Proposed Requirements for Implementation Plans and Ambient Air Quality Surveillance for Sulfur Oxides (Sulfur Dioxide) National Ambient Air Quality Standards

ENVIRONMENTAL PROTECTION AGENCY

40 CFR Parts 51 and 58

[AD-FRL-5157-7]

Proposed Requirements for Implementation Plans and Ambient Air

Quality Surveillance for Sulfur Oxides (Sulfur Dioxide) National

Ambient Air Quality Standards

AGENCY: Environmental Protection Agency (EPA).

ACTION: Proposed rule.

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SUMMARY: Today's action proposes implementation strategies for reducing

short-term high concentration sulfur dioxide (SO2) emissions in

the ambient air. The EPA is concerned that a segment of the asthmatic

population may be at increased health risk when exposed to 5-minute

peak concentrations of SO2 in the ambient air while exercising.

``Exercising'' in this case can include walking up stairs or hills, as

well as more strenuous activities.

In a related document published on November 15, 1994 in the Federal

Register (part 50/53 document), EPA proposed not to revise the current

24-hour and annual primary national ambient air quality standards

(NAAQS) for sulfur oxides (measured as SO2) while soliciting

comment on the possible need to adopt additional regulatory measures to

address short-term peak SO2 exposures. The three alternatives

under consideration include: Augmenting the implementation of the

existing standards by focusing on those sources or source types likely

to produce high 5-minute peak SO2 concentrations; establishing a

new regulatory program under the authority of section 303 of the Clean

Air Act (Act) to supplement protection provided by the existing

SO2 NAAQS; and revising the existing SO2 NAAQS by adding a

new 5-minute NAAQS of 0.60 ppm SO2, 1 expected exceedance. All

three regulatory alternatives would be implemented through a risk-based

targeted strategy designed to protect the population at risk while

minimizing the burden on the States for implementation.

This document presents EPA's proposed targeted implementation

strategy and the associated regulatory requirements for implementing

each of the regulatory measures under consideration. Also in this

document, EPA solicits comments on appropriate changes to the new

source review (NSR) programs as they relate to the 5-minute NAAQS

regulatory alternative, and EPA [[Page 12493]] proposes to incorporate

appropriate changes to the ambient air quality surveillance

requirements.

DATES: Written comments on this proposal must be received by June 6,

1995. The EPA will hold a public hearing on this document in

approximately 30 days and will announce the time and place in a

subsequent Federal Register document.

ADDRESSES: Submit comments on the proposed revisions to the

requirements for the preparation, adoption, and submittal of

implementation plans (two copies are preferred) to: Office of Air and

Radiation Docket and Information Center (Air Docket 6102), Room M 1500,

U.S. Environmental Protection Agency, Attention: Docket No. A-94-55

(for part 51 comments) or A-94-56 (for part 58 comments), 401 M Street,

S.W., Washington, DC 20460. The docket may be inspected between 8:00

a.m. and 5:30 p.m. on weekdays, and a reasonable fee may be charged for

copying. The Air Docket may be called at 202-260-7548.

FOR FURTHER INFORMATION CONTACT: Laura D. McKelvey, Information

Transfer and Program Integration Division (MD-12), U.S. Environmental

Protection Agency, Research Triangle Park, NC 27711, telephone (919)

541-5497, for the part 51 SIP. For parts 51 and 52 new source review

programs, contact Dan deRoeck, Information Transfer and Program

Integration Division (MD-12), U.S. Environmental Protection Agency,

Research Triangle Park, NC 27711, telephone (919) 541-5593. For part 58

ambient air quality surveillance, contact David Lutz, Emissions

Monitoring and Analysis Division (MD-14), U.S. Environmental Protection

Agency, Research Triangle Park, NC 27711, telephone (919) 541-5476.

Table of Contents

I. Background

II. Targeted Implementation Strategy

A. Background

1. Modeling

2. Ambient Monitoring

B. Implementing the Targeting Strategy

1. Ranking of Source Categories

2. Other Considerations

3. States' Targeted SO2 Monitoring Program

4. Addressing the Problem

C. Relocating Monitors

1. Resource Concerns

2. Siting Concerns

3. Trends Data Concerns

4. Barriers

5. Conclusion

D. Compliance and Enforcement Issues

1. Averaging Times for Emission Limits

2. Malfunction Policy

3. Conclusion

III. Requirements Associated with Retention of Existing NAAQS

IV. Requirements Associated with Retention of Existing NAAQS and

Implementation of a Section 303 Program

V. Requirements Associated with a New 5-Minute SO2 NAAQS

A. Targeted Implementation Strategy

B. Designations--Section 107

1. Statutory Requirements

2. Timeframe for Submittal of Designations by State

3. Determining Initial Designation of an Area

4. Determining the Boundaries of Designated Areas

5. Promulgation of Designations by EPA

6. Failing to Submit Designations

C. State Implementation Plans (SIP's)

1. General SIP Requirements--Section 110(a)

2. General SIP Requirements--Section 110(a)(2)

a. Statutory and Existing Regulatory Requirements

b. Statewide SIP's for the Revised SO2 NAAQS

c. New Source Review Issues

d. Schedule for Submittal of Section 110(a)(1) SIP's

D. Nonattainment Area Requirements

1. Attainment and SIP Submittal Dates

2. Classifications--Section 172(a)(1)

3. Nonattainment Plan Provisions--Section 172(c)

a. Statutory and Existing Regulatory Requirements

b. Reasonably Available Control Measures (Including Reasonably

Available Control Technology)

c. Emission Inventory

d. Control Strategy Demonstration

e. Reasonable Further Progress

f. Permits for New and Modified Major Stationary Sources

g. Contingency Measures

E. SIP Processing Requirements

1. SIP Completeness

2. Approval/Disapproval of Plan

3. Sanctions and Other Consequences of SIP Deficiencies

VI. Significant Harm Levels and Episode Criteria

VII. Proposed Revisions to Part 58 Monitoring Regulations

A. Section 58.1 Definitions

B. Appendix C--Ambient Air Quality Monitoring Methodology

C. Appendix D--Network Design for State and Local Air Monitoring

Stations (SLAMS) and National Air Monitoring Stations (NAMS)

D. Appendix F--Annual SLAMS Report

E. Appendix G--Air Quality Index Reporting and Daily Reporting

VIII. Transition Issues

IX. Other Clean Air Act Amendment Authorities Affecting SO2

Sources

X. Public Participation

A. Comments and the Public Docket

B. Public Hearing

XI. Administrative Requirements

A. Regulatory Impact Analysis

B. Impact on Reporting Requirements

C. Impact on Small Entities

D. Reduction of Governmental Burden

E. Environmental Justice

Appendix A--References

SUPPLEMENTARY INFORMATION:

I. Background

As required under sections 108 and 109 of the Act, EPA has

completed a thorough review of the air quality criteria and the current

SO2 NAAQS. Based on the health effects information assessed in the

air quality criteria, EPA provisionally concludes that the current 24-

hour and annual primary standards provide adequate protection against

the effects associated with those averaging periods. As discussed in

detail in the part 50/53 document (59 FR 58958), the key issue that

emerged from the review is whether additional regulatory measures are

needed to provide additional protection for asthmatic individuals that

may be exposed to high 5-minute peak SO2 concentrations.

As discussed in the part 50/53 document, the available air quality

and exposure data indicate that the likelihood that the asthmatic

population as a whole would be exposed to 5-minute peak SO2

concentrations of concern, while outdoors and at exercise, is very low

when viewed from a national perspective. The data indicate, however,

that high peak SO2 concentrations can occur around certain sources

or source types with some frequency, suggesting asthmatic individuals

that reside in the vicinity of such sources or source types will be at

greater health risk than indicated for the asthmatic population as a

whole. These assessments lead EPA to conclude that if any additional

regulatory measures are adopted to provide additional protection, they

should be implemented through a risk-based targeted strategy that

focuses on those individual sources most likely to produce high 5-

minute peak SO2 concentrations.

Based on these consideration, EPA is soliciting comment on the part

50/53 document on three regulatory alternatives: (1) Augmenting

implementation of the existing standards by focusing on those sources

or source types likely to produce high 5-minute peak SO2

concentrations; (2) establishing a new regulatory program under section

303 of the Act to supplement the protection provided by the existing

NAAQS; and (3) revising the existing NAAQS by adding a new 5-minute

standard of 0.60 ppm, 1 expected exceedance. Because the risk-based

targeted strategy is an integral part of each of the three alternatives

being proposed for comment, this notice will first present EPA's

approach for targeting sources with a high potential [[Page 12494]] for

causing or contributing to high 5-minute peak SO2 concentrations.

As discussed below and in the part 58 notice, a key element of this

strategy will be to relocate existing SO2 monitors to areas in

proximity of point sources of concern. The relocation of monitors is

necessary because the existing SO2 monitoring network is designed

to characterize urban ambient air quality associated with 3-hour, 24-

hour, and annual SO2 concentrations. These monitors are not

located to measure peak SO2 concentrations from point sources. As

a result, EPA's existing guidance on siting criteria, the spanning of

SO2 instruments, and instrument response time likely leads to

underestimates of high 5-minute peak SO2 concentrations. To

address these concerns, EPA is proposing revisions to the ambient air

quality surveillance requirements (40 CFR part 58) and proposed certain

technical changes to the requirements for Ambient Air Monitoring

Reference and Equivalent Methods (40 CFR part 53) in the part 50/53

document.

In addition to outlining the targeted implementation strategy, this

notice presents EPA's proposed program for implementing the section 303

program and the 5-minute SO2 NAAQS alternative. Regardless of the

alternative selected (i.e., retain the existing standards but augment

their implementation, establish a new 303 program, or add a new 5-

minute NAAQS), the targeted implementation strategy would be used to

identify areas that may be subject to high 5-minute SO2

concentrations. The measures that sources must take if they cause or

contribute to such high peaks and the actions that the States must take

will vary depending on the proposed alternative, if any, selected.

The following discussion gives statutory background information on

the regulatory approach used in addressing air pollution. Under

sections 108 and 109 of the Act, EPA is responsible for issuing air

quality criteria and for proposing and promulgating NAAQS. Under

section 110(a)(1) and part D of title I, the States then have primary

responsibility for implementing the NAAQS. In broad outline, each State

must develop and submit to EPA a plan that provides for attainment of

each NAAQS within certain time limits. The EPA must review the SIP

submittal and approve or disapprove its provisions. If States fail to

submit required SIP's or submit inadequate SIP's, and the deficiencies

are not cured within specified time periods, the States become subject

to certain sanctions under section 179, and EPA ultimately becomes

subject to an obligation to promulgate a Federal implementation plan

(FIP). For a more complete discussion of the provisions of title I of

the Act, see the General Preamble for the Implementation of Title I of

the Clean Air Act Amendments of 1990 published in the Federal Register

on April 16, 1992 (57 FR 13498).

The 1990 Amendments preserved the existing framework of the SIP

process, i.e., States are still responsible for preparing and

submitting SIP's, and EPA is still responsible for reviewing and

approving or disapproving SIP's. In addition, the 1990 Amendments,

among other things, provide EPA with the unilateral authority to

designate areas as either attainment, nonattainment or unclassifiable

with respect to any NAAQS (see generally, section 107(d)(1)). States

with areas designated nonattainment for a NAAQS are required to submit

SIP's which provide for attainment of that NAAQS. States can face

sanctions and other repercussions if they fail to meet the various SIP

requirements of title I.

In general, for each of the proposed regulatory alternatives, the

Act may or may not require specific actions on the part of EPA or the

States. If the existing NAAQS is retained, then the Act imposes no new

SIP requirements on EPA and the States, although EPA will use its

discretionary authority to effectuate the Act's protective purposes by

requiring States to implement targeted monitoring around sources

capable of producing short-term high concentrations of SO2 to the

extent that those sources contribute to ambient concentrations of

SO2. If the existing NAAQS is retained along with a trigger level

for implementing an emergency program under section 303, then the State

would be principally responsible for developing and implementing the

necessary prevention and/or abatement strategies. If a new 5-minute

NAAQS is established, States would have to develop and submit SIP's

which provide for implementation, maintenance and enforcement of the

new NAAQS.

Further discussion of the requirements that are to be met by the

States is provided below with regard to each of the additional

regulatory alternatives to be considered by EPA.

II. Targeted Implementation Strategy

This section principally proposes EPA's strategy to identify those

areas where the potential exists for exceedances of the current

SO2 NAAQS as well as the potential for high 5-minute

concentrations of SO2. This strategy has two stages. The first

stage is to identify potential problem areas and then to conduct

ambient monitoring at those areas. The second stage is to take

corrective action should monitoring conducted during the first stage

reveal concentrations in excess of the appropriate SO2 NAAQS or

trigger level. To begin this strategy, EPA intends to refocus Agency

monitoring resources into those areas with potential 5-minute SO2

peaks. The development and implementation of this strategy relies on

the ability of the States to identify the specific emission and

operating characteristics of sources which can contribute to violations

of the existing NAAQS as well as contribute to high 5-minute SO2

concentrations. Successful implementation of this strategy will result

in either the identification of additional SO2 problem areas or

the conclusion that the ambient SO2 problem is largely solved. It

also allows EPA to apply finite resources in an efficient way where

public health is most likely to be jeopardized by air pollution. The

EPA intends to pursue this targeted strategy regardless of the outcome

of the NAAQS proposal published in the part 50/53 notice and solicits

comments on the targeted implementation strategy.

A. Background

1. Modeling

For implementing the current SO2 program, EPA has historically

relied on mathematical dispersion models for predicting air pollutant

concentrations for the following needs: (1) For redesignating areas to

nonattainment or attainment under section 107 of the Act; (2) for

setting emission limits for an attainment strategy as required per 14

section 110(a)(2)(K) and part 40 of the Code of Federal Regulations,

Sec. 51.115 (40 CFR 51.115); (3) for predicting locations of maximum

concentrations for siting monitors; (4) for determining boundaries of

nonattainment areas; (5) for predicting consumption of ambient air

increments under prevention of significant deterioration (PSD); and (6)

for determining, under nonattainment NSR, if the significance level,

used for determining if a major source or modification is considered to

cause or contribute to a violation of the NAAQS, is exceeded.

The ``Guideline on Air Quality Models (Revised),'' EPA-450/2-78-

027R, hereinafter referred to as ``the Modeling Guideline,'' has

provided a common basis for conducting such modeling. The Modeling

Guideline was incorporated into 40 CFR part 51 on July 20, 1993 (58 FR

38816) as appendix W. However, modeling is not currently feasible for

predicting 5-minute ambient [[Page 12495]] air concentrations of

SO2. This is due to present uncertainties regarding the ability of

models to reliably predict SO2 concentrations for 5-minute periods

and uncertainties with the accuracy of the input data needed to run the

models. A brief summary of issues follows.

Validation. Although models are available, they have not been

applied in predicting 5-minute SO2 concentrations. Model

validation studies have not been conducted to determine whether

existing models can estimate with sufficient accuracy to be used in a

regulatory context. Model validation studies are therefore necessary to

determine the precision needed for input data for achieving the desired

prediction accuracy. This would help determine, for example, whether

on-site 5-minute meteorological data are needed or if nearby National

Weather Service data are sufficient.

Emissions Data. In addition to the unassessed uncertainties of

models, the accuracy and availability of input data, such as emissions,

meteorology, and the occurrence of a short-term release (e.g., a

process upset or control equipment malfunction) necessary to run the

models, limits the ability to accurately predict 5-minute SO2

concentrations at this time. Obtaining accurate source emission data

for 5-minute periods is of critical importance. However, it is

difficult to obtain such data since such data often depend on trying to

measure emissions that may occur infrequently and at unpredictable

times, concentrations, and flow rates (estimates of both flow rates and

pollutant concentrations are necessary to determine mass emissions

unless a mass balance can be performed, which would be difficult on a

5-minute basis). Moreover, emergency bypass valves, where measurements

of emissions might be most appropriate under some circumstances, are

infrequently used and therefore are not appropriate sites for the

installation of monitors for continuous measurement of flow rates or

pollutant concentrations.

Predicting Short-term Events. Current models used for predicting

ambient air concentrations rely on a known emission release, usually

some steady-state emission rate, and known past meteorological data.

