WAIS Document Retrieval[Code of Federal Regulations]
[Title 40, Volume 5]
[Revised as of July 1, 2004]
From the U.S. Government Printing Office via GPO Access
[CITE: 40CFR58]

[Page 205-291]
 
                   TITLE 40--PROTECTION OF ENVIRONMENT
 
         CHAPTER I--ENVIRONMENTAL PROTECTION AGENCY (CONTINUED)
 
PART 58_AMBIENT AIR QUALITY SURVEILLANCE

                      Subpart A_General Provisions

Sec.
58.1 Definitions.
58.2 Purpose.
58.3 Applicability.

                      Subpart B_Monitoring Criteria

58.10 Quality assurance.
58.11 Monitoring methods.
58.12 Siting of instruments or instrument probes.
58.13 Operating schedule.
58.14 Special purpose monitors.

        Subpart C_State and Local Air Monitoring Stations (SLAMS)

58.20 Air quality surveillance: plan content.
58.21 SLAMS network design.
58.22 SLAMS methodology.
58.23 Monitoring network completion.
58.24 [Reserved]
58.25 System modification.
58.26 Annual State air monitoring report.
58.27 Compliance date for air quality data reporting.
58.28 SLAMS data submittal.

            Subpart D_National Air Monitoring Stations (NAMS)

58.30 NAMS network establishment.
58.31 NAMS network description.
58.32 NAMS approval.
58.33 NAMS methodology.
58.34 NAMS network completion.
58.35 NAMS data submittal.
58.36 System modification.

      Subpart E_Photochemical Assessment Monitoring Stations (PAMS)

58.40 PAMS network establishment.
58.41 PAMS network description.
58.42 PAMS approval.
58.43 PAMS methodology.
58.44 PAMS network completion.
58.45 PAMS data submittal.
58.46 System modification.

                  Subpart F_Air Quality Index Reporting

58.50 Index reporting.

                      Subpart G_Federal Monitoring

58.60 Federal monitoring.
58.61 Monitoring other pollutants.

Appendix A to Part 58--Quality Assurance Requirements for State and 
          Local Air Monitoring Stations (SLAMS)

[[Page 206]]

Appendix B to Part 58--Quality Assurance Requirements for Prevention of 
          Significant Deterioration (PSD) Air Monitoring
Appendix C to Part 58--Ambient Air Quality Monitoring Methodology
Appendix D to Part 58--Network Design for State and Local Air Monitoring 
          Stations (SLAMS), National Air Monitoring Stations (NAMS), and 
          Photochemical Assessment Monitoring Stations (PAMS)
Appendix E to Part 58--Probe and Monitoring Path Siting Criteria for 
          Ambient Air Quality Monitoring
Appendix F to Part 58--Annual SLAMS Air Quality Information
Appendix G to Part 58--Uniform Air Quality Index (AQI) and Daily 
          Reporting

    Authority: 42 U.S.C. 7410, 7601(a), 7613, and 7619.

    Source: 44 FR 27571, May 10, 1979, as amended at 59 FR 41628, Aug. 
12, 1994.

                      Subpart A_General Provisions

Sec. 58.1  Definitions.

    As used in this part, all terms not defined herein have the meaning 
given them in the Act:
    Act means the Clean Air Act as amended (42 U.S.C. 7401, et seq.).
    Administrator means the Administrator of the Environmental 
Protection Agency (EPA) or his or her authorized representative.
    Aerometric Information Retrieval System (AIRS)-Air Quality Subsystem 
(AQS) is EPA's computerized system for storing and reporting of 
information relating to ambient air quality data.
    Annual State air monitoring report is an annual report, prepared by 
control agencies and submitted to EPA for approval, that consists of an 
annual data summary report for all pollutants and a detailed report 
describing any proposed changes to their air quality surveillance 
network.
    CO means carbon monoxide.
    Community Monitoring Zone (CMZ) means an optional averaging area 
with established, well defined boundaries, such as county or census 
block, within a MPA that has relatively uniform concentrations of annual 
PM<INF>2.5</INF> as defined by appendix D of this part. Two or more core 
SLAMS and other monitors within a CMZ that meet certain requirements as 
set forth in Appendix D of this part may be averaged for making 
comparisons to the annual PM<INF>2.5</INF> NAAQS.
    Consolidated Metropolitan Statistical Area (CMSA) means the most 
recent area as designated by the U.S. Office of Management and Budget 
and population figures from the Bureau of the Census. The Department of 
Commerce provides that within metropolitan complexes of 1 million or 
more population, separate component areas are defined if specific 
criteria are met. Such areas are designated primary metropolitan 
statistical areas (PMSAs; and any area containing PMSAs is designated 
CMSA.
    Core PM<INF>2.5</INF> SLAMS means community-oriented monitoring 
sites representative of community-wide exposures that are the basic 
component sites of the PM<INF>2.5</INF> SLAMS regulatory network. Core 
PM<INF>2.5</INF> SLAMS include community-oriented SLAMS monitors, and 
sites collocated at PAMS.
    Corrected concentration pertains to the result of an accuracy or 
precision assessment test of an open path analyzer in which a high-
concentration test or audit standard gas contained in a short test cell 
is inserted into the optical measurement beam of the instrument. When 
the pollutant concentration measured by the analyzer in such a test 
includes both the pollutant concentration in the test cell and the 
concentration in the atmosphere, the atmospheric pollutant concentration 
must be subtracted from the test measurement to obtain the corrected 
concentration test result. The corrected concentration is equal to the 
measured concentration minus the average of the atmospheric pollutant 
concentrations measured (without the test cell) immediately before and 
immediately after the test.
    Correlated acceptable continuous (CAC) PM analyzer means an optional 
fine particulate matter analyzer that can be used to supplement a 
PM<INF>2.5</INF> reference or equivalent sampler, in accordance with the 
provisions of Sec. 58.13(f).
    Effective concentration pertains to testing an open path analyzer 
with a high-concentration calibration or audit standard gas contained in 
a short test cell inserted into the optical measurement beam of the 
instrument. Effective concentration is the equivalent

[[Page 207]]

ambient-level concentration that would produce the same spectral 
absorbance over the actual atmospheric monitoring path length as 
produced by the high-concentration gas in the short test cell. 
Quantitatively, effective concentration is equal to the actual 
concentration of the gas standard in the test cell multiplied by the 
ratio of the path length of the test cell to the actual atmospheric 
monitoring path length.
    Equivalent method means a method of sampling and analyzing the 
ambient air for an air pollutant that has been designated as an 
equivalent method in accordance with part 53 of this chapter; it does 
not include a method for which an equivalent method designation has been 
canceled in accordance with Sec. 53.11 or Sec. 53.16 of this chapter.
    Indian Governing Body means the governing body of any tribe, band, 
or group of Indians subject to the jurisdiction of the United States and 
recognized by the United States as possessing power of self-government.
    Indian Reservation means any Federally recognized reservation 
established by treaty, agreement, executive order, or act of Congress.
    Local agency means any local government agency, other than the State 
agency, which is charged with the responsibility for carrying out a 
portion of the plan.
    Meteorological measurements means measurements of wind speed, wind 
direction, barometric pressure, temperature, relative humidity, and 
solar radiation.
    Metropolitan Statistical Area (MSA) as designated by the most recent 
decennial U.S. Census of Population Report.
    Monitor is a generic term for an instrument, sampler, analyzer, or 
other device that measures or assists in the measurement of atmospheric 
air pollutants and which is acceptable for use in ambient air 
surveillance under the provisions of appendix C to this part, including 
both point and open path analyzers that have been designated as either 
reference or equivalent methods under part 53 of this chapter and air 
samplers that are specified as part of a manual method that has been 
designated as a reference or equivalent method under part 53 of this 
chapter.
    Monitoring path for an open path analyzer is the actual path in 
space between two geographical locations over which the pollutant 
concentration is measured and averaged.
    Monitoring path length of an open path analyzer is the length of the 
monitoring path in the atmosphere over which the average pollutant 
concentration measurement (path-averaged concentration) is determined. 
See also, optical measurement path length.
    Monitoring Planning Area (MPA) means a contiguous geographic area 
with established, well defined boundaries, such as a metropolitan 
statistical area, county or State, having a common area that is used for 
planning monitoring locations for PM<INF>2.5</INF>. MPAs may cross State 
boundaries, such as the Philadelphia PA-NJ MSA, and be further 
subdivided into community monitoring zones. MPAs are generally oriented 
toward areas with populations greater than 200,000, but for convenience, 
those portions of a State that are not associated with MSAs can be 
considered as a single MPA. MPAs must be defined, where applicable, in a 
State PM monitoring network description.
    NAMS means National Air Monitoring Station(s). Collectively the NAMS 
are a subset of the SLAMS ambient air quality monitoring network.
    NO<INF>2</INF> means nitrogen dioxide. NO means nitrogen oxide. 
NO<INF>X</INF> means oxides of nitrogen and is defined as the sum of the 
concentrations of NO<INF>2</INF> and NO.
    O<INF>3</INF> means ozone.
    Open path analyzer is an automated analytical method that measures 
the average atmospheric pollutant concentration in situ along one or 
more monitoring paths having a monitoring path length of 5 meters or 
more and that has been designated as a reference or equivalent method 
under the provisions of part 53 of this chapter.
    Optical measurement path length is the actual length of the optical 
beam over which measurement of the pollutant is determined. The path-
integrated pollutant concentration measured by the analyzer is divided 
by the optical measurement path length to determine

[[Page 208]]

the path-averaged concentration. Generally, the optical measurement path 
length is:
    (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 means Photochemical Assessment Monitoring Stations.
    Particulate matter monitoring network description, required by Sec. 
58.20(f), means a detailed plan, prepared by control agencies and 
submitted to EPA for approval, that describes their PM<INF>2.5</INF> and 
PM<INF>10</INF> air quality surveillance network.
    Pb means lead.
    Plan means an implementation plan, approved or promulgated pursuant 
to section 110 of the Clean Air Act.
    PM<INF>2.5</INF> means particulate matter with an aerodynamic 
diameter less than or equal to a nominal 2.5 micrometers as measured by 
a reference method based on 40 CFR part 50, Appendix L, and designated 
in accordance with part 53 of this chapter or by an equivalent method 
designated in accordance with part 53 of this chapter.
    PM<INF>10</INF> means particulate matter with an aerodynamic 
diameter less than or equal to a nominal 10 micrometers as measured by a 
reference method based on appendix J of part 50 of this chapter and 
designated in accordance with part 53 of this chapter or by an 
equivalent method designated in accordance with part 53 of this chapter.
    Point analyzer is an automated analytical method that measures 
pollutant concentration in an ambient air sample extracted from the 
atmosphere at a specific inlet probe point and that has been designated 
as a reference or equivalent method in accordance with part 53 of this 
chapter.
    Population-oriented monitoring (or sites) applies to residential 
areas, commercial areas, recreational areas, industrial areas, and other 
areas where a substantial number of people may spend a significant 
fraction of their day.
    Primary Metropolitan Statistical Area (PMSA) is a separate component 
of a consolidated metropolitan statistical area. For the purposes of 
this part, PMSA is used interchangeably with MSA.
    Probe is the actual inlet where an air sample is extracted from the 
atmosphere for delivery to a sampler or point analyzer for pollutant 
analysis.
    PSD station means any station operated for the purpose of 
establishing the effect on air quality of the emissions from a proposed 
source for purposes of prevention of significant deterioration as 
required by Sec. 51.24(n) of part 51 of this chapter.
    Reference method means a method of sampling and analyzing the 
ambient air for an air pollutant that will be specified as a reference 
method in an appendix to part 50 of this chapter, or a method that has 
been designated as a reference method in accordance with this part; it 
does not include a method for which a reference method designation has 
been canceled in accordance with Sec. 53.11 or Sec. 53.16 of this 
chapter.
    Regional Administrator means the Administrator of one of the ten EPA 
Regional Offices or his or her authorized representative.
    SAROAD site identification form is one of the several forms in the 
SAROAD system. It is the form which provides a complete description of 
the site (and its surroundings) of an ambient air quality monitoring 
station.
    SLAMS means State or Local Air Monitoring Station(s). The SLAMS make 
up the ambient air quality monitoring network which is required by Sec. 
58.20 to be provided for in the State's implementation plan. This 
definition places no restrictions on the use of the physical structure 
or facility housing the SLAMS. Any combination of SLAMS and any other 
monitors (Special Purpose, NAMS, PSD) may occupy the same facility or 
structure without affecting the respective definitions of those 
monitoring station.
    SO<INF>2</INF> means sulfur dioxide.
    Special Purpose Monitor (SPM) is a generic term used for all 
monitors other

[[Page 209]]

than SLAMS, NAMS, PAMS, and PSD monitors included in an agency's 
monitoring network for monitors used in a special study whose data are 
officially reported to EPA.
    State agency means the air pollution control agency primarily 
responsible for development and implementation of a plan under the Act.
    Storage and Retrieval of Aerometric Data (SAROAD) system is a 
computerized system which stores and reports information relating to 
ambient air quality. The SAROAD system has been replaced with the AIRS-
AQS system; however, the SAROAD data reporting format continues to be 
used by some States and local air pollution agencies as an interface to 
AIRS on an interim basis.
    Traceable means that a local standard has been compared and 
certified, either directly or via not more than one intermediate 
standard, to a National Institute of Standards and Technology (NIST)-
certified primary standard such as a NIST-Traceable Reference Material 
(NTRM) or a NIST-certified Gas Manufacturer's Internal Standard (GMIS).
    TSP (total suspended particulates) means particulate matter as 
measured by the method described in appendix B of part 50 of this 
chapter,
    Urban area population means the population defined in the most 
recent decennial U.S. Census of Population Report.
    VOC means volatile organic compounds.

[44 FR 27571, May 10, 1979, as amended at 48 FR 2529, Jan. 20, 1983; 51 
FR 9586, Mar. 19, 1986; 52 FR 24739, July 1, 1987; 58 FR 8467, Feb. 12, 
1993; 59 FR 41628, 41629, Aug. 12, 1994; 60 FR 52319, Oct. 6, 1995; 62 
FR 38830, July 18, 1997; 63 FR 7714, Feb. 17, 1998]

Sec. 58.2  Purpose.

    (a) This part contains criteria and requirements for ambient air 
quality monitoring and requirements for reporting ambient air quality 
data and 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.
    (b) The requirements pertaining to provisions for an air quality 
surveillance system in the State Implementation Plan 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. This 
network will be operated by the States and will consist of certain 
selected stations from the States' SLAMS networks. These selected 
stations will remain as SLAMS and will continue to meet any applicable 
requirements on SLAMS. The stations, however, will also be designated as 
National Air Monitoring Stations (NAMS) and will be subject to 
additional data reporting and monitoring methodology requirements as 
contained in subpart D of this part.
    (d) This section also acts to establish a Photochemical Assessment 
Monitoring Stations (PAMS) network as a subset of the State's SLAMS 
network for the purpose of enhanced monitoring in O<INF>3</INF> 
nonattainment areas listed as serious, severe, or extreme. The PAMS 
network will be subject to the data reporting and monitoring methodology 
requirements as contained in subpart E of this part.
    (e) Requirements for the daily reporting of an index of ambient air 
quality, to insure that the population of major urban areas are informed 
daily of local air quality conditions, are also included in this part.

[44 FR 27571, May 10, 1979, as amended at 58 FR 8467, Feb. 12, 1993]

Sec. 58.3  Applicability.

    This part applies to:
    (a) State air pollution control agencies.
    (b) Any local air pollution control agency or Indian governing body 
to which the State has delegated authority to operate a portion of the 
State's SLAMS network.
    (c) Owners or operators of proposed sources.

[[Page 210]]

                      Subpart B_Monitoring Criteria

Sec. 58.10  Quality assurance.

    (a) Appendix A to this part contains quality assurance criteria to 
be followed when operating the SLAMS network.
    (b) Appendix B to this part contains the quality assurance criteria 
to be followed by the owner or operator of a proposed source when 
operating a PSD station.

Sec. 58.11  Monitoring methods.

    Appendix C to this part contains the criteria to be followed in 
determining acceptable monitoring methods or instruments for use in 
SLAMS.

Sec. 58.12  Siting of instruments or instrument probes.

    Appendix E to this part contains criteria for siting instruments or 
instrument probes for SLAMS.

Sec. 58.13  Operating schedule.

    Ambient air quality data collected at any SLAMS must be collected as 
follows:
    (a) For continuous analyzers--consecutive hourly averages except 
during:
    (1) Periods of routine maintenance,
    (2) Periods of instrument calibration, or
    (3) Periods or seasons exempted by the Regional Administrator.
    (b) For manual methods (excluding PM<INF>10</INF> samplers, 
PM<INF>2.5</INF> samplers, and PAMS VOC samplers), at least one 24-hour 
sample must be obtained every sixth day except during periods or seasons 
exempted by the Regional Administrator.
    (c) For PAMS VOC samplers, samples must be obtained as specified in 
sections 4.3 and 4.4 of appendix D to this part. Area-specific PAMS 
operating schedules must be included as part of the network description 
required by Sec. 58.40 and must be approved by the Administrator.
    (d) For PM<INF>10</INF> samplers--a 24-hour sample must be taken a 
minimum of every third day, except during periods or seasons exempted by 
the Regional Administrator.
    (e) For PM<INF>2.5</INF> samplers, a 24-hour sample is required 
everyday for certain core SLAMS, including certain PAMS, as described in 
section 2.8.1.3 of appendix D of this part, except during seasons or 
periods of low PM<INF>2.5</INF> as otherwise exempted by the Regional 
Administrator. A waiver of the everyday sampling schedule for SLAMS may 
be granted by the Regional Administrator or designee, and for NAMS by 
the Administrator or designee, for 1 calendar year from the time a 
PM<INF>2.5</INF> sequential sampler (FRM or Class I equivalent) has been 
approved by EPA. A 24-hour sample must be taken a minimum of every third 
day for all other SLAMS, including NAMS, as described in section 2.8.1.3 
of appendix D of this part, except when exempted by the Regional 
Administrator in accordance with forthcoming EPA guidance. During 
periods for which exemptions to every third day or every day sampling 
are allowed for core PM<INF>2.5</INF> SLAMS, a minimum frequency of one 
in 6-day sampling is still required. However, alternative sampling 
frequencies are allowed for SLAMS sites that are principally intended 
for comparisons to the 24-hour NAAQS. Such modifications must be 
approved by the Regional Administrator.
    (f) Alternatives to everyday sampling at sites with correlated 
acceptable continuous analyzers. (1) Certain PM<INF>2.5</INF> core SLAMS 
sites located in monitoring planning areas (as described in section 2.8 
of appendix D of this part) are required to sample every day with a 
reference or equivalent method operating in accordance with part 53 of 
this chapter and section 2 of appendix C of this part. However, in 
accordance with the monitoring priority as defined in paragraph (f)(2) 
of this section, established by the control agency and approved by EPA, 
a core SLAMS monitor may operate with a reference or equivalent method 
on a 1 in 3-day schedule and produce data that may be compared to the 
NAAQS, provided that it is collocated with an acceptable continuous fine 
particulate PM analyzer that is correlated with the reference or 
equivalent method. If the alternative sampling schedule is selected by 
the control agency and approved by EPA, the alternative schedule shall 
be implemented on January 1 of the year in which everyday sampling is 
required. The selection of correlated acceptable

[[Page 211]]

continuous PM analyzers and procedures for correlation with the 
intermittent reference or equivalent method shall be in accordance with 
procedures approved by the Regional Administrator. Unless the continuous 
fine particulate analyzer satisfies the requirements of section 2 of 
appendix C of this part, however, the data derived from the correlated 
acceptable continuous monitor are not eligible for direct comparisons to 
the NAAQS in accordance with part 50 of this chapter.
    (2) A Metropolitan Statistical Area (MSA) (or primary metropolitan 
statistical area) with greater than 1 million population and high 
concentrations of PM<INF>2.5</INF> (greater than or equal to 80 percent 
of the NAAQS) shall be a Priority 1 PM monitoring area. Other monitoring 
planning areas may be designated as Priority 2 PM monitoring areas.
    (3) Core SLAMS having a correlated acceptable continuous analyzer 
collocated with a reference or equivalent method in a Priority 1 PM 
monitoring area may operate on the 1 in 3 sampling frequency only after 
reference or equivalent data are collected for at least 2 complete 
years.
    (4) In all monitoring situations, with a correlated acceptable 
continuous alternative, FRM samplers or filter-based equivalent 
analyzers should preferably accompany the correlated acceptable 
continuous monitor.

[44 FR 27571, May 10, 1979, as amended at 52 FR 24739, July 1, 1987; 58 
FR 8467, Feb. 12, 1993; 62 FR 38831, July 18, 1997; 63 FR 7714, Feb. 17, 
1998]

Sec. 58.14  Special purpose monitors.

    (a) Except as specified in paragraph (b) of this section, any 
ambient air quality monitoring station other than a SLAMS or PSD station 
from which the State intends to use the data as part of a demonstration 
of attainment or nonattainment or in computing a design value for 
control purposes of the National Ambient Air Quality Standards (NAAQS) 
must meet the requirements for SLAMS as described in Sec. 58.22 and, 
after January 1, 1983, must also meet the requirements for SLAMS 
described in Sec. 58.13 and Appendices A and E of this part.
    (b) Based on the need, in transitioning to a PM<INF>2.5</INF> 
standard that newly addresses the ambient impacts of fine particles, to 
encourage a sufficiently extensive geographical deployment of 
PM<INF>2.5</INF> monitors and thus hasten the development of an adequate 
PM<INF>2.5</INF> ambient air quality monitoring infrastructure, 
PM<INF>2.5</INF> NAAQS violation determinations shall not be exclusively 
made based on data produced at a population-oriented SPM site during the 
first 2 complete calendar years of its operation. However, a notice of 
NAAQS violations resulting from population-oriented SPMs shall be 
reported to EPA in the State's annual monitoring report and be 
considered by the State in the design of its overall SLAMS network; 
these population-oriented SPMs should be considered to become a 
permanent SLAMS during the annual network review in accordance with 
Sec. 58.25.
    (c) Any ambient air quality monitoring station other than a SLAMS or 
PSD station from which the State intends to use the data for SIP-related 
functions other than as described in paragraph (a) of this section is 
not necessarily required to comply with the requirements for a SLAMS 
station under paragraph (a) of this section but must be operated in 
accordance with a monitoring schedule, methodology, quality assurance 
procedures, and probe or instrument-siting specifications approved by 
the Regional Administrator.

[62 FR 38832, July 18, 1997]

        Subpart C_State and Local Air Monitoring Stations (SLAMS)

Sec. 58.20  Air quality surveillance: plan content.

    By January 1, 1980, the State shall adopt and submit to the 
Administrator a revision to the plan which will:
    (a) Provide for the establishment of an air quality surveillance 
system that consists of a network of monitoring stations designated as 
State and Local Air Monitoring Stations (SLAMS) which measure ambient 
concentrations of those pollutants for which standards have been 
established in part 50 of this chapter. SLAMS (including NAMS) 
designated as PAMS will also obtain

[[Page 212]]

ambient concentrations of speciated VOC and NO<INF>X</INF>, and 
meteorological measurements. PAMS may therefore be located at existing 
SLAMS or NAMS sites when appropriate.
    (b) Provide for meeting the requirements of appendices A, C, D, and 
E to this part.
    (c) Provide for the operation of at least one SLAMS per criteria 
pollutant except Pb during any stage of an air pollution episode as 
defined in the plan.
    (d) Provide for the review of the air quality surveillance system on 
an annual basis to determine if the system meets the monitoring 
objectives defined in appendix D of this part. Such review must identify 
needed modifications to the network such as termination or relocation of 
unnecessary stations or establishment of new stations that are 
necessary. For PM<INF>2.5</INF>, the review must identify needed changes 
to core SLAMS, monitoring planning areas, the chosen community 
monitoring approach including optional community monitoring zones, 
SLAMS, or SPMs.
    (e) Provide for having a SLAMS network description available for 
public inspection and submission to the Administrator upon request. The 
network description must be available at the time of plan revision 
submittal and must contain the following information for each SLAMS:
    (1) The AIRS site identification form for existing stations.
    (2) The proposed location for scheduled stations.
    (3) The sampling and analysis method.
    (4) The operating schedule.
    (5) The monitoring objective and spatial scale of representativeness 
as defined in appendix D to this part.
    (6) A schedule for:
    (i) Locating, placing into operation, and making available the AIRS 
site identification form for each SLAMS which is not located and 
operating at the time of plan revision submittal,
    (ii) Implementing quality assurance procedures of appendix A to this 
part for each SLAMS for which such procedures are not implemented at the 
time of plan revision submittal, and
    (iii) Resiting each SLAMS which does not meet the requirements of 
appendix E to this part at the time of plan revision submittal.
    (f) Provide for having a PM monitoring network description available 
for public inspection which must provide for monitoring planning areas, 
and the community monitoring approach involving core monitors and 
optional community monitoring zones for PM<INF>2.5</INF>. The PM 
monitoring network description for PM<INF>10</INF> and PM<INF>2.5</INF> 
must be submitted to the Regional Administrator for approval by July 1, 
1998, and must contain the following information for each PM SLAMS and 
PM<INF>2.5</INF> SPM:
    (1) The AIRS site identification form for existing stations.
    (2) The proposed location for scheduled stations.
    (3) The sampling and analysis method.
    (4) The operating schedule.
    (5) The monitoring objective, spatial scale of representativeness, 
and additionally for PM<INF>2.5</INF>, the monitoring planning area, 
optional community monitoring zone, and the site code designation to 
identify which site will be identified as core SLAMS; and SLAMS or 
population-oriented SPMs, if any, that are microscale or middle scale in 
their representativeness as defined in appendix D of this part.
    (6) A schedule for:
    (i) Locating, placing into operation, and making available the AIRS 
site identification form for each SLAMS which is not located and 
operating at the time of plan revision submittal.
    (ii) Implementing quality assurance procedures of appendix A of this 
part for each SLAMS for which such procedures are not implemented at the 
time of plan revision submittal.
    (iii) Resiting each SLAMS which does not meet the requirements of 
appendix E of this part at the time of plan revision submittal.
    (g) Provide for having a list of all PM<INF>2.5</INF> monitoring 
locations including SLAMS, NAMS, PAMS and population-oriented SPMs, that 
are included in the State's PM monitoring network description and are 
intended for comparison to the NAAQS, available for public inspection.
    (h) Within 9 months after;

[[Page 213]]

    (1) February 12, 1993; or
    (2) Date of redesignation or reclassification of any existing 
O<INF>3</INF> nonattainment area to serious, severe, or extreme; or
    (3) The designation of a new area and classification to serious, 
severe, or extreme, affected States shall adopt and submit a plan 
revision to the Administrator.
    (i) The plan revision will provide for the establishment and 
maintenance of PAMS. Each PAMS site will provide for the monitoring of 
ambient concentrations of criteria pollutants (O<INF>3</INF>, 
NO<INF>2</INF>), and non-criteria pollutants (NO<INF>X</INF>, NO, and 
speciated VOC) as stipulated in section 4.2 of appendix D, and 
meteorological measurements. The PAMS network is part of the SLAMS 
network, and the plan provisions in paragraphs (a) through (h) of this 
section will apply to the revision. Since NAMS sites are also part of 
the SLAMS network, some PAMS sites may be coincident with NAMS sites and 
may be designated as both PAMS and NAMS.

[44 FR 27571, May 10, 1979, as amended at 46 FR 44164, Sept. 3, 1981; 52 
FR 24740, July 1, 1987; 58 FR 8467, Feb. 12, 1993; 59 FR 41628, Aug. 12, 
1994; 62 FR 38832, July 18, 1997]

Sec. 58.21  SLAMS network design.

    The design criteria for SLAMS contained in appendix D to this part 
must be used in designing the SLAMS network. The State shall consult 
with the Regional Administrator during the network design process. The 
final network design will be subject to the approval of the Regional 
Administrator.

Sec. 58.22  SLAMS methodology.

    Each SLAMS must meet the monitoring methodology requirements of 
appendix C to this part at the time the station is put into operation as 
a SLAMS.

Sec. 58.23  Monitoring network completion.

    With the exception of the PM<INF>10</INF> monitoring networks that 
shall be in place by March 16, 1998 and with the exception of the 
PM<INF>2.5</INF> monitoring networks as described in paragraph (c) of 
this section:
    (a) Each station in the SLAMS network must be in operation, be sited 
in accordance with the criteria in appendix E to this part, and be 
located as described on the station's AIRS site identification form, and
    (b) The quality assurance requirements of appendix A to this part 
must be fully implemented.
    (c) Each PM<INF>2.5</INF> station in the SLAMS network must be in 
operation in accordance with the minimum requirements of appendix D of 
this part, be sited in accordance with the criteria in appendix E of 
this part, and be located as described on the station's AIRS site 
identification form, according to the following schedule:
    (1) Within 1 year after September 16, 1997, at least one required 
core PM<INF>2.5</INF> SLAMS site in each MSA with population greater 
than 500,000, plus one site in each PAMS area, (plus at least two 
additional SLAMS sites per State) must be in operation.
    (2) Within 2 years after September 16, 1997, all other required 
SLAMS, including all required core SLAMS, required regional background 
and regional transport SLAMS, continuous PM monitors in areas with 
greater than 1 million population, and all additional required 
PM<INF>2.5</INF> SLAMS must be in operation.
    (3) Within 3 years after September 16, 1997, all additional sites 
(e.g., sites classified as SLAMS/SPM to complete the mature network) 
must be in operation.

[44 FR 27571, May 10, 1979, as amended at 52 FR 24740, July 1, 1987; 59 
FR 41628, Aug. 12, 1994; 62 FR 38832, July 18, 1997]

Sec. 58.24  [Reserved]

Sec. 58.25  System modification.

    The State shall annually develop and implement a schedule to modify 
the ambient air quality monitoring network to eliminate any unnecessary 
stations or to correct any inadequacies indicated by the result of the 
annual review required by Sec. 58.20(d). The State shall consult with 
the Regional Administrator during the development of the schedule to 
modify the monitoring program. The final schedule and modifications will 
be subject to the approval of the Regional Administrator. Nothing in 
this section will preclude the State,

[[Page 214]]

with the approval of the Regional Administrator, from making 
modifications to the SLAMS network for reasons other than those 
resulting from the annual review.

Sec. 58.26  Annual State air monitoring report.

