[Federal Register Volume 59, Number 248 (Wednesday, December 28, 1994)]
[Unknown Section]
[Page ]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 94-31742]


[Federal Register: December 28, 1994]


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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Parts 51, 52, 60, 61 and 64

[FRL-5128-3]


Enhanced Monitoring Program

AGENCY: Environmental Protection Agency (EPA).

ACTION: Proposed rule; reopening of public comment period.

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SUMMARY: EPA is soliciting comment on a limited set of revisions to its 
proposed Enhanced Monitoring Program. EPA received numerous comments on 
a wide range of issues pertaining to the October 22, 1993 proposed 
rulemaking for a new 40 CFR part 64. EPA is issuing this notice to take 
additional comment on a limited number of specific issues concerning 
the proposed regulations. First, the Agency is considering phasing in 
the implementation of the program over a five year period. This 
implementation approach would allow for the Agency to develop guidance 
on acceptable enhanced monitoring protocols for many types of affected 
emissions units in order to streamline the selection and approval of 
enhanced monitoring. Second, EPA seeks comment on the consideration of 
cost in selecting and approving enhanced monitoring protocols. Third, 
the Agency seeks comment on a second phase of applicability for 
nonattainment areas and on specifically adopting periodic monitoring 
under 40 CFR part 70 as sufficient enhanced monitoring for applicable 
emissions units that do not meet the emission level applicability 
thresholds for part 64 enhanced monitoring. The range of issues on 
which EPA is soliciting comment is strictly limited to those issues 
identified in this notice.

DATES: Comments on the issues discussed in this notice must be received 
by January 27, 1995.

ADDRESSES: Comments: Comments must be mailed (in duplicate, if 
possible) to: EPA Air Docket (LE-131), Attention: Docket No. A-91-52, 
Room M-1500, Waterside Mall, 401 M Street SW., Washington, DC 20460. 
Comments should refer to page numbers and columns whenever possible. 
Only comments addressing the specific issues identified below will be 
considered.
    Docket: Supporting information used in developing the regulations 
is contained in Docket No. A-91-52. This docket is available for public 
inspection and copying between 8 a.m. and 5:30 p.m. Monday through 
Friday, excluding government holidays, and is located at: EPA Air 
Docket (LE-131), Room M-1500, Waterside Mall, 401 M Street SW., 
Washington, DC 20460. A reasonable fee may be charged for copying.

FOR FURTHER INFORMATION CONTACT: Scott Throwe, U.S. Environmental 
Protection Agency, Office of Enforcement and Compliance Assurance, 
Manufacturing, Energy and Transportation Division, at (202) 564-7013.

SUPPLEMENTARY INFORMATION:

I. Purpose of Today's Notice

    EPA received numerous comments on many issues in response to the 
October 22, 1993 proposal to adopt an Enhanced Monitoring Program. The 
EPA has reviewed those comments, and has engaged in a series of 
discussions with a wide range of members of the public, including State 
and local governments, affected industries, and environmental groups. 
(Summaries of those discussions are contained in Docket No. A-91-52.) 
Based on EPA's review of the written comments received, and in light of 
the views presented by the parties noted above, EPA has determined that 
it would be appropriate to reopen the comment period to solicit 
additional comments on a limited number of issues. The EPA is 
soliciting comment on the following issues: phasing in the 
implementation of the Enhanced Monitoring Program over a five year 
period, including a process for developing guidance on example 
protocols and an implementation deadline that together would establish 
the timing for phasing in the program; the consideration of cost in 
proposing and approving enhanced monitoring protocols; a second phase 
of applicability in nonattainment areas; and the adoption of periodic 
monitoring under 40 CFR part 70 as sufficiently enhanced monitoring for 
applicable emissions units that do not meet the emissions level 
applicability thresholds for part 64 enhanced monitoring. The Agency 
believes it is useful to reopen the comment period in this limited 
manner in order to be certain that EPA has the benefit of a full range 
of views on these topics.
    This rulemaking is subject to a court-ordered deadline established 
by a consent decree in Sierra Club v. Browner, No. 93-0124 (NHJ) 
(D.D.C.). The original September 30, 1994 deadline for completion of 
this rulemaking was extended by the court at the request of the parties 
to December 20, 1994. The parties have agreed to request that the court 
extend the deadline again, to April 30, 1995 in order to accommodate 
this limited revision to the original rulemaking proposal and reopening 
of the comment period. The EPA believes that most of the issues 
addressed in the October 22, 1993 proposal have been fully addressed in 
the numerous detailed comments already received. For this reason, and 
in order to meet the court-ordered deadline and ensure that the 
Enhanced Monitoring Program is promulgated without undue delay, the 
scope of issues addressed in this notice is limited. The Agency will 
not consider comments submitted on issues that are not related 
specifically to those addressed in this notice. The issues on which EPA 
is soliciting comment are set forth below.