Short-term models use hourly weather data from the National Weather

Service or from on-site meteorological stations, which are preprocessed

before being used in the model. Long-term models use joint frequency

distribution summaries of wind speed, direction and atmospheric

stability category. In order to model for emission releases due to

malfunctions, a method of determining the expected frequency of these

malfunctions would have to be employed (e.g., a Monte Carlo simulation

which is a computer simulation using random sampling techniques to

obtain approximate solutions to mathematical or physical problems

especially in terms of a range of values each of which has a calculated

probability of being the solution). To date, EPA has never attempted to

integrate dispersion modeling with malfunction frequency data to set

emission limits, or to perform any other regulatory modeling tasks.

Indeed, EPA's longstanding position has been to regard malfunctions as

violations of applicable control requirements, subject to enforcement,

unless it can be shown that such malfunctions are truly unavoidable

(Bennett, 1982). To allow deviations from this policy, EPA would need

to develop a method along with policy and guidance for its use, which

EPA does not intend to do at this time.

Meteorological Data. On-site meteorological data are preferable,

but National Weather Service data may be acceptable if a station is

nearby and deemed representative of the area modeled. The

meteorological data requirements for 5-minute SO2 modeling could

be determined through model evaluation studies, as discussed earlier in

this section.

For these reasons, in contrast with longer averaging periods,

models cannot currently be used to predict 5-minute SO2 excursions

needed to support a 5-minute NAAQS. However, despite these limitations,

current models may still be used as a tool in a qualitative sense in

the decision-making process for determining boundaries of nonattainment

areas and for siting of monitors in areas of maximum concentrations.

Consequently, the targeted implementation strategy which is designed to

find areas exposed to high, 5-minute concentrations of SO2 will

rely principally on ambient air monitoring instead of modeling.

2. Ambient Monitoring

Requirements for monitoring are established at 40 CFR Part 58--

Ambient Air Quality Surveillance. This part: (1) Contains criteria and

requirements for ambient air quality monitoring and requirements for

reporting ambient air quality data and information; (2) contains

requirements pertaining to provisions for an air quality surveillance

system in the SIP; (3) acts to establish a national ambient air quality

monitoring network for the purpose of providing timely air quality data

upon which to base national assessments and policy decisions; and (4)

includes requirements for the daily reporting of an index of ambient

air quality to ensure that the population of major urban areas are

informed daily of local air quality conditions.

In the early 1970's when EPA and the States first began to monitor

for SO2 in the ambient air, SO2 emissions were greater and

more widespread than today. Combustion of sulfur-bearing fuels occurred

not only in industrial and utility settings but in private settings as

well. Fuel oil and coal were burned in residences and building boilers

for warmth. For this reason and because of the potential for exposures

of the population, large metropolitan areas were generally selected for

monitoring. Sulfur oxide emissions have decreased about 27 percent

since 1970 (EPA, 1992b). Today most residences and buildings use

electricity or natural gas for heating and nearby industrial or utility

sources have installed control devices or have switched to lower sulfur

fuel resulting in less sulfur emissions in the vicinity of the ambient

air monitors. Because of these reductions in SO2 emissions in

populated areas, only a small number of monitors are now recording

exceedances. Even these few exceedances are due not to area sources of

SO2 but instead to emissions from nearby industrial sources.

Despite these changes in the profile of sources of SO2 emissions,

the SO2 ambient air monitoring network has not been modified to

reflect the ambient air quality for SO2 near industrial sources.

As a result of past emphasis on urban scale air quality management,

SO2 monitoring networks are designed to measure population

exposure over a large area and are not generally designed to measure

the influence of specific point sources. To an increasing extent,

therefore, SO2 nonattainment areas have been identified by air

quality dispersion models and defined by one or a few point sources

with probability of causing a violation of the SO2 NAAQS when

operating at allowable emission limits at times of unfavorable

meteorology. Increased concerns about high short-term concentrations of

SO2 occurring near point sources, together with the prevalence of

low concentrations at existing networks and the inability of models to

predict short-term concentrations, suggest a need to redirect monitor

networks near these sources.

As already briefly discussed, there are about 675 SO2 SLAMS

monitors across the Nation. In this notice, EPA is proposing changes to

40 CFR part 58 to allow for fewer SLAMS monitors per metropolitan

statistical area. This will enable monitors and resources to be

redirected towards placing monitors [[Page 12496]] near point sources.

There is a higher initial cost associated with finding and setting up

new monitoring sites than the annual operating cost of the monitor

itself. Because of this and because of limited State monitoring

resources, not all monitors initially freed up can be immediately

placed around a targeted source, but will be phased in over a period of

time.

For the reasons stated above, EPA proposes to direct States to

redeploy SO2 monitors around targeted sources of SO2 and

respan the instrumentation at selected sites to measure values above

0.5 parts per million (ppm). The monitors will be sited at microscale,

middle, or neighborhood distance from the targeted sources in order to

best measure high, 5-minute concentrations of SO2. Micro, middle,

neighborhood, and urban scales are all more completely defined in 40

CFR part 58, appendix D. The EPA and States will first monitor around

those sources in areas with population with the greatest potential to

exposure to 5-minute, peak SO2 levels. The EPA and States will

consider discontinuing the operation of existing monitors and relocate

them for the purpose of monitoring around targeted sources (see part 58

discussion published elsewhere in this notice for monitoring

requirements).

B. Implementing the Targeting Strategy

As discussed earlier, the available air quality and exposure

information indicates that a large degree of protection against

exposure to short-term peak SO2 concentrations is provided by the

current NAAQS. Full implementation of the Acid Rain Program will result

in further reduction of SO2 emissions and the likelihood of peak

SO2 concentrations. The available data indicate, however, that

peak concentrations of SO2 can still occur around certain sources

or source types with some frequency, suggesting asthmatic individuals

who reside in the vicinity of such sources or source types will be at

greater health risk than indicated for the asthmatic population as a

whole. These assessments have led EPA to conclude that any regulatory

measures adopted to provide additional protection should be implemented

through a risk-based targeted strategy that focuses on those individual

sources more likely to produce high 5-minute peaks.

Therefore, in order to gather more information, to focus

implementation efforts on those sources that EPA's existing data

suggest may pose the greatest health risk, and to allocate monitoring

resources as efficiently as possible, EPA has developed an approach to

guide States in developing a prioritized list of sources to be targeted

for monitoring. As further discussed below, potential sources have been

placed in one of three groups based on the overall likelihood of the

source category to emit high 5-minute SO2 peaks. However, before

redeploying monitors, States must evaluate each of these facilities

individually, basing their decision on more specific information such

as size, configuration, compliance history and proximity to population

centers.

As just described, States need to review their current SO2

monitoring networks to determine which monitor sites should continue

operating and which should be discontinued and relocated around

potential sources. The EPA will work with each State to develop a

targeted SO2 monitoring plan to implement the strategy, based on

the number of targeted sources, SO2 monitoring resources, and

within a reasonable time horizon.

The EPA believes that new locations for siting monitors should be

in the vicinity of sources suspected of causing short-term SO2

peaks. Some examples of sources which emit SO2 are petroleum

refineries, sulfuric acid plants, fossil fuel-fired industrial boilers,

utility boilers, pulp and paper mills, iron and steel mills, wet corn

milling operations, nonferrous smelters, carbon black manufacturing,

portland cement manufacturing, phosphatic fertilizer production, and

natural gas production. This list is not exhaustive and could

potentially include other process sources with known emissions of

SO2. These sources have the ability to emit relatively large

quantities of SO2 over short durations. Such large quantities of

emissions may be due to releases from batch type operations,

operational malfunctions or upsets requiring control equipment

bypasses, control equipment malfunctions that can result in

uncontrolled emissions to the atmosphere, startup/shutdown, short

stacks subject to downwash, or fugitive emissions.

1. Ranking of Source Categories

The information most heavily relied on in developing this ranking

of source categories was: (1) Available 5-minute air quality data

documenting the number of high, short-term concentrations observed in

the vicinity of various sources by monitoring networks (Table 3-1, EPA,

1994b); (2) estimates of exposures from various source types, which

integrated a source's likelihood to emit short-term SO2 peaks with

the size and activity of the surrounding population, as summarized in

Table 3-5, Table B-1, and Table B-2 (EPA, 1994b), as well as

accompanying documentation (Rosenbaum et al., 1992; Stoeckenius et al.,

1990; Burton et al., 1987); and (3) the Geographic Targeting Data Base

for nonutility sources that is derived from combining a census of

manufacturing, the EPA Facilities Index System, and the EPA Aerometric

Information Retrieval System (AIRS) into a projected source impact data

set. This data base, which will be available through AIRS, is a data

set of nonutility sources sorted on the projected annual process

emissions per source and per size category.

In order to further refine the ranking of source categories, both

within and between groups, EPA solicits technical information

concerning several issues which include: (1) The likelihood of source

categories to produce short-term SO2 peaks; (2) the

characteristics, within a source category which cause a subset of

facilities to be more likely to produce short-term SO2 peaks; and

(3) the factors which are likely to drive the variability in SO2

emissions of individual facilities within a source category.

The ranking described here separates source categories into three

groups: A, B, and C. In pursuit of this targeting strategy, EPA intends

to require States to evaluate groups A, B, and C sources and produce a

refined monitoring plan. States are free to substitute, e.g., group B

sources for group A sources in their priority schemes, but should

provide a reasoned justification for finding that the risks posed by

these sources justifies such substitution. Ultimately, EPA anticipates

that sources in all three groups will be assessed for their exposure

potential and appropriate actions taken to address them. The EPA

believes that there is a higher probability of finding individual

sources that produce high, short-term ambient concentrations of

SO2 within each source category in group A than in the other

groups. As such, they are judged in general to pose the highest risk of

exposing population in their vicinity to high, short-term

concentrations of SO2, as well as potentially exposing some

individuals to several peaks per year.

The source categories within group A were generally found to meet

two of the three following characteristics. Either the source category

contained SO2 sources which: (1) Have a high emission rate, (2)

are near monitors which measured 5-minute peaks, or (3) are estimated,

based on exposure analysis, to expose a high number of asthmatics

living in their vicinity at elevated ventilation rates to SO2

concentrations greater than 0.6 ppm. In addition, these source

categories are known to have [[Page 12497]] short-term releases due to

events discussed later.

Group A consists of the following source categories: Sulfite pulp

and paper mills, primary copper smelters, primary lead smelters,

aluminum smelters, and the top 20 percent of the petroleum refineries

in terms of projected annual emissions of SO2 as listed in the

Geographic Targeting Data Base.

Source categories were selected for group B because they have high

annual emissions or are subject to events leading to short-term

releases of SO2. In addition, in some instances, there were air

quality or exposure data which indicate the source category to be of

concern for emitting short-term SO2 peaks.

The EPA judged group B source categories to have the potential to

produce high 5-minute peaks of SO2 but to pose less risk than

group A because: (1) Air quality or exposure data indicated that the

potential to emit high 5-minute peaks of SO2 was less than for

group A; (2) the grouping was based on annual emission data, but lacked

5-minute data to estimate risk; or (3) the overall risk posed by the

source category was judged to be low. This was the case for industrial

boilers because, while exposure analysis indicated that this group was

responsible for a considerable number of exposures, the exposures were

attributed to a very small subset of industrial boilers. The EPA

expects that States will examine their source categories within this

group very closely for inclusion in the targeted SO2 monitoring

plan.

The group B sources are as follows: Kraft sulfate pulp and paper

mills, secondary copper smelters, secondary lead smelters, the

remaining petroleum refineries, iron and steel mills, carbon black

manufacturing, portland cement manufacturing, crude petroleum and

natural gas extraction processes, phosphatic fertilizer manufacturing,

industrial boilers, and sulfuric acid plants.

Industrial boilers were placed in this group because they accounted

for about 30 to 50 percent of the 5-minute SO2 exposure events

given in the staff paper supplement (Table 3-5, EPA, 1994b). However,

in a study by Stoeckenius et al. (Table 2-14, 1990), approximately half

of the total industrial boiler exposures were attributed to a very

small proportion (2 percent) of the total population of

industrial boilers analyzed. Good engineering judgment suggests that

the use of higher sulfur coal and short stack height would contribute

to an increased likelihood of producing ambient SO2 peaks.

The group C source category consists of utility boilers. Although

utility boilers can emit large quantities of SO2, many power

plants are not anticipated to cause 5-minute violations despite their

high emission rates due to tall stacks and steady-state operating

conditions. They are placed in group C because as a source category,

utility boilers may be responsible for approximately 17 to 37 percent

of total estimated exposures (Table 3-5, EPA, 1994b). However, the risk

of exposures is very unevenly distributed across the sources in this

category. Approximately 75 percent of the utility sector's post-title

IV exposures were estimated to result from less than 10 percent of the

power plants (Rosenbaum, 1992, Table 3, Burton et al., 1987).

With the passage of the 1990 Amendments, Congress created under

title IV an SO2 emission trading program as an integral part of

the Acid Rain Program, which is designed to reduce SO2 emissions

by 10 million tons nationwide by the year 2010. Phase I, which begins

in 1995, reduces emissions from the 110 largest emitting power plants,

which are identified in table A of section 404 of the Act. The Acid

Rain Program introduces a flexibility for sources to choose the most

cost-effective compliance strategy to achieve their emission reduction

obligations and to maintain the national cap of 8.95 million tons of

SO2 emissions. Compliance flexibility may involve switching to

low-sulfur coal, scrubbing, conservation, other emission control

technologies, or buying SO2 allowances.

Title IV sources participating in the Acid Rain Program are under

the obligation to match their annual SO2 emissions with their

allowance holdings. They are also required to meet all other

requirements of the Act and regulations that apply to them, including

the NAAQS. Therefore, the compliance flexibility offered under the Acid

Rain Program does not permit any source to violate regulations adopted

to attain or maintain the SO2 NAAQS. Emissions from these sources

will be closely tracked, because title IV sources are also required to

install continuous emissions monitoring systems (CEMS) and report to

EPA on a quarterly basis their emissions of SO2, nitrogen oxides,

and carbon dioxide.

Further improvements in air quality are expected to be realized

from the SO2 emission reductions under Phase II of the Acid Rain

Program to be implemented by January 1, 2000 under title IV of the Act.

Because of the potential to have higher emissions and because of

potential plume downwash and interaction of complex terrain, EPA is

mainly concerned with those power plants that buy allowances rather

than reduce emissions themselves in order to comply with title IV and

those located in complex terrain, respectively. Complex terrain is

defined for modeling applications as that terrain exceeding the height

of the stack, but this definition is being applied here for monitoring

applications as well. In a study done for EPA, that is contained in the

docket for this rulemaking (Polkowsky, 1991), many of the predicted

exceedances of the SO2 standards in the vicinity of power plants

should be reduced or eliminated by allocating allowances based on a

reduced rate under Phase II. Any remaining exceedances not addressed by

the more restrictive Phase II emission rates will require a reanalysis

of the SO2 NAAQS control strategy demonstration and consideration

of more restrictive emission limits to protect the air quality

standards.

Because of the SO2 reductions that will occur under the Acid

Rain Program, the accurate stack monitoring of their emissions, and the

long-range atmospheric transport of these emissions due to taller

stacks at most large utilities, EPA believes that higher priority in

placing ambient monitors should be given to nonutility sources.

However, in instances at a particular power plant where the possibility

of high 5-minute emission peaks still exists, EPA believes that

consideration should be given by the State to locating monitors near

the facility.

2. Other Considerations

In addition to the guidelines and groupings listed above, which are

based largely on available information concerning the likelihood of a

source type to produce concentrated peaks of SO2, States may have

other information which may lead them to believe that a source located

in a lower probability group should be made a higher priority for

SO2 monitoring. Of particular importance to consider is any

available information on potential population exposure, inferred in

part by the population in the vicinity of the source.

In addition, other information can be incorporated by States into

an evaluation of the relative likelihood of sources under their

jurisdiction to produce SO2 exposures, thus refining their

judgments on priority of monitoring decisions. Such other information

can include the type of process being used (i.e., one type of process

within a source category may be less efficient and known to emit more

SO2 than a newer one), a history of past [[Page 12498]] upsets or

malfunctions, the type of fuel used, the type of terrain around the

source (e.g., is the source in a river valley or on flat terrain),

knowledge of how well the source is controlled, and a history of

citizen complaints, and should be considered by the States when

deciding which sources to monitor first. Such considerations would be

noted in each State's targeted SO2 monitoring plan presented

during the annual SLAMS review as described below.

