40 CFR Part 58 — Ambient Air Quality Surveillance

PART 58—AMBIENT AIR QUALITY SURVEILLANCE Authority: 42 U.S.C. 7403, 7405, 7410, 7414, 7601, 7611, 7614, and 7619. Source: 44 FR 27571, May 10, 1979; 59 FR 41628, Aug. 12, 1994, unless otherwise noted. Subpart A—General Provisions Source: 71 FR 61296, Oct. 17, 2006, unless otherwise noted. § 58.1 Definitions. As used in this part, all terms not defined herein have the meaning given them in the Clean Air Act. AADT Act et seq. Additive and multiplicative bias Administrator Air quality system (AQS) AQCR Area-wide Certifying agency Chemical Speciation Network (CSN) CO Combined statistical area (CSA) Core-based statistical area (CBSA) Corrected concentration Design value EDO Effective concentration Federal equivalent method (FEM) Federal reference method (FRM) HNO 3 Implementation plan Local agency Meteorological measurements Metropolitan Statistical Area (MSA) Monitor Monitoring agency Monitoring organization Monitoring path Monitoring path length optical measurement path length. Monitoring planning area (MPA) 2.5. NATTS NCore 2.5 2.5 10-2.5 3 2 y Near-road monitor 2.5 2 Network Network Plan NH 3 NO 2 NO NO X 2 NO y 2, Z. O 3 Open path analyzer Optical measurement path length (1) Equal to the monitoring path length for a (bistatic) system having a transmitter and a receiver at opposite ends of the monitoring path; (2) Equal to twice the monitoring path length for a (monostatic) system having a transmitter and receiver at one end of the monitoring path and a mirror or retroreflector at the other end; or (3) Equal to some multiple of the monitoring path length for more complex systems having multiple passes of the measurement beam through the monitoring path. PAMS Pb PM 10 10C 2.5 10-2.5 PM 2.5 PM 10 PM 10C PM 10−2.5 Point analyzer Primary monitor Primary quality assurance organization Probe PSD monitoring network PSD monitoring organization PSD reviewing authority PSD station Regional Administrator Reporting organization Site SLAMS SO 2 Special purpose monitor (SPM) State agency Station STN 2.5 Supplemental speciation station 2.5 Traceable TSP Urbanized area VOCs [81 FR 17276, Mar. 28, 2016, as amended at 89 FR 16388, Mar. 6, 2024] § 58.2 Purpose. (a) This part contains requirements for measuring ambient air quality and for reporting ambient air quality data and related information. The monitoring criteria pertain to the following areas: (1) Quality assurance procedures for monitor operation and data handling. (2) Methodology used in monitoring stations. (3) Operating schedule. (4) Siting parameters for instruments or instrument probes. (5) Minimum ambient air quality monitoring network requirements used to provide support to the State implementation plans (SIP), national air quality assessments, and policy decisions. These minimums are described as part of the network design requirements, including minimum numbers and placement of monitors of each type. (6) Air quality data reporting, and requirements for the daily reporting of an index of ambient air quality. (b) The requirements pertaining to provisions for an air quality surveillance system in the SIP are contained in this part. (c) This part also acts to establish a national ambient air quality monitoring network for the purpose of providing timely air quality data upon which to base national assessments and policy decisions. § 58.3 Applicability. This part applies to: (a) State air pollution control agencies. (b) Any local air pollution control agency to which the State has delegated authority to operate a portion of the State's SLAMS network. (c) Owners or operators of proposed sources. Subpart B—Monitoring Network Source: 71 FR 61298, Oct. 17, 2006, unless otherwise noted. § 58.10 Annual monitoring network plan and periodic network assessment. (a)(1) Beginning July 1, 2007, the State, or where applicable local, agency shall submit to the Regional Administrator an annual monitoring network plan which shall provide for the documentation of the establishment and maintenance of an air quality surveillance system that consists of a network of SLAMS monitoring stations that can include FRM and FEM monitors that are part of SLAMS, NCore, CSN, PAMS, and SPM stations. The plan shall include a statement of whether the operation of each monitor meets the requirements of appendices A, B, C, D, and E to this part, where applicable. The Regional Administrator may require additional information in support of this statement. The annual monitoring network plan must be made available for public inspection and comment for at least 30 days prior to submission to the EPA and the submitted plan shall include and address, as appropriate, any received comments. (2) Any annual monitoring network plan that proposes network modifications (including new or discontinued monitoring sites, new determinations that data are not of sufficient quality to be compared to the NAAQS, and changes in identification of monitors as suitable or not suitable for comparison against the annual PM 2.5 (3) The plan for establishing required NCore multipollutant stations shall be submitted to the Administrator not later than July 1, 2009. The plan shall provide for all required stations to be operational by January 1, 2011. (4) A plan for establishing source-oriented Pb monitoring sites in accordance with the requirements of appendix D to this part for Pb sources emitting 1.0 tpy or greater shall be submitted to the EPA Regional Administrator no later than July 1, 2009, as part of the annual network plan required in paragraph (a)(1) of this section. The plan shall provide for the required source-oriented Pb monitoring sites for Pb sources emitting 1.0 tpy or greater to be operational by January 1, 2010. A plan for establishing source-oriented Pb monitoring sites in accordance with the requirements of appendix D to this part for Pb sources emitting equal to or greater than 0.50 tpy but less than 1.0 tpy shall be submitted to the EPA Regional Administrator no later than July 1, 2011. The plan shall provide for the required source-oriented Pb monitoring sites for Pb sources emitting equal to or greater than 0.50 tpy but less than 1.0 tpy to be operational by December 27, 2011. (5)(i) A plan for establishing or identifying an area-wide NO 2 (ii) A plan for establishing or identifying any NO 2 (iii) A plan for establishing a single near-road NO 2 (iv) A plan for establishing a second near-road NO 2 (6) A plan for establishing SO 2 2 (7) A plan for establishing CO monitoring sites in accordance with the requirements of appendix D to this part shall be submitted to the EPA Regional Administrator. Plans for required CO monitors shall be submitted at least six months prior to the date such monitors must be established as required by section 58.13. (8)(i) A plan for establishing near-road PM 2.5 (ii) A plan for establishing near-road PM 2.5 (9) The annual monitoring network plan shall provide for the required O 3 3 (10) A plan for making Photochemical Assessment Monitoring Stations (PAMS) measurements, if applicable, in accordance with the requirements of appendix D paragraph 5(a) of this part shall be submitted to the EPA Regional Administrator no later than July 1, 2018. The plan shall provide for the required PAMS measurements to begin by June 1, 2019. (11) An Enhanced Monitoring Plan for O 3 3 (12) A detailed description of the PAMS network being operated in accordance with the requirements of appendix D to this part shall be submitted as part of the annual monitoring network plan for review by the EPA Administrator. The PAMS Network Description described in section 5 of appendix D may be used to meet this requirement. (b) The annual monitoring network plan must contain the following information for each existing and proposed site: (1) The AQS site identification number. (2) The location, including street address and geographical coordinates. (3) The sampling and analysis method(s) for each measured parameter. (4) The operating schedules for each monitor. (5) Any proposals to remove or move a monitoring station within a period of 18 months following plan submittal. (6) The monitoring objective and spatial scale of representativeness for each monitor as defined in appendix D to this part. (7) The identification of any sites that are suitable and sites that are not suitable for comparison against the annual PM 2.5 (8) The MSA, CBSA, CSA or other area represented by the monitor. (9) The designation of any Pb monitors as either source-oriented or non-source-oriented according to Appendix D to 40 CFR part 58. (10) Any monitors for which a waiver has been requested or granted by the EPA Regional Administrator as allowed for under appendix D or appendix E to this part. For those monitors where a waiver has been approved, the annual monitoring network plan shall include the date the waiver was approved. (11) Any source-oriented or non-source-oriented site for which a waiver has been requested or granted by the EPA Regional Administrator for the use of Pb-PM 10 (12) The identification of required NO 2 (13) The identification of any PM 2.5 2.5 2.5 (14) The identification of any site(s) intended to address being sited in an at-risk community where there are anticipated effects from sources in the area as required in section 4.7.1(b)(3) of appendix D to this part. An initial approach to the question of whether any new or moved sites are needed and to identify the communities in which they intend to add monitoring for meeting the requirement in this paragraph (b)(14), if applicable, shall be submitted in accordance with the requirements of section 4.7.1(b)(3) of appendix D to this part, which includes submission to the EPA Regional Administrator no later than July 1, 2024. Specifics on the resulting proposed new or moved sites for PM 2.5 (c) The annual monitoring network plan must document how state and local agencies provide for the review of changes to a PM 2.5 2.5 (d) The State, or where applicable local, agency shall perform and submit to the EPA Regional Administrator an assessment of the air quality surveillance system every 5 years to determine, at a minimum, if the network meets the monitoring objectives defined in appendix D to this part, whether new sites are needed, whether existing sites are no longer needed and can be terminated, and whether new technologies are appropriate for incorporation into the ambient air monitoring network. The network assessment must consider the ability of existing and proposed sites to support air quality characterization for areas with relatively high populations of susceptible individuals ( e.g., (e) All proposed additions and discontinuations of SLAMS monitors in annual monitoring network plans and periodic network assessments are subject to approval according to § 58.14. [71 FR 61298, Oct. 17, 2006, as amended at 72 FR 32210, June 12, 2007; 73 FR 67059, Nov. 12, 2008; 73 FR 77517, Dec. 19, 2008; 75 FR 6534, Feb. 9, 2010; 75 FR 35601, June 22, 2010; 75 FR 81137, Dec. 27, 2010; 76 FR 54341, Aug. 31, 2011; 78 FR 16188, Mar. 14, 2013; 78 FR 3282, Jan. 15, 2013; 80 FR 65466, Oct. 26, 2015; 81 FR 17279, Mar. 28, 2016; 81 FR 96388, Dec. 30, 2016; 89 FR 16388, Mar. 6, 2024] § 58.11 Network technical requirements. (a)(1) State and local governments shall follow the applicable quality assurance criteria contained in appendix A to this part when operating the SLAMS networks. (2) Beginning January 1, 2009, State and local governments shall follow the quality assurance criteria contained in appendix A to this part that apply to SPM sites when operating any SPM site which uses an FRM or an FEM and meets the requirements of appendix E to this part, unless the Regional Administrator approves an alternative to the requirements of appendix A with respect to such SPM sites because meeting those requirements would be physically and/or financially impractical due to physical conditions at the monitoring site and the requirements are not essential to achieving the intended data objectives of the SPM site. Alternatives to the requirements of appendix A may be approved for an SPM site as part of the approval of the annual monitoring plan, or separately. (3) The owner or operator of an existing or a proposed source shall follow the quality assurance criteria in appendix B to this part that apply to PSD monitoring when operating a PSD site. (b) State and local governments must follow the criteria in appendix C to this part to determine acceptable monitoring methods or instruments for use in SLAMS networks. Appendix C criteria are optional at SPM stations. (c) State and local governments must follow the network design criteria contained in appendix D to this part in designing and maintaining the SLAMS stations. The final network design and all changes in design are subject to approval of the Regional Administrator. NCore and STN network design and changes are also subject to approval of the Administrator. Changes in SPM stations do not require approvals, but a change in the designation of a monitoring site from SLAMS to SPM requires approval of the Regional Administrator. (d) State and local governments must follow the criteria contained in appendix E to this part for siting monitor inlets, paths or probes at SLAMS stations. Appendix E adherence is optional for SPM stations. (e) State and local governments must assess data from Class III PM 2.5 2.5 (1) The acceptable concentration range (Rj), µg/m 3 3 (2) The minimum number of test sites shall be at least one; however, the number of test sites will generally include all locations within an agency's network with collocated FRMs and FEMs. (3) The minimum number of methods shall include at least one FRM and at least one FEM. (4) Since multiple FRMs and FEMs may not be present at each site, the precision statistic requirement does not apply, even if precision data are available. (5) All seasons must be covered with no more than 36 consecutive months of data in total aggregated together. (6) The key statistical metric to include in an assessment is the bias (both additive and multiplicative) of the PM 2.5 [71 FR 61298, Oct. 17, 2006, as amended at 78 FR 3282, Jan. 15, 2013; 80 FR 65466, Oct. 26, 2015; 81 FR 17279, Mar. 28, 2016; 89 FR 16389, Mar. 6, 2024] § 58.12 Operating schedules. State and local governments shall collect ambient air quality data at any SLAMS station on the following operational schedules: (a) For continuous analyzers, consecutive hourly averages must be collected except during: (1) Periods of routine maintenance, (2) Periods of instrument calibration, or (3) Periods or monitoring seasons exempted by the Regional Administrator. (b) For Pb manual methods, at least one 24-hour sample must be collected every 6 days except during periods or seasons exempted by the Regional Administrator. (c) For PAMS VOC samplers, samples must be collected as specified in section 5 of appendix D to this part. Area-specific PAMS operating schedules must be included as part of the PAMS network description and must be approved by the Regional Administrator. (d) For manual PM 2.5 (1)(i) Manual PM 2.5 2.5 (ii) For SLAMS PM 2.5 2.5 2.5 2.5 2.5 2.5 2.5 (iii) Required SLAMS stations whose measurements determine the 24-hour design value for their area and whose data are within plus or minus 5 percent of the level of the 24-hour PM 2.5 2.5 2.5 (iv) Changes in sampling frequency attributable to changes in design values shall be implemented no later than January 1 of the calendar year following the certification of such data as described in § 58.15. (2) Manual PM 2.5 (3) Manual PM 2.5 (e) For PM 10 10 10 (f) For manual PM 10-2.5 (1) Manual PM 10-2.5 10-2.5 (2) [Reserved] (g) For continuous SO 2 [71 FR 61298, Oct. 17, 2006, as amended at 72 FR 32210, June 12, 2007; 75 FR 35601, June 22, 2010; 78 FR 3282, Jan. 15, 2013; 81 FR 17279, Mar. 28, 2016; 89 FR 16389, Mar. 6, 2024] § 58.13 Monitoring network completion. (a) The network of NCore multipollutant sites must be physically established no later than January 1, 2011, and at that time, operating under all of the requirements of this part, including the requirements of appendices A, C, D, E, and G to this part. NCore sites required to conduct Pb monitoring as required under 40 CFR part 58 appendix D paragraph 3(b), or approved alternative non-source-oriented Pb monitoring sites, shall begin Pb monitoring in accordance with all of the requirements of this part, including the requirements of appendices A, C, D, E, and G to this part no later than December 27, 2011. (b) Not withstanding specific dates included in this part, beginning January 1, 2008, when existing networks are not in conformance with the minimum number of required monitors specified in this part, additional required monitors must be identified in the next applicable annual monitoring network plan, with monitoring operation beginning by January 1 of the following year. To allow sufficient time to prepare and comment on Annual Monitoring Network Plans, only monitoring requirements effective 120 days prior to the required submission date of the plan (i.e., 120 days prior to July 1 of each year) shall be included in that year's annual monitoring network plan. (c) The NO 2 (1) January 1, 2013, for area-wide NO 2 (2) January 1, 2013, for NO 2 (3) January 1, 2014, for an initial near-road NO 2 (4) January 1, 2015, for a second near-road NO 2 (d) The network of SO 2 (e) The CO monitors required under Appendix D, section 4.2 of this part must be physically established and operating under all of the requirements of this part, including the requirements of appendices A, C, D, and E to this part, no later than: (1) January 1, 2015 for CO monitors in CBSAs having 2.5 million persons or more; or (2) January 1, 2017 for other CO monitors. (f) PM 2.5 (1) January 1, 2015 for PM 2.5 (2) January 1, 2017 for PM 2.5 (g) The O 3 3 (h) The Photochemical Assessment Monitoring sites required under appendix D of this part, section 5(a), must be physically established and operating under all of the requirements of this part, including the requirements of appendix A, C, D, and E of this part, no later than June 1, 2021. [71 FR 61298, Oct. 17, 2006, as amended at 73 FR 67059, Nov. 12, 2008; 75 FR 6534, Feb. 9, 2010; 75 FR 35601, June 22, 2010; 75 FR 81137, Dec. 27, 2010; 76 FR 54341, Aug. 31, 2011; 78 FR 16188, Mar. 14, 2013; 78 FR 3283, Jan. 15, 2013; 80 FR 65466, Oct. 26, 2015; 81 FR 96388, Dec. 30, 2016; 85 FR 837, Jan. 8, 2020] § 58.14 System modification. (a) The state, or where appropriate local, agency shall develop a network modification plan and schedule to modify the ambient air quality monitoring network that addresses the findings of the network assessment required every 5 years by § 58.10(d). The network modification plan shall be submitted as part of the Annual Monitoring Network Plan that is due no later than the year after submittal of the network assessment. (b) Nothing in this section shall preclude the State, or where appropriate local, agency from making modifications to the SLAMS network for reasons other than those resulting from the periodic network assessments. These modifications must be reviewed and approved by the Regional Administrator. Each monitoring network may make or be required to make changes between the 5-year assessment periods, including for example, site relocations or the addition of PAMS networks in bumped-up ozone nonattainment areas. These modifications must address changes invoked by a new census and changes due to changing air quality levels. The State, or where appropriate local, agency shall provide written communication describing the network changes to the Regional Administrator for review and approval as these changes are identified. (c) State, or where appropriate, local agency requests for SLAMS monitor station discontinuation, subject to the review of the Regional Administrator, will be approved if any of the following criteria are met and if the requirements of appendix D to this part, if any, continue to be met. Other requests for discontinuation may also be approved on a case-by-case basis if discontinuance does not compromise data collection needed for implementation of a NAAQS and if the requirements of appendix D to this part, if any, continue to be met. (1) Any PM 2.5 3 10 2 2 (2) Any SLAMS monitor for CO, PM 10 2 2 (3) For any pollutant, any SLAMS monitor in a county (or portion of a county within a distinct attainment, nonattainment, or maintenance area, as applicable) provided the monitor has not measured violations of the applicable NAAQS in the previous five years, and the approved SIP provides for a specific, reproducible approach to representing the air quality of the affected county in the absence of actual monitoring data. (4) A PM 2.5 (5) A SLAMS monitor that is designed to measure concentrations upwind of an urban area for purposes of characterizing transport into the area and that has not recorded violations of the relevant NAAQS in the previous five years, if discontinuation of the monitor is tied to start-up of another station also characterizing transport. (6) A SLAMS monitor not eligible for removal under any of the criteria in paragraphs (c)(1) through (c)(5) of this section may be moved to a nearby location with the same scale of representation if logistical problems beyond the State's control make it impossible to continue operation at its current site. [71 FR 61298, Oct. 17, 2006, as amended at 81 FR 17280, Mar. 28, 2016] § 58.15 Annual air monitoring data certification. (a) The State, or where appropriate local, agency shall submit to the EPA Regional Administrator an annual air monitoring data certification letter to certify data collected by FRM and FEM monitors at SLAMS and SPM sites that meet criteria in appendix A to this part from January 1 to December 31 of the previous year. The head official in each monitoring agency, or his or her designee, shall certify that the previous year of ambient concentration and quality assurance data are completely submitted to AQS and that the ambient concentration data are accurate to the best of her or his knowledge, taking into consideration the quality assurance findings. The annual data certification letter is due by May 1 of each year. (b) Along with each certification letter, the State shall submit to the Regional Administrator an annual summary report of all the ambient air quality data collected by FRM and FEM monitors at SLAMS and SPM sites. The annual report(s) shall be submitted for data collected from January 1 to December 31 of the previous year. The annual summary serves as the record of the specific data that is the object of the certification letter. (c) Along with each certification letter, the State shall submit to the Regional Administrator a summary of the precision and accuracy data for all ambient air quality data collected by FRM and FEM monitors at SLAMS and SPM sites. The summary of precision and accuracy shall be submitted for data collected from January 1 to December 31 of the previous year. [89 FR 16389, Mar. 6, 2024] § 58.16 Data submittal and archiving requirements. (a) The state, or where appropriate, local agency, shall report to the Administrator, via AQS all ambient air quality data and associated quality assurance data for SO 2 3 2 y X 10 10 2.5 2.5 2.5 10-2.5 https://www.epa.gov/sites/production/files/2015-09/documents/aqs_data_coding_manual_0.pdf (b) The specific quarterly reporting periods are January 1-March 31, April 1-June 30, July 1-September 30, and October 1-December 31. The data and information reported for each reporting period must contain all data and information gathered during the reporting period, and be received in the AQS within 90 days after the end of the quarterly reporting period. For example, the