[Federal Register Volume 62, Number 1 (Thursday, January 2, 1997)]
[Proposed Rules]
[Pages 210-222]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 96-32978]



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Part IV





Environmental Protection Agency





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40 CFR Part 51



Proposed Implementation Requirements for Reduction of Sulfur Oxide 
(Sulfur Dioxide) Emissions; Proposed Rule

  Federal Register / Vol. 62, No. 1 / Thursday, January 2, 1997 / 
Proposed Rules  

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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 51

[AD-FRL-5670-8]
RIN 2060-AA61


Proposed Implementation Requirements for Reduction of Sulfur 
Oxide (Sulfur Dioxide) Emissions

AGENCY: Environmental Protection Agency (EPA).

ACTION: Proposed rule.

-----------------------------------------------------------------------

SUMMARY: The EPA is proposing a new intervention level program under 
the authority of sections 301(a)(1) and 303 of the Clean Air Act (Act) 
to supplement protection provided by the primary and secondary sulfur 
dioxide (SO2) national ambient air quality standards (NAAQS). The 
program proposed today is in lieu of the three alternative 
implementation strategies for reducing high 5-minute SO2 
concentrations in the ambient air proposed on March 7, 1995.
    The intervention level program addresses EPA's concern 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). At certain 
concentration levels or frequencies, such peaks can represent imminent 
and substantial endangerment to public health. This proposed program 
also responds to comments received on the March 7, 1995 proposal.
    In addition, EPA is reproposing the implementation strategy for 
identifying and prioritizing areas with potential 5-minute SO2 
peaks. The changes to the monitoring strategy discussed in the March 7, 
1995 proposal address public comments regarding the flexibility of the 
strategy and the criteria used to identify sources for monitoring.
    Finally, EPA has reviewed comments concerning the revisions to the 
24-hour significant harm levels (SHL) for SO2 discussed in the 
March 7, 1995 proposal. After further consideration, the EPA now 
believes the proposed revisions to those levels are not needed at this 
time. The EPA is requesting comment on whether the proposed changes to 
the SHL are necessary or should be withdrawn.

DATES: Written comments on this proposal must be received by March 3, 
1997. Persons wishing to present oral testimony pertaining to this 
notice should contact EPA at the address listed below under FOR FURTHER 
INFORMATION CONTACT by January 17, 1997. If anyone contacts EPA 
requesting to speak at a public hearing, a separate notice will be 
published announcing the date, time, and place where the hearing will 
be held.

ADDRESSES: Submit comments on this proposal (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, 401 M Street, SW, 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 the availability of related 
information, see SUPPLEMENTARY INFORMATION.

FOR FURTHER INFORMATION CONTACT: Eric L. Crump, Integrated Policies and 
Strategies Group (MD-15), U.S. Environmental Protection Agency, 
Research Triangle Park, NC 27711, telephone (919) 541-4719.

SUPPLEMENTARY INFORMATION:

Regulated Entities

    Entities potentially regulated by this action are those which 
contribute to 5-minute ambient SO2 concentrations that pose a 
health threat to sensitive, exposed populations. Regulated categories 
and entities would include:

------------------------------------------------------------------------
           Category                  Examples of regulated entities     
------------------------------------------------------------------------
Industry.....................  Pulp and paper mills, lead, aluminum, and
                                copper smelters, petroleum refineries,  
                                iron and steel mills, carbon black      
                                manufacturers, portland cement plants,  
                                oil and gas extraction processes,       
                                fertilizer manufacturers, industrial and
                                utility boilers, sulfuric acid plants.  
Federal government...........  Federal agencies which operate industrial
                                or utility boilers.                     
State/tribal government......  State/tribal agencies which operate      
                                industrial or utility boilers.          
------------------------------------------------------------------------

    This table is not intended to be exhaustive; furthermore, entities 
listed in this table would not necessarily be subject to regulation 
under this proposed action. This table is intended only as a guide for 
readers regarding entities likely to be regulated by this action. This 
table lists the types of entities that EPA believes could potentially 
be regulated by this action. Other types of entities not listed in the 
table could also be regulated. To determine whether your facility, 
company, business or organization would be regulated by this proposed 
action, you should ascertain whether your facility, company, business, 
or organization (1) emits SO2, and (2) is located in an area 
subject to ambient air concentrations that exceed the criteria in 
Sec. 51.154 of 40 CFR. If you have questions regarding the 
applicability of this action to a particular entity, consult the person 
listed in the preceding FOR FURTHER INFORMATION CONTACT section.

Availability of Related Information.

    The 1982 revised criteria document, Air Quality Criteria for 
Particulate Matter and Sulfur Oxides (three volumes, EPA-600/8-82-
029af-cf, December 1982; Volume I, NTIS # PB-84-120401, $36.50 paper 
copy and $9.00 microfiche; Volume II, NTIS # PB-84-120419, $77.00 paper 
copy and $9.00 microfiche; Volume III, NTIS # PB-84-120427, $77.00 
paper copy and $20.50 microfiche); the 1986 criteria document addendum, 
Second Addendum to Air Quality Criteria for Particulate Matter and 
Sulfur Oxides (1982): Assessment of Newly Available Health Effects 
Information (EPA/600/8-86-020-F, NTIS # PB-87-176574, $36.50 paper copy 
and $9.00 microfiche); the 1994 criteria document supplement, 
Supplement to the Second Addendum (1986) to Air Quality Criteria for 
Particulate Matter and Sulfur Oxides (1982): Assessment of New Findings 
on Sulfur Dioxide Acute Exposure Health Effects in Asthmatic 
Individuals (1994) (EPA-600/FP-93/002); the 1982 staff paper, Review of 
the National Ambient Air Quality Standards for Sulfur Oxides: 
Assessment of Scientific and Technical Information (EPA-450/5-82-007, 
November 1982; NTIS # PB-84-102920, $36.50 paper copy and $9.00 
microfiche); the 1986 staff paper addendum, Review of the National 
Ambient Air Quality Standards for Sulfur Oxides: Updated Assessment of 
Scientific and Technical Information (EPA-450/05-86-013, December 1986; 
NTIS # PB-87-200259, $19.50 paper copy and $9.00 microfiche) and the 
1994 staff paper supplement, Review of the National Ambient Air Quality

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Standards For Sulfur Oxides: Updated Assessment of Scientific and 
Technical Information, Supplement to the 1986 OAQPS Staff Paper 
Addendum (1994) (EPA-452/R-94-013, September 1994; NTIS # PB-95-124160, 
$27.00 paper copy and $12.50 microfiche) are available from: U.S. 
Department of Commerce, National Technical Information Service, 5285 
Port Royal Road, Springfield, Virginia 22161, or call 1-800-553-NTIS. 
(Add $3.00 handling charge per order.)

Table of Contents

I. Background
    A. Overview
    B. Rulemaking Docket
II. Intervention Level Program
    A. Program Highlights
    B. Health Effects and Basis for Levels
    C. Flexible Implementation Strategy
III. Legal Authority
IV. Program Implementation
    A. Requirements Associated with the Implementation of the 
Intervention Level Program
    B. Compliance and Enforcement Issues
V. Relationship Between the Intervention Level Program and Existing 
Programs
    A. Impact on SIPs, Attainment Planning and Implementation
    B. Malfunctions
    C. Significant Harm Level Program
    D. Acid Rain Program
VI. Community Involvement in the Intervention Level Program
VII. Source Prioritization and Monitor Allocation
VIII. Reconsideration of Proposed 24-Hour Significant Harm Level and 
Episodes Criteria
IX. Comments and the Public Docket
X. Administrative Requirements
    A. Executive Order 12866
    B. Monitoring and Administrative Costs
    C. Regulatory Flexibility Analysis
    D. Impact on Reporting Requirements
    E. Unfunded Mandates Reform Act
    F. Environmental Justice
References

SUPPLEMENTARY INFORMATION:

I. Background

A. Overview

    As discussed in the November 15, 1994 proposal (59 FR 58958), EPA 
completed a thorough review of the air quality criteria and the current 
SO2 NAAQS required by sections 108 and 109 of the Act and 
concluded provisionally that the current 24-hour and annual primary 
standards provide adequate protection against the effects associated 
with those averaging periods. 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 explained in the March 7, 1995 Federal Register proposal (60 FR 
12492), the available air quality and exposure data indicate that the 
likelihood that the asthmatic population in general 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 with some frequency, and as a result, asthmatic 
individuals in the vicinity of such sources would be subject to a 
greater health risk than asthmatics not subject to such peaks or the 
nonasthmatic population. These assessments lead EPA to believe that if 
any additional regulatory measures are adopted to provide additional 
protection, they should be addressed through an approach that focuses 
on those locations where the sensitive population is more likely to be 
exposed to high 5-minute peak SO2 concentrations.
    Based on these considerations, EPA requested comment on three 
regulatory measures proposed on March 7, 1995 to address high 5-minute 
SO2 peaks: (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) supplementing the existing 
NAAQS with a 5-minute NAAQS of 0.60 parts per million (ppm).
    The public comments received represented various concerns regarding 
the three alternatives. Of the many comments received, the following 
arguments appeared to be most compelling: (1) short-term peak emissions 
are more of a localized issue rather than a widespread concern and that 
instead of a broad national regulatory program, States and tribes 
should be given the authority to address such issues; and (2) States 
and tribes need more flexibility to address situations that create 
exposures to high short-term ambient concentrations, especially in 
cases when the short-term peaks are rare and the potential for exposure 
is low (for example, when the source is located in a relatively 
isolated area). The comments received confirm EPA's original assessment 
that high 5-minute peak episodes of SO2 are not a uniformly 
widespread problem; rather, these episodes are limited to certain 
localized areas throughout the country. The EPA now believes that a 
national regulatory program developed for implementation by every State 
and tribe would be counterproductive, placing an administrative burden 
on many parts of the country that are not subject to risk from these 
peak concentrations.
    Although these episodes are few, it is clear that 5-minute SO2 
ambient concentration peaks pose a health threat to sensitive, exposed 
populations, and that the severity of the threat depends upon the 
concentration and frequency of peak episodes and the size of the 
population subject to the peak episodes. Because every area that is 
subject to significant short-term peaks has its own unique 
characteristics, EPA agrees it is prudent for States, local 
governments, and tribal governments to assess each individual 
situation, and if a significant threat to public health exists, act 
appropriately and efficiently to reduce the risk to the public. The EPA 
wishes to establish an implementation program that (1) effectively 
addresses real health concerns, (2) provides States, tribes, and local 
communities with a basis for taking protective action, and (3) provides 
flexibility to address a given situation appropriately.
    For the reasons discussed in the May 22, 1996 Federal Register 
final decision (61 FR 25566), EPA has concluded that revisions to the 
existing SO2 NAAQS are not appropriate at this time. In lieu of 
the three alternative approaches originally proposed to address 5-
minute concentrations, EPA now proposes an intervention level program 
under the authority of section 303 of the Act to address the risk 
presented by 5-minute SO2 concentrations.
    Because health effects caused by 5-minute SO2 ambient 
concentrations tend to be localized problems, EPA believes the 
intervention level program is the appropriate approach to address this 
concern. Instead of a uniform nationwide approach that might call for 
unnecessary administrative effort, this program would allow placement 
of resources and efforts precisely where the problems are. It would 
allow States, tribes, and local governments to analyze the variable 
issues relevant to peak concentration episodes in their jurisdiction, 
giving them the flexibility to address the sources of the peak 
emissions more efficiently and appropriately. The intervention level 
program would also provide a catalyst for community-based approaches to 
environmental protection by encouraging States and tribes to 
incorporate citizen concerns and complaints into their criteria for 
assessing public health risk.

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B. Rulemaking Docket

    Docket No. A-94-55 has been established for supporting 
documentation for the action proposed today. The EPA established a 
standard review docket (Docket No. A-79-28) for the sulfur oxides 
review in July 1979. The EPA also established a rulemaking docket 
(Docket No. A-84-25) for the April 26, 1988 proposal under section 
307(d) of the Act. Docket No. A-84-25 was used for the most current 
review of the SO2 NAAQS. Both of these dockets, as well as a 
separate docket established for criteria document revision (Docket No. 
ECAO-CD-79-1), are hereby incorporated into the rulemaking docket for 
the action proposed today.

II. Intervention Level Program

A. Program Highlights

    The proposed intervention level program is derived in part from the 
SHL program, which has served in the past as a means for implementing 
the authority granted under section 303 of the Act. The SHL program was 
designed to address emergency episodes that occur where pollution 
levels build up over a period of time to unhealthy levels. The SHL 
program establishes a specific pollutant concentration within a given 
time period that is known to pose a significant threat to human health 
and that would require specific measures on the part of the State or 
tribe and emission sources to correct. In addition, the program 
establishes several degrees or levels of response which are triggered 
by pollutant concentrations below the SHL. As the concentration of a 
pollutant rises to each level, emission sources in the area are 
required to take increasingly restrictive action to reduce emissions as 
specified in the contingency plan within an approved State 
implementation plan (SIP). The SHL program is a proactive program 
designed to prevent an area from ever reaching the SHL.
    The EPA contemplated using a similar approach to address 5-minute 
peak emissions of SO2, but believes the SHL program would not be 
the best means for addressing such short term peak episodes. A 5-minute 
ambient concentration peak encompasses a short period of time compared 
to the 3-hour and 24-hour periods used in the SHL program. The EPA 
believes it is impractical to expect industry, States, and tribes to 
have a predetermined course of corrective action in place to stop 5-
minute peak episodes as they occur because 5-minute episodes would 
generally be over before remedial action could be taken to stop them. 
In the view of the Administrator, this situation calls for a more 
reactive approach as opposed to the proactive approach called for in 
the SHL program. The EPA believes that its authority under sections 
301(a)(1) and 303 of the Act provides for the creation of a new program 
to address these short term peaks of SO2--the intervention level 
program.
    The intervention level program proposed herein would be similar to 
the SHL program in that it would establish concentration levels in the 
CFR that provide a basis for action by States, tribes and industry if 
those levels are reached. As a supplement to the four concentration 
levels specified in the SHL program, EPA proposes a range of 
concentrations under the intervention level program. The lower boundary 
of this range would be the concern level, set at 0.60 ppm of SO2, 
based on a 5-minute hourly maximum value (a 5-minute hourly maximum 
value for SO2 is the highest of the 5-minute averages from the 12 
possible nonoverlapping periods during a clock hour). The upper 
boundary of this range would be the endangerment level, set at 2.0 ppm 
of SO2, based on a 5-minute hourly maximum value. These 
intervention levels are based on the health criteria discussed below 
and in the May 22, 1996 part 50 final action (61 FR 25566), and would 
be used by States and tribes along with other factors to determine 
whether occurrences of 5-minute SO2 concentrations require action 
to address ``* * * imminent and substantial endangerment to public 
health or welfare, or the environment * * *'', as stated in section 303 
of the Act.
    In the event that the concern level concentration is exceeded in a 
given area, and the State or tribe has reason to believe that the 
exceedance may constitute imminent and substantial endangerment, the 
State or tribe would assess the situation to determine whether 
intervention is appropriate. In making this determination, the State or 
tribe would consider the magnitude of the 5-minute peak concentrations; 
the frequency of the episodes (based on those episodes detected by 
monitors and an estimate of the number of 5-minute peaks not recorded 
by the monitoring network); the history and nature of citizen 
complaints; available information on potential population exposure, 
inferred in part by the population in the vicinity of the source; 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 
another); the history of past upsets or malfunctions; the type of fuel 
used; knowledge of how well the source is controlled; and any other 
considerations the State or tribe finds to be appropriate. Because the 
health effects become more severe as the 5-minute SO2 
concentration approaches the endangerment level, it is reasonable to 
expect that the State or tribe would be more likely to determine that 
intervention is warranted, and that the degree of intervention judged 
to be necessary would increase. If the endangerment level is exceeded, 
thereby exposing a significant population to imminent and substantial 
endangerment, the State or tribe may consider taking immediate action 
to protect public health. Even in cases when the endangerment level is 
exceeded, it is conceivable that the State or tribe may determine that 
no action is warranted. For example, if the exceedance is linked to an 
unusual circumstance not likely to reoccur, or causes minimal impact on 
public health, the State or tribe may conclude that corrective measures 
are not needed at this time.
    In general the State or tribe will assess the health risk and 
implement corrective measures under the intervention level program, not 
EPA. If necessary, EPA would take action under the authority of section 
303, as appropriate, in the event that the State or tribe fails to 
address (1) imminent and substantial endangerment to public health 
presented by exceedances of the endangerment level, or (2) evidence 
that exceedances above the concern level (but below the endangerment 
level) cause imminent and substantial endangerment due to their 
frequency, magnitude, and reported health impacts.