As part of the targeting strategy, the States will also need to

decide how much relative weight should be given any particular source.

For example, a State would have to determine how heavily to weigh a

group A source in a less densely populated area versus a group C source

burning a high sulfur fuel in a more densely populated area. In

addition, some sources are often found collocated with other sources

such as sulfuric acid plants with copper smelters. Industrial boilers

may be located with any number of process sources. There may be small

geographic areas where there is clustering of an assorted number of

SO2 sources. In these situations there is no precise way to

determine what source should be targeted first at this point. For this

reason, the decision making should rest with the States who have better

knowledge of the individual circumstances pertaining to the potential

sources to be targeted.

3. States' Targeted SO2 Monitoring Program

The EPA will review and take appropriate action on the States'

targeted SO2 monitoring plans during the annual SLAMS network

review process to ensure that States provide an adequate rationale for

any deviations from the grouped approach. The States are then expected

to present to EPA in a targeted SO2 monitoring plan at the annual

SLAMS network review their listing of sources to be monitored, the

schedule for conducting such monitoring, and the rationale for

selecting these sources. Requirements for the targeted SO2

monitoring plan are discussed later in this notice for part 58 but EPA

expects the targeted SO2 monitoring plan to be a dynamic process

that could change depending on data gathered from early rounds of

monitoring or changes at targeted sources, such as installation of

control equipment.

Section 110(a)(2)(B) of the Act requires SIP's which provide for

the establishment and operation of appropriate devices, methods,

systems, and procedures necessary to monitor, compile and analyze data

on ambient air quality. Should EPA determine that a State's targeted

SO2 monitoring plan is inadequate, then EPA expects to issue a

call for a SIP revision under section 110(k)(5) of the Act based on a

finding that the SIP is substantially inadequate in meeting the

requirement of section 110(a)(2)(B). The EPA solicits comments on all

aspects of this approach to grouping of sources to investigate

potential air quality problems.

In the State targeted SO2 monitoring plan, EPA expects

SO2 monitoring network reviews to be completed within 1 year of

the effective date of promulgation of any of the three regulatory

alternatives. Implementation of network revisions is expected to take

longer.

4. Addressing the Problem

Regardless of the regulatory alternative chosen by the

Administrator, those areas which have monitored exceedances of the

existing or revised NAAQS or of a section 303 trigger level should

undergo a compliance inspection by the State of the targeted source. If

the source is out of compliance, EPA expects that the responsible air

pollution control agency will initiate appropriate enforcement action

to bring it into compliance, e.g., by using available administrative or

judicial enforcement authorities. If the source is in compliance, the

State will need to pursue other appropriate solutions to the problem as

discussed later in section III.

The EPA encourages States to pursue, where appropriate, the

enforcement and improved compliance options before other regulatory

actions. In many cases, air quality problems may be due to poor

operation and maintenance or other resolvable compliance problems. In

these instances, enforcement action can result in timely resolution of

violations and avoid the sometimes lengthy regulation development

process. However, the State should pursue existing regulatory options

where the regulations are inadequate, e.g., because the source is in

compliance with the existing regulations and an air quality problem

still exists.

C. Relocating Monitors

The EPA's criteria for the network design of monitors are discussed

in 40 CFR part 58, appendix D. Elsewhere in this notice, EPA is

proposing changes to part 58 in order to implement the proposed

targeting program. The EPA recognizes that it is not a trivial matter

to relocate monitors and that there are concerns that agencies will

need to consider in making relocation decisions.

1. Resource Concerns

The EPA believes that the resources currently devoted to monitoring

ambient concentrations of SO2 may be more effectively utilized

through systematic evaluations and reconfigurations of existing

monitoring networks. However, even if States and locals acquire no

additional SO2 monitors and rely solely on the current number of

monitors, there will be some costs incurred when relocating monitors.

Costs associated with moving a monitor include the resources taken in

locating new sites and negotiating leases along with the capital costs

of a new shelter and associated equipment. Because of the costs for

relocating monitors, not all monitors freed up can be immediately

placed around a targeted source, but will be phased in over a period of

time. The operating costs saved by not operating these monitors will be

used toward the costs of relocating monitors.

In more detail, the costs for moving an SO2 monitor have been

calculated in 1994 dollars to be $60,940 per site. These costs include

initial capital costs, operation, and amortization. The initial costs

include network design and site selection, land lease, power drop,

shelter, site preparation, calibration equipment, data logger, quality

assurance plan preparation, etc. The operation costs include routine

site visits, repairs, maintenance, data acquisition and reporting,

quality assurance calibrations, and supervision. The amortization costs

for replacement capital equipment were also calculated.

The total costs for the initial 3 years are summarized as follows.

The existing network of 679 NAMS, SLAMS, and industrial monitors costs

about $16 million per year. The first year costs for reconfiguration

and operation of NAMS, SLAMS, and industrial monitors in order to

comply with changes to 40 CFR part 58, which is being proposed in this

notice and is not a result of the targeted implementation strategy, is

estimated to be $12.4 million per year. This will leave an available

$3.6 million to be used toward the targeted implementation strategy the

first year to establish and operate four monitors around 15 sources.

The second year costs for operating the NAMS, SLAMS, industrial,

and targeted implementation strategy monitors is estimated to be $9.6

million dollars, making available $6.4 million for the targeted

implementation strategy. This will allow for establishing sites around

26 sources in addition to the 15 sources from the first year for a

total of 41 targeted sources. [[Page 12499]]

The third year costs for operating monitors are estimated to be

$11.4 million, leaving $4.6 million for the targeted implementation

strategy. This will allow for establishing sites around 16 sources in

addition to the 41 sources established in the first and second years

for a total of 57 targeted sources. The EPA estimates that monitors at

7 of the 15 sources established in the first year would be moved in the

third year due to no monitored violations.

2. Siting Concerns

The EPA is aware of the many considerations that arise when siting

monitoring stations. Monitors are usually sited where electrical power

is already available, they are reasonably secure, the immediate

environment satisfies the siting criteria of part 58, and they are in

proximity to the desired locations. Waiver provisions are also included

in the regulations to deviate from siting criteria when appropriate.

Generally, monitors are sited at or within reasonable proximity of the

desired locations. For purposes of convenience, monitors are sometimes

sited where other pollutants are already monitored.

When conducting the SO2 network review, EPA-approved air

quality models and saturation studies may be used to predict locations

where maximum concentrations are expected within the vicinity of

SO2 sources or clusters of sources. As discussed earlier, models

can be used in a qualitative sense to predict relative ambient impacts

and are useful as a tool for establishing preferred monitor locations

for predicting 5-minute concentrations.

3. Trends Data Concerns

A potential concern regarding the movement of monitors is the

effect on EPA's ability to detect and evaluate trends in air quality.

When monitors are operated in the same locations for several years, it

is possible to account for the effects of meteorology, seasonal

patterns in air pollutant concentrations and other variables specific

to a monitor location. When monitors are moved, the confidence in

detecting trends in air pollutant concentrations is compromised due to

a new set of variables that may affect ambient concentrations at the

new location.

The EPA needs to maintain a certain number of monitors for

detecting and evaluating trends in air pollutant concentrations.

However, EPA believes that a sufficient number of monitors now used for

trends analyses are not critical to the objectives of trends reporting

and should be considered for relocation. Elsewhere in this notice, the

EPA is proposing changes to 40 CFR part 58, appendix D, in which a

minimum number of SO2 monitors in the metropolitan areas will be

retained for trends purposes.

4. Barriers

Certain institutional barriers may be encountered in some attempts

to relocate monitors. These stem from the separate political entities

responsible for implementation of air pollution control programs at the

State and local levels throughout the U.S. Where monitor sites

considered for relocation are within the boundaries of one political

entity, the problems are diminished, since the resources necessary to

maintain existing monitoring sites may be redirected to the new sites,

providing the SO2 monitor is not sharing a site with other

pollutant monitors. Sites in a network around targeted sources of

SO2 emissions which are located in different States or air

pollution control districts may present some added difficulties. In

such cases, resources, such as grants for support of air pollution

planning and control programs as allowed under section 105 of the Act,

may be redirected by EPA to aid in relocating and maintaining new

monitoring stations.

5. Conclusion

In general, EPA believes that a portion of the monitors now

directed to monitoring ambient air quality in population areas for

trends purposes should be considered for relocation. While EPA may not

normally require monitors operated by industries to be relocated and

thus industry-operated monitors will not be candidates for relocation,

EPA strongly encourages companies to evaluate their networks in light

of today's notice. However, quality-assured data from such monitors

could allow for the relocation of nearby SLAMS monitors to other

locations if monitored air quality concentrations from industry-

operated monitors provide assurances that the SO2 NAAQS are

maintained.

D. Compliance and Enforcement Issues

Certain compliance and enforcement issues will arise only if either

the section 303 alternative or the new 5-minute NAAQS alternative is

selected. The issues are how to determine compliance to ensure

protection of a trigger level or NAAQS that has a 5-minute averaging

period, and what actions are appropriate by the State when the cause of

the violation may be process upsets, startup or shutdown, batch

operations, or other nonsteady-state sources. As is currently done with

the NAAQS, measurement of SO2 ambient air concentrations with

ambient air monitors under each of the three proposed regulatory

alternatives will serve as indicators of compliance. Enforcement will

be based on the results of compliance inspections at the source, and

the compliance inspection will be based on requirements in the

applicable operating permit or SIP. In most instances, EPA believes

that in order to ensure protection of the 5-minute NAAQS or trigger

level, compliance will need to be determined through sources meeting

recordkeeping and reporting requirements or carrying out any other

agreed-upon actions designed to reduce short-term emission peaks.

1. Averaging Times for Emission Limits

Under EPA's policy for emissions averaging under the current

SO2 NAAQS, sources are to be controlled through the imposition of

emission limits having averaging times consistent with the averaging

period of the air quality standard of concern. As an example, in order

to protect the SO2 ambient air quality standard that has been

established for a 24-hour period, mass emission limits for sources

should normally allow averaging of emissions over no more than a 24-

hour period when determining compliance with the limits. The purpose of

this is to restrict extreme variations in emissions of short duration

that might otherwise be allowed to occur if emission variations are

averaged over much longer periods (e.g., 30 days). Air quality

concentrations in excess of the standard could be produced while

sources are still complying with long-term average emission limits by

reducing emissions sufficiently at other times within their emission

averaging periods.

A variety of emission limit averaging times had been developed by

State and local agencies for SIP's both prior and subsequent to the

implementation of this policy on averaging. As a result, those SIP's

with averaging times inconsistent with the policy that were adopted

prior to implementation of the policy are included in an effort by EPA

to correct general SIP enforcement deficiencies. The EPA has not taken

final action on those rules developed subsequent to the policy.

The EPA has allowed the use of stack tests and analysis of fuel

samples for sulfur content as surrogates for continuous compliance

monitoring with the emission limits. In many cases, these methods will

continue to be feasible for ensuring compliance with a 5-minute trigger

level or NAAQS. Technically, SO2 emissions can be measured in a

stack at intervals less [[Page 12500]] than 5 minutes using Method 6c

(the instrumental analyzer procedure) in Appendix A of 40 CFR part 60

or by using a CEM. However, EPA believes that in many instances 5-

minute releases of SO2 that would cause exceedances of a 5-minute

NAAQS or trigger level will occur at unpredictable times or as fugitive

emissions (i.e., not through a stack), making stack tests an

impractical compliance method. Nor may sampling fuel at 5-minute

intervals be a practicable alternative as in the case of coal in which

sulfur content may not be homogeneous. In addition, the source of the

emission may not be due to combustion of fossil fuel but to chemical

process emissions.

The EPA believes that in most instances, in order to attain a 5-

minute NAAQS or trigger level, the State will not be able to rely on

measurable emission limits but instead on actions by the source to, for

example, modify equipment or process or to have improved maintenance

that will address the emission releases that are causing 5-minute

exceedances. Because of these potential limitations to determining

compliance of emission limits designed to protect a 5-minute NAAQS or

trigger level, compliance will in most instances need to consist of the

State ensuring that the source has implemented the necessary remedies.

Verification that actions have been effective will require that ambient

air monitoring continue for a reasonable period, e.g., another 2 years

following the corrective action. However, in those instances where

emissions can be feasibly measured on a 5-minute basis or it is

determined that fuel sampling is a feasible compliance indicator, the

State may elect to set an emission limit and use emission measurement

or fuel sampling as the method for determining compliance.

2. Malfunction Policy

As stated previously, EPA has on occasions used its enforcement

discretion in determining how and whether to act on unavoidable

violations of source emission limits during periods of startup,

shutdown and malfunction (40 CFR 60.11(d)). This policy recognizes that

during startup and shutdown conditions, effective pollutant control may

sometimes not be technically feasible due to process temperatures and

pressures that have not yet stabilized. The policy also recognizes that

certain source malfunctions are not reasonably foreseeable and are

unavoidable, which result in uncontrolled emissions to the atmosphere.

Clearly, in many cases, forces of nature such as floods, tornadoes and

lightning strikes can overwhelm a source's ability to function in a

normal fashion and may produce conditions that preclude proper

operation of sources or control equipment. However, some conditions may

be reasonably anticipated and proper design of equipment can ameliorate

their effects (e.g., grounding of equipment for lightning protection,

observation of flood plains, etc). It is possible in some cases to

address this through design of redundant control systems to guard

against the release of uncontrolled emissions to the atmosphere should

one system suffer a malfunction; however, the cost may be prohibitive

and such systems are not uniformly required. Some SO2 control

systems offer this protection, such as dual acid plants operated in

parallel at petroleum refineries. Should one plant experience

operational problems in such cases, the other is available to provide a

continued partial level of sulfur (and ultimately SO2) removal.

3. Conclusion

As is currently done, where there have been monitored violations of

the 24-hour, 3-hour, or 5-minute SO2 NAAQS or trigger level, the

State shall be required to determine the source of the SO2

emissions and investigate the cause of the emissions at that source.

Where the results of these investigations demonstrate that improper

operation and maintenance practices and/or poor control equipment

design are primarily responsible for release of uncontrolled emissions

to the atmosphere, the State shall be expected to work with the source

to take appropriate actions to reduce inadequately controlled source

emissions.

For purposes of verifying the results of any corrective actions

taken and compliance, the EPA intends to rely on continued ambient air

monitoring. The EPA also anticipates the need to review the

implementation of its malfunctions policy in light of the concerns

discussed in this document with the possible result of more stringent

showings required to justify the conclusion that malfunctions are truly

unavoidable. Recordkeeping based on earlier baseline assessments of the

problem at the source should be maintained at the source to assist in

evaluations should further exceedances be monitored.

III. Requirements Associated With Retention of Existing NAAQS

The State is not required to revise its SIP to address 5-minute,

high concentrations of SO2 if the existing NAAQS is retained.

However, in concert with changes in monitoring requirements for part 58

proposed in this document, as discussed above, EPA is proposing to

require States to implement a targeting strategy to more aggressively

monitor process sources that are likely producing high concentrations

of SO2 even if for short periods of time. As described previously,

the targeted strategy will be implemented through the annual SLAMS

network review during which the States will report on progress made the

previous year. The EPA believes that the results of such a targeting

strategy will reduce the possibility and frequency of 5-minute high-

concentration SO2 exposures as an incident to more effectively

monitoring peak SO2 concentrations and by bringing into compliance

those sources violating the existing NAAQS. However, EPA acknowledges

that there may be occurrences of SO2 releases which could exceed

the 5-minute NAAQS or section 303 trigger level proposed in the part

50/53 document and not exceed the current SO2 NAAQS. In those

cases, the State should, nevertheless, conduct compliance inspections

in the eventuality that the source is out of compliance with current

SIP requirements. Beyond these measures, EPA would not have authority

to take further actions under the title I SIP program.

