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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                                          2
    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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                                      3



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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                                      5
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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                                      6

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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