data for the reporting period January 1-March 31 are due on or before June 30 of that year. (c) Air quality data submitted for each reporting period must be edited, validated, and entered into the AQS (within the time limits specified in paragraphs (b) and (d) of this section) pursuant to appropriate AQS procedures. The procedures for editing and validating data are described in the AQS Data Coding Manual and in each monitoring agency's quality assurance project plan. (d) The state shall report VOC and if collected, carbonyl, NH 3 3 2.5 (e) The State shall also submit any portion or all of the SLAMS and SPM data to the appropriate Regional Administrator upon request. (f) The state, or where applicable, local agency shall archive all PM 2.5 10 10-2.5 (g) Any State or, where applicable, local agency operating a continuous SO 2 2 2 [71 FR 61298, Oct. 17, 2006, as amended at 73 FR 67059, Nov. 12, 2008; 75 FR 6534, Feb. 9, 2010; 75 FR 35602, June 22, 2010; 78 FR 3283, Jan. 15, 2013; 81 FR 17280, Mar. 28, 2016] Subpart C—Special Purpose Monitors Source: 71 FR 61302, Oct. 17, 2006, unless otherwise noted. § 58.20 Special purpose monitors (SPM). (a) An SPM is defined as any monitor included in an agency's monitoring network that the agency has designated as a special purpose monitor in its annual monitoring network plan and in AQS, and which the agency does not count when showing compliance with the minimum requirements of this subpart for the number and siting of monitors of various types. Any SPM operated by an air monitoring agency must be included in the periodic assessments and annual monitoring network plan required by § 58.10. The plan shall include a statement of purposes for each SPM monitor and evidence that operation of each monitor meets the requirements of appendix A or an approved alternative as provided by § 58.11(a)(2) where applicable. The monitoring agency may designate a monitor as an SPM after January 1, 2007 only if it is a new monitor, i.e., a SLAMS monitor that is not included in the currently applicable monitoring plan or, for a monitor included in the monitoring plan prior to January 1, 2007, if the Regional Administrator has approved the discontinuation of the monitor as a SLAMS site. (b) Any SPM data collected by an air monitoring agency using a Federal reference method (FRM) or Federal equivalent method (FEM) must meet the requirements of §§ 58.11 and 58.12 and appendix A to this part or an approved alternative to appendix A. Compliance with appendix E to this part is optional but encouraged except when the monitoring agency's data objectives are inconsistent with the requirements in appendix E. Data collected at an SPM using a FRM or FEM meeting the requirements of appendix A must be submitted to AQS according to the requirements of § 58.16. Data collected by other SPMs may be submitted. The monitoring agency must also submit to AQS an indication of whether each SPM reporting data to AQS monitor meets the requirements of appendices A and E. (c) All data from an SPM using an FRM or FEM which has operated for more than 24 months are eligible for comparison to the relevant NAAQS, subject to the conditions of §§ 58.11(e) and 58.30, unless the air monitoring agency demonstrates that the data came from a particular period during which the requirements of appendix A, appendix C, or appendix E to this part were not met, subject to review and EPA Regional Office approval as part of the annual monitoring network plan described in § 58.10. (d) If an SPM using an FRM or FEM is discontinued within 24 months of start-up, the Administrator will not base a NAAQS violation determination for the PM 2.5 (e) If an SPM using an FRM or FEM is discontinued within 24 months of start-up, the Administrator will not designate an area as nonattainment for the CO, SO 2 2 10 (f) Prior approval from EPA is not required for discontinuance of an SPM. [71 FR 61298, Oct. 17, 2006, as amended at 72 FR 32210, June 12, 2007; 73 FR 67060, Nov. 12, 2008; 78 FR 3283, Jan. 15, 2013; 89 FR 16390, Mar. 6, 2024] Subpart D—Comparability of Ambient Data to the NAAQS Source: 71 FR 61302, Oct. 17, 2006, unless otherwise noted. § 58.30 Special considerations for data comparisons to the NAAQS. (a) Comparability of 2.5 data. 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 (b) [Reserved] [71 FR 61302, Oct. 17, 2006, as amended at 78 FR 3283, Jan. 15, 2013] Subpart E [Reserved] Subpart F—Air Quality Index Reporting § 58.50 Index reporting. (a) The State or where applicable, local agency shall report to the general public on a daily basis through prominent notice an air quality index that complies with the requirements of appendix G to this part. (b) Reporting is required for all individual MSA with a population exceeding 350,000. (c) The population of a metropolitan statistical area for purposes of index reporting is the latest available U.S. census population. [71 FR 61302, Oct. 17, 2006, as amended at 80 FR 65466, Oct. 26, 2015] Subpart G—Federal Monitoring Source: 44 FR 27571, May 10, 1979, unless otherwise noted. Redesignated at 58 FR 8467, Feb. 12, 1993. § 58.60 Federal monitoring. The Administrator may locate and operate an ambient air monitoring site if the State or local agency fails to locate, or schedule to be located, during the initial network design process, or as a result of the 5-year network assessments required in § 58.10, a SLAMS station at a site which is necessary in the judgment of the Regional Administrator to meet the objectives defined in appendix D to this part. [71 FR 61303, Oct. 17, 2006] § 58.61 Monitoring other pollutants. The Administrator may promulgate criteria similar to that referenced in subpart B of this part for monitoring a pollutant for which an NAAQS does not exist. Such an action would be taken whenever the Administrator determines that a nationwide monitoring program is necessary to monitor such a pollutant. [71 FR 61303, Oct. 17, 2006] Appendix A to Part 58—Quality Assurance Requirements for Monitors used in Evaluations of National Ambient Air Quality Standards 1. General Information 2. Quality System Requirements 3. Measurement Quality Check Requirements 4. Calculations for Data Quality Assessments 5. Reporting Requirements 6. References 1. General Information 1.1 Applicability. e.g., (b) Primary quality assurance organizations are encouraged to develop and maintain quality systems more extensive than the required minimums. Additional guidance for the requirements reflected in this appendix can be found in the “Quality Assurance Handbook for Air Pollution Measurement Systems,” Volume II (see reference 10 of this appendix) and at a national level in references 1, 2, and 3 of this appendix. 1.2 Primary Quality Assurance Organization (PQAO). 1.2.1 Each PQAO shall be defined such that measurement uncertainty among all stations in the organization can be expected to be reasonably homogeneous as a result of common factors. Common factors that should be considered in defining PQAOs include: (a) Operation by a common team of field operators according to a common set of procedures; (b) Use of a common quality assurance project plan (QAPP) or standard operating procedures; (c) Common calibration facilities and standards; (d) Oversight by a common quality assurance organization; and (e) Support by a common management organization ( i.e., Since data quality assessments are made and data certified at the PQAO level, the monitoring organization identified as the PQAO will be responsible for the oversight of the quality of data of all monitoring organizations within the PQAO. 1.2.2 Monitoring organizations having difficulty describing its PQAO or in assigning specific monitors to primary quality assurance organizations should consult with the appropriate EPA Regional Office. Any consolidation of monitoring organizations to PQAOs shall be subject to final approval by the appropriate EPA Regional Office. 1.2.3 Each PQAO is required to implement a quality system that provides sufficient information to assess the quality of the monitoring data. The quality system must, at a minimum, include the specific requirements described in this appendix. Failure to conduct or pass a required check or procedure, or a series of required checks or procedures, does not by itself invalidate data for regulatory decision making. Rather, PQAOs and the EPA shall use the checks and procedures required in this appendix in combination with other data quality information, reports, and similar documentation that demonstrate overall compliance with Part 58. Accordingly, the EPA and PQAOs shall use a “weight of evidence” approach when determining the suitability of data for regulatory decisions. The EPA reserves the authority to use or not use monitoring data submitted by a monitoring organization when making regulatory decisions based on the EPA's assessment of the quality of the data. Consensus built validation templates or validation criteria already approved in QAPPs should be used as the basis for the weight of evidence approach. 1.3 Definitions. (a) Measurement Uncertainty. (b) Precision. (c) Bias. (d) Accuracy. (e) Completeness. (f) Detection Limit. 1.4 Measurement Quality Checks. 1.5 Assessments and Reports. 2. Quality System Requirements A quality system (reference 1 of this appendix) is the means by which an organization manages the quality of the monitoring information it produces in a systematic, organized manner. It provides a framework for planning, implementing, assessing and reporting work performed by an organization and for carrying out required quality assurance and quality control activities. 2.1 Quality Management Plans and Quality Assurance Project Plans. (a) Meet a well-defined need, use, or purpose (reference 5 of this appendix); (b) Provide data of adequate quality for the intended monitoring objectives; (c) Satisfy stakeholder expectations; (d) Comply with applicable standards specifications; (e) Comply with statutory (and other legal) requirements; and (f) Reflect consideration of cost and economics. 2.1.1 The QMP describes the quality system in terms of the organizational structure, functional responsibilities of management and staff, lines of authority, and required interfaces for those planning, implementing, assessing and reporting activities involving environmental data operations (EDO). The QMP must be suitably documented in accordance with EPA requirements (reference 2 of this appendix), and approved by the appropriate Regional Administrator, or his or her representative. The quality system described in the QMP will be reviewed during the systems audits described in section 2.5 of this appendix. Organizations that implement long-term monitoring programs with EPA funds should have a separate QMP document. Smaller organizations, organizations that do infrequent work with the EPA or have monitoring programs of limited size or scope may combine the QMP with the QAPP if approved by, and subject to any conditions of the EPA. Additional guidance on this process can be found in reference 10 of this appendix. Approval of the recipient's QMP by the appropriate Regional Administrator or his or her representative may allow delegation of authority to the PQAOs independent quality assurance function to review and approve environmental data collection activities adequately described and covered under the scope of the QMP and documented in appropriate planning documents (QAPP). Where a PQAO or monitoring organization has been delegated authority to review and approve their QAPP, an electronic copy must be submitted to the EPA region at the time it is submitted to the PQAO/monitoring organization's QAPP approving authority. The QAPP will be reviewed by the EPA during systems audits or circumstances related to data quality. The QMP submission and approval dates for PQAOs/monitoring organizations must be reported to AQS either by the monitoring organization or the EPA Region. 2.1.2 The QAPP is a formal document describing, in sufficient detail, the quality system that must be implemented to ensure that the results of work performed will satisfy the stated objectives. PQAOs must develop QAPPs that describe how the organization intends to control measurement uncertainty to an appropriate level in order to achieve the data quality objectives for the EDO. The quality assurance policy of the EPA requires every EDO to have a written and approved QAPP prior to the start of the EDO. It is the responsibility of the PQAO/monitoring organization to adhere to this policy. The QAPP must be suitably documented in accordance with EPA requirements (reference 3 of this appendix) and include standard operating procedures for all EDOs either within the document or by appropriate reference. The QAPP must identify each PQAO operating monitors under the QAPP as well as generally identify the sites and monitors to which it is applicable either within the document or by appropriate reference. The QAPP submission and approval dates must be reported to AQS either by the monitoring organization or the EPA Region. 2.1.3 The PQAO/monitoring organization's quality system must have adequate resources both in personnel and funding to plan, implement, assess and report on the achievement of the requirements of this appendix and it's approved QAPP. 2.2 Independence of Quality Assurance. e.g., 2.3. Data Quality Performance Requirements. 2.3.1 Data Quality Objectives. 2.3.1.1 Measurement Uncertainty for Automated and Manual PM 2.5 Methods. 2.3.1.2 Measurement Uncertainty for Automated O 3 Methods. 2.3.1.3 Measurement Uncertainty for Pb Methods. 2.3.1.4 Measurement Uncertainty for NO 2 2.3.1.5 Measurement Uncertainty for SO 2. 2.4 National Performance Evaluation Programs. 2.5 2.5 2.4.1 Independent assessment. 2.5 Technical Systems Audit Program. 2.6 Gaseous and Flow Rate Audit Standards. 2.6.1 Gaseous pollutant concentration standards (permeation devices or cylinders of compressed gas) used to obtain test concentrations for CO, SO 2 2 2.6.1.1 The concentrations of EPA Protocol Gas standards used for ambient air monitoring must be certified with a 95-percent confidence interval to have an analytical uncertainty of no more than ±2.0 percent (inclusive) of the certified concentration (tag value) of the gas mixture. The uncertainty must be calculated in accordance with the statistical procedures defined in Reference 4 of this appendix. 2.6.1.2 Specialty gas producers advertising certification with the procedures provided in Reference 4 of this appendix and distributing gases as “EPA Protocol Gas” for ambient air monitoring purposes must adhere to the regulatory requirements specified in 40 CFR 75.21(g) or not use “EPA” in any form of advertising. Monitoring organizations must provide information to the EPA on the specialty gas producers they use on an annual basis. PQAOs, when requested by the EPA, must participate in the EPA Ambient Air Protocol Gas Verification Program at least once every 5 years by sending a new unused standard to a designated verification laboratory. 2.6.2 Test concentrations for O 3 3 3 2.6.3 Flow rate measurements must be made by a flow measuring instrument that is NIST-traceable to an authoritative volume or other applicable standard. Guidance for certifying some types of flowmeters is provided in reference 10 of this appendix. 2.7 Primary Requirements and Guidance. 3. Measurement Quality Check Requirements This section provides the requirements for PQAOs to perform the measurement quality checks that can be used to assess data quality. Data from these checks are required to be submitted to the AQS within the same time frame as routinely-collected ambient concentration data as described in 40 CFR 58.16. Table A-1 of this appendix provides a summary of the types and frequency of the measurement quality checks that will be described in this section. 3.1. Gaseous Monitors of SO 2 , NO 2 , O 3 , and CO 3.1.1 One-Point Quality Control (QC) Check for SO 2, 2 3 2 2 3 2 2 3 (b) Point analyzers must operate in their normal sampling mode during the QC check and the test atmosphere must pass through all filters, scrubbers, conditioners and other components used during normal ambient sampling and as much of the ambient air inlet system as is practicable. The QC check must be conducted before any calibration or adjustment to the monitor. (c) Open path monitors are tested by inserting a test cell containing a QC check gas concentration into the optical measurement beam of the instrument. If possible, the normally used transmitter, receiver, and as appropriate, reflecting devices should be used during the test, and the normal monitoring configuration of the instrument should be altered as little as possible to accommodate the test cell for the test. However, if permitted by the associated operation or instruction manual, an alternate local light source or an alternate optical path that does not include the normal atmospheric monitoring path may be used. The actual concentration of the QC check gas in the test cell must be selected to produce an effective concentration in the range specified earlier in this section. Generally, the QC test concentration measurement will be the sum of the atmospheric pollutant concentration and the QC test concentration. As such, the result must be corrected to remove the atmospheric concentration contribution. The corrected concentration is obtained by subtracting the average of the atmospheric concentrations measured by the open path instrument under test immediately before and immediately after the QC test from the QC check gas concentration measurement. If the difference between these before and after measurements is greater than 20 percent of the effective concentration of the test gas, discard the test result and repeat the test. If possible, open path monitors should be tested during periods when the atmospheric pollutant concentrations are relatively low and steady. (d) Report the audit concentration of the QC gas and the corresponding measured concentration indicated by the monitor to AQS. The percent differences between these concentrations are used to assess the precision and bias of the monitoring data as described in sections 4.1.2 (precision) and 4.1.3 (bias) of this appendix. 3.1.2 Annual performance evaluation for SO 2 NO 2 O 3 , or CO 3.1.2.1 The evaluation is made by challenging the monitor with audit gas standards of known concentration from at least three audit levels. One point must be within two to three times the method detection limit of the instruments within the PQAOs network, the second point will be less than or equal to the 99th percentile of the data at the site or the network of sites in the PQAO or the next highest audit concentration level. The third point can be around the primary NAAQS or the highest 3-year concentration at the site or the network of sites in the PQAO. An additional 4th level is encouraged for those agencies that would like to confirm the monitors' linearity at the higher end of the operational range. In rare circumstances, there may be sites measuring concentrations above audit level 10. Notify the appropriate EPA region and the AQS program in order to make accommodations for auditing at levels above level 10. Audit level Concentration Range, ppm O 3 SO 2 NO 2 CO 1 0.004-0.0059 0.0003-0.0029 0.0003-0.0029 0.020-0.059 2 0.006-0.019 0.0030-0.0049 0.0030-0.0049 0.060-0.199 3 0.020-0.039 0.0050-0.0079 0.0050-0.0079 0.200-0.899 4 0.040-0.069 0.0080-0.0199 0.0080-0.0199 0.900-2.999 5 0.070-0.089 0.0200-0.0499 0.0200-0.0499 3.000-7.999 6 0.090-0.119 0.0500-0.0999 0.0500-0.0999 8.000-15.999 7 0.120-0.139 0.1000-0.1499 0.1000-0.2999 16.000-30.999 8 0.140-0.169 0.1500-0.2599 0.3000-0.4999 31.000-39.999 9 0.170-0.189 0.2600-0.7999 0.5000-0.7999 40.000-49.999 10 0.190-0.259 0.8000-1.000 0.8000-1.000 50.000-60.000 3.1.2.2 The standards from which audit gas test concentrations are obtained must meet the specifications of section 2.6.1 of this appendix. The gas standards and equipment used for the performance evaluation must not be the same as the standards and equipment used for one-point QC, calibrations, span evaluations or NPAP. 3.1.2.3 For point analyzers, the evaluation shall be carried out by allowing the monitor to analyze the audit gas test atmosphere in its normal sampling mode such that the test atmosphere passes through all filters, scrubbers, conditioners, and other sample inlet components used during normal ambient sampling and as much of the ambient air inlet system as is practicable. 3.1.2.4 Open-path monitors are evaluated by inserting a test cell containing the various audit gas concentrations into the optical measurement beam of the instrument. If possible, the normally used transmitter, receiver, and, as appropriate, reflecting devices should be used during the evaluation, and the normal monitoring configuration of the instrument should be modified as little as possible to accommodate the test cell for the evaluation. However, if permitted by the associated operation or instruction manual, an alternate local light source or an alternate optical path that does not include the normal atmospheric monitoring path may be used. The actual concentrations of the audit gas in the test cell must be selected to produce effective concentrations in the evaluation level ranges specified in this section of this appendix. Generally, each evaluation concentration measurement result will be the sum of the atmospheric pollutant concentration and the evaluation test concentration. As such, the result must be corrected to remove the atmospheric concentration contribution. The corrected concentration is obtained by subtracting the average of the atmospheric concentrations measured by the open path instrument under test immediately before and immediately after the evaluation test (or preferably before and after each evaluation concentration level) from the evaluation concentration measurement. If the difference between the before and after measurements is greater than 20 percent of the effective concentration of the test gas standard, discard the test result for that concentration level and repeat the test for that level. If possible, open path monitors should be evaluated during periods when the atmospheric pollutant concentrations are relatively low and steady. Also, if the open-path instrument is not installed in a permanent manner, the monitoring path length must be reverified to be within ±3 percent to validate the evaluation since the monitoring path length is critical to the determination of the effective concentration. 3.1.2.5 Report both the evaluation concentrations (effective concentrations for open-path monitors) of the audit gases and the corresponding measured concentration (corrected concentrations, if applicable, for open path monitors) indicated or produced by the monitor being tested to AQS. The percent differences between these concentrations are used to assess the quality of the monitoring data as described in section 4.1.1 of this appendix. 3.1.3 National Performance Audit Program (NPAP). The NPAP is a performance evaluation which is a type of audit where quantitative data are collected independently in order to evaluate the proficiency of an analyst, monitoring instrument or laboratory. Due to the implementation approach used in the program, NPAP provides a national independent assessment of performance while maintaining a consistent level of data quality. Details of the program can be found in reference 11 of this appendix. The program requirements include: 3.1.3.1 Performing audits of the primary monitors at 20 percent of monitoring sites per year, and 100 percent of the sites every 6 years. High-priority sites may be audited more frequently. Since not all gaseous criteria pollutants are monitored at every site within a PQAO, it is not required that 20 percent of the primary monitors for each pollutant receive an NPAP audit each year only that 20 percent of the PQAOs monitoring sites receive an NPAP audit. It is expected that over the 6-year period all primary monitors for all gaseous pollutants will receive an NPAP audit. 