II. Implementation

    The proposed regulations would require that the owner or operator 
of a major stationary source propose an enhanced monitoring protocol as 
part of an application for a permit under the operating permits program 
pursuant to title V of the Act. In the public comments received on the 
proposed regulations, many commenters expressed concern about the 
burden of the enhanced monitoring protocol selection process on the 
operating permits program process. Many commenters suggested modifying 
the implementation approach to address their concerns regarding burdens 
associated with the permit process. Some commenters suggested that EPA 
engage in rulemaking to determine nationally applicable enhanced 
monitoring protocols for each source category as opposed to a permit-
based implementation approach. Others suggested separating the protocol 
approval process from the permit approval process. Finally, still other 
commenters suggested phasing in the implementation so that permitting 
authorities would not be required to implement the entire enhanced 
monitoring program in the first round of permits without the benefit of 
national guidance on example enhanced monitoring protocols.
    Because of the concerns about burdens to the permit process, EPA is 
considering phasing in implementation of the enhanced monitoring rule 
over a five year period. The implementation approach would have several 
elements. First, EPA would develop guidance on presumptively acceptable 
protocols that may be used for particular process/pollutant 
combinations. In referring to ``process/pollutant combinations,'' the 
Agency is referring to emissions units classified on both a pollutant-
specific basis and on a process-specific basis, including the 
applicable pollutant control measures, and, where appropriate, the 
nature of the emission limitation or standard. For example, one 
process/pollutant combination could be SO2 emissions from a coal-fired 
boiler using a scrubber to achieve compliance with an SO2 standard 
expressed in lbs/mmBtu, while another could be a similar boiler using 
low sulfur coal to achieve compliance with a sulfur-in-fuel limit.
    After EPA issues guidance for a particular process/pollutant 
combination, the owner or operator of an affected source that includes 
such a combination for an emissions unit subject to part 64 would be 
required to propose an enhanced monitoring protocol as part of the 
operating permit application for the applicable emissions unit. Except, 
as discussed below, sources generally would not be required under part 
64 to propose a protocol in the absence of EPA guidance. The protocol 
may be based on a presumptively acceptable example protocol developed 
by EPA or a different monitoring approach that can satisfy the part 64 
criteria. If the permitting authority has published a notice requesting 
public comment on a draft title V permit before EPA issues applicable 
guidance for a particular process/pollutant combination, then an 
enhanced monitoring protocol would not have to be proposed for that 
emissions unit until either a reopening of the permit that involves 
public notice and comment, or the next renewal of the permit.
    Finally, to ensure timely implementation of the program, EPA would 
incorporate a ``hammer'' provision that would be triggered on January 
1, 2000. Under this provision, any title V operating permit issued 
after the effective date of the ``hammer'' provision would have to 
include enhanced monitoring for emissions units subject to part 64. In 
addition, any existing permit that does not include an enhanced 
monitoring protocol where one would have been required by part 64 in 
the absence of phased implementation would have to be reopened 
expeditiously to incorporate enhanced monitoring. This ``hammer'' 
provision would apply regardless of whether EPA has issued guidance for 
a particular process/pollutant combination.
    Nothing in this phased approach would prevent a State from 
requiring that enhanced monitoring comporting with the part 64 criteria 
be included in a title V operating permit at any time before EPA's 
guidance for the relevant pollutant/process combination is available.
    The following outline describes in more detail each of these 
particular elements of EPA's suggested implementation approach. The 
Agency believes that its suggested approach alleviates many of the 
burdens associated with trying to implement enhanced monitoring in the 
first round of operating permits. The Agency's guidance development 
process would serve as a means of assisting sources and permitting 
authorities alike in implementing the program. At the same time, this 
approach would assure that enhanced monitoring is adopted in a timely 
manner at all affected emissions units. The EPA requests specific 
comment on this suggested approach to phasing in the program. The 
Agency solicits suggestions on any variations on this approach that 
commenters believe would reduce burdens on the permitting process while 
assuring timely adoption of enhanced monitoring protocols at affected 
emissions units.

