~ pAOORA)1Ss BRANCl 

' A f F UNITED STATES ENVIRONMENTAL PROTECTION AGE 

Office of Air Quality Planning and Standards 

Research Triangle Park, North Carollna 27711 $EP Q 1992 

4 $ E P 1992 

EPAMREQIOId IV 

ATLANTA. OA. 

MEMORANDUM 

SUBJECT: Procedures for Processing Requestsedesignate. to 

to Attainment / / l ~'/7 

FROM: John Calcagni, Directo 

Air Quality Management ivisio - 

TO: Director, Air, Pestic' es and Toxics nage nt 

Division, Regions I and IV 

Director, Air and Waste Management Division, 

Region II 

Director, Air, Radiation and Toxics Division, 

Region III 

Director, Air and Radiation Division, 

Region V 

,Director, Air, Pesticides and Toxics Division, 

Region VI 

Director, Air and Toxics Division, 

Regions VII, VIII,.IX, and X 

Purnose 

The Office of Air Quality Planning and Standards (OAQPS) 

expects that a number of redesignation requests will be submit 

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

the applicable procedures for handling these requests, includi 

maintenance plan provisions. This memorandum, therefore, 

consolidates the Environmental Protection Agency's (EPA's) 

guidance regarding the processing of requests for redesignatio 

of nonattainment'areas to attainment for ozone (0 3 ) 1 carbon 

monoxide (CO), particulate matter (PM-10), sulfur dioxide (SO Z 

nitrogen dioxide (NO2), and lead (Pb). Regions should use thi 

guidance as a general framework for drafting Federal Register 

notices pertaining to redesignation requests. Special concern 

for areas seeking redesignation from unclassifiable to attainm 

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

~ . . . 

Section 107(d)(3)(E) of the Clean Air Act', as amended, 

states that an area can be redesignated to attainment if the 

following conditions are met: 
1. The EPA has determined that the national ambient air 

quality standards '(NAAQS) have been attained. 

2. The applicable implementation plan has been fully 

approved by EPA under section 110(k). 

3. The EPA has determined that the improvement in air , 

quaiity is due to permanent and enforceable reductions in 

emissions. 

4. The State has met all applicable requirements for the 

area under section 110 and Part D. 

5. Ttie EPA has fully approved a maintenance_.plan, including 

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

Each of these criteria is discussed in more detail in the 

following paragraphs. Particular attention is given to 

maintenance plan provisions at the end of this document since 

maintenance plans constitute a new requirement under the amended 

Clean Air Act. Exceptions . tothe guidance will'be considered on 

a case-by-case basis. 

, - ~ • e - . ~ •- • 

The State must show that the area is attaining the 

applicable NAAQS. There are two components involved in making 

= this demonstration which should be considered interdependently. 

The first component relies upon ambient air quality data. The 

data that are used to demonstrate attainment should be the 

product of ambient monitoiing that is representative of the area 

of highest concentration. These monitors should remain at the 

same location for the duration of_the monitoring'period required 

for demonstrating attainment. The data should be collected and 

qualfty-assured.in accordance with 40 CFR 58 and recorded in the 

Aerometric Information Retrieval System (AIRS) in order for it to 

be available to the public for review. For purposes of 

redesignation, the Regional Office.should verify that the 

integrity of the air quality monitoring network has been 

preserved: 

For.PM-10, an area may be considered attaining the NAAQS if 

the number,of expected exceedances per year, according to 40 CFR 

50.6, is less than or equal to 1.0. For 0 31 the area must show 

that the average,.annual number of expected exceedances, according 

.to 40 CFR 50.9, is less than or equal to 1.0 based on data from 

all monitoring sites in the area or its affected downwind 

environs. In making this showing, both PM-10 and 0 3must rely on 

3 complete,_.:consecutive,,calendar :years. ~ of>.,quality-assured ~ ,pair= _.- rquality monitoring data, collected in accordance with 40 CFR 50, 

Appendices H and K. For CO,.an area may be considered attaining 

the NAAQS if there are no violations, as determined in accordance 
3 

with 40 CFR 50.8, based on 2 complete, consecutive calendar years 

of quality-assured monitoring data. For S0 21 according to 40 CFR 

50.4; an.area must show no more than one exceedance annually and 

for Pb, according to section 50.12, an area may show no 

exceedances on a quarterly basis. 

