GUIDELINE SERIES
GUIDANCE FOR REGIONAL
LIMITATION DETERMINATIONS
UNDER ESECA
OAQPS No. 1.2 - OSS
Hit UK - A* Hk
UM
I.S. ENVIRONMENTAL PROTECTION AGENCY
Offi«T o! Air and Wasle Management
Office of Air Quality Planning and Standards
Research Triangle Park, North Carolina 27711
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15482
GUIDANCE FOR
REGIONAL LIMITATION DETERMINATIONS
UNDER ESECA
July 1975
OAQPS Number 1.2 - 033
U.S. ENVIRONMENTAL PROTECTION AGENCY
Monitoring and Data Analysis Division
and
Strategies and Air Standards Division
Office of Air Quality Planning and Standards
Research Triangle Park, North Carolina
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TABLE OF CONTENTS
Page
I. Introduction and Background 1
II. Regional Limitation Evaluation 2
A. General 2
B. Monitoring Types and Distribution 3
C. Data Interpretation 5
III. Reevaluation of a Regional Limitation
Finding
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INTRODUCTION AND BACKGROUND
The purpose of this guideline is to provide the Regional Offices
(RO) with procedures for the determination of AQCR Regional Limitation
status as required by Section 119(c)(2)(D) of the Clean Air Act, a part
of the Energy Supply and Environmental Coordination Act of 1974 (ESECA).
The ESECA is designed to promote greater reliance on our domestic
coal supplies over the long term. Furthermore, it is the stated pur-
pose of the Act that these efforts shall be ". . . consistent, to the
fullest extent practicable, with existing national commitments to protect
and'improve the environment." To carry out these purposes, the Act (1)
authorizes the Federal Energy Administration to prohibit major fuel burn-
ing sources, primarily power plants, from burning oil or gas, thereby
requiring the conversion to coal; and (2) authorizes the Environmental
Protection Agency to apply environmental requirements to these sources.
Where a Regional Limitation does not apply, EPA has authority to
grant converting sources compliance date extensions (CDE) pertinent to
existing applicable air pollution control requirements. For the period
of the CDE, EPA may require only such control of emissions as is neces-
sary to assure that national primary ambient air quality standards
(NPAAQS) are met; this required control is called primary standard con-
ditions (PSC). A Regional Limitation applies if a converting source is
located in an air quality control region in which a national primary
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ambient air quality standard for a pollutant is not being met. Where
a Regional Limitation applies, EPA cannot authorize the source to emit
such pollutant in amounts which exceed that permitted under the existing
applicable air pollution control requirements, i.e., EPA cannot grant
the source a CDE for that pollutant and prescribe primary standard con-
ditions.
According to the Conference Committee Report on ESECA (No. 93-1085,
page 34), a Regional Limitation applies to a source if a NPAAQS is not
being met at any location within the AQCR in which the source is located;
the determination of applicability of a Regional Limitation is not depend-
ent on showing any relationship between the source's emissions and the
measured air quality.
EPA actions regarding determination and application of the Regional
Limitation are reviewable in the United States Court of Appeals for the ap-
propriate circuit under Section 307(b) of the Clean Air Act. The Regional
Limitation is enforceable under citizen suit provisions (Section 304) of
the Clean Air Act and may also be enforced by the appropriate state or
locality under Section 119(d)(4) of the Clean Air Act.
II. REGIONAL LIMITATION EVALUATION
A. General
After consideration of comments received from RO's on previous drafts
of this guideline, we are recommending that, except when the uncertainties
discussed below warrant additional consideration, air quality data be
treated literally without regard to the effects of different sampling fre-
quencies, statistical sampling errors, or routine collection and
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measurement errors known to affect the results of any particular air
sample. Under this approach, the Regional Limitation will apply wherever
there is found to be a level of pollutant concentrations in excess of the
NPAAQS. The purpose is to minimize the possible confusion in the inter-
pretation and reporting of monitoring data, particularly as these data
are compared with NPAAQS. EPA follows these recommendations in reporting
air quality in publications such as the 1973 Monitoring and Air Quality
Trends Reports.
The guidance provided in this section is intended to provide a
general framework within which to consider air quality uncertainties
but does not attempt to provide precise decision rules. In cases where
the air quality is of uncertain status, it is recommended that the RO's
carefully consider all of the relevant factors including the degree of data
adequacy, the appropriateness of the monitoring network, and the frequency
and intensity of concentrations approaching or exceeding the NAAQS.
B. Monitoring Types and Distribution
The types .and distribution of monitors within an AQCR are major
factors in evaluation of regional air quality. A list of approved
instruments is presented in Table 1, which is extracted from OAQPS
Guideline #1.2 - 018. Since there are no approved continuous S02 in-
struments available at this time, any instrument utilizing the principles
of operation listed in the unapproved category could be used.in the
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Pollutant Code
TABLE
STATUS OF AIR MONITORING METHODS
Method
Approved Unapproved Unacceptable Type
TSP 11101 91 Hi-Vol (FRM)
S02 42401 11 Colorimetric
13 Conductimetric
14 Coulometric
15 Autometerc
16 Flame Photometric
31 Hydrogen Peroxide0
33 Sequential Conduc-
timetric
91 West-Gaeke-Sulfamic
Acid (FRM)
92 West-Gaeke Bubbler
93 Conductimetric
Bubbler
X
X
X
x
xc
X
xc
X
I
c
c
c
c
c
c
c
X
X
FRM - Federal Reference Method.
See OAQPS Guideline #1.2 - 018 for explanation.
c These methods should be reported under method
code 42401 13.