A. Guidance Development Process

    As discussed in the preamble to the proposed rule (see 58 FR 
54658), EPA is preparing an Enhanced Monitoring Reference Document that 
will serve as guidance on the implementation of the Enhanced Monitoring 
Program and that will include example protocols that can be used by 
various types of emissions units with respect to specific process/
pollutant combinations. The Agency noted in the preamble to the 
proposed rule that EPA intended this document to be a compendium of 
available monitoring that would be updated on a regular basis.
    Under the implementation approach described in this notice, the 
purpose of the Enhanced Monitoring Reference Document would change in 
some important respects. First, EPA would issue guidance for a given 
process/pollutant combination only after a notice of availability of 
the example protocol in draft form is published in the Federal 
Register, with an opportunity for the public to respond in writing. The 
Agency would commit to publishing example protocols for a wide variety 
of process/pollutant combinations over the next four years, with many 
examples scheduled to be completed by the end of 1995. In addition, the 
examples published in the Enhanced Monitoring Reference Document would 
serve as presumptively acceptable protocols for the type of process/
pollutant combinations covered by the individual protocols.
    This approach would allow owners or operators and permitting 
authorities to rely on the examples in the Enhanced Monitoring 
Reference Document to a greater extent than contemplated in the 
preamble to the proposed rule. However, the Agency notes that the 
guidance is intended to remain as guidance, and would not be a binding 
regulation. Thus, owners or operators would not be required to use 
these example protocols where an alternative protocol would satisfy the 
part 64 criteria. The Agency emphasizes that the flexibility in the 
proposed rule to propose other monitoring satisfying the criteria in 
the rule would be retained.
    The Agency intends to develop presumptively acceptable protocols in 
a manner that assures the broadest coverage of process/pollutant 
combinations as expeditiously as possible while providing interested 
parties the opportunity for input. One issue on which the Agency is 
soliciting comment is the prioritization for developing example 
protocols, including how to group example protocols to allow cost-
effective collection of supporting data and other technical background 
information while at the same time ensuring that the most 
environmentally significant protocols are completed expeditiously.
    The Agency also solicits comment on whether and how to use 
particular types of tools for evaluating the degree of confidence that 
a particular monitoring methodology can provide in demonstrating 
compliance. In particular, the Agency is considering a ``Data Quality 
Objectives'' (DQO) process for protocol evaluation where EPA guidance 
is not available or in circumstances in which a source proposes an 
alternative to EPA's example protocol, although a DQO process may also 
be helpful to EPA in developing its example protocols. (Item No. IV-A-3 
in the docket for this rulemaking provides a detailed description of 
this process.) Recognizing that all measurements have imprecisions, EPA 
staff have developed the DQO process for application to environmental 
data collection programs. The DQO process is a systematic method for 
designing and evaluating any data collection activity, including the 
development and evaluation of many types of enhanced monitoring 
protocols. The process can account for the effects of process or 
emissions variability, margin of compliance, measurement precision, and 
frequency of data collection or measurements in designing an enhanced 
monitoring protocol. The DQO procedure is very similar to other 
statistical procedures used in the manufacturing and chemical process 
industries to optimize equipment design and production operations.
    The application of the DQO process to protocol development and 
review would reduce uncertainty about whether a proposed protocol will 
be accepted and will promote consistent decisions on review of 
protocols. Application of the DQO process requires the establishment of 
an acceptable level of probability of compliance assurance that 
enhanced monitoring data must meet when the affected emissions unit is 
emitting near or over the applicable emission limit. The appropriate 
level for the probability limit is an issue for which the Agency 
requests comment. The probability level selected will necessarily 
affect protocol design. For example, a low probability of error (e.g., 
less than 5 percent) may dictate more frequent, and thus, costly, 
sampling than a higher probability (e.g., 10 percent or higher). In 
another example, the probability level selection may be linked to the 
risk associated with a particular emission, that is, a lower 