3.1.3.2 Developing a delivery system that will allow for the audit concentration gasses to be introduced to the probe inlet where logistically feasible. 3.1.3.3 Using audit gases that are verified against the NIST standard reference methods or special review procedures and validated per the certification periods specified in Reference 4 of this appendix (EPA Traceability Protocol for Assay and Certification of Gaseous Calibration Standards) for CO, SO 2 2 3 3.1.3.4 As described in section 2.4 of this appendix, the PQAO may elect, on an annual basis, to utilize the federally implemented NPAP program. If the PQAO plans to self-implement NPAP, the EPA will establish training and other technical requirements for PQAOs to establish comparability to federally implemented programs. In addition to meeting the requirements in sections 3.1.3.1 through 3.1.3.3 of this appendix, the PQAO must: (a) Utilize an audit system equivalent to the federally implemented NPAP audit system and is separate from equipment used in annual performance evaluations. (b) Perform a whole system check by having the NPAP system tested against an independent and qualified EPA lab, or equivalent. (c) Evaluate the system with the EPA NPAP program through collocated auditing at an acceptable number of sites each year (at least one for an agency network of five or less sites; at least two for a network with more than five sites). (d) Incorporate the NPAP in the PQAO's quality assurance project plan. (e) Be subject to review by independent, EPA-trained personnel. (f) Participate in initial and update training/certification sessions. 3.1.3.5 OAQPS, in consultation with the relevant EPA Regional Office, may approve the PQAO's plan to self-implement NPAP if the OAQPS determines that the PQAO's self-implementation plan is equivalent to the federal programs and adequate to meet the objectives of national consistency and data quality. 3.2 PM 2.5 3.2.1 Flow Rate Verification for PM 2.5 2.5 3.2.2 Semi-Annual Flow Rate Audit for PM 2.5 3.2.3 Collocated Quality Control Sampling Procedures for PM 2.5 3.2.3.1 For each distinct monitoring method designation (FRM or FEM) that a PQAO is using for a primary monitor, the PQAO must have 15 percent of the primary monitors of each method designation collocated (values of 0.5 and greater round up); and have at least one collocated quality control monitor (if the total number of monitors is less than three). The first collocated monitor must be a designated FRM monitor. 3.2.3.2 In addition, monitors selected for collocation must also meet the following requirements: (a) A primary monitor designated as an EPA FRM shall be collocated with a quality control monitor having the same EPA FRM method designation. (b) For each primary monitor designated as an EPA FEM used by the PQAO, 50 percent of the monitors designated for collocation, or the first if only one collocation is necessary, shall be collocated with a FRM quality control monitor and 50 percent of the monitors shall be collocated with a monitor having the same method designation as the FEM primary monitor. If an odd number of collocated monitors is required, the additional monitor shall be a FRM quality control monitor. An example of the distribution of collocated monitors for each unique FEM is provided below. Table A-2 of this appendix demonstrates the collocation procedure with a PQAO having one type of primary FRM and multiple primary FEMs. #Primary FEMS of a unique method #Collocated #Collocated with an FRM #Collocated with same method 1-9 1 1 0 10-16 2 1 1 17-23 3 2 1 24-29 4 2 2 30-36 5 3 2 37-43 6 3 3 3.2.3.3 Since the collocation requirements are used to assess precision of the primary monitors and there can only be one primary monitor at a monitoring site, a site can only count for the collocation of the method designation of the primary monitor at that site. 3.2.3.4 The collocated monitors should be deployed according to the following protocol: (a) Fifty percent of the collocated quality control monitors should be deployed at sites with annual average or daily concentrations estimated to be within plus or minus 20 percent of either the annual or 24-hour NAAQS and the remainder at the PQAOs discretion; (b) If an organization has no sites with annual average or daily concentrations within ±20 percent of the annual NAAQS or 24-hour NAAQS, 50 percent of the collocated quality control monitors should be deployed at those sites with the annual mean concentrations or 24-hour concentrations among the highest for all sites in the network and the remainder at the PQAOs discretion. (c) The two collocated monitors must be within 4 meters (inlet to inlet) of each other and at least 2 meters apart for flow rates greater than 200 liters/min or at least 1 meter apart for samplers having flow rates less than 200 liters/min to preclude airflow interference. A waiver allowing up to 10 meters horizontal distance and up to 3 meters vertical distance (inlet to inlet) between a primary and collocated sampler may be approved by the Regional Administrator for sites at a neighborhood or larger scale of representation during the annual network plan approval process. Sampling and analytical methodologies must be the consistently implemented for both primary and collocated quality control samplers and for all other samplers in the network. (d) Sample the collocated quality control monitor on a 1-in-12 day schedule. Report the measurements from both primary and collocated quality control monitors at each collocated sampling site to AQS. The calculations for evaluating precision between the two collocated monitors are described in section 4.2.1 of this appendix. 3.2.4 PM 2.5 Performance Evaluation Program (PEP) Procedures. 3.2.4.1 Have each method designation evaluated each year; and, 3.2.4.2 Have all FRM and FEM samplers subject to a PEP audit at least once every 6 years, which equates to approximately 15 percent of the monitoring sites audited each year. 3.2.4.3. Additional information concerning the PEP is contained in reference 10 of this appendix. The calculations for evaluating bias between the primary monitor and the performance evaluation monitor for PM 2.5 3.3 PM 10 3.3.1 Flow Rate Verification for PM 10 Low Volume Samplers (less than 200 liter/minute). 10 3.3.2 Flow Rate Verification for PM 10 High Volume Samplers (greater than 200 liters/minute). 10 3.3.3 Semi-Annual Flow Rate Audit for PM 10 3.3.4 Collocated Quality Control Sampling Procedures for Manual PM 10 10 3.3.4.1 For manual PM 10 (a) Have 15 percent of the primary monitors collocated (values of 0.5 and greater round up); and (b) Have at least one collocated quality control monitor (if the total number of monitors is less than three). 3.3.4.2 The collocated quality control monitors should be deployed according to the following protocol: (a) Fifty percent of the collocated quality control monitors should be deployed at sites with daily concentrations estimated to be within plus or minus 20 percent of the applicable NAAQS and the remainder at the PQAOs discretion; (b) If an organization has no sites with daily concentrations within plus or minus 20 percent of the NAAQS, 50 percent of the collocated quality control monitors should be deployed at those sites with the daily mean concentrations among the highest for all sites in the network and the remainder at the PQAOs discretion. (c) The two collocated monitors must be within 4 meters (inlet to inlet) of each other and at least 2 meters apart for flow rates greater than 200 liters/min or at least 1 meter apart for samplers having flow rates less than 200 liters/min to preclude airflow interference. A waiver allowing up to 10 meters horizontal distance and up to 3 meters vertical distance (inlet to inlet) between a primary and collocated sampler may be approved by the Regional Administrator for sites at a neighborhood or larger scale of representation. This waiver may be approved during the annual network plan approval process. Sampling and analytical methodologies must be the consistently implemented for both collocated samplers and for all other samplers in the network. (d) Sample the collocated quality control monitor on a 1-in-12 day schedule. Report the measurements from both primary and collocated quality control monitors at each collocated sampling site to AQS. The calculations for evaluating precision between the two collocated monitors are described in section 4.2.1 of this appendix. (e) In determining the number of collocated quality control sites required for PM 10 10 10 10 10 10 3.4 Pb. 3.4.1 Flow Rate Verification for Pb-PM 10 Low Volume Samplers (less than 200 liter/minute). 3.4.2 Flow Rate Verification for Pb High Volume Samplers (greater than 200 liters/minute). 3.4.3 Semi-Annual Flow Rate Audit for Pb. 3.4.4 Collocated Quality Control Sampling for TSP Pb for monitoring sites other than non-source oriented NCore. For each pair of collocated monitors for manual TSP Pb samplers, designate one sampler as the primary monitor whose concentrations will be used to report air quality for the site, and designate the other as the quality control monitor. 3.4.4.1 A PQAO must: (a) Have 15 percent of the primary monitors (not counting non-source oriented NCore sites in PQAO) collocated. Values of 0.5 and greater round up; and (b) Have at least one collocated quality control monitor (if the total number of monitors is less than three). 3.4.4.2 The collocated quality control monitors should be deployed according to the following protocol: (a) The first collocated Pb site selected must be the site measuring the highest Pb concentrations in the network. If the site is impractical, alternative sites, approved by the EPA Regional Administrator, may be selected. If additional collocated sites are necessary, collocated sites may be chosen that reflect average ambient air Pb concentrations in the network. (b) The two collocated monitors must be within 4 meters (inlet to inlet) of each other and at least 2 meters apart for flow rates greater than 200 liters/min or at least 1 meter apart for samplers having flow rates less than 200 liters/min to preclude airflow interference. (c) Sample the collocated quality control monitor on a 1-in-12 day schedule. Report the measurements from both primary and collocated quality control monitors at each collocated sampling site to AQS. The calculations for evaluating precision between the two collocated monitors are described in section 4.2.1 of this appendix. 3.4.5 Collocated Quality Control Sampling for Pb-PM 10 10 3.4.5.1 Have 15 percent of the primary monitors (not counting non-source oriented NCore sites in PQAO) collocated. Values of 0.5 and greater round up; and 3.4.5.2 Have at least one collocated quality control monitor (if the total number of monitors is less than three). 3.4.5.3 The collocated monitors should be deployed according to the following protocol: (a) Fifty percent of the collocated quality control monitors should be deployed at sites with the highest 3-month average concentrations and the remainder at the PQAOs discretion. (b) The two collocated monitors must be within 4 meters (inlet to inlet) of each other and at least 2 meters apart for flow rates greater than 200 liters/min or at least 1 meter apart for samplers having flow rates less than 200 liters/min to preclude airflow interference. A waiver allowing up to 10 meters horizontal distance and up to 3 meters vertical distance (inlet to inlet) between a primary and collocated sampler may be approved by the Regional Administrator for sites at a neighborhood or larger scale of representation. This waiver may be approved during the annual network plan approval process. Sampling and analytical methodologies must be the consistently implemented for both collocated samplers and for all other samplers in the network. (c) Sample the collocated quality control monitor on a 1-in-12 day schedule. Report the measurements from both primary and collocated quality control monitors at each collocated sampling site to AQS. The calculations for evaluating precision between the two collocated monitors are described in section 4.2.1 of this appendix. (d) In determining the number of collocated quality control sites required for Pb-PM 10 10 10 10 10 10 10 3.4.6 Pb Analysis Audits. Range Equivalent ambient Pb 3 1 30-100% of Pb NAAQS. 2 200-300% of Pb NAAQS. (a) Extract the audit samples using the same extraction procedure used for exposed filters. (b) Analyze three audit samples in each of the two ranges each quarter samples are analyzed. The audit sample analyses shall be distributed as much as possible over the entire calendar quarter. (c) Report the audit concentrations (in µg Pb/filter or strip) and the corresponding measured concentrations (in µg Pb/filter or strip) to AQS using AQS unit code 077. The percent differences between the concentrations are used to calculate analytical accuracy as described in section 4.2.6 of this appendix. 3.4.7 Pb PEP Procedures for monitoring sites other than non-source oriented NCore. The PEP is an independent assessment used to estimate total measurement system bias. These evaluations will be performed under the NPEP described in section 2.4 of this appendix or a comparable program. Each year, one performance evaluation audit must be performed at one Pb site in each primary quality assurance organization that has less than or equal to five sites and two audits at PQAOs with greater than five sites. Non-source oriented NCore sites are not counted. Siting of the PEP monitor must be consistent with section 3.4.5.3(b). However, any horizontal distance greater than 4 meters and any vertical distance greater than 1 meter must be reported to the EPA regional PEP coordinator. In addition, each year, four collocated samples from PQAOs with less than or equal to five sites and six collocated samples at PQAOs with greater than five sites must be sent to an independent laboratory, the same laboratory as the performance evaluation audit, for analysis. The calculations for evaluating bias between the primary monitor and the performance evaluation monitor for Pb are described in section 4.2.4 of this appendix. 4. Calculations for Data Quality Assessments (a) Calculations of measurement uncertainty are carried out by the EPA according to the following procedures. The PQAOs must report the data to AQS for all measurement quality checks as specified in this appendix even though they may elect to perform some or all of the calculations in this section on their own. (b) The EPA will provide annual assessments of data quality aggregated by site and PQAO for SO 2 2 3 10 2.5 (c) At low concentrations, agreement between the measurements of collocated quality control samplers, expressed as relative percent difference or percent difference, may be relatively poor. For this reason, collocated measurement pairs are selected for use in the precision and bias calculations only when both measurements are equal to or above the following limits: (1) Pb: 0.002 µg/m 3 (2) Pb: 0.02 µg/m 3 (3) PM 10 3 (4) PM 10 3 (5) PM 2.5 3 4.1 Statistics for the Assessment of QC Checks for 2, 2 3 4.1.1 Percent Difference. d i where meas audit 4.1.2 Precision Estimate. 2 2 3 where n 2 0.1,n-1 4.1.3 Bias Estimate. 2 2 3 where n 0.95,n-1 AB d i ′ s and the quantity AS d i ′ s 4.1.3.1 Assigning a sign (positive/negative) to the bias estimate. 4.1.3.2 Calculate the 25th and 75th percentiles of the percent differences for each site. The absolute bias upper bound should be flagged as positive if both percentiles are positive and negative if both percentiles are negative. The absolute bias upper bound would not be flagged if the 25th and 75th percentiles are of different signs. 4.2 Statistics for the Assessment of 10, 2.5 4.2.1 Collocated Quality Control Sampler Precision Estimate for PM 10, PM 2.5 , and Pb t i , Equation 6 to Section 4.2.1 of Appendix A Where X i Y i Where k 2 0.1,k-1 t i 4.2.2 One-Point Flow Rate Verification Bias Estimate for PM 10, PM 2.5 and Pb meas audit n 0.95,n-1 AB d i′s AS d i′s 4.2.3 Semi-Annual Flow Rate Audit Bias Estimate for PM 10, PM 2.5 and Pb. 4.2.4 Performance Evaluation Programs Bias Estimate for Pb. 4.2.5 Performance Evaluation Programs Bias Estimate for PM 2.5 i 4.2.6 Pb Analysis Audit Bias Estimate. 5. Reporting Requirements 5.1 Reporting Requirements. 5.1.1 Quarterly Reports. 5.1.2 Annual Reports. 5.1.2.1 When the PQAO has certified relevant data for the calendar year, the EPA will calculate and report the measurement uncertainty for the entire calendar year. 6. References (1) American National Standard Institute—Quality Management Systems For Environmental Information And Technology Programs—Requirements With Guidance For Use. ASQ/ANSI E4-2014. February 2014. Available from ANSI Webstore https://webstore.ansi.org/. (2) EPA Requirements for Quality Management Plans. EPA QA/R-2. EPA/240/B-01/002. March 2001, Reissue May 2006. Office of Environmental Information, Washington DC 20460. http://www.epa.gov/quality/agency-wide-quality-system-documents. (3) EPA Requirements for Quality Assurance Project Plans for Environmental Data Operations. EPA QA/R-5. EPA/240/B-01/003. March 2001, Reissue May 2006. Office of Environmental Information, Washington DC 20460. http://www.epa.gov/quality/agency-wide-quality-system-documents. (4) EPA Traceability Protocol for Assay and Certification of Gaseous Calibration Standards. EPA-600/R-12/531. May, 2012. Available from U.S. Environmental Protection Agency, National Risk Management Research Laboratory, Research Triangle Park NC 27711. https://www.epa.gov/nscep. (5) Guidance for the Data Quality Objectives Process. EPA QA/G-4. EPA/240/B-06/001. February, 2006. Office of Environmental Information, Washington DC 20460. http://www.epa.gov/quality/agency-wide-quality-system-documents. (6) List of Designated Reference and Equivalent Methods. Available from U.S. Environmental Protection Agency, Center for Environmental Measurements and Modeling, Air Methods and Characterization Division, MD-D205-03, Research Triangle Park, NC 27711. https://www.epa.gov/amtic/air-monitoring-methods-criteria-pollutants. (7) Transfer Standards for the Calibration of Ambient Air Monitoring Analyzers for Ozone. EPA-454/B-13-004 U.S. Environmental Protection Agency, Research Triangle Park, NC 27711, October, 2013. https://www.epa.gov/sites/default/files/2020-09/documents/ozonetransferstandardguidance.pdf. (8) Paur, R.J. and F.F. McElroy. Technical Assistance Document for the Calibration of Ambient Ozone Monitors. EPA-600/4-79-057. U.S. Environmental Protection Agency, Research Triangle Park, NC 27711, September, 1979. http://www.epa.gov/ttn/amtic/cpreldoc.html. (9) Quality Assurance Handbook for Air Pollution Measurement Systems, Volume 1—A Field Guide to Environmental Quality Assurance. EPA-600/R-94/038a. April 1994. Available from U.S. Environmental Protection Agency, ORD Publications Office, Center for Environmental Research Information (CERI), 26 W. Martin Luther King Drive, Cincinnati, OH 45268. https://www.epa.gov/amtic/ambient-air-monitoring-quality-assurance#documents. (10) Quality Assurance Handbook for Air Pollution Measurement Systems, Volume II: Ambient Air Quality Monitoring Program Quality System Development. EPA-454/B-13-003. https://www.epa.gov/amtic/ambient-air-monitoring-quality-assurance#documents. (11) National Performance Evaluation Program Standard Operating Procedures. https://www.epa.gov/amtic/ambient-air-monitoring-quality-assurance#npep. Table A-1 to Section 6 of Appendix A—Minimum Data Assessment Requirements for NAAQS Related Criteria Pollutant Monitors Method Assessment method Coverage Minimum Parameters AQS assessment type Gaseous Methods (CO, NO 2 2 3 One-Point QC for SO 2 2 3 Response check at concentration 0.005-0.08 ppm SO 2 2 3 Each analyzer Once per 2 weeks 5 Audit concentration 1 2 One-Point QC. Annual performance evaluation for SO 2 2 3 See section 3.1.2 of this appendix Each analyzer Once per year Audit concentration 1 2 Annual PE. NPAP for SO 2 2 3 Independent Audit 20% of sites each year Once per year Audit concentration 1 2 NPAP. Particulate Methods: Continuous 4 2.5 Collocated samplers 15% 1-in-12 days Primary sampler concentration and duplicate sampler concentration. 3 No Transaction reported as raw data. Manual method—collocated quality control sampling PM 10 2.5 10 Collocated samplers 15% 1-in-12 days Primary sampler concentration and duplicate sampler concentration. 3 No Transaction reported as raw data. Flow rate verification PM 10 2.5 10 Check of sampler flow rate Each sampler Once every month 5 Audit flow rate and measured flow rate indicated by the sampler Flow Rate Verification. Flow rate verification PM 10 Check of sampler flow rate Each sampler Once every quarter 5 Audit flow rate and measured flow rate indicated by the sampler Flow Rate Verification. Semi-annual flow rate audit PM 10 10 2.5 10 Check of sampler flow rate using independent standard Each sampler Once every 6 months 5 Audit flow rate and measured flow rate indicated by the sampler Semi Annual Flow Rate Audit. Pb analysis audits Pb-TSP, Pb-PM 10 Check of analytical system with Pb audit strips/filters Analytical Once each quarter 5 Measured value and audit value (ug Pb/filter) using AQS unit code 077 Pb Analysis Audits. Performance Evaluation Program PM 2.5 Collocated samplers (1) 5 valid audits for primary QA orgs, with ≤5 sites Distributed over all 4 quarters 5 Primary sampler concentration and performance evaluation sampler concentration PEP. Performance Evaluation Program Pb-TSP, Pb-PM 10 Collocated samplers (1) 1 valid audit and 4 collocated samples for primary QA orgs, with ≤5 sites Distributed over all 4 quarters 5 Primary sampler concentration and performance evaluation sampler concentration. Primary sampler concentration and duplicate sampler concentration PEP. 1 2 3 4 2.5 5 Table A-2 of Appendix A to Part 58—Summary of PM 2.5 Primary sampler method designation Total No. of monitors Total No. of collocated No. of No. of FRM 20 3 3 3 FEM (A) 20 3 2 1 FEM (B) 2 1 1 0 FEM (C) 12 2 1 1 [81 FR 17280, Mar. 28, 2016, as amended at 89 FR 16390, Mar. 6, 2024; 89 FR 103655, Dec. 19, 2024] Appendix B to Part 58—Quality Assurance Requirements for Prevention of Significant Deterioration (PSD) Air Monitoring 1. General Information 2. Quality System Requirements 3. Measurement Quality Check Requirements 4. Calculations for Data Quality Assessments 5. Reporting Requirements 6. References 1. General Information 1.1 Applicability. (a) This appendix specifies the minimum quality assurance requirements for the control and assessment of the quality of the ambient air monitoring data submitted to a PSD reviewing authority or the EPA by an organization operating an air monitoring station, or network of stations, operated in order to comply with Part 51 New Source Review—Prevention of Significant Deterioration (PSD). Such organizations are encouraged to develop and maintain quality assurance programs more extensive than the required minimum. Additional guidance for the requirements reflected in this appendix can be found in the “Quality Assurance Handbook for Air Pollution Measurement Systems,” Volume II (Ambient Air) and “Quality Assurance Handbook for Air Pollution Measurement Systems,” Volume IV (Meteorological Measurements) and at a national level in references 1, 2, and 3 of this appendix. (b) It is not assumed that data generated for PSD under this appendix will be used in making NAAQS decisions. However, if all the requirements in this appendix are followed (including the NPEP programs) and reported to AQS, with review and concurrence from the EPA region, data may be used for NAAQS decisions. With the exception of the NPEP programs (NPAP, PM 2.5 1.2 PSD Primary Quality Assurance Organization (PQAO). 