    (a) The State shall submit to the Administrator (through the 
appropriate Regional Office) an annual summary report of all the ambient 
air quality monitoring data from all monitoring stations designated 
State and Local Air Monitoring Stations (SLAMS). The annual report must 
be submitted by July 1 of each year for data collected from January 1 to 
December 31 of the previous year.
    (b) The SLAMS annual data summary report must contain:
    (1) The information specified in appendix F,
    (2) The location, date, pollution source, and duration of each 
incident of air pollution during which ambient levels of a pollutant 
reached or exceeded the level specified by Sec. 51.16(a) of this 
chapter as a level which could cause significant harm to the health of 
persons.
    (c) The senior air pollution control officer in the State or his 
designee shall certify that the annual summary report is accurate to the 
best of his knowledge.
    (d) For PM monitoring and data--
    (1) The State shall submit a summary to the appropriate Regional 
Office (for SLAMS) or Administrator (through the Regional Office) (for 
NAMS) that details proposed changes to the PM Monitoring Network 
Description and to be in accordance with the annual network review 
requirements in Sec. 58.25. This shall discuss the existing PM 
networks, including modifications to the number, size or boundaries of 
monitoring planning areas and optional community monitoring zones; 
number and location of PM<INF>10</INF> and PM<INF>2.5</INF> SLAMS; 
number and location of core PM<INF>2.5</INF> SLAMS; alternative sampling 
frequencies proposed for PM<INF>2.5</INF> SLAMS (including core 
PM<INF>2.5</INF> SLAMS and PM<INF>2.5</INF> NAMS), core PM<INF>2.5</INF> 
SLAMS to be designated PM<INF>2.5</INF> NAMS; and PM<INF>10</INF> and 
PM<INF>2.5</INF> SLAMS to be designated PM<INF>10</INF> and 
PM<INF>2.5</INF> NAMS respectively.
    (2) The State shall submit an annual summary to the appropriate 
Regional Office of all the ambient air quality monitoring PM data from 
all special purpose monitors that are described in the State's PM 
monitoring network description and are intended for SIP purposes. These 
include those population-oriented SPMs that are eligible for comparison 
to the PM<INF>2.5</INF> NAAQS. The State shall certify the data in 
accordance with paragraph (c) of this section.
    (e) The Annual State Air Monitoring Report shall be submitted to the 
Regional Administrator by July 1 or by an alternative annual date to be 
negotiated between the State and Regional Administrator. The Region 
shall provide review and approval/disapproval within 60 days. After 3 
years following September 16, 1997, the schedule for submitting the 
required annual revised PM<INF>2.5</INF> monitoring network description 
may be altered based on a new schedule determined by the Regional 
Administrator. States may submit an alternative PM monitoring network 
description in which it requests exemptions from specific required 
elements of the network design (e.g., required number of core sites, 
other SLAMS, sampling frequency, etc.). After 3 years following 
September 16, 1997 or once a monitoring area has been determined to 
violate the NAAQS, then changes to an MPA monitoring network affecting 
the violating locations shall require public review and notification.

[44 FR 27571, May 10, 1979, as amended at 51 FR 9586, Mar. 19, 1986; 62 
FR 38833, July 18, 1997; 63 FR 7714, Feb. 17, 1998]

Sec. 58.27  Compliance date for air quality data reporting.

    The annual air quality data reporting requirements of Sec. 58.26 
apply to data collected after December 31, 1980. Data collected before 
January 1, 1981, must be reported under the reporting procedures in 
effect before the effective date of subpart C of this part.

Sec. 58.28  SLAMS data submittal.

    The State shall submit all of the SLAMS data according to the same 
data submittal requirements as defined for NAMS in section 58.35. The 
State shall also submit any portion or all of

[[Page 215]]

the SLAMS data to the appropriate Regional Administrator upon request.

[59 FR 41628, Aug. 12, 1994]

            Subpart D_National Air Monitoring Stations (NAMS)

Sec. 58.30  NAMS network establishment.

    (a) By January 1, 1980, with the exception of PM<INF>10</INF> and 
PM<INF>2.5</INF> samplers, which shall be by July 1, 1998, the State 
shall:
    (1) Establish, through the operation of stations or through a 
schedule for locating and placing stations into operation, that portion 
of a National Ambient Air Quality Monitoring Network which is in that 
State, and
    (2) Submit to the Administrator (through the appropriate Regional 
Office) a description of that State's portion of the network.
    (b) Hereinafter, the portion of the national network in any State 
will be referred to as the NAMS network.
    (c) The stations in the NAMS network must be stations from the SLAMS 
network required by Sec. 58.20.
    (d) The requirements of appendix D to this part must be met when 
designing the NAMS network. The process of designing the NAMS network 
must be part of the process of designing the SLAMS network as explained 
in appendix D to this part.

[44 FR 27571, May 10, 1979, as amended at 46 FR 44164, Sept. 3, 1981; 52 
FR 24740, July 1, 1987; 62 FR 38833, July 18, 1997]

Sec. 58.31  NAMS network description.

    The NAMS network description required by Sec. 58.30 must contain 
the following for all stations, existing or scheduled:
    (a) The AIRS site identification number for existing stations.
    (b) The proposed location for scheduled stations.
    (c) Identity of the urban area represented.
    (d) The sampling and analysis method.
    (e) The operating schedule.
    (f) The monitoring objective, spatial scale of representativeness, 
and for PM<INF>2.5</INF>, the monitoring planning area and community 
monitoring zones, as defined in appendix D of this part.
    (g) A schedule for:
    (1) Locating, placing into operation, and submitting the AIRS site 
identification form for each NAMS which is not located and operating at 
the time of network description submittal,
    (2) Implementing quality assurance procedures of appendix A to this 
part for each NAMS for which such procedures are not implemented at the 
time of network description submittal, and
    (3) Resiting each NAMS which does not meet the requirements of 
appendix E to this part at the time of network description submittal.

[44 FR 27571, May 10, 1979, as amended at 59 FR 41628, Aug. 12, 1994; 62 
FR 38833, July 18, 1997; 63 FR 7714, Feb. 17, 1998; 64 FR 3034, Jan. 20, 
1999]

Sec. 58.32  NAMS approval.

    The NAMS network required by Sec. 58.30 is subject to the approval 
of the Administrator. Such approval will be contingent upon completion 
of the network description as outlined in Sec. 58.31 and upon 
conformance to the NAMS design criteria contained in appendix D to this 
part.

Sec. 58.33  NAMS methodology.

    Each NAMS must meet the monitoring methodology requirements of 
appendix C to this part applicable to NAMS at the time the station is 
put into operation as a NAMS.

Sec. 58.34  NAMS network completion.

    With the exception of PM<INF>10</INF> samplers, which shall be by 1 
year after September 16, 1997, and PM<INF>2.5</INF>, which shall be by 3 
years after September 16, 1997:
    (a) Each NAMS must be in operation, be sited in accordance with the 
criteria in Appendix E to this part, and be located as described in the 
AIRS database; and
    (b) The quality assurance requirements of appendix A to this part 
must be fully implemented for all NAMS.

[44 FR 27571, May 10, 1979, as amended at 46 FR 44164, Sept. 3, 1981; 52 
FR 24740, July 1, 1987; 59 FR 41628, Aug. 12, 1994; 62 FR 38833, July 
18, 1997; 64 FR 3034, Jan. 20, 1999]

Sec. 58.35  NAMS data submittal.

    (a) The requirements of this section apply to those stations 
designated as

[[Page 216]]

both SLAMS and NAMS by the network description required by Sec. Sec. 
58.20 and 58.30.
    (b) The State shall report to the Administrator all ambient air 
quality data for SO<INF>2</INF>, CO, O<INF>3</INF>, NO<INF>2</INF>, Pb, 
PM<INF>10</INF>, and PM<INF>2.5</INF>, and information specified by the 
AIRS Users Guide (Volume II, Air Quality Data Coding, and Volume III, 
Air Quality Data Storage) to be coded into the AIRS-AQS format. Such air 
quality data and information must be submitted directly to the AIRS-AQS 
via either electronic transmission or magnetic tape, in the format of 
the AIRS-AQS, and in accordance with the quarterly schedule described in 
paragraph (c) of this section.
    (c) 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:
    (1) Contain all data and information gathered during the reporting 
period.
    (2) Be received in the AIRS-AQS within 90 days after the end of the 
quarterly reporting period. For example, the data for the reporting 
period January 1-March 31, 1994 are due on or before June 30, 1994.
    (d) Air quality data submitted for each reporting period must be 
edited, validated, and entered into the AIRS-AQS for updating (within 
the time limits specified in paragraph (c) of this section) pursuant to 
appropriate AIRS-AQS procedures. The procedures for editing and 
validating data are described in the AIRS Users Guide, Volume II Air 
Quality Data Coding.
    (e) This section does not permit a State to exempt those SLAMS which 
are also designated as NAMS from all or any of the reporting 
requirements applicable to SLAMS in Sec. 58.26.

[44 FR 27571, May 10, 1979, as amended at 46 FR 44164, Sept. 3, 1981; 51 
FR 9586, Mar. 19, 1986; 52 FR 24740, July 1, 1987; 59 FR 41628, Aug. 12, 
1994; 62 FR 38833, July 18, 1997]

Sec. 58.36  System modification.

    During the annual SLAMS Network Review specified in Sec. 58.20, any 
changes to the NAMS network identified by the EPA and/or proposed by the 
State and agreed to by the EPA will be evaluated. These modifications 
should address changes invoked by a new census and changes to the 
network due to changing air quality levels, emission patterns, etc. The 
State shall be given one year (until the next annual evaluation) to 
implement the appropriate changes to the NAMS network.

[51 FR 9586, Mar. 19, 1986]

      Subpart E_Photochemical Assessment Monitoring Stations (PAMS)

    Source: 58 FR 8468, Feb. 12, 1993, unless otherwise noted.

Sec. 58.40  PAMS network establishment.

    (a) In addition to the plan revision, the State shall submit a 
photochemical assessment monitoring network description including a 
schedule for implementation to the Administrator within 6 months after;
    (1) February 12, 1993; or
    (2) Date of redesignation or reclassification of any existing 
O<INF>3</INF> nonattainment area to serious, severe, or extreme; or
    (3) The designation of a new area and classification to serious, 
severe, or extreme O<INF>3</INF> nonattainment.

The network description will apply to all serious, severe, and extreme 
O<INF>3</INF> nonattainment areas within the State. Some O<INF>3</INF> 
nonattainment areas may extend beyond State or Regional boundaries. In 
instances where PAMS network design criteria as defined in appendix D to 
this part require monitoring stations located in different States and/or 
Regions, the network description and implementation schedule should be 
submitted jointly by the States involved. When appropriate, such 
cooperation and joint network design submittals are preferred. Network 
descriptions shall be submitted through the appropriate Regional 
Office(s). Alternative networks, including different monitoring 
schedules, periods, or methods, may be submitted, but they must include 
a demonstration that they satisfy the monitoring data uses and fulfill 
the PAMS monitoring objectives described in sections 4.1 and 4.2 of 
appendix D to this part.
    (b) For purposes of plan development and approval, the stations 
established

[[Page 217]]

or designated as PAMS must be stations from the SLAMS network or become 
part of the SLAMS network required by Sec. 58.20.
    (c) The requirements of appendix D to this part applicable to PAMS 
must be met when designing the PAMS network.

Sec. 58.41  PAMS network description.

    The PAMS network description required by Sec. 58.40 must contain 
the following:
    (a) Identification of the monitoring area represented.
    (b) The AIRS site identification number for existing stations.
    (c) The proposed location for scheduled stations.
    (d) Identification of the site type and location within the PAMS 
network design for each station as defined in appendix D to this part 
except that during any year, a State may choose to submit detailed 
information for the site scheduled to begin operation during that year's 
PAMS monitoring season, and defer submittal of detailed information on 
the remaining sites until succeeding years. Such deferred network design 
phases should be submitted to EPA for approval no later than January 1 
of the first year of scheduled operation. As a minimum, general 
information on each deferred site should be submitted each year until 
final approval of the complete network is obtained from the 
Administrator.
    (e) The sampling and analysis method for each of the measurements.
    (f) The operating schedule for each of the measurements.
    (g) An O<INF>3</INF> event forecasting scheme, if appropriate.
    (h) A schedule for implementation. This schedule should include the 
following:
    (1) A timetable for locating and submitting the AIRS site 
identification form for each scheduled PAMS that is not located at the 
time of submittal of the network description;
    (2) A timetable for phasing-in operation of the required number and 
type of sites as defined in appendix D to this part; and
    (3) A schedule for implementing the quality assurance procedures of 
appendix A to this part for each PAMS.

[58 FR 8468, Feb. 12, 1993, as amended at 64 FR 3035, Jan. 20, 1999]

Sec. 58.42  PAMS approval.

    The PAMS network required by Sec. 58.40 is subject to the approval 
of the Administrator. Such approval will be contingent upon completion 
of each phase of the network description as outlined in Sec. 58.41 and 
upon conformance to the PAMS network design criteria contained in 
appendix D to this part.

Sec. 58.43  PAMS methodology.

    PAMS monitors must meet the monitoring methodology requirements of 
appendix C to this part applicable to PAMS.

Sec. 58.44  PAMS network completion.

    (a) The complete, operational PAMS network will be phased in as 
described in appendix D to this part over a period of 5 years after;
    (1) February 12, 1993; or
    (2) Date of redesignation or reclassification of any existing 
O<INF>3</INF> nonattainment area to serious, severe, or extreme; or
    (3) The designation of a new area and classification to serious, 
severe, or extreme O<INF>3</INF> nonattainment.
    (b) The quality assurance criteria of appendix A to this part must 
be implemented for all PAMS.

Sec. 58.45  PAMS data submittal.

    (a) The requirements of this section apply only to those stations 
designated as PAMS by the network description required by Sec. 58.40.
    (b) All data shall be submitted to the Administrator in accordance 
with the format, reporting periods, reporting deadlines, and other 
requirements as specified for NAMS in Sec. 58.35.
    (c) The State shall report NO and NO<INF>X</INF> data consistent 
with the requirements of Sec. 58.35 for criteria pollutants.
    (d) The State shall report VOC data and meteorological data within 6 
months following the end of each quarterly reporting period.

[[Page 218]]

Sec. 58.46  System modification.

    (a) Any proposed changes to the PAMS network description will be 
evaluated during the annual SLAMS Network Review specified in Sec. 
58.20. Changes proposed by the State must be approved by the 
Administrator. The State will be allowed 1 year (until the next annual 
evaluation) to implement the appropriate changes to the PAMS network.
    (b) PAMS network requirements are mandatory only for serious, 
severe, and extreme O<INF>3</INF> nonattainment areas. When any such 
area is redesignated to attainment, the State may revise its PAMS 
monitoring program subject to approval by the Administrator.

                  Subpart F_Air Quality Index Reporting

Sec. 58.50  Index reporting.

    (a) The State shall report to the general public through prominent 
notice an air quality index in accordance with the requirements of 
appendix G to this part.
    (b) Reporting is required by all Metropolitan Statistical Areas with 
a population exceeding 350,000.
    (c) The population of a Metropolitan Statistical Area for purposes 
of index reporting is the most recent decennial U.S. census population.

[64 FR 42547, Aug. 4, 1999]

                      Subpart G_Federal Monitoring

    Source: 44 FR 27571, May 10, 1979. Redesignated at 58 FR 8467, Feb. 
12, 1993.

Sec. 58.60  Federal monitoring.

    The Administrator may locate and operate an ambient air monitoring 
station if the State fails to locate, or schedule to be located, during 
the initial network design process or as a result of the annual review 
required by Sec. 58.20(d):
    (a) A SLAMS at a site which is necessary in the judgment of the 
Regional Administrator to meet the objectives defined in appendix D to 
this part, or
    (b) A NAMS at a site which is necessary in the judgment of the 
Administrator for meeting EPA national data needs.

Sec. 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 a 
National Ambient Air Quality Standard 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.

  Appendix A to Part 58--Quality Assurance Requirements for State and 
                  Local Air Monitoring Stations (SLAMS)

1. General Information.
    1.1 This appendix specifies the minimum quality assurance/quality 
control (QA/QC) requirements applicable to SLAMS air monitoring data 
submitted to EPA. State and local agencies are encouraged to develop and 
maintain quality assurance programs more extensive than the required 
minimum.
    1.2 To assure the quality of data from air monitoring measurements, 
two distinct and important interrelated functions must be performed. One 
function is the control of the measurement process through broad quality 
assurance activities, such as establishing policies and procedures, 
developing data quality objectives, assigning roles and 
responsibilities, conducting oversight and reviews, and implementing 
corrective actions. The other function is the control of the measurement 
process through the implementation of specific quality control 
procedures, such as audits, calibrations, checks, replicates, routine 
self-assessments, etc. In general, the greater the control of a given 
monitoring system, the better will be the resulting quality of the 
monitoring data. The results of quality assurance reviews and 
assessments indicate whether the control efforts are adequate or need to 
be improved.
    1.3 Documentation of all quality assurance and quality control 
efforts implemented during the data collection, analysis, and reporting 
phases is important to data users, who can then consider the impact of 
these control efforts on the data quality (see reference 1 of this 
appendix). Both qualitative and quantitative assessments of the 
effectiveness of these control efforts should identify those areas most 
likely to impact the data quality and to what extent.
    1.4 Periodic assessments of SLAMS data quality are required to be 
reported to EPA. To provide national uniformity in this assessment and 
reporting of data quality for all SLAMS networks, specific assessment

[[Page 219]]

and reporting procedures are prescribed in detail in sections 3, 4, and 
5 of this appendix. On the other hand, the selection and extent of the 
QA and QC activities used by a monitoring agency depend on a number of 
local factors such as the field and laboratory conditions, the 
objectives for monitoring, the level of the data quality needed, the 
expertise of assigned personnel, the cost of control procedures, 
pollutant concentration levels, etc. Therefore, the quality system 
requirements, in section 2 of this appendix, are specified in general 
terms to allow each State to develop a quality assurance program that is 
most efficient and effective for its own circumstances while achieving 
the Ambient Air Quality Programs data quality objectives.
2. Quality System Requirements.
    2.1 Each State and local agency must develop a quality system 
(reference 2 of this appendix) to ensure that the monitoring results:
    (a) Meet a well-defined need, use, or purpose.
    (b) Satisfy customers' expectations.
    (c) Comply with applicable standards specifications.
    (d) Comply with statutory (and other) requirements of society.
    (e) Reflect consideration of cost and economics.
    (f) Implement a quality assurance program consisting of policies, 
procedures, specifications, standards, and documentation necessary to:
    (1) Provide data of adequate quality to meet monitoring objectives, 
and
    (2) Minimize loss of air quality data due to malfunctions or out-of-
control conditions. This quality assurance program must be described in 
detail, suitably documented in accordance with Agency requirements 
(reference 4 of this appendix), and approved by the appropriate Regional 
Administrator, or the Regional Administrator's designee. The Quality 
Assurance Program will be reviewed during the systems audits described 
in section 2.5 of this appendix.
    2.2 Primary requirements and guidance documents for developing the 
quality assurance program are contained in references 2 through 7 of 
this appendix, which also contain many suggested and required 
procedures, checks, and control specifications. Reference 7 of this 
appendix describes specific guidance for the development of a QA Program 
for SLAMS. Many specific quality control checks and specifications for 
methods are included in the respective reference methods described in 
part 50 of this chapter or in the respective equivalent method 
descriptions available from EPA (reference 8 of this appendix). 
Similarly, quality control procedures related to specifically designated 
reference and equivalent method analyzers are contained in the 
respective operation or instruction manuals associated with those 
analyzers. Quality assurance guidance for meteorological systems at PAMS 
is contained in reference 9 of this appendix. Quality assurance 
procedures for VOC, NO<INF>X</INF> (including NO and NO<INF>2</INF>), 
O<INF>3</INF>, and carbonyl measurements at PAMS must be consistent with 
reference 15 of this appendix. Reference 4 of this appendix includes 
requirements for the development of quality assurance project plans, and 
quality assurance and control programs, and systems audits demonstrating 
attainment of the requirements.
    2.3 Pollutant Concentration and Flow Rate Standards.
    2.3.1 Gaseous pollutant concentration standards (permeation devices 
or cylinders of compressed gas) used to obtain test concentrations for 
CO, SO<INF>2</INF>, NO, and NO<INF>2</INF> must be traceable to either a 
National Institute of Standards and Technology (NIST) NIST-Traceable 
Reference Material (NTRM) or a NIST-certified Gas Manufacturer's 
Internal Standard (GMIS), certified in accordance with one of the 
procedures given in reference 10 of this appendix.
    2.3.2 Test concentrations for O<INF>3</INF> must be obtained in 
accordance with the UV photometric calibration procedure specified in 40 
CFR part 50, appendix D, or by means of a certified ozone transfer 
standard. Consult references 11 and 12 of this appendix for guidance on 
primary and transfer standards for O<INF>3</INF>.
    2.3.3 Flow rate measurements must be made by a flow measuring 
instrument that is traceable to an authoritative volume or other 
applicable standard. Guidance for certifying some types of flowmeters is 
provided in reference 7 of this appendix.
    2.4 National Performance Audit Program (NPAP). Agencies operating 
SLAMS are required to participate in EPA's NPAP. These audits are 
described in reference 7 of this appendix. For further instructions, 
agencies should contact either the appropriate EPA Regional QA 
Coordinator at the appropriate EPA Regional Office location, or the NPAP 
Coordinator, Emissions Monitoring and Analysis Division (MD-14), U.S. 
Environmental Protection Agency, Research Triangle Park, NC 27711.
    2.5 Systems Audit Programs. Systems audits of the ambient air 
monitoring programs of agencies operating SLAMS shall be conducted at 
least every 3 years by the appropriate EPA Regional Office. Systems 
audit programs are described in reference 7 of this appendix. For 
further instructions, agencies should contact either the appropriate EPA 
Regional QA Coordinator or the Systems Audit QA Coordinator, Office of 
Air Quality Planning and Standards, Emissions Monitoring and Analysis 
Division (MD-14), U.S. Environmental Protection Agency, Research 
Triangle Park, NC 27711.
3. Data Quality Assessment Requirements.

[[Page 220]]

    3.0.1 All ambient monitoring methods or analyzers used in SLAMS 
shall be tested periodically, as described in this section, to 
quantitatively assess the quality of the SLAMS data. Measurement 
uncertainty is estimated for both automated and manual methods. 
Terminology associated with measurement uncertainty are found within 
this appendix and includes:
    (a) Precision. A measurement of mutual agreement among individual 
measurements of the same property usually under prescribed similar 
conditions, expressed generally in terms of the standard deviation;
    (b) Accuracy. The degree of agreement between an observed value and 
an accepted reference value, accuracy includes a combination of random 
error (precision) and systematic error (bias) components which are due 
to sampling and analytical operations;
    (c) Bias. The systematic or persistent distortion of a measurement 
process which causes errors in one direction. The individual results of 
these tests for each method or analyzer shall be reported to EPA as 
specified in section 4 of this appendix. EPA will then calculate 
quarterly assessments of measurement uncertainty applicable to the SLAMS 
data as described in section 5 of this appendix. Data assessment results 
should be reported to EPA only for methods and analyzers approved for 
use in SLAMS monitoring under appendix C of this part.
    3.0.2 Estimates of the data quality will be calculated on the basis 
of single monitors and reporting organizations and may also be 
calculated for each region and for the entire Nation. A reporting 
organization is defined as a State, subordinate organization within a 
State, or other organization that is responsible for a set of stations 
that monitors the same pollutant and for which data quality assessments 
can be pooled. States must define one or more reporting organizations 
for each pollutant such that each monitoring station in the State SLAMS 
network is included in one, and only one, reporting organization.
    3.0.3 Each reporting organization 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) Common factors that should be considered by States in defining 
reporting organizations include:
    (1) Operation by a common team of field operators.
    (2) Common calibration facilities.
    (3) Oversight by a common quality assurance organization.
    (4) Support by a common laboratory or headquarters.
    (b) Where there is uncertainty in defining the reporting 
organizations or in assigning specific sites to reporting organizations, 
States shall consult with the appropriate EPA Regional Office. All 
definitions of reporting organizations shall be subject to final 
approval by the appropriate EPA Regional Office.
    3.0.4 Assessment results shall be reported as specified in section 4 
of this appendix. Table A-1 of this appendix provides a summary of the 
minimum data quality assessment requirements, which are described in 
more detail in the following sections.
    3.1 Precision of Automated Methods Excluding PM<INF>2.5</INF>.
    3.1.1 Methods for SO<INF>2</INF>, NO<INF>2</INF>, O<INF>3</INF> and 
CO. A one- point precision check must be performed at least once every 2 
weeks on each automated analyzer used to measure SO<INF>2</INF>, 
NO<INF>2</INF>, O<INF>3</INF> and CO. The precision check is made by 
challenging the analyzer with a precision check gas of known 
concentration (effective concentration for open path analyzers) between 
0.08 and 0.10 ppm for SO<INF>2</INF>, NO<INF>2</INF>, and O<INF>3</INF> 
analyzers, and between 8 and 10 ppm for CO analyzers. To check the 
precision of SLAMS analyzers operating on ranges higher than 0 to 1.0 
ppm SO<INF>2</INF>, NO<INF>2</INF>, and O<INF>3</INF>, or 0 to 100 ppm 
for CO, use precision check gases of appropriately higher concentration 
as approved by the appropriate Regional Administrator or their designee. 
However, the results of precision checks at concentration levels other 
than those specified above need not be reported to EPA. The standards 
from which precision check test concentrations are obtained must meet 
the specifications of section 2.3 of this appendix.
    3.1.1.1 Except for certain CO analyzers described below, point 
analyzers must operate in their normal sampling mode during the 
precision 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. 
If permitted by the associated operation or instruction manual, a CO 
point analyzer may be temporarily modified during the precision check to 
reduce vent or purge flows, or the test atmosphere may enter the 
analyzer at a point other than the normal sample inlet, provided that 
the analyzer's response is not likely to be altered by these deviations 
from the normal operational mode. If a precision check is made in 
conjunction with a zero or span adjustment, it must be made prior to 
such zero or span adjustments. Randomization of the precision check with 
respect to time of day, day of week, and routine service and adjustments 
is encouraged where possible.
    3.1.1.2 Open path analyzers are tested by inserting a test cell 
containing a precision check gas concentration into the optical 
measurement beam of the instrument. If possible, the normally used 
transmitter, receiver, and as appropriate, reflecting devices

[[Page 221]]

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 precision 
check gas in the test cell must be selected to produce an effective 
concentration in the range specified in section 3.1.1. Generally, the 
precision test concentration measurement will be the sum of the 
atmospheric pollutant concentration and the precision test 
concentration. If so, 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 precision check test from the precision test 
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 analyzers should be tested during periods 
when the atmospheric pollutant concentrations are relatively low and 
steady.
    3.1.1.3 Report the actual concentration (effective concentration for 
open path analyzers) of the precision check gas and the corresponding 
concentration measurement (corrected concentration, if applicable, for 
open path analyzers) indicated by the analyzer. The percent differences 
between these concentrations are used to assess the precision of the 
monitoring data as described in section 5.1. of this appendix.
    3.1.2 Methods for Particulate Matter Excluding PM<INF>2.5</INF>. A 
one-point precision check must be performed at least once every 2 weeks 
on each automated analyzer used to measure PM<INF>10</INF>. The 
precision check is made by checking the operational flow rate of the 
analyzer. If a precision flow rate check is made in conjunction with a 
flow rate adjustment, it must be made prior to such flow rate 
adjustment. Randomization of the precision check with respect to time of 
day, day of week, and routine service and adjustments is encouraged 
where possible.
    3.1.2.1 Standard procedure: Use a flow rate transfer standard 
certified in accordance with section 2.3.3 of this appendix to check the 
analyzer's normal flow rate. Care should be used in selecting and using 
the flow rate measurement device such that it does not alter the normal 
operating flow rate of the analyzer. Report the actual analyzer flow 
rate measured by the transfer standard and the corresponding flow rate 
measured, indicated, or assumed by the analyzer.
    3.1.2.2 Alternative procedure:
    3.1.2.2.1 It is permissible to obtain the precision check flow rate 
data from the analyzer's internal flow meter without the use of an 
external flow rate transfer standard, provided that:
    3.1.2.2.1.1 The flow meter is audited with an external flow rate 
transfer standard at least every 6 months.
    3.1.2.2.1.2 Records of at least the three most recent flow audits of 
the instrument's internal flow meter over at least several weeks confirm 
that the flow meter is stable, verifiable and accurate to <plus-
minus<ls-thn-eq>4%.
    3.1.2.2.1.3 The instrument and flow meter give no indication of 
improper operation.
    3.1.2.2.2 With suitable communication capability, the precision 
check may thus be carried out remotely. For this procedure, report the 
set-point flow rate as the actual flow rate along with the flow rate 
measured or indicated by the analyzer flow meter.
    3.1.2.2.3 For either procedure, the percent differences between the 
actual and indicated flow rates are used to assess the precision of the 
monitoring data as described in section 5.1 of this appendix (using flow 
rates in lieu of concentrations). The percent differences between these 
concentrations are used to assess the precision of the monitoring data 
as described in section 5.1. of this appendix.
    3.2 Accuracy of Automated Methods Excluding PM<INF>2.5</INF>.
    3.2.1 Methods for SO<INF>2</INF>, NO<INF>2</INF>, O<INF>3</INF>, or 
CO.
    3.2.1.1 Each calendar quarter (during which analyzers are operated), 
audit at least 25 percent of the SLAMS analyzers that monitor for 
SO<INF>2</INF>, NO<INF>2</INF>, O<INF>3</INF>, or CO such that each 
analyzer is audited at least once per year. If there are fewer than four 
analyzers for a pollutant within a reporting organization, randomly 
reaudit one or more analyzers so that at least one analyzer for that 
pollutant is audited each calendar quarter. Where possible, EPA strongly 
encourages more frequent auditing, up to an audit frequency of once per 
quarter for each SLAMS analyzer.
    3.2.1.2 (a) The audit is made by challenging the analyzer with at 
least one audit gas of known concentration (effective concentration for 
open path analyzers) from each of the following ranges applicable to the 
analyzer being audited:

------------------------------------------------------------------------
                                          Concentration Range, PPM
            Audit Level           --------------------------------------
                                     SO2, O3        NO2           CO
------------------------------------------------------------------------
1................................    0.03-0.08    0.03-0.08          3-8
2................................    0.15-0.20    0.15-0.20        15-20
3................................    0.35-0.45    0.35-0.45        35-45
4................................    0.80-0.90  ...........        80-90
------------------------------------------------------------------------

    (b) NO<INF>2</INF> audit gas for chemiluminescence-type 
NO<INF>2</INF> analyzers must also contain at least 0.08 ppm NO.
    3.2.1.3 NO concentrations substantially higher than 0.08 ppm, as may 
occur when

[[Page 222]]

using some gas phase titration (GPT) techniques, may lead to audit 
errors in chemiluminescence analyzers due to inevitable minor NO-
NO<INF>X</INF> channel imbalance. Such errors may be atypical of routine 
monitoring errors to the extent that such NO concentrations exceed 
typical ambient NO concentrations at the site. These errors may be 
minimized by modifying the GPT technique to lower the NO concentrations 
remaining in the NO<INF>2</INF> audit gas to levels closer to typical 
ambient NO concentrations at the site.
    3.2.1.4 To audit SLAMS analyzers operating on ranges higher than 0 
to 1.0 ppm for SO<INF>2</INF>, NO<INF>2</INF>, and O<INF>3</INF> or 0 to 
100 ppm for CO, use audit gases of appropriately higher concentration as 
approved by the appropriate Regional Administrator or the 
Administrators's designee. The results of audits at concentration levels 
other than those shown in the above table need not be reported to EPA.
    3.2.1.5 The standards from which audit gas test concentrations are 
obtained must meet the specifications of section 2.3 of this appendix. 
The gas standards and equipment used for auditing must not be the same 
as the standards and equipment used for calibration or calibration span 
adjustments. The auditor should not be the operator or analyst who 
conducts the routine monitoring, calibration, and analysis.
    3.2.1.6 For point analyzers, the audit shall be carried out by 
allowing the analyzer to analyze the audit 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. The exception provided in section 3.1 of this appendix 
for certain CO analyzers does not apply for audits.
    3.2.1.7 Open path analyzers are audited 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 audit, and the normal monitoring configuration of the 
instrument should be modified as little as possible to accommodate the 
test cell for the audit. 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 ranges specified in this section 3.2 of this appendix. Generally, 
each audit concentration measurement result will be the sum of the 
atmospheric pollutant concentration and the audit test concentration. If 
so, 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 audit 
test (or preferably before and after each audit concentration level) 
from the audit 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 analyzers should be audited during periods when 
the atmospheric pollutant concentrations are relatively low and steady. 
Also, the monitoring path length must be reverified to within <plus-
minus<ls-thn-eq>3 percent to validate the audit, since the monitoring 
path length is critical to the determination of the effective 
concentration.
    3.2.1.8 Report both the actual concentrations (effective 
concentrations for open path analyzers) of the audit gases and the 
corresponding concentration measurements (corrected concentrations, if 
applicable, for open path analyzers) indicated or produced by the 
analyzer being tested. The percent differences between these 
concentrations are used to assess the accuracy of the monitoring data as 
described in section 5.2 of this appendix.
    3.2.2 Methods for Particulate Matter Excluding PM<INF>2.5</INF>.
    3.2.2.1 Each calendar quarter, audit the flow rate of at least 25 
percent of the SLAMS PM<INF>10</INF> analyzers such that each 
PM<INF>10</INF> analyzer is audited at least once per year. If there are 
fewer than four PM<INF>10</INF> analyzers within a reporting 
organization, randomly re-audit one or more analyzers so that at least 
one analyzer is audited each calendar quarter. Where possible, EPA 
strongly encourages more frequent auditing, up to an audit frequency of 
once per quarter for each SLAMS analyzer.
    3.2.2.2 The audit is made by measuring the analyzer's normal 
operating flow rate, using a flow rate transfer standard certified in 
accordance with section 2.3.3 of this appendix. The flow rate standard 
used for auditing must not be the same flow rate standard used to 
calibrate the analyzer. However, both the calibration standard and the 
audit standard may be referenced to the same primary flow rate or volume 
standard. Great care must be used in auditing the flow rate to be 
certain that the flow measurement device does not alter the normal 
operating flow rate of the analyzer. Report the audit (actual) flow rate 
and the corresponding flow rate indicated or assumed by the sampler. The 
percent differences between these flow rates are used to calculate 
accuracy (PM<INF>10</INF>) as described in section 5.2 of this appendix.
    3.3 Precision of Manual Methods Excluding PM<INF>2.5</INF>.