probability may be applied for higher risk emissions monitoring systems 
data. The data needed to calculate these probabilities can be obtained 
through field tests, historical data, quality assurance/quality control 
documentation (e.g., measurement method precision), data from tests at 
similar sources, or engineering and scientific literature.
    In return, the DQO process would provide the owner or operator and 
the permitting authority a method for evaluating enhanced monitoring 
protocol design effectiveness. It also would allow for significant 
flexibility in protocol design regarding which parameters should be 
monitored, frequency of data collection, and margin of compliance. The 
result should be cost-effective protocols that meet the data quality 
criteria in part 64.
    The DQO process would provide an iterative planning method for the 
design of the enhanced monitoring protocol. The process leads to a 
mathematical determination of the probability of decision errors 
associated with reported protocol values. The DQO process might also 
optimize the protocol design process by identifying the most effective 
data collection and analysis design for the protocol that will satisfy 
the DQOs. This element of the process may include additional data 
collection on alternative protocol designs, formulating additional 
mathematical expressions, or redefining the sample size or measurement 
frequency.
    With respect to this DQO process, the Agency requests specific 
comment on three issues: (1) the usefulness or limitations of the DQO 
approach to protocol design; (2) the acceptable probability level of 
data quality or compliance assurance, and appropriate mathematical 
approaches for determining the probability; and (3) examples of cost-
effective protocols demonstrating a known high level of assurance of 
continuous compliance using DQO analysis principles.
    The Agency also requests comment on the possibility of using 
independent third parties to evaluate protocols proposed by sources 
particularly where a source proposes an alternative to a presumptively 
acceptable example protocol provided by EPA. The use of third parties 
could increase confidence in the protocol development and review 
process and reduce the resource burdens associated with enhanced 
monitoring protocol review and approval. The Agency is considering the 
idea of using third-party reviewers through a public/private 
partnership between the Agency and interested industrial organizations. 
The Agency has in the past relied on outside parties to streamline 
implementation of programs, such as certifying laboratories in 
connection with the certification of woodstoves with NSPS requirements 
under 40 CFR part 60, subpart AAA. The function of the third party 
organization would be to review industry-submitted protocols for a fee 
paid by the source owner submitting the protocol for review. The third 
party would provide to the source owner or operators and the permitting 
authorities an evaluation of the feasibility and acceptability of the 
protocol for specific applications. The Agency is soliciting comment on 
whether establishing a third party review process to augment permitting 
authority review and evaluation of protocols is appropriate; what would 
be a suitable structure for a third party review organization and 
process; the suitability of the industry paid fee for the third party 
review services or any alternative funding mechanism; and what 
procedures (e.g., data quality objectives analysis) would be 
appropriate to guide a third party review.
    The Agency intends to provide for input from all interested parties 
throughout the example protocol guidance development process. To assure 
that all interested parties have an opportunity to comment, EPA intends 
to publish in the Federal Register a notice of availability of example 
protocols in draft form prior to incorporating those protocols into the 
Reference Document A notice of availability of final example protocols 
would also be published in the Federal Register. In addition, the 
Agency will use its Technology Transfer Network (TTN) electronic 
bulletin board to facilitate public involvement in the development and 
review of guidance on example protocols. The Agency will make available 
through the TTN initial information on the development of example 
protocol guidance, as well as draft and final example protocols and 
other pertinent information. Regular updates to the Enhanced Monitoring 
Reference Document will be available on the TTN as well. The Agency 
anticipates updating the Enhanced Monitoring Reference Document after 
the five year phase-in period, as well as throughout the initial 
implementation period, so that it continues to reflect advances in 
monitoring techniques. The phone number for accessing the TTN is (919) 
541-5742. Persons unfamiliar with the TTN but interested in using the 
system should contact the TTN help desk at (919) 541-5384 for further 
information.

