I,

UNITED STATES ENVIRONMENTAL PROTECTION AGE

Office of Air Quality Planning and Standards

Research Triangle Park, North Carolina 27711

4SEP 1992

MEMORANDUM

iUR l'BOGRAMS BRAHCl

~J?nnf1

SUBJECT: Procedures for Processing

to Attainment

FROM:

TO:

Purpose

John Calcagni, Directo~~z==

Air Quality Management

Director, Air, Pestic' es and Toxics 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

Areas

The Office of Air Quality PlannIng and Standards (OAQPS)

expects that a number of redesignation requests will be submitted

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

the applicable procedures for handling these requests, including

maintenance plan provisions. This memorandum, therefore,

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

guidance regarding the processing of requests for redesignation

of nonattainment areas to attainment for ozone (03)' carbon

monoxide (CO), particulate matter (PM-lO), sulfur dioxide (S02)'

nitrogen dioxide (N02), and lead (Pb). Regions should use th1s

guidance as a general framework for drafting Federal Register

notices pertaining to redesignation requests. Special concerns

for areas seeking redesignation from unclassifiable to attainment

will be addressed on a c~se-by-case basis.

Background

section l07(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:
.,,-...

2

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

quality is du~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. The 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 to the guidance will be considered on

a case-by-case basis.

1. Attainment of the Standard

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 monitoring 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

quality-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 03, 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 3 must rely on

3 complete, consecutive calendar years of quality-assured air

quality monitoring data, collected in accordance with 40 CFR 50,

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

the NAAQS if there are no violations, as determined in accordance
r'..~,

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

of quality-assured monitoring data. For 502' 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 m~deling. No such supplemental modeling is required

for 03 nonattainment areas seeking redesignation. Modeling may

be necessary to determine the representativeness of the monitored

data. For pollutants such as s02 and CO; a small number of

monitors typically is not representative of areawide air quality

or areas .of highest concentration. When dealing with s02' 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 sources'

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 be

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.

2. state Implementation Plan (SIP) Approval

The SIP for the area must be fUlly approved under section

110(k),1 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 to

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.

1Sec tion 110(k) contains the requirements for EPA action on

plan submissions. It addresses completeness, deadlines, full and

partial approval, conditional approval, and disapproval.
3.

4

Permanent and Enforceable Improvement in Air Quality

....-.

The state must be able to reasonably attribute the

improvement in air quality to emission reductions which are

permanent and enforceable. 2 Attainment resulting from temporary

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

shutdown due to temporary adverse economic conditions) or

unusually fav~rable meteorology would not qualify as an air

quality improvement due to permanent and enforceable emission

reductions.

In making this showing, the state should estimate the

percent ~eduction (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 0 Requirements

For the purposes of redesignation, a state must meet all

requirements of section 110 and Part 0 that were applicable prior

to submittal of the complete redesignation reque~t. When

evaluating a redesignation request, Regions should not consider

whether the state has met requirements that come due under the

Act after submittal of a complete redesignation request. 3

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

memorandums; interested parties should consult with QAQPS 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 0

remain 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 .

..
5

-- However, 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.

To avoid confusion concerning what requirements will be

applicable for purposes of redesignation, Regions should

encourage State~ to work closely with the appropriate Regiqnal

Office early irr 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 EPA disapproves

the redesignation request or if the request is invalidated

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

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

nonattainment plans. Most of the provisions of this

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

provide guidance on these requirements as needed. 4

for

section are

We will

b. Part D Requirements

Part D consists of general requirements applicable to all

areas which are designated nonattainment based on a violation of

the NAAQS. 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,

S02' N02, 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 requirements

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 03 and CO area,

which is classified, must meet all applicable requ~rements 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).
6