[[Page 223]]

    3.3.1 For each network of manual methods other than for 
PM<INF>2.5</INF>, select one or more monitoring sites within the 
reporting organization for duplicate, collocated sampling as follows: 
for 1 to 5 sites, select 1 site; for 6 to 20 sites, select 2 sites; and 
for over 20 sites, select 3 sites. Where possible, additional collocated 
sampling is encouraged. For purposes of precision assessment, networks 
for measuring TSP and PM<INF>10</INF> shall be considered separately 
from one another. PM<INF>10</INF> and TSP sites having annual mean 
particulate matter concentrations among the highest 25 percent of the 
annual mean concentrations for all the sites in the network must be 
selected or, if such sites are impractical, alternative sites approved 
by the Regional Administrator may be selected.
    3.3.2 In determining the number of collocated sites required for 
PM<INF>10</INF>, monitoring networks for lead should be treated 
independently from networks for particulate matter, even though the 
separate networks may share one or more common samplers. However, a 
single pair of samplers collocated at a common-sampler monitoring site 
that meets the requirements for both a collocated lead site and a 
collocated particulate matter site may serve as a collocated site for 
both networks.
    3.3.3 The two collocated samplers must be within 4 meters of each 
other, and particulate matter samplers must be at least 2 meters apart 
to preclude airflow interference. Calibration, sampling, and analysis 
must be the same for both collocated samplers and the same as for all 
other samplers in the network.
    3.3.4 For each pair of collocated samplers, designate one sampler as 
the primary sampler whose samples will be used to report air quality for 
the site, and designate the other as the duplicate sampler. Each 
duplicate sampler must be operated concurrently with its associated 
routine sampler at least once per week. The operation schedule should be 
selected so that the sampling days are distributed evenly over the year 
and over the seven days of the week. A six-day sampling schedule is 
required. Report the measurements from both samplers at each collocated 
sampling site. The calculations for evaluating precision between the two 
collocated samplers are described in section 5.3 of this appendix.
    3.4 Accuracy of Manual Methods Excluding PM<INF>2.5</INF>. The 
accuracy of manual sampling methods is assessed by auditing a portion of 
the measurement process.
    3.4.1 Procedures for PM<INF>10</INF> and TSP.
    3.4.1.1 Procedures for flow rate audits for PM<INF>10</INF>. Each 
calendar quarter, audit the flow rate of at least 25 percent of the 
PM<INF>10</INF> samplers such that each PM<INF>10</INF> sampler is 
audited at least once per year. If there are fewer than four 
PM<INF>10</INF> samplers within a reporting organization, randomly 
reaudit one or more samplers so that one sampler is audited each 
calendar quarter. Audit each sampler at its normal operating flow rate, 
using a flow rate transfer standard certified in accordance with section 
2.3.3 of this appendix. The flow rate standard used for auditing must 
not be the same flow rate standard used to calibrate the sampler. 
However, both the calibration standard and the audit standard may be 
referenced to the same primary flow rate standard. The flow audit should 
be scheduled so as to avoid interference with a scheduled sampling 
period. Report the audit (actual) flow rate and the corresponding flow 
rate indicated by the sampler's normally used flow indicator. The 
percent differences between these flow rates are used to calculate 
accuracy and bias as described in section 5.4.1 of this appendix.
    3.4.1.2 Great care must be used in auditing high-volume particulate 
matter samplers having flow regulators because the introduction of 
resistance plates in the audit flow standard device can cause abnormal 
flow patterns at the point of flow sensing. For this reason, the flow 
audit standard should be used with a normal filter in place and without 
resistance plates in auditing flow-regulated high-volume samplers, or 
other steps should be taken to assure that flow patterns are not 
perturbed at the point of flow sensing.
    3.4.2 SO<INF>2</INF> Methods.
    3.4.2.1 Prepare audit solutions from a working sulfite-
tetrachloromercurate (TCM) solution as described in section 10.2 of the 
SO<INF>2</INF> Reference Method (40 CFR part 50, appendix A). These 
audit samples must be prepared independently from the standardized 
sulfite solutions used in the routine calibration procedure. Sulfite-TCM 
audit samples must be stored between 0 and 5 [deg]C and expire 30 days 
after preparation.
    3.4.2.2 Prepare audit samples in each of the concentration ranges of 
0.2-0.3, 0.5-0.6, and 0.8-0.9 [mu]g SO<INF>2</INF>/ml. Analyze an audit 
sample in each of the three ranges at least once each day that samples 
are analyzed and at least twice per calendar quarter. Report the audit 
concentrations (in [mu]g SO<INF>2</INF>/ml) and the corresponding 
indicated concentrations (in [mu]g SO<INF>2</INF>/ml). The percent 
differences between these concentrations are used to calculate accuracy 
as described in section 5.4.2 of this appendix.
    3.4.3 NO<INF>2</INF> Methods. Prepare audit solutions from a working 
sodium nitrite solution as described in the appropriate equivalent 
method (see reference 8 of this appendix). These audit samples must be 
prepared independently from the standardized nitrite solutions used in 
the routine calibration procedure. Sodium nitrite audit samples expire 
in 3 months after preparation. Prepare audit samples in each of the 
concentration ranges of 0.2-0.3, 0.5-0.6, and 0.8-0.9 [mu]g 
NO<INF>2</INF>/ml. Analyze an audit sample in each of the three

[[Page 224]]

ranges at least once each day that samples are analyzed and at least 
twice per calendar quarter. Report the audit concentrations (in [mu]g 
NO<INF>2</INF>/ml) and the corresponding indicated concentrations (in 
[mu]g NO<INF>2</INF>/ml). The percent differences between these 
concentrations are used to calculate accuracy as described in section 
5.4.2 of this appendix.
    3.4.4 Pb Methods.
    3.4.4.1 For the Pb Reference Method (40 CFR part 50, appendix G), 
the flow rates of the high-volume Pb samplers shall be audited as part 
of the TSP network using the same procedures described in section 3.4.1 
of this appendix. For agencies operating both TSP and Pb networks, 25 
percent of the total number of high-volume samplers are to be audited 
each quarter.
    3.4.4.2 Each calendar quarter, audit the Pb Reference Method 
analytical procedure using glass fiber filter strips containing a known 
quantity of Pb. These audit sample strips are prepared by depositing a 
Pb solution on unexposed glass fiber filter strips of dimensions 1.9 cm 
by 20.3 cm (3/4 inch by 8 inch) and allowing them to dry thoroughly. The 
audit samples must be prepared using batches of reagents different from 
those used to calibrate the Pb analytical equipment being audited. 
Prepare audit samples in the following concentration ranges:

------------------------------------------------------------------------
                                                           Equivalent
                                             Pb            Ambient Pb
                Range                  Concentration,    Concentration,
                                         [mu]g/Strip      [mu]g/m3 \1\
------------------------------------------------------------------------
1...................................           100-300           0.5-1.5
2...................................          600-1000           3.0-5.0
------------------------------------------------------------------------
\1\ Equivalent ambient Pb concentration in [mu]g/m3 is based on sampling
  at 1.7 m3/min for 24 hours on a 20.3 cmx25.4 cm (8 inchx10 inch) glass
  fiber filter.

    3.4.4.3 Audit samples must be extracted using the same extraction 
procedure used for exposed filters.
    3.4.4.4 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. Report 
the audit concentrations (in [mu]g Pb/strip) and the corresponding 
measured concentrations (in [mu]g Pb/strip) using unit code 77. The 
percent differences between the concentrations are used to calculate 
analytical accuracy as described in section 5.4.2 of this appendix.
    3.4.4.5 The accuracy of an equivalent Pb method is assessed in the 
same manner as for the reference method. The flow auditing device and Pb 
analysis audit samples must be compatible with the specific requirements 
of the equivalent method.
    3.5 Measurement Uncertainty for Automated and Manual 
PM<INF>2.5</INF> Methods. The goal for acceptable measurement 
uncertainty has been defined as 10 percent coefficient of variation (CV) 
for total precision and <plus-minus<ls-thn-eq> 10 percent for total bias 
(reference 14 of this appendix).
    3.5.1 Flow Rate Audits.
    3.5.1.1 Automated methods for PM<INF>2.5</INF>. A one-point 
precision check must be performed at least once every 2 weeks on each 
automated analyzer used to measure PM<INF>2.5</INF>. The precision check 
is made by checking the operational flow rate of the analyzer. If a 
precision flow rate check is made in conjunction with a flow rate 
adjustment, it must be made prior to such flow rate adjustment. 
Randomization of the precision check with respect to time of day, day of 
week, and routine service and adjustments is encouraged where possible.
    3.5.1.1.1 Standard procedure: Use a flow rate transfer standard 
certified in accordance with section 2.3.3 of this appendix to check the 
analyzer's normal flow rate. Care should be used in selecting and using 
the flow rate measurement device such that it does not alter the normal 
operating flow rate of the analyzer. Report the actual analyzer flow 
rate measured by the transfer standard and the corresponding flow rate 
measured, indicated, or assumed by the analyzer.
    3.5.1.1.2 Alternative procedure: It is permissible to obtain the 
precision check flow rate data from the analyzer's internal flow meter 
without the use of an external flow rate transfer standard, provided 
that the flow meter is audited with an external flow rate transfer 
standard at least every 6 months; records of at least the three most 
recent flow audits of the instrument's internal flow meter over at least 
several weeks confirm that the flow meter is stable, verifiable and 
accurate to <plus-minus<ls-thn-eq>4%; and the instrument and flow meter 
give no indication of improper operation. With suitable communication 
capability, the precision check may thus be carried out remotely. For 
this procedure, report the set-point flow rate as the actual flow rate 
along with the flow rate measured or indicated by the analyzer flow 
meter.
    3.5.1.1.3 For either procedure, the differences between the actual 
and indicated flow rates are used to assess the precision of the 
monitoring data as described in section 5.5 of this appendix.
    3.5.1.2 Manual methods for PM<INF>2.5</INF>. Each calendar quarter, 
audit the flow rate of each SLAMS PM<INF>2.5</INF> analyzer. The audit 
is made by measuring the analyzer's normal operating flow rate, using a 
flow rate transfer standard certified in accordance with section 2.3.3 
of this appendix. The flow rate standard used for auditing must not be 
the same flow rate standard used to calibrate the analyzer. However, 
both the calibration standard and the audit standard may be referenced 
to the same primary flow rate or volume standard. Great care must be 
used in auditing the flow rate to be certain that the flow measurement 
device does not alter the normal operating flow rate of the analyzer. 
Report the audit

[[Page 225]]

(actual) flow rate and the corresponding flow rate indicated or assumed 
by the sampler. The procedures used to calculate measurement uncertainty 
PM<INF>2.5</INF> are described in section 5.5 of this appendix.
    3.5.2 Measurement of Precision using Collocated Procedures for 
Automated and Manual Methods of PM<INF>2.5</INF>.
    (a) For PM<INF>2.5</INF> sites within a reporting organization each 
EPA designated Federal reference method (FRM) or Federal equivalent 
method (FEM) must:
    (1) Have 15 percent of the monitors collocated (values of .5 and 
greater round up).
    (2) Have at least 1 collocated monitor (if the total number of 
monitors is less than 4). The first collocated monitor must be a 
designated FRM monitor.
    (b) In addition, monitors selected must also meet the following 
requirements:
    (1) A monitor designated as an EPA FRM shall be collocated with a 
monitor having the same EPA FRM designation.
    (2) For each monitor designated as an EPA FEM, 50 percent of the 
designated monitors shall be collocated with a monitor having the same 
method designation and 50 percent of the monitors shall be collocated 
with an FRM monitor. If there are an odd number of collocated monitors 
required, the additional monitor shall be an FRM. An example of this 
procedure is found in table A-2 of this appendix.
    (c) For PM<INF>2.5</INF> sites during the initial deployment of the 
SLAMS network, special emphasis should be placed on those sites in areas 
likely to be in violation of the NAAQS. Once areas are initially 
determined to be in violation, the collocated monitors should be 
deployed according to the following protocol:
    (1) Eighty percent of the collocated monitors should be deployed at 
sites with concentrations <ls-thn-eq>= ninety percent of the annual 
PM<INF>2.5</INF> NAAQS (or 24-hour NAAQS if that is affecting the area); 
one hundred percent if all sites have concentrations above either NAAQS, 
and each area determined to be in violation should be represented by at 
least one collocated monitor.
    (2) The remaining 20 percent of the collocated monitors should be 
deployed at sites with concentrations < ninety percent of the annual 
PM<INF>2.5</INF> NAAQS (or 24-hour NAAQS if that is affecting the area)
    (3) If an organization has no sites at concentration ranges 
<ls-thn-eq>= ninety percent of the annual PM<INF>2.5</INF> NAAQS (or 24-
hour NAAQS if that is affecting the area), 60 percent of the collocated 
monitors should be deployed at those sites with the annual mean 
PM<INF>2.5</INF> concentrations (or 24-hour NAAQS if that is affecting 
the area) among the highest 25 percent for all PM<INF>2.5</INF> sites in 
the network.
    3.5.2.1 In determining the number of collocated sites required for 
PM<INF>2.5</INF>, monitoring networks for visibility should not be 
treated independently from networks for particulate matter, as the 
separate networks may share one or more common samplers. However, for 
class I visibility areas, EPA will accept visibility aerosol mass 
measurement instead of a PM<INF>2.5</INF> measurement if the latter 
measurement is unavailable. Any PM<INF>2.5</INF> monitoring site which 
does not have a monitor which is an EPA federal reference or equivalent 
method is not required to be included in the number of sites which are 
used to determine the number of collocated monitors.
    3.5.2.2 The two collocated samples must be within 4 meters of each 
other, and particulate matter samplers must be at least 2 meters apart 
(1 meter apart for samplers having flow rates less than 200 liters/min.) 
to preclude airflow interference. Calibration, sampling, and analysis 
must be the same for both collocated samplers and the same as for all 
other samplers in the network.
    3.5.2.3 For each pair of collocated samplers, designate one sampler 
as the primary sampler whose samples will be used to report air quality 
for the site, and designate the other as the duplicate sampler. Each 
duplicate sampler must be operated concurrently with its associated 
primary sampler. The operation schedule should be selected so that the 
sampling days are distributed evenly over the year and over the 7 days 
of the week and therefore, a 6-day sampling schedule is required. Report 
the measurements from both samplers at each collocated sampling site. 
The calculations for evaluating precision between the two collocated 
samplers are described in section 5.5 of this appendix.
    3.5.3 Measurement of Bias using the FRM Audit Procedures for 
Automated and Manual Methods of PM<INF>2.5</INF>.
    3.5.3.1 The FRM audit is an independent assessment of the total 
measurement system bias. These audits will be performed under the 
National Performance Audit Program (section 2.4 of this appendix) or a 
comparable program. Twenty-five percent of the SLAMS monitors within 
each reporting organization will be assessed with an FRM audit each 
year. Additionally, every designated FRM or FEM within a reporting 
organization must:
    (a) Have at least 25 percent of each method designation audited, 
including collocated sites (even those collocated with FRM instruments), 
(values of .5 and greater round up).
    (b) Have at least one monitor audited.
    (c) Be audited at a frequency of four audits per year.
    (d) Have all FRM or FEM samplers subject to an FRM audit at least 
once every 4 years. Table A-2 illustrates the procedure mentioned above.
    3.5.3.2 For PM<INF>2.5</INF> sites during the initial deployment of 
the SLAMS network, special emphasis should be placed on those sites in 
areas likely to be in violation of the NAAQS. Once areas are initially 
determined to be in violation, the FRM audit program should be

[[Page 226]]

implemented according to the following protocol:
    (a) Eighty percent of the FRM audits should be deployed at sites 
with concentrations <ls-thn-eq>= ninety percent of the annual 
PM<INF>2.5</INF> NAAQS (or 24-hour NAAQS if that is affecting the area); 
one hundred percent if all sites have concentrations above either NAAQS, 
and each area determined to be in violation should implement an FRM 
audit at a minimum of one monitor within that area.
    (b) The remaining 20 percent of the FRM audits should be implemented 
at sites with concentrations < ninety percent of the annual 
PM<INF>2.5</INF> NAAQS (or 24-hour NAAQS if that is affecting the area).
    (c) If an organization has no sites at concentration ranges 
<ls-thn-eq>= ninety percent of the annual PM<INF>2.5</INF> NAAQS (or 24-
hour NAAQS if that is affecting the area), 60 percent of the FRM audits 
should be implemented at those sites with the annual mean 
PM<INF>2.5</INF> concentrations (or 24-hour NAAQS if that is affecting 
the area) among the highest 25 percent for all PM<INF>2.5</INF> sites in 
the network. Additional information concerning the FRM audit program is 
contained in reference 7 of this appendix. The calculations for 
evaluating bias between the primary monitor and the FRM audit are 
described in section 5.5.
4. Reporting Requirements.
    (a) For each pollutant, prepare a list of all monitoring sites and 
their AIRS site identification codes in each reporting organization and 
submit the list to the appropriate EPA Regional Office, with a copy to 
AIRS-AQS. Whenever there is a change in this list of monitoring sites in 
a reporting organization, report this change to the Regional Office and 
to AIRS-AQS.
    4.1 Quarterly Reports. For each quarter, each reporting organization 
shall report to AIRS-AQS directly (or via the appropriate EPA Regional 
Office for organizations not direct users of AIRS) the results of all 
valid precision, bias and accuracy tests it has carried out during the 
quarter. The quarterly reports of precision, bias and accuracy data must 
be submitted consistent with the data reporting requirements specified 
for air quality data as set forth in Sec. 58.35(c). EPA strongly 
encourages early submittal of the QA data in order to assist the State 
and Local agencies in controlling and evaluating the quality of the 
ambient air SLAMS data. Each organization shall report all QA/QC 
measurements. Report results from invalid tests, from tests carried out 
during a time period for which ambient data immediately prior or 
subsequent to the tests were invalidated for appropriate reasons, and 
from tests of methods or analyzers not approved for use in SLAMS 
monitoring networks under appendix C of this part. Such data should be 
flagged so that it will not be utilized for quantitative assessment of 
precision, bias and accuracy.
    4.2 Annual Reports.
    4.2.1 When precision, bias and accuracy estimates for a reporting 
organization have been calculated for all four quarters of the calendar 
year, EPA will calculate and report the measurement uncertainty for the 
entire calendar year. These limits will then be associated with the data 
submitted in the annual SLAMS report required by Sec. 58.26.
    4.2.2 Each reporting organization shall submit, along with its 
annual SLAMS report, a listing by pollutant of all monitoring sites in 
the reporting organization.
5. Calculations for Data Quality Assessment.
    (a) Calculations of measurement uncertainty are carried out by EPA 
according to the following procedures. Reporting organizations should 
report the data for individual precision, bias and accuracy tests as 
specified in sections 3 and 4 of this appendix even though they may 
elect to perform some or all of the calculations in this section on 
their own.
    5.1 Precision of Automated Methods Excluding PM<INF>2.5</INF>. 
Estimates of the precision of automated methods are calculated from the 
results of biweekly precision checks as specified in section 3.1 of this 
appendix. At the end of each calendar quarter, an integrated precision 
probability interval for all SLAMS analyzers in the organization is 
calculated for each pollutant.
    5.1.1 Single Analyzer Precision.
    5.1.1.1 The percent difference (d<INF>i</INF>) for each precision 
check is calculated using equation 1, where Y<INF>i</INF> is the 
concentration indicated by the analyzer for the I-th precision check and 
X<INF>i</INF> is the known concentration for the I-th precision check, 
as follows:
                               Equation 1
[GRAPHIC] [TIFF OMITTED] TR18JY97.138

    5.1.1.2 For each analyzer, the quarterly average (d<INF>j</INF>) is 
calculated with equation 2, and the standard deviation (S<INF>j</INF>) 
with equation 3, where n is the number of precision checks on the 
instrument made during the calendar quarter. For example, n should be 6 
or 7 if precision checks are made biweekly during a quarter. Equation 2 
and 3 follow:
                               Equation 2
[GRAPHIC] [TIFF OMITTED] TR18JY97.139

[[Page 227]]

                               Equation 3
[GRAPHIC] [TIFF OMITTED] TR18JY97.140

    5.1.2 Precision for Reporting Organization.
    5.1.2.1 For each pollutant, the average of averages (D) and the 
pooled standard deviation (S<INF>a</INF>) are calculated for all 
analyzers audited for the pollutant during the quarter, using either 
equations 4 and 5 or 4a and 5a, where k is the number of analyzers 
audited within the reporting organization for a single pollutant, as 
follows:
                               Equation 4
[GRAPHIC] [TIFF OMITTED] TR18JY97.141

                               Equation 4a
[GRAPHIC] [TIFF OMITTED] TR18JY97.142

                               Equation 5
[GRAPHIC] [TIFF OMITTED] TR18JY97.143

                               Equation 5a
[GRAPHIC] [TIFF OMITTED] TR18JY97.144

    5.1.2.2 Equations 4 and 5 are used when the same number of precision 
checks are made for each analyzer. Equations 4a and 5a are used to 
obtain a weighted average and a weighted standard deviation when 
different numbers of precision checks are made for the analyzers.
    5.1.2.3 For each pollutant, the 95 Percent Probability Limits for 
the precision of a reporting organization are calculated using equations 
6 and 7, as follows:
                               Equation 6
[GRAPHIC] [TIFF OMITTED] TR18JY97.145

                               Equation 7
[GRAPHIC] [TIFF OMITTED] TR18JY97.146

    5.2 Accuracy of Automated Methods Excluding PM<INF>2.5</INF>. 
Estimates of the accuracy of automated methods are calculated from the 
results of independent audits as described in section 3.2 of this 
appendix. At the end of each calendar quarter, an integrated accuracy 
probability interval for all SLAMS analyzers audited in the reporting 
organization is calculated for each pollutant. Separate probability 
limits are calculated for each audit concentration level in section 3.2 
of this appendix.
    5.2.1 Single Analyzer Accuracy. The percentage difference 
(d<INF>i</INF>) for each audit concentration is calculated using 
equation 1, where Y<INF>i</INF> is the analyzer's indicated 
concentration measurement from the I-th audit check and X<INF>i</INF> is 
the actual concentration of the audit gas used for the I-th audit check.
    5.2.2 Accuracy for Reporting Organization.
    5.2.2.1 For each audit concentration level of a particular 
pollutant, the average (D) of the individual percentage differences 
(d<INF>i</INF>) for all n analyzers audited during the quarter is 
calculated using equation 8, as follows:
                               Equation 8
[GRAPHIC] [TIFF OMITTED] TR18JY97.147

    5.2.2.2 For each concentration level of a particular pollutant, the 
standard deviation (S<INF>a</INF>) of all the individual percentage 
differences for all n analyzers audited during the quarter is 
calculated, using equation 9, as follows:

[[Page 228]]

                               Equation 9
[GRAPHIC] [TIFF OMITTED] TR18JY97.148

    5.2.2.3 For reporting organizations having four or fewer analyzers 
for a particular pollutant, only one audit is required each quarter. For 
such reporting organizations, the audit results of two consecutive 
quarters are required to calculate an average and a standard deviation, 
using equations 8 and 9. Therefore, the reporting of probability limits 
shall be on a semiannual (instead of a quarterly) basis.
    5.2.2.4 For each pollutant, the 95 Percent Probability Limits for 
the accuracy of a reporting organization are calculated at each audit 
concentration level using equations 6 and 7.
    5.3 Precision of Manual Methods Excluding PM<INF>2.5</INF>. 
Estimates of precision of manual methods are calculated from the results 
obtained from collocated samplers as described in section 3.3 of this 
appendix. At the end of each calendar quarter, an integrated precision 
probability interval for all collocated samplers operating in the 
reporting organization is calculated for each manual method network.
    5.3.1 Single Sampler Precision.
    5.3.1.1 At low concentrations, agreement between the measurements of 
collocated samplers, expressed as percent differences, may be relatively 
poor. For this reason, collocated measurement pairs are selected for use 
in the precision calculations only when both measurements are above the 
following limits:
    (a) TSP: 20 [mu]g/m<SUP>3</SUP>.
    (b) SO<INF>2</INF>: 45 [mu]g/m<SUP>3</SUP>.
    (c) NO<INF>2</INF>: 30 [mu]g/m<SUP>3</SUP>.
    (d) Pb: 0.15 [mu]g/m<SUP>3</SUP>.
    (e) PM<INF>10</INF>: 20 [mu]g/m<SUP>3</SUP>.
    5.3.1.2 For each selected measurement pair, the percent difference 
(d<INF>i</INF>) is calculated, using equation 10, as follows:
                               Equation 10
[GRAPHIC] [TIFF OMITTED] TR18JY97.149

where:

Y<INF>i</INF> is the pollutant concentration measurement obtained from 
the duplicate sampler; and
X<INF>i</INF> is the concentration measurement obtained from the primary 
sampler designated for reporting air quality for the site.