B. Health Effects and Basis for Levels

    The health effects associated with exposures to the concern level, 
0.60 ppm SO2, 5-minute block average, were the focus of EPA's most 
recent review of the primary NAAQS for sulfur oxides (measured as 
sulfur dioxide). The health effects and the Administrator's conclusions 
about the public health risks associated with exposure to the concern 
level are thoroughly discussed in the EPA documents generated during 
that review: the criteria document supplement (EPA, 1994a), the staff 
paper supplement (EPA 1994b), the November 15, 1994 proposal (59 FR 
58958) and the May 22, 1996 final decision on part 50 (61 FR 25566). 
These documents are incorporated into today's proposal by reference.
    The EPA's concern about the potential public health consequences of 
exposures to short-term peaks of SO2 arose from the extensive 
literature involving brief (2- to 10-min) controlled exposures of 
persons with mild (and, in some cases moderate) asthma across the

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ranges of concentrations of SO2 to greater than 2.0 ppm while at 
elevated ventilation rates. The major effect of SO2 on sensitive 
asthmatic individuals is bronchoconstriction, usually evidenced in 
these studies by decreased lung function (i.e., decreased forced 
expiratory volume in 1 second (FEV1) and increased specific airway 
resistance (SRaw)) and the occurrence of clinical symptoms such as 
wheezing, chest tightness, and shortness of breath. The proportion of 
asthmatic individuals who respond, the magnitude of the response and 
the occurrence of symptoms increase as SO2 concentrations and 
ventilation rates increase. The criteria document supplement (EPA, 
1994a) contains a summary of the literature on the health effects 
associated with brief exposures to SO2.
    Taking into account the available health effects studies and the 
body of comments on the health effects, the Administrator concluded in 
the May 22, 1996 final decision (61 FR 25566) that a substantial 
percentage (20 percent or more) of mild-to-moderate asthmatic 
individuals exposed to 0.60 to 1.0 ppm SO2 for 5 to 10 minutes at 
elevated ventilation rates, such as would be expected during moderate 
exercise, would be expected to have lung function changes and severity 
of respiratory symptoms that clearly exceed those experienced from 
typical daily variation in lung function or in response to other 
stimuli (e.g., moderate exercise or cold/dry air). The 
bronchoconstriction caused by brief exposures to 0.6 to 1.0 ppm 
SO2 is transient (i.e., measurements of lung function start to 
improve when exposure ceases or when the individual ceases to exercise 
and ventilation rates return to resting levels). However, for many 
responders, the effects are likely to be both perceptible and thought 
to be of some health concern; that is, likely to cause some disruption 
of ongoing activities, use of bronchodilator medication, and/or 
possibly seeking of medical attention.
    During the regulatory review process, there was some agreement by 
medical experts that at this concentration, 0.60 ppm SO2, the 
frequency with which such effects are experienced may affect the degree 
of public health risk. After taking into account the broad range of 
opinions expressed by Clean Air Scientific Advisory Committee (CASAC) 
members, medical experts, and the public in the part 50 final decision, 
the Administrator concluded that repeated occurrences of such effects 
should be regarded as significant from a public health standpoint. 
Furthermore, the Administrator determined that the likely frequency of 
occurrence of such effects should be a consideration in assessing the 
overall public health risk in a given situation.
    The available scientific literature indicates that in the range of 
0.60 to 2.0 ppm SO2, there is a dose-response relationship between 
SO2 concentration and (1) the magnitude of the lung function 
changes, and (2) the proportion of the asthmatic individuals expected 
to respond. At 1.0 ppm SO2, 5-minute block average, approximately 
60 percent of the mild-to-moderate asthmatic individuals at elevated 
ventilation rates are likely to respond. The health effects become more 
pronounced, with more substantial changes in pulmonary function 
accompanied by symptoms. Asthmatic individuals may experience mild 
bronchoconstriction without symptoms while at rest (EPA, 1986a; EPA, 
1986b).
    At 2.0 ppm SO2, 5-minute block average, approximately 80 
percent of mild-to-moderate asthmatic individuals at elevated 
ventilation rates are likely to respond. Effects can range from 
moderate to incapacitating. Asthmatic individuals at rest are likely to 
experience moderate bronchoconstriction. A moderate episode of 
bronchoconstriction can increase the lung function index SRaw by 
100 to 200 percent, with a severe response being an SRaw increase 
of > 200 percent, and incapacitating bronchoconstriction entails 
SRaw increases much greater than 300 percent (EPA, 1994a). 
Horstman et al. (1986) report that 12 (of 27) subjects in the Roger et 
al. (1985) study, whose SRaw values did not increase by 100 
percent at 1.0 ppm SO2 or lower levels, were also exposed to 2.0 
ppm using the same protocol. At this level, seven of these less 
sensitive asthmatic individuals had SRaw increases of from 100 to 
over 600 percent. For a more detailed discussion of the studies which 
support this assessment, see the 1986 criteria document addendum (Table 
7; EPA, 1986a), and section IIB of the 1986 staff paper addendum (EPA, 
1986b).
    At 3.0 to 5.0 ppm SO2, nonasthmatic adults at mild exercise 
will experience bronchoconstriction, and asthmatic individuals at rest 
will likely experience pronounced bronchoconstriction. For a more 
detailed discussion of the health effects of exposure to these higher 
concentrations of SO2, see the 1982 criteria document (EPA, 1982a) 
and the 1982 staff paper (EPA, 1982b). Based upon this information, EPA 
believes that exposure of a sensitive population to a 5-minute ambient 
concentration of 2.0 ppm or above would pose an imminent and 
substantial endangerment to public health and welfare and, therefore, 
would justify corrective action under the authority of section 303.

C. Flexible Implementation Strategy

    Like the previously proposed implementation alternatives, a key 
element of this new implementation strategy is the relocation of 
existing SO2 monitors to areas near point sources where peak 
SO2 concentrations may exist. Because the monitors in the existing 
State and local area monitoring stations (SLAMS) network were designed 
to characterize urban ambient air quality associated with 3-hour, 24-
hour, and annual SO2 concentrations, they are not always the 
appropriate means for measuring 5-minute peak SO2 concentrations 
from point sources. To make existing monitors available for the 
measurement of short-term peak concentrations, EPA proposed certain 
technical changes to the requirements for ambient air monitoring 
reference and equivalent methods (40 CFR part 53) and revisions to the 
ambient air quality surveillance requirements (40 CFR part 58) in the 
November 15, 1994 (59 FR 58958) and the March 7, 1995 (60 FR 12492) 
proposals, respectively.
    The EPA believes these changes to the monitoring requirements will 
give the States and tribes the flexibility to relocate existing 
monitors to areas where 5-minute peak concentrations may be of concern, 
and to respan the monitors to measure these peaks. Under the 
intervention level program, the States and tribes would be able to 
identify areas to be monitored based on State or tribal priorities, 
source emissions, citizen complaints, location of sensitive 
populations, or other variables. Upon request, EPA would assist State 
and tribal efforts to identify and prioritize areas for monitoring 5-
minute peak concentrations by providing information compiled from 
various databases. The EPA would leave the discretion on how best to 
utilize this information in siting monitors to the States and tribes. 
If the State or tribe has ample reason to believe that areas within its 
jurisdiction do not experience health risks from 5-minute peak 
concentrations (for example, no sources with significant compliance 
issues, maintenance problems or upsets; no complaints about detrimental 
health effects from short-term peak SO2 concentrations), the State 
or tribe would be justified in not relocating SO2 monitors for 
this purpose.

III. Legal Authority

    In the November 15, 1994 Federal Register action (59 FR 58958), EPA

[[Page 214]]

discussed the legal authority for a proposed regulatory program under 
the authority of sections 110(a)(2)(G), 301, and 303 of the Act. The 
March 7, 1995 proposal (60 FR 12492) described this program in greater 
detail. Although the intervention level program proposed herein differs 
from the section 303 program described in these actions, the basic 
objective and the legal authority to establish it remain the same. 
Consequently, the EPA continues to rely on the legal authority 
discussion regarding sections 301 and 303 contained in the November 15, 
1994 proposal and hereby incorporates that discussion by reference (59 
FR 58970-71).
    In addition, the EPA believes that in some cases the potential 
health effects that may result from a 5-minute peak SO2 
concentration above the concern level of 0.60 ppm could be an indicator 
of substantial endangerment to public health and welfare, depending on 
the frequency and magnitude of the ambient peak concentrations and the 
likelihood that asthmatic individuals will experience exposures of 
concern. For example, concentrations above the concern level may 
present an unacceptable risk of harm to asthmatic individuals who have 
not premedicated with beta-agonist bronchodilators and are exposed at 
elevated ventilation. Action under the authority of section 114 to 
investigate the cause and potential effect of ambient concentrations 
above the concern level, followed by corrective action under the 
authority of section 303, might therefore be warranted in some cases. 
Furthermore, EPA believes that exposure of a sensitive population to a 
5-minute ambient concentration of 2.0 ppm or above would pose an 
imminent and substantial endangerment to public health and welfare and, 
therefore, would justify corrective action under the authority of 
section 303.
    Unlike the section 303 program EPA proposed on March 7, 1995, the 
intervention level program proposed today would not require States and 
tribes to submit revised contingency plans to EPA requiring specific 
actions for the State, tribe, and source to undertake once an 
established ambient SO2 concentration is violated. The EPA 
believes that the approved SIP's currently in force provide the States 
with adequate general authorities to implement the intervention level 
program without submittal of revised contingency plans for approval by 
EPA. Section 110(a)(2)(G) of the Act requires that the SIP contingency 
plans contain adequate authority to implement section 303 programs. 
Furthermore, the SIP's contain general enforcement authority that 
allows States to request information and conduct inspections--in short, 
to gather the necessary data to determine the appropriate course of 
action in the event that 5-minute SO2 peaks pose a threat to human 
health. Finally, many SIP's contain general prohibitions against air 
pollution which provide the States broad discretion to address source-
specific problems. The EPA also believes that once the tribal rule 
proposed on August 25, 1994 (59 FR 43956) becomes final, tribal 
implementation plans (TIP's) will provide tribes with similar 
authority.
    The EPA believes the general authority possessed by States and 
tribes to implement the intervention level program under section 303 is 
an advantage. By eliminating the need for States and tribes to revise 
their contingency plans, as well as the need for an extensive review 
and approval process, the intervention level program should minimize 
the potential administrative burden on the States and tribes. If a 
particular State SIP or tribal TIP does not contain adequate authority 
to implement the intervention level program, EPA expects the State/
tribe to revise its SIP/TIP accordingly to provide the necessary 
authority. In the event that the State/tribe does not take prompt 
action to revise its SIP/TIP, EPA would issue a SIP/TIP call for the 
State/tribe. The EPA interprets sections 110(a)(2)(G) and 303 of the 
Act, along with section 301 (which grants general authority to 
prescribe regulations necessary to carry out the functions of the 
Administrator), as providing adequate legal authority to establish this 
program and to promulgate the necessary regulations to implement it.