The second component relies upon supplemental EPA-approved 

air quality modeling. No such supplemental modeling is required 

for 03nonattainment areas seeking redesignation. Modeling may 

be necessary to determine the representativeness of-the ~ monitoied 

data. For pollutants such as S0 2and CO ; a small number of 

monitors typically is not representative of areawide air quality 

or areas of highest concentration. When dealing with S0 2 , Pb, 

PM-10 (except for a limited number of initial moderate 

nonattainment areas), and CO (except moderate areas with design 

values of 12.7 parts per million or lower at the time of passage 

of the Clean Air Act Amendments of 1990), dispersion modeling 

will generally be necessary to evaluate comprehensively sourcei' 

impacts and to determine the areas of expected high 

concentrations based upon current conditions. Areas which were 

designated nonattainment based on modeling will generally not }ie 

redesignated to attainment unless an acceptable modeling analysis 

indicates attainment. Regions should consult with OAQPS for-. 

further guidance addressing the need for modeling in specific 

circumstances. 

~-; 

State Implementation Plan (SIP) Aooroval 

Thy SIP for the area must be fully approved under section 

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

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

and the redesignation request may occur simultaneously.. An area 

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

subject of a disapproval; a finding of failure to submit or tol 

implement the SIP; or partial, conditional, or limited approval. 

However, this does not mean that earlier issues with regard to 

the SIP will be reopened. Regions should not reconsider those 

things that have already been approved and for which the Clean 

Air Act Amendments did not alter what is required. In contrast, 

to the extent the Amendments add a requirement or alter an 

existing•requirement so that it adds something more, Regions 

should consider those issues. In addition, requests from areas 

known to be affected by dispersion techniques which are 

inconsistent with EPA guidance will continue to be considered 

unapprovable under section 110 and will not qualify for 

redesignation. 

1 Section 110(k) contains the requirements for EPA action 

plan submissions. It addresses completeness, deadlines, full 

partial approval, conditional approval, - and disapproval. 
3." P manent_and Enforceable Imorovement in Air Ou_alit 

The State must be able to reasonably attribute the 

improvement in air quality to emission reductions which are 

permanent and enforceable. 2Attainment resulting from temporary 

reductions in emission rates (e.g., reduced production or 

shutdown due to temporary adverse economic•conditions) or 

unusually favorable meteorology would not qualify as an air 

quality improvement due to permanent and enforceable emission 

reduc*_ions< 

In.making this showing, the State should'estimate the 

percent reduction (from the year that was used to determine the 

design value for designation and classification) achieved.from 

Federal measures such as the Federal Motor Vehicle Control 

Program and fuel volatility rules as well as control measures 

that have been adopted and implemented by the'State. This . 

estimate should consider emission rates, production capacities, 

and other related information to clearly show that'the air . 

quality improvements are the result of implemented controls. The 

analysis should assume that sources are operating at permitted 

levels (or historic peak.levels)•unless evidence is presented 

that such an assumption is unrealistic. 

4. Section 110 and Part D Requirements - 

For the purposes of redesignation, a State must meet all 

- requirements of section 110 and Part D that were applicable prior 

to submittal of the complete redesignation request. when 

evaluating a redesignation request, Regions shouid not consider 

whether the State has met requirements that come due undir the 

Act after submittal of a complete redesignation request.. 

2This is consistent with EPA's existing policy on 

redesignations as stated in an April 21, 1983 memorandum titled 

"Section 107 Designation Policy summary." This memorandum states 

that in order for an area to be redesignated to attainment, the 

State must show that "actual enforceable emission reductions are 

responsible for the recent air quality improvement." This 

element of the policy retains its validity under the amended Act 

pursuant to section 193. [Note: other aspects of the April 21, 

1983 memorandum have since been superseded by subsequent 

meinorandums;"interested parties should consult with oAQPS before 

relying on these aspects, e.g. those relating to required years 

of air quality data.] 