    (a) For each site, the quarterly average percent difference 
(d<INF>j</INF>) is calculated from equation 2 and the standard deviation 
(S<INF>j</INF>) is calculated from equation 3, where n= the number of 
selected measurement pairs at the site.
    5.3.2 Precision for Reporting Organization.
    5.3.2.1 For each pollutant, the average percentage difference (D) 
and the pooled standard deviation (S<INF>a</INF>) are calculated, using 
equations 4 and 5, or using equations 4a and 5a if different numbers of 
paired measurements are obtained at the collocated sites. For these 
calculations, the k of equations 4, 4a, 5 and 5a is the number of 
collocated sites.
    5.3.2.2 The 95 Percent Probability Limits for the integrated 
precision for a reporting organization are calculated using equations 11 
and 12, as follows:
                               Equation 11
[GRAPHIC] [TIFF OMITTED] TR18JY97.150

                               Equation 12
[GRAPHIC] [TIFF OMITTED] TR18JY97.151

    5.4 Accuracy of Manual Methods Excluding PM<INF>2.5</INF>. Estimates 
of the accuracy of manual methods are calculated from the results of 
independent audits as described in section 3.4 of this appendix. At the 
end of each calendar quarter, an integrated accuracy probability 
interval is calculated for each manual method network operated by the 
reporting organization.
    5.4.1 Particulate Matter Samplers other than PM<INF>2.5</INF> 
(including reference method Pb samplers).
    5.4.1.1 Single Sampler Accuracy. For the flow rate audit described 
in section 3.4.1 of this appendix, the percentage difference 
(d<INF>i</INF>) for each audit is calculated using equation 1, where 
X<INF>i</INF> represents the known flow rate and Y<INF>i</INF> 
represents the flow rate indicated by the sampler.
    5.4.1.2 Accuracy for Reporting Organization. For each type of 
particulate matter measured (e.g., TSP/Pb), the average (D) of the 
individual percent differences for all similar particulate matter 
samplers audited during the calendar quarter is calculated using 
equation 8. The standard deviation (S<INF>a</INF>) of the percentage 
differences for all of the similar particulate matter samplers audited 
during the calendar quarter is calculated using equation 9. The 95 
Percent Probability Limits for the integrated accuracy for the reporting 
organization are calculated using equations 6 and 7. For reporting 
organizations having four or fewer particulate matter

[[Page 229]]

samplers of one type, only one audit is required each quarter, and the 
audit results of two consecutive quarters are required to calculate an 
average and a standard deviation. In that case, probability limits shall 
be reported semi-annually rather than quarterly.
    5.4.2 Analytical Methods for SO<INF>2</INF>, NO<INF>2</INF>, and Pb.
    5.4.2.1 Single Analysis-Day Accuracy. For each of the audits of the 
analytical methods for SO<INF>2</INF>, NO<INF>2</INF>, and Pb described 
in sections 3.4.2, 3.4.3, and 3.4.4 of this appendix, the percentage 
difference (d<INF>j</INF>) at each concentration level is calculated 
using equation 1, where X<INF>j</INF> represents the known value of the 
audit sample and Y<INF>j</INF> represents the value of SO<INF>2</INF>, 
NO<INF>2</INF>, or Pb indicated by the analytical method.
    5.4.2.2 Accuracy for Reporting Organization. For each analytical 
method, the average (D) of the individual percent differences at each 
concentration level for all audits during the calendar quarter is 
calculated using equation 8. The standard deviation (S<INF>a</INF>) of 
the percentage differences at each concentration level for all audits 
during the calendar quarter is calculated using equation 9. The 95 
Percent Probability Limits for the accuracy for the reporting 
organization are calculated using equations 6 and 7.
    5.5 Precision, Accuracy and Bias for Automated and Manual 
PM<INF>2.5</INF> Methods.
    (a) Reporting organizations are required to report the data that 
will allow assessments of the following individual quality control 
checks and audits:
    (1) Flow rate audit.
    (2) Collocated samplers, where the duplicate sampler is not an FRM 
device.
    (3) Collocated samplers, where the duplicate sampler is an FRM 
device.
    (4) FRM audits.
    (b) EPA uses the reported results to derive precision, accuracy and 
bias estimates according to the following procedures.
    5.5.1 Flow Rate Audits. The reporting organization shall report both 
the audit standard flow rate and the flow rate indicated by the sampling 
instrument. These results are used by EPA to calculate flow rate 
accuracy and bias estimates.
    5.5.1.1 Accuracy of a Single Sampler - Single Check (Quarterly) 
Basis (d<INF>i</INF>). The percentage difference (d<INF>i</INF>) for a 
single flow rate audit d<INF>i</INF> is calculated using equation 13, 
where X<INF>i</INF> represents the audit standard flow rate (known) and 
Y<INF>i</INF> represents the indicated flow rate, as follows:
                               Equation 13
[GRAPHIC] [TIFF OMITTED] TR18JY97.152

    5.5.1.2 Bias of a Single Sampler - Annual Basis (D<INF>j</INF>). For 
an individual particulate sampler j, the average (D<INF>j</INF>) of the 
individual percentage differences (d<INF>i</INF>) during the calendar 
year is calculated using equation 14, where n<INF>j</INF> is the number 
of individual percentage differences produced for sampler j during the 
calendar year, as follows:
                               Equation 14
[GRAPHIC] [TIFF OMITTED] TR18JY97.153

    5.5.1.3 Bias for Each EPA Federal Reference and Equivalent Method 
Designation Employed by Each Reporting Organization - Quarterly Basis 
(D<INF>k,q</INF>). For method designation k used by the reporting 
organization, quarter q's single sampler percentage differences 
(d<INF>i</INF>) are averaged using equation 16, where n<INF>k,q</INF> is 
the number of individual percentage differences produced for method 
designation k in quarter q, as follows:
                               Equation 15
[GRAPHIC] [TIFF OMITTED] TR18JY97.154

    5.5.1.4 Bias for Each Reporting Organization - Quarterly Basis 
(D<INF>q</INF>). For each reporting organization, quarter q's single 
sampler percentage differences (d<INF>i</INF>) are averaged using 
equation 16, to produce a single average for each reporting 
organization, where n<INF>q</INF> is the total number of single sampler 
percentage differences for all federal reference or equivalent methods 
of samplers in quarter q, as follows:
                               Equation 16
[GRAPHIC] [TIFF OMITTED] TR18JY97.155

    5.5.1.5 Bias for Each EPA Federal Reference and Equivalent Method 
Designation Employed by Each Reporting Organization - Annual Basis 
(D<INF>k</INF>). For method designation k used by the reporting 
organization, the annual average percentage difference, D<INF>k</INF>, 
is derived using equation 17, where D<INF>k,q</INF> is the average 
reported for method designation k during the qth quarter, and 
n<INF>k,q</INF> is the number of the method designation k's monitors 
that were deployed during the qth quarter, as follows:

[[Page 230]]

                               Equation 17
[GRAPHIC] [TIFF OMITTED] TR18JY97.156

    5.5.1.6 Bias for Each Reporting Organization - Annual Basis (D). For 
each reporting organization, the annual average percentage difference, 
D, is derived using equation 18, where D<INF>q</INF> is the average 
reported for the reporting organization during the qth quarter, and 
n<INF>q</INF> is the total number monitors that were deployed during the 
qth quarter. A single annual average is produced for each reporting 
organization. Equation 18 follows:
                               Equation 18
[GRAPHIC] [TIFF OMITTED] TR18JY97.157

    5.5.2 Collocated Samplers, Where the Duplicate Sampler is not an FRM 
Device. (a) At low concentrations, agreement between the measurements of 
collocated samplers may be relatively poor. For this reason, collocated 
measurement pairs are selected for use in the precision calculations 
only when both measurements are above the following limits:
     PM<INF>2.5</INF> : 6 [mu]g/m<SUP>3</SUP>
(b) Collocated sampler results are used to assess measurement system 
precision. A collocated sampler pair consists of a primary sampler (used 
for routine monitoring) and a duplicate sampler (used as a quality 
control check). Quarterly precision estimates are calculated by EPA for 
each pair of collocated samplers and for each method designation 
employed by each reporting organization. Annual precision estimates are 
calculated by EPA for each primary sampler, for each EPA Federal 
reference method and equivalent method designation employed by each 
reporting organization, and nationally for each EPA Federal reference 
method and equivalent method designation.
    5.5.2.1 Percent Difference for a Single Check (d<INF>i</INF>). The 
percentage difference, d<INF>i</INF>, for each check is calculated by 
EPA using equation 19, where X<INF>i</INF> represents the concentration 
produced from the primary sampler and Y<INF>i</INF> represents 
concentration reported for the duplicate sampler, as follows:
                               Equation 19
[GRAPHIC] [TIFF OMITTED] TR18JY97.158

    5.5.2.2 Coefficient of Variation (CV) for a Single Check 
(CV<INF>i</INF>). The coefficient of variation, CV<INF>i</INF>, for each 
check is calculated by EPA by dividing the absolute value of the 
percentage difference, d<INF>i</INF>, by the square root of two as shown 
in equation 20, as follows:
                               Equation 20
[GRAPHIC] [TIFF OMITTED] TR18JY97.159

    5.5.2.3 Precision of a Single Sampler - Quarterly Basis 
(CV<INF>j,q</INF>).
    (a) For particulate sampler j, the individual coefficients of 
variation (CV<INF>j,q</INF>) during the quarter are pooled using 
equation 21, where n<INF>j,q</INF> is the number of pairs of 
measurements from collocated samplers during the quarter, as follows:
                               Equation 21
[GRAPHIC] [TIFF OMITTED] TR18JY97.160

    (b) The 90 percent confidence limits for the single sampler's CV are 
calculated by EPA using equations 22 and 23, where X<SUP>2</SUP> 
<INF>0.05,df</INF> and X<SUP>2</SUP> <INF>0.95,df</INF> are the 0.05 and 
0.95 quantiles of the chi-square (X<SUP>2</SUP>) distribution with 
n<INF>j,q</INF> degrees of freedom, as follows:
                               Equation 22
[GRAPHIC] [TIFF OMITTED] TR18JY97.161

                               Equation 23
[GRAPHIC] [TIFF OMITTED] TR18JY97.162

    5.5.2.4 Precision of a Single Sampler - Annual Basis. For 
particulate sampler j, the individual coefficients of variation, 
CV<INF>i</INF>, produced during the calendar year are pooled using 
equation 21, where n<INF>j</INF> is the number of checks made during the 
calendar year. The 90 percent confidence limits for the single

[[Page 231]]

sampler's CV are calculated by EPA using equations 22 and 23, where 
X<SUP>2</SUP> <INF>0.05,df</INF> and X<SUP>2</SUP> <INF>0.95,df</INF> 
are the 0.05 and 0.95 quantiles of the chi-square (X<SUP>2</SUP>) 
distribution with n<INF>j</INF> degrees of freedom.
    5.5.2.5 Precision for Each EPA Federal Reference Method and 
Equivalent Method Designation Employed by Each Reporting Organization - 
Quarterly Basis (CV<INF>k,q</INF>).
    (a) For each method designation k used by the reporting 
organization, the quarter's single sampler coefficients of variation, 
CV<INF>j,q</INF>s, obtained from equation 21, are pooled using equation 
24, where n<INF>k,q</INF> is the number of collocated primary monitors 
for the designated method (but not collocated with FRM samplers) and 
n<INF>j,q</INF> is the number of degrees of freedom associated with 
CV<INF>j,q</INF>, as follows:
                               Equation 24
[GRAPHIC] [TIFF OMITTED] TR18JY97.163

    (b) The number of method CVs produced for a reporting organization 
will equal the number of different method designations having more than 
one primary monitor employed by the organization during the quarter. 
(When exactly one monitor of a specified designation is used by a 
reporting organization, it will be collocated with an FRM sampler.)
    5.5.2.6 Precision for Each Method Designation Employed by Each 
Reporting Organization - Annual Basis (CV<INF>k</INF>). For each method 
designation k used by the reporting organization, the quarterly 
estimated coefficients of variation, CV<INF>k,q</INF>, are pooled using 
equation 25, where n<INF>k,q</INF> is the number of collocated primary 
monitors for the designated method during the qth quarter and also the 
number of degrees of freedom associated with the quarter's precision 
estimate for the method designation, CV<INF>k,q</INF>, as follows:
                               Equation 25
[GRAPHIC] [TIFF OMITTED] TR18JY97.164

    5.5.3 Collocated Samplers, Where the Duplicate Sampler is an FRM 
Device. At low concentrations, agreement between the measurements of 
collocated samplers may be relatively poor. For this reason, collocated 
measurement pairs are selected for use in the precision calculations 
only when both measurements are above the following limits: 
PM<INF>2.5</INF>: 6 [mu]g/m<SUP>3</SUP>. These duplicate sampler results 
are used to assess measurement system bias. Quarterly bias estimates are 
calculated by EPA for each primary sampler and for each method 
designation employed by each reporting organization. Annual precision 
estimates are calculated by EPA for each primary monitor, for each 
method designation employed by each reporting organization, and 
nationally for each method designation.
    5.5.3.1 Accuracy for a Single Check (d'<INF>i</INF>). The percentage 
difference, d'<INF>i</INF>, for each check is calculated by EPA using 
equation 26, where X<INF>i</INF> represents the concentration produced 
from the FRM sampler taken as the true value and Y<INF>i</INF> 
represents concentration reported for the primary sampler, as follows:
                               Equation 26
[GRAPHIC] [TIFF OMITTED] TR18JY97.165

    5.5.3.2 Bias of a Single Sampler - Quarterly Basis 
(D'<INF>j,q</INF>).
    (a) For particulate sampler j, the average of the individual 
percentage differences during the quarter q is calculated by EPA using 
equation 27, where n<INF>j,q</INF> is the number of checks made for 
sampler j during the calendar quarter, as follows:
                               Equation 27
[GRAPHIC] [TIFF OMITTED] TR18JY97.166

    (b) The standard error, s'<INF>j,q</INF>, of sampler j's percentage 
differences for quarter q is calculated using equation 28, as follows:

[[Page 232]]

                               Equation 28
[GRAPHIC] [TIFF OMITTED] TR17FE98.007

    (c) The 95 Percent Confidence Limits for the single sampler's bias 
are calculated using equations 29 and 30 where t<INF>0.975,df</INF> is 
the 0.975 quantile of Student's t distribution with df = 
n<INF>j,q</INF>-1 degrees of freedom, as follows:
                               Equation 29
[GRAPHIC] [TIFF OMITTED] TR18JY97.168

                               Equation 30
[GRAPHIC] [TIFF OMITTED] TR18JY97.169

    5.5.3.3 Bias of a Single Sampler - Annual Basis (D'<INF>j</INF>).
    (a) For particulate sampler j, the mean bias for the year is derived 
from the quarterly bias estimates, D'<INF>j,q</INF>, using equation 31, 
where the variables are as defined for equations 27 and 28, as follows:
                               Equation 31
[GRAPHIC] [TIFF OMITTED] TR18JY97.170

    (b) The standard error of the above estimate, se<INF>j</INF>' is 
calculated using equation 32, as follows:
                               Equation 32
[GRAPHIC] [TIFF OMITTED] TR18JY97.171

    (c) The 95 Percent Confidence Limits for the single sampler's bias 
are calculated using equations 33 and 34, where t<INF>0.975,df</INF> is 
the 0.975 quantile of Student's t distribution with df = 
(n<INF>j,1</INF> + n<INF>j,2</INF> + n<INF>j,3</INF> + n<INF>j,4</INF>-
4) degrees of freedom, as follows:
                               Equation 33
[GRAPHIC] [TIFF OMITTED] TR18JY97.172

                               Equation 34
[GRAPHIC] [TIFF OMITTED] TR18JY97.173

    5.5.3.4 Bias for a Single Reporting Organization (D') - Annual 
Basis. The reporting organizations mean bias is calculated using 
equation 35, where variables are as defined in equations 31 and 32, as 
follows:
                               Equation 35
[GRAPHIC] [TIFF OMITTED] TR18JY97.174

    5.5.4 FRM Audits. FRM Audits are performed once per quarter for 
selected samplers. The reporting organization reports concentration data 
from the primary sampler. Calculations for FRM Audits are similar to 
those for collocated samplers having FRM samplers as duplicates. The 
calculations differ because only one check is performed per quarter.
    5.5.4.1 Accuracy for a Single Sampler, Quarterly Basis 
(d<INF>i</INF>). The percentage difference, d<INF>i</INF>, for each 
check is calculated using equation 26, where X<INF>i</INF> represents 
the concentration produced from the FRM sampler and Y<INF>i</INF> 
represents the concentration reported for the primary sampler. For 
quarter q, the bias estimate for sampler j is denoted D<INF>j,q</INF>.
    5.5.4.2 Bias of a Single Sampler - Annual Basis (D'<INF>j</INF>). 
For particulate sampler j, the mean bias for the year is derived from 
the quarterly bias estimates, D<INF>j,q</INF>, using equation 31, where 
n<INF>j,q</INF> equals 1 because one FRM audit is performed per quarter.
    5.5.4.3. Bias for a Single Reporting Organization - Annual Basis 
(D'). The reporting organizations mean bias is calculated using equation 
35, where variables are as defined in equations 31 and 32.

                   References in Appendix A of Part 58

    (1) Rhodes, R.C. Guideline on the Meaning and Use of Precision and 
Accuracy Data Required by 40 CFR part 58, Appendices A and

[[Page 233]]

B. EPA-600/4-83/023. U.S. Environmental Protection Agency, Research 
Triangle Park, NC 27711, June, 1983.
    (2) American National Standard--Specifications and Guidelines for 
Quality Systems for Environmental Data Collection and Environmental 
Technology Programs. ANSI/ASQC E4-1994. January 1995. Available from 
American Society for Quality Control, 611 East Wisconsin Avenue, 
Milwaukee, WI 53202.
    (3) EPA Requirements for Quality Management Plans. EPA QA/R-2. 
August 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.
    (4) EPA Requirements for Quality Assurance Project Plans for 
Environmental Data Operations. EPA QA/R-5. August 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.
    (5) Guidance for the Data Quality Objectives Process. EPA QA/G-4. 
September 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.
    (6) 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.
    (7) Quality Assurance Handbook for Air Pollution Measurement 
Systems, Volume II--Ambient Air Specific Methods EPA-600/R-94/038b. 
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.
    (7a) Copies of section 2.12 of the Quality Assurance Handbook for 
Air Pollution Measurement Systems, are available from Department E (MD-
77B), U.S. EPA, Research Triangle Park, NC 27711.
    (8) List of Designated Reference and Equivalent Methods. Available 
from U.S. Environmental Protection Agency, National Exposure Research 
Laboratory, Quality Assurance Branch, MD-77B, Research Triangle Park, NC 
27711.
    (9) 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.
    (10) EPA Traceability Protocol for Assay and Certification of 
Gaseous Calibration Standards. EPA-600/R-93/224. September 1993. 
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.
    (11) 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.
    (12) McElroy, F.F. Transfer Standards for the Calibration of Ambient 
Air Monitoring Analyzers for Ozone. EPA-600/4-79-056. U.S. Environmental 
Protection Agency, Research Triangle Park, NC 27711, September, 1979.
    (13) Musick, D.R. The Ambient Air Precision and Accuracy Program: 
1995 Annual Report. EPA-454/R97001. U.S. Environmental Protection 
Agency, Research Triangle Park, NC 27711, February 1997.
    (14) Papp, M.L., J,B., Elkins, D.R., Musick and M.J., Messner, Data 
Quality Objectives for the PM<INF>2.5</INF>. Monitoring Data, U.S. 
Environmental Protection Agency, Research Triangle Park, NC 27711. In 
preparation.
    (15) Photochemical Assessment Monitoring Stations Implementation 
Manual. EPA-454/B-93-051, U.S. Environmental Protection Agency, Research 
Triangle Park, NC 27711, March 1994.

                          Table A-1 to Appendix A--Minimum Data Assessment Requirements
----------------------------------------------------------------------------------------------------------------
        Method           Assessment Method           Coverage          Minimum Frequency     Parameters Reported
----------------------------------------------------------------------------------------------------------------
Precision:
    Automated Methods  Response check at      Each analyzer          Once per 2 weeks       Actual concentration
     for SO2, NO2,      concentration                                                        \2\ and measured
     O3, and CO         between .08 and .10                                                  concentration \3\
                        ppm (8 & 10 ppm for
                        CO) \2\

    Manual Methods:    Collocated samplers    1 site for 1-5 sites   Once every six days    Particle mass
     All methods                              2 sites for 6-20                               concentration
     except PM2.5                              sites                                         indicated by
                                              3 sites <ls-thn-eq>20                          sampler and by
                                               sites (sites with                             collocated sampler
                                               highest conc.)
Accuracy:

[[Page 234]]

    Automated Methods  Response check at      1. Each analyzer       1. Once per year       Actual concentration
     for SO2, NO2,     .03-.08 ppm1,2         2. 25% of analyzers    2. Each calendar        \2\ and measured
     O3, and CO        .15-.20 ppm1,2          (at least 1)           quarter                (indicated)
                       .35-.45 ppm1,2                                                        concentration \3\
                       80-.90 ppm1,2 (if                                                     for each level
                        applicable)

    Manual Methods     Check of analytical    Analytical system      Each day samples are   Actual concentration
     for SO2, and NO2   procedure with audit                          analyzed, at least     and measured
                        standard solutions                            twice per quarter      (indicated)
                                                                                             concentration for
                                                                                             each audit solution

    TSP, PM10          Check of sampler flow  1. Each sampler        1. Once per year       Actual flow rate and
                        rate                  2. 25% of samplers     2. Each calendar        flow rate indicated
                                               (at least 1)           quarter                by the sampler

    Lead               1. Check of sample     1. Each sampler        1. Include with TSP    1. Same as for TSP
                        flow rate as for TSP
                       2. Check of            2. Analytical system   2. Each quarter        2. Actual
                        analytical system                                                    concentration and
                        with Pb audit strips                                                 measured
                                                                                             (indicated)
                                                                                             concentration of
                                                                                             audit samples
                                                                                             ([mu]g Pb/strip)
PM2.5
    Manual and         Collocated samplers    25% of SLAMS           Once every six days    1. Particle mass
     Automated                                 (monitors with Conc                           concentration
     Methods-                                  affecting NAAQS                               indicated by
     Precision                                 violation status)                             sampler and by
                                                                                             collocated sampler
                                                                                            2. 24-hour value for
                                                                                             automated methods
    Manual and         1. Check of sampler    Every SLAMS monitor    1. Automated--once     1. Actual flow rate
     Automated          flow rate                                     every 2 weeks;         and flow rate
     Methods-Accuracy                                                 Manual--each           indicated by
     and Bias                                                         calendar quarter (4/   sampler
                                                                      year)
                       2. Audit with          .....................  2. Minimum 4           2. Particle mass
                        reference method                              measurements per       concentration
                                                                      year                   indicated by
                                                                                             sampler and by
                                                                                             audit reference
                                                                                             sampler
----------------------------------------------------------------------------------------------------------------
\1\ Concentration times 100 for CO.
\2\ Effective concentration for open path analyzers.
\3\ Corrected concentration, if applicable, for open path analyzers.

Table A-2 to Appendix A--Summary of PM2.5 Collocation and Audits Procedures As an Example of a Typical Reporting
         Organization Needing 43 Monitors, Having Procured FRMs and Three Other Equivalent Method Types
----------------------------------------------------------------------------------------------------------------
                                                                                <greek-i> of
                         Total <greek-i>   Total <greek-i>    <greek-i> of       Collocated       <greek-i> of
  Method Designation       of Monitors       Collocated      Collocated FRMs  Monitors of Same   Independent FRM
                                                                                    Type             Audits
----------------------------------------------------------------------------------------------------------------
FRM                            25                 6                 6                n/a                6
Type A                         10                 3                 2                 1                 3
Type C                          2                 1                 1                 0                 1
Type D                          6                 2                 1                 1                 2
----------------------------------------------------------------------------------------------------------------

[62 FR 38833, July 18, 1997; 63 FR 7714, 7715, Feb. 17, 1998; 68 FR 
80328, Dec. 31, 2002]

Appendix B to Part 58--Quality Assurance Requirements for Prevention of 
             Significant Deterioration (PSD) Air Monitoring

1. General Information
    This appendix specifies the minimum quality assurance requirements 
for the control and assessment of the quality of the PSD ambient air 
monitoring data submitted to EPA by an organization operating a network 
of PSD stations. Such organizations are encouraged to develop and 
maintain quality assurance programs more extensive than the required 
minimum.
    Quality assurance of air monitoring systems includes two distinct 
and important interrelated functions. One function is the

[[Page 235]]

control of the measurement process through the implementation of 
policies, procedures, and corrective actions. The other function is the 
assessment of the quality of the monitoring data (the product of the 
measurement process). In general, the greater the effort and 
effectiveness of the control of a given monitoring system, the better 
will be the resulting quality of the monitoring data. The results of 
data quality assessments indicate whether the control efforts need to be 
increased.
    Documentation of the quality assessments of the monitoring data is 
important to data users, who can then consider the impact of the data 
quality in specific applications (see Reference 1). Accordingly, 
assessments of PSD monitoring data quality are required to be made and 
reported periodically by the monitoring organization.
    To provide national uniformity in the assessment and reporting of 
data quality among all PSD networks, specific assessment and reporting 
procedures are prescribed in detail in sections 3, 4, 5, and 6 of this 
appendix.
    In contrast, the control function encompasses a variety of policies, 
procedures, specifications, standards, and corrective measures which 
affect the quality of the resulting data. The selection and extent of 
the quality control activities--as well as additional quality assessment 
activities--used by a monitoring organization depend on a number of 
local factors such as the field and laboratory conditions, the 
objectives of the monitoring, the level of the data quality needed, the 
expertise of assigned personnel, the cost of control procedures, 
pollutant concentration levels, etc. Therefore, the quality assurance 
requirements, in section 2 of this appendix, are specified in general 
terms to allow each organization to develop a quality control system 
that is most efficient and effective for its own circumstances.
    For purposes of this appendix, ``organization'' is defined as a 
source owner/operator, a government agency, or their contractor that 
operates an ambient air pollution monitoring network for PSD purposes.

2. Quality Assurance Requirements

    2.1 Each organization must develop and implement a quality assurance 
program consisting of policies, procedures, specifications, standards 
and documentation necessary to:
    (1) Provide data of adequate quality to meet monitoring objectives 
and quality assurance requirements of the permit-granting authority, and
    (2) Minimize loss of air quality data due to malfunctions or out-of-
control conditions.
    This quality assurance program must be described in detail, suitably 
documented, and approved by the permit-granting authority. The Quality 
Assurance Program will be reviewed during the system audits described in 
section 2.4.
    2.2 Primary guidance for developing the Quality Assurance Program is 
contained in References 2 and 3, which also contain many suggested 
procedures, checks, and control specifications. Section 2.0.9 of 
Reference 3 describes specific guidance for the development of a Quality 
Assurance Program for automated analyzers. Many specific quality control 
checks and specifications for manual methods are included in the 
respective reference methods described in part 50 of this chapter or in 
the respective equivalent method descriptions available from EPA (see 
Reference 4). Similarly, quality control procedures related to 
specifically designated reference and equivalent analyzers are contained 
in their respective operation and instruction manuals. This guidance, 
and any other pertinent information from appropriate sources, should be 
used by the organization in developing its quality assurance program.
    As a minimum, each quality assurance program must include 
operational procedures for each of the following activities:
    (1) Selection of methods, analyzers, or samplers;
    (2) Training;
    (3) Installation of equipment;
    (4) Selection and control of calibration standards;
    (5) Calibration;
    (6) Zero/span checks and adjustments of automated analyzers;
    (7) Control checks and their frequency;
    (8) Control limits for zero, span and other control checks, and 
respective corrective actions when such limits are surpassed;
    (9) Calibration and zero/span checks for multiple range analyzers 
(see section 2.6 of appendix C of this part);
    (10) Preventive and remedial maintenance;
    (11) Recording and validating data;
    (12) Date quality assessment (precision and accuracy);
    (13) Documentation of quality control information.
    2.3 Pollutant Standards.
    2.3.1 Gaseous standards (permeation tubes, permeation devices or 
cylinders of compressed gas) used to obtain test concentrations for CO, 
SO<INF>2</INF>, and NO<INF>2</INF> must be traceable to either a 
National Institute of Standards and Technology (NIST) gaseous Standard 
Reference Material (SRM) or an NIST/EPA-approved commercially available 
Certified Reference Material (CRM). CRM's are described in Reference 5, 
and a list of CRM sources is available from Quality Assurance Division 
(MD-77), Atmospheric Research and Exposure Assessment Laboratory, U.S. 
Environmental Protection Agency, Research Triangle Park, NC 27711. A 
recommended protocol for certifying gaseous standards against an SRM or 
CRM is given in section

[[Page 236]]

2.0.7 of Reference 3. Direct use of a CRM as a working standard is 
acceptable, but direct use of an NIST SRM as a working standard is 
discouraged because of the limited supply and expense of SRM's.
    2.3.2 Test concentrations for ozone must be obtained in accordance 
with the UV photometric calibration procedure specified in appendix D of 
part 50 of this chapter, or by means of a certified ozone transfer 
standard. Consult References 6 and 7 for guidance on primary and 
transfer standards for ozone.
    2.3.3. Flow measurement must be made by a flow measuring instrument 
that is traceable to an authoritative volume or other standard. Guidance 
for certifying various types of flowmeters is provided in Reference 3.
    2.4 Performance and System Audit Programs. The organization 
operating a PSD monitoring network must participate in EPA's national 
performance audit program. The permit granting authority, or EPA, may 
conduct system audits of the ambient air monitoring programs of 
organizations operating PSD networks. See section 1.4.16 of reference 2 
and section 2.0.11 of reference 3 for additional information about these 
programs. Organizations should contact either the appropriate EPA 
Regional Quality Control Coordinator or the Quality Assurance Branch, 
AREAL/RTP, at the address given in reference 3 for instructions for 
participation.

3. Data Quality Assessment Requirements

    All ambient monitoring methods or analyzers used in PSD monitoring 
shall be tested periodically, as described in this section 3, to 
quantitatively assess the quality of the data being routinely collected. 
The results of these tests shall be reported as specified in section 6. 
Concentration standards used for the tests must be as specified in 
section 2.3. Additional information and guidance in the technical 
aspects of conducting these tests may be found in Reference 3 or in the 
operation or instruction manual associated with the analyzer or sampler. 
Concentration measurements reported from analyzers or analytical systems 
must be derived by means of the same calibration curve and data 
processing system used to obtain the routine air monitoring data. Table 
B-1 provides a summary of the minimum data quality assessment 
requirements, which are described in more detail in the following 
sections.
    3.1 Precision of Automated Methods. A one-point precision check must 
be carried out at least once every two weeks on each automated analyzer 
used to measure SO<INF>2</INF>, NO<INF>2</INF>, O<INF>2</INF>, and CO. 
The precision check is made by challenging the analyzer with a precision 
check gas of known concentration (effective concentration for open path 
analyzers) between 0.08 and 0.10 ppm for SO<INF>2</INF>, NO<INF>2</INF>, 
and O<INF>3</INF> analyzers, and between 8 and 10 ppm for CO analyzers. 
The standards from which precision check test concentrations are 
obtained must meet the specifications of section 2.3. Except for certain 
CO analyzers described below, point analyzers must operate in their 
normal sampling mode during the precision 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. If permitted by the 
associated operation or instruction manual, a CO point analyzer may be 
temporarily modified during the precision check to reduce vent or purge 
flows, or the test atmosphere may enter the analyzer at a point other 
than the normal sample inlet, provided that the analyzer's response is 
not likely to be altered by these deviations from the normal operational 
mode.
    Open path analyzers are tested by inserting a test cell containing a 
precision 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 precision check gas in the test cell must be 
selected to produce an ``effective concentration'' in the range 
specified above. Generally, the precision test concentration measurement 
will be the sum of the atmospheric pollutant concentration and the 
precision test concentration. If so, 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 precision check test 
from the precision test 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 analyzers should be tested 
during periods when the atmospheric pollutant concentrations are 
relatively low and steady.
    If a precision check is made in conjunction with a zero or span 
adjustment, it must be made prior to such zero or span adjustment. The 
difference between the actual concentration (effective concentration for 
open path analyzers) of the precision check gas and the corresponding 
concentration measurement (corrected concentration, if applicable, for

[[Page 237]]

open path analyzers) indicated by the analyzer is used to assess the 
precision of the monitoring data as described in section 4.1. Report 
data only from automated analyzers that are approved for use in the PSD 
network.
    3.2 Accuracy of Automated Methods. Each sampling quarter, audit each 
analyzer that monitors for SO<INF>2</INF>, NO<INF>2</INF>, 
O<INF>3</INF>, or CO at least once. The audit is made by challenging the 
analyzer with at least one audit gas of known concentration (effective 
concentration for open path analyzers) from each of the following ranges 
that fall within the measurement range of the analyzer being audited:

------------------------------------------------------------------------
                                     Concentration range, ppm
            Audit level             --------------------------     CO
                                       SO2, O3,       NO2,
------------------------------------------------------------------------
1..................................    0.03-0.08    0.03-0.08     3-8
2..................................    0.15-0.20    0.15-0.20   15-20
3..................................    0.36-0.45    0.35-0.45   35-45
4..................................    0.80-0.90  ...........   80-90
------------------------------------------------------------------------

NO<INF>2</INF> audit gas for chemiluminescence-type NO<INF>2</INF> 
analyzers must also contain at least 0.08 ppm NO.

    Note: NO concentrations substantially higher than 0.08 ppm, as may 
occur when using some gas phase titration (GPT) techniques, may lead to 
audit errors in chemiluminescence analyzers due to inevitable minor NO-
NO<INF>X</INF> channel imbalance. Such errors may be atypical of routine 
monitoring errors to the extent that such NO concentrations exceed 
typical ambient NO concentrations. These errors may be minimized by 
modifying the GPT technique to lower the NO concentrations remaining in 
the NO<INF>2</INF> audit gas to levels closer to typical ambient NO 
concentrations at the site.