IV. Program Implementation

A. Requirements Associated with Implementation of the Intervention 
Level Program

    As stated earlier, EPA's intent in proposing the intervention level 
program is that the States and tribes would be given the flexibility to 
address particular sources of 5-minute SO2 peak concentrations in 
the most efficient and appropriate manner, based on an area-specific 
analysis of the particular characteristics of peak ambient 
concentration episodes in their jurisdictions. The following discussion 
is intended as a guide for implementing the intervention level program 
and is not meant to be prescriptive.
    The EPA believes that when the concern level of 0.60 ppm has been 
exceeded in a given area, the State or tribe should consider whether or 
not the situation presents a significant public health risk. If the 
number of exceedances per year are few in number, or linked to rare 
incidents, the State or tribe may determine that no further action is 
warranted unless the frequency or severity of the exceedances 
increases. If the concern level is exceeded on a more regular basis, or 
to a more severe degree, the State or tribe should conduct a more 
detailed analysis. The analysis could include elements such as 
identification of the sources that contribute most to the peak ambient 
concentrations, the number of observed and projected exceedances, the 
magnitude of the exceedances, the nature and location of the sources, 
the proximity of the sources to sensitive populations, and other 
pertinent factors needed to characterize the risk to public health. The 
State or tribe may choose to follow up the analysis with a compliance 
inspection of the sources that contribute to the peak ambient 
concentrations. If the magnitude of the peak concentrations is 
significantly higher than the concern level of 0.60 ppm (but still less 
than the endangerment level of 2.0 ppm), the State or tribe may choose 
to conduct a compliance inspection after only one exceedance. If any of 
the sources under consideration are out of compliance with their 
existing emission limits (based on the NAAQS or other air pollution 
requirements), then the State or tribe would take the necessary steps 
to bring the sources into compliance. If, however, the State or tribe 
determines a substantial threat to public health exists, but (1) finds 
it unlikely that bringing sources into compliance with their existing 
emission limits would prevent further exceedances of the concern level, 
or (2) determines the source to be in compliance with applicable 
emission limits, then further action in addition to assuring compliance 
may be needed. In such circumstances, the next step would be for the 
State, tribe and source to examine the sources of the peak 
concentrations. Once that is determined, an appropriate approach to 
address the high peak concentrations would need to be developed.
    Under the intervention level program, EPA would not specify a time 
limit in which States, tribes and sources must take corrective action 
(whether it be control devices, process or operational modifications, 
or other selected protective approach). However, EPA expects that 
development and implementation of any course of corrective action for a 
given situation would occur expeditiously and efficiently, based on the 
risk to public

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health; the specific processes or operations at the source that cause 
the peak episodes; the available options for addressing the public 
health risk; the reasonable lead time necessary to plan, design, 
procure and install control devices and process modifications, or to 
implement alternative approaches to control; and other pertinent 
considerations. Implementation need not wait until the process of 
incorporating the selected course of action into the SIP/TIP, permit, 
or other enforceable agreement is complete. Once the approach for 
addressing the public health risk has been determined, the State/tribe 
should issue a section 303 order to the source to expedite 
implementation of the selected action.
    In determining the course of corrective action, States, tribes, and 
sources should keep in mind that the goal of the intervention level 
program is to prevent imminent and substantial endangerment to public 
health caused by short-term peak ambient concentrations. Control 
measures to prevent recurrences of 5-minute SO2 peaks may include 
better maintenance of control equipment, better capture of fugitive 
emissions, raising the stack height (refer to section A under 
Relationship between the Intervention Level Program and Existing 
Programs), restriction of operations during times of peak exposure 
(e.g., conducting activities during hours when fewer people are 
outside), or other innovative courses of action. In some cases (e.g., 
areas where the risk is minimal due to low population density or where 
infrequent 5-minute peaks occur), after consultation with sources and 
the affected communities, the State or tribe may determine that control 
measures may not be the most appropriate means for reducing the risk to 
the public. In such cases, States or tribes, in consultation with 
sources and the impacted communities, may elect to address the health 
risk through alternative approaches. Examples of alternative approaches 
that States, sources, and communities might select are: public 
education campaigns for asthma prevention, public warning/notice of 
potential health problems due to peak episodes (e.g., a local alert 
system, posting of areas where short-term peaks occur), or providing 
support for State, tribal, or local public health programs. Should an 
alternative approach be chosen, the State/tribe should ensure that the 
alternative measures required of the source are federally enforceable.
    As the concentration approaches the endangerment level of 2.0 ppm 
averaged over a 5-minute period, the health effects, as discussed 
earlier, will become more pronounced and severe. The EPA expects States 
and tribes will be more concerned about the potential impacts and be 
more assertive in pursuing corrective remedies with the sources as the 
5-minute peak concentrations approach the endangerment level. At 
concentrations at or above the endangerment level, EPA believes that 
imminent and substantial endangerment to the public health and welfare 
could occur, and if such is the case, urgent corrective actions would 
be warranted. However, even an isolated exceedance of the endangerment 
level might not require corrective action if the State or tribe find 
that the circumstances related to the exceedance are not likely to 
reoccur, or that the risk of exposure to sensitive populations is 
minimal. Again, EPA encourages States and tribes to determine the 
appropriate course of action for each situation based on the potential 
for public exposure and the risk to public health. While the State/
tribe would issue section 303 orders requiring urgent corrective 
actions, any long-term corrective actions would have the same 
enforceability, recordkeeping, and compliance requirements as specified 
for the concern level actions.
    The EPA believes proper and judicious implementation of the 
intervention level program by States and tribes would provide adequate 
protection against the recurrence of high, 5-minute SO2 peaks once 
such emissions are identified as a problem for particular sources. In 
EPA's view, States and tribes, being in the best position to assess the 
impact of 5-minute concentrations in their jurisdiction, would have 
primary responsibility to execute this section 303 program. However, 
EPA would retain the authority to take whatever actions the Agency 
considers appropriate under section 303 to address these situations. 
For example, if a State or tribe does not take action after the 
endangerment level has been exceeded, EPA would consult with the State 
or tribe to discuss the basis for their decision not to act. If EPA 
then determines that corrective action is warranted to protect public 
health, EPA itself would take action. Similarly, EPA would consult with 
the State or tribe and take action in cases where it is evident that 
frequent exceedances of the concern level constitute an imminent and 
substantial endangerment to public health, and the State or tribe has 
failed to take protective action.

B. Compliance and Enforcement Issues

    If the State/tribe decides that action is required under the 
intervention level program to abate the threat to public health, an 
effective means for ensuring that the source (or sources) has 
implemented the required course of action is needed. In many cases, 
compliance would consist of the State or tribe ensuring that the source 
has implemented the required remedies (e.g., equipment/process 
modifications, improving maintenance to address emissions contributing 
to short-term peaks, or a system to alert the public that conditions 
conducive to high 5-minute peak concentrations are present). However, 
if there are instances in which emissions can be feasibly measured on a 
5-minute basis, or if fuel sampling can be shown to be a feasible 
compliance indicator, the State or tribe may elect to set an emission 
limit and use emission measurement or fuel sampling as the method for 
determining compliance with any control requirements. In such cases, 
ambient air monitoring over a reasonable period after the 
implementation of the selected approach would be necessary to verify 
the effectiveness of the selected corrective actions.
    Enforcement of the intervention level program requirements would be 
based on the requirements of the applicable operating permit, 
enforceable consent order or agreements, or SIP. Because States and 
tribes have differing mechanisms for implementing their programs, EPA 
believes States and tribes are in the best position to determine the 
most appropriate implementation mechanism for their situations. 
Nonetheless, EPA believes that any corrective action required of a 
source by the State/tribe should be effective and practically 
enforceable--on both the State/tribal and Federal levels. Furthermore, 
the State/tribe should provide opportunity for public notice and 
comment on these actions. To this end, SIP revisions, operating 
permits, court orders, or other implementation mechanisms that provide 
for Federal enforceability and public participation would be 
appropriate methods for establishing corrective actions.