If violations of the current NAAQS cannot be resolved through

compliance and enforcement (i.e., the source is in compliance), then

the State will be expected to take steps to reduce emissions on its own

initiative by revising the emission limit, by requiring process

modifications, or other control measures. The State shall then prepare

a SIP revision for EPA approval in order to make the emission

reductions federally enforceable. In the event that a State does not

take these steps, then EPA can take either of two actions: (1) If the

area is currently designated attainment, using the authority under

section 107(d) to redesignate the area nonattainment; and/or (2)

issuing a SIP call under section 110(k)(5) of the Act to notify the

Governor of the State that the SIP is inadequate to attain and maintain

the SO2 NAAQS and to call for a SIP revision as necessary to

correct such inadequacies.

There are advantages and disadvantages in using either the

nonattainment redesignation or SIP call approach. For instance, the

nonattainment redesignation process, in addition to requiring

expeditious attainment of the standard, imposes the requirements

applicable under part D, title I, of the Act (e.g., reasonably

available control measures (RACM), reasonable further progress (RFP),

[[Page 12501]] nonattainment NSR, and contingency measures), and

requires sanctions and FIP's if the SIP is not developed and

implemented in a timely manner.

While these part D requirements may well be useful in effectively

addressing the air quality problem, plan development may proceed more

quickly in response to a SIP call in some cases because the SIP call

does not entail the process and time needed to undertake a

redesignation of an area (including the notification of the Governor

required under section 107(d)(3)). The SIP submitted in response to a

SIP call under section 110 must also provide for expeditious attainment

of the NAAQS. A disadvantage of relying on SIP calls for attainment

areas is that, unless an area is otherwise subject to section 173

permit requirements, no mandatory sanctions are applicable in the event

the State fails to respond adequately to the SIP call. The

discretionary air grant funding sanction under section 179 remains

available for attainment areas, however. The requirement for EPA to

promulgate a Federal plan if the State fails to submit an approvable

SIP is wholly applicable for either option.

In addition to the advantages and disadvantages just described,

decisions about which regulatory approach to use should consider

factors specific to the affected area. Among the factors EPA will

consider are the following:

(1) The magnitude of the violation.

(2) The persistence of violations.

(3) The exposure potential. (For example, is it near a population

center or a school?)

(4) The State's regulatory process. (For example, is it lengthy;

does the legislature only meet periodically? Would the timeline of one

option fit better within the State's regulatory frame work?)

(5) Other sources in the area. (For example, can culpability be

clearly determined? Would one process facilitate that determination of

culpability over the other? Is new source growth anticipated?)

(6) The need for a more objective level of control.

(7) The type of information available for indicating a problem

exists (monitoring, modeling, others).

(8) If there is uncertainty associated with modeling and/or past

history of failing to attain the standard, does the action taken

provide for appropriate contingencies that can be implemented if the

area fails to provide a SIP or to attain and maintain the standards?

(9) Is there a need for long-range planning for the area and does

the approach taken facilitate this planning effort?

IV. Requirements Associated With Retention of Existing NAAQS and

Implementation of a Section 303 Program

In attempting to address health concerns with population exposure

to high concentrations of SO2 for short periods of time, one of

the alternatives that EPA considered in the part 50/53 notice is to

reaffirm the existing SO2 NAAQS and at the same time to promulgate

a trigger level for implementation of a program under section 303 of

the Act. The basic rationale and legal authority for that program are

discussed in that document. What follows in more detail is the proposed

implementation program, including the proposed regulatory text. The EPA

believes that a targeted implementation strategy, as already discussed,

could be used to find sources that would be subject to further

emissions or operational control under a section 303 program. The EPA

believes that a program to protect the public from exposure to high

concentrations of SO2 for short periods of time may be

successfully implemented under section 303. The type of program EPA is

proposing to implement would require States to submit contingency plans

to EPA that would require certain actions on behalf of the State and

source once an established ambient SO2 concentration (``trigger

level'') is violated. The State would be required to take certain

actions to determine the source of the emissions and to protect against

future violations of the trigger level.

As described in the part 50/53 notice concerning the regulatory

alternative of the section 303 program, EPA believes that sections 303,

110(a)(2)(G), and 301 provide adequate legal authority to establish

this program and to promulgate regulations to implement it. As with the

existing section 303 program, EPA's proposed regulations require States

to adopt contingency plans under section 110(a)(2)(G) to carry out the

program. The EPA is proposing to require that each State submit such

plans to EPA within 18 months of the promulgation of final regulations

establishing a section 303 program. The EPA believes that section

110(a)(2)(G) authorizes EPA to require these submissions and that 18

months is an adequate period of time to develop and submit the programs

to EPA for approval.

Once the section 303 trigger level has been violated, EPA proposes

that the following actions occur. First, within 30 days of a violation

of the trigger level, the State would carry out a compliance inspection

of the culpable source. The EPA recommends that the State not wait for

a violation but conduct a compliance inspection after the first

exceedance. If the source is out of compliance with its existing

emission limits, then the State would take the necessary steps to bring

the source into compliance within 30 days of the compliance inspection.

If, however, the State determines that bringing the source into

compliance with its existing emission limits would not be likely to

prevent further exceedances of the trigger level, or the State

determines the source to be in compliance with applicable emission

limits, then further action would be needed. In such circumstances, the

next step would be for the State and source to examine the cause of the

emissions. Once that is determined, enforceable actions would need to

be developed to address the cause of the pollution. These actions must

eventually be made federally enforceable by adopting them as source-

specific SIP revisions. The EPA proposes to require that actions be

taken within 60 days of the compliance inspection and provide for

implementation of any new control measures as expeditiously as

practicable. The EPA expects that the control measures that may need to

be implemented to prevent recurrences of 5-minute SO2 peaks may

include better maintenance of control equipment, better capture of

fugitive emissions, raising the stack height, or other innovative

control measures.

The EPA believes that the actions required of States and sources

would provide adequate protection against the recurrence of high, 5-

minute SO2 peaks once such emissions are identified as a problem

for particular sources. The EPA also believes that the time periods for

taking action that it is proposing are reasonable periods, as they

provide sufficient time for the required actions to take place, while

assuring that any necessary corrective actions will be taken and

implemented as expeditiously as practicable.

The EPA would also retain the ability to take whatever actions it

believed appropriate directly under section 303. Thus, EPA could take

direct action under section 303 prior to the adoption of State

contingency plans if needed, or take action after their adoption if

circumstances warranted such Federal action. Moreover, once the section

303 contingency plans have been adopted and incorporated into SIP's,

EPA may directly enforce their provisions pursuant to section 113 of

the Act.

However, it is EPA's position that the States are primarily

responsible for carrying out actions under this section

[[Page 12502]] 303 program. If a State does not exercise its

responsibility under section 303 once a trigger level has been

violated, EPA intends to consult with the State prior to taking action

itself.

The EPA is proposing to add an Appendix X to 40 CFR part 51 which

explains the computations necessary to determine from monitoring data

whether the 5-minute trigger level has been exceeded or violated.

Appendix X defines several terms, among them, ``5-minute hourly

maximum,'' ``exceedance,'' ``expected exceedance,'' and ``violation.''

Appendix X explains the convention used to calculate expected

exceedances, which essentially is a procedure which makes an adjustment

for missing monitoring data.

In brief, the 5-minute trigger level is not violated when the

number of expected exceedances per year is less than or equal to one.

In general, this determination is made by recording the number of 5-

minute hourly maximum exceedances at a monitoring site for each year,

making the adjustment for missing data (if required), averaging the

number of exceedances over a 2-year period, and comparing the number

calculated to the allowable number of exceedances (one). The 2-year

period reduces the likelihood of a source being penalized for a

violation that may be attributed to a one-time event. Aside from

changes in terminology to make the language appropriate for a section

303 program rather than a NAAQS, the proposed Appendix X is identical

to the Appendix I to 40 CFR part 50 for interpreting the 5-minute NAAQS

for SO2 that was proposed in the part 50/53 document. The EPA is

soliciting comments on Appendix X.

V. Requirements Associated With New 5-Minute SO2 NAAQS

The EPA proposed in the part 50/53 document a new primary 5-minute

SO2 NAAQS which would be in addition to the 24-hour and annual

primary SO2 NAAQS. Should this new 5-minute NAAQS be promulgated,

EPA intends to initiate the targeted implementation strategy previously

described to determine which areas are not meeting the new 5-minute

NAAQS. In addition, EPA and the States will need to initially meet

statutory requirements under sections 107 and 110. In general, these

requirements are that the States must submit their initial suggested

designations and statewide SIP's to EPA. Later, if areas are designated

or redesignated to nonattainment, then EPA and the States must meet the

requirements under section 172. The requirements under sections 107,

110, and 172 of the Act are discussed in detail below. The rationale

for any requirements which are discretionary, such as setting

timeframes, or which need interpretation, are also discussed. Since the

current annual, 24-hour, and 3-hour NAAQS are retained under this

option, all existing requirements, such as SIP submittal and attainment

dates, will remain in place as to the current NAAQS.

A. Targeted Implementation Strategy

Should a new 5-minute NAAQS be promulgated, EPA intends to initiate

the targeted implementation strategy previously described to determine

which areas are not meeting the revised 5-minute NAAQS. And as

described, the States should initially attempt to address any

violations through compliance inspection and, if necessary, enforcement

actions.

Because of the modeling issues discussed previously (II.A.1.), the

targeted implementation strategy relies principally on monitoring. The

use of models is not advocated at this time for establishing section

107 designations under a 5-minute SO2 NAAQS due to a lack of

evaluation results concerning model performance, or defining the

precision and bias of modeled 5-minute ambient SO2 concentrations.

However, models may still be used under a new 5-minute SO2 NAAQS

program for the following purposes:

(1) Models may be useful as a tool for developing control

strategies. When evaluating emissions from complex sources, they may

provide information on the relative contributions to ambient SO2

concentrations from various sources of emissions. Receptor modeling may

be a useful tool for developing control strategies for complex sources.

The use of tracers or ``tramp elements'' in association with these

models would be needed for SO2 emission sources to determine

source locations and relative contributions to ambient SO2

concentrations.

(2) Models can be and are recommended as a useful tool for

evaluating the design of monitoring networks for a 5-minute SO2

standard. They can provide useful information in a relative sense for

determining points of maximum impact providing the characteristics of

the emission source are not too complex or uncertain.

B. Designations--Section 107 1. Statutory Requirements

The 1990 Amendments require EPA to promulgate designations, of

areas for new or revised NAAQS. Section 107(d)(1)(A) of the Act

requires States to submit designations, and section 107(d)(1)(B)

requires EPA to promulgate designations of all areas (or portions

thereof) with respect to new or revised NAAQS as nonattainment,

attainment or unclassifiable. The specific requirements of section

107(d)(1) (A) and (B) of the Act are described below. An area which is

designated nonattainment is one that does not meet (or that contributes

to ambient air quality in a nearby area that does not meet) the NAAQS

for the pollutant. An area which is designated attainment is one which

meets the NAAQS for the pollutant. An area which is designated

unclassifiable is one that cannot be classified on the basis of

available information as meeting or not meeting the NAAQS for the

pollutant. Also, while section 107(d)(1) provides for States to submit

a list of areas designated, it authorizes EPA to modify the

designations submitted by the States. Once an area's initial

designation is promulgated, any change in the designation status is

accomplished pursuant to section 107(d)(3) of the Act.

2. Timeframe for Submittal of Designations by State

As mentioned above, section 107(d)(1)(A) of the Act requires States

to submit a list of all areas (or portions thereof) in the State

designating them as nonattainment, attainment or unclassifiable for

SO2. States must submit such list of areas (or portions thereof)

in a timeframe EPA deems reasonable but not later than 1 year after the

effective promulgation date of the new or revised NAAQS. The EPA cannot

require the States to submit the list of areas in less than 120 days,

however.

The EPA intends to require that the initial SO2 designations

be submitted not later than 1 year from the effective date of

promulgation of the revised standard in order to allow the States as

much time as possible to gather the necessary data to make the

designation determinations. The EPA believes that, in most instances,

areas will need to be initially designated unclassifiable due to lack

of adequate ambient air monitoring data and the inability to rely on

models for predicting 5-minute SO2 concentrations. By giving the

maximum time allowed under the Act, States may have enough time to

gather the data needed to make an adequate determination of an area's

designation status. Nonetheless, EPA encourages States to submit

designations sooner, wherever possible, in order to provide improved

protection of public health. [[Page 12503]]

3. Determining Initial Designation of an Area

The EPA expects, in most instances, to initially designate areas as

unclassifiable due to the lack of complete data or no data at all

reported for 5-minute averaging time increments. Most of the existing

ambient monitoring data are not reported for 5-minute averaging time

increments, and EPA believes that those that are reported in this

manner may not meet the data completeness criteria required by the

proposed SO2 NAAQS (see discussion in revisions to CFR part 50,

appendix I, published in the part 50/53 document). Revising the

SO2 NAAQS to include an additional primary standard set at 5-

minute and 0.60 ppm necessitates that most ambient monitors be

respanned to measure the higher concentration.

In anticipation of a revised NAAQS, EPA has requested that the

States respan monitors to begin measuring for higher concentrations. In

these cases, EPA and States may have data to provide as a basis for

initially designating an area as nonattainment.

The EPA understands that in some instances States may want to

request that certain areas be initially designated attainment for the

revised SO2 NAAQS. An area will not be initially designated as

attainment based solely on ambient monitoring data since no

requirements have been issued to ensure complete data. Data

completeness is a significant issue when trying to determine if an area

is attaining the NAAQS as opposed to determining if an area is not

attaining the NAAQS. However, areas with no SO2 sources as shown

by their emission inventory would be likely candidates for an early

attainment designation. Providing ambient air monitoring data does not

indicate otherwise, EPA intends to designate an area as attainment if

the State can show in its emissions inventory that the area does not

contain any potential major source of SO2 as defined in the Act.

This does not preclude the State or EPA from initially designating an

area unclassifiable, if there is reason to believe there is an SO2

source which may be causing a violation of the revised NAAQS in the

area. The EPA believes this guidance gives reasonable assurance that

the area is in attainment of the revised NAAQS. This does not prevent

EPA or the State from redesignating an area, initially designated

unclassifiable, to nonattainment at a later time should ambient air

monitoring data indicate that the area is violating the NAAQS.

4. Determining the Boundaries of Designated Areas

States should identify the boundaries of the nonattainment,

attainment and unclassifiable areas when submitting designations for

the revised SO2 NAAQS. In the absence of data or more specific

boundary information, it may be more appropriate to define SO2

nonattainment boundaries by the perimeter of the county in which the

ambient SO2 monitor(s) recording the violation is located.

Alternatively, it might be appropriate to define the nonattainment area

using monitoring or other data to determine more specifically the

geographic area that is nonattainment. In addition, if the ambient

monitor measuring violations is located near a county boundary, then

EPA recommends that the adjacent county also be designated as

nonattainment for SO2. In some situations, however, a boundary

other than the county perimeter may be appropriate. States may choose,

alternatively, to define the SO2 nonattainment boundaries by using

any one, or a combination, of the following techniques: (1) Qualitative

analysis, (2) spatial interpolation of air monitoring data, (3) air

quality simulation by dispersion modeling, or (4) saturation

monitoring. If a State defines an SO2 nonattainment boundary using

one of the methods above, EPA requires that it submit a defensible

rationale for the boundary chosen with the Governor's request to

designate the area.

Boundaries for attainment areas can be drawn along current

political boundaries if the State can show in its emissions inventory

that the area does not contain any potential major source of SO2

as defined in the Act, nor any of the sources listed in the previous

section on determining the initial designation of an area.

All areas of the State not designated attainment or nonattainment

will be designated unclassifiable. The boundaries of the unclassifiable

area will be the ``remainder of the State.''

5. Promulgation of Designations by EPA

Section 107(d)(1)(B)(i) of the Act requires that EPA promulgate the

designations submitted by States as expeditiously as practicable, but

not later than 2 years from the date of promulgation of the revised

SO2 NAAQS. This period may be extended for up to 1 year where EPA

has insufficient information to promulgate the designations. The EPA

may make any modifications deemed necessary to the areas (or portions

thereof) submitted by the State (see generally section 107(d)(1)(B) of

the Act). However, no later than 120 days before promulgating a

modified area, EPA must notify the affected State and provide an

opportunity for the State to demonstrate why any proposed modification

is inappropriate.