    The standards from which audit gas test concentrations are obtained 
must meet the specifications of section 2.3. Working and transfer 
standards and equipment used for auditing must be different from the 
standards and equipment used for calibration and spanning. The auditing 
standards and calibration standards may be referenced to the same NIST, 
SRM, CRM, or primary UV photometer. The auditor must not be the 
operator/analyst who conducts the routine monitoring, calibration and 
analysis.
    For point analyzers, the audit shall be carried out by allowing the 
analyzer to analyze the audit test atmosphere in the same manner as 
described for precision checks in section 3.1. The exception given in 
section 3.1 for certain CO analyzers does not apply for audits.
    Open path analyzers are audited by inserting a test cell containing 
an audit 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 audit, and 
the normal monitoring configuration of the instrument should be modified 
as little as possible to accommodate the test cell for the audit. 
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 range specified in this 
section 3.2. Generally, each audit concentration measurement result will 
be the sum of the atmospheric pollutant concentration and the audit test 
concentration. If so, 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 audit test (or preferably before and after each 
audit concentration level) from the audit concentration measurement. If 
the difference between these before and after measurements is greater 
than 20 percent of the effective concentration of the test gas 
standards, discard the test result for that concentration level and 
repeat the test for that level. If possible, open path analyzers should 
be audited during periods when the atmospheric pollutant concentrations 
are relatively low and steady. Also, the monitoring path length must be 
reverified to within <plus-minus<ls-thn-eq>3 percent to validate the 
audit, since the monitoring path length is critical to the determination 
of the effective concentration.
    The differences between the actual concentrations (effective 
concentrations for open path analyzers) of the audit test gas and the 
corresponding concentration measurements (corrected concentrations, if 
applicable, for open path analyzers) indicated by the analyzer are used 
to assess the accuracy of the monitoring data as described in section 
4.2. Report data only from automated analyzers that are approved for use 
in the PSD network.
    3.3 Precision of Manual Methods.
    3.3.1 TSP and PM<INF>10</INF> Methods. For a given organization's 
monitoring network, one sampling site must have collocated samplers. A 
site with the highest expected 24-hour pollutant concentration must be 
selected. The two samplers must be within 4 meters of each other but at 
least 2 meters apart to preclude airflow interference. Calibration, 
sampling and analysis must be the same for both collocated samplers as 
well as for all other samplers in the network. The collocated samplers 
must be operated as a minimum every third day when continuous sampling 
is used. When a less frequent sample schedule is

[[Page 238]]

used, the collocated samplers must be operated at least once each week. 
For each pair of collocated samplers, designate one sampler as the 
sampler which will be used to report air quality for the site and 
designate the other as the duplicate sampler. The differences in 
measured concentration ([mu] g/m\3\) between the two collocated samplers 
are used to calculate precision as described in section 5.1.
    3.3.2 Pb Method. The operation of collocated samplers at one 
sampling site must be used to assess the precision of the reference or 
an equivalent Pb method. The procedure to be followed for Pb methods is 
the same as described in 3.3.1 for the TSP method. If approved by the 
permit granting authority, the collocated TSP samplers may serve as the 
collocated lead samplers.
    3.4 Accuracy of Manual Methods.
    3.4.1 TSP and PM<INF>10</INF> Methods. Each sampling quarter, audit 
the flow rate of each sampler at least once. Audit the flow at the 
normal flow rate, using a certified flow transfer standard (see 
reference 2). The flow transfer standard used for the audit must not be 
the same one used to calibrate the flow of the sampler being audited, 
although both transfer standards may be referenced to the same primary 
flow or volume standard. The difference between the audit flow 
measurement and the flow indicated by the sampler's flow indicator is 
used to calculate accuracy, as described in paragraph 5.2.
    Great care must be used in auditing high-volume samplers having flow 
regulators because the introduction of resistance plates in the audit 
device can cause abnormal flow patterns at the point of flow sensing. 
For this reason, the orifice of the flow audit device should be used 
with a normal glass fiber filter in place and without resistance plates 
in auditing flow regulated high-volume samplers, or other steps should 
be taken to assure that flow patterns are not perturbed at the point of 
flow sensing.
    3.4.2 Pb Method. For the reference method (appendix G of part 50 of 
this chapter) during each sampling quarter audit the flow rate of each 
high-volume Pb sampler at least once. The procedure to be followed for 
lead methods is the same as described in section 3.4.1 for the TSP 
method.
    For each sampling quarter, audit the Pb analysis using glass fiber 
filter strips containing a known quantity of lead. Audit samples are 
prepared by depositing a Pb solution on 1.9 cm by 20.3 cm (\3/4\ inch by 
8 inch) unexposed glass fiber filter strips and allowing to dry 
thoroughly. The audit samples must be prepared using reagents different 
from those used to calibrate the Pb analytical equipment being audited. 
Prepare audit samples in the following concentration ranges:

------------------------------------------------------------------------
                                                      Equivalent ambient
             Ranges                Pb concentration    Pb concentration
                                     [mu] g/strip      \1\ [mu] g/m \3\
------------------------------------------------------------------------
1...............................  100 to 300........  0.5 to 1.5.
2...............................  600 to 1,000......  3.0 to 5.0.
------------------------------------------------------------------------
\1\ Equivalent ambient Pb concentration in [mu] g/m\3\ is based on
  sampling at 1.7 m\3\/min for 24 hours on 20.3 cm x 25.4 cm (8 inch x
  10 inch) glass fiber filter.

    Audit samples must be extracted using the same extraction procedure 
used for exposed filters.
    Analyze at least one audit sample in each of the two ranges each day 
that samples are anlayzed. The difference between the audit 
concentration (in mu;g Pb/strip) and the analyst's measured 
concentration (in mu;g Pb/strip is used to calculate accuracy as 
described in section 5.4.
    The accuracy of an equivalent method is assessed in the same manner 
as the reference method. The flow auditing device and Pb analysis audit 
samples must be compatible with the specific requirements of the 
equivalent method.

4. Calculations for Automated Methods

    4.1 Single Analyzer Precision. Each organization, at the end of each 
sampling quarter, shall calculate and report a precision probability 
interval for each analyzer. Directions for calculations are given below 
and directions for reporting are given in section 6. If monitoring data 
are invalidated during the period represented by a given precision 
check, the results of that precision check shall be excluded from the 
calculations. Calculate the percentage difference (d<INF>i</INF>) for 
each precision check using equation 1.
[GRAPHIC] [TIFF OMITTED] TC09NO91.023

where:

Y<INF>i</INF> = analyzer's indicated concentration from the i-th 
precision check
X<INF>i</INF> = known concentration of the test gas used for the i-th 
precision check.

For each instrument, calculate the quarterly average (d<INF>j</INF>), 
equation 2, and the standard deviation (S<INF>j</INF>), equation 3.
[GRAPHIC] [TIFF OMITTED] TC09NO91.024

[GRAPHIC] [TIFF OMITTED] TC09NO91.025

where n is the number of precision checks on the instrument made during 
ther sampling quarter. For example, n should be 6 or 7 if span checks 
are made biweekly during a quarter.

[[Page 239]]

    Calculate the 95 percent probability limits for precision using 
equation 4 and 5.

Upper 95 Percent Probability
Limit = d<INF>j</INF>+1.96 S<INF>j</INF>
                                                                     (4)
Lower 95 Percent Probability
Limit = d<INF>j</INF>-1.96 S<INF>j</INF>
                                                                     (5)

    4.2 Single Analyzer Accuracy. Each organization, at the end of each 
sampling quarter, shall calculate and report the percentage difference 
for each audit concentration for each analyzer audited during the 
quarter. Directions for calculations are given below (directions for 
reporting are given in section 6).
    Calculate and report the percentage difference (d<INF>i</INF>) for 
each audit concentration using equation 1 where Y<INF>i</INF> is the 
analyzer's indicated concentration from the i-th audit check and 
X<INF>i</INF> is the known concentration of the audit gas used for the 
i-th audit check.

5. Calculations for Manual Methods

    5.1 Single Instrument Precision for TSP, Pb and PM<INF>10</INF>. 
Estimates of precision for ambient air quality particulate measurements 
are calculated from results obtained from collocated samplers as 
described in section 3.3. At the end of each sampling quarter, calculate 
and report a precision probability interval, using weekly result from 
the collecated samplers. Directions for calculations are given below, 
and directions for reporting are given in section 6.
    For the paired measurements obtained as described in sections 3.3.1 
and 3.3.2, calculate the percent difference (d<INF>i</INF>) using 
equation 1a, where Y<INF>i</INF> is the concentration of pollutant 
measured by the duplicate sampler, and X<INF>i</INF> is the 
concentration measured by the sampler reporting air quality for the 
site. Calculate the quarterly average percent difference 
(d<INF>j</INF>), equation 2; standard deviation (S<INF>j</INF>), 
equation 3; and upper and lower 95 percent probability limits for 
precision, equations 6 and 7.
[GRAPHIC] [TIFF OMITTED] TC09NO91.026

                                                                    (1a)

Upper 95 percent probability
limit = d<INF>j</INF>+1.96 S<INF>j</INF>/<radical>2
                                                                     (6)
Lower 95 percent probability
limit = d<INF>j</INF>-1.96 S<INF>j</INF>/<radical>2
                                                                     (7)

    5.2 Single Instrument Accuracy for TSP and PM<INF>10</INF>. Each 
organization, at the end of each sampling quarter, shall calculate and 
report the percentage difference for each high-volume or PM<INF>10</INF> 
sampler audited during the quarter. Directions for calculation are given 
below and directions for reporting are given in section 6.
    For the flow rate audit described in section 3.4, let X<INF>i</INF> 
represent the known flow rate and Y<INF>i</INF> represent the indicated 
flow rate. Calculate the percentage difference (d<INF>i</INF>) using 
equation 1.
    5.3 Single Instrument Accuracy for Pb. Each organization, at the end 
of each sampling quarter, shall calculate and report the percentage 
difference for each high-volume lead sampler audited during the quarter. 
Directions for calculation are given in 5.2 and directions for reporting 
are given in section 6.
    5.4 Single-Analysis-Day Accuracy for Pb. Each organization, at the 
end of each sampling quarter, shall calculate and report the percentage 
difference for each Pb analysis audit during the quarter. Directions for 
calculations are given below and directions for reporting are given in 
section 6.
    For each analysis audit for Pb described in section 3.4.2, let 
X<INF>i</INF> represent the known value of the audit sample and 
Y<INF>i</INF> the indicated value of Pb. Calculate the percentage 
difference (d<INF>i</INF>) for each audit at each concentration level 
using equation 1.

6. Organization Reporting Requirements.

    At the end of each sampling quarter, the organization must report 
the following data assessment information:
    (1) For automated analyzers--precision probability limits from 
section 4.1 and percentage differences from section 4.2, and
    (2) For manual methods--precision probability limits from section 
5.1 and percentage differences from sections 5.2 and 5.3. The precision 
and accuracy information for the entire sampling quarter must be 
submitted with the air monitoring data. All data used to calculate 
reported estimates of precision and accuracy including span checks, 
collocated sampler and audit results must be made available to the 
permit granting authority upon request.

                               Table B-1--Minimum PSD Data Assessment Requirements
----------------------------------------------------------------------------------------------------------------
                                                                                                  Parameters
             Method                Assessment method       Coverage            Frequency           reported
----------------------------------------------------------------------------------------------------------------
Precision:
  Automated Methods for SO2,      Response check at   Each analyzer.....  Once per 2 weeks..  Actual
   NO2, O3, and CO.                concentration                                               concentration 2 &
                                   between .08 & .10                                           measured
                                   ppm (8 & 10 ppm                                             concentration.3
                                   for CO) 2.

[[Page 240]]

  TSP, PM10, Lead...............  Collocated          Highest             Once per week or    Two concentration
                                   samplers.           concentration       every 3rd day for   measurements.
                                                       site in             continuous
                                                       monitoring          sampling.
                                                       network.
Accuracy:
  Automated Methods for SO2,      Response check at:  Each analyzer.....  Once per sampling   Actual
   NO2, O3, and CO.                .03-.08 ppm;1,2                         quarter.            concentration2 &
                                   .15-.20 ppm;1,2                                             measured
                                   .35-.45 ppm;1,2                                             (indicated)
                                   .80-.90 ppm;1,2                                             concentration3
                                   (if applicable).                                            for each level.
  TSP, PM10.....................  Sampler flow check  Each sampler......  Once per sampling   Actual flow rate
                                                                           quarter.            and flow rate
                                                                                               indicated by the
                                                                                               sampler.
  Lead..........................  1. Sample flow      1. Each sampler...  1. Once/quarter...  1. Same as for
                                   rate check..       2. Analytical       2. Each quarter Pb   TSP.
                                  2. Check             system.             samples are        2. Actual
                                   analytical system                       analyzed.           concentration &
                                   with Pb audit                                               measured
                                   strips.                                                     concentration of
                                                                                               audit samples
                                                                                               ([mu] g Pb/
                                                                                               strip).
----------------------------------------------------------------------------------------------------------------
\1\ Concentration shown times 100 for CO.
\2\ Effective concentration for open path analyzers.
\3\ Corrected concentration, if applicable, for open path analyzers.

References

    1. Rhodes, R.C. Guideline on the Meaning and Use of Precision and 
Accuracy Data Required by 40 CFR part 58, appendices A and B. EPA-600/4-
83-023. U.S. Environmental Protection Agency, Research Triangle Park, NC 
27711, June, 1983.
    2. ``Quality Assurance Handbook for Air Pollution Measurement 
Systems, Volume I--Principles.'' EPA-600/9-76-005. March 1976. Available 
from U.S Environmental Protection Agency, Atmospheric Research and 
Exposure Assessment Laboratory (MD-77), Research Triangle Park, NC 
27711.
    3. ``Quality Assurance Handbook for Air Pollution Measurement 
Systems, Volume II--Ambient Air Specific Methods.'' EPA-600/4-77-027a. 
May 1979. Available from U.S. Environmental Protection Agency, 
Atmospheric Research and Exposure Assessment Laboratory(MD-77), Research 
Triangle Park, NC 27711.
    4. ``List of Designated Reference and Equivalent Methods.'' 
Available from U.S. Environmental Protection Agency, Department E (MD-
77), Research Triangle Park, NC 27711.
    5. Hughes, E.E. and J. Mandel. A Procedure for Establishing 
Traceability of Gas Mixtures to Certain National Bureau of Standards 
SRM's. EPA-600/7-81-010. U.S. Environmental Protection Agency, Research 
Triangle Park, NC 27711, May, 1981. (Joint NBS/EPA Publication)
    6. 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, Atmospheric Research and Exposure 
Assessment Laboratory (MD-77), Research Triangle Park, NC 27711, 
September, 1979.
    7. McElroy, F.F. Transfer Standards for the Calibration of Ambient 
Air Monitoring Analyzers for Ozone. EPA-600/4-79-056. U.S. Environmental 
Protection Agency, Atmospheric Research and Exposure Assessment 
Laboratory (MD-77), Research Triangle Park, NC 27711, September, 1979.

[44 FR 27571, May 10, 1979; 44 FR 65070, Nov. 9, 1979; 44 FR 72592, Dec. 
14, 1979, as amended at 46 FR 44168, Sept. 3, 1981; 48 FR 2530, Jan. 20, 
1983; 51 FR 9596, Mar. 19, 1986; 52 FR 24741, July 1, 1987; 59 FR 41628, 
41629, Aug. 12, 1994; 60 FR 52321, Oct. 6, 1995]

    Appendix C to Part 58--Ambient Air Quality Monitoring Methodology

1.0 Purpose
    This appendix specifies the monitoring methods (manual methods or 
automated analyzers) which must be used in State ambient air quality 
monitoring stations.

2.0 State and Local Air Monitoring Stations (SLAMS)

    2.1 Except as otherwise provided in this appendix, a monitoring 
method used in a SLAMS must be a reference or equivalent method as 
defined in Sec. 50.1 of this chapter.
    2.2 Substitute PM<INF>10</INF> samplers.
    2.2.1 For purposes of showing compliance with the NAAQS for 
particulate matter, a high volume TSP sampler described in 40 CFR part 
50, appendix B, may be used in a SLAMS in lieu of a PM<INF>10</INF> 
monitor as long as the ambient concentrations of particles measured by 
the TSP sampler are below the PM<INF>10</INF> NAAQS. If the TSP sampler 
measures a single value that is higher than the PM<INF>10</INF> 24-hour 
standard, or if the annual average of its measurements is greater than 
the PM<INF>10</INF> annual standard, the TSP sampler operating as a 
substitute PM<INF>10</INF> sampler must be replaced

[[Page 241]]

with a PM<INF>10</INF> monitor. For a TSP measurement above the 24-hour 
standard, the TSP sampler should be replaced with a PM<INF>10</INF> 
monitor before the end of the calendar quarter following the quarter in 
which the high concentration occurred. For a TSP annual average above 
the annual standard, the PM<INF>10</INF> monitor should be operating by 
June 30 of the year following the exceedance.
    2.2.2 In order to maintain historical continuity of ambient 
particulate matter trends and patterns for PM<INF>10</INF> NAMS that 
were previously TSP NAMS, the TSP high volume sampler must be operated 
concurrently with the PM<INF>10</INF> monitor for a one-year period 
beginning with the PM<INF>10</INF> NAMS start-up date. The operating 
schedule for the TSP sampler must be at least once every 6 days 
regardless of the PM<INF>10</INF> sampling frequency.
    2.3 Any manual method or analyzer purchased prior to cancellation of 
its reference or equivalent method designation under Sec. 53.11 or 
Sec. 53.16 of this chapter may be used in a SLAMS following 
cancellation for a reasonable period of time to be determined by the 
Administrator.
    2.4 Approval of non-designated PM<INF>2.5</INF> methods operated at 
specific individual sites. A method for PM<INF>2.5</INF> that has not 
been designated as a reference or equivalent method as defined in Sec. 
50.1 of this chapter may be approved for use for purposes of section 2.1 
of this appendix at a particular SLAMS under the following stipulations.
    2.4.1 The method must be demonstrated to meet the comparability 
requirements (except as provided in this section 2.4.1) set forth in 
Sec. 53.34 of this chapter in each of the four seasons at the site at 
which it is intended to be used. For purposes of this section 2.4.1, the 
requirements of Sec. 53.34 of this chapter shall apply except as 
follows:
    2.4.1.1 The method shall be tested at the site at which it is 
intended to be used, and there shall be no requirement for tests at any 
other test site.
    2.4.1.2 For purposes of this section 2.4, the seasons shall be 
defined as follows: Spring shall be the months of March, April, and May; 
summer shall be the months of June, July, and August; fall shall be the 
months of September, October, and November; and winter shall be the 
months of December, January, and February; when alternate seasons are 
approved by the Administrator.
    2.4.1.3 No PM<INF>10</INF> samplers shall be required for the test, 
as determination of the PM<INF>2.5</INF>/PM<INF>10</INF> ratio at the 
test site shall not be required.
    2.4.1.4 The specifications given in table C-4 of part 53 of this 
chapter for Class I methods shall apply, except that there shall be no 
requirement for any minimum number of sample sets with Rj greater than 
40 [mu]g/m<SUP>3</SUP> for 24-hour samples or greater than 15 [mu]g/
m<INF>3</INF> average concentration collected over a 48-hour period.
    2.4.2 The monitoring agency wishing to use the method must develop 
and implement appropriate quality assurance procedures for the method.
    2.4.3 The monitoring agency wishing to use the method must develop 
and implement appropriate procedures for assessing and reporting the 
precision and accuracy of the method comparable to the procedures set 
forth in appendix A of this part for designated reference and equivalent 
methods.
    2.4.4 The assessment of network operating precision using collocated 
measurements with reference method ``audit'' samplers required under 
section 3 of appendix A of this part shall be carried out semi-annually 
rather than annually (i.e., monthly audits with assessment 
determinations each 6 months).
    2.4.5 Requests for approval under this section 2.4 must meet the 
general submittal requirements of sections 2.7.1 and 2.7.2.1 of this 
appendix and must include the requirements in sections 2.4.5.1 through 
2.4.5.7 of this appendix.
    2.4.5.1 A clear and unique description of the site at which the 
method or sampler will be used and tested, and a description of the 
nature or character of the site and the particulate matter that is 
expected to occur there.
    2.4.5.2 A detailed description of the method and the nature of the 
sampler or analyzer upon which it is based.
    2.4.5.3 A brief statement of the reason or rationale for requesting 
the approval.
    2.4.5.4 A detailed description of the quality assurance procedures 
that have been developed and that will be implemented for the method.
    2.4.5.5 A detailed description of the procedures for assessing the 
precision and accuracy of the method that will be implemented for 
reporting to AIRS.
    2.4.5.6 Test results from the comparability tests as required in 
section 2.4.1 through 2.4.1.4 of this appendix.
    2.4.5.7 Such further supplemental information as may be necessary or 
helpful to support the required statements and test results.
    2.4.6 Within 120 days after receiving a request for approval of the 
use of a method at a particular site under this section 2.4 and such 
further information as may be requested for purposes of the decision, 
the Administrator will approve or disapprove the method by letter to the 
person or agency requesting such approval.
    2.5 Approval of non-designated methods under Sec. 58.13(f). An 
automated (continuous) method for PM<INF>2.5</INF> that is not 
designated as either a reference or equivalent method as defined in 
Sec. 50.1 of this chapter may be approved under Sec. 58.13(f) for use 
at a SLAMS for the limited purposes of Sec. 58.13(f). Such an analyzer 
that is approved for use at a SLAMS under Sec. 58.13(f), identified as 
correlated acceptable continuous (CAC) monitors, shall

[[Page 242]]

not be considered a reference or equivalent method as defined in Sec. 
50.1 of this chapter by virtue of its approval for use under Sec. 
58.13(f), and the PM<INF>2.5</INF> monitoring data obtained from such a 
monitor shall not be otherwise used for purposes of part 50 of this 
chapter.
    2.6 Use of Methods With Higher, Nonconforming Ranges in Certain 
Geographical Areas.
    2.6.1 [Reserved]
    2.6.2 Nonconforming Ranges. 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 must meet the 
submittal requirements of section 2.7. Except as provided in subsection 
2.7.3, each request must contain the information specified in subsection 
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 subsection 2.7.2.2 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.
    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 sections 2.4, 2.6.2, or 2.8 of 
this appendix must be submitted to: Director, National Exposure 
Assessment Laboratory, Department E, (MD-77B), U.S. Environmental 
Protection Agency, Research Triangle Park, North Carolina 27711.
    2.7.2 Except as provided in section 2.7.3, 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 Sec. 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 sections 2.4, 
2.5, or 2.6, 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 
information available to him, that any of the determinations or 
statements on which approval of a request under this section (2.7) was 
based are invalid or no longer valid, or that the requirements of 
section 2.4, 2.5, or 2.6, as applicable, have not been met, he 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 (2.8), no 
reference method, equivalent method, or alternative method may be used 
in a SLAMS if it has been modified in a manner that will, or might, 
significantly alter

[[Page 243]]

the performance characteristics of the method without prior approval by 
the Administrator. For purposes of this section (2.8), ``alternative 
method'' means an analyzer the use of which has been approved under 
section 2.4, 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 Within 75 days after receiving a request for approval under 
this section (2.8) and such further information as he may request for 
purposes of his decision, the Administrator will approve or disapprove 
the modification in question by letter to the person or agency 
requesting such approval.
    2.8.5 A temporary modification that will or might alter the 
performance characteristics of a reference, equivalent, or alternative 
method may be made without prior approval under this section (2.8) 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, 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 Sec. 58.28 or Sec. 58.35 of this chapter and must be accompanied 
by a report containing the information specified in section 2.8.3. A 
request that the Administrator approve a temporary modification may be 
submitted in accordance with sections 2.8.1 through 2.8.4. 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. ``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. These samplers 
are routinely operated at about 70 locations in the United States. 
IMPROVE samplers consist of four sampling modules that are used to 
collect twice weekly 24-hour duration simultaneous samples. Modules A, 
B, and C collect PM<INF>2.5</INF> on three different filter substrates 
that are compatible with a variety of analytical techniques, and module 
D collects a PM<INF>10</INF> sample. PM<INF>2.5</INF> mass and elemental 
concentrations are determined by analysis of the 25mm diameter stretched 
Teflon filters from module A. More complete descriptions of the IMPROVE 
samplers and the data they collect are available elsewhere (references 
4, 5, and 6 of this appendix).

3.0 National Air Monitoring Stations (NAMS)

    3.1 Methods used in those SLAMS which are also designated as NAMS to 
measure SO<INF>2</INF>, CO, NO<INF>2</INF>, or O<INF>3</INF> must be 
automated reference or equivalent methods (continuous analyzers).

4.0 Photochemical Assessment Monitoring Stations (PAMS)

    4.1 Methods used for O<INF>3</INF> monitoring at PAMS must be 
automated reference or equivalent methods as defined in Sec. 50.1 of 
this chapter.
    4.2 Methods used for NO, NO<INF>2</INF> and NO<INF>X</INF> 
monitoring at PAMS should be automated reference or equivalent methods 
as defined for NO<INF>2</INF> in Sec. 50.1 of this chapter. If 
alternative NO, NO<INF>2</INF> or NO<INF>X</INF> monitoring 
methodologies are proposed, such techniques must be detailed in the 
network description required by Sec. 58.40 and subsequently approved by 
the Administrator.
    4.3 Methods for meteorological measurements and speciated VOC 
monitoring are included in the guidance provided in references 2 and 3. 
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 
Sec. 58.40 and subsequently approved by the Administrator.

    5.0 Particulate Matter Episode Monitoring

    5.1 For short-term measurements of PM<INF>10</INF> during air 
pollution episodes (see Sec. 51.152 of this chapter) the measurement 
method must be:
    5.1.1 Either the ``Staggered PM<INF>10</INF>'' method or the 
``PM<INF>10</INF> Sampling Over Short Sampling Times'' method, both of 
which are based on the reference method for PM<INF>10</INF> and are 
described in reference 1: or
    5.1.2 Any other method for measuring PM<INF>10</INF>:

[[Page 244]]

    5.1.2.1 Which has a measurement range or ranges appropriate to 
accurately measure air pollution episode concentration of 
PM<INF>10</INF>,
    5.1.2.2 Which has a sample period appropriate for short-term 
PM<INF>10</INF> measurements, and
    5.1.2.3 For which a quantitative relationship to a reference or 
equivalent method for PM<INF>10</INF> has been established at the use 
site. Procedures for establishing a quantitative site-specific 
relationship are contained in reference 1.
    5.2 Quality Assurance. PM<INF>10</INF> methods other than the 
reference method are not covered under the quality assessment 
requirements of appendix A. Therefore, States must develop and implement 
their own quality assessment procedures for those methods allowed under 
this section 4. These quality assessment procedures should be similar or 
analogous to those described in section 3 of appendix A for the 
PM<INF>10</INF> reference method.

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., 
Measurements of fine particles and their chemical components in the 
IMPROVE/NPS networks, in Transactions of the International Specialty 
Conference on Visibility and Fine Particles, Air and Waste Management 
Association: Pittsburgh, PA, 1990; pp 187-196.
    (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.

[44 FR 27571, May 10, 1979, as amended at 44 FR 37918, June 29, 1979; 44 
FR 65070, Nov. 9, 1979; 51 FR 9597, Mar. 19, 1986; 52 FR 24741, 24742, 
July 1, 1987; 58 FR 8469, Feb. 12, 1993; 59 FR 41628, Aug. 12, 1994; 62 
FR 38843, July 18, 1997]

Appendix D to Part 58--Network Design for State and Local Air Monitoring 
     Stations (SLAMS), National Air Monitoring Stations (NAMS), and 
           Photochemical Assessment Monitoring Stations (PAMS)

    1. SLAMS Monitoring Objectives and Spatial Scales
    2. SLAMS Network Design Procedures
    2.1 Background Information for Establishing SLAMS
    2.2 Substantive Changes in SLAMS/NAMS Network Design Elements
    2.3 Sulfur Dioxide (SO<INF>2</INF>) Design Criteria for SLAMS
    2.4 Carbon Monoxide (CO) Design Criteria for SLAMS
    2.5 Ozone (O<INF>3</INF>) Design Criteria for SLAMS
    2.6 Nitrogen Dioxide (NO<INF>2</INF>) Design Criteria for SLAMS
    2.7 Lead (Pb) Design Criteria for SLAMS
    2.8 Particluate Matter Design Criteria for SLAMS
    3. Network Design for National Air Monitoring Stations (NAMS)
    3.1 [Reserved]
    3.2 Sulfur Dioxide (SO<INF>2</INF>) Design Criteria for NAMS
    3.3 Carbon Monoxide (CO) Design Criteria for NAMS
    3.4 Ozone (O<INF>3</INF>) Design Criteria for NAMS
    3.5 Nitrogen Dioxide (NO<INF>2</INF>) Design Criteria for NAMS
    3.6 Lead (Pb) Design Criteria for NAMS
    3.7 Particulate Matter Design Criteria for NAMS
    4. Network Design for Photochemical Assessment Monitoring Stations 
(PAMS)
    5. Summary
    6. References

    1. SLAMS Monitoring Objectives and Spatial Scales

    The purpose of this appendix is to describe monitoring objectives 
and general criteria to be applied in establishing the State and Local 
Air Monitoring Stations (SLAMS) networks and for choosing general 
locations for new monitoring stations. It also describes criteria for 
determining the number and location of National Air Monitoring Stations 
(NAMS), Photochemical Assessment Monitoring Stations (PAMS), and core 
Stations for PM<INF>2.5</INF>. These criteria will also be used by EPA 
in evaluating the adequacy of the

[[Page 245]]

SLAMS/NAMS/PAMS and core PM<INF>2.5</INF> networks.
    The network of stations that comprise SLAMS should be designed to 
meet a minimum of six basic monitoring objectives. These basic 
monitoring objectives are:
    (1) To determine highest concentrations expected to occur in the 
area covered by the network.
    (2) To determine representative concentrations in areas of high 
population density.
    (3) To determine the impact on ambient pollution levels of 
significant sources or source categories.
    (4) To determine general background concentration levels.
    (5) To determine the extent of Regional pollutant transport among 
populated areas; and in support of secondary standards.
    (6) To determine the welfare-related impacts in more rural and 
remote areas (such as visibility impairment and effects on vegetation).
    It should be noted that this appendix contains no criteria for 
determining the total number of stations in SLAMS networks, except in 
areas where Pb concentrations currently exceed or have exceeded the Pb 
NAAQS during any one quarter of the most recent eight quarters. The 
optimum size of a particular SLAMS network involves trade offs among 
data needs and available resources that EPA believes can best be 
resolved during the network design process.
    This appendix focuses on the relationship between monitoring 
objectives and the geographical location of monitoring stations. 
Included are a rationale and set of general criteria for identifying 
candidate station locations in terms of physical characteristics which 
most closely match a specific monitoring objective. The criteria for 
more specifically siting the monitoring station, including spacing from 
roadways and vertical and horizontal probe and path placement, are 
described in appendix E of this part.
    To clarify the nature of the link between general monitoring 
objectives and the physical location of a particular monitoring station, 
the concept of spatial scale of representativeness of a monitoring 
station is defined. The goal in siting stations is to correctly match 
the spatial scale represented by the sample of monitored air with the 
spatial scale most appropriate for the monitoring objective of the 
station.
    Thus, spatial scale of representativeness is described in terms of 
the physical dimensions of the air parcel nearest to a monitoring 
station throughout which actual pollutant concentrations are reasonably 
similar. The scale of representativeness of most interest for the 
monitoring objectives defined above are as follows:
    Microscale--defines the concentrations in air volumes associated 
with area dimensions ranging from several meters up to about 100 meters.
    Middle Scale--defines the concentration typical of areas up to 
several city blocks in size with dimensions ranging from about 100 
meters to 0.5 kilometer.
    Neighborhood Scale--defines concentrations within some extended area 
of the city that has relatively uniform land use with dimensions in the 
0.5 to 4.0 kilometers range.
    Urban Scale--defines the overall, citywide conditions with 
dimensions on the order of 4 to 50 kilometers. This scale would usually 
require more than one site for definition.
    Regional Scale--defines usually a rural area of reasonably 
homogeneous geography and extends from tens to hundreds of kilometers.
    National and Global Scales--these measurement scales represent 
concentrations characterizing the nation and the globe as a whole.
    Proper siting of a monitoring station requires precise specification 
of the monitoring objective which usually includes a desired spatial 
scale of representativeness. For example, consider the case where the 
objective is to determine maximum CO concentrations in areas where 
pedestrians may reasonably be exposed. Such areas would most likely be 
located within major street canyons of large urban areas and near 
traffic corridors. Stations located in these areas are most likely to 
have a microscale of representativeness since CO concentrations 
typically peak nearest roadways and decrease rapidly as the monitor is 
moved from the roadway. In this example, physical location was 
determined by consideration of CO emission patterns, pedestrian 
activity, and physical characteristics affecting pollutant dispersion. 
Thus, spatial scale of representativeness was not used in the selection 
process but was a result of station location.
    In some cases, the physical location of a station is determined from 
joint consideration of both the basic monitoring objective, and a 
desired spatial scale of representativeness. For example, to determine 
CO concentrations which are typical over a reasonably broad geographic 
area having relatively high CO concentrations, a neighborhood scale 
station is more appropriate. Such a station would likely be located in a 
residential or commercial area having a high overall CO emission density 
but not in the immediate vicinity of any single roadway. Note that in 
this example, the desired scale of representativeness was an important 
factor in determining the physical location of the monitoring station.
    In either case, classification of the station by its intended 
objective and spatial scale of representativeness is necessary and will 
aid in interpretation of the monitoring data.
    Table 1 illustrates the relationship between the four basic 
monitoring objectives and the scales of representativeness that are

[[Page 246]]

generally most appropriate for that objective.

