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 ------- 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 ------- 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 ------- 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 ------- 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 ------- 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 ------- 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 ------- 4 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 ------- 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 ------- 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. ------- 7 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. ------- 8 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). ------- |