B. Timing of Implementation

    Under the proposed rule, owners or operators would be required to 
submit proposed enhanced monitoring protocols with an application for a 
title V operating permit. The approach that EPA is now considering 
would delay implementation until EPA has published a notice of 
availability of an example protocol (or protocols) for the type of 
process/pollutant combination for which a protocol is required, subject 
to the ``hammer'' provision described below. In the interim, the 
monitoring requirements in 40 CFR 70.6(a)(3) and 70.6(c) would apply.
    Following publication of the notice of availability of example 
protocol(s) for a process/pollutant combination, the time at which the 
owner or operator would be required to submit a proposed enhanced 
monitoring protocol would depend on the status of the title V operating 
permit for the applicable facility. If the initial operating permit 
application has not yet been filed for the facility, then the owner or 
operator generally would be required to include a proposed protocol in 
the initial application for an emissions unit subject to part 64 that 
includes the relevant process/pollutant combination. In some 
circumstances, notice that EPA's example protocols are available may be 
published shortly before an affected source is obligated to submit its 
permit application to the permitting authority. In such circumstances, 
the source may submit its application as scheduled and then update the 
application to include enhanced monitoring no later than 90 days after 
publication of the notice of availability.
    If the operating permit application is filed before EPA publishes 
notice of availability of example protocol(s) for a process/pollutant 
combination applicable to emissions units subject to part 64 at the 
affected source, but the permitting authority has not yet published a 
notice to request public comment on a draft permit, then the owner or 
operator would be required to update the permit application within 90 
days of publication of the example protocols(s) to address enhanced 
monitoring for the emissions units covered by the example protocol(s). 
If an application is filed and a draft permit is noticed for public 
comment before EPA publishes a notice of availability of applicable 
example protocols, then the owner or operator would not be required to 
submit a proposed protocol until the earlier of: (1) the next 
application for permit renewal; or (2) a reopening of the permit that 
involves public notice and comment that is consistent with the type of 
public notice and comment required by 40 CFR part 70 for approval of an 
enhanced monitoring protocol.
    The ``hammer'' provision would limit the duration of the phased-in 
implementation process. Where enhanced monitoring is not required for 
an affected emissions unit and applicable requirement under the 
implementation schedule outlined above, the ``hammer'' provision would 
mandate implementation of enhanced monitoring as of January 1, 2000. 
There are three different scenarios in which the ``hammer'' provision 
would apply. First, an enhanced monitoring protocol must be included 
where applicable under part 64 in any title V permit issued after the 
``hammer'' deadline, even if EPA has not issued guidance on a 
particular process/pollutant combination. Second, an existing title V 
permit that has not included an enhanced monitoring protocol required 
under part 64 because EPA has not yet issued guidance for the 
applicable process/pollutant combination would have to be reopened 
expeditiously after the January 1, 2000 deadline to incorporate 
enhanced monitoring. Finally, where an existing title V permit has not 
included an enhanced monitoring protocol because EPA has issued 
guidance only after the date of notice for public comment on the draft 
permit, the permit would have to be reopened expeditiously after the 
January 1, 2000 deadline assuming that the required enhanced monitoring 
protocol had not been approved previously during a permit renewal or 
reopening. The Agency requests comment on appropriate timeframes for 
processing permit actions where the ``hammer'' provision requires an 
expeditious reopening of an existing permit.
    The Agency believes that including this type of ``hammer'' 
provision is essential to assure that the program is implemented in a 
timely manner. This ``hammer'' provision would provide an incentive for 
all parties to facilitate the development of example protocol guidance. 
The Agency also believes that the experience gained over the next five 
years and the publication of guidance for many types of process/
pollutant combinations will facilitate effective implementation for the 
limited number of process/pollutant combinations for which the Agency 
may not develop guidance before the January 1, 2000 deadline. The 
Agency believes that guidance will be available for most affected 
emissions units before the end of this time period. The Agency requests 
comment on this ``hammer'' provision.