     Table 1--Relationship Among Monitoring Objectives and Scale of
                           Representativeness
------------------------------------------------------------------------
           Monitoring Objective               Appropriate Siting Scales
------------------------------------------------------------------------
Highest concentration.....................  Micro, Middle, neighborhood
                                             (sometimes urban \1\)
Population................................  Neighborhood, urban
Source impact.............................  Micro, middle, neighborhood
General/background........................  Neighborhood, urban,
                                             regional
Regional transport........................  Urban/regional
Welfare-related impacts...................  Urban/regional
------------------------------------------------------------------------
\1\ Urban denotes a geographic scale applicable to both cities and rural
  areas

    Open path analyzers can often be used effectively and advantageously 
to provide better monitoring representation for population exposure 
monitoring and general or background monitoring in urban and 
neighborhood scales of representation. Such analyzers may also be able 
to provide better area coverage or operational advantages in high 
concentration and source-impact monitoring in middle scale and possibly 
microscale areas. However, siting of open path analyzers for the latter 
applications must be carried out with proper regard for the specific 
monitoring objectives and for the path-averaging nature of these 
analyzers. Monitoring path lengths need to be commensurate with the 
intended scale of representativeness and located carefully with respect 
to local sources or potential obstructions. For short-term/high-
concentration or source-oriented monitoring, the monitoring path may 
need to be further restricted in length and be oriented approximately 
radially with respect to the source in the downwind direction, to 
provide adequate peak concentration sensitivity. Alternatively, multiple 
(e.g., orthogonal) paths may be used advantageously to obtain both wider 
area coverage and peak concentration sensitivity. Further discussion on 
this topic is included in section 2.2 of this appendix.
    Subsequent sections of this appendix describe in greater detail the 
most appropriate scales of representativeness and general monitoring 
locations for each pollutant.

2. SLAMS Network Design Procedures

    The preceding section of this appendix has stressed the importance 
of defining the objectives for monitoring a particular pollutant. Since 
monitoring data are collected to ``represent'' the conditions in a 
section or subregion of a geographical area, the previous section 
included a discussion of the scale of representativeness of a monitoring 
station. The use of this physical basis for locating stations allows for 
an objective approach to network design.
    The discussion of scales in sections 2.3 through 2.8 of this 
appendix does not include all of the possible scales for each pollutant. 
The scales that are discussed are those that are felt to be most 
pertinent for SLAMS network design.
    In order to evaluate a monitoring network and to determine the 
adequacy of particular monitoring stations, it is necessary to examine 
each pollutant monitoring station individually by stating its monitoring 
objective and determining its spatial scale of representativeness. This 
will do more than insure compatibility among stations of the same type. 
It will also provide a physical basis for the interpretation and 
application of the data. This will help to prevent mismatches between 
what the data actually represent and what the data are interpreted to 
represent. It is important to note that SLAMS are not necessarily 
sufficient for completely describing air quality. In many situations, 
diffusion models must be applied to complement ambient monitoring, e.g., 
determining the impact of point sources or defining boundaries of 
nonattainment areas.
    Information such as emissions density, housing density, 
climatological data, geographic information, traffic counts, and the 
results of modeling will be useful in designing regulatory networks. Air 
pollution control agencies have shown the value of screening studies, 
such as intensive studies conducted with portable samplers, in designing 
networks. In many cases, in selecting sites for core PM<INF>2.5</INF> or 
carbon monoxide SLAMS, and for defining the boundaries of 
PM<INF>2.5</INF> optional community monitoring zones, air pollution 
control agencies will benefit from using such studies to evaluate the 
spatial distribution of pollutants.
    2.1 Background Information for Establishing SLAMS. Background 
information that must be considered in the process of selecting SLAMS 
from the existing network and in establishing new SLAMS includes 
emission inventories, climatological summaries, and local geographical 
characteristics. Such information is to be used as a basis for the 
judgmental decisions that are required during the station selection 
process. For new stations, the background information should be used to 
decide on the actual location considering the monitoring objective and 
spatial scale while following the detailed procedures in References 1 
through 4.
    Emission inventories are generally the most important type of 
background information needed to design the SLAMS network. The emission 
data provide valuable information concerning the size and distribution 
of large point sources. Area source emissions are usually available for 
counties but should be subdivided into smaller areas or grids where 
possible, especially if diffusion modeling is to be used as a basis for 
determining where stations should be located. Sometimes

[[Page 247]]

this must be done rather crudely, for example, on the basis of 
population or housing units. In general, the grids should be smaller in 
areas of dense population than in less densely populated regions.
    Emission inventory information for point sources should be generally 
available for any area of the country for annual and seasonal averaging 
times. Specific information characterizing the emissions from large 
point sources for the shorter averaging times (diurnal variations, load 
curves, etc.) can often be obtained from the source. Area source 
emission data by season, although not available from the EPA, can be 
generated by apportioning annual totals according to degree days.
    Detailed area source data are also valuable in evaluating the 
adequacy of an existing station in terms of whether the station has been 
located in the desired spatial scale of representativeness. For example, 
it may be the desire of an agency to have an existing CO station 
measuring in the neighborhood scale.
    By examining the traffic data for the area and examining the 
physical location of the station with respect to the roadways, a 
determination can be made as to whether or not the station is indeed 
measuring the air quality on the desired scale.
    The climatological summaries of greatest use are the frequency 
distributions of wind speed and direction. The wind rose is an easily 
interpreted graphical presentation of the directional frequencies. Other 
types of useful climatological data are also available, but generally 
are not as directly applicable to the site selection process as are the 
wind statistics.
    In many cases, the meteorological data originating from the most 
appropriate (not necessarily the nearest) national weather service (NWS) 
airport station in the vicinity of the prospective siting area will 
adequately reflect conditions over the area of interest, at least for 
annual and seasonal averaging times. In developing data in complex 
meteorological and terrain situations, diffusion meteorologists should 
be consulted. NWS stations can usually provide most of the relevant 
weather information in support of network design activities anywhere in 
the country. Such information includes joint frequency distributions of 
winds and atmospheric stability (stability-wind roses).
    The geographical material is used to determine the distribution of 
natural features, such as forests, rivers, lakes, and manmade features. 
Useful sources of such information may include road and topographical 
maps, aerial photographs, and even satellite photographs. This 
information may include the terrain and land-use setting of the 
prospective monitor siting area, the proximity of larger water bodies, 
the distribution of pollutant sources in the area, the location of NWS 
airport stations from which weather data may be obtained, etc. Land use 
and topographical characteristics of specific areas of interest can be 
determined from U.S. Geological Survey (USGS) maps and land use maps. 
Detailed information on urban physiography (building/street dimensions, 
etc.) can be obtained by visual observations, aerial photography, and 
also surveys to supplement the information available from those sources. 
Such information could be used in determining the location of local 
pollutant sources in and around the prospective station locations.
    2.2 Substantive Changes in SLAMS/NAMS Network Design Elements. Two 
important purposes of the SLAMS monitoring data are to examine and 
evaluate overall air quality within a certain region, and to assess the 
trends in air pollutant levels over several years. The EPA believes that 
one of the primary tools for providing these characterizations is an 
ambient air monitoring program which implements technically 
representative networks. The design of these networks must be carefully 
evaluated not only at their outset, but at relatively frequent intervals 
thereafter, using an appropriate combination of other important 
technical tools, including: dispersion and receptor modeling, saturation 
studies, point and area source emissions analyses, and meteorological 
assessments. The impetus for these subsequent reexaminations of 
monitoring network adequacy stems not only from the need to evaluate the 
effect that changes in the environment may pose, but also from the 
recognition that new and/or refined tools and techniques for use in 
impact assessments are continually emerging and available for 
application.
    Substantiative changes to an ambient air monitoring network are both 
inevitable and necessary; however, any changes in any substantive aspect 
of an existing SLAMS network or monitoring site that might affect the 
continuity or comparability of pollutant measurements over time must be 
carefully and thoroughly considered. Such substantive changes would 
include cessation of monitoring at an existing site, relocation of an 
existing site, a change in the type of monitoring method used, any 
change in the probe or path height or orientation that might affect 
pollutant measurements, any significant changes in calibration 
procedures or standards, any significant change in operational or 
quality assurance procedures, any significant change in the sources or 
the character of the area in the vicinity of a monitoring site, or any 
other change that could potentially affect the continuity or 
comparability of monitoring data obtained before and after the change.
    In general, these types of changes should be made cautiously with 
due consideration given to the impact of such changes on the

[[Page 248]]

network/site's ability to meet its intended goals. Some of these changes 
will be inevitable (such as when a monitoring site will no longer be 
available and the monitor must be relocated, for example). Other changes 
may be deemed necessary and advantageous, after due consideration of 
their impact, even though they may have a deleterious effect on the 
long-term comparability of the monitoring data. In these cases, an 
effort should be made to quantify, if possible, or at least 
characterize, the nature or extent of the effects of the change on the 
monitoring data. In all cases, the changes and all information pertinent 
to the effect of the change should be properly and completely documented 
for evaluation by trends analysts.
    The introduction of open path methods to the SLAMS monitoring 
network may seem relatively straightforward, given the kinds of 
technical analyses required in this appendix. However, given the 
uncertainties attendant to these analyses and the critical nature and 
far-reaching regulatory implications of some sites in the current SLAMS 
network composed of point monitors, there is a need to `bridge' between 
databases generated by these different candidate methods to evaluate and 
promote continuity in understanding of the historical representativeness 
of the database.
    Concurrent, nominally collocated monitoring must be conducted in all 
instances where an open path analyzer is effectively intended to replace 
a criteria pollutant point monitor which meets either of the following:
    1. Data collected at the site represents the maximum concentration 
for a particular nonattainment area; or
    2. Data collected at the site is currently used to characterize the 
development of a nonattainment area State implementation plan.
    The Regional Administrator, the Administrator, or their appropriate 
designee may also require collocated monitoring at other sites which 
are, based on historical technical data, significant in assessing air 
quality in a particular area. The term of this requirement is determined 
by the Regional Administrator (for SLAMS), Administrator (for NAMS), or 
their appropriate designee. The recommended minimum term consists of one 
year (or one season of maximum pollutant concentration) with a maximum 
term indexed to the subject pollutant NAAQS compliance interval (e.g., 
three calendar years for ozone). The requirement involves concurrent 
monitoring with both the open path analyzer and the existing point 
monitor during this term. Concurrent monitoring with more than one point 
analyzer with an open path analyzer using one or more measurement paths 
may also be advantageous to confirm adequate peak concentration 
sensitivity or to optimize the location and length of the monitoring 
path or paths.
    All or some portion of the above requirement may be waived by the 
Regional Administrator (for SLAMS), the Administrator (for NAMS), or 
their designee in response to a request, based on accompanying technical 
information and analyses, or in certain unavoidable instances caused by 
logistical circumstances.
    These requirements for concurrent monitoring also generally apply to 
situations where the relocation of any SLAMS site, using either a point 
monitor or an open path analyzer, within an area is being contemplated.
    2.3 Sulfur Dioxide (SO<INF>2</INF>) Design Criteria for SLAMS. The 
spatial scales for SO<INF>2</INF> SLAMS monitoring are the middle, 
neighborhood, urban, and regional scales. Because of the nature of 
SO<INF>2</INF> distributions over urban areas, the middle scale is the 
most likely scale to be represented by a single measurement in an urban 
area, but only if the undue effects from local sources (minor or major 
point sources) can be eliminated. Neighborhood scales would be those 
most likely to be represented by single measurements in suburban areas 
where the concentration gradients are less steep. Urban scales would 
represent areas where the concentrations are uniform over a larger 
geographical area. Regional scale measurements would be associated with 
rural areas.
    Middle Scale--Some data uses associated with middle scale 
measurements for SO<INF>2</INF> include assessing the effects of control 
strategies to reduce urban concentrations (especially for the 3-hour and 
24-hour averaging times) and monitoring air pollution episodes.
    Neighborhood Scale--This scale applies in areas where the 
SO<INF>2</INF> concentration gradient is relatively flat (mainly 
suburban areas surrounding the urban center) or in large sections of 
small cities and towns. In general, these areas are quite homogeneous in 
terms of SO<INF>2</INF> emission rates and population density. Thus, 
neighborhood scale measurements may be associated with baseline 
concentrations in areas of projected growth and in studies of population 
responses to exposure to SO<INF>2</INF>. Also concentration maxima 
associated with air pollution episodes may be uniformly distributed over 
areas of neighborhood scale, and measurements taken within such an area 
would represent neighborhood, and to a limited extent, middle scale 
concentrations.
    Urban Scale--Data from this scale could be used for the assessment 
of air quality trends and the effect of control strategies on urban 
scale air quality.
    Regional Scale--These measurements would be applicable to large 
homogeneous areas, particularly those which are sparsely populated. Such 
measurements could provide information on background air quality and 
interregional pollutant transport.

[[Page 249]]

    After the spatial scale has been selected to meet the monitoring 
objectives for each station location, the procedures found in reference 
2 should be used to evaluate the adequacy of each existing 
SO<INF>2</INF> station and must be used to relocate an existing station 
or to locate any new SLAMS stations. The background material for these 
procedures should consist of emission inventories, meteorological data, 
wind roses, and maps for population and topographical characteristics of 
specific areas of interest. Isopleth maps of SO<INF>2</INF> air quality 
as generated by diffusion models\5\ are useful for the general 
determination of a prospective area within which the station is 
eventually placed.
    2.4 Carbon Monoxide (CO) Design Criteria for SLAMS. Micro, middle, 
and neighborhood scale measurements are necessary station 
classifications for SLAMS since most people are exposed to CO 
concentrations in these scales. Carbon monoxide maxima occur primarily 
in areas near major roadways and intersections with high traffic density 
and poor atmospheric ventilation. As these maxima can be predicted by 
ambient air quality modeling, a large fixed network of CO monitors is 
not required. Long-term CO monitoring should be confined to a limited 
number of micro and neighborhood scale stations in large metropolitan 
areas to measure maximum pollution levels and to determine the 
effectiveness of control strategies.
    Microscale--Measurements on this scale would represent distributions 
within street canyons, over sidewalks, and near major roadways. The 
measurements at a particular location in a street canyon would be 
typical of one high concentration area which can be shown to be a 
representation of many more areas throughout the street canyon or other 
similar locations in a city. This is a scale of measurement that would 
provide valuable information for devising and evaluating ``hot spot'' 
control measures.
    Middle Scale--This category covers dimensions from 100 meters to 0.5 
kilometer. In certain cases discussed below, it may apply to regions 
that have a total length of several kilometers. In many cases of 
interest, sources and land use may be reasonably homogeneous for long 
distances along a street, but very inhomogeneous normal to the street. 
This is the case with strip development and freeway corridors. Included 
in this category are measurements to characterize the CO concentrations 
along the urban features just enumerated. When a location is chosen to 
represent conditions in a block of street development, then the 
characteristic dimensions of this scale are tens of meters by hundreds 
of meters. If an attempt is made to characterize street-side conditions 
throughout the downtown area or along an extended stretch of freeway, 
the dimensions may be tens of meters by kilometer.
    The middle scale would also include the parking lots and feeder 
streets associated with indirect sources which attract significant 
numbers of pollutant emitters, particularly autos. Shopping centers, 
stadia, and office buildings are examples of indirect sources.
    Neighborhood Scale--Measurements in this category would represent 
conditions throughout some reasonably homogeneous urban subregions, with 
dimensions of a few kilometers and generally more regularly shaped than 
the middle scale. Homogeneity refers to CO concentration, but it 
probably also applies to land use. In some cases, a location carefully 
chosen to provide neighborhood scale data, might represent not only the 
immediate neighborhood, but also neighborhoods of the same type in other 
parts of the city. These kinds of stations would provide information 
relating to health effects because they would represent conditions in 
areas where people live and work. Neighborhood scale data would provide 
valuable information for developing, testing, and revising concepts and 
models that describe the larger scale concentration patterns, especially 
those models relying on spatially smoothed emission fields for inputs. 
These types of measurements could also be used for interneighborhood 
comparisons within or between cities.
    After the spatial scale has been determined to meet the monitoring 
objectives for each location, the location selection procedures, as 
shown in reference 3 should be used to evaluate the adequacy of each 
existing CO station and must be used to relocate an existing station or 
to locate any new SLAMS stations. The background material necessary for 
these procedures may include the average daily traffic on all streets in 
the area, wind roses for different hours of the day, and maps showing 
one-way streets, street widths, and building heights. If the station is 
to typify the area with the highest concentrations, the streets with the 
greatest daily traffic should be identified. If some streets are one-
way, those streets that have the greatest traffic during the afternoon 
and evening hours should be selected as tentative locations, because the 
periods of high traffic volume are usually of greatest duration through 
the evening hours. However, the strength of the morning inversion has to 
be considered along with the traffic volume and pattern when seeking 
areas with the highest concentrations. Traffic counters near the 
stations will provide valuable data for interpreting the observed CO 
Concentrations.
    Monitors should not be placed in the vicinity of possible anomalous 
source areas. Examples of such areas include toll gates on turnpikes, 
metered freeway ramps, and drawbridge approaches. Additional information 
on network design may be found in reference 3.

[[Page 250]]

    2.5 Ozone (O<INF>3</INF>) Design Criteria for SLAMS. Ozone is not 
directly emitted into the atmosphere but results from complex 
photochemical reactions involving organic compounds, oxides of nitrogen, 
and solar radiation.
    The relationships between primary emissions (precursors) and 
secondary pollutants (O<INF>3</INF>) tend to produce large separations 
spatially and temporally between the major sources and the areas of high 
oxidant pollution. This suggests that the meteorological transport 
process and the relationships between sources and sinks need to be 
considered in the development of the network design criteria and 
placement of monitoring stations, especially in measuring peak 
concentration levels.
    The principal spatial scales for SLAMS purposes based on the 
monitoring objectives are neighborhood, urban, regional, and to a lesser 
extent, middle scale. Since ozone requires appreciable formation time, 
the mixing of reactants and products occurs over large volumes of air, 
and this reduces the importance of monitoring small scale spatial 
variability.
    Middle Scale--Measurement in this scale would represent conditions 
close to sources of NO<INF>X</INF> such as roads where it would be 
expected that suppression of O<INF>3</INF> concentrations would occur. 
Trees also may have a strong scavenging effect on O<INF>3</INF> and may 
tend to suppress O<INF>3</INF> concentrations in their immediate 
vicinity. Measurements at these stations would represent conditions over 
relatively small portions of the urban area.
    Neighborhood Scale--Measurements in this category represent 
conditions throughout some reasonably homogeneous urban subregion, with 
dimensions of a few kilometers. Homogeneity refers to pollutant 
concentrations. Neighborhood scale data will provide valuable 
information for developing, testing, and revising concepts and models 
that describe urban/regional concentration patterns. They will be useful 
to the understanding and definition of processes that take periods of 
hours to occur and hence involve considerable mixing and transport. 
Under stagnation conditions, a station located in the neighborhood scale 
may also experience peak concentration levels within the urban areas.
    Urban Scale--Measurement in this scale will be used to estimate 
concentrations over large portions of an urban area with dimensions of 
several kilometers to 50 or more kilometers. Such measurements will be 
used for determining trends, and designing area-wide control strategies. 
The urban scale stations would also be used to measure high 
concentrations downwind of the area having the highest precursor 
emissions.
    Regional Scale--This scale of measurement will be used to typify 
concentrations over large portions of a metropolitan area and even 
larger areas with dimensions of as much as hundreds of kilometers. Such 
measurements will be useful for assessing the ozone that is transported 
into an urban area. Data from such stations may be useful in accounting 
for the ozone that cannot be reduced by control strategies in that urban 
area.
    The location selection procedure continues after the spatial scale 
is selected based on the monitoring objectives. The appropriate network 
design procedures as found in reference 4, should be used to evaluate 
the adequacy of each existing O<INF>3</INF> monitor and must be used to 
relocate an existing station or to locate any new O<INF>3</INF> SLAMS 
stations. The first step in the siting procedure would be to collect the 
necessary background material, which may consist of maps, emission 
inventories for nonmethane hydrocarbons and oxides of nitrogen 
(NO<INF>X</INF>), climatological data, and existing air quality data for 
ozone, nonmethane hydrocarbons, and NO<INF>2</INF>/NO.
    For locating a neighborhood scale station 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<INF>X</INF> sources. For an urban scale station to 
measure the high concentration areas, the emission inventories should be 
used to define the extent of the area of important nonmethane 
hydrocarbons and NO<INF>X</INF> emissions. The most frequent wind speed 
and direction for periods of important photochemical activity should be 
determined. Then the prospective monitoring area should be selected in a 
direction from the city that is most frequently downwind during periods 
of photochemical activity. The distance from the station to the upwind 
edge of the city should be about equal to the distance traveled by air 
moving for 5 to 7 hours at wind speeds prevailing during periods of 
photochemical activity. Prospective areas for locating O<INF>3</INF> 
monitors should always be outside the area of major NO<INF>X</INF>.
    In locating a neighborhood scale station which is to measure high 
concentrations, the same procedures used for the urban scale are 
followed except that the station should be located closer to the areas 
bordering on the center city or slightly further downwind in an area of 
high density population.
    For regional scale background monitoring stations, the most frequent 
wind associated with important photochemical activity should be 
determined. The prospective monitoring area should be upwind for the 
most frequent direction and outside the area of city influence.
    Since ozone levels decrease significantly in the colder parts of the 
year in many areas, ozone is required to be monitored at NAMS and SLAMS 
monitoring sites only during the ``ozone season'' as designated in the 
AIRS

[[Page 251]]

files on a State by State basis and described below:

                    Ozone Monitoring Season By State
------------------------------------------------------------------------
              State                   Begin month          End month
------------------------------------------------------------------------
Alabama.........................  March.............  October.
Alaska..........................  April.............  October.
Arizona.........................  January...........  December.
Arkansas........................  March.............  November.
California......................  January...........  December.
Colorado........................  March.............  September.
Connecticut.....................  April.............  September.
Delaware........................  April.............  October.
District of Columbia............  April.............  October.
Florida.........................  March.............  October.
Georgia.........................  March.............  October.
Hawaii..........................  January...........  December.
Idaho...........................  April.............  October.
Illinois........................  April.............  October.
Indiana.........................  April.............  September.
Iowa............................  April.............  October.
Kansas..........................  April.............  October.
Kentucky........................  March.............  October.
Louisiana AQCRs 019, 022........  March.............  October.
Louisiana AQCR 106..............  January...........  December.
Maine...........................  April.............  September.
Maryland........................  April.............  October.
Massachusetts...................  April.............  September.
Michigan........................  April.............  September.
Minnesota.......................  April.............  October.
Mississippi.....................  March.............  October.
Missouri........................  April.............  October.
Montana.........................  June..............  September.
Nebraska........................  April.............  October.
Nevada..........................  January...........  December.
New Hampshire...................  April.............  September.
New Jersey......................  April.............  October.
New Mexico......................  January...........  December.
New York........................  April.............  October.
North Carolina..................  April.............  October.
North Dakota....................  May...............  September.
Ohio............................  April.............  October.
Oklahoma........................  March.............  November.
Oregon..........................  May...............  September.
Pennsylvania....................  April.............  October.
Puerto Rico.....................  January...........  December.
Rhode Island....................  April.............  September.
South Carolina..................  April.............  October.
South Dakota....................  June..............  September.
Tennessee.......................  March.............  October.
Texas AQCR 4,5,7,10,11..........  January...........  December
Texas AQCR 1, 2, 3, 6, 8, 9, 12.  March.............  October
Utah............................  May...............  September.
Vermont.........................  April.............  September.
Virginia........................  April.............  October.
Washington......................  May...............  September.
West Virginia...................  April.............  October.
Wisconsin.......................  April 15..........  October 15.
Wyoming.........................  April.............  October.
American Samoa..................  January...........  December.
Guam............................  January...........  December.
Virgin Islands..................  January...........  December.
------------------------------------------------------------------------

Additional discussion on the procedures for siting ozone stations may be 
found in reference 4.
    2.6 Nitrogen Dioxide (NO<INF>2</INF>) Design Criteria for SLAMS. The 
typical spatial scales of representativeness associated with nitrogen 
dioxide monitoring based on monitoring objectives are middle, 
neighborhood, and urban. Since nitrogen dioxide is primarily formed in 
the atmosphere from the oxidation of NO, large volumes of air and mixing 
times usually reduce the importance of monitoring on small scale spatial 
variability especially for long averaging times. However, there may be 
some situations where NO<INF>2</INF> measurements would be made on the 
middle scale for both long- and short-term averages.
    Middle Scale--Measurements on this scale would cover dimensions from 
about 100 meters to 0.5 kilometer. These measurements would characterize 
the public exposure to NO<INF>2</INF> in populated areas. Also monitors 
that are located closer to roadways than the minimum distances specified 
in table 3 of appendix E of this part, would be represented by 
measurements on this scale.
    Neighborhood and Urban Scales--The same considerations as discussed 
in section 2.5 for O<INF>3</INF> would also apply to NO<INF>2</INF>.
    After the spatial scale is selected based on the monitoring 
objectives, then the siting procedures as found in reference 4 should be 
used to evaluate the adequacy of each existing NO<INF>2</INF> station 
and must be used to relocate an existing station or to locate any new 
NO<INF>2</INF> SLAMS stations. The siting procedures begin with 
collecting the background material. This background information may 
include the characteristics of the area and its sources under study, 
climatological data to determine where concentration maxima are most 
likely to be found, and any existing monitoring data for NO<INF>2</INF>.
    For neighborhood or urban scales, the emphasis in site selection 
will be in finding those areas where long-term averages are expected to 
be the highest. Nevertheless, it should be expected that the maximum 
NO<INF>2</INF> concentrations will occur in approximately the same 
locations as the maximum total oxides of nitrogen concentrations. The 
best course would be to locate the station somewhat further downwind 
beyond the expected point of maximum total oxides of nitrogen to allow 
more time for the formation of NO<INF>2</INF>. The dilution of the 
emissions further downwind from the source should be considered along 
with the need for reaction time for NO<INF>2</INF> formation in locating 
stations to measure peak concentration. If dispersion is favorable, 
maximum concentrations may occur closer to the emission sources than the 
locations predicted from oxidation of NO to NO<INF>2</INF> alone. This 
will occur downwind of sources based on winter wind direction or in 
areas where there are high ozone concentrations and high density 
NO<INF>2</INF> emissions such as on the fringe of the central business 
district or further downwind. The distance and direction downwind would 
be based on ozone season wind patterns.

[[Page 252]]

    Once the major emissions areas and wind patterns are known, areas of 
potential maximum NO<INF>2</INF> levels can be determined. Nitrogen 
dioxide concentrations are likely to decline rather rapidly outside the 
urban area. Therefore, the best location for measuring NO<INF>2</INF> 
concentrations will be in neighborhoods near the edge of the city.
    2.7 Lead (Pb) Design Criteria for SLAMS. Presently, less than 1 
percent of the Nation's Pb air pollution emissions originate from on-
road mobile source exhaust. The majority of Pb emissions come from point 
sources, such as metals processing facilities, waste disposal and 
recycling, and fuel combustion (reference 19 of this appendix). The 
SLAMS networks are used to assess the air quality impacts of Pb point 
sources, and to determine the broad population exposure from any Pb 
source. The most important spatial scales to effectively characterize 
the emissions from point sources are the micro, middle, and neighborhood 
scales. For purposes of establishing monitoring stations to represent 
large homogeneous areas other than the above scales of 
representativeness, urban or regional scale stations may also be needed.
    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. Data collected at microscale stations 
provide information for evaluating and developing ``hot-spot'' control 
measures.
    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 7 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.
    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. Stations 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.
    Urban Scale--Such stations would be used to present ambient Pb 
concentrations over an entire metropolitan area with dimensions in the 4 
to 50 kilometer range. An urban scale station would be useful for 
assessing trends in citywide air quality and the effectiveness of larger 
scale air pollution control strategies.
    Regional Scale--Measurements from these stations would characterize 
air quality levels over areas having dimensions of 50 to hundreds of 
kilometers. This large scale of representativeness, rarely used in Pb 
monitoring, would be most applicable to sparsely populated areas and 
could provide information on background air quality and inter-regional 
pollutant transport.
    Monitoring for ambient Pb levels is required for all major urbanized 
areas where Pb levels have been shown or are expected to be of concern 
due to the proximity of Pb point source emissions. Sources emitting five 
tons per year or more of actual point and fugitive Pb emissions would 
generally be candidates for lead ambient air monitoring. Modeling may be 
needed to determine if a source has the potential to exceed the 
quarterly lead National Ambient Air Quality Standards (NAAQS). The total 
number and type of stations for SLAMS are not prescribed but must be 
determined on a case-by-case basis. As a minimum, there must be two 
stations in any area where Pb concentrations currently exceed or have 
exceeded the Pb NAAQS during any one quarter of the most recent eight 
quarters. Where the Pb air quality violations are widespread or the 
emissions density, topography, or population locations are complex and 
varied, there may be a need to establish more than two Pb ambient air 
monitoring stations. The EPA Regional Administrator may specify more 
than two monitoring stations if it is found that two stations are 
insufficient to adequately determine if the Pb standard is being 
attained and maintained. The Regional Administrator may also specify 
that stations be located in areas outside the boundaries of the 
urbanized areas.
    Concerning the previously discussed required minimum of two 
stations, at least one of the stations must be a category (a) type 
station and the second may be either category (a) or (b) depending upon 
the extent of the point source's impact and the existence of residential 
neighborhoods surrounding the source. When the source is located in an 
area that is subject to NAMS requirements as in Section 3 of this 
Appendix, it is preferred that the NAMS site be used to describe the 
population's exposure and the second SLAMS site be used as a category 
(a) site.