The EPA expects in many cases to require the full extension of 1

year before promulgating the designations of many areas as allowed

under section 107(d)(1)(B) of the Act. The full extension would be

needed in these cases in order to allow States and EPA to respan or

relocate monitors and collect complete ambient data to better ascertain

the designation status of areas with monitors. Therefore, EPA generally

intends to promulgate the initial area designations within 3 years from

the effective date of promulgation of the revised SO2 NAAQS.

Designations promulgated pursuant to section 107(d)(1) of the Act

are exempt from the Administrative Procedures Act requirements for

notice-and-comment rulemaking (5 U.S.C. section 553-557) (see section

107(d)(2)(B) of the Act). Therefore, when EPA promulgates designations

with respect to the revised SO2 NAAQS, it may or may not

promulgate the designations through notice-and-comment rulemaking.

6. Failing to Submit Designations

If the Governor of a State fails to submit the required SO2

designations, in whole or in part, EPA is required to promulgate the

designation that EPA deems appropriate for any area (or portion

thereof) not designated by the State (see section 107(d)(1)(B)(ii) of

the Act). The EPA will do so no later than 3 years after the date of

promulgation of a new NAAQS.

C. State Implementation Plans (SIP's)

Section 110(a) establishes the general requirements for SIP's. In

addition, subparts 1 and 5 of part D of title I of the Act establish

additional requirements concerning SIP's for areas designated

nonattainment for SO2. These requirements concern the content of

the SIP's, the applicable dates by which nonattainment areas must

attain a new SO2 NAAQS, and the schedule for the submission of the

SIP's.

1. General SIP Requirements--Section 110(a)

All SIP's, regardless of whether they concern areas designated

nonattainment or not, must meet the general SIP requirements of section

110(a). Section 110(a)(1) provides that each state must submit a SIP to

provide for the implementation, maintenance and enforcement of a

primary NAAQS in [[Page 12504]] each air quality control region within

the State (hereinafter referred to as ``statewide SIP's''). Section

110(a)(2) sets forth the elements that a SIP must contain in order to

be fully approved. These elements are discussed in the General Preamble

for the Implementation of Title I of the Clean Air Act Amendments of

1990 (57 FR 13556-13557).

2. General SIP Requirements--Section 110(a)(2).

(a) Statutory and Existing Regulatory Requirements. Regulations for

the preparation, adoption, and submission of SIP's under section 110 of

the Act were initially published November 25, 1971 (36 FR 22369) and

codified as 40 CFR part 51. The 40 CFR part 51 has been modified from

time to time since then. On November 7, 1986 (51 FR 40656), EPA

restructured and consolidated the 40 CFR part 51 regulations to make

them easier to follow and revise in the future.

The 1990 amended Act did not substantially change the SIP

requirements in section 110(a)(2) of the Act. For the most part, EPA

believes that the existing regulatory framework, i.e., 40 CFR part 51,

defines the general section 110(a)(2) SIP requirements for SO2.

However, as a result of a revised SO2 NAAQS, data handling

practices, and specified SIP submittal timeframes in the Act, some

revisions to 40 CFR part 51 are necessary. The specific revisions to 40

CFR part 51 are discussed in another section entitled ``Regulatory

Revisions.'' The EPA also notes that under section 193, anything in

part 51 that is inconsistent with the 1990 Amendments is superseded

even if EPA has not yet revised the regulations. A discussion of the

statewide SIP requirements is provided below.

(b) Statewide SIP's for the Revised SO2 NAAQS. For the most

part, States have already adopted, as part of their overall SIP for

current SO2 NAAQS, rules or regulations which satisfy the majority

of the general SIP requirements in section 110(a)(2) of the Act and the

existing 40 CFR part 51. At this time, the EPA does not envision that

States will have to develop substantial new general regulations for the

statewide SIP's for the revised SO2 NAAQS. The EPA will issue

appropriate guidance in the future in the event that this assessment

changes.

There are two requirements, in particular, under section 110(a)(2)

that must be met by the States upon promulgation of a revised SO2

NAAQS. Section 110(a)(2)(B) requires the establishment and operation of

appropriate ambient air monitoring systems, data from which must be

made available to the Administrator upon request. Coupled with this is

a requirement under section 110(a)(2)(E) that States have adequate

resources and authority to implement the SIP.

(c) New Source Review Issues. Section 110(a)(2)(C) of the Act

requires States to protect the NAAQS by providing for the regulation of

the construction and modification of stationary sources. In areas that

are designated as attaining the NAAQS, as well as areas that are

designated as unclassifiable under section 107 of the Act, each

implementation plan must contain legally-enforceable requirements which

enable the State to determine whether the construction or modification

of stationary sources will interfere with maintenance of the NAAQS (see

section 161 of the Act). For major stationary sources that locate in

attainment or unclassifiable areas, the Act requires that comprehensive

preconstruction review requirements under PSD of the air quality

program contained in part C, title I, of the Act must be satisfied\1\

(e.g., sections 160-169 of the Act).

\1\The statutory PSD requirements apply to new major stationary

sources and modifications of existing major stationary sources. A

``major stationary source'' is: (1) Any source from a statutory list

of 28 source categories that emits, or has the potential to emit,

100 tons per year (tpy) or more of a regulated pollutant; or (2) any

other source that emits, or has the potential to emit, at least 250

tpy of a regulated pollutant (see section 169(1) of the Act).

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The EPA has set forth SIP requirements at 40 CFR 51.166 containing

the minimum requirements by which a State preconstruction review permit

program will be considered to meet with the statutory requirements for

PSD.\2\ In very broad terms, these requirements provide for the

imposition of best available control technology at new and modified

major stationary sources for each pollutant subject to regulation under

the Act, and provide for review of the potential air quality impacts of

such sources and modifications (e.g., section 165(a) of the Act).

\2\The EPA has also promulgated regulations for a Federal PSD

program at 40 CFR 52.21. The Federal program applies to States that

do not have EPA-approved PSD programs as part of their SIP.

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The current PSD program requirements under 40 CFR 51.166, which

protect the existing primary and secondary NAAQS for SO2, will

also be protective of a new 5-minute SO2 NAAQS in that the

regulations prevent the issuance of a PSD permit to a major source that

would cause or contribute to a violation of any NAAQS (Sec. 51.166(k)).

However, while no changes to the existing requirements are needed to

ensure the new or modified PSD source must evaluate their ambient

impacts against a new 5-minute standard for SO2, EPA has reviewed

certain existing PSD provisions at Sec. 51.166 (and corresponding

provisions at Sec. 52.21) to determine whether changes may be needed to

ensure that a new 5-minute SO2 standard, as proposed in the part

50/53 document, would be adequately protected.

Several of the existing PSD provisions rely on Agency-prescribed

significance levels to determine whether any pollutant that would be

emitted by a new or modified major stationary source must undergo

comprehensive permit review. First, EPA uses significant emissions

rates (expressed in tons per year) to determine whether a regulated

pollutant (other than a pollutant emitted in major amounts) to be

emitted by a new or modified major stationary source must undergo PSD

review3 (e.g., Sec. 51.166(b)(23)(i)).

\3\The PSD review requirements apply to any regulated pollutant

which a new or modified major stationary source would emit in

significant amounts. Thus, a source may be ``major'' for only one

pollutant, but PSD review would apply to other pollutants emitted in

``significant'' amounts.

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Second, significant ambient impact concentrations are used to

determine whether a source must undergo an impact analysis to show that

it will not contribute to a violation of the NAAQS or PSD increments

(Sec. 51.165(b)). Finally, significant monitoring concentrations are

used to determine whether the reviewing authority may exempt a source

from the ambient monitoring requirements for a particular pollutant

(e.g., Sec. 51.166(i)(8)).

As described below, the EPA examined each applicable significance

level used for SO2 in order to determine whether a 5-minute

standard for SO2 would necessitate any revisions to the existing

levels. In each case, EPA has determined that sufficient information is

not presently available to warrant any revision to the existing levels.

The significant emissions rate for SO2 is currently defined as

an emissions rate of 40 tpy or more under the PSD regulations. New or

modified sources that would emit significant amounts of SO2 must

undergo PSD review for that pollutant. Conversely, de minimis amounts

of SO2 emissions are exempt from further review. The existing

significance level for SO2 is based on the premise that an

emissions rate that would result in ambient concentrations equaling at

least 4 percent of the 24-hour primary standard should be considered

significant (45 FR 52676, 52707-52708 (August 7, 1980)). In order to

help determine whether the existing [[Page 12505]] significant

emissions rate for SO2 would be appropriate, based on the same

criteria, for the proposed 5-minute standard, EPA would need to predict

the 5-minute concentration that results from a source emitting 40 tpy

of SO2. The absence of an approved methodology for either directly

modeling 5-minute SO2 concentrations or converting modeled

concentrations of SO2 from a given averaging period (e.g., 3-hour,

1-hour) to a 5-minute average precludes EPA from completing its

analysis of the adequacy of the existing significant emissions rate.

Should EPA adopt a 5-minute NAAQS for SO2, EPA will further study

the need for revisions of the significant emissions rate.

Because of the present difficulties associated with efforts to

model 5-minute ambient concentrations of SO2, EPA has also

determined that it would be inappropriate to establish a significant

ambient impact level for a 5-minute SO2 NAAQS. In the event that

adequate data and the appropriate performance evaluations become

available to support the use of dispersion models to estimate 5-minute

SO2 concentrations in the future, EPA will consider the

establishment of a 5-minute SO2 significant ambient impact

concentration.

Under the existing regulations, the reviewing authority may exempt

a proposed major stationary source from the PSD pre-application

monitoring requirements (40 CFR 51.166(m)) if either the air quality

impacts resulting from the source, or the existing ambient

concentrations of the particular pollutant in the area of the source,

are less than the prescribed significance level for that pollutant. For

SO2, the significance level is 13 g/m\3\ (24-hour

average). Since models are not available for a source to project its

ambient impact for 5-minute averaging periods, EPA believes that

consideration of a new significance level for SO2 based on a 5-

minute averaging time is not practical at this time. Instead, EPA

proposes to continue using the existing 24-hour significance level in

conjunction with the pre-application monitoring requirement at 40 CFR

51.166(m). Thus, if a source finds that it must gather ambient data for

SO2, based on ambient impacts and existing air quality

concentrations exceeding the SO2 significance level, then the

applicant will be required to gather 5-minute air quality data in

addition to data for all other applicable averaging periods for

SO2.

As indicated in the preceding discussion, for several different PSD

program elements, EPA proposes to retain existing SO2 significance

levels instead of pursuing the possibility of revising the significance

levels based on a new 5-minute SO2 NAAQS. The EPA requests the

public's views about this proposed use of existing significance levels.

The PSD program also includes specific air quality limitations,

known as increments, which define maximum allowable increases in

pollutant concentrations. These increments prevent unlimited increases

in ambient pollutant concentrations beyond a determined baseline

concentration for a particular area.4 Section 166 of the Act

authorizes EPA to promulgate new increments within 2 years from the

date of promulgation of new NAAQS. The existing PSD regulations include

increments for SO2 for the 3-hour, 24-hour and annual averaging

periods. The EPA will determine the need for a 5-minute increment for

SO2, especially in light of the present difficulties which

restrict the Agency's ability to use air quality dispersion models to

determine the amount of increment that would be consumed by new and

modified SO2 sources for a 5-minute averaging period. The EPA will

also investigate the feasibility of developing and implementing

alternatives to numerical air quality increments (expressed in

g/m\3\), as authorized under section 166(d) of the Act. In any

event, EPA will not propose new increments for SO2 until such time

that a new 5-minute SO2 NAAQS is first promulgated.

\4\The PSD areas (areas designated as attainment or

unclassifiable under section 107 of the Act) are further categorized

as Class I, II, or III areas (section 162 of the Act). Each of these

classifications determines the ``maximum allowable increases'' or

increment of air quality deterioration permissible (section 163 of

the Act). Only a relatively small increment of air quality

deterioration is permissible in Class I areas and consequently these

areas are afforded the greatest amount of air quality protection. An

increasingly greater amount of air quality deterioration is allowed

in Class II and III areas.

Air quality deterioration is measured from the date on which the

first PSD application is submitted. This date becomes the baseline

date after which any change in actual emissions affects the

allowable increment. In all instances, however, the NAAQS represent

the overarching air quality ceiling that may not be exceeded,

notwithstanding any allowable increment.

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(d) Schedule for Submittal of Section 110(a)(1) SIP's. Section

110(a)(1) states that the SIP's required by that subsection are to be

submitted to EPA ``within 3 years (or such shorter period as the

Administrator may prescribe) after the promulgation of a national

primary ambient air quality standard (or any revision thereof) under

section 109.'' Such SIP's are to provide for ``implementation,

maintenance and enforcement'' of the new NAAQS. Section 110(a)(1),

however, must be read in light of the timetable for designations of

areas as nonattainment, attainment, or unclassifiable under section

107(d)(1) described above, and the explicit timetables for SIP

submissions for nonattainment areas under part D of title I. Section

107(d)(1) provides that designations must occur within 3 years of the

promulgation of a new NAAQS and the part D provisions (sections 172(b)

and 191(a)) provide for the submission of SIP's meeting the

requirements of section 172(c) within a specified time period following

the designation of an area as nonattainment.

The EPA believes that these provisions can best be harmonized in

the context of a new 5-minute SO2 NAAQS by interpreting the

section 110(a)(1) deadline as being satisfied by the submission of SIP

elements whose content does not depend on the designation of an area.

In the case of SIP's concerning a new 5-minute SO2 NAAQS, EPA

believes that such submissions would be limited to SIP revisions

concerning compliance with the monitoring requirements of section

110(a)(2)(B) and the resource requirements of section 110(a)(2)(E). The

EPA believes that, until a problem with maintaining a new 5-minute

NAAQS is identified, it is reasonable to view the already-existing

substantive SIP provisions as adequate and that it would be absurd to

require areas to adopt additional control requirements or emission

limitations prior to the identification of particular problem sources.

The EPA notes that any areas designated nonattainment will be subject

to further SIP submission deadlines requiring the submission of

nonattainment area SIP's under part D of title I that satisfy the

substantive requirements of section 172(c).

Moreover, with respect to the monitoring and resource SIP elements,

EPA believes that any changes to existing SIP's that would be needed

will not be significant in terms of scope or effort. Indeed, some

States may have to make minimal or no changes to their own rules in

order to implement the new monitoring requirements. For this reason,

and because the changes in monitoring requirements will assist in

developing information about ambient air quality that will be relevant

to designations, EPA is proposing that all States submit any needed SIP

revisions within 1 year of final action on today's proposal.

D. Nonattainment Area Requirements

Areas designated nonattainment must meet the SIP requirements of

part D of title I as well as the requirements of section 110. The

provisions of part D [[Page 12506]] pertinent to SO2 areas are

those contained in subparts 1 and 5. These provisions have been

described previously in the General Preamble for the Implementation of

Title I of the Clean Air Act Amendments of 1990 (57 FR 13498), and the

following discussion will focus on the requirements of particular

relevance to the implementation of a new NAAQS.

1. Attainment and SIP Submittal Dates

To determine the attainment dates and SIP submittal dates

applicable to a new SO2 NAAQS, it is necessary to analyze the

relationship of the relevant provisions of both subpart 1 and subpart

5.

The starting point for the analysis is section 172(a) in subpart 1.

Section 172(a)(2)(A) provides that the attainment date for attaining a

primary NAAQS is the date by which attainment can be achieved as

expeditiously as practicable, but not later than 5 years from the date

of designation under section 107(d). It also provides that EPA may

extend the attainment date to the extent appropriate, for a period of

up to 10 years after designation, considering the severity of the air

quality problem and the feasibility and availability of pollution

control measures. Section 172(a)(2)(D), however, provides that ``[t]his

paragraph (paragraph (2)) shall not apply with respect to nonattainment

areas for which attainment dates are specifically provided under other

provisions of this part.'' This language therefore leads to the

question of whether areas designated nonattainment with respect to a

new SO2 NAAQS are areas for which attainment dates are provided

elsewhere in part D of title I.