III. Consideration of Cost

    Many industry representatives and some other groups commented that 
the proposed rule would not allow adequate consideration of the costs 
of various monitoring approaches in selecting enhanced monitoring for a 
particular emissions unit. The Agency requests comment generally on how 
the final rule should address the issue of considering cost in the 
context of protocol selection and approval and specifically on whether 
the final rule should be clarified to allow owners or operators to 
select the least-cost monitoring protocol that can achieve the 
requirements in the rule.
    Some comments from industry representatives indicate that cost also 
should be a consideration where the only monitoring approaches that can 
meet the other part 64 criteria are not cost-effective for the 
particular emissions unit. The EPA finds this an important issue and is 
considering incorporating a more explicit role for the consideration of 
cost in the selection and approval of enhanced monitoring. In the 
notice of proposed rulemaking (NPRM), EPA discussed in numerous places 
the importance of designing an enhanced monitoring program that would 
both achieve cost-effective emissions reductions and also allow sources 
to adopt monitoring methods that would satisfy the enhanced monitoring 
standards in the most cost-effective manner. EPA thus sees the 
consideration of costs in establishing enhanced monitoring as 
consistent with the NPRM and the Clean Air Act. The Agency requests 
specific comment as to whether and how the final rule should allow the 
Agency to consider cost and effectiveness in developing guidance for 
monitoring protocols.
    The Agency also requests comment on whether the final rule should 
allow, on a case-by-case basis and upon a demonstration by the owner or 
operator that no monitoring approach that satisfies all of the part 64 
criteria is cost-effective, the owner or operator to propose a cost-
effective monitoring approach that comes as close as possible to 
achieving all the other part 64 criteria. The Agency also requests 
specific comment as to what procedures and criteria should be used by 
permitting authorities to evaluate such proposals by owners or 
operators.
    If EPA adopts this approach, EPA would define enhanced monitoring 
as representing the monitoring for determining compliance, taking cost 
and effectiveness into account. The basic purpose of Section 114(a)(3) 
and associated sections of the Clean Air Act is to require all major 
sources to conduct monitoring which will allow them to certify 
continuous or intermittent compliance. However, nothing in Section 
114(a)(3) dictates that all sources must certify to being in either 
continuous compliance or else be considered in noncompliance; sources 
may also certify to being in compliance as demonstrated on an 
intermittent basis. For example, by virtue of consideration of cost (or 
because the emissions unit is below the applicability threshold for 
part 64) a source may not have monitoring data that is sufficient to 
support a certification of continuous compliance but does provide the 
basis for certification on an intermittent basis. EPA emphasizes that a 
certification of intermittent compliance does not mean that a source 
has operated in violation of applicable requirements. Rather, it merely 
reflects the fact that under some enhanced monitoring protocols, a 
source will only be able to gather enough data to certify compliance on 
an intermittent basis. In order to ensure effective implementation of 
enhanced monitoring and to minimize the burden on the operating permits 
program, any approach related to protocol cost would, in EPA's view, 
need to allow the permitting authority to make an expeditious 
determination based on simple, direct criteria.