1.2.1 Each PSD PQAO shall be defined such that measurement uncertainty among all stations in the organization can be expected to be reasonably homogeneous, as a result of common factors. A PSD PQAO must be associated with only one PSD reviewing authority. Common factors that should be considered in defining PSD PQAOs include: (a) Operation by a common team of field operators according to a common set of procedures; (b) Use of a common QAPP and/or standard operating procedures; (c) Common calibration facilities and standards; (d) Oversight by a common quality assurance organization; and (e) Support by a common management organization or laboratory. 1.2.2 PSD monitoring organizations having difficulty describing its PQAO or in assigning specific monitors to a PSD PQAO should consult with the PSD reviewing authority. Any consolidation of PSD PQAOs shall be subject to final approval by the PSD reviewing authority. 1.2.3 Each PSD PQAO is required to implement a quality system that provides sufficient information to assess the quality of the monitoring data. The quality system must, at a minimum, include the specific requirements described in this appendix. Failure to conduct or pass a required check or procedure, or a series of required checks or procedures, does not by itself invalidate data for regulatory decision making. Rather, PSD PQAOs and the PSD reviewing authority shall use the checks and procedures required in this appendix in combination with other data quality information, reports, and similar documentation that demonstrate overall compliance with parts 51, 52 and 58 of this chapter. Accordingly, the PSD reviewing authority shall use a “weight of evidence” approach when determining the suitability of data for regulatory decisions. The PSD reviewing authority reserves the authority to use or not use monitoring data submitted by a PSD monitoring organization when making regulatory decisions based on the PSD reviewing authority's assessment of the quality of the data. Generally, consensus built validation templates or validation criteria already approved in quality assurance project plans (QAPPs) should be used as the basis for the weight of evidence approach. 1.3 Definitions. (a) Measurement Uncertainty. (b) Precision. (c) Bias. (d) Accuracy. (e) Completeness. (f) Detectability. 1.4 Measurement Quality Check Reporting. 1.5 Assessments and Reports. 2. Quality System Requirements A quality system (reference 1 of this appendix) is the means by which an organization manages the quality of the monitoring information it produces in a systematic, organized manner. It provides a framework for planning, implementing, assessing and reporting work performed by an organization and for carrying out required quality assurance and quality control activities. 2.1 Quality Assurance Project Plans. (a) Meet a well-defined need, use, or purpose (reference 5 of this appendix); (b) Provide data of adequate quality for the intended monitoring objectives; (c) Satisfy stakeholder expectations; (d) Comply with applicable standards specifications; (e) Comply with statutory (and other legal) requirements; and (f) Assure quality assurance and quality control adequacy and independence. 2.1.1 The QAPP is a formal document that describes these activities in sufficient detail and is supported by standard operating procedures. The QAPP must describe how the organization intends to control measurement uncertainty to an appropriate level in order to achieve the objectives for which the data are collected. The QAPP must be documented in accordance with EPA requirements (reference 3 of this appendix). 2.1.2 The PSD PQAO's quality system must have adequate resources both in personnel and funding to plan, implement, assess and report on the achievement of the requirements of this appendix and it's approved QAPP. 2.1.3 Incorporation of quality management plan (QMP) elements into the QAPP. The QMP describes the quality system in terms of the organizational structure, functional responsibilities of management and staff, lines of authority, and required interfaces for those planning, implementing, assessing and reporting activities involving environmental data operations (EDO). The PSD PQAOs may combine pertinent elements of the QMP into the QAPP rather than requiring the submission of both QMP and QAPP documents separately, with prior approval of the PSD reviewing authority. Additional guidance on QMPs can be found in reference 2 of this appendix. 2.2 Independence of Quality Assurance Management. The PSD PQAO must provide for a quality assurance management function for its PSD data collection operation, that aspect of the overall management system of the organization that determines and implements the quality policy defined in a PSD PQAO's QAPP. Quality management includes strategic planning, allocation of resources and other systematic planning activities ( e.g., 2.3 Data Quality Performance Requirements. 2.3.1 Data Quality Objectives (DQOs). 2.3.1.1 Measurement Uncertainty for Automated and Manual PM 2.5 Methods 2.3.1.2 Measurement Uncertainty for Automated Ozone Methods. 2.3.1.3 Measurement Uncertainty for Pb Methods. 2.3.1.4 Measurement Uncertainty for NO 2 2.3.1.5 Measurement Uncertainty for SO 2. 2.4 National Performance Evaluation Program. 2.5 2.5 2.4.1 Independent Assessment. 2.5 Technical Systems Audit Program. 2.6 Gaseous and Flow Rate Audit Standards. 2.6.1 Gaseous pollutant concentration standards (permeation devices or cylinders of compressed gas) used to obtain test concentrations for CO, SO 2 2 2.6.1.1 The concentrations of EPA Protocol Gas standards used for ambient air monitoring must be certified with a 95-percent confidence interval to have an analytical uncertainty of no more than ±2.0 percent (inclusive) of the certified concentration (tag value) of the gas mixture. The uncertainty must be calculated in accordance with the statistical procedures defined in Reference 4 of this appendix. 2.6.1.2 Specialty gas producers advertising certification with the procedures provided in Reference 4 of this appendix and distributing gases as “EPA Protocol Gas” for ambient air monitoring purposes must adhere to the regulatory requirements specified in 40 CFR 75.21(g) or not use “EPA” in any form of advertising. The PSD PQAOs must provide information to the PSD reviewing authority on the specialty gas producers they use (or will use) for the duration of the PSD monitoring project. This information can be provided in the QAPP or monitoring plan but must be updated if there is a change in the specialty gas producers used. 2.6.2 Test concentrations for ozone (O 3 3 3 2.6.3 Flow rate measurements must be made by a flow measuring instrument that is NIST-traceable to an authoritative volume or other applicable standard. Guidance for certifying some types of flow-meters is provided in reference 10 of this appendix. 2.7 Primary Requirements and Guidance. Requirements and guidance documents for developing the quality system are contained in references 1 through 11 of this appendix, which also contain many suggested procedures, checks, and control specifications. Reference 10 describes specific guidance for the development of a quality system for data collected for comparison to the NAAQS. Many specific quality control checks and specifications for methods are included in the respective reference methods described in Part 50 or in the respective equivalent method descriptions available from the EPA (reference 6 of this appendix). Similarly, quality control procedures related to specifically designated reference and equivalent method monitors are contained in the respective operation or instruction manuals associated with those monitors. For PSD monitoring, the use of reference and equivalent method monitors are required. 3. Measurement Quality Check Requirements This section provides the requirements for PSD PQAOs to perform the measurement quality checks that can be used to assess data quality. Data from these checks are required to be submitted to the PSD reviewing authority within the same time frame as routinely-collected ambient concentration data as described in 40 CFR 58.16. Table B-1 of this appendix provides a summary of the types and frequency of the measurement quality checks that are described in this section. Reporting these results to AQS may be required by the PSD reviewing authority. 3.1 Gaseous monitors of SO 2 NO 2 O 3 and CO 3.1.1 One-Point Quality Control (QC) Check for SO 2, NO 2 O 3 and CO 2 2 3 2 2 3 (b) Point analyzers must operate in their normal sampling mode during the QC check and the test atmosphere must pass through all filters, scrubbers, conditioners and other components used during normal ambient sampling and as much of the ambient air inlet system as is practicable. The QC check must be conducted before any calibration or adjustment to the monitor. (c) Open-path monitors are tested by inserting a test cell containing a QC check gas concentration into the optical measurement beam of the instrument. If possible, the normally used transmitter, receiver, and as appropriate, reflecting devices should be used during the test and the normal monitoring configuration of the instrument should be altered as little as possible to accommodate the test cell for the test. However, if permitted by the associated operation or instruction manual, an alternate local light source or an alternate optical path that does not include the normal atmospheric monitoring path may be used. The actual concentration of the QC check gas in the test cell must be selected to produce an effective concentration in the range specified earlier in this section. Generally, the QC test concentration measurement will be the sum of the atmospheric pollutant concentration and the QC test concentration. As such, the result must be corrected to remove the atmospheric concentration contribution. The corrected concentration is obtained by subtracting the average of the atmospheric concentrations measured by the open path instrument under test immediately before and immediately after the QC test from the QC check gas concentration measurement. If the difference between these before and after measurements is greater than 20 percent of the effective concentration of the test gas, discard the test result and repeat the test. If possible, open path monitors should be tested during periods when the atmospheric pollutant concentrations are relatively low and steady. (d) Report the audit concentration of the QC gas and the corresponding measured concentration indicated by the monitor. The percent differences between these concentrations are used to assess the precision and bias of the monitoring data as described in sections 4.1.2 (precision) and 4.1.3 (bias) of this appendix. 3.1.2 Quarterly performance evaluation for SO 2, NO 2 , O 3 , or CO 3.1.2.1 The evaluation is made by challenging the monitor with audit gas standards of known concentration from at least three audit levels. One point must be within two to three times the method detection limit of the instruments within the PQAOs network, the second point will be less than or equal to the 99th percentile of the data at the site or the network of sites in the PQAO or the next highest audit concentration level. The third point can be around the primary NAAQS or the highest 3-year concentration at the site or the network of sites in the PQAO. An additional 4th level is encouraged for those PSD organizations that would like to confirm the monitor's linearity at the higher end of the operational range. In rare circumstances, there may be sites measuring concentrations above audit level 10. These sites should be identified to the PSD reviewing authority. Audit level Concentration range, ppm O 3 SO 2 NO 2 CO 1 0.004-0.0059 0.0003-0.0029 0.0003-0.0029 0.020-0.059 2 0.006-0.019 0.0030-0.0049 0.0030-0.0049 0.060-0.199 3 0.020-0.039 0.0050-0.0079 0.0050-0.0079 0.200-0.899 4 0.040-0.069 0.0080-0.0199 0.0080-0.0199 0.900-2.999 5 0.070-0.089 0.0200-0.0499 0.0200-0.0499 3.000-7.999 6 0.090-0.119 0.0500-0.0999 0.0500-0.0999 8.000-15.999 7 0.120-0.139 0.1000-0.1499 0.1000-0.2999 16.000-30.999 8 0.140-0.169 0.1500-0.2599 0.3000-0.4999 31.000-39.999 9 0.170-0.189 0.2600-0.7999 0.5000-0.7999 40.000-49.999 10 0.190-0.259 0.8000-1.000 0.8000-1.000 50.000-60.000 3.1.2.2 [Reserved] 3.1.2.3 The standards from which audit gas test concentrations are obtained must meet the specifications of section 2.6.1 of this appendix. 3.1.2.4 For point analyzers, the evaluation shall be carried out by allowing the monitor to analyze the audit gas test atmosphere in its normal sampling mode such that the test atmosphere passes through all filters, scrubbers, conditioners, and other sample inlet components used during normal ambient sampling and as much of the ambient air inlet system as is practicable. 3.1.2.5 Open-path monitors are evaluated by inserting a test cell containing the various audit gas concentrations into the optical measurement beam of the instrument. If possible, the normally used transmitter, receiver, and, as appropriate, reflecting devices should be used during the evaluation, and the normal monitoring configuration of the instrument should be modified as little as possible to accommodate the test cell for the evaluation. However, if permitted by the associated operation or instruction manual, an alternate local light source or an alternate optical path that does not include the normal atmospheric monitoring path may be used. The actual concentrations of the audit gas in the test cell must be selected to produce effective concentrations in the evaluation level ranges specified in this section of this appendix. Generally, each evaluation concentration measurement result will be the sum of the atmospheric pollutant concentration and the evaluation test concentration. As such, the result must be corrected to remove the atmospheric concentration contribution. The corrected concentration is obtained by subtracting the average of the atmospheric concentrations measured by the open-path instrument under test immediately before and immediately after the evaluation test (or preferably before and after each evaluation concentration level) from the evaluation concentration measurement. If the difference between the before and after measurements is greater than 20 percent of the effective concentration of the test gas standard, discard the test result for that concentration level and repeat the test for that level. If possible, open-path monitors should be evaluated during periods when the atmospheric pollutant concentrations are relatively low and steady. Also, if the open-path instrument is not installed in a permanent manner, the monitoring path length must be reverified to be within ±3 percent to validate the evaluation, since the monitoring path length is critical to the determination of the effective concentration. 3.1.2.6 Report both the evaluation concentrations (effective concentrations for open-path monitors) of the audit gases and the corresponding measured concentration (corrected concentrations, if applicable, for open-path monitors) indicated or produced by the monitor being tested. The percent differences between these concentrations are used to assess the quality of the monitoring data as described in section 4.1.1 of this appendix. 3.1.3 National Performance Audit Program (NPAP). 3.1.3.1 Performing audits on 100 percent of monitors and sites each year including monitors and sites that may be operated for less than 1 year. The PSD reviewing authority has the authority to require more frequent audits at sites they consider to be high priority. 3.1.3.2 Developing a delivery system that will allow for the audit concentration gasses to be introduced at the probe inlet where logistically feasible. 3.1.3.3 Using audit gases that are verified against the NIST standard reference methods or special review procedures and validated per the certification periods specified in Reference 4 of this appendix (EPA Traceability Protocol for Assay and Certification of Gaseous Calibration Standards) for CO, SO 2 2 3 3.1.3.4 The PSD PQAO may elect to self-implement NPAP. In these cases, the PSD reviewing authority will work with those PSD PQAOs to establish training and other technical requirements to establish comparability to federally implemented programs. In addition to meeting the requirements in sections 3.1.1.3 through 3.1.3.3, the PSD PQAO must: (a) Ensure that the PSD audit system is equivalent to the EPA NPAP audit system and is an entirely separate set of equipment and standards from the equipment used for quarterly performance evaluations. If this system does not generate and analyze the audit concentrations, as the EPA NPAP system does, its equivalence to the EPA NPAP system must be proven to be as accurate under a full range of appropriate and varying conditions as described in section 3.1.3.6. (b) Perform a whole system check by having the PSD audit system tested at an independent and qualified EPA lab, or equivalent. (c) Evaluate the system with the EPA NPAP program through collocated auditing at an acceptable number of sites each year (at least one for a PSD network of five or less sites; at least two for a network with more than five sites). (d) Incorporate the NPAP into the PSD PQAO's QAPP. (e) Be subject to review by independent, EPA-trained personnel. (f) Participate in initial and update training/certification sessions. 3.2 PM 2.5 3.2.1 Flow Rate Verification for PM 2.5 2.5 3.2.2 Semi-Annual Flow Rate Audit for PM 2.5 2.5 3.2.3 Collocated Sampling Procedures for PM 2.5 3.2.3.1 For each pair of collocated monitors, designate one sampler as the primary monitor whose concentrations will be used to report air quality for the site, and designate the other as the QC monitor. There can be only one primary monitor at a monitoring site for a given time period. (a) If the primary monitor is a FRM, then the quality control monitor must be a FRM of the same method designation. (b) If the primary monitor is a FEM, then the quality control monitor must be a FRM unless the PSD PQAO submits a waiver for this requirement, provides a specific reason why a FRM cannot be implemented, and the waiver is approved by the PSD reviewing authority. If the waiver is approved, then the quality control monitor must be the same method designation as the primary FEM monitor. 3.2.3.2 In addition, the collocated monitors should be deployed according to the following protocol: (a) The collocated quality control monitor(s) should be deployed at sites with the highest predicted daily PM 2.5 2.5 (b) The two collocated monitors must be within 4 meters of each other and at least 2 meters apart for flow rates greater than 200 liters/min or at least 1 meter apart for samplers having flow rates less than 200 liters/min to preclude airflow interference. A waiver allowing up to 10 meters horizontal distance and up to 3 meters vertical distance (inlet to inlet) between a primary and collocated quality control monitor may be approved by the PSD reviewing authority for sites at a neighborhood or larger scale of representation. This waiver may be approved during the QAPP review and approval process. Sampling and analytical methodologies must be the consistently implemented for both collocated samplers and for all other samplers in the network. (c) Sample the collocated quality control monitor on a 6-day schedule for sites not requiring daily monitoring and on a 3-day schedule for any site requiring daily monitoring. Report the measurements from both primary and collocated quality control monitors at each collocated sampling site. The calculations for evaluating precision between the two collocated monitors are described in section 4.2.1 of this appendix. 3.2.4 PM 2.5 Performance Evaluation Program (PEP) Procedures. 3.2.4.1 Have each method designation evaluated each year; and, 3.2.4.2 Have all FRM and FEM samplers subject to a PEP audit at least once every 6 years, which equates to approximately 15 percent of the monitoring sites audited each year. 3.2.4.3 Additional information concerning the PEP is contained in Reference 10 of this appendix. The calculations for evaluating bias between the primary monitor and the performance evaluation monitor for PM 2.5 3.3 PM 10 3.3.1 Flow Rate Verification for PM 10 10 3.3.2 Semi-Annual Flow Rate Audit for PM 10 10 3.3.3 Collocated Sampling Procedures for Manual PM 10 3.3.3.1 For each pair of collocated monitors, designate one sampler as the primary monitor whose concentrations will be used to report air quality for the site, and designate the other as the quality control monitor. 3.3.3.2 In addition, the collocated monitors should be deployed according to the following protocol: (a) The collocated quality control monitor(s) should be deployed at sites with the highest predicted daily PM 10 10 (b) The two collocated monitors must be within 4 meters of each other and at least 2 meters apart for flow rates greater than 200 liters/min or at least 1 meter apart for samplers having flow rates less than 200 liters/min to preclude airflow interference. A waiver allowing up to 10 meters horizontal distance and up to 3 meters vertical distance (inlet to inlet) between a primary and collocated sampler may be approved by the PSD reviewing authority for sites at a neighborhood or larger scale of representation. This waiver may be approved during the QAPP review and approval process. Sampling and analytical methodologies must be the consistently implemented for both collocated samplers and for all other samplers in the network. (c) Sample the collocated quality control monitor on a 6-day schedule or 3-day schedule for any site requiring daily monitoring. Report the measurements from both primary and collocated quality control monitors at each collocated sampling site. The calculations for evaluating precision between the two collocated monitors are described in section 4.2.1 of this appendix. (d) In determining the number of collocated sites required for PM 10 10 10 10 10 10 3.4 Pb. 3.4.1 Flow Rate Verification for Pb. 3.4.2 Semi-Annual Flow Rate Audit for Pb. 3.4.3 Collocated Sampling for Pb. 3.4.3.1 For each pair of collocated monitors, designate one sampler as the primary monitor whose concentrations will be used to report air quality for the site, and designate the other as the quality control monitor. 3.4.3.2 In addition, the collocated monitors should be deployed according to the following protocol: (a) The collocated quality control monitor(s) should be deployed at sites with the highest predicted daily Pb concentrations in the network. If the highest Pb concentration site is impractical for collocation purposes, alternative sites approved by the PSD reviewing authority may be selected. (b) The two collocated monitors must be within 4 meters of each other and at least 2 meters apart for flow rates greater than 200 liters/min or at least 1 meter apart for samplers having flow rates less than 200 liters/min to preclude airflow interference. A waiver allowing up to 10 meters horizontal distance and up to 3 meters vertical distance (inlet to inlet) between a primary and collocated sampler may be approved by the PSD reviewing authority for sites at a neighborhood or larger scale of representation. This waiver may be approved during the QAPP review and approval process. Sampling and analytical methodologies must be the consistently implemented for both collocated samplers and all other samplers in the network. (c) Sample the collocated quality control monitor on a 6-day schedule if daily monitoring is not required or 3-day schedule for any site requiring daily monitoring. Report the measurements from both primary and collocated quality control monitors at each collocated sampling site. The calculations for evaluating precision between the two collocated monitors are described in section 4.2.1 of this appendix. (d) In determining the number of collocated sites required for Pb-PM 10 10 10 10 10 10 10 3.4.4 Pb Analysis Audits. Range Equivalent ambient 3 1 30-100% of Pb NAAQS. 