3Under section 175A(c), however, the requirements of Part D 

remairn--in.force: and.-effect for- the area until such , time`, as it , is •- 

redesignated. Upon redesignation to attainment, the requirements 

that became due under section 175A(c) after submittal of the 

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

redesignation request must be fully approved into the plan at 

before the time EPA redesignates the area. 

To avoid confusion concerning what requirements will be 

applicable for purposes of redesignation, Regions should 

encourage States to work closely with the appropriate Regional 

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

redesignation request submitted by the State has a high 

likelihood of being approved by EPA. Regions'should advise 

States of the practical planning consequences if SPA disapprov 

the redesignation request or if the request is invalidated. 

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

circumstances, EPA does not have the discretion to adjust - 

schedules for implementing SIP requirements. As a result, an 

area may risk sanctions and/or Federal implementation plan 

implementation that could result from failure to meet SIP 

submittal or implementation requirements. ' 

a. Section 110 Requirements 

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

nonattainment plans. Most of the provisions of this section 

the same as those contained in the pre-amended Act. We will 

provide guidance on these requirements as needed. 4 

b. Part D Requirements 

Part D consists of general requirements applicable to all 

areas which are designated nonattainment based on a violation o 

the NAAQS. The general requirements are followed by a series o 

subparts specific to each pollutant. The general requirements 

appear in subpart 1. The requirements relating to 0 3 , CO, PM-1 

S021 NO2 , 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 as one of the 

pollutant-specific subparts, the general provisions may - be 

subsumed within, or superseded by, the more specific requiremen 

of subparts 2 through 5. 

If an area was not classified under section 181 for 03, or 

section 186 for CO, then that area is only subject to the 

provisions of subpart 1, "Nonattainment Areas in General." In 

addition to relevant provisions in subpart 1; an 0 3and CO area 

which is classified, must meet all applicable requirements in 

subpart 2, "Additional Provisions for Ozone Nonattainment Areas 

and subpart 3, "Additional Provisions for Carbon Monoxide 

4General guidance regarding the requirements for SIP's may 

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

Air Act Amendments," 57 FR 13498 (April 16, 1992). 
0 

Nonattainment.Areas," respectively, before the area may be 

redesignated to,attainment. A11 PM-10 nonattainment areas 

(whether classified as moderate or serious) must similarly meet 

the applicable generai provisions of subpart 1 and the specific 

PM-10 provisions in subpart 4, "Additional Provisions for 

Particulate Matter Nonattainment Areas." Likewise, S0 2 , NO2, and 

Pb nonattainment areas are subject to Lhe applicable generai 

nonattainment.provisions in subpart 1 as well as the more 

specific requirements in subpart 5, "Additional Provisions for 

Areas Designated;Nonattainmeiit £or Sulfur Oxides, Nitroqen 

Dioxide, and Lead." 

- • -• - i~ - ~ . 

This section contains general requirements,for nonattainment 

plans. A thorough discussion of these requirements may be found 

in the General Preamble to Title I[57 FR 13498 (April 16; 

1992)]: The EPA anticipates that areas will already have met 

most or all of these requirements to the extent that they are not 

superseded by more specific Part D requirements. The 

requirements for reasonable further progress, identification of 

certain emissions increases, and other measures needed for, 

attainment will not apply for redesignations because they only 

have meaning for areas not attaining the standard. The 

requirements for,an emission inventory will be.satisfied by the 

;< inventory requirements of the maintenance plan. The requirements 

~ z= of the Part D new source review program will be replaced by the 

prevention of significant deterioration (PSD) program once the 

area has been redesignated. However, in order to ensure that the 

PSD program will become fully effective immediately upon 

redesignation, either the State must be delegated the Federal PSD 

program or the State must make any needed modifications-to its 

rules to have the approved PSD program apply to the affected area 

upon redesignation. , 

ii. ,conformitv 

The State must work with EPA to show that its SIP 

provisions are consistent with section 176(c)(4) conformity. 

requirements. The redesignation request should include 

conformity procedures, if the State already has these procedures 

in place. Additionally, we currently interpret the conformity 

requirement to apply to attainment areas. However, EPA has not 

yet issued its conformity regulations specifying what areas are 

subject to the conformity requirement. Therefore, if a State 

does not have conformity procedures in place at the time that it 

submits a redesignation request, the State"must commit to follow 

EPA's conformity regulation upon issuance, as applicable. If the 

State submits the'redesignation'request'subsequent°to EPA"s'' 

issuance of the conformity regulations, and the conformity 

requirement became applicable to the area prior to submission,• 
7 

th'e State must adopt the applicable conformity requirements 

before EPA can redesignate the area. 