V. Relationship Between the Intervention Level Program and Existing 
Programs

A. Impact on SIP's, Attainment Planning and Implementation

    While both the intervention level program and the SIP address 
health concerns caused by ambient concentrations of SO2 in a given 
area, care should be taken to distinguish the two approaches. While the 
SIP and the intervention level programs are both meant to provide 
protection from the effects of ambient SO2 concentrations,

[[Page 216]]

they address different health concerns. The SIP is intended for 
implementation of the primary and secondary SO2 NAAQS, established 
under sections 108 and 109 of the Act to protect public health with an 
adequate margin of safety and protect the public welfare. The limits 
for the NAAQS as established are based on an annual arithmetic mean, a 
maximum 24-hour concentration and a maximum 3-hour concentration. The 
intervention level program, under the authority of section 303, is 
designed to address short-term (5-minute) ambient concentrations that 
present imminent and substantial endangerment to public health or 
welfare. While these programs complement each other, satisfaction of 
one program's requirements does not necessarily mean compliance with 
the other. For example, an area within a State may be in compliance 
with the requirements of the SIP and still be subject to 5-minute peaks 
of such magnitude and frequency that action under the intervention 
level program is warranted. Similarly, in a nonattainment area where 
progress is being made toward meeting the SIP requirements, the State/
tribe may conclude that action under the intervention level program is 
unnecessary if, for example (1) the area has no 5-minute peaks that 
exceed the concern level, or (2) the area has infrequent peak episodes 
that do not render a significant health risk. Furthermore, if any 
actions are taken by States, tribes, or industry to address 5-minute 
peaks of SO2 in a given area, care should be taken to ensure that 
such actions do not conflict with the existing SIP requirement, or the 
State or tribal attainment plan.
    As an example, after investigating 5-minute SO2 peak emissions 
in a given area and discussing various approaches with the source and 
the affected community, it may be determined that the most cost 
efficient way of addressing the situation would be to increase the 
stack height of a particular source. While the impact of increasing the 
stack height may not be considered in determining whether the emission 
limitation requirements of the SIP are satisfied, and though the source 
may already be in compliance with all applicable SIP limits, it is 
conceivable that the best way to address a given 5-minute concentration 
problem under the intervention level program could be through the use 
of dispersion techniques and intermittent controls. The EPA is not 
suggesting by this example that increasing stack heights is generally 
an appropriate means for addressing short-term peaks. States, tribes, 
sources, and affected communities are encouraged to consider other 
available approaches for minimizing the risk from short-term SO2 
exposures.
    In conclusion, implementation of the intervention level program 
cannot and should not lead to any relaxation of the SIP requirements. 
However, there will be cases where the implementation of the 
intervention level program will complement the implementation of the 
SIP, if reductions in emissions are achieved. In nonattainment areas 
where 5-minute SO2 peaks are also prevalent, the State or tribe 
may wish to coordinate attainment plan development so that the 
corrective action taken by the source is consistent with the objectives 
of both the attainment plan and the intervention level program.

B. Malfunctions

    The EPA has on occasion 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 certain 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. However, in some 
cases these emissions may be causing 5-minute SO2 peak 
concentrations that exceed the concern level of 0.60 ppm. The State or 
tribe must decide when and if action is needed to address such cases. 
The State or tribe may find that if exceedances associated with 
malfunctions, start-ups, or shutdowns occur frequently and pose a risk 
to public health, an appropriate remedial response (including controls, 
improved maintenance, or other alternative approaches) would be 
warranted.

C. Significant Harm Level Program

    The EPA views the SHL program and the intervention level program as 
separate programs designed to address different situations that pose a 
threat to public health. The SHL program establishes corrective actions 
in advance to address emergency episodes that occur over a period of 
time (in the case of SO2, the timeframe would be 24 hours or 
more). The intervention level program is intended to address peak 
concentrations which occur over a relatively short timeframe (5 
minutes) and, thereby, calls for the appropriate means to address the 
peaks to be determined after the peak episode occurs.
    In most cases, no overlap between the two programs is expected to 
occur. It is, however, conceivable that an area may be subject to high 
SO2 emissions and generate 5-minute and 24-hour ambient 
concentrations of such magnitude that a State or tribe would have cause 
to take action under the auspices of both the intervention level and 
the SHL programs. For example, an area experiencing a 24-hour average 
SO2 concentration of 1.0 ppm (the significant harm level) would 
also experience 5-minute peak concentrations in excess of 0.60 ppm (the 
concern level for the intervention level program).
    Under such circumstances, EPA expects corrective action will be 
promptly initiated through the SHL program. Once the corrective action 
required under that program has been established, steps would be taken 
to determine whether (1) that action effectively prevents 5-minute peak 
concentration episodes in excess of the intervention levels, or (2) if 
the 5-minute episodes occur independently of events in which the 24-
hour episode levels are exceeded. In the latter case, States and tribes 
would be expected to take further action under the intervention level 
program as necessary.

D. Acid Rain Program

    Under the acid rain program, sources (primarily coal-fired electric 
utilities) are given flexibility in how they choose to meet their 
emissions reductions, including the buying or selling of SO2 
emissions allowances. Regardless of the number of SO2 allowances a 
source holds, it may not emit at levels that would violate Federal, 
State, or tribal emission requirements established under title I of the 
Act to protect public health, including any emission requirements that 
would be established to carry out the intent of the intervention level 
program.

VI. Community Involvement in the Intervention Level Program

    As stated earlier, the intervention level program as designed would 
give States, tribes, local governments, and communities the authority, 
ability and flexibility to address localized health concerns caused by 
5-minute SO2 episodes more effectively. While State or tribal 
regulatory agencies and industrial sources would be expected to be 
primarily responsible for implementing the intervention level program, 
members of the local community, whose health may be

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significantly impacted by peak ambient SO2 concentrations, have a 
primary interest in the implementation of this program. The EPA 
encourages the States, tribes, industry, and local citizens to work 
together through the intervention level program to identify areas 
subject to 5-minute peaks, to assess the need for corrective action, 
and to develop corrective solutions.
    When identifying areas that are subject to high ambient peaks, 
States and tribes may not wish to limit their analysis to ambient air 
monitoring and risk analysis. The States and tribes may want to 
consider the number and nature of citizen complaints received as an 
indicator of a potential public health problem and apply appropriate 
resources to receiving, reviewing, and addressing the concerns of 
citizens and community groups. The EPA recommends that citizens who 
express concern about the health and welfare effects due to high 
ambient concentration peaks be given the opportunity to present and 
clarify their concerns to the State or tribe. Citizens, in turn, should 
be informed of the types and levels of information that would be most 
helpful in determining links between peaks and health effects and be 
given every opportunity to gather and provide that information. The EPA 
can serve as an information resource for States, tribes, and citizens 
providing the information it has available regarding health effects, 
risk analysis, ambient air concentrations, monitoring, and other 
issues, if requested.
    After the State or tribe completes its assessment of the health 
risks in an area caused by 5-minute SO2 concentrations, it may 
determine one of three things in an area: (1) measures to protect the 
public health are needed, (2) measures to protect the public health are 
not needed, or (3) more information is needed to reasonably determine 
if protective measures are needed. The EPA encourages States and tribes 
to keep local citizens and community groups informed during the 
decision-making process, to explain the factors and information used to 
supporting the decision, and to provide citizens ample opportunity to 
comment if they disagree with the decision.
    If the State or tribe decides that measures to protect the public 
health are necessary, EPA recommends that the protective measures be 
developed through a collaborative process involving the State, tribe, 
industry, and the local community. As part of the collaborative 
process, the parties involved should determine: (1) an agreed outcome 
or goal to be achieved by the protective measures, (2) appropriate 
actions to be taken by the emission sources to reduce the risk due to 
5-minute ambient SO2 concentrations, (3) a reasonable timetable 
for completion of the agreed-upon action (or actions), (4) a process to 
ensure that the action (or actions) agreed upon has been taken, and (5) 
a reasonable yardstick for assuring that the desired objectives have 
been achieved.