As subpart 5 establishes attainment dates for certain SO2

nonattainment areas, the issue is whether those provisions establish

attainment dates for areas designated nonattainment with respect to a

new SO2 NAAQS. Of particular relevance are sections 192(a) and

191(a). Section 192(a) provides that SIP's required under section

191(a) provide for attainment ``as expeditiously as practicable but no

later than 5 years from the date of the nonattainment designation.''

Section 191(a) requires that ``[a]ny State containing an area

designated or redesignated under section 107(d) as nonattainment with

respect to the national primary ambient air quality standards for

sulfur oxides, nitrogen dioxide, or lead subsequent to the date of the

enactment of the Clean Air Act Amendments of 1990 shall submit to the

Administrator, within 18 months of the designation, an applicable

implementation plan meeting the requirements of this part.''

One possible interpretation of the Act is that the language of

section 191(a) applies to areas designated nonattainment with respect

to a new SO2 NAAQS promulgated after the enactment of the 1990

Amendments. If that interpretation is followed, section 192(a), rather

than section 172(a)(2), would determine the attainment date for those

areas. This is due to the language in section 172(a)(2)(D) providing

that section 172(a)(2) does not apply to areas for which attainment

dates are specifically provided elsewhere in part D. The language of

section 191(a), rather than section 172(b), would also apply to the

establishment of the SIP submittal date for nonattainment SIP's

required to implement the new NAAQS. The consequence of this

interpretation for the attainment deadline is that the 5-year

attainment deadline of section 192(a) would apply, rather than the 5-

year deadline that can be extended to 10 years under certain conditions

under section 172(a). As far as SIP submittal deadlines are concerned,

section 191(a)'s 18-month deadline would apply rather than section

172(b)'s 3-year deadline.

An alternative interpretation is that the provisions of subpart 5

were intended to apply only to attainment dates and SIP submittal

deadlines concerning a NAAQS in existence at the time of the enactment

of the 1990 Clean Air Act Amendments. Under this view, the general

provisions of subpart 1 (i.e., sections 172(a)(2)(A) and 172(b)) would

apply to the determination of attainment dates and SIP submittal

deadlines pertaining to a new SO2 NAAQS promulgated after the 1990

Amendments. The EPA notes, however, that it believes that an 18-month

SIP submittal deadline would provide adequate time for the States to

develop and submit their SIP's regarding a new NAAQS. It would also

provide more time to implement the control strategy adopted in the SIP,

which EPA believes is preferable. If the maximum period of 3 years were

allowed, there would only be 2 years between the date of the submittal

of the SIP and the 5-year attainment date, and even less time between

EPA's final action regarding the approvability of the SIP's and the

attainment date. Consequently, even if the provisions of section 172(b)

were to apply to SIP submittal deadlines for a new NAAQS, EPA would

require States to submit their SIP's within an 18-month timeframe

pursuant to section 172(b)'s authority to establish a shorter period

than the maximum 3-year period.

The EPA requests comment on both of these interpretations and the

consequences that they lead to regarding the establishment of

attainment dates and SIP submittal deadlines for a new SO2 NAAQS.

2. Classifications--Section 172(a)(1)

The classification provisions (section 172(a)(1)) give EPA the

authority to classify nonattainment areas for the purposes of applying

attainment dates (section 172(a)(2)(A)). In exercising this authority,

EPA may consider such factors as the severity of the nonattainment

problem or the availability and feasibility of the pollution control

measures. Based upon the classification, EPA may set later attainment

dates for areas with more severe air quality problems (section

172(a)(2)(A)).

At the present time, EPA does not intend to establish a

classification scheme for areas which violate the new 5-minute SO2

NAAQS. Currently the SO2 program does not have a classification

scheme since, typically, within the SO2 program the severity of

the SO2 ambient air quality is not a factor in attaining the NAAQS

once the needed control measures are put in place. The EPA believes

that in most of the areas designated nonattainment for the new 5-minute

NAAQS, the cause of the high SO2 concentrations (usually a single

source) will be obvious. While the method of controlling these

emissions may not be as obvious, the control measure should result, in

most cases, in a single step correction of any future violations.

Consequently, EPA does not believe a classification scheme is necessary

or appropriate.

3. Nonattainment Plan Provision--Section 172(c)

Section 172(c) lists the requirements to be met by a nonattainment

SIP. Some of those requirements are discussed below in the context of a

SIP submittal for a SO2 NAAQS nonattainment area.

a. Statutory and Existing Regulatory Requirements. As previously

indicated, regulations for the preparation, adoption, and submission of

SIP's were initially published November 25, 1971 and codified as 40 CFR

part 51. The 40 CFR part 51 has been modified from time to time since

then. However, the most current guidance on how EPA intends to

interpret the 1990 Amendments is found in the General Preamble (57 FR

13498, April 16, 1992).

The 1990 Amendments added section 172(c) which prescribes the

nonattainment SIP requirements. To the extent that the existing SIP

regulations that have been codified in 40 CFR parts 51 and 52 do not

conflict with section 172(c), EPA will rely on them to carry out the

requirements of section 172(c). [[Page 12507]] As necessary EPA will

adopt new or modify existing regulations to carry out other provisions

of section 172(c). For further information on potential changes to 40

CFR part 51 with respect to SO2, see the separate section entitled

``Regulation Revisions.'' Also, as noted earlier under section 193,

anything in part 51 that is inconsistent with the 1990 Amendments is

superseded even if EPA has not yet revised the regulations.

b. Reasonably Available Control Measures (Including Reasonably

Available Control Technology). Section 172(c)(1) requires SIP's to

``provide for the implementation of all reasonably available control

measures (RACM) as expeditiously as practicable (including such

reductions in emissions from existing sources as may be obtained

through the adoption, at a minimum, of reasonably available control

technology (RACT)) and shall provide for attainment of the national

primary ambient air quality standards.'' Historically, EPA has defined

RACT as ``the lowest emission limit that a particular source is capable

of meeting by the application of control technology that is reasonably

available considering technological and economic feasibility (Strelow,

1976).'' In the case of a new 5-minute SO2 NAAQS, EPA believes

that RACT should be interpreted in accordance with EPA's long-standing

interpretation.

The EPA notes that, as the sources of any violations of a new

SO2 NAAQS should be readily identifiable, there should not be any

questions about the identity of the sources to which RACT should be

applied. Thus, in the case of a new SO2 NAAQS, compliance with

EPA's general recommendation that available control technology be

applied to those existing sources in the nonattainment area that are

reasonable to control in light of the attainment needs of the area and

the feasibility of such controls should be readily achieved (EPA 1992c,

n. 20, 57 FR 13541).

While a plan must require the implementation of RACM needed to

attain within the statutory timeframes, it need not require the

adoption of all available control measures if it demonstrates

attainment as expeditiously as practicable without the adoption of all

measures. The EPA believes it would be unreasonable to require that a

plan which demonstrates attainment include all technologically and

economically available control measures if such measures would not

expedite attainment. Thus, it is possible that some available control

measures may not be ``reasonably'' available, and not required by RACM,

because their implementation would not expedite attainment (EPA 1992c,

57 FR 13543).

In addition to available control technology that should be fully

considered in identifying RACT for purposes of the current SO2

NAAQS, RACT for purposes of a new 5-minute NAAQS would also include

consideration of maintenance and process operating procedures at

SO2 sources that will achieve the new NAAQS within the statutory

timeframes. The EPA believes that such available control measures

should be fully assessed, in light of the general guidance above, in

determining RACM (including RACT) for purposes of implementing a 5-

minute SO2 NAAQS.

c. Emission Inventory. Section 172(c)(3) states that the SIP shall

include a comprehensive, accurate, current inventory of actual

emissions from all sources of SO2 in the nonattainment area and

that EPA may require periodic revisions of the inventory as determined

necessary to assure that the requirements of part D are met. Typically

for most nonattainment areas, determining the nature and extent of

specific control strategies needed requires an emissions inventory.

Also, typically, an emission inventory should be based on measured

emissions or documented emission factors. The more comprehensive and

accurate the inventory, the more effective the control evaluation.

However, in terms of a new 5-minute NAAQS, measured emissions or

emission factors for the probable sources of 5-minute NAAQS

exceedances, process upsets, equipment malfunctions, batch processes,

startup/shutdown, and fugitive emissions, are almost nonexistent. It is

anticipated that most nonattainment areas for the 5-minute SO2

NAAQS will be defined by a single source as measured by a monitor or

monitors close to the source. Thus, in most cases, the part D SIP for a

nonattainment area will fulfill the inventory requirements of section

172(c)(3) by identifying the source around which the monitors were

located and which may have caused the monitored problem. In situations

where it is technically feasible, emission estimates should be made

using emission measurements or factors.

d. Control Strategy Demonstration. The EPA has historically

required dispersion modeling for setting emission limits. However,

because of the limitations of models in predicting 5-minute

concentrations, other methods may have to be used. Control strategy

demonstrations may have to rely on monitors as evidence of adequacy of

the implemented emission reductions as being protective of the 5-minute

NAAQS. In certain cases, the monitors may be used for setting the

emission limits. The EPA intends to rely on section 11.2.2 of the

Modeling Guideline which addresses requirements for using monitoring

networks to set emission limits.

e. Reasonable Further Progress. As stated in the General Preamble

(57 FR 13547), section 171(l) of the amended Act defines reasonable

further progress as ``such annual incremental reductions in emissions

of the relevant air pollutant as are required by this part (part D) or

may reasonably be required by EPA for the purpose of ensuring

attainment of the applicable national ambient air quality standard by

the applicable date.'' This definition is most appropriate for

pollutants which are emitted by numerous and diverse sources, where the

relationship between any individual source and the overall air quality

is not explicitly quantified, and where the emission reductions

necessary to attain the NAAQS are inventorywide. The definition is

generally less pertinent to pollutants such as SO2, particularly

for the proposed new NAAQS, which usually have a limited number of

sources, relationships between individual sources and air quality which

are relatively well defined, and emissions control measures which

result in swift and dramatic improvement in air quality. That is, for

SO2, there is usually a single ``step'' between pre-control

nonattainment and post-control attainment.

Therefore, for a new 5-minute SO2 NAAQS, with its discernible

relationship between emissions and air quality and significant and

immediate air quality improvements, RFP will continue to be construed

as ``adherence to an ambitious compliance schedule.''5 The

compliance schedule for a new 5-minute NAAQS could consist of

implementation of a maintenance program where the source of emissions

is due to frequent malfunction of a control device. The SIP's which

require RFP as just described for an SO2 nonattainment area will

be considered as meeting the requirements of section 172(c)(2).

\5\U.S. Environmental Protection Agency, Office of Air Quality

Planning and Standards, ``Guidance Document for Correction of Part D

SIP's for Nonattainment Areas,'' (Research Triangle Park, North

Carolina, January 27, 1984), page 27.

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f. Permits for New and Modified Major Stationary Sources. Section

172(c)(5) of the Act states that the SIP shall require permits for the

construction and operation of new or modified major stationary sources

(i.e., stationary [[Page 12508]] sources which emit or have the

potential to emit at least 100 tpy of any nonattainment pollutant or

lesser amounts in certain nonattainment areas) anywhere in a

nonattainment area, in accordance with section 173 of the Act.6 In

nonattainment areas, a presumption exists that emissions increases

resulting from new and modified major stationary sources will adversely

affect the area; thus, in lieu of a complete air quality impact

analysis (including ambient monitoring), emissions reductions (offsets)

from existing sources must be obtained in order to mitigate the ambient

impacts resulting from the potential emissions from the proposed new

source, or net emissions increase from a proposed major modification to

an existing source (e.g., section 173(c) of the Act).

\6\For purposes of the nonattainment NSR requirements under part

D of title I of the Act, ``major stationary source'' is defined as

any stationary source which emits, or has the potential to emit, 100

tpy (or lesser amounts in certain nonattainment areas) of any

nonattainment pollutant (see, e.g., sections 182(c-e), 189(b)(3),

and 302(j) of the Act).

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Under the nonattainment NSR program (40 CFR 51.165(a)), EPA uses

significant emissions rates (expressed in tons per year) for pollutant

applicability purposes to determine whether a modification of an

existing major stationary source will result in a significant net

emissions increase (Sec. 51.165(a)(1)(x)). For the same reasons

described in section V.C of this preamble, EPA does not now intend to

propose to revise the significant emissions rate for SO2

commensurate with the 5-minute SO2 NAAQS proposed in the part 50/

53 document. Public comment is requested as to whether the existing 40

tpy significant emissions rate needs to be revised if EPA promulgates

the proposed 5-minute SO2 standard.

Major new or modified sources locating in the nonattainment area

will be required to meet the lowest achievable emission rate, obtain

emissions offsets, and satisfy other applicable requirements under

section 173 of the Act. With implementation of a new 5-minute NAAQS,

these requirements may be addressed by existing permit programs for

those areas already designated nonattainment for SO2 and meeting

the nonattainment NSR requirements under section 173 of the Act.

However, for those States without the appropriate nonattainment NSR

program, the State would need to develop and implement such a program

for any newly designated nonattainment areas resulting from a new 5-

minute NAAQS for SO2.

g. Contingency Measures. Section 172(c)(9) of the amended Act

defines contingency measures as measures that become effective without

further action by the State or EPA, upon determination by EPA that the

area has failed to: (1) Make reasonable further progress, or (2) attain

the SO2 NAAQS by the applicable statutory deadline.

For current SO2 programs, EPA interprets ``contingency

measures'' to mean that the State agency has a comprehensive program to

identify sources of violations of the SO2 NAAQS and to undertake

an aggressive followup for compliance and enforcement, including

expedited procedures for establishing enforceable consent agreements

pending the adoption of revised SIP's. The rationale for this

interpretation as presented in the General Preamble (57 FR 13547) is

the following. The EPA interprets the contingency measure provisions as

primarily directed at general programs which can be undertaken on an

areawide basis. First, for some criteria pollutants, the analytical

tools for quantifying the relationship between reductions in emissions

and resulting air quality improvements remain subject to significant

uncertainties, in contrast with procedures for pollutants such as

SO2 and its current NAAQS. Second, emission estimates and

attainment analyses can be strongly influenced by overly optimistic

assumptions about control efficiency and rates of compliance for many

small sources. In contrast, controls for the current SO2 NAAQS are

well understood and are far less prone to uncertainty. Since SO2

control measures are by definition based upon what is directly and

quantifiably necessary to attain the SO2 NAAQS, it would be

unlikely for an area to implement the necessary emissions control yet

fail to attain the NAAQS.

However, for the proposed 5-minute SO2 NAAQS, EPA will need to

interpret requirements for contingency measures different from those

for the current NAAQS, due to the nature of sources and emissions that

EPA considers likely to cause violations. As opposed to the current

NAAQS, which can rely on dispersion models to predict attainment of the

NAAQS, the State and Local agencies cannot reliably predict that

attainment will be achieved even with proper implementation of a

control program. It is possible that even with the control equipment

operating properly, violations may persist. In other words, there may

be overly optimistic assumptions about control efficiencies and

emission rates. Therefore, contingency measures for the proposed 5-

minute NAAQS will require more than aggressive follow-up for compliance

and enforcement as allowed for the current SO2 NAAQS. As an

example, if the cause of the SO2 violations is due to control

equipment failure, a SIP may require a more rigorous maintenance

schedule. If further violations occur due to continued failures of the

control equipment, then the contingency measures may need to invoke a

more frequent inspection/maintenance program of the control equipment

or even installation of backup control equipment.

E. SIP Processing Requirements

1. SIP Completeness

Section 110(k)(1) required EPA to promulgate minimum criteria that

any SIP submittal must meet. The EPA proposed an initial set of

completeness criteria at 56 FR 23826 (May 24, 1991) and finalized them

at 56 FR 42216 (August 26, 1991). Those notices describe the procedures

for assessing whether a SIP submittal is complete and, therefore,

adequate to trigger the Act requirement that EPA review and take action

on the submittal. The completeness criteria provide a procedure and

criteria that enable States to prepare adequate SIP submittals and

enable EPA reviewers to promptly screen SIP submittals, identify those

that are incomplete, and return them to the State for corrective action

without having to go through rulemaking. The EPA intends to use the

completeness criteria as amended in 40 CFR part 51, appendix V, to

determine completeness of SIP submittals as required under section

110(k)(1)(B).