5. Maintenance Plans 

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

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

plan which meets the requirements of section 1775A. A State may 

submit both the redesignation request and the maintenance plan at 

the same time and rulemaking on both-may proceed on a parallel 

track. Maintenance plans may, of course, be submitted and 

approved by EPA before a redesignation is requested. However, 

according to section 175A(c), pending approval of the maintenance 

plan and redesignation request, all applicable nonattainment area 

requirements shall remain in place. I 

Section 175A defines the general framework of a maintenanc 

plan. The maintenance plan will constitute a SIP revision and 

must provide for maintenance of the relevant NAAQS in the area 

for at least 10 years after redesignation. Section 175A furthe 

states that the plan shall contain such additional measures, i1 

any, as may be necessary to ensure such maintenance. Because t 

Act requires a demonstration of maintenance for 10 years after 

area is redesignated (not 10 years after submittalof a 

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

r for EPA action on the request. In other words, the maintenance 

demonstration should project maintenance for 10 years, beginnir 

- from a date which factors in the time necessary for EPA review 

and approval action on the redesignation request. In determini 

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

section 107(d)(3)(D) grants the Administrator up to 18 months 

from receipt of a complete.submittal to process a redesignatior 

request. The statute also requires the State to submit a 

revision of the SIP 8 years after the original redesignation 

request is approved to provide for maintenance.of the NAAQS foi 

an additional 10 years following the first 10-year period [see 

section 175A(b)]. 

In addition, the maintenance plan shall contain such 

contingency measures as the•Administrator deems necessary to 

ensure prompt correction of any violation of the NAAQS [see 

section 175A(d)]. The Act provides that, at a minimum, the 

contingency measures must include a requirement that the State 

will implement all measures contained in the nonattainment SIP 

prior to redesignation. Failure to maintain the NAAQS and 

triggering of the contingency plan will not necessitate a 

revision of the SIP unless required by the Administrator, as 

stated in section 175A(d). 

The following is a list of core provisions that we 

anticipate will be necessary to ensure maintenance of the 

relevant NAAQS in an'area seeking redesignation from 
0 

nonattainment to attainment.. We therefore recommend that States 

seeking redesignat'ion of a nonattainment area consider these 

provisions. However, any final EPA determination regardinq the 

adequacy of a maintenance plan will be made following review of 

the plan submittal in light of the particular'circumstances 

facing the area proposed for redesignation and based on all 

relevant information available at the time. 

a . 

a. . P:ttainment Inventory 

The State should develop an attainment emissions inventory 

to identify.the level of emissi ~ns in the area which is 

sufficient to attain the NAAQS. This inventory should be', 

consistent with EPA's most recent guidance on emission 

inventories for nonattainment areas available at the time and 

should include the emissions during the time period associated 

with the monitoring data showing attainment. 6 

Source size thresholds are 100 tons/year for SO 2, NO 2, and 

PM-10 areas, and 5 tons/year for Pb based upon 40:CFR 51.100(k) 

and 51.322, as well as established practice for AIRS data. The 

source size threshold for serious PH-10 areas is 70 tons/year 

SWhere the State has made an adequate demonstration that air 

quali ty has improved as a result of the SIP (as discussed 

previously), the attainment inventory will generally be the 

actual inventory at the time the area attained the standard. 