Nonattainment Areas," respectively, before the area may be

redesignated to attainment. All PM-I0 nonattainment areas

(Whether classified as moderate or serious) must similarly meet

the applicable general provisions of SUbpart 1 and the specific

PM-I0 provisions in subpart 4, "Additional Provisions for

Particulate Matter Nonattainment Areas." Likewise, S02' N02, and

Pb nonattainme~t areas are subject to the applicable generql

nonattainment provisions in SUbpart 1 as well as the more

specific requirements in subpart 5, "Additional Provisions for

Areas Designated Nonattainment for Sulfur Oxides,Nitrogen

Dioxide, and Lead."

i. Section 172(c) Reguirements

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

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. Conformity

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,
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the 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 mee~s the requirements of section 175A. 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.

section l75A defines the general framework of a maintenance

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 further

states that the plan shall contain such additional measures, if

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

Act requires a demonstration of maintenance for 10 years after an

area is redesignated (not 10 years after submittal of a

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

",.-. for EPA 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 necessary for EPA review

and approval action on the redesignation request. In determining

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 redesignation

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 for

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
8

nonattainment to attainment. We therefore recommend that states

seeking redesignation of a nonattainment area consider these

provisions. However, any final EPA determination regarding 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. Attainment Inventory

The state should develop an attainment emissions inventory

to identify the level of emissions in the area which is

sufficient to attain the NAAQS. 5 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 , N0 2, and

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

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

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

5Where the State has made an adequate demonstration that air

quality 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.

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

inventories for 0 and CO nonattainment areas is contained in the

following documenfs: "Procedures for the Preparation ot 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 Plans" (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 S02. 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.
9

-- according to Clean Air Act section l89(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/yearsize thresholds (e.g., areas with smaller source size

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

program, these ~ources need only be addressed in the aggre9ate to

the extent that: they result in areawide growth.

For 03 nonattainment areas, the inventory should be based on

actual "typical summer day" emissions of-03 precursors (volatile

organic compounds and nitrogen oxides) dur1ng 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 be

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 inventory,

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 applicable NAAQS. For

these areas, the maintenance demonstration should be based upon

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

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

inventory approach. In both instances, the demonstration should

be for a period of 10 years following the r~esignation.

c=- -

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 control

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

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 the

state should project emissions for the 10-year period following

redesignation, either for the purpose of showing that emissions

will not ~ncrease over the attainment inventory or for conducting

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.
10

with the attainment inventory, and should document data inputs

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

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

consistent with current EPA modeling guidance. 8 For 0 3 and CO,

the projected emissions should reflect the expected actual

emissions based on enforceable emission rates and typical

production rat~s.

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 Quality 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 relied 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 be 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.
·,

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..,-. EPA referenced techniques. 9 This may be necessary where, for

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

siting of new sources or modifications such that air quality may

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. The 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 traveled

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

perform a saturation monitoring study to determine the need for,

and location of, additional permanent monitors.

d. verification of continued Attainment

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Each State should ensure that it has the legal authority to

implement and enforce all measures necessary to attain and to

maintain the NAAQS. sections 110(a)(2){B) and (F) of the Clean

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 based

on a showing that future emission inventories will not exceed the

attainment inventory or on modeling, the state submittal should

indicate how the state will track the progress of the maintenance

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). As

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

may choose to do a comprehensive review of the factors that were

used in developing the attainment inventory to show no

significant change. If this review does show a significant

change, the State should then perform an update of the inventory.

9s ee references for modeling guidance cited in footnote 8.

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/-- Where the demonstration is based on modeling, an option for

tracking 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. contingency 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 redesign~tion 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

1a7(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 0 nonattainment

-------,~-~,~_._---
,"

13

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

This language suggests that a state may submit a SIP revision at

the time of its redesignation request to remove or reduce the

stringency of control measures. Such a revision can be approved

by EPA if it provides for compensating equivalent reductions. A

demonstration that measures are equivalent would have to include

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

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

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.

Summary

As stated previously, this memorandum consolidates EPA's

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

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 members

have questions which require clarification, they may contact

Sharon Reinders at (919) 541-5284 for 03- and CO-related issues,

and Eric Ginsburg at (919) 541-0877 for S02-' PM-I0-, 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