2. Approval/Disapproval of Plan

The Act as amended in 1990 allows for EPA to make full and partial

approvals and disapprovals under section 110(k)(3) and conditional

approvals under section 110(k)(4) of SIP submittals. In meeting the

requirements under section 110(k)(3) and (4), EPA intends to follow the

guidance for processing SIP submittals issued in the memo from Calcagni

to the Regional Air Division Directors dated July 9, 1992.

3. Sanctions and Other Consequences of SIP Deficiencies

The EPA intends to use sanctions consistent with the following

stated policies and regulations as provided for by the Act in sections

110(m) and 179 for the imposition of sanctions in the event that EPA

finds that a State did not make a required SIP submission (in whole or

in part), finds that a State did not submit a complete submission,

[[Page 12509]] disapproves in whole or in part a required submission,

or finds that any part of an approved SIP is not being implemented.

Section 179(a) provides for the imposition of mandatory sanctions

unless the deficiency identified by EPA (e.g., the failure to submit or

disapproval) is corrected within 18 months. Moreover, section 110(m)

provides EPA with the discretionary authority to impose sanctions at

any time after a finding, disapproval or determination under section

179(a).

With respect to mandatory sanctions, section 179(a) provides that

unless the State corrects the deficiency within 18 months, one of the

two sanctions referred to in section 179(b) (i.e., highway or offset

sanctions) shall be selected by EPA and will apply until EPA determines

that the State has come into compliance. (In the case of a finding of

failure to submit a required SIP revision, the sanctions would not be

lifted until EPA determines that the State has submitted a SIP revision

that satisfies the completeness criteria.) If 6 months after the

imposition of the first sanction the State still has not corrected the

deficiency, then the second sanction shall apply as well. If EPA finds

a lack of good faith on the part of the State, then both the highway

and offset sanctions are applied 18 months after the finding or

disapproval.

The EPA has discussed in detail issues concerning the imposition of

sanctions in a number of Federal Register notices. The criteria for

imposing discretionary sanctions on a statewide basis are discussed in

a February 11, 1994 Federal Register notice, Criteria for Exercising

Discretionary Sanctions Under Title I of the Clean Air Act (59 FR

1476), and are codified at 40 CFR 52.30. The preamble to this notice

also sets forth EPA's policy with respect to section 110(m) sanctions.

Mandatory sanctions were discussed in a October 1, 1993 proposal (58 FR

51270) and in the August 4, 1994 final rule (59 FR 39832) selecting the

order of mandatory sanctions under section 179. That final rule does

not apply to State failures to respond to SIP calls. The EPA intends to

address sanctions for such failures in a future rulemaking.

Apart from sanctions under sections 110(m) and 179(b), other

consequences may also attach to a failure to comply with the Act's SIP

submission or implementation requirements. First, section 179(a)

authorizes EPA to withhold all or part of section 105 grants for air

pollution control planning and control programs. Second, section

110(c)(1)(B) provides that within 2 years of a finding that a State has

failed to make a required submittal, a finding that a required

submittal was not complete, or a disapproval of a submission (in whole

or in part), EPA shall promulgate a FIP unless EPA approves a submitted

SIP that corrects the deficiency. In support of this requirement, EPA

intends to use its authority to withhold all or part of section 105

grants to develop and implement FIP's where a State fails to comply

with the Act's SIP submission or implementation requirements.

VI. Significant Harm Levels and Episode Criteria

In a notice published in the Federal Register on April 26, 1988 (53

FR 14926), in which the EPA proposed not to revise the SO2 NAAQS,

the EPA at the same time proposed to revise the significant harm levels

for SO2. Since final action was never taken on that proposal, EPA

is reproposing to revise the 24-hour significant harm levels.

Section 303 of the Act authorizes the Administrator to take certain

emergency actions if pollution levels in an area constitute ``an

imminent and substantial endangerment to public health or welfare, or

the environment.'' The Act and EPA's regulations governing adoption and

submittal of SIP's (section 110(a)(2)(G) and 40 CFR 51.16 and subpart H

of part 51) require States to adopt contingency plans to prevent

ambient pollutant concentrations from reaching specified significant

harm levels and to take additional abatement actions if such levels are

reached. The existing significant harm levels (40 CFR 51.16a) for

SO2 were established in 1971 (36 FR 24002, November 21, 1971) at

the following levels: SO2 alone--1.00 ppm (2620 g/m\3\)

24-hour average of SO2; and SO2 x tsp--490 x 103

(g/m\3\) 2--24-hour average product of SO2 and tsp

concentrations.

On the basis of EPA's reassessment of the data upon which these

levels were based and its assessment of more recent scientific evidence

on sulfur oxides and particulate matter, EPA proposes to revise the

significant harm levels for SO2.

In actions related to the revisions of the particulate matter

standards, EPA has already eliminated the combined tsp/SO2

significant harm level (52 FR 24672, July 1, 1987). In doing so, EPA

left open the possibility of reinstating an SO2/PM-10 significant

harm level, if necessary for additional protection against SO2

effects, at the conclusion of the SO2 review. The scientific data

suggest that SO2 in combination with high levels of particulate

matter have been associated with increases in daily mortality. The

final 24-hour PM-10 significant harm level of 600 g/m3

takes this potential interaction into account. Addition of a combined

SO2/PM-10 significant harm level therefore appears unnecessary.

Removal of the combined significant harm level raises the question

as to whether the remaining SO2 significant harm level is

sufficient. The possibility that SO2 alone or in combination with

other pollutant or fog droplets may be in part responsible for the

effects associated with 24-hour exposures suggests the need to continue

a 24-hour significant harm level for SO2 alone at a substantially

lower concentration. The EPA's assessment of studies of daily mortality

(EPA, 1986a, Table 1 and EPA, 1986b Table 4-2) indicates greatest

certainty of some increased daily mortality associated with high

particle concentrations in combination with SO2 levels at or above

750 g/m\3\ (0.29 ppm) for 24-hours. Accordingly, EPA proposes

to revise the 24-hour SO2 significant harm level from 1.0 (2,620

g/m3) to 0.29 ppm (750 g/m\3\).

Appendix L to part 51 contains example air pollution episode levels

and example contingency plans for the purpose of preventing air

pollution from reaching the significant harm levels prescribed in

section 51.151. The examples in appendix L serve as guides to States

for the development of their own contingency plans. To conform with the

proposed revisions to the significant harm level for SO2, certain

changes to appendix L are required. The EPA proposes the following

revisions to the example 24-hour episode levels for SO2:

(1) That the example alert level for SO2 be changed from 800

g/m3 to 0.19 ppm (500 g/m3), 24-hour

average.

(2) That the example warning level for SO2 be changed from

1600 g/m3 to 0.23 ppm (600 g/m3), 24-hour

average.

(3) That the example emergency level for SO2 be changed from

2100 g/m3 to 0.26 ppm (675 g/m3), 24-hour

average.

The basis for changing the episode levels for SO2 is the same

as discussed above for the revisions to the significant harm level.

With respect to example episode levels, the proposed alert level

reflects the upper bound of the 24-hour range of interest for the NAAQS

presented in the staff paper addendum (EPA, 1986b, Table 2). The staff

paper concludes that at or above 0.19 ppm (500 g/m3) for

24 hours, health effects are likely to occur in certain sensitive

population groups (EPA, 1982a, page 72). Therefore, it would be

appropriate under the episode criteria to initiate first stage control

action when this ambient level of SO2 occurs. The proposed 24-

[[Page 12510]] hour warning and emergency levels are set at increments

between the proposed alert level and the proposed significant harm

level. This approach would provide opportunity for the control actions

associated with each episode level to take effect before the next stage

is triggered and additional control actions become necessary. This

proposal, if adopted, would change the 24-hour significant harm level.

Therefore, States would be required to adopt the new numerical level,

to evaluate the emergency episode provisions, in their current SIP's

and any permits containing such provisions and to make any revisions

necessary to assure their adequacy.

All public comments on the proposed significant harm level and

episode criteria will be considered by the Agency as it makes a

decision on the final significant harm level.

VII. Proposed Revisions to Part 58 Monitoring Regulations

The proposed revisions to 40 CFR part 58 are needed to allow States

to reduce in most cases the number of NAMS SO2 monitors in the

metropolitan areas. This, in turn, will free up monitors and resources

that can be used toward the SO2 targeted implementation strategy.

The following preamble details requirements which will be implemented

regardless of the regulatory alternative that is ultimately selected

for part 50.

A. Section 58.1 Definitions

The number of SO2 monitors in the revised NAMS network for

major metropolitan areas will be based on factors including population,

historical ambient concentration measurements, and total SO2

emissions. The SO2 emissions data are available from the AIRS for

each county and for each consolidated metropolitan statistical area/

metropolitan statistical area (CMSA/MSA). Therefore, the requirements

for NAMS SO2 stations have been determined on a CMSA/MSA basis,

and the requirements for SLAMS SO2 stations have been determined

on a county basis. Definitions are added for CMSA and MSA as provided

by the U.S. Census Bureau.

B. Appendix C--Ambient Air Quality Monitoring Methodology

As explained in a related notice in this issue of the Federal

Register that proposes amendments to part 53, continuous ambient air

monitoring analyzers designed to obtain 1-hour average SO2

concentration measurements may not provide accurate 5-minute average

concentration measurements. That notice proposes special supplemental

performance specifications applicable to continuous SO2 analyzers

that would be used for 5-minute monitoring so that the average SO2

concentration measurements would be accurate. A companion amendment to

appendix C of part 58 is needed to specifically require the use of

these specially approved analyzers for 5-minute monitoring in SLAMS

monitoring networks. Accordingly, a new section 2.4 is proposed to

require that monitoring methods used for 5-minute average SO2

measurements meet the special supplemental specifications proposed to

be added to part 53.

C. Appendix D--Network Design for State and Local Air Monitoring

Stations (SLAMS) and National Air Monitoring Stations (NAMS)

Appendix D is being revised to change the NAMS requirements for

SO2 monitors. The present requirements are based on measuring

population exposure over a large area without being unduly influenced

by point sources. Because concentrations at a significant number of

these sites have decreased over time and many are measuring

concentrations well below the current SO2 NAAQS, EPA believes that

they may be put to better use if relocated. The monitors which may be

moved could be used to complete the minimum NAMS and SLAMS requirements

or to implement the targeted monitoring strategy for point sources of

SO2 emissions described earlier in this notice (section II:

Targeted Implementation Strategy). Up to three SO2 monitors would

be required for each metropolitan area for trends purposes and general

urban air quality analyses. The new number of NAMS monitors required

for each metropolitan area would be based on the combination of

population and SO2 emissions, as defined in the Air Facility

Subsystem of AIRS and other information. The EPA solicits comments on

reducing the requirements for the number of population-oriented NAMS

SO2 monitors in the metropolitan areas.

In addition to changing the criteria for the required number of

NAMS monitors as noted above, new criteria are being included for a

minimum number of SLAMS SO2 monitors for those counties (or parts

of counties) not a part of any CMSA/MSA but with significant SO2

emissions. These counties with SO2 emissions greater than 20,000

tons/year, as defined in the Air Facility Subsystem of AIRS, would be

required to have one to two monitors. However, EPA is proposing a

provision which would allow for a waiver of all (or part of) these

monitoring requirements after a 2-year monitoring period in accordance

with EPA guidelines for network review for source-oriented SO2

monitoring in nonurban areas. Although these guidelines have not been

developed at this time, EPA solicits comments on the waiver provision

criteria to be established and included in the guideline as well as the

minimum number of years for data collection. The EPA also solicits

comments on the requirement for SO2 SLAMS monitors in these areas.

As discussed earlier in this notice, EPA believes there are a

significant number of sources of SO2 emissions which can produce

high 5-minute ambient concentrations of SO2. These 5-minute

concentrations have the potential to exceed the level for a proposed 5-

minute SO2 NAAQS or the trigger level which may be established

under the authority of section 303 of the Act. The sources which are

believed to provide these high concentrations would be targeted for

monitoring as discussed earlier in this notice. States will be required

to prepare a targeted SO2 monitoring plan containing a listing of

sources to be monitored, the schedule for monitoring, and the rationale

for selecting the sources. The schedule for monitoring should be as

expeditious as practicable. It is expected that the resources which are

made available by the reconfiguration of the NAMS and SLAMS networks

will be used to implement the targeting strategy around selected

SO2 sources. The targeted SO2 monitoring plan will be

reviewed as part of the annual network review.

The number of SO2 monitors to be used around the targeted

sources depends on several diverse factors, i.e. quantity of SO2

emissions, meteorology, terrain, stack height and diameter of stack,

temperature and velocity of stack emissions, distance from point of

emissions to fence line and populated areas, batch operations, etc. To

capture high peak 5-minute concentrations may require many monitors

around the sources (Sonoma Technology Inc., 1994). However, it is not

economically feasible to place enough monitors around the source to

capture all potential exceedances of the NAAQS or trigger level.

Therefore, EPA is using a more moderate approach on the number of

monitors required.

The EPA is proposing a minimum requirement of four SO2

monitors to measure 5-minute, 3-hour, 24-hour, and annual average

SO2 concentrations around the targeted sources. These monitors

could be point SO2 monitors, open path SO2 analyzers, or a

combination of both. If open path [[Page 12511]] analyzers with

multiple monitoring paths are used, each monitoring path could

potentially be substituted for one point SO2 monitor. Modeling,

and perhaps saturation monitoring (a short term study involving the use

of portable monitors deployed around the source), could be used to

determine the area of expected maximum concentration based on the most

predominant wind direction. One monitor would be placed at the fence

line downwind of the predominant wind direction. A second monitor would

be placed in the modeled maximum concentration area based on the

predominant wind direction. Since wind directions around an SO2

source may be significantly different from one season to another, this

same procedure would be repeated for the second most frequent wind

direction. For some cases, two or more of these locations may coincide

and thereby reduce the number of monitors, or allow for a State or

local agency to locate sites in alternative locations. In other cases,

additional monitors would probably be needed for situations of complex

terrain and/or meteorology. The EPA also encourages the use of open

path SO2 analyzers in combination with point SO2 monitors to

obtain better spatial coverage around the targeted sources. One open

path SO2 analyzer using multiple monitoring paths could

potentially replace several of the point SO2 monitors, depending

on factors such as meteorology, terrain, and obstructions. Open path

analyzers may be particularly useful in assessing ambient SO2

concentrations over large populated areas, such as parks and recreation

centers, where people are expected to jog/exercise. The EPA solicits

comments on the location, number and type of SO2 monitors, the

various available monitoring technologies, and the need to waive

minimum monitoring requirements.

The concentration gradients are expected to be sharper around these

targeted sources of SO2 emissions. As a result, the SO2

monitors located to measure population exposures over a wide area are

unlikely to adequately characterize these peaks. Therefore, appendix D

is being revised to allow the use of microscale SO2 sites for

SLAMS monitors, and to encourage middle/neighborhood scale measurements

as appropriate in populated areas near these targeted sources. The

microscale measurements for SO2 would represent concentrations

over an area ranging from several meters to up to about 100 meters. The

EPA solicits comments on the use of micro, middle, and neighborhood

scale monitors, both point monitors and/or open path analyzers, around

point sources of SO2 emissions.

The EPA is also proposing that the SO2 monitors around these

targeted sources of SO2 emissions be classified as SLAMS monitors.

Section 2.3 requires that monitoring be performed for a minimum of 2

years. After that time, a decision should be made during the annual

network review as to whether the monitoring should be continued around

the targeted source, or the monitors redeployed around a different

targeted source based on measured concentration levels, changes in

plant process operations, etc. The EPA solicits comments on the SLAMS

classification of the SO2 monitors around the targeted sources and

a waiver provision to relocate the monitors before the full 2 years

based on a review of the data.

With this proposal, EPA is also requiring the collection of 5-

minute SO2 concentrations at the targeted sites. The EPA solicits

comment on the need to require 5-minute concentrations at NAMS or other

SLAMS sites, and if supplementary criteria should be considered for

this additional request (e.g., require 5-minute SO2 monitor data

if 1-hour concentration exceeds some level).