2 200-300% of Pb NAAQS. (a) Audit samples must be extracted using the same extraction procedure used for exposed filters. (b) Analyze three audit samples in each of the two ranges each quarter samples are analyzed. The audit sample analyses shall be distributed as much as possible over the entire calendar quarter. (c) Report the audit concentrations (in µg Pb/filter or strip) and the corresponding measured concentrations (in µg Pb/filter or strip) using AQS unit code 077 (if reporting to AQS). The percent differences between the concentrations are used to calculate analytical accuracy as described in section 4.2.5 of this appendix. 3.4.5 Pb Performance Evaluation Program (PEP) Procedures. 4. Calculations for Data Quality Assessments (a) Calculations of measurement uncertainty are carried out by PSD PQAO according to the following procedures. The PSD PQAOs should report the data for all appropriate measurement quality checks as specified in this appendix even though they may elect to perform some or all of the calculations in this section on their own. (b) At low concentrations, agreement between the measurements of collocated samplers, expressed as relative percent difference or percent difference, may be relatively poor. For this reason, collocated measurement pairs will be selected for use in the precision and bias calculations only when both measurements are equal to or above the following limits: (1) Pb: 0.002 µg/m 3 (2) Pb: 0.02 µg/m 3 (3) PM 10 3 (4) PM 10 3 (5) PM 2.5 3 (c) The PM 2.5 3 2.5 4.1 Statistics for the Assessment of QC Checks for SO 2 , NO 2 , 3 and CO 4.1.1 Percent Difference. d i where meas audit 4.1.2 Precision Estimate. 2 2 3 where n 2 0.1,n-1 4.1.3 Bias Estimate. 2 2 3 where n 0.95,n-1 AB d i′s and the quantity AS d i′s 4.1.3.1 Assigning a sign (positive/negative) to the bias estimate. 4.1.3.2 Calculate the 25th and 75th percentiles of the percent differences for each site. The absolute bias upper bound should be flagged as positive if both percentiles are positive and negative if both percentiles are negative. The absolute bias upper bound would not be flagged if the 25th and 75th percentiles are of different signs. 4.2 Statistics for the Assessment of PM 10, PM 2.5 , and Pb 4.2.1 Collocated Quality Control Sampler Precision Estimate for PM 10, PM 2.5 , and Pb t i , Equation 6 to Section 4.2.1 of Appendix B Where X i Y i Where k 2 0.1,k-1 t i 4.2.2 One-Point Flow Rate Verification Bias Estimate for PM 10 , PM 2.5 and Pb meas audit n 0.95,n-1 AB d i′s AS d i′s 4.2.3 Semi-Annual Flow Rate Audit Bias Estimate for PM 10 , PM 2.5 and Pb 4.2.4 Performance Evaluation Programs Bias Estimate for Pb. 4.2.5 Performance Evaluation Programs Bias Estimate for PM 2.5 i 4.2.6 Pb Analysis Audit Bias Estimate. 5. Reporting Requirements 5.1. Quarterly Reports. 6. References (1) American National Standard Institute—Quality Management Systems For Environmental Information And Technology Programs—Requirements With Guidance For Use. ASQ/ANSI E4-2014. February 2014. Available from ANSI Webstore https://webstore.ansi.org/. (2) EPA Requirements for Quality Management Plans. EPA QA/R-2. EPA/240/B-01/002. March 2001, Reissue May 2006. Office of Environmental Information, Washington, DC 20460. http://www.epa.gov/quality/agency-wide-quality-system-documents. (3) EPA Requirements for Quality Assurance Project Plans for Environmental Data Operations. EPA QA/R-5. EPA/240/B-01/003. March 2001, Reissue May 2006. Office of Environmental Information, Washington, DC 20460. http://www.epa.gov/quality/agency-wide-quality-system-documents. (4) EPA Traceability Protocol for Assay and Certification of Gaseous Calibration Standards. EPA-600/R-12/531. May, 2012. Available from U.S. Environmental Protection Agency, National Risk Management Research Laboratory, Research Triangle Park NC 27711. https://www.epa.gov/nscep. (5) Guidance for the Data Quality Objectives Process. EPA QA/G-4. EPA/240/B-06/001. February, 2006. Office of Environmental Information, Washington, DC 20460. http://www.epa.gov/quality/agency-wide-quality-system-documents. (6) List of Designated Reference and Equivalent Methods. Available from U.S. Environmental Protection Agency, Center for Environmental Measurements and Modeling, Air Methods and Characterization Division, MD-D205-03, Research Triangle Park, NC 27711. https://www.epa.gov/amtic/air-monitoring-methods-criteria-pollutants. (7) Transfer Standards for the Calibration of Ambient Air Monitoring Analyzers for Ozone. EPA-454/B-13-004 U.S. Environmental Protection Agency, Research Triangle Park, NC 27711, October, 2013. https://www.epa.gov/sites/default/files/2020-09/documents/ozonetransferstandardguidance.pdf. (8) Paur, R.J. and F.F. McElroy. Technical Assistance Document for the Calibration of Ambient Ozone Monitors. EPA-600/4-79-057. U.S. Environmental Protection Agency, Research Triangle Park, NC 27711, September, 1979. http://www.epa.gov/ttn/amtic/cpreldoc.html. (9) Quality Assurance Handbook for Air Pollution Measurement Systems, Volume 1—A Field Guide to Environmental Quality Assurance. EPA-600/R-94/038a. April 1994. Available from U.S. Environmental Protection Agency, ORD Publications Office, Center for Environmental Research Information (CERI), 26 W. Martin Luther King Drive, Cincinnati, OH 45268. https://www.epa.gov/amtic/ambient-air-monitoring-quality-assurance#documents. (10) Quality Assurance Handbook for Air Pollution Measurement Systems, Volume II: Ambient Air Quality Monitoring Program Quality System Development. EPA-454/B-13-003. https://www.epa.gov/amtic/ambient-air-monitoring-quality-assurance#documents. (11) National Performance Evaluation Program Standard Operating Procedures. https://www.epa.gov/amtic/ambient-air-monitoring-quality-assurance#npep. Table B-1 to Section 6 of Appendix B- Minimum Data Assessment Requirements for NAAQS Related Criteria Pollutant PSD Monitors Method Assessment Coverage Minimum Parameters AQS Gaseous Methods (CO, NO 2 2 3 One-Point QC for SO 2 2 3 Response check at concentration 0.005-0.08 ppm SO 2 2 3 Each analyzer Once per 2 weeks 5 Audit concentration 1 2 One-Point QC. Quarterly performance evaluation for SO 2 2 3 See section 3.1.2 of this appendix Each analyzer Once per quarter 5 Audit concentration 1 2 Annual PE. NPAP for SO 2 2 3 3 Independent Audit Each primary monitor Once per year Audit concentration 1 2 NPAP. Particulate Methods: Collocated sampling PM 10 2.5 Collocated samplers 1 per PSD Network per pollutant Every 6 days or every 3 days if daily monitoring required Primary sampler concentration and duplicate sampler concentration 4 No Transaction reported as raw data. Flow rate verification PM 10 2.5 Check of sampler flow rate Each sampler Once every month 5 Audit flow rate and measured flow rate indicated by the sampler Flow Rate Verification. Semi-annual flow rate audit PM 10 2.5 Check of sampler flow rate using independent standard Each sampler Once every 6 months or beginning, middle and end of monitoring 5 Audit flow rate and measured flow rate indicated by the sampler Semi Annual Flow Rate Audit. Pb analysis audits Pb-TSP, Pb-PM 10 Check of analytical system with Pb audit strips/filters Analytical Each quarter 5 Measured value and audit value (ug Pb/filter) using AQS unit code 077 for parameters: Pb Analysis Audits. Performance Evaluation Program PM 2.5 3 Collocated samplers (1) 5 valid audits for PQAOs with <= 5 sites. Over all 4 quarters 5 Primary sampler concentration and performance evaluation sampler concentration PEP. Performance Evaluation Program Pb 3 Collocated samplers (1) 1 valid audit and 4 collocated samples for PQAOs, with <=5 sites. Over all 4 quarters 5 Primary sampler concentration and performance evaluation sampler concentration. Primary sampler concentration and duplicate sampler concentration PEP. 1 2 3 2.5 4 5 [81 FR 17290, Mar. 28, 2016, as amended at 89 FR 16392, Mar. 6, 2024; 89 FR 103655, Dec. 19, 2024] Appendix C to Part 58—Ambient Air Quality Monitoring Methodology 1.0 Purpose 2.0 SLAMS Ambient Air Monitoring Stations 3.0 NCore Ambient Air Monitoring Stations 4.0 Photochemical Assessment Monitoring Stations (PAMS) 5.0 Particulate Matter Episode Monitoring 6.0 References 1.0 Purpose This appendix specifies the criteria pollutant monitoring methods (manual methods or automated analyzers) which must be used in SLAMS and NCore stations that are a subset of SLAMS. 2.0 SLAMS Ambient Air Monitoring Network 2.1 Except as otherwise provided in this appendix, a criteria pollutant monitoring method used for making NAAQS decisions at a SLAMS site must be a reference or equivalent method as defined in § 50.1 of this chapter. 2.1.1 Any NO 2 2.2 PM 10 2.5 10-2.5 2.2.1 Data to demonstrate a calibration may include valid data from State, local, or Tribal air agencies or data collected by instrument manufacturers in accordance with 40 CFR 53.35 or other data approved by the Administrator. 2.2.2 A request to update a designated methods calibration may be initiated by the instrument manufacturer of record or the EPA Administrator. State, local, Tribal, and multijurisdictional organizations of these entities may work with an instrument manufacture to update a designated method calibration. 2.2.3 Requests for approval of an updated PM 10 2.5 10-2.5 2.2.4 Data included in the request should represent a subset of representative locations where the method is operational. For cases with a small number of collocated FRMs and continuous FEMs sites, an updated candidate calibration may be limited to the sites where both methods are in use. 2.2.5 Data included in a candidate method updated calibration may include a subset of sites where there is a large grouping of sites in one part of the country such that the updated calibration would be representative of the country as a whole. 2.2.6 Improvements should be national in scope and ideally implemented through a firmware change. 2.2.7 The goal of a change to a methods calibration is to increase the number of sites meeting measurements quality objectives of the method as identified in section 2.3.1.1 of appendix A to this part. 2.2.8 For meeting measurement quality objectives (MQOs), the primary objective is to meet the bias goal as this statistic will likely have the most influence on improving the resultant data collected. 2.2.9 Precision data are to be included, but so long as precision data are at least as good as existing network data or meet the MQO referenced in section 2.2.8 of this appendix, no further work is necessary with precision. 2.2.10 Data available to use may include routine primary and collocated data. 2.2.11 Audit data may be useful to confirm the performance of a candidate updated calibration but should not be used as the basis of the calibration to keep the independence of the audit data. 2.2.12 Data utilized as the basis of the updated calibration may be obtained by accessing EPA's AQS database or future analogous EPA database. 2.2.13 Years of data to use in a candidate method calibration should include two recent years where we are past the certification period for the previous year's data, which is May 1 of each year. 2.2.14 Data from additional years is to be used to test an updated calibration such that the calibration is independent of the test years of interest. Data from these additional years need to minimally demonstrate that a larger number of sites are expected to meet bias MQO especially at sites near the level of the NAAQS for the PM indicator of interest. 2.2.15 Outliers may be excluded using routine outlier tests. 2.2.16 The range of data used in a calibration may include all data available or alternatively use data in the range from the lowest measured data available up to 125% of the 24-hour NAAQS for the PM indicator of interest. 2.2.17 Other improvements to a PM continuous method may be included as part of a recommended update so long as appropriate testing is conducted with input from EPA's Office of Research and Development (ORD) Reference and Equivalent (R&E) Methods Designation program. 2.2.18 EPA encourages early communication by instrument manufacturers considering an update to a PM method. Instrument companies should initiate such dialogue by contacting EPA's ORD R&E Methods Designation program. The contact information for this can be found at 40 CFR 53.4. 2.2.19 Manufacturers interested in improving instrument's performance through an updated factory calibration must submit a written modification request to EPA with supporting rationale. Because the testing requirements and acceptance criteria of any field and/or lab tests can depend upon the nature and extent of the intended modification, applicants should contact EPA's R&E Methods Designation program for guidance prior to development of the modification request. 2.3 Any manual method or analyzer purchased prior to cancellation of its reference or equivalent method designation under § 53.11 or § 53.16 of this chapter may be used at a SLAMS site following cancellation for a reasonable period of time to be determined by the Administrator. 2.4-2.5 [Reserved] 2.6 Use of Methods With Higher, Nonconforming Ranges in Certain Geographical Areas. 2.6.1 [Reserved] 2.6.2 An analyzer may be used (indefinitely) on a range which extends to concentrations higher than two times the upper limit specified in table B-1 of part 53 of this chapter if: 2.6.2.1 The analyzer has more than one selectable range and has been designated as a reference or equivalent method on at least one of its ranges, or has been approved for use under section 2.5 (which applies to analyzers purchased before February 18, 1975); 2.6.2.2 The pollutant intended to be measured with the analyzer is likely to occur in concentrations more than two times the upper range limit specified in table B-1 of part 53 of this chapter in the geographical area in which use of the analyzer is proposed; and 2.6.2.3 The Administrator determines that the resolution of the range or ranges for which approval is sought is adequate for its intended use. For purposes of this section (2.6), “resolution” means the ability of the analyzer to detect small changes in concentration. 2.6.3 Requests for approval under section 2.6.2 of this appendix must meet the submittal requirements of section 2.7. Except as provided in section 2.7.3 of this appendix, each request must contain the information specified in section 2.7.2 in addition to the following: 2.6.3.1 The range or ranges proposed to be used; 2.6.3.2 Test data, records, calculations, and test results as specified in section 2.7.2.2 of this appendix for each range proposed to be used; 2.6.3.3 An identification and description of the geographical area in which use of the analyzer is proposed; 2.6.3.4 Data or other information demonstrating that the pollutant intended to be measured with the analyzer is likely to occur in concentrations more than two times the upper range limit specified in table B-1 of part 53 of this chapter in the geographical area in which use of the analyzer is proposed; and 2.6.3.5 Test data or other information demonstrating the resolution of each proposed range that is broader than that permitted by section 2.5 of this appendix. 2.6.4 Any person who has obtained approval of a request under this section (2.6.2) shall assure that the analyzer for which approval was obtained is used only in the geographical area identified in the request and only while operated in the range or ranges specified in the request. 2.7 Requests for Approval; Withdrawal of Approval. 2.7.1 Requests for approval under section 2.2, 2.6.2, or 2.8 of this appendix must be submitted to: Director, Center for Environmental Measurement and Modeling, Reference and Equivalent Methods Designation Program (MD-D205-03), U.S. Environmental Protection Agency, P.O. Box 12055, Research Triangle Park, North Carolina 27711. 2.7.2 Except as provided in section 2.7.3 of this appendix, each request must contain: 2.7.2.1 A statement identifying the analyzer (e.g., by serial number) and the method of which the analyzer is representative (e.g., by manufacturer and model number); and 2.7.2.2 Test data, records, calculations, and test results for the analyzer (or the method of which the analyzer is representative) as specified in subpart B, subpart C, or both (as applicable) of part 53 of this chapter. 2.7.3 A request may concern more than one analyzer or geographical area and may incorporate by reference any data or other information known to EPA from one or more of the following: 2.7.3.1 An application for a reference or equivalent method determination submitted to EPA for the method of which the analyzer is representative, or testing conducted by the applicant or by EPA in connection with such an application; 2.7.3.2 Testing of the method of which the analyzer is representative at the initiative of the Administrator under § 53.7 of this chapter; or 2.7.3.3 A previous or concurrent request for approval submitted to EPA under this section (2.7). 2.7.4 To the extent that such incorporation by reference provides data or information required by this section (2.7) or by section 2.5 or 2.6 of this appendix, independent data or duplicative information need not be submitted. 2.7.5 After receiving a request under this section (2.7), the Administrator may request such additional testing or information or conduct such tests as may be necessary in his judgment for a decision on the request. 2.7.6 If the Administrator determines, on the basis of any available information, that any of the determinations or statements on which approval of a request under this section was based are invalid or no longer valid, or that the requirements of section 2.5 or 2.6, as applicable, have not been met, he/she may withdraw the approval after affording the person who obtained the approval an opportunity to submit information and arguments opposing such action. 2.8 Modifications of Methods by Users. 2.8.1 Except as otherwise provided in this section, no reference method or equivalent method may be used in a SLAMS network if it has been modified in a manner that could significantly alter the performance characteristics of the method without prior approval by the Administrator. For purposes of this section, “alternative method” means an analyzer, the use of which has been approved under section 2.5 or 2.6 of this appendix or some combination thereof. 2.8.2 Requests for approval under this section (2.8) must meet the submittal requirements of sections 2.7.1 and 2.7.2.1 of this appendix. 2.8.3 Each request submitted under this section (2.8) must include: 2.8.3.1 A description, in such detail as may be appropriate, of the desired modification; 2.8.3.2 A brief statement of the purpose(s) of the modification, including any reasons for considering it necessary or advantageous; 2.8.3.3 A brief statement of belief concerning the extent to which the modification will or may affect the performance characteristics of the method; and 2.8.3.4 Such further information as may be necessary to explain and support the statements required by sections 2.8.3.2 and 2.8.3.3. 2.8.4 The Administrator will approve or disapprove the modification by letter to the person or agency requesting such approval within 75 days after receiving a request for approval under this section and any further information that the applicant may be asked to provide. 2.8.5 A temporary modification that could alter the performance characteristics of a reference or equivalent may be made without prior approval under this section if the method is not functioning or is malfunctioning, provided that parts necessary for repair in accordance with the applicable operation manual cannot be obtained within 45 days. Unless such temporary modification is later approved under section 2.8.4 of this appendix, the temporarily modified method shall be repaired in accordance with the applicable operation manual as quickly as practicable but in no event later than 4 months after the temporary modification was made, unless an extension of time is granted by the Administrator. Unless and until the temporary modification is approved, air quality data obtained with the method as temporarily modified must be clearly identified as such when submitted in accordance with § 58.16 and must be accompanied by a report containing the information specified in section 2.8.3 of this appendix. A request that the Administrator approve a temporary modification may be submitted in accordance with sections 2.8.1 through 2.8.4 of this appendix. In such cases, the request will be considered as if a request for prior approval had been made. 2.9 Use of IMPROVE Samplers at a SLAMS Site. “IMPROVE” samplers may be used in SLAMS for monitoring of regional background and regional transport concentrations of fine particulate matter. The IMPROVE samplers were developed for use in the Interagency Monitoring of Protected Visual Environments (IMPROVE) network to characterize all of the major components and many trace constituents of the particulate matter that impair visibility in Federal Class I Areas. Descriptions of the IMPROVE samplers and the data they collect are available in references 4, 5, and 6 of this appendix. 2.10 Use of Pb-PM 10 at SLAMS Sites. 2.10.1 The EPA Regional Administrator may approve the use of a Pb-PM 10 10 2.10.1.1 Pb-PM 10 10 2.10.1.2 Pb-PM 10 10 2.10.2 The approval of a Pb-PM 10 10 10 3.0 Ncore Ambient Air Monitoring Stations 3.1 Methods employed in NCore multipollutant sites used to measure SO 2 2 3 2.5 10-2.5 3.2 If alternative SO 2 2 3 2.5 10-2.5 4.0 Photochemical Assessment Monitoring Stations (PAMS) 4.1 Methods used for O 3 4.2 Methods used for NO, NO 2 X 2 2 X 4.3 Methods for meteorological measurements and speciated VOC monitoring are included in the guidance provided in references 2 and 3 of this appendix. If alternative VOC monitoring methodology (including the use of new or innovative technologies), which is not included in the guidance, is proposed, it must be detailed in the network description required by § 58.10 and subsequently approved by the Administrator. 5.0 Particulate Matter Episode Monitoring 5.1 For short-term measurements of PM 10 5.1.1 Either the “Staggered PM 10 10 10 5.1.2 Any other method for measuring PM 10 5.1.2.1 Which has a measurement range or ranges appropriate to accurately measure air pollution episode concentration of PM 10 5.1.2.2 Which has a sample period appropriate for short-term PM 10 5.1.2.3 For which a quantitative relationship to a reference or equivalent method for PM 10 5.2 PM 10 10 6.0 References 1. Pelton, D. J. Guideline for Particulate Episode Monitoring Methods, GEOMET Technologies, Inc., Rockville, MD. Prepared for U.S. Environmental Protection Agency, Research Triangle Park, NC. EPA Contract No. 68-02-3584. EPA 450/4-83-005. February 1983. 2. Technical Assistance Document For Sampling and Analysis of Ozone Precursors. Atmospheric Research and Exposure Assessment Laboratory, U.S. Environmental Protection Agency, Research Triangle Park, NC 27711. EPA 600/8-91-215. October 1991. 3. Quality Assurance Handbook for Air Pollution Measurement Systems: Volume IV. Meteorological Measurements. Atmospheric Research and Exposure Assessment Laboratory, U.S. Environmental Protection Agency, Research Triangle Park, NC 27711. EPA 600/4-90-0003. August 1989. 