6 The EPA's current guidance on the preparation of emission 

inventories for O3and co nonattainment.areas is contained in the 

following documents:, "Procedures for the Preparation of Emission 

Inventories for Carbon Monoxide and Precursors of Ozone: Volume 

I" (EPA-450/4-91-016), "Procedures for the Preparation of 

Emission Inventories for Carbon Monoxide and Precursors of Ozone: 

Volume II" (EPA-450/4-91-014), "Emission Inventory Requirements 

for Ozone State Implementation Plans" (EPA-450/4-91-010), 

"Emission inventory Requirements for Carbon Monoxide 

Implementation PlanB" (EPA-450/4-91-011), "Guideline for 

Regulatory Application of the Urban Airshed Model" (EPA=450/4-91- 

013), "Procedures for Emission Inventory Preparation: Volume IV, 

Mobile Sources" (EPA-450/4-81-026d), and "Procedures for 

Preparing'Emission Inventory Projections" (EPA-450/4-91-019). 

The EPA does not currently have specific guidance on attainment 

emissions inventories for S0 2 ', In lieu thereof, States are 

referred to the guidance on emissions data to be used as input to 

modeling demonstrations, contained in Table 9.1 of EPA's 

"GUideline on Air Quality Models (Revised)" (EPA-450/2-78-027R), 

July 1987,.,which_is,generally applicable to,all,criteria... 

pollutants." Emission inventory'procedures and requirements 

documents are currently being prepared by OAQPS for PM-10 and Pb; 

these documents are due for release by summer 1992. 
F] 

according to Clean Air'Act section 189(b)(3). However, the 

inventory should include sources below these size thresholds if 

these smaller sources were included in the SIP attainment 

demonstration. Where sources below the 100, 70, and 5 tons/yee 

size thresholds (e.g., areas with smaller source size 

definitions) are subject to a State's minor source permit 

program, these sources need only be addressed in the aggreqate 

the extent that'they result in areawide growth. 

,

For 03nonattainment areas, the inventory should be based 

actual "typical summer day" emissions of 0 3precursors (volati: 

organic compounds and.nitrogen oxides) during the attainment 

year. This will generally correspond to one of the periodic 

inventories required for nonattainment areas to reconcile 

milestones. For_ CO nonattainment areas, the inventory should 1 

based on actual "typical CO season day" emissions for the 

attainment year. This will generally correspond to one of the 

periodic inventories required for nonattainment areas. 

b. Maintenance Demonstration 

A State may generally demonstrate maintenance of the NAAQS 

by either showing that future emissions of a pollutant or its 

precursors will not exceed the level of the attainment inventor 

or by modeling to show that the future mix of sources and 

=' emission rates will not cause a violation of the NAAQS. Under 

the Clean Air Act, many areas are required to submit-modeled 

' attainment demonstrations to show that proposed reductions in 

emissions will be sufficient to attain the appliaable NAAQS. P 

these areas, the maintenance demonstration should be based upor, 

the same level of modeling. In areas where.no such modeling wa 

required, the State should be able to rely on the attainment 

inventory approach. In both instanees, the demonstration shoul 

be for a period of 10 years following the redesignation. 

Where modeling is relied upon to demonstrate maintenance, 

each plan should contain a summary of the air quality 

concentrations expected to result from application of the contr 

strategy. In the process, the plan should identify and descriY 

the dispersion model or other air quality model used to project 

ambient concentrations (see 40 CFR 51.46). 

In either case, to satisfy the demonstration requirement t 

State should project emissions for the 10-year period followinc 

redesignation, either for the purpose of showing that emissions 

will notj~ ncrease over the attainment inventory or for conducti 

modeling. The projected inventory should consider future 

growth, including population and industry, should be consistent 

7Guidance for projecting emissions may be found in the 

emissions inventory guidance cited in footnote 6. 

to 

on 
10 

with the attainment inventory, and should docyment data inputs 

and assumptions. A11 elements of the demonstration (e.g., 

emission projections, new source growth, and mgdeling) should be 

consistent with current EPA modeling guidance. For O s and CO 3 

the projected emissions should reflect the expected actual 

emissions based on enforceable emission rates and typical 

production rates. 

For CO, a State should address the areawide component of the 

maintenance demonstration either by.showing that future CO• 

emissions will not increase or by conducting areawide modeling. 

