ppm. the State may select the limited maintenance plan option for the first IO-year maintenance period undCf" seclion 17SA. 

### If the design value for the area exceeds 7.6Sppm prior 10 final EPA action on the rcdesignation, the area no longer qualifies for the limited maintenance plan and must instead submit a full maintenance plan, as indicated in the September 4. 1992 memorandum

.3 

### 3. Question: What elements must be conlsined in a section 17SA rnainlemlllce plan for 

### r"IOoclusifiable CO 

### areas which qualify for the limiled maintenance plan option? 

### Answer: Following is a li51 ofcore provisions which should 

### be iocluded in 

### the limited maintenance plan for CO nonclassifiablc areas. Any fmal EPA determination regarding 

### tbe adequacy of a limited maintenance plan will 

### be made following review oCtile plan subminal 

### in light of the panicularcircumstanc:cs facing the area proposed for redcsignation and b;osed on aU relevant available information.

s. A!!ainmcnt InvenlOry The Slale should develop an anaiomenl emissions im..:ntory to identify a level of emissions in the area which is sufficient 10 anaio 1he NAAQS. This inventory should 

### be eonsistent wilh EPA's most recent guidance' on emissions inventories for DonaUaiomen! arcM available m the lime and should represent emissions during the time 

### period associated with the monitoring data showing attainment. The inventory should 

### be based on actual "typical winter day" emissions of CO. b. Maintenance Pemonst@lioo The maintenance demonstration requirement is considered to 

### be satisfied for nonclassiliable areas if the monitoring data show that tile area is meeting !he air qLlaJity enteria for limited maintenance areas (7.6Sppm or SS% of the CO NAAQS). Thcre is no requirement to project emissions over the maintenance period. 1bc: EPA believes ;fthe area**begin~** the mailllcnance period at or below 

### 8S percent ofexceedance levels. the air quality along with the continLied applicability of PSD requirements, any control measures already in the SIP, and federal meaSUrl:$, should provide adequate assurance of maintenance over the initial 100year maintenance period. When EPA approves a limited maintenance plan. EPA is conclLlding that an emissions budget may be treated as essentially not constraining 

### for the length orthe maintenance



### 'The EPA· s current guidance on the prepar<ltion 

## ot emissions inventories for ozone areas i. contsined in the following documents, "Procedures tor the Preparation of Emission Inventories for Carbon Monoxide and Precursors of Ozone: Volume I" (EPA-450/4-91-016), 'Emission Inventory Requirements for Ozone State Implementation plans" (EPA-4S0/4-91-010J, and 'Procedures for Emission Inventory Preparation: Volume IV, Mobile Sources' (EPA-450/4-81-026dJ.4 

### period because 

### it is unreasonable to expect that such an area will experience so much growth in that period that a violation of the CO NAAQS would result.

c. Monitoring (l/etworkNerificatjoD ofCoD1jpyed AUajnment To verify 

### the attainment status oftile area over the maintenance period. 

### the maintenance 

### plan should contain provisions for continued operation of an appropriate, EPA-approved air quality monitoring network, in accordance 

### with 40 CFR part 

### 58. This is particularly important for areas using a limited maintenance plan b«ause 

### there will 

### be no cap on errusslOOS. 

### d, ContingenCY 

### Plan Section [75A ortlle Act requires that a maintenance plan include contingency provisions, as necessary. [0 promptly correct any violation of 

### the NAAQS that occun: after redesignalion of 

### the ;m,a. 1bese contingency measures do [I()( have 10 be fully adopted at the time of redesignation. However, the oontingency plan is considered to be an enforceable part of too SIP and should ensure that the contingency measures are adopted expeditiously onee they are triggered by a specified event. The contingency plan should identify the measures to be promptly adopted and provide a schedule and procedure for adoption and implementation of the measures. The State should also identify specific indicators, or triggers, which will be used to determine when the contingency measures need to be implemented. While a violation ofthe NAAQS is an acceptable trigger, States may wish to choose a pre-violation action level as a trigger, such as an e,;eeedance of the NAAQS. By taking early action. a State may 

### be able to prevent any actual violation of the NAAQS and, therefore, eliminate any need on the part of EPA to redesignate an area back to nooallainment.

e. CQIlfoanjlY Deleauinatjons Urnkr Limilcd Maintepance Plans The transportation conformity rule (58 FR 62188; November 24.1993) and the general conformity rule (58 FR 63214; November 30, 1993) apply to nonattainment areas and maintenance areas operating under maintenance plans. Under either rule, one means of demonstrating confonnity of Federal actions is to indicate that c,;pocted emissions from planned actions 

### an: consistcnt with the emissions budget for the area. Emissions budgets in limited maintenance plan 3Jl:a5 may be treated as essentially [l(){ constraining for the length of too initial maintenance pcriCK! because il is unreasonable to e,;pect that such an area will e,;perience so much growth in that periCK! that a violation oflhe CO NAAQS would result. In other words. EPA would 

### be concluding that emissions need [l(){ 

### be capped for the maintenance period. Therefore. in areas with approved limited maintenance plans. Federal actions requiring confonnily detenninations under the transportation confonnity rule could 

### be considered to satisfy the "budget test" required in sections 93.118, 93. I 19, and 93.120 of the rule. Similarly, in these areas. Federal actions subject to the generdl conformity rul e could 

### be considered to satisfy the "budget test"5 specified in scc{ioo 93.158(a)(S)(iXA) of

### the rule.