D. Appendix F--Annual SLAMS Report

A proposed revision to section 2.1.1 of appendix F would reword

this section to provide greater clarity and add a requirement to report

the number of 5-minute hourly maximum observations. Section 2.1.2 would

similarly be reworded for clarity and to require that the 24-hour

averages reported in the annual report for SO2 be based on block

(midnight to midnight) averaging periods and the 3-hour averages also

to be based on block averaging periods. Reporting of the number of

values in specified ranges of 24-hour average concentrations would be

deleted because of new revisions to 40 CFR part 58 data reporting

requirements.

Reporting of 5-minute hourly maximums would also be added. The EPA

solicits comments on the need for reporting additional summary data if

a multiple exceedance form of the standard is adopted.

E. Appendix G--Air Quality Index Reporting and Daily Reporting

The EPA proposes to revise the SO2 ambient concentrations

contained in Tables 1 and 2 and in Figure 3 to correspond to the

proposed new episode criteria and significant harm levels.

VIII. Transition Issues

Since the existing NAAQS would be retained even if a 5-minute NAAQS

is promulgated, all existing requirements and attainment dates will

remain in place as to the existing NAAQS.

IX. Other Clean Air Act Amendment Authorities Affecting SO2

Sources

The EPA is also developing a voluntary program as part of the acid

rain program to encourage nonutility sources to reduce their emissions

of SO2. The voluntary entry into the acid rain program, known as

the opt-in program, allows nonaffected sources (nonaffected under title

IV), the opportunity to receive their own allowances, undertake

emission reductions and trade the extra allowances they would no longer

need for compliance with the acid rain program. Again, such

participating sources would be under the same obligations to meet all

other air regulatory requirements.

These nonutility sources that could participate in the opt-in

program are the same group of sources of concern for establishing a 5-

minute SO2 NAAQS. Assuming entry occurred prior to the imposition

of the 5-minute standard, the source could accelerate its emissions

reductions and offset the cost of such reductions through participation

in the opt-in program. The EPA believes the development of options for

a 5-minute SO2 standard and the opt-in program protects public

health and provides an opportunity for cost reduction.

X. Public Participation

A. Comments and the Public Docket

The EPA welcomes comments on all aspects of this proposed

rulemaking. Commenters are especially encouraged to give suggestions

for changing any aspects of the proposal that they find objectionable.

All comments, with the exception of proprietary information, should be

directed to Docket No. A-94-55 with regard to part 51 and Docket No. A-

94-56 with regard to part 58 (see ADDRESSES).

Commenters who wish to submit proprietary information for

consideration should clearly separate such information from other

comments by: (1) Labeling proprietary information ``Confidential

Business Information,'' and (2) sending proprietary information

directly to the contact person listed (see FOR FURTHER INFORMATION

CONTACT) and not to the public docket.

This will help ensure that proprietary information is not

inadvertently placed in the docket. If a commenter wants EPA to use a

submission labeled as [[Page 12512]] confidential business information

as part of the basis for the final rule, then a nonconfidential version

of the document, which summarizes the key data or information, should

be sent to the docket. Information covered by a claim of

confidentiality will be disclosed by EPA only to the extent allowed and

by the procedures set forth in 40 CFR part 2. If no claim of

confidentiality accompanies the submission when it is received by EPA,

the submission may be made available to the public without notifying

the commenters.

B. Public Hearing

Anyone who wants to present testimony about this proposal at the

public hearing (see DATES) should, if possible, notify the contact

person (see FOR FURTHER INFORMATION CONTACT) at least 7 days prior to

the day of the hearing. The contact person should be given an estimate

of the time required for the presentation of testimony and notification

of any need for audio/visual equipment. A sign-up sheet will be

available at the registration table the morning of the hearing for

scheduling those who have not notified the contact earlier. This

testimony will be scheduled on a first-come, first-serve basis to

follow previously scheduled testimony.

The EPA requests that approximately 50 copies of the statement or

material to be presented be brought to the hearing for distribution to

the audience. In addition, EPA would find it helpful to receive an

advance copy of any statement or material to be presented at the

hearing at least 1 week before the scheduled hearing date. This is to

give EPA staff adequate time to review such material before the

hearing. Such advance copies should be submitted to the contact person

listed.

The official records of the hearing will be kept open for 30 days

following the hearing to allow submission of rebuttal and supplementary

testimony. All such submissions should be directed to Docket No. A-94-

55 with regard to part 51 and Docket No. A-94-56 with regard to part 58

(see ADDRESSES).

Joseph W. Paisie is hereby designated Presiding Officer of the

hearing. The hearing will be conducted informally, and technical rules

of evidence will apply. A written transcript of the hearing will be

placed in the above docket for review. Anyone desiring to purchase a

copy of the transcript should make individual arrangements with the

court reporter recording the proceeding.

XI. Administrative Requirements

A. Regulatory Impact Analysis

Under Executive Order 12866, (58 FR 51735 (October 4, 1993)) the

Agency must determine whether the regulatory action is ``significant''

and therefore subject to the Office of Management and Budget (OMB)

review and the requirements of the Executive Order. The Order defines

``significant regulatory action'' as one that is likely to result in a

rule that may:

(1) Have an annual effect on the economy of $100 million or more or

adversely affect in a material way the economy, a sector of the

economy, productivity, competition, jobs, the environment, public

health or safety, or State, local, or tribal governments or

communities.

(2) Create a serious inconsistency or otherwise interfere with an

action taken or planned by another agency.

(3) Materially alter the budgetary impact of entitlements, grants,

user fees, or loan programs or the rights and obligations of recipients

thereof.

(4) Raise novel legal or policy issues arising out of legal

mandates, the President's priorities , or the principles set forth in

the Executive Order.

Pursuant to the terms of Executive Order 12866, it has been

determined that this rule is a ``significant regulatory action''

because of its potential to have an annual effect on the economy of

$100 million or more as discussed in the related SO2 NAAQS

proposal package on November 15, 1994 (59 FR 58958). As such, this

action was submitted to OMB for review. Changes made in response to OMB

suggestions or recommendations will be documented in the public record.

The EPA has prepared a draft regulatory impact analysis (RIA) based

on information developed by several EPA contractors. It includes

estimates of costs, benefits, and net benefits associated with

alternative SO2 NAAQS. The draft analysis, entitled Regulatory

Impact Analysis of the National Ambient Air Quality Standards for

SO2-Draft, is available from the address given above. The draft

RIA estimates the cost for the short-term SO2 NAAQS regulatory

alternative. The cost estimate for the short-term SO2 NAAQS

alternative represent a snapshot of the estimated total industry costs

that could be incurred at some unspecified time in the future following

full implementation of a short-term SO2 NAAQS. The costs are based

on the use of add-on control devices and fuel switching to lower-sulfur

fuels. Given that EPA believes that many sources will be able to reduce

their peaks through other, nontechnological means, this assumption may

result in overstating costs. With this caveat in mind, nonutility

annualized costs are estimated to be approximately $250 million for an

ambient SO2 concentration for a 0.06 ppm, 5 annual exceedance

concentration levels are estimated to be approximately $160 million. It

is estimated that SO2 will be reduced by approximately 910,000

tons, and 560,000 tons for 1 and 5 exceedance cases, respectively.

Incremental to the title IV requirements and attainment of the existing

SO2 NAAQS, total utility annualized costs in 2005 are estimated to

be an additional $1.5 billion for the 0.06 ppm, 1 expected exceedance

case, and $400 million for the 5 expected exceedance case. Estimated

total utility SO2 emissions in 2005 are not expected to change

given the title IV emissions trading program.

Administrative costs are estimated to be approximately $18 million

for the short-term NAAQS regulatory alternative. Monitoring costs are

estimated to be minimal.

However, EPA has not completed its cost analysis of the section 303

regulatory alternative which EPA believes will be less than the

SO2 NAAQS regulatory alternative. The EPA intends to complete this

analysis and make it available to the public by the end of January

1995. The EPA will announce the availability of this analysis in the

Federal Register as soon as it is available. A final RIA will be issued

at the time of promulgation of final standards. Neither the draft RIA

nor the other contractor reports have been considered in issuing this

proposal.

The regulations, implementation of the revised SO2 NAAQS, the

retained existing NAAQS, and the section 303 program, have been

submitted to OMB for review under Executive Order 12866. Any written

comments from OMB and any EPA responses to those comments are in the

public docket for this rulemaking.

B. Impact on Reporting Requirements

Air quality monitoring activities that would occur as a result of

the SO2 NAAQS proposal could increase the costs and man-hour

burdens to State and local agencies for conducting ambient SO2

surveillance required by 40 CFR part 58 and currently approved under

OMB Control Number 2060-0084. Temporarily-increased costs could result

from the relocation of some monitors currently operated as part of the

SLAMS networks and from the purchase and operation of additional

monitors in a small number of agencies. [[Page 12513]] However, some or

all of these costs could be offset by savings in existing monitoring

networks. As a result, to the extent that additional monitoring costs

will be incurred at all, EPA expects that these costs will be minimal.

The information collection requirements in this proposed rule have

been submitted for approval to OMB under the Paperwork Reduction Act,

44 U.S.C. 3501 et seq. An Information Collection Request document has

been prepared by EPA (ICR No.0940.11) and a copy may be obtained from

Sandy Farmer, Information Policy Branch, EPA, 401 M St., S.W. (Mail

Code 2136), Washington, DC 20460, or by calling (202) 260-2740.

Send comments regarding the burden estimate or any other aspect of

this collection of information, including suggestions for reducing this

burden to Chief, Information Policy Branch, EPA, 401 M St., S.W. (Mail

Code 2136), Washington, DC 20460, and to the Office of Information and

Regulatory Affairs, Office of Management and Budget, Washington, DC

20503, marked ``Attention: Desk Officer for EPA.'' The final rule will

respond to any OMB or public comments on the information collection

requirements contained in this proposal.

C. Impact on Small Entities

Under the Regulatory Flexibility Act, 5 U.S.C., 600 et seq, the

Agency must prepare a regulatory flexibility analysis assessing the

impact of any proposed or final rule on small entities. Under 5 U.S.C.

605(b), this requirement may be waived if the Agency certifies that the

rule will not have a significant economic effect on a substantial

number of small entities. Small entities include small businesses,

small not-for-profit enterprises, and governmental entities with

jurisdiction over populations of less than 50,000.

A decision to revise the current NAAQS for SO2 or set a

trigger level for implementation of a section 303 program would impose

no new major requirements. It is expected that following the

promulgation of a revised SO2 NAAQS, additional nonattainment

areas will be designated and will thus have to submit SIP revisions

imposing additional control requirements on affected sources.

Furthermore, the control measures necessary to attain and maintain

the NAAQS or implement a section 303 program are developed by the

respective States as part of their SIP's. In selecting such measures,

the States have considerable discretion so long as the mix of controls

selected is adequate to attain and maintain the NAAQS or not exceed the

section 303 trigger level. Whether a particular NAAQS would have a

significant effect on a substantial number of small entities,

therefore, depends on how the States would choose to implement it. For

these reasons, any assessment performed by EPA on the costs of

additional SIP requirements at this time would necessarily be

speculative. On the basis of the above considerations and findings, and

as required by section 605 of the Regulatory Flexibility Act, 5 U.S.C.

601 et seq., the Administrator certifies that this regulation does not

have a significant impact on a substantial number of small entities.

D. Reduction of Governmental Burden

Executive Order 12875 (``Enhancing the Intergovernmental

Partnership'') is designed to reduce the burden to State, local, and

tribal governments of the cumulative effect of unfunded Federal

mandates. The Order recognizes the need for these entities to be free

from unnecessary Federal regulation to enhance their ability to address

problems they face and provides for Federal agencies to grant waivers

to these entities from discretionary Federal requirements. The Order

applies to any regulation that is not required by statute and that

creates a mandate upon a State, local, or tribal government. The EPA is

required by statute to review periodically and, as necessary, revise

the national ambient air quality standards, and to call on States to

develop plans to attain and maintain these standards. However, this

action also includes a request for comment on the adoption of a section

303 program, as well as a proposal to establish a targeted monitoring

network, neither of these actions is explicitly mandated by statute.

Therefore, in accordance with the purposes of Executive Order 12875,

EPA will consult with representatives of State, local, and tribal

governments to inform them of the requirements for implementing the

alternative regulatory measures being proposed to address short-term

peak SO2 exposures. The EPA will summarize the concerns of the

governmental entities and respond to their comments prior to taking

final action.

The EPA anticipates that there will be no additional cost burden

imposed on States in order to implement the monitoring requirements

proposed in this notice. In general, costs incurred for relocating

monitors will be offset by operating costs saved from discontinuing

SLAMS and NAMS monitors. For more detail the reader is referred to the

section on resource concerns for relocating monitors under the targeted

implementation strategy section discussed earlier in this notice or to

the supporting statement for the information collection request.

E. Environmental Justice

Executive Order 12898 requires that each Federal agency shall make

achieving environmental justice part of its mission by identifying and

addressing, as appropriate, disproportionately high and adverse human

health or environmental effects of its programs, policies, and

activities on minority and low-income populations. The requirements of

Executive Order 12898 have been addressed in the draft RIA cited above.

On average, approximately 25 percent of the total population and 14

percent of total households residing in geographic areas that are

potentially impacted by short-term SO2 peaks of 0.60 ppm or

greater are nonwhite and below the poverty level, respectively. These

estimates exceed the national averages of 19.7 percent and 12.7

percent, respectively. It also follows that, on average, 25 percent of

the asthmatics potentially exposed to short-term SO2 peaks of 0.60

ppm or greater are nonwhite. Upon closer examination, 44 percent of

these potentially SO2-impacted areas have a nonwhite population

greater than the national average with 24 percent between 1 and 2 times

greater, 10 percent between 2 and 3 times greater, 7 percent between 3

and 4 times greater, and 3 percent between 4 and 5 times greater.

Appendix A--References

Bennett, K.M. (1982), US EPA, Assistant Administrator for Air, Noise

and Radiation, Policy on Excess Emissions During Startup, Shutdown,

Maintenance, and Malfunctions, Memorandum to Regional

Administrators, Regions I-X, September 28, 1982.

Burton, C.S.; Stoeckenius, T.E.; Stocking, T.S.; Carr, E.L.; Austin,

B.S.; Roberson, R.L. (1987), Assessment of exposures of exercising

asthmatics to short-term SO2 levels as a result of emissions

from U.S. fossil-fueled power plant, Systems Applications, Inc., San

Rafael, CA., Pub. No. 87/176, September 23, 1987.

Calcagni, J. (1992), Director of Air Quality Management Division,

Processing of State Implementation Plan (SIP) Submittals, Memorandum

to Air Division Directors, Regions I-X, July 9, 1992.

EPA (1982a), Review of the National Ambient Air Quality Standards

for Sulfur Oxides: Assessment of Scientific and Technical

Information-OAQPS Staff Paper, Office of Air Quality Planning and

Standards, Research Triangle Park, NC, EPA-450/5-82-007.

[[Page 12514]]

EPA (1986a), Second Addendum to Air Quality Criteria for Particulate

Matter and Sulfur Oxides (1982): Assessment of Newly Available

Health Effects Information, Environmental Criteria and Assessment

Office, Research Triangle Park, NC, EPA-450/5-86-012.

EPA (1986b), Review of the National Ambient Air Quality Standards

for Sulfur Oxides: Updated Assessment of Scientific and Technical

Information, Addendum to the 1982 OAQPS Staff Paper, Office of Air

Quality Planning and Standards, Research Triangle Park, NC, EPA-450/

05-86-013.

EPA (1986c), Guideline on Air Quality Models (Revised), Office of

Air Quality Planning and Standards, Research Triangle Park, NC, EPA-

450/2-78-027R. (Codified in 40 CFR 51, appendix W.)

EPA (1992a), National Air Pollutant Emission Estimates, 1900-1991,

Office of Air Quality Planning and Standards, Research Triangle

Park, NC, EPA-454/R-92-013.

EPA (1992b), National Air Quality and Emissions Trends Report, 1991,

Office of Air Quality Planning and Standards, Research Triangle

Park, NC, EPA/450-R-92-001.

EPA (1992c), General Preamble for the Implementation of Title I of

the Clean Air Act Amendments of 1990, April 16, 1992, 57 FR 13498.

EPA (1994b), Review of the Ambient Air Qua

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