VII. Source Prioritization and Monitor Allocation

    Like the three implementation options originally proposed, a key 
element of this new proposed implementation strategy is the relocation 
of existing SO2 monitors to areas near point sources where peak 
SO2 concentrations may exist. Historically, EPA has relied on 
modeling to predict air pollutant concentrations. However, the use of 
models is not currently an effective means for predicting 5-minute 
SO2 excursions. The reasons for this, discussed in detail in the 
March 7, 1995 proposal (60 FR 12492), are summarized as follows: (1) 
model validation studies have not been conducted to determine if 
existing models can estimate with sufficient accuracy to be used in a 
regulatory context; (2) it is difficult to obtain accurate source 
emission data for 5-minute periods, since such data often depend on 
trying to measure emissions that may occur infrequently and at 
unpredictable times, concentrations, and flow rates; and (3) a method 
of determining the expected frequency of emission releases due to 
malfunctions would have to be employed in order to model these 
releases.
    For these reasons, EPA presented a ``targeted implementation 
strategy'' in the March 7, 1995 proposal that relied principally on 
ambient air monitoring instead of modeling to find areas exposed to 
high, 5-minute concentrations of SO2. Because the layout of the 
existing SLAMS network was intended for characterizing urban ambient 
air quality associated with 3-hour, 24-hour, and annual SO2 
concentrations, the network is not currently designed to measure 5-
minute peak SO2 concentrations from point sources. To allow for 
the relocation of monitors for measuring 5-minute peak concentrations, 
EPA proposed 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 November 15, 1994 (59 FR 58958) and the 
March 7, 1995 (60 FR 12492) proposals. The March 7, 1995 proposal also 
presented a strategy States and tribes could use to prioritize 
potential sources of high, 5-minute SO2 peaks for monitoring. The 
strategy presented three groups of sources ranked by their capacity for 
high emission rates and their potential for high, 5-minute peaks. 
Available air quality or exposure data and the effects of source 
location in complex terrain were also considerations in developing the 
groups.
    In ranking sources for monitoring 5-minute peaks, EPA did not 
expect States and tribes to rely solely on the three categories 
described in the original proposal. The EPA also recommended that 
States and tribes evaluate each facility on an individual basis, 
considering such factors as the type of process, past upsets and 
malfunctions, the type of fuel used, the complexity of the surrounding 
terrain, knowledge of how well the source is controlled, the compliance 
history of the source, proximity to population centers, and the history 
of citizen complaints. The States and tribes would also need to 
determine how heavily to weigh a Group A source in an area with low 
population density versus a Group C source in a more densely-populated 
area and consider the impact of different source types clustering 
within a given area. These considerations would form the basis for a 
State or tribal monitoring plan which would be submitted to EPA during 
the annual review of the SLAMS network. While EPA would review the 
monitoring plan developed by States or tribes, it was EPA's intent that 
States and tribes would retain the main role of decision making since 
they would have better knowledge of the individual circumstances 
pertaining to the potential sources to be targeted.
    Comments received on the targeted monitoring strategy indicate that 
some members of the public viewed the proposed strategy as being more 
rigid than EPA intended. Many commenters felt that the data and 
assumptions used to develop the ranking categories were outdated and/or 
conservative. Some felt that their respective industries should not 
have been given as high a priority as suggested by the categories. Many 
rejected the concept of prioritizing industrial categories, preferring 
that the prioritization of sources be based on the additional factors 
EPA originally proposed--health and exposure data, the size and 
configuration of sources, compliance history, proximity to population 
centers, etc.
    In response to the comments received, EPA wishes to clarify the 
criteria discussed in the March 7, 1995 proposal for use by States and 
tribes to prioritize

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the monitoring of sources for high, 5-minute SO2 peaks. The EPA is 
not requiring States or tribes to prioritize sources for monitoring in 
accordance with the three categories of industrial sources discussed in 
that proposal. The EPA is now recommending that States and tribes 
evaluate the need to monitor sources based on factors such as the 
history of citizen complaints, the compliance history of the sources in 
question, the State or tribe's knowledge of the operational 
characteristics of a given source (e.g., the likelihood of highly 
variable emissions, maintenance history), the population in the 
vicinity of a source (or more specifically, the population of 
asthmatics and other individuals susceptible to high SO2 
concentrations), and environmental justice concerns. The EPA maintains 
the proposed revisions to the ambient air quality surveillance 
requirements (40 CFR part 58) and the proposed technical changes to the 
requirements for ambient air monitoring reference and equivalent 
methods (40 CFR part 53), as discussed earlier.

VIII. Reconsideration of Proposed 24-Hour Significant Harm Level and 
Episodes Criteria

    In the March 7, 1995 action (53 FR 14926), EPA also proposed 
revisions to the 24-hour SHL for SO2. The EPA is now reconsidering 
this proposed SHL revision.
    The EPA based its previous proposal on a reassessment of the data 
upon which the original SHL were based and an assessment of more recent 
scientific evidence on sulfur oxides and particulate matter. The 
scientific evidence suggested that the combination of SO2 and high 
levels of particulate matter can be associated with increases in daily 
mortality. The final 24-hour PM-10 (particles with an aerodynamic 
diameter less than or equal to a nominal 10 micrometers) SHL of 600 
g/m3 takes this potential interaction into account. This 
raised the question as to whether the remaining SO2 SHL is 
sufficient. The possibility that SO2 alone or in combination with 
other pollutants or fog droplets may be in part responsible for the 
effects associated with 24-hour exposures suggests the need to continue 
a 24-hour SHL for SO2, but at a substantially lower concentration. 
Accordingly, EPA proposed to revise the 24-hour SO2 SHL from 1.0 
(2,620 g/m3) to 0.29 ppm (750 g/m3), as 
well as revisions to the 24-hour episode levels.
    Upon further consideration, EPA now believes that a revised 24-hour 
SHL is not necessary to protect the public health. Based on a review of 
existing data, the EPA now believes the additional areas that would 
require corrective action as a result of changing the SHL (and the 
episode levels) are generally areas that have not attained the SO2 
NAAQS. The EPA expects that continued efforts of the States and tribes 
toward submittal, approval, and enactment of State or tribal 
implementation plans should not only achieve attainment of the NAAQS, 
but should also address the impact on human health caused by 
significant 24-hour SO2 episodes. For this reason, EPA is amending 
its earlier proposal, recommending that no revision to the 24-hour SHL 
for SO2 be made at this time. The EPA solicits comment on this 
issue.

IX. Comments and the Public Docket

    The EPA welcomes comments on all aspects of this proposed 
rulemaking. Commenters are especially encouraged to give suggestions 
for improving or clarifying any aspects of the proposal. All comments, 
with the exception of proprietary information, should be directed to 
Docket No. A-94-55 (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 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.

IX. Administrative Requirements

A. Executive Order 12866

    Under Executive Order 12866, the Agency must determine whether a 
regulatory action is ``significant'' and, therefore, subject to Office 
of Management and Budget (OMB) review and the requirements of the 
Executive Order. The order defines a ``significant regulatory action'' 
as one 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 or recipients 
thereof; or
    (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.
    While EPA does not believe the intervention level program would 
potentially have an annual effect on the economy of $100 million or 
more, the proposed intervention level program was developed in part due 
to comments received on earlier proposed implementation strategies 
which were deemed to be significant. Also, to some extent, the 
characteristics of the intervention level program--local 
responsibility, flexibility, community involvement--represents a novel 
regulatory approach. For these reasons, EPA has judged that the 
proposed intervention level program is a significant regulatory action 
as defined by Executive Order 12866 and has submitted this action to 
OMB for review. The EPA has prepared a regulatory impact analysis (RIA) 
which is summarized below.
    In the event that a State or tribe determines that some means of 
corrective action is necessary under the intervention level program, 
the actions taken will be specific to the source and the area impacted 
by high, 5-minute ambient concentrations. As such, the costs can vary 
widely (from a low-cost alternative, such as fuel switching, to the 
installation of more costly add-on control equipment). Because of the 
tremendous uncertainty surrounding the estimation of national costs, 
the RIA evaluates the cost of control through a series of case studies 
that present information on a sample of control strategies. The case 
studies chosen for analysis in the RIA are based upon available data 
and characteristics of the SO2 problem (and areas) that provide a 
broad scope of the issues associated with the implementation of the 
intervention level program. Of the predicted actions to be taken under 
this program, two of them correspond with case studies provided in the 
RIA. It should be noted, however, that the control strategies evaluated 
for the case