[[Page 253]]

Both of these categories of stations are defined in section 3.
    To locate monitoring stations, it will be necessary to obtain 
background information such as point source emissions inventories, 
climatological summaries, and local geographical characteristics. Such 
information should be used to identify areas that are most suitable to 
the particular monitoring objective and spatial scale of 
representativeness desired. References 9 & 10 of this appendix provide 
additional guidance on locating sites to meet specific urban area 
monitoring objectives and should be used in locating new stations or 
evaluating the adequacy of existing stations.
    After locating each Pb station and, to the extent practicable, 
taking into consideration the collective impact of all Pb sources and 
surrounding physical characteristics of the siting area, a spatial scale 
of representativeness must be assigned to each station.
    2.8 Particulate Matter Design Criteria for SLAMS.
    As with other pollutants measured in the SLAMS network, the first 
step in designing the particulate matter network is to collect the 
necessary background information. Various studies in references 11, 12, 
13, 14, 15, and 16 of section 6 of this appendix have documented the 
major source categories of particulate matter and their contribution to 
ambient levels in various locations throughout the country.
    2.8.0.1 Sources of background information would be regional and 
traffic maps, and aerial photographs showing topography, settlements, 
major industries and highways. These maps and photographs would be used 
to identify areas of the type that are of concern to the particular 
monitoring objective. After potentially suitable monitoring areas for 
particulate matter have been identified on a map, modeling may be used 
to provide an estimate of particulate matter concentrations throughout 
the area of interest. After completing the first step, existing 
particulate matter stations should be evaluated to determine their 
potential as candidates for SLAMS designation. Stations meeting one or 
more of the six basic monitoring objectives described in section 1 of 
this appendix must be classified into one of the five scales of 
representativeness (micro, middle, neighborhood, urban and regional) if 
the stations are to become SLAMS. In siting and classifying particulate 
matter stations, the procedures in references 17 and 18 of section 6 of 
this appendix should be used.
    2.8.0.2 The most important spatial scales to effectively 
characterize the emissions of particulate matter from both mobile and 
stationary sources are the middle scales for PM<INF>10</INF> and 
neighborhood scales for both PM<INF>10</INF> and PM<INF>2.5</INF>. For 
purposes of establishing monitoring stations to represent large 
homogenous areas other than the above scales of representativeness and 
to characterize regional transport, urban or regional scale stations 
would also be needed. Most PM<INF>2.5</INF> monitoring in urban areas 
should be representative of a neighborhood scale.
    2.8.0.3 Microscale--This scale would typify areas such as downtown 
street canyons and traffic corridors where the general public would be 
exposed to maximum concentrations from mobile sources. In some 
circumstances, the microscale is appropriate for particulate stations; 
core SLAMS on the microscale should, however, be limited to urban sites 
that are representative of long-term human exposure and of many such 
microenvironments in the area. In general, microscale particulate matter 
sites should be located near inhabited buildings or locations where the 
general public can be expected to be exposed to the concentration 
measured. Emissions from stationary sources such as primary and 
secondary smelters, power plants, and other large industrial processes 
may, under certain plume 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. Data collected at microscale 
stations provide information for evaluating and developing hot spot 
control measures. Unless these sites are indicative of population-
oriented monitoring, they may be more appropriately classified as SPMs.
    2.8.0.4 Middle Scale--Much of the measurement of short-term public 
exposure to coarse fraction particles (PM<INF>10</INF>) is on this scale 
and on the neighborhood scale; for fine particulate, much of the 
measurement is on the neighborhood scale. People moving through downtown 
areas, or living near major roadways, encounter particles that would be 
adequately characterized by measurements of this spatial scale. Thus, 
measurements of this type would be appropriate for the evaluation of 
possible short-term exposure public health effects of particulate matter 
pollution. In many situations, monitoring sites that are representative 
of micro-scale or middle-scale impacts are not unique and are 
representative of many similar situations. This can occur along traffic 
corridors or other locations in a residential district. In this case, 
one location is representative of a neighborhood of small scale sites 
and is appropriate for evaluation of long-term or chronic effects. This 
scale also includes the characteristic concentrations for other areas 
with dimensions of a few hundred meters such as the parking lot and 
feeder streets associated with shopping centers, stadia, and office 
buildings. In the case of PM<INF>10</INF>, unpaved or seldom swept 
parking lots associated with these sources could be an important source 
in addition to the vehicular emissions themselves.

[[Page 254]]

    2.8.0.5 Neighborhood Scale--Measurements in this category would 
represent conditions throughout some reasonably homogeneous urban 
subregion with dimensions of a few kilometers and of generally more 
regular shape than the middle scale. Homogeneity refers to the 
particulate matter concentrations, as well as the land use and land 
surface characteristics. Much of the PM<INF>2.5</INF> exposures are 
expected to be associated with this scale of measurement. In some cases, 
a location carefully chosen to provide neighborhood scale data would 
represent not only the immediate neighborhood but also neighborhoods of 
the same type in other parts of the city. Stations of this kind provide 
good information about trends and compliance with standards because they 
often represent conditions in areas where people commonly live and work 
for periods comparable to those specified in the NAAQS. In general, most 
PM<INF>2.5</INF> monitoring in urban areas should have this scale. A 
PM<INF>2.5</INF> monitoring location is assumed to be representative of 
a neighborhood scale unless the monitor is adjacent to a recognized 
PM<INF>2.5</INF> emissions source or is otherwise demonstrated to be 
representative of a smaller spatial scale by an intensive monitoring 
study. This category also may include industrial and commercial 
neighborhoods especially in districts of diverse land use where 
residences are interspersed.
    2.8.0.6 Neighborhood scale data could provide valuable information 
for developing, testing, and revising models that describe the larger-
scale concentration patterns, especially those models relying on 
spatially smoothed emission fields for inputs. The neighborhood scale 
measurements could also be used for neighborhood comparisons within or 
between cities. This is the most likely scale of measurements to meet 
the needs of planners.
    2.8.0.7 Urban Scale--This class of measurement would be made to 
characterize the particulate matter concentration over an entire 
metropolitan or rural area ranging in size from 4 to 50 km. Such 
measurements would be useful for assessing trends in area-wide air 
quality, and hence, the effectiveness of large scale air pollution 
control strategies. Core PM<INF>2.5</INF> SLAMS may have this scale.
    2.8.0.8 Regional Scale--These measurements would characterize 
conditions over areas with dimensions of as much as hundreds of 
kilometers. As noted earlier, using representative conditions for an 
area implies some degree of homogeneity in that area. For this reason, 
regional scale measurements would be most applicable to sparsely 
populated areas with reasonably uniform ground cover. Data 
characteristics of this scale would provide information about larger 
scale processes of particulate matter emissions, losses and transport. 
Especially in the case of PM<INF>2.5</INF>, transport contributes to 
particulate concentrations and may affect multiple urban and State 
entities with large populations such as in the Eastern United States. 
Development of effective pollution control strategies requires an 
understanding at regional geographical scales of the emission sources 
and atmospheric processes that are responsible for elevated 
PM<INF>2.5</INF> levels and may also be associated with elevated ozone 
and regional haze.
    2.8.1 Specific Design Criteria for PM<INF>2.5</INF>.
    2.8.1.1 Monitoring Planning Areas.
    Monitoring planning areas (MPAs) shall be used to conform to the 
community-oriented monitoring approach used for the PM<INF>2.5</INF> 
NAAQS given in part 50 of this chapter. MPAs are required to correspond 
to all metropolitan statistical areas (MSAs) with population greater 
than 200,000, and all other areas determined to be in violation of the 
PM<INF>2.5</INF> NAAQS.<SUP>1</SUP> MPAs for other designated parts of 
the State are optional. All MPAs shall be defined on the basis of 
existing, delineated mapping data such as State boundaries, county 
boundaries, zip codes, census blocks, or census block groups.
---------------------------------------------------------------------------

    \1\The boundaries of MPAs do not have to necessarily correspond to 
those of MSAs and existing intra or interstate air pollution planning 
districts may be utilized.
---------------------------------------------------------------------------

    2.8.1.2 PM<INF>2.5</INF> Monitoring Sites within the State's PM 
Monitoring Network Description.
    2.8.1.2.1 The minimum required number, type of monitoring sites, and 
sampling requirements for PM<INF>2.5</INF> are based on monitoring 
planning areas described in the PM monitoring network description and 
proposed by the State in accordance with Sec. 58.20.
    2.8.1.2.2 Comparisons to the PM<INF>2.5</INF> NAAQS may be based on 
data from SPMs in addition to SLAMS (including NAMS, core SLAMS and 
collocated PM<INF>2.5</INF> sites at PAMS), that meet the requirements 
of Sec. 58.13 and Appendices A, C and E of this part, that are included 
in the PM monitoring network description. For comparison to the annual 
NAAQS, the monitors should be neighborhood scale community-oriented 
locations. Special purpose monitors that meet part 58 requirements will 
be exempt from NAAQS comparisons with the PM<INF>2.5</INF> NAAQS for the 
first 2 calendar years of their operation to encourage PM<INF>2.5</INF> 
monitoring initially. After this time, however, any SPM that records a 
violation of the PM<INF>2.5</INF> NAAQS must be seriously considered as 
a potential SLAMS site during the annual SLAMS network review in 
accordance with Sec. 58.25. If such SPMs are not established as a 
SLAMS, the agency must document in its annual report the technical basis 
for excluding it as a SLAMS.
    2.8.1.2.3 The health-effects data base that served as the basis for 
selecting the new PM<INF>2.5</INF> standards relied on a spatial average 
approach that reflects average community-oriented area-wide PM exposure 
levels.

[[Page 255]]

Under this approach, the most effective way to reduce total population 
risk is by lowering the annual distributions of ambient 24-hour 
PM<INF>2.5</INF> concentrations, as opposed to controlling peak 24-hour 
concentrations on individual days. The annual standard selected by EPA 
will generally be the controlling standard for lowering both short- and 
long-term PM<INF>2.5</INF> concentrations on an area-wide basis and will 
achieve this result. In order to be consistent with this rationale, 
therefore, PM<INF>2.5</INF> data collected from SLAMS and special 
purpose monitors that are representative, not of area-wide but rather, 
of relatively unique population-oriented microscale, or localized hot 
spot, or unique population-oriented middle-scale impact sites are only 
eligible for comparison only to the 24-hour PM<INF>2.5</INF> NAAQS. 
However, in instances where certain population-oriented micro- or 
middle-scale PM<INF>2.5</INF> monitoring sites are determined by the EPA 
Regional Administrator to collectively identify a larger region of 
localized high ambient PM<INF>2.5</INF> concentrations, data from these 
population-oriented sites would be eligible for comparison to the annual 
NAAQS.
    2.8.1.2.4 Within each MPA, the responsible air pollution control 
agency shall install core SLAMS, other required SLAMS and as many 
PM<INF>2.5</INF> stations judged necessary to satisfy the SLAMS 
requirements and monitoring objectives of this appendix.
    2.8.1.3 Core Monitoring Stations for PM<INF>2.5</INF>.
    Core monitoring stations or sites are a subset of the SLAMS network 
for PM<INF>2.5</INF> that are sited to represent community-wide air 
quality. These core sites include sites to be collocated at PAMS.
    2.8.1.3.1 Within each monitoring planning area, the responsible air 
pollution control agency shall install the following core 
PM<INF>2.5</INF> SLAMS:
    (a) At least two core PM<INF>2.5</INF> SLAMS per MSA with population 
greater than 500,000 sampling everyday, unless exempted by the Regional 
Administrator, including at least one station in a population-oriented 
area of expected maximum concentration and at least one station in an 
area of poor air quality and at least one additional core monitor 
collocated at a PAMS site in each PAMS area<SUP>2</SUP>.
---------------------------------------------------------------------------

    \2\The core monitor to be collocated at a PAMS site shall not be 
considered a part of the PAMS as described in section 4 of this 
appendix, but shall instead be considered to be a component of the 
particular MPA PM<INF>2.5</INF> network.
---------------------------------------------------------------------------

    (b) At least one core PM<INF>2.5</INF> SLAMS per MSA with population 
greater than 200,000 and less than or equal to 500,000 sampling every 
third day.
    (c) Additional core PM<INF>2.5</INF> SLAMS per MSA with population 
greater than 1 million, sampling every third day, as specified in the 
following table:

   Table 1--Required Number of Core SLAMS According to MSA Population
------------------------------------------------------------------------
                                      Minimum Required No. of Core Sites
           MSA Population                            \1\
------------------------------------------------------------------------
<ls-thn-eq>1 M                       3
------------------------------------------------------------------------
<ls-thn-eq>2 M                       4
------------------------------------------------------------------------
<ls-thn-eq>4 M                       6
------------------------------------------------------------------------
<ls-thn-eq>6 M                       8
------------------------------------------------------------------------
<ls-thn-eq>8 M                       10
------------------------------------------------------------------------
\1\Core SLAMS at PAMS are in addition to these numbers.

    2.8.1.3.2 The site situated in the area of expected maximum 
concentration is analogous to NAMS ``category a.'' \3\ This will 
henceforth be termed a category a core SLAMS site. The site located in 
the area of poor air quality with high population density or 
representative of maximum population impact is analogous to NAMS, 
``category b.'' This second site will be called a category b core SLAMS 
site.
---------------------------------------------------------------------------

    \3\The measured maximum concentrations at core population-oriented 
sites should be consistent with the averaging time of the NAAQS. 
Therefore, sites only with high concentrations for shorter averaging 
times (say 1-hour) should not be category ``a'' core SLAMS monitors.
---------------------------------------------------------------------------

    2.8.1.3.3 Those MPAs that are substantially impacted by several 
different and geographically disjoint local sources of fine particulate 
should have separate core sites to monitor each influencing source 
region.
    2.8.1.3.4 Within each monitoring planning area, one or more required 
core SLAMS may be exempted by the Regional Administrator. This may be 
appropriate in areas where the highest concentration is expected to 
occur at the same location as the area of maximum or sensitive 
population impact, or areas with low concentrations (e.g., highest 
concentrations are less than 80 percent of the NAAQS). When only one 
core monitor for PM<INF>2.5</INF> is included in a MPA or optional CMZ, 
however, a ``category a'' core site is strongly preferred to determine 
community-oriented PM<INF>2.5</INF> concentrations in areas of high 
average PM<INF>2.5</INF> concentration.
    2.8.1.3.5 More than the minimum number of core SLAMS should be 
deployed as necessary in all MPAs. Except for the core SLAMS described 
in section 2.8.1.3.1 of this appendix, the additional core SLAMS must 
only comply with the minimum sampling frequency for SLAMS specified in 
Sec. 58.13(e).
    2.8.1.3.6 A subset of the core PM<INF>2.5</INF> SLAMS shall be 
designated NAMS as discussed in section 3.7 of this appendix. The 
selection of

[[Page 256]]

core monitoring sites in relation to MPAs and CMZs is discussed further 
in section 2.8.3 of this appendix.
    2.8.1.3.7 Core monitoring sites shall represent neighborhood or 
larger spatial scales. A monitor that is established in the ambient air 
that is in or near a populated area, and meets appropriate 40 CFR part 
58 criteria (i.e., meets the requirements of Sec. 58.13 and Sec. 
58.14, Appendices A, C, and E of this part) can be presumed to be 
representative of at least a neighborhood scale, is eligible to be 
called a core site and shall produce data that are eligible for 
comparison to both the 24-hour and annual PM<INF>2.5</INF> NAAQS. If the 
site is adjacent to a dominating local source or can be shown to have 
average 24-hour concentrations representative of a smaller spatial 
scale, then the site would only be compared to the 24-hour 
PM<INF>2.5</INF> NAAQS.
    2.8.1.3.8 Continuous fine particulate monitoring at core SLAMS. At 
least one continuous fine particulate analyzer (e.g., beta attenuation 
analyzer; tapered-element, oscillating microbalance (TEOM); 
transmissometer; nephelometer; or other acceptable continuous fine 
particulate monitor) shall be located at a core monitoring 
PM<INF>2.5</INF> site in each metropolitan area with a population 
greater than 1 million. These analyzers shall be used to provide 
improved temporal resolution to better understand the processes and 
causes of elevated PM<INF>2.5</INF> concentrations and to facilitate 
public reporting of PM<INF>2.5</INF> air quality and will be in 
accordance with appropriate methodologies and QA/QC procedures approved 
by the Regional Administrator.
    2.8.1.4 Other PM<INF>2.5</INF> SLAMS Locations.
    In addition to the required core sites described in section 2.8.1.3 
of this appendix, the State shall also install and operate on an every 
third day sampling schedule at least one SLAMS to monitor for regional 
background and at least one SLAMS to monitor regional transport. These 
monitoring stations may be at a community-oriented site and their 
requirement may be satisfied by a corresponding SLAMS monitor in an area 
having similar air quality in another State. The State shall also be 
required to establish additional SLAMS sites based on the total 
population outside the MSA(s) associated with monitoring planning areas 
that contain required core SLAMS. There shall be one such additional 
SLAMS for each 200,000 people. The minimum number of SLAMS may be 
deployed anywhere in the State to satisfy the SLAMS monitoring 
objectives including monitoring of small scale impacts which may not be 
community-oriented or for regional transport as described in section 1 
of this appendix. Other SLAMS may also be established and are encouraged 
in a State PM<INF>2.5</INF> network.
    2.8.1.5 Additional PM<INF>2.5</INF> Analysis Requirements.
    (a) Within 1 year after September 16, 1997, chemical speciation will 
be required at approximately 25 PM<INF>2.5</INF> core sites collocated 
at PAMS sites (1 type 2 site per PAMS area) and at approximately 25 
other core sites for a total of approximately 50 sites. The selection of 
these sites will be performed by the Administrator in consultation with 
the Regional Administrator and the States. Chemical speciation is 
encouraged at additional sites. At a minimum, chemical speciation to be 
conducted will include analysis for elements, selected anions and 
cations, and carbon. Samples for required speciation will be collected 
using appropriate monitoring methods and sampling schedule in accordance 
with procedures approved by the Administrator.
    (b) Air pollution control agencies shall archive PM<INF>2.5</INF> 
filters from all other SLAMS sites for a minimum of one year after 
collection. These filters shall be made available for supplemental 
analyses at the request of EPA or to provide information to State and 
local agencies on the composition for PM<INF>2.5</INF>. The filters 
shall be archived in accordance with procedures approved by the 
Administrator.
    2.8.1.6 Community Monitoring Zones.
    2.8.1.6.1 The CMZs describe areas within which two or more core 
monitors may be averaged for comparison with the annual PM<INF>2.5</INF> 
NAAQS. This averaging approach as specified in 40 CFR part 50, appendix 
N, is directly related to epidemiological studies used as the basis for 
the PM<INF>2.5</INF> NAAQS. A CMZ should characterize an area of 
relatively similar annual average air quality (i.e., the average 
concentrations at individual sites shall not exceed the spatial average 
by more than 20 percent) and exhibit similar day to day variability 
(e.g., the monitoring sites should not have low correlations, say less 
than 0.6). Moreover, the entire CMZ should principally be affected by 
the same major emission sources of PM<INF>2.5</INF> .
    2.8.1.6.2 Each monitoring planning area may have at least one CMZ, 
that may or may not cover the entire MPA. In metropolitan statistical 
areas (MSAs) for which MPAs are required, the CMZs may completely cover 
the entire MSA. When more than one CMZ is described within an MPA, CMZs 
shall not overlap in their geographical coverage. All areas in the 
ambient air may become a CMZ.
    2.8.1.6.3. As PM<INF>2.5</INF> networks are first established, core 
sites would be used individually for making comparisons to the annual 
PM<INF>2.5</INF> NAAQS. As these networks evolve, individual monitors 
may not be adequate by themselves to characterize the annual average 
community wide air quality. This is especially true for areas with sharp 
gradients in annual average air quality. Therefore, CMZs with multiple 
core SLAMS or other eligible sites as described in accordance with

[[Page 257]]

section 2.8.1.2 to this appendix, may be established for the purposes of 
providing improved estimates of community wide air quality and for 
making comparisons to the annual NAAQS. This CMZ approach is subject to 
the constraints of section 2.8.1.6.1 to this appendix.
    2.8.1.6.4 The spatial representativeness of individual monitoring 
sites should be considered in the design of the network and in 
establishing the boundaries of CMZs. Communities within the MPA with the 
highest PM<INF>2.5</INF> concentrations must have a high priority for 
PM<INF>2.5</INF> monitoring. Until a sufficient number of monitoring 
stations or CMZs are established, however, the monitored air quality in 
all parts of the MPA may not be precisely known. It would be desirable, 
however, to design the placement of monitors so that those portions of 
the MPAs without monitors could be characterized as having average 
concentrations less than the monitored portions of the network.
    2.8.1.7 Selection of Monitoring Locations Within MPAs or CMZs.
    2.8.1.7.1 Figure 1 of this appendix illustrates a hypothetical 
monitoring planning area and shows the location of monitors in relation 
to population and areas of poor air quality. Figure 2 of this appendix 
shows the same hypothetical MPA as Figure 1 of this appendix and 
illustrates potential community monitoring zones and the location of 
core monitoring sites within them.
    2.8.1.7.2 In Figure 1 of this appendix, a hypothetical monitoring 
planning area is shown representing a typical Eastern US urban areas. 
The ellipses represent zones with relatively high population and poor 
air quality, respectively. Concentration isopleths are also depicted. 
The highest population density is indicated by the urban icons, while 
the area of worst air quality is presumed to be near the industrial 
symbols. The monitoring area should have at least one core monitor to 
represent community wide air quality in each sub-area affected by 
different emission sources. Each monitoring planning area with 
population greater than 500,000 is required to have at least two core 
population-oriented monitors that will sample everyday (with PAMS areas 
requiring three) and may have as many other core SLAMS, other SLAMS, and 
SPMs as necessary. All SLAMS should generally be population-oriented, 
while the SPMs can focus more on other monitoring objectives, e.g., 
identifying source impacts and the area boundaries with maximum 
concentration. C<INF>a</INF> denotes ``category a'' core SLAMS site 
(community-oriented site in area of expected maximum concentration); it 
is shown within the populated area and closest to the area with highest 
concentration. C<INF>b</INF> denotes a ``category b'' core SLAMS site 
(area of poor air quality with high population density or representative 
of maximum population impact); it is shown in the area of poor air 
quality, closest to highest population density. All other core SLAMS in 
this MPA are denoted by ``C.'' S denotes other SLAMS sites (monitoring 
for any objective: Max concentration, population exposure, source-
oriented, background, or regional transport or in support of secondary 
NAAQS). P denotes a Special Purpose Monitor (a specialized monitor that, 
for example, may use a non-reference sampler). Finally, note that all 
SPMs would be subject to the 2-year moratorium against data comparison 
to the NAAQS for the first 2 complete calendar years of its operation.
    2.8.1.7.3 A Monitoring Planning Area may have one or more community 
monitoring zones (CMZ) for aggregation of data from eligible SLAMS and 
SPM sites for comparison to the annual NAAQS. The planning area has 
large gradients of average air quality and, as shown in Figure 2 may be 
assigned three CMZs: An industrial zone, a downtown central business 
district (CBD), and a residential area. (If there is not a large 
difference between downtown concentrations and other residential areas, 
a separate CBD zone would not be appropriate).

[[Page 258]]

[GRAPHIC] [TIFF OMITTED] TR17FE98.008

[[Page 259]]

[GRAPHIC] [TIFF OMITTED] TR17FE98.009

    2.8.1.7.4 Figure 3 of this appendix illustrates how CMZs and 
PM<INF>2.5</INF> monitors might be located in a hypothetical MPA typical 
of a Western State. Western States with more localized sources of PM and 
larger geographic area could require a different mix of SLAMS and SPM 
monitors and may need

[[Page 260]]

more total monitors. As the networks are deployed, the available 
monitors may not be sufficient to completely represent all geographic 
portions of the Monitoring Planning Area. Due to the distribution of 
pollution and population and because of the number and spatial 
representativeness of monitors, the MPAs and CMZs may not cover the 
entire State.
[GRAPHIC] [TIFF OMITTED] TR18JY97.176

    2.8.1.7.5 Figure 4 of this appendix shows how the MPAs, CMZs, and 
PM<INF>2.5</INF> monitors might be distributed within a hypothetical 
State. Areas of the State included within MPAs are shown within heavy 
solid lines. Two MPAs are illustrated. Areas in the State outside the 
MPAs will also include monitors, but this monitoring coverage may be 
limited. This portion of the State may also be represented by CMZs 
(shown by areas enclosed within dotted lines). The monitors that are 
intended for comparison to the NAAQS are indicated by X. Furthermore, 
eligible monitors within a CMZ could be averaged for comparison to the 
annual NAAQS or examined individually for comparison to both NAAQS. Both 
within the MPAs and in the remainder of the State, some special study 
monitors might not satisfy applicable 40 CFR part 58 requirements and 
will not be eligible for comparison to the NAAQS.

[[Page 261]]

[GRAPHIC] [TIFF OMITTED] TR18JY97.177

    2.8.2 Substitute PM Monitoring Sites.
    2.8.2.1 Section 2.2 of appendix C of this part describes conditions 
under which TSP samplers can be used as substitutes for PM<INF>10</INF>. 
This provision is intended to be used when PM<INF>10</INF> 
concentrations are expected to be very low and substitute TSP samplers 
can be used to satisfy the minimum number of PM<INF>10</INF> samplers 
needed for an adequate PM<INF>10</INF> network.
    2.8.2.2 If data produced by substitute PM samplers exceed the 
concentration levels described in appendix C of this part, then the need 
for this sampler to be converted to a PM<INF>10</INF> or 
PM<INF>2.5</INF> sampler, shall be considered in the PM monitoring 
network review. If the State does not believe that a PM<INF>10</INF> or 
PM<INF>2.5</INF> sampler should be sited, the State shall submit 
documentation to EPA as part of its annual PM report to justify this 
decision. If a PM site is not designated as a substitute site in the PM 
monitoring network description, then high concentrations at this site 
would not necessarily cause this site to become a PM<INF>2.5</INF> or 
PM<INF>10</INF> site, whichever is indicated.
    2.8.2.3 Consistent with Sec. 58.1, combinations of SLAMS 
PM<INF>10</INF> or PM<INF>2.5</INF> monitors and other monitors may 
occupy the same structure without any mutual effect on the regulatory 
definition of the monitors.

3. Network Design for National Air Monitoring Stations (NAMS)

    The NAMS must be stations selected from the SLAMS network with 
emphasis given to urban and multisource areas. Areas to be monitored 
must be selected based on urbanized population and pollutant 
concentration levels. Generally, a larger number of NAMS are needed in 
more polluted urban and multisource areas. The network design criteria 
discussed below reflect these concepts. However, it should be emphasized 
that deviations from the NAMS network design criteria may be necessary 
in a few cases. Thus, these design criteria are not a set of rigid rules 
but rather a guide for achieving a proper distribution of monitoring 
sites on a national scale.
    The primary objective for NAMS is to monitor in the areas where the 
pollutant concentration and the population exposure are expected to be 
the highest consistent with the averaging time of the NAAQS. 
Accordingly, the NAMS fall into two categories:
    Category (a): Stations located in area(s) of expected maximum 
concentrations, generally microscale for CO, microscale or middle scale 
for Pb, middle scale or neighborhood scale for population-oriented 
particulate matter, urban or regional scale for Regional transport 
PM<INF>2.5</INF>, neighborhood scale for SO2, and NO2, and urban scale 
for O<INF>3</INF>.

[[Page 262]]

    Category (b): Stations which combine poor air quality with a high 
population density but not necessarily located in an area of expected 
maximum concentrations (neighborhood scale, except urban scale for 
NO<INF>2</INF>). Category (b) monitors would generally be representative 
of larger spatial scales than category (a) monitors.
    For each urban area where NAMS are required, both categories of 
monitoring stations must be established. In the case of Pb and 
SO<INF>2</INF> if only one NAMS is needed, then category (a) must be 
used. The analysis and interpretation of data from NAMS should consider 
the distinction between these types of stations as appropriate.
    For each MSA where NAMS are required, both categories of monitoring 
stations must be established. In the case of SO<INF>2</INF> if only one 
NAMS is needed, then category (a) must be used. The analysis and 
interpretation of data from NAMS should consider the distinction between 
these types of stations as appropriate.
    The concept of NAMS is designed to provide data for national policy 
analyses/trends and for reporting to the public on major metropolitan 
areas. It is not the intent to monitor in every area where the NAAQS are 
violated. On the other hand, the data from SLAMS should be used 
primarily for nonattainment decisions/ analyses in specific geographical 
areas. Since the NAMS are stations from the SLAMS network, station 
locating procedures for NAMS are part of the SLAMS network design 
process.
    3.1 [Reserved]
    3.2 Sulfur Dioxide (SO<INF>2</INF>) Design Criteria for NAMS. It is 
desirable to have a greater number of NAMS in the more polluted and 
densely populated urban and multisource areas. The data in table 3 show 
the approximate number of permanent stations needed in urban areas to 
characterize the national and regional SO<INF>2</INF> air quality trends 
and geographical patterns. These criteria require that the number of 
NAMS in areas where urban populations exceed 1,000,000 and 
concentrations also exceed the primary NAAQS may range from 6 to 10 and 
that in areas where the SO<INF>2</INF> problem is minor, only one or two 
(or no) monitors are required. For those cases where more than one 
station is required for an urban area, there should be at least one 
station for category (a) and category (b) objectives as discussed in 
section 3. Where three or more stations are required, the mix of 
category (a) and (b) stations is determined on a case-by-case basis. The 
actual number and location of the NAMS must be determined by EPA 
Regional Offices and the State Agency, subject to the approval of EPA 
Headquarters, Office of Air Quality Planning and Standards (OAQPS).

          Table 3--SO2 National Air Monitoring Station Criteria
               [Approximate number of stations per area] a
------------------------------------------------------------------------
                                  High          Medium          Low
    Population category      concentration  concentration  concentration
                                   b              c              d
------------------------------------------------------------------------
<ls-thn-eq>1,000,000             6-10               4-8          2-4
500,000 to 1,000,000              4-8               2-4          1-2
250,000 to 500,000                3-4               1-2          0-1
100,000 to 250,000                1-2               0-1            0
------------------------------------------------------------------------
a Selection of urban areas and actual number of stations per area will
  be jointly determined by EPA and the State agency.
b High concentration--exceeding level of the primary NAAQS.
c Medium concentration--exceeding 60 percent of the level of the primary
  or 100% of the secondary NAAQS.
d Low concentration--less than 60 percent of the level of the primary or
  100% of the secondary NAAQS.