IV. Special Applicability for Nonattainment Areas and Incorporation of 
Periodic Monitoring

    Many industry representatives and several State and local agencies 
commented that the proposed applicability of the rule covered too many 
sources and emissions units, especially too many small emissions units. 
Environmental groups commented that the proposed applicability was too 
narrow and criticized any reduction in applicability. In response to 
these comments, the Agency solicits comment on whether it would be 
appropriate to have a second phase of applicability only for 
nonattainment pollutants in nonattainment areas.
    The Agency is considering applying part 64 primarily to emissions 
units which emit, or have the potential to emit, a pollutant at or 
above the applicable major source threshold, as defined under title V 
of the Act. This approach would have the effect of significantly 
reducing the number of sources and emissions units subject to part 64. 
To address concerns that environmentally significant emissions units 
would not be covered, the EPA is also considering the appropriateness 
of a second phase of applicability, only for nonattainment pollutants 
in nonattainment areas, in which all major sources which are major for 
a nonattainment pollutant would be required to cover a prescribed 
minimum percentage of their emissions units, perhaps with a de minimis 
cutoff for very small units.
    In such a second phase, part 64 could require each major source 
which is located in a nonattainment area and major for a nonattainment 
pollutant to conduct enhanced monitoring on at least 25% of its 
emissions units that are subject to applicable requirements for the 
nonattainment pollutant, except that it would not have to conduct 
enhanced monitoring for that pollutant on any emissions unit which 
emits, and has the potential to emit, less than 50% of the applicable 
major source threshold. Emissions units would be selected for coverage 
as part of the 25% requirement based on the potential to emit of the 
units, with the largest selected first. Any emissions units already 
required to conduct enhanced monitoring under the regular, first phase 
of implementation would ``count'' toward the 25%.
    The EPA believes that this second phase of applicability is 
appropriate as a means of ensuring that emissions units that have the 
potential to contribute significantly to nonattainment problems are 
subject to enhanced monitoring while at the same time excluding the 
smallest emissions units.
    The EPA solicits comment on the appropriateness of requiring such a 
second phase only in nonattainment areas (i.e., not in attainment 
areas); the appropriate percentage threshold to use; whether and at 
what level a de minimis level should be used to exclude small emissions 
units; when and how such a second phase should be implemented in 
connection with the title V permitting process; and on all other 
aspects of such a second phase in nonattainment areas. After reviewing 
any comments received, EPA may proceed to finally promulgate a second 
phase without further opportunity to comment.
    The EPA realizes that the applicability approach described above 
may still leave some major sources with no emissions units subject to 
enhanced monitoring requirements in part 64. To satisfy the statutory 
obligation that all major stationary sources conduct enhanced 
monitoring, the preamble to the proposed rule stated EPA's intent to 
rely on periodic monitoring under 40 CFR part 70 as sufficiently 
enhanced for small units under the size threshold proposed by EPA. The 
Agency also requested comment on the possibility of relying upon a de 
minimis exemption theory as allowed under Alabama Power v. Costle, 636 
F.2d 323 (D.C. Cir. 1979).
    Accordingly, EPA solicits comment on the appropriateness of relying 
in part on periodic monitoring under 40 CFR part 70 to satisfy the 
Agency's obligation to require enhanced monitoring for all major 
sources.
    The Agency also solicits comment on whether to codify this link 
between enhanced and periodic monitoring by specifically including the 
rule language from 40 CFR 70.6(a)(3)(i) into a separate subpart of part 
64. A separate subpart of part 64 could provide that at a major source, 
for all emissions units and applicable requirements that do not meet 
the applicability thresholds for the enhanced monitoring requirements 
discussed in the proposed rule and in this notice, the source must 
conduct monitoring, to the extent necessary to comply with 40 CFR 
70.6(a)(3)(i) and 70.6(c)(1) and (5), that is periodic monitoring 
sufficient to yield reliable data from the relevant time period that 
are representative of the source's compliance with the permit. Such 
monitoring requirements would be required to assure use of terms, test 
methods, units, averaging periods, and other statistical conventions 
consistent with the applicable requirement.
    Such a codification of existing part 70 language into part 64 would 
not be intended to alter, or add to, the existing part 70 monitoring 
requirements. Rather, this codification would merely make clear that 
EPA considers existing periodic monitoring requirements as partial 
fulfillment of its obligation to require enhanced monitoring for all 
major sources.
    Finally, in a separate section above, the Agency discusses the 
potential role of cost in selecting enhanced monitoring. In this 
context, EPA may also consider periodic monitoring approaches under 
certain circumstances as one of the ways of achieving more cost-
effective monitoring approaches.

    Dated: December 20, 1994.
Carol M. Browner,
Administrator, U.S. Environmental Protection Agency.
[FR Doc. 94-31742 Filed 12-27-94; 8:45 am]
BILLING CODE 6560-50-P