[[Page 219]]

studies were chosen to provide the reader with a wide variety of 
approaches to resolve a short-term SO2 problem, and thus, the 
strategies may not coincide with strategies that may be developed by 
States and tribes to resolve the problem in their local areas. The list 
of control strategies analyzed is not exhaustive, as time and resource 
constraints preclude analysis of all possible control alternatives 
(including new and innovative ways of addressing SO2 
concentrations that States and local communities may develop while 
evaluating a 5-minute SO2 problem). As discussed earlier, States 
or tribes may choose to have sources address health risks from short-
term peaks through alternative approaches such as public health 
education campaigns or public warning/notice of peak episodes. Such 
approaches may have lower costs than measures that reduce SO2 
emissions.
    Since the current SLAMS network was not developed to identify areas 
that experience 5-minute peak SO2 concentrations, it is difficult 
to predict how many areas of concern might be identified by States and 
tribes when they relocate monitors for this purpose. A survey of the 
States yielded 63 source-based monitors that monitored 5-minute 
concentrations during 1993 and 1994. Of these 63 monitors, 27 (43 
percent) registered at least one exceedance of the concern level (0.6 
ppm), and 1 (2 percent) registered exceedance of the endangerment level 
(2.0 ppm). Based on a detailed evaluation of data from these monitors, 
EPA identified ten areas that the Agency felt would be evaluated for 
the level of public health risk associated with short-term SO2 
episodes. Of the ten areas, EPA reasonably estimates that action under 
the intervention level program could be warranted for approximately 
five areas. The EPA is using several types of information as a basis 
for projecting the likelihood of action under the intervention level 
program, including: (1) historical knowledge about the situation based 
on interactions between the EPA Regions, States and local sources; (2) 
comments from sources, States, and local agencies on the original 
proposals which not only discuss local situations, but also the 
regulatory agency's likely response (because EPA is not only making a 
provisional judgment about the potential public health risk from these 
situations, but is also assessing how the regulatory agencies would 
respond); (3) air quality and census data; and (4) information about 
the industrial processes at facilities in the locations of concern.
    The EPA recognizes that relocation of monitors around sources and 
in areas of potential concern could identify more areas where 
assessment of public health risk and possible intervention would be 
warranted. Since there is significant uncertainty about the extent to 
which States and tribes will relocate monitors, the total cost of the 
final program could be higher than the cost EPA has so far identified. 
The EPA invites public comment on its approach to estimating the costs 
of this proposal.
    The case studies indicate the range of annualized cost for 
solutions to different 5-minute SO2 problems to be from 
approximately $300,000 to $2.2 million. In addition, some case studies 
have no cost associated with the program since action is not taken. 
Yet, other studies indicate the potential for either a cost savings of 
$257,544 or a total annualized cost of $30 million. The range of costs 
reflects the significant amount of flexibility that regulatory 
authorities, communities, and sources have under the intervention level 
program to resolve short-term SO2 problems at a substantially 
lower cost than other potential regulatory vehicles. For example, the 
previously-proposed regulatory option of establishing a new short-term 
SO2 NAAQS (0.60 ppm, 5-minute average) was estimated to cost $1.75 
billion. Several sources expected to incur costs under the NAAQS option 
would conceivably have no regulatory action taken upon them under the 
intervention level program and thus would not incur compliance costs. 
Even if the five actions predicted so far to occur under the 
intervention level program have the highest end of costs estimated in 
the RIA case studies ($2.2 million), the total cost of these five 
actions would be $11 million--$1.739 billion less than the NAAQS option 
proposed earlier.
    Given that implementation of the intervention level program will 
only occur in areas where a State or tribe determines there is 
substantial risk to human health, it is unlikely that a vast number of 
sources in any one industry will be impacted. It is likely that only 
one or two sources of an industry will incur additional control costs 
to resolve a 5-minute SO2 problem. If the sources affected by the 
program are not the marginal producers of an industry, the market 
supply curve is not likely to shift and the source would not benefit 
from increased prices. Rather, the source would absorb the compliance 
costs and incorporate them into the cost of production to determine 
their optimal level of operation.
    The quantified benefits of the case studies ranged in value from 
$2,700 to $44,100. As such, the costs exceed benefits by a significant 
amount. The small magnitude of benefits results from mainly two 
factors. First, the short-term peaks in SO2 under consideration 
impact a fairly small geographic area within the local vicinity of the 
model plants. The small geographic area leads to a relatively small 
number of people being exposed to these short-term peaks. Second, the 
benefit estimates are limited to the health benefits accruing to 
asthmatics. The welfare benefits associated with any ecosystem--
visibility, odor, materials damage, or particulate matter improvements 
that may result from control of short-term peaks in SO2--have not 
been considered. Although the costs determined for the case studies 
exceed the quantifiable benefits, the intervention level program 
achieves a reasonable solution to short-term SO2 problems at 
substantially lower cost than other potential regulatory vehicles, such 
as the previously-proposed, new short-term SO2 NAAQS. Several of 
the sources assumed to incur costs under the short-term NAAQS option 
would conceivably not require regulatory action taken upon them under 
the proposed intervention level program and would thus incur no 
compliance costs. In addition, a regulatory authority may consider 
environmental justice as a criteria to warrant action under the 
intervention level program. Paragraph E of this section of the preamble 
discusses the environmental justice analysis prepared for the RIA.

B. Monitoring and Administration Costs

    There are 679 sites in the current SLAMS network established to 
monitor for violations of the SO2 NAAQS. It was estimated in the 
previous proposal that approximately two-thirds of the monitors could 
be relocated in order to monitor for short-term SO2 concentrations 
without compromising the current network of monitors for the NAAQS. 
When final changes to the requirements for ambient air monitoring 
reference and equivalent methods (40 CFR part 53) and revisions to the 
ambient air quality surveillance requirements (40 CFR part 58) are 
promulgated, the States, tribes, and local authorities will be given 
guidance to place anywhere from 1 to 4 monitors around sources where 
short-term SO2 concentrations are of concern. While the total 
number of monitors to be relocated cannot be determined presently, it 
is likely that significantly fewer than two-thirds of the current 
network will be relocated under the intervention level program.

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    The cost to relocate a monitor is specific to the monitor and site. 
However, if a stand-alone monitor can be relocated without having to 
replace operating and maintenance equipment (i.e., the shelter, 
calibration equipment, data logger, etc.), EPA estimates it would cost 
$18,630 to relocate the monitor. If a monitor that is relocated 
requires the installation of new equipment, the total cost of 
relocation would be $45,050. In addition, there is a cost to operate 
the monitor estimated at $22,000 per year. If the monitor is currently 
operating independently, relocating the monitor would merely transfer 
this expense to the new site. Therefore, there would be no incremental 
cost to operate the relocated monitor. However, the EPA is aware that 
some SO2 monitors are colocated with other monitors (e.g., for 
ozone, nitrogen oxides, and particulate matter). When relocating the 
SO2 monitor in this case, the existing site would maintain the 
current operating expense for the remaining monitors, and the new site 
for the relocated SO2 monitor would incur an incremental operating 
cost of $22,000. Thus the total cost to relocate a monitor could range 
from $18,630 for a stand-alone monitor that already has the necessary 
equipment to relocate to a new site and will not incur any incremental 
operating costs to $67,050 for a monitor requiring both new equipment 
and operating expenses.
    The EPA recognizes that as monitors are relocated, areas of concern 
in addition to those estimated may be identified. To the extent more 
information becomes available, EPA will estimate the anticipated impact 
of relocating monitors on total program costs in the final rule.
    The EPA recognizes that there are costs associated with the 
administration of the intervention level program. These costs include: 
determining the need to relocate monitors; evaluating citizen 
complaints; assessing public health risk; and developing, implementing, 
and monitoring actions required of the source to reduce risk. The EPA 
believes that the additional costs resulting from the intervention 
level program would be minimal for two reasons. First, many States and 
tribes currently have sufficient administrative infrastructure in place 
to conduct such activities. Second, the flexibility of the program 
allows States and tribes to use their resources in the most efficient 
manner in implementing the program. The EPA invites public comment on 
the costs associated with administering the intervention level program.

C. Regulatory Flexibility Analysis

    The Regulatory Flexibility Act (RFA) requires that all Federal 
agencies consider the impacts of final regulations on small entities, 
which are defined to be small businesses, small organizations, and 
small governmental jurisdictions (5 U.S.C. 601 et seq.). 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 implement the intervention level program under the 
authority of section 303 would impose no new major requirements. 
Furthermore, the control measures necessary to implement the 
intervention level program are developed by the States and tribes. In 
selecting such measures, the States and tribes have considerable 
discretion to address the risk presented by 5-minute ambient SO2 
concentrations. Therefore, the impact on small entities from the 
intervention level program would be determined by how the States and 
tribes choose to implement the program. For these reasons, any 
assessment performed by EPA on the costs of implementation at this time 
would necessarily be speculative. On the basis of the above 
considerations and findings, and as required by section 605 of the RFA, 
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. Impact on Reporting Requirements

    While there are reporting requirements associated with related 
sections of the Act, particularly sections 107, 110, 160, and 317 (42 
U.S.C. 7407, 7410, 7460, and 7617), there are no specific Federal 
reporting requirements associated with the proposed intervention level 
program. Because the program gives States and tribes discretion to take 
action as warranted by the risk to the public health, it is difficult 
to project what recordkeeping and reporting requirements States and 
tribes may feel are needed to ensure compliance and enforceability in 
specific cases. Furthermore, any necessary reporting and recordkeeping 
would be restricted to sources the State/tribe determines as 
contributing to high 5-minute concentrations in a localized area. No 
recordkeeping or reporting would be required from sources not 
contributing to 5-minute peaks or from sources in areas not subject to 
high 5-minute peaks.
    Consequently, EPA is not asking for approval under the Paperwork 
Reduction Act for any such requirements at this time. The EPA welcomes 
comments on the nature and burden of recordkeeping and reporting 
requirements that may be associated with the intervention level 
program. As the information requirements of the program become clearer, 
EPA will reevaluate the need for information collection approval under 
the Paperwork Reduction Act.