4. Eldred, R.A., Cahill, T.A., Wilkenson, L.K., et al., 5. Sisler, J.F., Huffman, D., and Latimer, D.A.; Spatial and temporal patterns and the chemical composition of the haze in the United States: An analysis of data from the IMPROVE network, 1988-1991, ISSN No. 0737-5253-26, National Park Service, Ft. Collins, CO, 1993. 6. Eldred, R.A., Cahill, T.A., Pitchford, M., and Malm, W.C.; IMPROVE—a new remote area particulate monitoring system for visibility studies, Proceedings of the 81st Annual Meeting of the Air Pollution Control Association, Dallas, Paper 88-54.3, 1988. 7. Data Quality Objectives (DQOs) for Relating Federal Reference Method (FRM) and Continuous PM 2.5 [71 FR 61313, Oct. 17, 2006, as amended at 73 FR 67061, Nov. 12, 2008; 75 FR 6534, Feb. 9, 2010; 89 FR 16395, Mar. 6, 2024; 89 FR 103655, Dec. 19, 2024] Appendix D to Part 58—Network Design Criteria for Ambient Air Quality Monitoring 1. Monitoring Objectives and Spatial Scales 2. General Monitoring Requirements 3. Design Criteria for NCore Sites 4. Pollutant-Specific Design Criteria for SLAMS Sites 5. Design Criteria for Photochemical Assessment Monitoring Stations (PAMS) 6. References 1. Monitoring Objectives and Spatial Scales The purpose of this appendix is to describe monitoring objectives and general criteria to be applied in establishing the required SLAMS ambient air quality monitoring stations and for choosing general locations for additional monitoring sites. This appendix also describes specific requirements for the number and location of FRM and FEM sites for specific pollutants, NCore multipollutant sites, PM 10 2.5 2.5 3 1.1 Monitoring Objectives. The ambient air monitoring networks must be designed to meet three basic monitoring objectives. These basic objectives are listed below. The appearance of any one objective in the order of this list is not based upon a prioritized scheme. Each objective is important and must be considered individually. (a) Provide air pollution data to the general public in a timely manner. Data can be presented to the public in a number of attractive ways including through air quality maps, newspapers, Internet sites, and as part of weather forecasts and public advisories. (b) Support compliance with ambient air quality standards and emissions strategy development. Data from FRM and FEM monitors for NAAQS pollutants will be used for comparing an area's air pollution levels against the NAAQS. Data from monitors of various types can be used in the development of attainment and maintenance plans. SLAMS, and especially NCore station data, will be used to evaluate the regional air quality models used in developing emission strategies, and to track trends in air pollution abatement control measures' impact on improving air quality. In monitoring locations near major air pollution sources, source-oriented monitoring data can provide insight into how well industrial sources are controlling their pollutant emissions. (c) Support for air pollution research studies. Air pollution data from the NCore network can be used to supplement data collected by researchers working on health effects assessments and atmospheric processes, or for monitoring methods development work. 1.1.1 In order to support the air quality management work indicated in the three basic air monitoring objectives, a network must be designed with a variety of types of monitoring sites. Monitoring sites must be capable of informing managers about many things including the peak air pollution levels, typical levels in populated areas, air pollution transported into and outside of a city or region, and air pollution levels near specific sources. To summarize some of these sites, here is a listing of six general site types: (a) Sites located to determine the highest concentrations expected to occur in the area covered by the network. (b) Sites located to measure typical concentrations in areas of high population density. (c) Sites located to determine the impact of significant sources or source categories on air quality. (d) Sites located to determine general background concentration levels. (e) Sites located to determine the extent of regional pollutant transport among populated areas; and in support of secondary standards. (f) Sites located to measure air pollution impacts on visibility, vegetation damage, or other welfare-based impacts. 1.1.2 This appendix contains criteria for the basic air monitoring requirements. The total number of monitoring sites that will serve the variety of data needs will be substantially higher than these minimum requirements provide. The optimum size of a particular network involves trade-offs among data needs and available resources. This regulation intends to provide for national air monitoring needs, and to lend support for the flexibility necessary to meet data collection needs of area air quality managers. The EPA, State, and local agencies will periodically collaborate on network design issues through the network assessment process outlined in § 58.10. 1.1.3 This appendix focuses on the relationship between monitoring objectives, site types, and the geographic location of monitoring sites. Included are a rationale and set of general criteria for identifying candidate site locations in terms of physical characteristics which most closely match a specific monitoring objective. The criteria for more specifically locating the monitoring site, including spacing from roadways and vertical and horizontal probe and path placement, are described in appendix E to this part. 1.2 Spatial Scales. (a) To clarify the nature of the link between general monitoring objectives, site types, and the physical location of a particular monitor, the concept of spatial scale of representativeness is defined. The goal in locating monitors is to correctly match the spatial scale represented by the sample of monitored air with the spatial scale most appropriate for the monitoring site type, air pollutant to be measured, and the monitoring objective. (b) Thus, spatial scale of representativeness is described in terms of the physical dimensions of the air parcel nearest to a monitoring site throughout which actual pollutant concentrations are reasonably similar. The scales of representativeness of most interest for the monitoring site types described above are as follows: (1) Microscale (2) Middle scale (3) Neighborhood scale (4) Urban scale (5) Regional scale (6) National and global scales (c) Proper siting of a monitor requires specification of the monitoring objective, the types of sites necessary to meet the objective, and then the desired spatial scale of representativeness. For example, consider the case where the objective is to determine NAAQS compliance by understanding the maximum ozone concentrations for an area. Such areas would most likely be located downwind of a metropolitan area, quite likely in a suburban residential area where children and other susceptible individuals are likely to be outdoors. Sites located in these areas are most likely to represent an urban scale of measurement. In this example, physical location was determined by considering ozone precursor emission patterns, public activity, and meteorological characteristics affecting ozone formation and dispersion. Thus, spatial scale of representativeness was not used in the selection process but was a result of site location. (d) In some cases, the physical location of a site is determined from joint consideration of both the basic monitoring objective and the type of monitoring site desired, or required by this appendix. For example, to determine PM 2.5 2.5 2.5 (e) In either case, classification of the monitor by its type and spatial scale of representativeness is necessary and will aid in interpretation of the monitoring data for a particular monitoring objective (e.g., public reporting, NAAQS compliance, or research support). (f) Table D-1 of this appendix illustrates the relationship between the various site types that can be used to support the three basic monitoring objectives, and the scales of representativeness that are generally most appropriate for that type of site. Table D-1 of Appendix D to Part 58—Relationship Between Site Types and Scales of Representativeness Site type Appropriate siting scales 1. Highest concentration Micro, middle, neighborhood ( sometimes 2. Population oriented Neighborhood, urban. 3. Source impact Micro, middle, neighborhood. 4. General/background & regional transport Urban, regional. 5. Welfare-related impacts Urban, regional. 2. General Monitoring Requirements (a) The National ambient air monitoring system includes several types of monitoring stations, each targeting a key data collection need and each varying in technical sophistication. (b) Research grade sites are platforms for scientific studies, either involved with health or welfare impacts, measurement methods development, or other atmospheric studies. These sites may be collaborative efforts between regulatory agencies and researchers with specific scientific objectives for each. Data from these sites might be collected with both traditional and experimental techniques, and data collection might involve specific laboratory analyses not common in routine measurement programs. The research grade sites are not required by regulation; however, they are included here due to their important role in supporting the air quality management program. (c) The NCore multipollutant sites are sites that measure multiple pollutants in order to provide support to integrated air quality management data needs. NCore sites include both neighborhood and urban scale measurements in general, in a selection of metropolitan areas and a limited number of more rural locations. Continuous monitoring methods are to be used at the NCore sites when available for a pollutant to be measured, as it is important to have data collected over common time periods for integrated analyses. NCore multipollutant sites are intended to be long-term sites useful for a variety of applications including air quality trends analyses, model evaluation, and tracking metropolitan area statistics. As such, the NCore sites should be placed away from direct emission sources that could substantially impact the ability to detect area-wide concentrations. The Administrator must approve the NCore sites. (d) Monitoring sites designated as SLAMS sites, but not as NCore sites, are intended to address specific air quality management interests, and as such, are frequently single-pollutant measurement sites. The EPA Regional Administrator must approve the SLAMS sites. (e) This appendix uses the statistical-based definitions for metropolitan areas provided by the Office of Management and Budget and the Census Bureau. These areas are referred to as metropolitan statistical areas (MSA), micropolitan statistical areas, core-based statistical areas (CBSA), and combined statistical areas (CSA). A CBSA associated with at least one urbanized area of 50,000 population or greater is termed a Metropolitan Statistical Area (MSA). A CBSA associated with at least one urbanized cluster of at least 10,000 population or greater is termed a Micropolitan Statistical Area. CSA consist of two or more adjacent CBSA. In this appendix, the term MSA is used to refer to a Metropolitan Statistical Area. By definition, both MSA and CSA have a high degree of integration; however, many such areas cross State or other political boundaries. MSA and CSA may also cross more than one air shed. The EPA recognizes that State or local agencies must consider MSA/CSA boundaries and their own political boundaries and geographical characteristics in designing their air monitoring networks. The EPA recognizes that there may be situations where the EPA Regional Administrator and the affected State or local agencies may need to augment or to divide the overall MSA/CSA monitoring responsibilities and requirements among these various agencies to achieve an effective network design. Full monitoring requirements apply separately to each affected State or local agency in the absence of an agreement between the affected agencies and the EPA Regional Administrator. 3. Design Criteria for NCore Sites (a) Each State (i.e. the fifty States, District of Columbia, Puerto Rico, and the Virgin Islands) is required to operate at least one NCore site. States may delegate this requirement to a local agency. States with many MSAs often also have multiple air sheds with unique characteristics and, often, elevated air pollution. These States include, at a minimum, California, Florida, Illinois, Michigan, New York, North Carolina, Ohio, Pennsylvania, and Texas. These States are required to identify one to two additional NCore sites in order to account for their unique situations. These additional sites shall be located to avoid proximity to large emission sources. Any State or local agency can propose additional candidate NCore sites or modifications to these requirements for approval by the Administrator. The NCore locations should be leveraged with other multipollutant air monitoring sites including PAMS sites, National Air Toxics Trends Stations (NATTS) sites, CASTNET sites, and STN sites. Site leveraging includes using the same monitoring platform and equipment to meet the objectives of the variety of programs where possible and advantageous. (b) The NCore sites must measure, at a minimum, PM 2.5 2.5 10-2.5 3 2 Y (1) Although the measurement of NO y y X y X X y (2) The EPA recognizes that, in some cases, the physical location of the NCore site may not be suitable for representative meteorological measurements due to the site's physical surroundings. It is also possible that nearby meteorological measurements may be able to fulfill this data need. In these cases, the requirement for meteorological monitoring can be waived by the Administrator. (c) [Reserved] (d) Siting criteria are provided for urban and rural locations. Sites with significant historical records that do not meet siting criteria may be approved as NCore by the Administrator. Sites with the suite of NCore measurements that are explicitly designed for other monitoring objectives are exempt from these siting criteria (e.g., a near-roadway site). (1) Urban NCore stations are to be generally located at urban or neighborhood scale to provide representative concentrations of exposure expected throughout the metropolitan area; however, a middle-scale site may be acceptable in cases where the site can represent many such locations throughout a metropolitan area. (2) Rural NCore stations are to be located to the maximum extent practicable at a regional or larger scale away from any large local emission source, so that they represent ambient concentrations over an extensive area. 4. Pollutant-Specific Design Criteria for SLAMS Sites 4.1 Ozone (O 3 3 3 3 3 3 3 3 Table D-2 of Appendix D to Part 58— SLAMS Minimum O 3 MSA population 1 2 Most recent 3-year design value concentrations ≥85% of any O 3 3 Most recent 3-year design value concentrations <85% of any O 3 3 4 >10 million 4 2 4-10 million 3 1 350,000-<4 million 2 1 50,000-<350,000 5 1 0 1 2 3 3 4 5 (b) Within an O 3 3 3 3 3 3 (c) The appropriate spatial scales for O 3 3 (1) Neighborhood scale (2) Urban scale (3) Regional scale 3 (d) EPA's technical guidance documents on O 3 3 3 (e) For locating a neighborhood scale site to measure typical city concentrations, a reasonably homogeneous geographical area near the center of the region should be selected which is also removed from the influence of major NO X X 3 3 3 3 3 (f) Once the meteorological and air quality data are reviewed, the prospective maximum concentration monitor site should be selected in a direction from the city that is most likely to observe the highest O 3 3 3 3 3 (g) In locating a neighborhood scale site which is to measure high concentrations, the same procedures used for the urban scale are followed except that the site should be located closer to the areas bordering on the center city or slightly further downwind in an area of high density population. (h) For regional scale background monitoring sites, similar meteorological analysis as for the maximum concentration sites may also inform the decisions for locating regional scale sites. Regional scale sites may be located to provide data on O 3 (i) Ozone monitoring is required at SLAMS monitoring sites only during the seasons of the year that are conducive to O 3 i.e., 3 3 3 3 3 3 Table D-3 1 State Begin Month End Month Alabama March October. Alaska April October. Arizona January December. Arkansas March November. California January December. Colorado January December. Connecticut March September. Delaware March October. District of Columbia March October. Florida January December. Georgia March October. Hawaii January December. Idaho April September. Illinois March October. Indiana March October. Iowa March October. Kansas March October. Kentucky March October. Louisiana (Northern) AQCR 019, 022 March October. Louisiana (Southern) AQCR 106 January December. Maine April September. Maryland March October. Massachusetts March September. Michigan March October. Minnesota March October. Mississippi March October. Missouri March October. Montana April September. Nebraska March October. Nevada January December. New Hampshire March September. New Jersey March October. New Mexico January December. New York March October. North Carolina March October. North Dakota March September. Ohio March October. Oklahoma March November. Oregon May September. Pennsylvania March October. Puerto Rico January December. Rhode Island March September. South Carolina March October. South Dakota March October. Tennessee March October. Texas (Northern) AQCR 022, 210, 211, 212, 215, 217, 218 March November. Texas (Southern) AQCR 106, 153, 213, 214, 216 January December. Utah January December. Vermont April September. Virginia March October. Washington May September. West Virginia March October. Wisconsin March October 15. Wyoming January September. American Samoa January December. Guam January December. Virgin Islands January December. 1 3 4.2 Carbon Monoxide (CO) Design Criteria 4.2.1 General Requirements. (a) Except as provided in subsection (b), one CO monitor is required to operate collocated with one required near-road NO 2 2 2 (b) If a state provides quantitative evidence demonstrating that peak ambient CO concentrations would occur in a near-road location which meets microscale siting criteria in Appendix E of this part but is not a near-road NO 2 2 4.2.2 Regional Administrator Required Monitoring. (a) The Regional Administrators, in collaboration with states, may require additional CO monitors above the minimum number of monitors required in 4.2.1 of this part, where the minimum monitoring requirements are not sufficient to meet monitoring objectives. The Regional Administrator may require, at his/her discretion, additional monitors in situations where data or other information suggest that CO concentrations may be approaching or exceeding the NAAQS. Such situations include, but are not limited to, (1) characterizing impacts on ground-level concentrations due to stationary CO sources, (2) characterizing CO concentrations in downtown areas or urban street canyons, and (3) characterizing CO concentrations in areas that are subject to high ground level CO concentrations particularly due to or enhanced by topographical and meteorological impacts. The Regional Administrator and the responsible State or local air monitoring agency shall work together to design and maintain the most appropriate CO network to address the data needs for an area, and include all monitors under this provision in the annual monitoring network plan. 4.2.3 CO Monitoring Spatial Scales. (a) Microscale and middle scale measurements are the most useful site classifications for CO monitoring sites since most people have the potential for exposure on these scales. Carbon monoxide maxima occur primarily in areas near major roadways and intersections with high traffic density and often in areas with poor atmospheric ventilation. (1) Microscale (2) Middle scale (3) Neighborhood scale 4.3 Nitrogen Dioxide (NO 2 4.3.1 General Requirements (a) State and, where appropriate, local agencies must operate a minimum number of required NO 2 4.3.2 Requirement for Near-road NO 2 (a) Within the NO 2 2 2 (1) The near-road NO 2 2 2 2 (b) Measurements at required near-road NO 2 2 X 4.3.3 Requirement for Area-wide NO 2 (a) Within the NO 2 2 2 2 2 2 4.3.4 Regional Administrator Required Monitoring (a) The Regional Administrators, in collaboration with States, must require a minimum of forty additional NO 2 (b) The Regional Administrators may require monitors to be sited inside or outside of CBSAs in which: (i) The required near-road monitors do not represent all locations of expected maximum hourly NO 2 2 (ii) Areas that are not required to have a monitor in accordance with the monitoring requirements and NO 2 (iii) The minimum monitoring requirements for area-wide monitors are not sufficient to meet monitoring objectives. (c) The Regional Administrator and the responsible State or local air monitoring agency should work together to design and/or maintain the most appropriate NO 2 4.3.5 NO 2 (a) The most important spatial scale for near-road NO 2 2 2 2 (1) Microscale 2 2 (2) Middle scale 2 (3) Neighborhood scale 2 2 (4) Urban scale 2 4.3.6 NO y (a) NO/NO y y 2 2 y 3 4.4 Sulfur Dioxide (SO 2 4.4.1 General Requirements. 2 4.4.2 Requirement for Monitoring by the Population Weighted Emissions Index. 2 2 2 2 2 (1) The SO 2 2 4.4.3 Regional Administrator Required Monitoring. 2 2 4.4.4 SO 2 Monitoring Spatial Scales. 2 2 2 (1) Microscale 2 (2) Middle scale 2 (3) Neighborhood scale 2 2 (4) Urban scale 2 4.4.5 NCore Monitoring. 