I - Intermittent, C - continuous
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Regional Limitation decision-making process. As EPA gathers additional
data on the acceptability of the continuous S02 instruments, the list
will be revised and notice published in the Federal Register. Unaccept-
able monitors should not be used unless they are unacceptable because .
of an interferent that is known to affect instrument performance and are
located in areas where the interferent does not exist. The documentation
that known interferents do not exist in concentrations significant
enough to affect performance would be the responsibility of the operator
of the monitor. Such documentation must be available to the RO before
using data from such monitors for Regional Limitation purposes. This is
necessary to support Regional Limitation determination in case of legal
challenge.
The location of monitors in the existing network should have been
reviewed to determine if areas of expected maximum concentration (hot
spots) are being sampled as well as areas of expected impact from the af-
fected source. It is not recommended, however, that determinations of
Regional Limitations be deferred until additional monitors are installed
and additional data are available. In addition to the States' monitoring,
some utilities and private institutions are collecting monitoring data.
Much of this type of monitoring is being collected by EPA reference
methods; however, much is being collected with sampling equipment which
EPA has not fully evaluated. It is recommended that these data be sup-
ported by a certification of the procedures used in the collection and
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analysis of the samples and the validation of the data, especially in
instances where individual data points (such as a 24-hour average con-
centration) define a Regional Limitation.
OAQPS and ORD/RTP have issued several guideline documents on air
quality data validation and quality control procedures. These guideline
reports should be consulted for the appropriate procedures to use. This
guidance includes:
1. OAQPS #1.2 - 006 Guidelines for Evaluation of Suspect
. Air Quality Data
2. OAQPS #1.2 - 012 Guidance for Air Quality Monitoring
Network Design and Instrument Siting
3. OAQPS #1.2 - 013 Procedures for Flow and Auditing of
Air Quality Data
4. OAQPS #1.2 - 015 Guidelines for the Evaluation of Air
Quality Data
5. OAQPS #1.2 - 019 Air Quality Monitoring Site Description
Guideline
6. Guidelines for Development of a Quality Assurance Program.
EPA-R4-73-028 (a through d)
C. Data Interpretation
It is recommended that data review be focused on identifying the
AQCRs in which a NPAAQS is not being met. If the available data are
not sufficiently complete (see suggested criteria below) to support such
a finding, then a finding of "no Regional Limitation" is recommended.
Such a finding would not lead to contravention of NPAAQS since primary
standard conditions must be specified for any source granted a compliance
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date extension, and deferring a decision on RL applicability until
sufficiently complete data become available could lead to unwarranted
delays in the coal conversion program. Data completeness is particular-
ly important in determining where the long-term NPAAQS is not being met.
Currency of the measured air quality data is an important considera-
tion. Ideally, data covering the 12-month period immediately prior to
making a determination of RL applicability should be used, but time is
needed for data reduction and validation. It is recommended that data
representing the most recent four calendar quarters be used for comparing
concentrations with the NPAAQS. Where this is not possible, a determina-
tion that a NPAAQS is not being met that is based on older data should be
fully explained.
Contravention of the short-term standards should be closely examined.
If the contravention resulted from a circumstance not likely to be repeat-
ed, e.g., from nearby construction since completed, then a finding of "no
Regional Limitation" is suggested.
For calculating concentrations to determine whether long-term
standards are being met, the following criteria for data completeness are
recommended:
t
1. For continuous monitors, between 60-75 percent of the
possible observations should be available to compute quarterly
or annual statistical summaries. For purposes of computations,
this criteria will be met when the number of hourly observations
equals or exceeds 1314.
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2. For intermittent monitors, between 60-75 percent of the
scheduled observations should be available to compute quarterly
or annual statistical summaries. For minimum sampling (once
in six days: see 40 CRF 51.17) this would correspond to
approximately 36 to 46 scheduled samples properly distributed
within a four quarter period.
These criteria are presented as suggested guidance for use in a
Regional Limitation determination. Data from air monitoring sites
could be used even though the condition in (1) and (2) are not met
if, in the judgment of the Regional Office, the data are valid and
are sufficient to provide a representative statistical sample.
Justification for different criteria should be documented for review
purposes.
III. REEVALUATION OF A REGIONAL LIMITATION FINDING
The status of air quality fluctuates from one quarter to the
next because of factors such as meteorology, sampling frequency,
and additional site reporting. In some AQCRs, pollutant concentra-
tions may vary between exceeding and meeting the NPAAQS. An un-
stable Regional Limitation status would have undesirable program-
matic and economic consequences with CDEs being withdrawn and re-
instituted, required emission controls varying between SIP and PSC,
and fuel contracts constantly changing.
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It is recommended that a finding of "no Regional Limitation" not
be reversed after a source has been granted a compliance date extension
and authorized to operate under relaxed emission control provided by
primary standard conditions. Public health would not be jeopardized by
this position. If contravention of a standard were to occur, wholly or
in part as a result of the source's emissions, then ESECA requires that
the primary standard conditions be made more stringent. If the source's
emissions played no part in the contravention of the standard, then re-
voking the CDE and PSC would not help to reduce the excessive concentra-
tions.
Reevaluation of a finding which applied a Regional Limitation may
be appropriate if subsequent data indicate that a Regional Limitation no
longer applies. This action would cause no contravention of the NPAAQS
and could, because of the less stringent control required by PSC, allow
the source to burn coal while preparing to meet the implementation plan re-
quirements at the expiration of the CDE. The ESECA Conference Committee
Report supports this type of revaluation. In explaining the Regional
Limitation provision and presenting examples of its application, the Report
reads, "Moreover, if at any subsequent time it is determined that the
national primary standard for particulates is being attained in this
region, then such source would no longer subject to the regional limita-
tion" (but of course would continue to be subject to all primary standard
conditions).
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