E. Unfunded Mandates Reform Act

    Title II of the Unfunded Mandates Reform Act of 1995 (UMRA), P.L. 
104-4, establishes requirements for Federal agencies to assess the 
effects of their regulatory actions on State, local, and tribal 
governments and the private sector. Under sections 202, 203, and 205, 
respectively, of the UMRA, EPA generally must prepare a written 
statement, including a cost-benefit analysis, for proposed and final 
rules with ``Federal mandates'' that may result in expenditures to 
State, local and tribal governments, in the aggregate or to the private 
sector, of $100 million or more in any 1 year. Before promulgating an 
EPA rule for which a written statement is needed, section 205 of the 
UMRA generally requires EPA to identify and consider a reasonable 
number of regulatory alternatives and adopt the least costly, most 
cost-effective or least burdensome alternative that achieves the 
objectives of the rule. The provisions of section 205 do not apply when 
they are inconsistent with applicable law. Moreover, section 205 allows 
EPA to adopt an alternative other than the least costly, most cost-
effective or least burdensome alternative if the Administrator 
publishes with the final rule an explanation why that alternative was 
not adopted. Before EPA establishes any regulatory requirements that 
may significantly or uniquely affect small governments, including 
tribal governments, it must have developed a small government agency 
plan under section 203 of the UMRA. The plan must provide for notifying 
potentially-affected, small governments, enabling officials of affected 
small governments to have meaningful and timely input in the 
development of EPA regulatory proposals with significant Federal 
intergovernmental mandates, and informing, educating, and advising 
small governments on compliance with the regulatory requirements.
    The EPA has determined that this proposal does not contain a 
Federal mandate that may result in expenditures

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of $100 million or more for State, local, or tribal governments, in the 
aggregate or the private sector in any 1 year. The EPA anticipates that 
the number of cases in which abatement of short-term SO2 
concentrations will be necessary will be few in number and that the 
States and tribes will work with the sources and the local community to 
arrive at the most appropriate and efficient control approach to reduce 
the risk to the public. For these reasons, the expenditures under the 
intervention level program are not expected to exceed the $100 million 
threshold. Thus, today's proposal is not subject to the requirements of 
sections 202 and 205 of the UMRA.

F. 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 regulatory 
impact analysis.
    A number of factors indicate that asthma may pose more of a health 
problem among non-white individuals, children, and urban populations. 
With these factors in mind, a general screening analysis is conducted 
to examine the sociodemographic characteristics of the case study areas 
potentially impacted by short-term SO2 peaks.
    Overall, the population distributions in the case study areas do 
not indicate that a disproportionate number of non-white individuals 
would be impacted by short-term SO2 ambient concentrations greater 
than 0.60 ppm. The analysis also indicates that there are twice as many 
children residing in the case study areas as compared to the national 
average, and potentially 595 of these children could have asthma and 
thus experience health impacts during peak SO2 concentrations. In 
addition to the large number of children potentially exposed to peak 
SO2 concentrations, 27 percent of the households in the case study 
areas are below the poverty level, which is twice the national average. 
It should be noted, however, that it is not known how many of the 
households below the poverty level contain asthmatic individuals. Given 
the available data, there is an indication that a disproportionate 
number of children and households below the poverty level are exposed 
to short-term SO2 peaks.
    In general, children do not have sufficient resources to relocate 
or take action against sources of SO2 emissions. Similarly, 
households below the poverty level are generally unlikely to relocate 
or take action against sources of SO2 emissions. Not only do these 
households often lack the resources to relocate, but they may be 
dependent on the local industrial sources for employment. In such a 
case, these households may be reluctant to take action against sources 
of SO2 emissions if this action would adversely impact employment 
opportunities.

List of Subjects in 40 CFR Part 51

    Environmental protection, Administrative practices and procedure, 
Air pollution control, Intergovernmental relations, SO2, Reporting 
and recordkeeping requirements, State implementation plans.

    Dated: December 20, 1996.
Carol M. Browner,
Administrator.

References

EPA (1982a), Air Quality Criteria for Particulate Matter and Sulfur 
Oxides, Environmental Criteria and Assessment Office, Research 
Triangle Park, NC, EPA-600/8-82-029a-c.
EPA (1982b), 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.
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 (1994a), Supplement to the Second Addendum (1986) to Air Quality 
Criteria for Particulate Matter and Sulfur Oxides (1982): Assessment 
of New Findings on Sulfur Dioxide Acute Exposure Health Effects in 
Asthmatic Individuals, Environmental Criteria and Assessment Office, 
Research Triangle Park, NC, EPA/600/FP-93/002.
EPA (1994b), Review of the Ambient Air Quality Standards for Sulfur 
Oxides: Updated Assessment of Scientific and Technical Information, 
Supplement to the 1986 OAQPS Staff Paper Addendum, Office of Air 
Quality Planning and Standards, Research Triangle Park, NC, EPA/452/
R-94-01
Horstman, D. H. Roger, L. J.; Kehrl, H. R.; Hazucha, M. J. (1986). 
Airway sensitivity of asthmatics to sulfur dioxide. Toxicol. Ind. 
Health. 2:289-298.
Roger, L. J.; Kehrl, H. R.; Hazucha, M.; Horstman, D. H. (1985). 
Bronchoconstriction in asthmatics exposed to sulfur dioxide during 
repeated exercise. J. Appl. Physiol. 59: 784-791.

    For the reasons set forth in the preamble, EPA proposes to amend 
part 51 of Chapter I of title 40 of the Code of Federal Regulations as 
follows:

PART 51--REQUIREMENTS FOR PREPARATION, ADOPTION, AND SUBMITTAL OF 
IMPLEMENTATION PLANS

    1. The authority citation for part 51 continues to read as follows:

    Authority: 42 U.S.C. 7401-7671q.

Subpart H--Prevention of Air Pollution Emergency Episodes

    2. Section 51.154 is added to Subpart H to read as follows:


Sec. 51.154  Intervention levels.

    (a) Each plan must contain the authority to take whatever action 
necessary to prevent further exceedances of the following concern level 
attributable to emissions from a source or group of sources where one 
exceedance has occurred, and the State, tribe, or local air pollution 
control agency determines that the potential for further exceedances of 
this level constitutes imminent and substantial endangerment to public 
health or welfare, or the environment:

    Sulfur dioxide (SO2)--0.60 ppm, 5-minute hourly maximum 
value.

    (b) Each plan must contain the authority to take whatever action 
necessary to prevent further exceedances of the following endangerment 
level attributable to emissions from a source or group of sources where 
one exceedance has occurred, and the State, tribe, or local air 
pollution control agency determines that the potential for further 
exceedances of this level constitutes imminent and substantial 
endangerment to public health or welfare, or the environment:

    Sulfur dioxide (SO2)--2.0 ppm, 5-minute hourly maximum 
value.

    (c) Nothing in paragraphs (a) or (b) of this section shall preclude 
the State, tribe, or local air pollution control agency from addressing 
any public health threat arising from exceedances of the concern or 
endangerment levels with measures other than the imposition

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of control requirements designed to reduce emissions from specific 
sources, as long as the measures chosen effectively reduce the threat 
to public health.
    (d) The State, tribe, or local air pollution control agency shall 
ensure that any action to be taken on the part of the source or group 
of sources to address any public health threat caused by exceedances of 
either the concern or endangerment level shall be enforceable by the 
Administrator and by citizens under the Act.
    (e) A 5-minute hourly maximum value for SO2 is the highest of 
the 5-minute averages from the 12 possible nonoverlapping periods 
during a clock hour. An exceedance occurs if the 5-minute hourly 
maximum is greater than the 5-minute concern or endangerment level 
after rounding. A value of 0.605 would be rounded to 0.61; a value of 
2.05 would be rounded to 2.1. Therefore, the smallest value for an 
exceedance of the concern level is 0.61 and the smallest value for an 
exceedance of the endangerment level is 2.1. A 5-minute maximum shall 
be considered valid if:
    (1) The 5-minute averages were available for at least 9 of the 12 
5-minute periods during the clock hour; or
    (2) The value of any 5-minute average is greater than the concern 
level.

[FR Doc. 96-32978 Filed 12-31-96; 8:45 am]
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