2 2 2 2 2 2 4.5 Lead (Pb) Design Criteria. http://www.epa.gov/ttn/chief/eiinformation.html (i) One monitor may be used to meet the requirement in paragraph 4.5(a) for all sources involved when the location of the maximum Pb concentration due to one Pb source is expected to also be impacted by Pb emissions from a nearby source (or multiple sources). This monitor must be sited, taking into account logistics and the potential for population exposure, where the Pb concentration from all sources combined is expected to be at its maximum. (ii) The Regional Administrator may waive the requirement in paragraph 4.5(a) for monitoring near Pb sources if the State or, where appropriate, local agency can demonstrate the Pb source will not contribute to a maximum Pb concentration in ambient air in excess of 50 percent of the NAAQS (based on historical monitoring data, modeling, or other means). The waiver must be renewed once every 5 years as part of the network assessment required under § 58.10(d). (iii) State and, where appropriate, local agencies are required to conduct ambient air Pb monitoring near each of the airports listed in Table D-3A for a period of 12 consecutive months commencing no later than December 27, 2011. Monitors shall be sited to measure the maximum Pb concentration in ambient air, taking into account logistics and the potential for population exposure, and shall use an approved Pb-TSP Federal Reference Method or Federal Equivalent Method. Any monitor that exceeds 50 percent of the Pb NAAQS on a rolling 3-month average (as determined according to 40 CFR part 50, Appendix R) shall become a required monitor under paragraph 4.5(c) of this Appendix, and shall continue to monitor for Pb unless a waiver is granted allowing it to stop operating as allowed by the provisions in paragraph 4.5(a)(ii) of this appendix. Data collected shall be submitted to the Air Quality System database according to the requirements of 40 CFR part 58.16. Table D-3A Airports To Be Monitored for Lead Airport County State Merrill Field Anchorage AK Pryor Field Regional Limestone AL Palo Alto Airport of Santa Clara County Santa Clara CA McClellan-Palomar San Diego CA Reid-Hillview Santa Clara CA Gillespie Field San Diego CA San Carlos San Mateo CA Nantucket Memorial Nantucket MA Oakland County International Oakland MI Republic Suffolk NY Brookhaven Suffolk NY Stinson Municipal Bexar TX Northwest Regional Denton TX Harvey Field Snohomish WA Auburn Municipal King WA (b) [Reserved] (c) The EPA Regional Administrator may require additional monitoring beyond the minimum monitoring requirements contained in paragraph 4.5(a) of this appendix where the likelihood of Pb air quality violations is significant or where the emissions density, topography, or population locations are complex and varied. The EPA Regional Administrators may require additional monitoring at locations including, but not limited to, those near existing additional industrial sources of Pb, recently closed industrial sources of Pb, airports where piston-engine aircraft emit Pb, and other sources of re-entrained Pb dust. (d) The most important spatial scales for source-oriented sites to effectively characterize the emissions from point sources are microscale and middle scale. The most important spatial scale for non-source-oriented sites to characterize typical lead concentrations in urban areas is the neighborhood scale. Monitor siting should be conducted in accordance with 4.5(a)(i) with respect to source-oriented sites. (1) Microscale—This scale would typify areas in close proximity to lead point sources. Emissions from point sources such as primary and secondary lead smelters, and primary copper smelters may under fumigation conditions likewise result in high ground level concentrations at the microscale. In the latter case, the microscale would represent an area impacted by the plume with dimensions extending up to approximately 100 meters. Pb monitors in areas where the public has access, and particularly children have access, are desirable because of the higher sensitivity of children to exposures of elevated Pb concentrations. (2) Middle scale—This scale generally represents Pb air quality levels in areas up to several city blocks in size with dimensions on the order of approximately 100 meters to 500 meters. The middle scale may for example, include schools and playgrounds in center city areas which are close to major Pb point sources. Pb monitors in such areas are desirable because of the higher sensitivity of children to exposures of elevated Pb concentrations (reference 3 of this appendix). Emissions from point sources frequently impact on areas at which single sites may be located to measure concentrations representing middle spatial scales. (3) Neighborhood scale—The neighborhood scale would characterize air quality conditions throughout some relatively uniform land use areas with dimensions in the 0.5 to 4.0 kilometer range. Sites of this scale would provide monitoring data in areas representing conditions where children live and play. Monitoring in such areas is important since this segment of the population is more susceptible to the effects of Pb. Where a neighborhood site is located away from immediate Pb sources, the site may be very useful in representing typical air quality values for a larger residential area, and therefore suitable for population exposure and trends analyses. (d) Technical guidance is found in references 4 and 5 of this appendix. These documents provide additional guidance on locating sites to meet specific urban area monitoring objectives and should be used in locating new sites or evaluating the adequacy of existing sites. 4.6 Particulate Matter (PM 10 10 10 10 Table D-4 of Appendix D to Part 58—PM 10 1 Population category High concentration 2 Medium concentration 3 Low concentration 4 5 >1,000,000 6-10 4-8 2-4 500,000-1,000,000 4-8 2-4 1-2 250,000-500,000 3-4 1-2 0-1 100,000-250,000 1-2 0-1 0 1 2 10 3 10 4 10 5 (b) Although microscale monitoring may be appropriate in some circumstances, the most important spatial scales to effectively characterize the emissions of PM 10 (1) Microscale 10 (2) Middle scale 10 10 10 (3) Neighborhood scale 10 4.7 Fine Particulate Matter (PM 2.5 4.7.1 General Requirements. (a) State and where applicable, local, agencies must operate the minimum number of required PM 2.5 2.5 2.5 2.5 2.5 Table D-5 of Appendix D to Part 58—PM 2.5 MSA population 1 2 Most recent 3-year design value ≥85% of any PM 2.5 3 Most recent 3-year design value <85% of any PM 2.5 3 4 >1,000,000 3 2 500,000-1,000,000 2 1 50,000-<500,000 5 1 0 1 2 3 2.5 4 5 (b) Specific Design Criteria for PM 2.5 2.5 (1) At least one monitoring station is to be sited at neighborhood or larger scale in an area of expected maximum concentration. (2) For CBSAs with a population of 1,000,000 or more persons, at least one PM 2.5 2 (3) For areas with additional required SLAMS, a monitoring station is to be sited in an at-risk community with poor air quality, particularly where there are anticipated effects from sources in the area ( e.g., (4) Additional technical guidance for siting PM 2.5 (c) The most important spatial scale to effectively characterize the emissions of particulate matter from both mobile and stationary sources is the neighborhood scale for PM 2.5 2.5 (1) Micro-scale. (2) Middle scale (3) Neighborhood scale 2.5 2.5 2.5 (4) Urban scale 2.5 (5) Regional scale 2.5 2.5 3 4.7.2 Requirement for Continuous PM 2.5 2.5 4.7.3 Requirement for PM 2.5 2.5 2.5 2.5 4.7.4 PM 2.5 2.5 2.5 4.8 Coarse Particulate Matter (PM 10-2.5 4.8.1 General Monitoring Requirements. (a) The only required monitors for PM 10-2.5 (b) Although microscale monitoring may be appropriate in some circumstances, middle and neighborhood scale measurements are the most important station classifications for PM 10-2.5 (1) Microscale (2) Middle scale (3) Neighborhood scale 10-2.5 4.8.2 [Reserved] 5. Network Design for Photochemical Assessment Monitoring Stations (PAMS) and Enhanced Ozone Monitoring (a) State and local monitoring agencies are required to collect and report PAMS measurements at each Ncore site required under paragraph 3(a) of this appendix located in a CBSA with a population of 1,000,000 or more, based on the latest available census figures. (b) PAMS measurements include: (1) Hourly averaged speciated volatile organic compounds (VOCs); (2) Three 8-hour averaged carbonyl samples per day on a 1 in 3 day schedule, or hourly averaged formaldehyde; (3) Hourly averaged O 3 (4) Hourly averaged nitrogen oxide (NO), true nitrogen dioxide (NO 2 y (5) Hourly averaged ambient temperature; (6) Hourly vector-averaged wind direction; (7) Hourly vector-averaged wind speed; (8) Hourly average atmospheric pressure; (9) Hourly averaged relative humidity; (10) Hourly precipitation; (11) Hourly averaged mixing-height; (12) Hourly averaged solar radiation; and (13) Hourly averaged ultraviolet radiation. (c) The EPA Regional Administrator may grant a waiver to allow the collection of required PAMS measurements at an alternative location where the monitoring agency can demonstrate that the alternative location will provide representative data useful for regional or national scale modeling and the tracking of trends in O 3 (d) The EPA Regional Administrator may grant a waiver to allow speciated VOC measurements to be made as three 8-hour averages on every third day during the PAMS season as an alternative to 1-hour average speciated VOC measurements in cases where the primary VOC compounds are not well measured using continuous technology due to low detectability of the primary VOC compounds or for logistical and other programmatic constraints. (e) The EPA Regional Administrator may grant a waiver to allow representative meteorological data from nearby monitoring stations to be used to meet the meteorological requirements in paragraph 5(b) where the monitoring agency can demonstrate the data is collected in a manner consistent with EPA quality assurance requirements for these measurements. (f) The EPA Regional Administrator may grant a waiver from the requirement to collect PAMS measurements in locations where CBSA-wide O 3 3 3 (g) At a minimum, the monitoring agency shall collect the required PAMS measurements during the months of June, July, and August. (h) States with Moderate and above 8-hour O 3 3 3 3 3 (1) Additional O 3 (2) Additional NO X y (3) Additional speciated VOC measurements including data gathered during different periods other than required under paragraph 5(g) of this appendix, or locations other than those required under paragraph 5(a) of this appendix, and (4) Enhanced upper air measurements of meteorology or pollution concentrations. 6. References 1. Ball, R.J. and G.E. Anderson. Optimum Site Exposure Criteria for SO 2 2. Ludwig, F.F., J.H.S. Kealoha, and E. Shelar. Selecting Sites for Carbon Monoxide Monitoring. Stanford Research Institute, Menlo Park, CA. Prepared for U.S. Environmental Protection Agency, Research Triangle Park, NC. EPA Publication No. EPA-450/3-75-077, September 1975. 3. Air Quality Criteria for Lead. Office of Research and Development, U.S. Environmental Protection Agency, Washington D.C. EPA Publication No. 600/8-89-049F. August 1990. (NTIS document numbers PB87-142378 and PB91-138420.) 4. Optimum Site Exposure Criteria for Lead Monitoring. PEDCo Environmental, Inc. Cincinnati, OH. Prepared for U.S. Environmental Protection Agency, Research Triangle Park, NC. EPA Contract No. 68-02-3013. May 1981. 5. Guidance for Conducting Ambient Air Monitoring for Lead Around Point Sources. Office of Air Quality Planning and Standards, U.S. Environmental Protection Agency, Research Triangle Park, NC. EPA-454/R-92-009. May 1997. 6. Koch, R.C. and H.E. Rector. Optimum Network Design and Site Exposure Criteria for Particulate Matter. GEOMET Technologies, Inc., Rockville, MD. Prepared for U.S. Environmental Protection Agency, Research Triangle Park, NC. EPA Contract No. 68-02-3584. EPA 450/4-87-009. May 1987. 7. Watson et al. 2.5 10 8. Guideline for Selecting and Modifying the Ozone Monitoring Season Based on an 8-Hour Ozone Standard. Prepared for U.S. Environmental Protection Agency, RTP, NC. EPA-454/R-98-001, June 1998. 9. Photochemical Assessment Monitoring Stations Implementation Manual. Office of Air Quality Planning and Standards, U.S. Environmental Protection Agency, Research Triangle Park, NC. EPA-454/B-93-051. March 1994. [71 FR 61316, Oct. 17, 2006, as amended at 72 FR 32211, June 12, 2007; 73 FR 67062, Nov. 12, 2008; 75 FR 6534, Feb. 9, 2010; 75 FR 35602, June 22, 2010; 75 FR 81137, Dec. 27, 2010; 76 FR 54342, Aug. 31, 2011; 78 FR 3284, Jan. 15, 2013; 80 FR 65466, Oct. 26, 2015; 81 FR 17298, Mar. 28, 2016; 81 FR 96388, Dec. 30, 2016; 89 FR 16396, Mar. 6, 2024] Appendix E to Part 58—Probe and Monitoring Path Siting Criteria for Ambient Air Quality Monitoring 1. Introduction 2. Monitors and Samplers with Probe Inlets 3. Open Path Analyzers 4. Waiver Provisions 5. References 1. Introduction 1.1 Applicability (a) This appendix contains specific location criteria applicable to ambient air quality monitoring probes, inlets, and optical paths of SLAMS, NCore, PAMS, and other monitor types whose data are intended to be used to determine compliance with the NAAQS. These specific location criteria are relevant after the general location has been selected based on the monitoring objectives and spatial scale of representation discussed in appendix D to this part. Monitor probe material and sample residence time requirements are also included in this appendix. Adherence to these siting criteria is necessary to ensure the uniform collection of compatible and comparable air quality data. (b) The probe and monitoring path siting criteria discussed in this appendix must be followed to the maximum extent possible. It is recognized that there may be situations where some deviation from the siting criteria may be necessary. In any such case, the reasons must be thoroughly documented in a written request for a waiver that describes whether the resulting monitoring data will be representative of the monitoring area and how and why the proposed or existing siting must deviate from the criteria. This documentation should help to avoid later questions about the validity of the resulting monitoring data. Conditions under which the EPA would consider an application for waiver from these siting criteria are discussed in section 4 of this appendix. (c) The pollutant-specific probe and monitoring path siting criteria generally apply to all spatial scales except where noted otherwise. Specific siting criteria that are phrased with “shall” or “must” are defined as requirements and exceptions must be granted through the waiver provisions. However, siting criteria that are phrased with “should” are defined as goals to meet for consistency but are not requirements. 2. Monitors and Samplers with Probe Inlets 2.1 Horizontal and Vertical Placement (a) For O 3 2 10 10-2.5 2.5 2 (b) Middle scale CO and NO 2 (c) Middle scale PM 10-2.5 (d) Microscale Pb, PM 10 10-2.5 2.5 (e) Microscale near-road NO 2 (f) The probe inlets for microscale carbon monoxide monitors that are being used to measure concentrations near roadways must be greater than or equal to 2.0 meters and less than or equal to 7.0 meters above ground level. Those probe inlets for microscale carbon monoxide monitors measuring concentrations near roadways in downtown areas or urban street canyons must be greater than or equal to 2.5 meters and less than or equal to 3.5 meters above ground level. The probe must be at least 1.0 meter vertically or horizontally away from any supporting structure, walls, parapets, penthouses, etc ., 2.2 Spacing From Minor Sources (a) It is important to understand the monitoring objective for a particular site in order to interpret this requirement. Local minor sources of a primary pollutant, such as SO 2 (b) Similarly, local sources of nitric oxide (NO) and ozone-reactive hydrocarbons can have a scavenging effect causing unrepresentatively low concentrations of O 3 3 2 2.3 Spacing From Obstructions (a) Obstacles may scavenge SO 2 3 2 (b) A probe inlet located near or along a vertical wall is undesirable because air moving along the wall may be subject to removal mechanisms. A probe inlet must have unrestricted airflow with no obstructions (as defined in paragraph (a) of this section) in a continuous arc of at least 270 degrees. An unobstructed continuous arc of 180 degrees is allowable when the applicable network design criteria specified in appendix D of this part require monitoring in street canyons and the probe is located on the side of a building. This arc must include the predominant wind direction for the season of greatest pollutant concentration potential. For particle sampling, there must be a minimum of 2.0 meters of horizontal separation from walls, parapets, and structures for rooftop site placement. (c) A sampling station with a probe inlet located closer to an obstacle than required by the criteria in this section should be classified as middle scale or microscale, rather than neighborhood or urban scale, since the measurements from such a station would more closely represent these smaller scales. (d) For near-road monitoring stations, the monitor probe shall have an unobstructed air flow, where no obstacles exist at or above the height of the monitor probe, between the monitor probe and the outside nearest edge of the traffic lanes of the target road segment. 2.4 Spacing From Trees (a) Trees can provide surfaces for SO 2 3 2 (b) The scavenging effect of trees is greater for O 3 (c) Beginning January 1, 2024, microscale sites of any air pollutant shall have no trees or shrubs located at or above the line-of-sight fetch between the probe and the source under investigation, e.g., 2.5 Spacing From Roadways Table E-1 to Section 2.5 of Appendix E—Minimum Separation Distance Between Roadways and Probes for Monitoring Neighborhood and Urban Scale Ozone (O 3 2 X y Roadway Minimum 1 3 Minimum 1 2 3 ≤1,000 10 10 10,000 10 20 15,000 20 30 20,000 30 40 40,000 50 60 70,000 100 100 ≥110,000 250 250 1 2 3 2.5.1 Spacing for Ozone Probes In siting an O 3 3 2.5.2 Spacing for Carbon Monoxide Probes (a) Near-road microscale CO monitoring sites, including those located in downtown areas, urban street canyons, and other near-road locations such as those adjacent to highly trafficked roads, are intended to provide a measurement of the influence of the immediate source on the pollution exposure on the adjacent area. (b) Microscale CO monitor probe inlets in downtown areas or urban street canyon locations shall be located a minimum distance of 2.0 meters and a maximum distance of 10 meters from the edge of the nearest traffic lane. (c) Microscale CO monitor probe inlets in downtown areas or urban street canyon locations shall be located at least 10 meters from an intersection, preferably at a midblock location. Midblock locations are preferable to intersection locations because intersections represent a much smaller portion of downtown space than do the streets between them. Pedestrian exposure is probably also greater in street canyon/corridors than at intersections. (d) Neighborhood scale CO monitor probe inlets in downtown areas or urban street canyon locations shall be located according to the requirements in Table E-2 of this appendix. Table E-2 to Section 2.5.2 of Appendix E—Minimum Separation Distance Between Roadways and Probes for Monitoring Neighborhood Scale Carbon Monoxide Roadway average Minimum distance 1 2 ≤10,000 10 15,000 25 20,000 45 30,000 80 40,000 115 50,000 135 ≥60,000 150 1 2 2.5.3 Spacing for Particulate Matter (PM 2.5 2.5-10 10 (a) Since emissions associated with the operation of motor vehicles contribute to urban area particulate matter ambient levels, spacing from roadway criteria are necessary for ensuring national consistency in PM sampler siting. (b) The intent is to locate localized hot-spot sites in areas of highest concentrations, whether it be caused by mobile or multiple stationary sources. If the area is primarily affected by mobile sources and the maximum concentration area(s) is judged to be a traffic corridor or street canyon location, then the monitors should be located near roadways with the highest traffic volume and at separation distances most likely to produce the highest concentrations. For microscale traffic corridor sites, the location must be greater than or equal 5.0 meters and less than or equal to 15 meters from the major roadway. For the microscale street canyon site, the location must be greater than or equal 2.0 meters and less than or equal to 10 meters from the roadway. For the middle scale site, a range of acceptable distances from the roadway is shown in Figure E-1 of this appendix. This figure also includes separation distances between a roadway and neighborhood or larger scale sites by default. Any PM probe inlet at a site, 2.0 to 15 meters high, and further back than the middle scale requirements will generally be neighborhood, urban or regional scale. For example, according to Figure E-1 of this appendix, if a PM sampler is primarily influenced by roadway emissions and that sampler is set back 10 meters from a 30,000 ADT (average daily traffic) road, the site should be classified as microscale, if the sampler's inlet height is between 2.0 and 7.0 meters. If the sampler's inlet height is between 7.0 and 15 meters, the site should be classified as middle scale. If the sampler is 20 meters from the same road, it will be classified as middle scale; if 40 meters, neighborhood scale; and if 110 meters, an urban scale. 2.5.4 Spacing for Nitrogen Dioxide (NO 2 (a) In siting near-road NO 2 2 (b) In siting NO 2 2.6 Probe Material and Pollutant Sampler Residence Time (a) For the reactive gases (SO 2 2 3 25 34 25 TM 35 (b) For volatile organic compound (VOC) monitoring at PAMS, FEP Teflon® is unacceptable as the probe material because of VOC adsorption and desorption reactions on the FEP Teflon®. Borosilicate glass, stainless steel, or their equivalents are the acceptable probe materials for VOC and carbonyl sampling. Care must be taken to ensure that the sample residence time is kept to 20 seconds or less. (c) No matter how nonreactive the sampling probe material is initially, after a period of use, reactive particulate matter is deposited on the probe walls. Therefore, the time it takes the gas to transfer from the probe inlet to the sampling device is critical. Ozone in the presence of nitrogen oxide (NO) will show significant losses, even in the most inert probe material, when the residence time exceeds 20 seconds. 26 27 28 2 2 3 2.7 Summary Table E-3 of this appendix presents a summary of the general requirements for probe siting criteria with respect to distances and heights. Table E-3 requires different elevation distances above the ground for the various pollutants. The discussion in this appendix for each of the pollutants describes reasons for elevating the monitor or probe inlet. The differences in the specified range of heights are based on the vertical concentration gradients. For source oriented and near-road monitors, the gradients in the vertical direction are very large for the microscale, so a small range of heights are used. The upper limit of 15 meters is specified for the consistency between pollutants and to allow the use of a single manifold for monitoring more than one pollutant. Table E-3 to Section 2.7 of Appendix E—Summary of Probe Siting Criteria Pollutant Scale 9 Height from ground to probe 8 Horizontal or vertical distance from supporting structures 1 8 Distance from drip line of trees to probe 8 Distance from roadways to probe 8 SO 2 2 3 4 5 Middle, Neighborhood, Urban, and Regional 2.0-15 ≥1.0 ≥10 N/A. CO 3 4 6 Micro [downtown or street canyon sites] 2.5-3.5 ≥1.0 ≥10 2.0-10 for downtown areas or street canyon microscale. CO 3 4 6 Micro [Near-Road sites] 2.0-7.0 ≥1.0 ≥10 ≤50 for near-road microscale. CO 3 4 6 Middle and Neighborhood 2.0-15 ≥1.0 ≥10 See O 3 2 3 4 Middle, Neighborhood, Urban, and Regional 2.0-15 ≥1.0 ≥10 See NO 2 2 3 4 Micro 2.0-7.0 ≥1.0 ≥10 ≤50 for near-road micro-scale. NO 2 2 3 4 Middle, Neighborhood, Urban, and Regional 2.0-15 ≥1.0 ≥10 See PAMS 2 3 4 Neighborhood and Urban 2.0-15 ≥1.0 ≥10 See PM, Pb 2 3 4 7 Micro 2.0-7.0 ≥2.0 (horizontal ≥10 See PM, Pb 2 3 4 7 Middle, Neighborhood, Urban and Regional 2.0-15 ≥2.0 (horizontal ≥10 See N/A—Not applicable. 1 2 3 see 4 5 6 7 2.5 8 9 3. Open Path Analyzers 3.1 Horizontal and Vertical Placement (a) For all O 3 2 2 (b) Middle scale CO and NO 2 (c) Microscale near-road monitoring sites are required to have monitoring paths greater than or equal 2.0 meters and less than or equal to 7.0 meters above ground level. (d) For microscale carbon monoxide monitors that are being used to measure concentrations near roadways, the monitoring path must be greater than or equal 2.0 meters and less than or equal to 7.0 meters above ground level. If the microscale carbon monoxide monitors measuring concentrations near roadways are in downtown areas or urban street canyons, the monitoring path must be greater than or equal 2.5 meters and less than or equal to 3.5 meters above ground level and at least 90 percent of the monitoring path must be at least 1.0 meter vertically or horizontally away from any supporting structure, walls, parapets, penthouses, etc., and away from dusty or dirty areas. If a significant portion of the monitoring path is located near the side of a building or wall, then it should be located on the windward side of the building relative to the prevailing wind direction during the season of highest concentration potential for the pollutant being measured. 