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October 6,1995 

MEMORANDUM 

SUBJECT: Limited Maintenance Plan Option for Nonclassifiable CO Nonattainment Areas 

FROM: Joseph W. Paisie. Group Leader 

Integrated Policy and Strategies Group (MD· 15) 

TO: Air Branch. Chiefs, Regions 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 (919) 541·5556 or larry Wallace at (919) 541-

0906 

Auachment 

cc; E. Cummings. OMS 

K. Mclean. OGC 

C. Oldham 

L. Wallace 
AQSSD: [PSG:L W AlJ..ACE: vwyau:xS628:MD-12: I 0-6-95 

W AU.ACE: A:\JOE.ABC 
I. 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 of exceedance levels of the 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 is justifiable and appropriate to apply a different set of 

maintenance plan requirements to a nonclassifiable CO nonauainment areas whose 

monitored air quality is equal to or less than 85 percent of exceedance le~els of the 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 of control 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 of prevention 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. 
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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 for a nonclassifiable CO nonanainmcnt area 10 qualify 

for [he limited maintenance plan 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 of data) used \0 demonstrate attainment, 

mU$! be at or below 7.65ppm (8S percent of exceedanoe levels ortlle orone NAAQS). 

Additionally. the design value for the area muS( continue 10 be at or be low 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 of a 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. 
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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 of core 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 of exceedance 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 of tile 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 of the 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.