Preferably, the State should carry out hot-spot.modeling that is 

consistent with the Guideline on Air ouality Models (Revised), in 

order to demonstrate maintenance of the NAAQS. In particular, if 

the,nonattainment problem is related to a pattern of hot-spots 

then hot-spot modeling should generally be.conducted. However, 

hot-spot modeling is not automatically required. For example, if 

the nonattainment problem was related solely to stationary point 

sources, or if highway improvements have been implemented and the 

associated emission reductions,and travel characteristics can be 

qualitatively documented, then hot-spot modeling is not required. 

In such cases, adequate documentation as well as the concurrence 

of Headquarters is needed. 

Any assumptions concerning emission rates must reflect 

permanent, enforceable measures. In other words, a State 

generally cannot take credit in the maintenance demonstration for 

- reductions unless there are•regulations in place requiring those 

reductions or the reductions are ~ otherwise.shown to be permanent. 

Therefore, the State will be expected to maintain its implemented 

control strategy despite redesignation to attainment, unless such 

measures are shown to be unnecessary for maintenance or are 

replaced with measures that achieve equivalent reductions (see 

additional discussion under "Contingency Plan"). Emission 

reductions from source shutdowns can be considered permanent and 

enforceable to the extent.that those shutdowns have been 

reflected in the SIP and all applicable permits have been 

modified accordingly. 

Modeling used to demonstrate attainment may be:reli.ed upon 

in the maintenance demonstration where the modeling conforms to 

current EPA guidance and where the State has projected no 

significant changes in the-modeling inputs during the intervening 

time. Where the original attainment demonstration may no longer 

be relied upon, States will be expected to remodel using current 

8The EPA-approved modeling guidance may tie found in the 

following documents: "Guideline on Air Quality Models 

(Revised)," OAQPS, RTP, NC (EPA-450/2-78-027R); July 1986; and 

"PM-10 SIP Development Guideline," OAQPS, RTP, NC (EPA-450/2-86- 

001), June 1987. 
~ g 

11 

EPA referenced techniques. yThis may be necessary where, for 

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

siting of new sources or modifications such that air quality 

no longer be accurately represented by the existing modeling. 

C.Monitoring Network 

Once an area has been redesignated, the State should 

continue to operate an appropriate air quality monitoring 

network, in accordance with 40 CFR Part 58, to.verify, the 

attainment status'of the area. mhe maintenance plan should 

contain provisions for continued operation of air quality 

monitors that will provide such verification. In cases where 

measured mobile source parameters (e.g., vehicle miles travele 

conqestion) have changed over time, the State may also need to 

perform a saturation monitoring study to determine the need fo 

and location of, additional permanent monitors. 

d. Verification of Continued Attainment 

Each State should ensure that it has the legal authority 

implement and enforce all measures necessary to attain and to 

maintain the NAAQS.. Sections 110(a)(2)(B) and (F) of the Clea 

Air Act, as amended, and regulations promulgated at 40 CFR 

51.110(k), suggest that one such measure is the acquisition of 

ambient and source emission data to demonstrate attainment and 

maintenance. 

Regardless of whether the maintenance demonstration is b 

on a showing that future emission inventories will not exceed 

attainment inventory or on modeling, the State submittal shou 

indicate how the State will track the progress of the mainten 

plan." This is necessary due to the fact that the emission . 

projections made for the maintenance demonstration depend on 

assumptions of point and area source growth. 

One option for tracking the progress of the maintenance 

demonstration, provided here as an example, would be for the 

State to periodically update the emissions inventory. In this 

case, the maintenance plan should specify the frequency of any 

planned inventory updates. Such an update could be based, in 

part, on the annual AIRS update and could indicate new source 

growth and other changes from the attainment inventory (e.g., 

changes in vehicle miles travelled or in traffic patterns). A; 

an alternative to a complete update of the inventoiy, the Stat 

may choose to do a comprehensive review of the factors that we; 

used in developing the attainment inventbry to show no 

significant change. If this review does show a significant 

change, the State should then perform an update of the invento: 