3.2 Spacing From Minor Sources (a) It is important to understand the monitoring objective for a particular site in order to interpret this requirement. Local minor sources of a primary pollutant, such as SO 2 (b) Similarly, local sources of nitric oxide (NO) and ozone-reactive hydrocarbons can have a scavenging effect causing unrepresentatively low concentrations of O 3 3 2 3.3 Spacing From Obstructions (a) Obstacles may scavenge SO 2 3 2 (b) A monitoring path located near or along a vertical wall is undesirable because air moving along the wall may be subject to removal mechanisms. At least 90 percent of the monitoring path for open path analyzers must have unrestricted airflow with no obstructions (as defined in paragraph (a) of this section) in a continuous arc of at least 270 degrees. An unobstructed continuous arc of 180 degrees is allowable when the applicable network design criteria specified in appendix D of this part require monitoring in street canyons and the monitoring path is located on the side of a building. This arc must include the predominant wind direction for the season of greatest pollutant concentration potential. (c) Special consideration must be given to the use of open path analyzers given their inherent potential sensitivity to certain types of interferences and optical obstructions. A monitoring path must be clear of all trees, brush, buildings, plumes, dust, or other optical obstructions, including potential obstructions that may move due to wind, human activity, growth of vegetation, etc. Temporary optical obstructions, such as rain, particles, fog, or snow, should be considered when siting an open path analyzer. Any of these temporary obstructions that are of sufficient density to obscure the light beam will negatively affect the ability of the open path analyzer to continuously measure pollutant concentrations. Transient, but significant obscuration of especially longer measurement paths, could occur as a result of certain meteorological conditions ( e.g., e.g., (d) A sampling station with a monitoring path located closer to an obstacle than required by the criteria in this section should be classified as middle scale or microscale, rather than neighborhood or urban scale, since the measurements from such a station would more closely represent these smaller scales. (e) For near-road monitoring stations, the monitoring path shall have an unobstructed air flow, where no obstacles exist at or above the height of the monitoring path, between the monitoring path and the outside nearest edge of the traffic lanes of the target road segment. 3.4 Spacing From Trees (a) Trees can provide surfaces for SO 2 3 2 (b) The scavenging effect of trees is greater for O 3 (c) Beginning January 1, 2024, microscale sites of any air pollutant shall have no trees or shrubs located at or above the line-of-sight fetch between the monitoring path and the source under investigation, e.g., 3.5 Spacing from Roadways Table E-4 of Section 3.5 of Appendix E—Minimum Separation Distance Between Roadways and Monitoring Paths for Monitoring Neighborhood and Urban Scale Ozone (O 3 2 x y Roadway Minimum 1 3 Minimum 1 2 3 ≤1,000 10 10 10,000 10 20 15,000 20 30 20,000 30 40 40,000 50 60 70,000 100 100 ≥110,000 250 250 1 2 3 3.5.1 Spacing for Ozone Monitoring Paths In siting an O 3 3 3.5.2 Spacing for Carbon Monoxide Monitoring Paths (a) Near-road microscale CO monitoring sites, including those located in downtown areas, urban street canyons, and other near-road locations such as those adjacent to highly trafficked roads, are intended to provide a measurement of the influence of the immediate source on the pollution exposure on the adjacent area. (b) Microscale CO monitoring paths in downtown areas or urban street canyon locations shall be located a minimum distance of 2.0 meters and a maximum distance of 10 meters from the edge of the nearest traffic lane. (c) Microscale CO monitoring paths in downtown areas or urban street canyon locations shall be located at least 10 meters from an intersection, preferably at a midblock location. Midblock locations are preferable to intersection locations because intersections represent a much smaller portion of downtown space than do the streets between them. Pedestrian exposure is probably also greater in street canyon/corridors than at intersections. (d) Neighborhood scale CO monitoring paths in downtown areas or urban street canyon locations shall be located according to the requirements in Table E-5 of this appendix. Table E-5 Section 3.5.2 of Appendix E—Minimum Separation Distance Between Roadways and Monitoring Paths for Monitoring Neighborhood Scale Carbon Monoxide Roadway average Minimum 1 2 ≤10,000 10 15,000 25 20,000 45 30,000 80 40,000 115 50,000 135 ≥60,000 150 1 2 3.5.3 Spacing for Nitrogen Dioxide (NO 2 (a) In siting near-road NO 2 (b) In siting NO 2 3.6 Cumulative Interferences on a Monitoring Path The cumulative length or portion of a monitoring path that is affected by minor sources, trees, or roadways must not exceed 10 percent of the total monitoring path length. 3.7 Maximum Monitoring Path Length The monitoring path length must not exceed 1.0 kilometer for open path analyzers in neighborhood, urban, or regional scale. For middle scale monitoring sites, the monitoring path length must not exceed 300 meters. In areas subject to frequent periods of dust, fog, rain, or snow, consideration should be given to a shortened monitoring path length to minimize loss of monitoring data due to these temporary optical obstructions. For certain ambient air monitoring scenarios using open path analyzers, shorter path lengths may be needed in order to ensure that the monitoring site meets the objectives and spatial scales defined in appendix D to this part. The Regional Administrator may require shorter path lengths, as needed on an individual basis, to ensure that the SLAMS sites meet the appendix D requirements. Likewise, the Administrator may specify the maximum path length used at NCore monitoring sites. 3.8 Summary Table E-6 of this appendix presents a summary of the general requirements for monitoring path siting criteria with respect to distances and heights. Table E-6 requires different elevation distances above the ground for the various pollutants. The discussion in this appendix for each of the pollutants describes reasons for elevating the monitoring path. The differences in the specified range of heights are based on the vertical concentration gradients. For source oriented and near-road monitors, the gradients in the vertical direction are very large for the microscale, so a small range of heights are used. The upper limit of 15 meters is specified for the consistency between pollutants and to allow the use of a monitoring path for monitoring more than one pollutant. Table E-6 to Section 3.8 of Appendix E—Summary of Monitoring Path Siting Criteria Pollutant Maximum monitoring path length 9 10 Height from ground to 80% of monitoring path 1 8 Horizontal or vertical distance 2 1 8 Distance from trees to 90% of monitoring path 1 8 Distance from roadways to monitoring path 1 8 SO 2 3 4 5 6 <= 300 m for Middle 2.0-15 ≥1.0 ≥10 N/A. CO 4 5 7 <= 300 m for Micro [downtown or street canyon sites] 2.5-3.5 ≥1.0 ≥10 2.0-10 for downtown areas or street canyon microscale. CO 4 5 7 <= 300 m for Micro [Near-Road sites] 2.0-7.0 ≥1.0 ≥10 ≤50 for near-road microscale. CO 4 5 7 <= 300 m for Middle 2.0-15 ≥1.0 ≥10 See CO 4 5 7 <= 1.0 km for Neighborhood 2.0-15 ≥1.0 ≥10 See O 3 3 4 5 <= 300 m for Middle 2.0-15 ≥1.0 ≥10 See O 3 3 4 5 <= 1.0 km for Neighborhood, Urban, and Regional 2.0-15 ≥1.0 ≥10 See NO 2 3 4 5 Between 50 m-300 m for Micro (Near-Road) 2.0-7.0 ≥1.0 ≥10 ≤50 for near-road micro-scale. NO 2 3 4 5 <= 300 m for Middle 2.0-15 ≥1.0 ≥10 See NO 2 3 4 5 <= 1.0 km for Neighborhood, Urban, and Regional 2.0-15 ≥1.0 ≥10 See PAMS 3 4 5 <= 1.0 km for Neighborhood and Urban 2.0-15 ≥1.0 ≥10 See N/A—Not applicable. 1 2 2 3 3 2 3 4 see 5 6 7 8 9 10 4. Waiver Provisions Most sampling probes or monitors can be located so that they meet the requirements of this appendix. New sites, with rare exceptions, can be located within the limits of this appendix. However, some existing sites may not meet these requirements and may still produce useful data for some purposes. The EPA will consider a written request from the State, or where applicable local, agency to waive one or more siting criteria for some monitoring sites providing that the State or their designee can adequately demonstrate the need (purpose) for monitoring or establishing a monitoring site at that location. 4.1 For a proposed new site, a waiver may be granted only if both the following criteria are met: 4.1.1 The proposed new site can be demonstrated to be as representative of the monitoring area as it would be if the siting criteria were being met. 4.1.2 The monitor or probe cannot reasonably be located so as to meet the siting criteria because of physical constraints ( e.g., 4.2 For an existing site, a waiver may be granted if either the criterion in section 4.1.1 or the criterion in 4.1.2 of this appendix is met. 4.3 Cost benefits, historical trends, and other factors may be used to add support to the criteria in sections 4.1.1 and 4.1.2 of this appendix; however, by themselves, they will not be acceptable reasons for the EPA to grant a waiver. Written requests for waivers must be submitted to the Regional Administrator. Granted waivers must be renewed minimally every 5 years and ideally as part of the network assessment as defined in § 58.10(d). The approval date of the waiver must be documented in the annual monitoring network plan to support the requirements of § 58.10(a)(1) and 58.10(b)(10). 5. References 1. Bryan, R.J., R.J. Gordon, and H. Menck. Comparison of High Volume Air Filter Samples at Varying Distances from Los Angeles Freeway. University of Southern California, School of Medicine, Los Angeles, CA. (Presented at 66th Annual Meeting of Air Pollution Control Association. Chicago, IL. June 24-28, 1973. APCA 73-158.) 2. Teer, E.H. Atmospheric Lead Concentration Above an Urban Street. Master of Science Thesis, Washington University, St. Louis, MO. January 1971. 3. Bradway, R.M., F.A. Record, and W.E. Belanger. Monitoring and Modeling of Resuspended Roadway Dust Near Urban Arterials. GCA Technology Division, Bedford, MA. (Presented at 1978 Annual Meeting of Transportation Research Board, Washington, DC. January 1978.) 4. Pace, T.G., W.P. Freas, and E.M. Afify. Quantification of Relationship Between Monitor Height and Measured Particulate Levels in Seven U.S. Urban Areas. U.S. Environmental Protection Agency, Research Triangle Park, NC. (Presented at 70th Annual Meeting of Air Pollution Control Association, Toronto, Canada. June 20-24, 1977. APCA 77-13.4.) 5. Harrison, P.R. Considerations for Siting Air Quality Monitors in Urban Areas. City of Chicago, Department of Environmental Control, Chicago, IL. (Presented at 66th Annual Meeting of Air Pollution Control Association, Chicago, IL. June 24-28, 1973. APCA 73-161.) 6. Study of Suspended Particulate Measurements at Varying Heights Above Ground. Texas State Department of Health, Air Control Section, Austin, TX. 1970. p.7. 7. Rodes, C.E. and G.F. Evans. Summary of LACS Integrated Pollutant Data. In: Los Angeles Catalyst Study Symposium. U.S. Environmental Protection Agency, Research Triangle Park, NC. EPA Publication No. EPA-600/4-77-034. June 1977. 8. Lynn, D.A. et al. 9. Pace, T.G. Impact of Vehicle-Related Particulates on TSP Concentrations and Rationale for Siting Hi-Vols in the Vicinity of Roadways. OAQPS, U.S. Environmental Protection Agency, Research Triangle Park, NC. April 1978. 10. Ludwig, F.L., J.H. Kealoha, and E. Shelar. Selecting Sites for Monitoring Total Suspended Particulates. Stanford Research Institute, Menlo Park, CA. Prepared for U.S. Environmental Protection Agency, Research Triangle Park, NC. EPA Publication No. EPA-450/3-77-018. June 1977, revised December 1977. 11. Ball, R.J. and G.E. Anderson. Optimum Site Exposure Criteria for SO 2 12. Ludwig, F.L. and J.H.S. Kealoha. Selecting Sites for Carbon Monoxide Monitoring. Stanford Research Institute, Menlo Park, CA. Prepared for U.S. Environmental Protection Agency, Research Triangle Park, NC. EPA Publication No. EPA-450/3-75-077. September 1975. 13. Ludwig, F.L. and E. Shelar. Site Selection for the Monitoring of Photochemical Air Pollutants. Stanford Research Institute, Menlo Park, CA. Prepared for U.S. Environmental Protection Agency, Research Triangle Park, NC. EPA Publication No. EPA-450/3-78-013. April 1978. 14. Lead Analysis for Kansas City and Cincinnati, PEDCo Environmental, Inc., Cincinnati, OH. Prepared for U.S. Environmental Protection Agency, Research Triangle Park, NC. EPA Contract No. 66-02-2515, June 1977. 15. Barltrap, D. and C.D. Strelow. Westway Nursery Testing Project. Report to the Greater London Council. August 1976. 16. Daines, R. H., H. Moto, and D. M. Chilko. Atmospheric Lead: Its Relationship to Traffic Volume and Proximity to Highways. Environ. Sci. and Technol., 4:318, 1970. 17. Johnson, D. E., et al. 18. Air Quality Criteria for Lead. Office of Research and Development, U.S. Environmental Protection Agency, Washington, DC EPA-600/8-83-028 aF-dF, 1986, and supplements EPA-600/8-89/049F, August 1990. (NTIS document numbers PB87-142378 and PB91-138420.) 19. Lyman, D. R. The Atmospheric Diffusion of Carbon Monoxide and Lead from an Expressway, Ph.D. Dissertation, University of Cincinnati, Cincinnati, OH. 1972. 20. Wechter, S.G. Preparation of Stable Pollutant Gas Standards Using Treated Aluminum Cylinders. ASTM STP. 598:40-54, 1976. 21. Wohlers, H.C., H. Newstein and D. Daunis. Carbon Monoxide and Sulfur Dioxide Adsorption On and Description From Glass, Plastic and Metal Tubings. J. Air Poll. Con. Assoc. 17:753, 1976. 22. Elfers, L.A. Field Operating Guide for Automated Air Monitoring Equipment. U.S. NTIS. p. 202, 249, 1971. 23. Hughes, E.E. Development of Standard Reference Material for Air Quality Measurement. ISA Transactions, 14:281-291, 1975. 24. Altshuller, A.D. and A.G. Wartburg. The Interaction of Ozone with Plastic and Metallic Materials in a Dynamic Flow System. Intern. Jour. Air and Water Poll., 4:70-78, 1961. 25. Code of Federal Regulations. 40 CFR 53.22, July 1976. 26. Butcher, S.S. and R.E. Ruff. Effect of Inlet Residence Time on Analysis of Atmospheric Nitrogen Oxides and Ozone, Anal. Chem., 43:1890, 1971. 27. Slowik, A.A. and E.B. Sansone. Diffusion Losses of Sulfur Dioxide in Sampling Manifolds. J. Air. Poll. Con. Assoc., 24:245, 1974. 28. Yamada, V.M. and R.J. Charlson. Proper Sizing of the Sampling Inlet Line for a Continuous Air Monitoring Station. Environ. Sci. and Technol., 3:483, 1969. 29. Koch, R.C. and H.E. Rector. Optimum Network Design and Site Exposure Criteria for Particulate Matter, GEOMET Technologies, Inc., Rockville, MD. Prepared for U.S. Environmental Protection Agency, Research Triangle Park, NC. EPA Contract No. 68-02-3584. EPA 450/4-87-009. May 1987. 30. Burton, R.M. and J.C. Suggs. Philadelphia Roadway Study. Environmental Monitoring Systems Laboratory, U.S. Environmental Protection Agency, Research Triangle Park, N.C. EPA-600/4-84-070 September 1984. 31. Technical Assistance Document for Sampling and Analysis of Ozone Precursors. Atmospheric Research and Exposure Assessment Laboratory, U.S. Environmental Protection Agency, Research Triangle Park, NC 27711. EPA 600/8-91-215. October 1991. 32. Quality Assurance Handbook for Air Pollution Measurement Systems: Volume IV. Meteorological Measurements. Atmospheric Research and Exposure Assessment Laboratory, U.S. Environmental Protection Agency, Research Triangle Park, NC 27711. EPA 600/4-90-0003. August 1989. 33. On-Site Meteorological Program Guidance for Regulatory Modeling Applications. Office of Air Quality Planning and Standards, U.S. Environmental Protection Agency, Research Triangle Park, NC 27711. EPA 450/4-87-013. June 1987F. 34. Johnson, C., A. Whitehill, R. Long, and R. Vanderpool. Investigation of Gaseous Criteria Pollutant Transport Efficiency as a Function of Tubing Material. U.S. Environmental Protection Agency, Research Triangle Park, NC 27711. EPA/600/R-22/212. August 2022. 35. Hannah Halliday, Cortina Johnson, Tad Kleindienst, Russell Long, Robert Vanderpool, and Andrew Whitehill. Recommendations for Nationwide Approval of Nafion TM [89 FR 16396, Mar. 6, 2024; 89 FR 103656, Dec. 19, 2024] Appendix F to Part 58 [Reserved] Appendix G to Part 58—Uniform Air Quality Index (AQI) and Daily Reporting 1. General Information 2. Reporting Requirements 3. Data Handling 1. General Information 1.1 AQI Overview. 3 2.5 10 2 2 2. Reporting Requirements 2.1 Applicability. 2.2 Contents of AQI Report. 2.2.1 Content of AQI Report Requirements. a. The reporting area(s) (the MSA or subdivision of the MSA). b. The reporting period (the day for which the AQI is reported). c. The main pollutant (the pollutant with the highest index value). d. The AQI (the highest index value). e. The category descriptor and index value associated with the AQI and, if choosing to report in a color format, the associated color. Use only the following descriptors and colors for the six AQI categories: Table 1 to Section 2 of Appendix G—AQI Categories For this AQI Use this descriptor And this color 1 0 to 50 “Good” Green. 51 to 100 “Moderate” Yellow. 101 to 150 “Unhealthy for Sensitive Groups” Orange. 151 to 200 “Unhealthy” Red. 201 to 300 “Very Unhealthy” Purple. 301 and above “Hazardous” Maroon 1 1 https://www.airnow.gov/publications/air-quality-index/technical-assistance-document-for-reporting-the-daily-aqi/. f. The pollutant specific sensitive groups for any reported index value greater than 100. The sensitive groups for each pollutant are identified as part of the periodic review of the air quality criteria and the NAAQS. For convenience, the EPA lists the relevant groups for each pollutant in the most recent reporting guidance (Technical Assistance Document for the Reporting of Daily Air Quality), which can be found at https://www.airnow.gov/publications/air-quality-index/technical-assistance-document-for-reporting-the-daily-aqi/. 2.2.2 Contents of AQI Report When Applicable. a. Appropriate health and cautionary statements. b. The name and index value for other pollutants, particularly those with an index value greater than 100. c. The index values for sub-areas of your MSA. d. Causes for unusually high AQI values. e. Pollutant concentrations. f. Generally, the AQI report applies to an area's MSA only. However, if a significant air quality problem exists (AQI greater than 100) in areas significantly impacted by the MSA but not in it (for example, O 3 2.3. Communication, Timing, and Frequency of AQI Report. a. Reporting the AQI sub-daily is recommended, but not required, to provide more timely air quality information to the public for making health-protective decisions. b. Submitting hourly data in real-time to the EPA's AirNow (or future analogous) system is recommended, but not required, and assists the EPA in providing timely air quality information to the public for making health-protective decisions. c. Submitting hourly data for appropriate monitors (referenced in section 3.2 of this appendix) satisfies the daily AQI reporting requirement because the AirNow system makes daily and sub-daily AQI reports widely available through its website and other communication tools. d. Forecasting the daily AQI provides timely air quality information to the public and is recommended but not required. Sub-daily forecasts are also recommended, especially when air quality is expected to vary substantially throughout the day, like during wildfires. Long-term (multi-day) forecasts can also be made available when useful. 2.4. Exceptions to Reporting Requirements. a. If the index value for a particular pollutant remains below 50 for a season or year, then it may be excluded from the calculation of the AQI in section 3 of this appendix. b. If all index values remain below 50 for a year, then the AQI may be reported at the discretion of the reporting agency. In subsequent years, if pollutant levels rise to where the AQI would be above 50, then the AQI must be reported as required in section 2 of this appendix. c. As previously mentioned in section 2.3 of this appendix, submitting hourly data in real-time from appropriate monitors (referenced in section 3.2 of this appendix) to the EPA's AirNow (or future analogous) system satisfies the daily AQI reporting requirement. 3. Data Handling. 3.1 Relationship of AQI and pollutant concentrations. i.e., 10 2.5 3.2 Monitors Used for AQI Reporting. e.g., 2.5 10 2.5 Reference for relating non-approved PM measurements to approved methods (Eberly, S., T. Fitz-Simons, T. Hanley, L. Weinstock., T. Tamanini, G. Denniston, B. Lambeth, E. Michel, S. Bortnick. Data Quality Objectives (DQOs) For Relating Federal Reference Method (FRM) and Continuous PM 2.5 3.3 AQI Forecast. 2.5 https://www.airnow.gov/publications/weathercasters/guidelines-developing-air-quality-forecasting-program/. 3.4 Calculation and Equations. a. The AQI is the highest value calculated for each pollutant as follows: i. Identify the highest concentration among all of the monitors within each reporting area and truncate as follows: (A) Ozone—truncate to 3 decimal places PM 2.5 PM 10 CO—truncate to 1 decimal place SO 2 NO 2 (B) [Reserved] ii. Using table 2 to this appendix, find the two breakpoints that contain the concentration. iii. Using equation 1 to this appendix, calculate the index. iv. Round the index to the nearest integer. Table 2 to Section 3.4 of Appendix G—Breakpoints for the AQI These breakpoints Equal these AQI's O 3 O 3 1 PM 2.5 3 PM 10 3 CO SO 2 NO 2 AQI Category 0.000-0.054 0.0-9.0 0-54 0.0-4.4 0-35 0-53 0-50 Good. 0.055-0.070 9.1-35.4 55-154 4.5-9.4 36-75 54-100 51-100 Moderate. 0.071-0.085 0.125-0.164 35.5-55.4 155-254 9.5-12.4 76-185 101-360 101-150 Unhealthy for Sensitive Groups. 0.086-0.105 0.165-0.204 55.5-125.4 255-354 12.5-15.4 3 361-649 151-200 Unhealthy. 0.106-0.200 0.205-0.404 125.5—225.4 355-424 15.5-30.4 3 650-1249 201-300 Very Unhealthy. 0.201−( 2 0.405+ 225.5+ 425+ 30.5+ 3 1250+ 301+ 4 1 2 3 3 3 2 2 4 3 2.5 3 10 3 2 2 b. If the concentration is equal to a breakpoint, then the index is equal to the corresponding index value in table 2 to this appendix. However, equation 1 to this appendix can still be used. The results will be equal. If the concentration is between two breakpoints, then calculate the index of that pollutant with equation 1. It should also be noted that in some areas, the AQI based on 1-hour O 3 see 3. Where: I p p C p p BP Hi p BP Lo p I Hi Hi I lo Lo c. If the concentration is larger than the highest breakpoint in table 2 to this appendix then the last two breakpoints in table 2 may be used when equation 1 to this appendix is applied. Example: d. Using table 2 and equation 1 to this appendix, calculate the index value for each of the pollutants measured and select the one that produces the highest index value for the AQI. For example, if a PM 10 3 3 3 i. Find the breakpoints for PM 10 3 3 3 ii. Find the breakpoints for 1-hour O 3 iii. Find the breakpoints for 8-hour O 3 iv. Apply equation 21 to this appendix for 210 µg/m 3 10 v. Apply equation 3 to this appendix for 0.156 ppm, 1-hour O 3 vi. Apply equation 4 to this appendix for 0.130 ppm, 8-hour O 3 vii. Find the maximum, 206. This is the AQI. A minimal AQI report could read: “Today, the AQI for my city is 206, which is Very Unhealthy, due to ozone.” It would then reference the associated sensitive groups. [89 FR 16403, Mar. 6, 2024]

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