9See references for modeling guidance cited in footnote 8. 
12 

where the demonstration is based on modeling, an option for 

trackinq progress would be for the State to periodically 

(typically every 3 years) reevaluate the modeling assumptions and 

input data. In any event, the State should monitor the 

indicators for triggering contingency measures (as discussed 

below). 

e. Continqencv Plan 

Section 175A of the Act also requires that a maintenance 

plan include contingency provisions, as necessary, to promptly 

correct any violation of the NAAQS that occurs after 

redesignation of the area. These contingency.measures are 

distinguished from those generally required for nonattainment 

areas under section 172(c)(9) and those specifically required for 

O'and CO nonattainment areas under sections 182(c)(9) and 

N7(a)(3), respectively. For the purposes of section 175A, a 

state is not required to have fully adopted contingency measures 

that will take effect without further action by the State in 

order for the maintenance plan to be approved. However, the 

contingency plan is,considered to be an enforceable part of the 

SIP and should ensure that the contingency measures are adopted 

expediently once they are triggered. The plan should clearly 

identify the measures to be adopted, a schedule and procedure for 

adoption and implementation, and a specific time limit for action 

by the State. As a necessary part of the plan, the State should 

also identify specific indicators, or triggers, which will be 

used to determine when the contingency measures need to be 

implemented. 

, Where the maintenance demonstration is based on the 

inventory,.the State may, for example, identify an "action level" 

of emissions as the indicator. If later inventory updates show 

that the inventory has exceeded the action level, the State would 

take the necessary steps to implement the contingency measures. 

The indicators would allow a State to take early action to 

address potential violations of the NAAQS before they occur. By 

taking early action, States may be able to prevent any actual 

violations of the NAAQS and, therefore, eliminate the need on the 

part of EPA to redesignate an area to nonattainment. 

other indicators to consider include monitored or modeled' 

violations of the NAAQS (due to the inadequacy of monitoring data 

in some situations). It is important to note that air quality 

data in excess of the NAAQS will not automatically necessitate a 

revision of the SIP where implementation of contingency measures 

is adequate to address the cause of the violation. The need for 

a SIP revision is subject to the Administrator's discretion. 

The EPA will review what constitutes a contingency plan on a 

case-by-case basis. At a minimum, it must require that the State 

will implement all measures contained in the-Part D nonattainment 
13 

plan for the area prior to redesignation [see section 175A(d) 

This language suggests that a State may submit a SIP revision 

the time of its redesignation request to remove or reduce the 

stringency of control measures. Such a revision can be appro 

by EPA if it provides for.compensating equivalent reductions. 

demonstration that measures are equivalent would have to incl 

appropriate modeling or an adequate justification. Alternatively, a State might be able to demonstrate (through 

EPA-approved modeling) that the measures are not necessary fo 

maintenance of the standard. In either case, the contingency 

plan would have to provide for implementation of any measures 

that were reduced or removed after redesignation of the area. 

As stated previously, this memorandum consolidates EPA's I 

redesignation and maintenance plan guidance and Regions should 

rely upon it as a general framework in drafting Federal Register 

notices. It is strongly suggested that the Regional Offices 

share this document with the appropriate States. This should 

give the States a better understanding of.what is expected from a 

redesignation request and maintenance plan under existing policy. 

Any necessary changes to existing Agency policy will be made 

through our action on specific redesignation requests and the 

review of section 175A maintenance plans for these particular 

areas, both of which are subject to notice and comment rulemaking 

_ procedures. Thus, in applying this memorandum to specific 

y N circumstances in a rulemaking, Regions should consider the 

applicability of the underlying policies to the particular 'facts 

and to comments submitted by any person. If your staff inembels 

have questions which require clarification, they may contact 

Sharon Reinders at (919) 541-5284 for 0 3- and CO-related issues, 

and Eric Ginsburg at (919) 541-0877 for S0 2 -

1 

 PM-10-, and 

Pb-related issues. 

cc: Chief, Air Branch, Regions I-X 

John Cabaniss, OMS 

Denise Devoe, OAQPS 

Bill Laxton, TSD 

Rich Ossias, OGC 

John Rasnic, SSCD 

John Seitz, OAQPS 

Mike Shapiro, OAR 

Lydia Wegman, OAQPS 

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