    The estimated number of SO<INF>2</INF> NAMS which would be required 
nationwide ranges from approximately 200 to 300. This number of NAMS 
SO<INF>2</INF> monitors is sufficient for national trend purposes due to 
the low background SO<INF>2</INF> levels, and the fact that air quality 
is very sensitive to SO<INF>2</INF> emission changes. The actual number 
of stations in any specific area depends on local factors such as 
meteorology, topography, urban and regional air quality gradients, and 
the potential for significant air quality improvements or degradation. 
The greatest density of stations should be where urban populations are 
large and where pollution levels are high. Fewer NAMS are necessary in 
the western States since concentrations are seldom above the NAAQS in 
their urban areas. Exceptions to this are in the areas where an expected 
shortage of clean fuels indicates that ambient air quality may be 
degraded by increased SO<INF>2</INF> emissions. In such cases, a minimum 
number of NAMS is required to provide EPA with a proper national 
perspective on significant changes in air quality.
    Like TSP, the worst air quality in an urban area is to be used as 
the basis for determining the required number of SO<INF>2</INF> NAMS 
(see table 3). This includes SO<INF>2</INF> air quality levels within 
populated parts of urbanized areas, that are affected by one or two 
point sources of SO<INF>2</INF> if the impact of the source(s) extends 
over a reasonably broad geographic scale (neighborhood or larger). 
Maximum SO<INF>2</INF> air quality levels in remote unpopulated areas 
should be excluded as a basis for selecting NAMS regardless of the 
sources affecting the concentration levels. Such remote areas are more 
appropriately monitored by SLAMS or SPM networks and/or characterized by 
diffusion model calculations as necessary.
    3.3 Carbon Monoxide (CO) Design Criteria for NAMS. Information is 
needed on ambient CO levels in major urbanized areas where CO levels 
have been shown or inferred to be a

[[Page 263]]

significant concern. At the national level, EPA will not routinely 
require data from as many stations as are required for PM-10, and 
perhaps SO<INF>2</INF>, since CO trend stations are principally needed 
to assess the overall air quality progress resulting from the emission 
controls required by the Federal motor vehicle control program (FMVCP) 
and other local controls.
    Although State and local air programs may require extensive 
monitoring to document and measure the local impacts of CO emissions and 
emission controls, an adequate national perspective is possible with as 
few as two stations per major urban area. The two categories for which 
CO NAMS would be required are: (a) Peak concentration areas such as are 
found around major traffic arteries and near heavily traveled streets in 
downtown areas (micro scale); and (b) neighborhoods where concentration 
exposures are significant (middle scale, neighborhood scale).
    The peak concentration station (micro scale) is usually found near 
heavily traveled downtown streets (street canyons), but could be found 
along major arterials (corridors), either near intersections or at low 
elevations which are influenced by downslope drainage patterns under low 
inversion conditions. The peak concentration station should be located 
so that it is representative of several similar source configurations in 
the urban area, where the general population has access. Thus, it should 
reflect one of many potential peak situations which occur throughout the 
urban area. It is recognized that this does not measure air quality 
which represents large geographical areas. Thus, a second type of 
station on the neighborhood scale is necessary to provide data 
representative of the high concentration levels which exist over large 
geographical areas.
    The category (b) (middle scale or neighborhood scale) should be 
located in areas with a stable, high population density, projected 
continuity of neighborhood character, and high traffic density. The 
stations should be located where no major zoning changes, new highways, 
or new shopping centers are being considered. The station should be 
where a significant CO pollution problem exists, but not be unduly 
influenced by any one line source. Rather, it should be more 
representative of the overall effect of the sources in a significant 
portion of the urban area.
    Because CO is generally associated with heavy traffic and population 
clusters, an urbanized area with a population greater than 500,000 is 
the principal critertion for identifying the urban areas for which pairs 
of NAMS for this pollutant will be required. The criterion is based on 
judgment that stations in urban areas with greater than 500,000 
population would provide sufficient data for national analysis and 
national reporting to Congress and the public. Also, it has generally 
been shown that major CO problems are found in areas greater than 
500,000 population.
    3.4 Ozone (O<INF>3</INF>) Design Criteria for NAMS. The criterion 
for selecting locations for ozone NAMS is any urbanized area having a 
population of more than 200,000. This population cut off is used since 
the sources of hydrocarbons are both mobile and stationary and are more 
diverse. Also, because of local and national control strategies and the 
complex chemical process of ozone formation and transport, more sampling 
stations than for CO are needed on a national scale to better understand 
the ozone problem. This selection criterion is based entirely on 
population and will include those relatively highly populated areas 
where most of the oxidant precursors originate.
    Each urban area will generally require only two ozone NAMS, One 
station would be representative of maximum ozone concentrations 
(category (a), urban scale) under the wind transport conditions as 
discussed in section 2.5. The exact location should balance local 
factors affecting transport and buildup of peak O<INF>3</INF> levels 
with the need to represent population exposure. The second station 
(category (b), neighborhood scale), should be representative of high 
density population areas on the fringes of the central business district 
along the predominant summer/fall daytime wind direction. This latter 
station should measure peak O<INF>3</INF> levels under light and 
variable or stagnant wind conditions. Two ozone NAMS stations will be 
sufficient in most urban areas since spatial gradients for ozone 
generally are not as sharp as for other criteria pollutants.
    3.5 Nitrogen Dioxide (NO<INF>2</INF>) Criteria for NAMS. Nitrogen 
dioxide NAMS will be required in those areas of the country which have a 
population greater than 1,000,000. These areas will have two 
NO<INF>2</INF> NAMS. It is felt that stations in these major 
metropolitan areas would provide sufficient data for a national analysis 
of the data, and also because NO<INF>2</INF> problems occur in areas of 
greater than 1,000,000 population.
    Within urban areas requiring NAMS, two permanent monitors are 
sufficient. The first station (category (a), middle scale or 
neighborhood scale) would be to measure the photochemical production of 
NO<INF>2</INF> and would best be located in that part of the urban area 
where the emission density of NO<INF>X</INF> is the highest. The second 
station (category (b) urban scale), would be to measure the 
NO<INF>2</INF> produced from the reaction of NO with O<INF>3</INF> and 
should be downwind of the area of peak NO<INF>X</INF> emission areas.
    3.6 Lead (Pb) Design Criteria for NAMS. In order to achieve the 
national monitoring objective, one NAMS site must be located in one of 
the two cities with the greatest population in the following ten regions 
of the

[[Page 264]]

country (the choice of which of the two metropolitan areas should have 
the lead NAMS requirement is made by the Administrator or the 
Administrator's designee using the recommendation of the Regional 
Administrators or the Regional Administrators' designee):

 Table 1--EPA Regions & Two Current Largest MSA/CMSAs (Using 1995 Census
                                  Data)
------------------------------------------------------------------------
            Region (States)                   Two Largest MSA/CMSAs
------------------------------------------------------------------------
I (Connecticut, Massachusetts, Maine,    Boston-Worcester-Lawrence CMSA,
 New Hampshire, Rhode Island, Vermont).   Hartford, CT MSA.
II (New Jersey, New York, Puerto Rico,   New York-Northern New Jersey-
 U.S. Virgin Islands).                    Long Island, CMSA, San Juan-
                                          Caguas-Arecibo, PR CMSA.
III (Delaware, Maryland, Pennsylvania,   Washington-Baltimore CMSA,
 Virginia, West Virginia, Washington,     Philadelphia-Wilmington-
 DC).                                     Atlantic City CMSA.
IV (Alabama, Florida, Georgia,           Miami-Fort Lauderdale CMSA,
 Kentucky, Mississippi, North Carolina,   Atlanta, GA MSA.
 South Carolina, Tennessee).
V (Illinois, Indiana, Michigan,          Chicago-Gary-Kenosha CMSA,
 Minnesota, Ohio, Wisconsin).             Detroit-Ann Arbor-Flint CMSA.
VI (Arkansas, Louisiana, New Mexico,     Dallas-Fort Worth CMSA, Houston-
 Oklahoma, Texas).                        Galveston-Brazoria CMSA.
VII (Iowa, Kansas, Missouri, Nebraska).  St. Louis MSA, Kansas City MSA.
VIII (Colorado, Montana, North Dakota,   Denver-Boulder-Greeley CMSA,
 South Dakota, Utah, Wyoming).            Salt Lake City-Ogden MSA.
IX (American Samoa, Arizona,             Los Angeles-Riverside-Orange
 California, Guam, Hawaii, Nevada).       County CMSA, San Francisco-
                                          Oakland-San Jose CMSA.
X (Alaska, Idaho, Oregon, Washington)..  Seattle-Tacoma-Bremerton CMSA,
                                          Portland-Salem CMSA.
------------------------------------------------------------------------

    In addition, one NAMS site must be located in each of the MSA/CMSAs 
where one or more violations of the quarterly Pb NAAQS have been 
recorded over the previous eight quarters. If a violation of the 
quarterly Pb NAAQS is measured at a monitoring site outside of a MSA/
CMSA, one NAMS site must be located within the county in a populated 
area, apart from the Pb source, to assess area wide Pb air pollution 
levels. These NAMS sites should represent the maximum Pb concentrations 
measured within the MSA/CMSA, city, or county that is not directly 
affected from a single Pb point source. Further, in order that on-road 
mobile source emissions may continue to be verified as not contributing 
to lead NAAQS violations, roadside ambient lead monitors should be 
considered as viable NAMS site candidates. A NAMS site may be a 
microscale or middle scale category (a) station, located adjacent to a 
major roadway (e.g., <ls-thn-eq>30,000 ADT), or a neighborhood scale 
category (b) station that is located in a highly populated residential 
section of the MSA/CMSA or county where the traffic density is high. 
Data from these sites will be used to assess general conditions for 
large MSA/CMSAs and other populated areas as a marker for national 
trends, and to confirm continued attainment of the Pb NAAQS. In some 
cases, the MSA/CMSA subject to the latter lead NAMS requirement due to a 
violating point source will be the same MSA/CMSA subject to the lead 
NAMS requirement based upon its population. For these situations, the 
total minimum number of required lead NAMS is one.
    3.7 Particulate Matter Design Criteria for NAMS.
    3.7.1 Table 4 indicates the approximate number of permanent stations 
required in MSAs to characterize national and regional PM<INF>10</INF> 
air quality trends and geographical patterns. The number of 
PM<INF>10</INF> stations in areas where MSA populations exceed 1,000,000 
must be in the range from 2 to 10 stations, while in low population 
urban areas, no more than two stations are required. A range of 
monitoring stations is specified in table 4 because sources of 
pollutants and local control efforts can vary from one part of the 
country to another and therefore, some flexibility is allowed in 
selecting the actual number of stations in any one locale.
    3.7.2 Through promulgation of the NAAQS for PM<INF>2.5</INF>, the 
number of PM<INF>10</INF> SLAMS is expected to decrease, but 
requirements to maintain PM<INF>10</INF> NAMS remain in effect. The 
PM<INF>10</INF> NAMS are retained to provide trends data, to support 
national assessments and decisions, and in some cases to continue 
demonstration that a NAAQS for PM<INF>10</INF> is maintained as a 
requirement under a State Implementation Plan.
    3.7.3 The PM<INF>2.5</INF> NAMS shall be a subset of the core 
PM<INF>2.5</INF> SLAMS and other SLAMS intended to monitor for regional 
transport. The PM<INF>2.5</INF> NAMS are planned as long-term monitoring 
stations concentrated in metropolitan areas. A target range of 200 to 
300 stations shall be designated nationwide. The largest metropolitan 
areas (those with a population greater than approximately one million) 
shall have at least one PM<INF>2.5</INF> NAMS stations.
    3.7.4 The number of total PM<INF>2.5</INF> NAMS per Region will be 
based on recommendations of the EPA Regional Offices, in concert with 
their State and local agencies, in accordance with the network design 
goals described in sections 3.7.5 through 3.7.7 of this appendix. The 
selected stations should represent the

[[Page 265]]

range of conditions occurring in the Regions and will consider factors 
such as total number or type of sources, ambient concentrations of 
particulate matter, and regional transport.
    3.7.5 The approach for PM<INF>2.5</INF> NAMS is intended to give 
State and local agencies maximum flexibility while apportioning a 
limited national network. By advancing a range of monitors per Region, 
EPA intends to balance the national network with respect to geographic 
area and population. Table 5 presents the target number of 
PM<INF>2.5</INF> NAMS per Region to meet the national goal of 200 to 300 
stations. These numbers consider a variety of factors such as Regional 
differences in metropolitan population, population density, land area, 
sources of particulate emissions, and the numbers of PM<INF>10</INF> 
NAMS.
    3.7.6 States will be required to establish approximately 50 NAMS 
sites for routine chemical speciation of PM<INF>2.5</INF>. These sites 
will include those collocated at approximately 25 PAMS sites and 
approximately 25 other core SLAMS sites to be selected by the 
Administrator. After 5 years of data collection, the Administrator may 
exempt some sites from collecting speciated data. The number of NAMS 
sites at which speciation will be performed each year and the number of 
samples per year will be determined by the Administrator.
    3.7.7 Since emissions associated with the operation of motor 
vehicles contribute to urban area particulate matter levels, 
consideration of the impact of these sources must be included in the 
design of the NAMS network, particularly in MSAs greater than 500,000 
population. In certain urban areas particulate emissions from motor 
vehicle diesel exhaust currently is or is expected to be a significant 
source of particulate matter ambient levels. The actual number of NAMS 
and their locations must be determined by EPA Regional Offices and the 
State agencies, subject to the approval of the Administrator as required 
by Sec. 58.32. The Administrator's approval is necessary to ensure that 
individual stations conform to the NAMS selection criteria and that the 
network as a whole is sufficient in terms of number and location for 
purposes of national analyses.

                             Table 4--PM10 National Air Monitoring Station Criteria
                                  [Approximate Number of Stations per MSA] \1\
----------------------------------------------------------------------------------------------------------------
                                                                          High          Medium          Low
                        Population Category                          Concentration  Concentration  Concentration
                                                                          \2\            \3\            \4\
----------------------------------------------------------------------------------------------------------------
<ls-thn-eq>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 Selection of urban areas and actual number of stations per area will be jointly determined by EPA and the
  State agency.
2 High concentration areas are those for which ambient PM10 data show ambient concentrations exceeding either
  PM10 NAAQS by 20 percent or more.
3 Medium concentration areas are those for which ambient PM10 data show ambient concentrations exceeding 80
  percent of the PM10 NAAQS.
4 Low concentration areas are those for which ambient PM10 data show ambient concentrations less than 80 percent
  of the PM10 NAAQS.

    3.7.7.1 Selection of urban areas and actual number of stations per 
area will be jointly determined by EPA and the State agency.
    3.7.7.2 High concentration areas are those for which: Ambient 
PM<INF>10</INF> data show ambient concentrations exceeding either 
PM<INF>10</INF> NAAQS by 20 percent or more.
    3.7.7.3 Medium concentration areas are those for which: Ambient 
PM<INF>10</INF> data show ambient concentrations exceeding either 80 
percent of the PM<INF>10</INF> NAAQS.
    3.7.7.4 Low concentration areas are those for which: Ambient 
PM<INF>10</INF> data show ambient concentrations less than 80 percent of 
the PM<INF>10</INF> NAAQS.

            Table 5--Goals for Number of PM2.5 NAMS by Region
------------------------------------------------------------------------
                                                   Percent of National
      EPA Region           Number of NAMS \1\             Total
------------------------------------------------------------------------
1                       15 to 20                 6 to 8
2                       20 to 30                 8 to 12
3                       20 to 25                 8 to 10
4                       35 to 50                 14 to 20
5                       35 to 50                 14 to 20
6                       25 to 35                 10 to 14
7                       10 to 15                 4 to 6
8                       10 to 15                 4 to 6
9                       25 to 40                 10 to 16
10                      10 to 15                 4 to 6
                       --------------------------
    Total               205-295                  100
------------------------------------------------------------------------
\1\ Each region will have one to three NAMS having the monitoring of
  regional transport as a primary objective.

4. Network Design for Photochemical Assessment Monitoring Stations 
(PAMS)

    In order to obtain more comprehensive and representative data on 
O<INF>3</INF> air pollution, the 1990 Clean Air Act Amendments require 
enhanced monitoring for ozone (O<INF>3</INF>), oxides of nitrogen (NO, 
NO<INF>2</INF>, and NO<INF>X</INF>), and monitoring for VOC in 
O<INF>3</INF> nonattainment areas classified as serious, severe, or 
extreme. This will be accomplished through the establishment of a 
network of Photochemical Assessment Monitoring Stations (PAMS).

[[Page 266]]

    4.1 PAMS Data Uses. Data from the PAMS are intended to satisfy 
several coincident needs related to attainment of the National Ambient 
Air Quality Standards (NAAQS), SIP control strategy development and 
evaluation, corroboration of emissions tracking, preparation of trends 
appraisals, and exposure assessment.
    (a) NAAQS attainment and control strategy development. Like SLAMS 
and NAMS data, PAMS data will be used for monitoring O<INF>3</INF> 
exceedances and providing input for attainment/nonattainment decisions. 
In addition, PAMS data will help resolve the roles of transported and 
locally emitted O<INF>3</INF> precursors in producing an observed 
exceedance and may be utilized to identify specific sources emitting 
excessive concentrations of O<INF>3</INF> precursors and potentially 
contributing to observed exceedances of the O<INF>3</INF> NAAQS. The 
PAMS data will enhance the characterization of O<INF>3</INF> 
concentrations and provide critical information on the precursors which 
cause O<INF>3</INF>, therefore extending the database available for 
future attainment demonstrations. These demonstrations will be based on 
photochemical grid modeling and other approved analytical methods and 
will provide a basis for prospective mid-course control strategy 
corrections. PAMS data will provide information concerning (1) which 
areas and episodes to model to develop appropriate control strategies; 
(2) boundary conditions required by the models to produce quantifiable 
estimates of needed emissions reductions; and (3) the evaluation of the 
predictive capability of the models used.
    (b) SIP control strategy evaluation. The PAMS will provide data for 
SIP control strategy evaluation. Long-term PAMS data will be used to 
evaluate the effectiveness of these control strategies. Data may be used 
to evaluate the impact of VOC and NO<INF>X</INF> emission reductions on 
air quality levels for O<INF>3</INF> if data is reviewed following the 
time period during which control measures were implemented. Speciation 
of measured VOC data will allow determination of which organic species 
are most affected by the emissions reductions and assist in developing 
cost-effective, selective VOC reductions and control strategies. A State 
or local air pollution control agency can therefore ensure that 
strategies which are implemented in their particular nonattainment area 
are those which are best suited for that area and achieve the most 
effective emissions reductions (and therefore largest impact) at the 
least cost.
    (c) Emissions tracking. PAMS data will be used to corroborate the 
quality of VOC and NO<INF>X</INF> emission inventories. Although a 
perfect mathematical relationship between emission inventories and 
ambient measurements does not yet exist, a qualitative assessment of the 
relative contributions of various compounds to the ambient air can be 
roughly compared to current emission inventory estimates to evaluate the 
accuracy of the emission inventories. In addition, PAMS data which are 
gathered year round will allow tracking of VOC and NO<INF>X</INF> 
emission reductions, provide additional information necessary to support 
Reasonable Further Progress (RFP) calculations, and corroborate 
emissions trends analyses. While the regulatory assessments of progress 
will be made in terms of emission inventory estimates, the ambient data 
can provide independent trends analyses and corroboration of these 
assessments which either verify or highlight possible errors in 
emissions trends indicated by inventories. The ambient assessments, 
using speciated data, can gauge the accuracy of estimated changes in 
emissions. The speciated data can also be used to assess the quality of 
the VOC speciated and NO<INF>X</INF> emission inventories for input 
during photochemical grid modeling exercises and identify potential 
urban air toxic pollutant problems which deserve closer scrutiny.
    The speciated VOC data will be used to determine changes in the 
species profile, resulting from the emission control program, 
particularly those resulting from the reformulation of fuels.
    (d) Trends. Long-term PAMS data will be used to establish speciated 
VOC, NO<INF>X</INF>, and limited toxic air pollutant trends, and 
supplement the O<INF>3</INF> trends database. Multiple statistical 
indicators will be tracked, including O<INF>3</INF> and its precursors 
during the events encompassing the days during each year with the 
highest O<INF>3</INF> concentrations, the seasonal means for these 
pollutants, and the annual means at representative locations.
    The more PAMS that are established in and near nonattainment areas, 
the more effective the trends data will become. As the spatial 
distribution and number of O<INF>3</INF> and O<INF>3</INF> precursor 
monitors improves, trends analyses will be less influenced by instrument 
or site location anomalies. The requirement that surface meteorological 
monitoring be established at each PAMS will help maximize the utility of 
these trends analyses by comparisons with meteorological trends, and 
transport influences. The meteorological data can also help interpret 
the ambient air pollution trends by taking meteorological factors into 
account.
    (e) Exposure assessment. PAMS data will be used to better 
characterize O<INF>3</INF> and toxic air pollutant exposure to 
populations living in serious, severe, or extreme areas. Annual mean 
toxic air pollutant concentrations will be calculated to help estimate 
the average risk to the population associated with individual VOC 
species, which are considered toxic, in urban environments.
    4.2 PAMS Monitoring Objectives. Unlike the SLAMS and NAMS design 
criteria which are pollutant specific, PAMS design criteria are site 
specific. Concurrent measurements of O<INF>3</INF>, NO<INF>X</INF>, 
speciated VOC, and meteorology

[[Page 267]]

are obtained at PAMS. Design criteria for the PAMS network are based on 
selection of an array of site locations relative to O<INF>3</INF> 
precursor source areas and predominant wind directions associated with 
high O<INF>3</INF> events. Specific monitoring objectives are associated 
with each location. The overall design should enable characterization of 
precursor emission sources within the area, transport of O<INF>3</INF> 
and its precursors into and out of the area, and the photochemical 
processes related to O<INF>3</INF> nonattainment, as well as developing 
an initial, though limited, urban air toxic pollutant database. Specific 
objectives that must be addressed include assessing ambient trends in 
O<INF>3</INF>, NO, NO<INF>2</INF>, NO<INF>X</INF>, VOC (including 
carbonyls), and VOC species, determining spatial and diurnal variability 
of O<INF>3</INF>, NO, NO<INF>2</INF>, NO<INF>X</INF>, and VOC species 
and assessing changes in the VOC species profiles that occur over time, 
particularly those occurring due to the reformulation of fuels. A 
maximum of five PAMS sites are required in an affected nonattainment 
area depending on the population of the Metropolitan Statistical Area/
Consolidated Metropolitan Statistical Area (MSA/CMSA) or nonattainment 
area, whichever is larger. Specific monitoring objectives associated 
with each of these sites result in four distinct site types. Note that 
detailed guidance for the locating of these sites may be found in 
reference 19.
    Type (1) sites are established to characterize upwind background and 
transported O<INF>3</INF> and its precursor concentrations entering the 
area and will identify those areas which are subjected to overwhelming 
transport. Type (1) sites are located in the predominant morning upwind 
direction from the local area of maximum precursor emissions during the 
O<INF>3</INF> season and at a distance sufficient to obtain urban scale 
measurements as defined in section 1 of this appendix. Typically, type 
(1) sites will be located near the edge of the photochemical grid model 
domain in the predominant morning upwind direction from the city limits 
or fringe of the urbanized area. Depending on the boundaries and size of 
the nonattainment area and the orientation of the grid, this site may be 
located outside of the nonattainment area. The appropriate predominant 
morning wind direction should be determined from historical wind data 
occurring during the period 7 a.m. to 10 a.m. on high O<INF>3</INF> days 
or on those days which exhibit the potential for producing high 
O<INF>3</INF> levels, i.e., O<INF>3</INF>-conducive days as described in 
reference 25. Alternate schemes for specifying this morning wind 
direction may be submitted as a part of the network description required 
by Sec. Sec. 58.40 and 58.41. Data measured at type (1) sites will be 
used principally for the following purposes:
    <bullet<ls-thn-eq> Future development and evaluation of control 
strategies,
    <bullet<ls-thn-eq> Identification of incoming pollutants,
    <bullet<ls-thn-eq> Corroboration of NO<INF>X</INF> and VOC emission 
inventories,
    <bullet<ls-thn-eq> Establishment of boundary conditions for future 
photochemical grid modeling and mid-course control strategy changes, and
    <bullet<ls-thn-eq> Development of incoming pollutant trends.
    Type (2) sites are established to monitor the magnitude and type of 
precursor emissions in the area where maximum precursor emissions are 
expected to impact and are suited for the monitoring of urban air toxic 
pollutants. Type (2) sites are located immediately downwind of the area 
of maximum precursor emissions and are typically placed near the 
downwind boundary of the central business district to obtain 
neighborhood scale measurements. The appropriate downwind direction 
should be obtained similarly to that for type (1) sites. Additionally, a 
second type (2) site may be required depending on the size of the area, 
and should be placed in the second-most predominant morning wind 
direction as noted previously. Data measured at type (2) sites will be 
used principally for the following purposes:
    <bullet<ls-thn-eq> Development and evaluation of imminent and future 
control strategies,
    <bullet<ls-thn-eq> Corroboration of NO<INF>X</INF> and VOC emission 
inventories,
    <bullet<ls-thn-eq> Augmentation of RFP tracking,
    <bullet<ls-thn-eq> Verification of photochemical grid model 
performance,
    <bullet<ls-thn-eq> Characterization of O<INF>3</INF> and toxic air 
pollutant exposures (appropriate site for measuring toxic emissions 
impact),
    <bullet<ls-thn-eq> Development of pollutant trends, particularly 
toxic air pollutants and annual ambient speciated VOC trends to compare 
with trends in annual VOC emission estimates, and
    <bullet<ls-thn-eq> Determination of attainment with the NAAQS for 
NO<INF>2</INF> and O<INF>3</INF>.
    Type (3) sites are intended to monitor maximum O<INF>3</INF> 
concentrations occurring downwind from the area of maximum precursor 
emissions. Locations for type (3) sites should be chosen so that urban 
scale measurements are obtained. Typically, type (3) sites will be 
located 10 to 30 miles downwind from the fringe of the urban area. The 
downwind direction should also be determined from historical wind data, 
but should be identified as those afternoon winds occurring during the 
period 1 p.m. to 4 p.m. on high O<INF>3</INF> days or on those days 
which exhibit the potential for producing high O<INF>3</INF> levels. 
Alternate schemes for specifying this afternoon wind direction may also 
be submitted as a part of the network description required by Sec. Sec. 
58.40 and 58.41. Data measured at type (3) sites will be used 
principally for the following purposes:
    <bullet<ls-thn-eq> Determination of attainment with the NAAQS for 
O<INF>3</INF> (this site may coincide with an existing maximum 
concentration O<INF>3</INF> monitoring site),

[[Page 268]]

    <bullet<ls-thn-eq> Evaluation of future photochemical grid modeling 
applications,
    <bullet<ls-thn-eq> Future development and evaluation of control 
strategies,
    <bullet<ls-thn-eq> Development of pollutant trends, and
    <bullet<ls-thn-eq> Characterization of O<INF>3</INF> pollutant 
exposures.
    Type (4) sites are established to characterize the extreme downwind 
transported O<INF>3</INF> and its precursor concentrations exiting the 
area and will identify those areas which are potentially contributing to 
overwhelming transport in other areas. Type (4) sites are located in the 
predominant afternoon downwind direction, as determined for the type (3) 
site, from the local area of maximum precursor emissions during the 
O<INF>3</INF> season and at a distance sufficient to obtain urban scale 
measurements as defined elsewhere in this appendix. Typically, type (4) 
sites will be located near the downwind edge of the photochemical grid 
model domain. Alternate schemes for specifying the location of this site 
may be submitted as a part of the network description required by 
Sec. Sec. 58.40 and 58.41. Data measured at type (4) sites will be used 
principally for the following purposes:
    <bullet<ls-thn-eq> Development and evaluation of O<INF>3</INF> 
control strategies,
    <bullet<ls-thn-eq> Identification of emissions and photochemical 
products leaving the area,
    <bullet<ls-thn-eq> Establishment of boundary conditions for 
photochemical grid modeling,
    <bullet<ls-thn-eq> Development of pollutant trends,
    <bullet<ls-thn-eq> Background and upwind information for other 
downwind areas, and
    <bullet<ls-thn-eq> Evaluation of photochemical grid model 
performance.
    States choosing to submit an individual network description for each 
affected nonattainment area, irrespective of its proximity to other 
affected areas, must fulfill the requirements for isolated areas as 
described in section 4 of this appendix, as an example, and illustrated 
by Figure 5. States containing areas which experience significant impact 
from long-range transport or are proximate to other nonattainment areas 
(even in other States) should collectively submit a network description 
which contains alternative sites to those that would be required for an 
isolated area. Such a submittal should, as a guide, be based on the 
example provided in Figure 6, but must include a demonstration that the 
design satisfies the monitoring data uses and fulfills the PAMS 
monitoring objectives described in sections 4.1 and 4.2 of this 
appendix.

[[Page 269]]

[GRAPHIC] [TIFF OMITTED] TR18JY97.178

[[Page 270]]

[GRAPHIC] [TIFF OMITTED] TR18JY97.179

    Alternative PAMS network designs should, on a site-by-site basis, 
provide those data necessary to enhance the attainment/nonattainment 
database for criteria pollutants and explain the origins of overwhelming 
O<INF>3</INF> transport. The alternative PAMS data should be usable for 
the corroboration and verification of O<INF>3</INF> precursor emissions 
inventories and should comprise a qualitative (if not quantitative) 
measure of the accuracy of RFP calculations. The data should be 
sufficient to evaluate the effectiveness of the implemented 
O<INF>3</INF> control strategies and should provide data necessary to 
establish photochemical grid modeling boundary conditions and necessary 
inputs including appropriate meteorological parameters, and provide 
measurements which can serve as model evaluation tools. Further, 
utilizing its PAMS database (alternative or not), a State should be able 
to draw conclusions regarding population exposure and conduct trends 
analyses for both criteria and non-criteria pollutants. Overall, the 
PAMS network should serve as one of several complementary means, 
together with modeling and analysis of other data bases (e.g., 
inventories) and availability of control technology, etc., for States to 
justify the modification of existing control programs, design

[[Page 271]]

new programs, and evaluate future courses of actions for O<INF>3</INF> 
control.
    4.3 Monitoring Period. PAMS precursor monitoring will be conducted 
annually throughout the months of June, July and August (as a minimum) 
when peak O<INF>3</INF> values are expected in each area; however, 
precursor monitoring during the entire O<INF>3</INF> season for the area 
is preferred. Alternate precursor monitoring periods may be submitted 
for approval as a part of the PAMS network description required by Sec. 
58.40. Changes to the PAMS monitoring period must be identified during 
the annual SLAMS Network Review specified in Sec. 58.20. PAMS 
O<INF>3</INF> monitors must adhere to the O<INF>3</INF> monitoring 
season specified in section 2.5 of appendix D. To ensure a degree of 
national consistency, monitoring for the 1993 season should commence as 
follows:
    One in 3-day sampling--June 3, 1993.
    One in 6-day sampling--June 6, 1993.
    These monitoring dates will thereby be coincident with the 
previously-established, intermittent schedule for particulate matter. 
States initiating sampling earlier (or later) than June 3, 1993 should 
adjust their schedules to coincide with this national schedule.
    4.4 Minimum Monitoring Network Requirements. The minimum required 
number and type of monitoring sites and sampling requirements are based 
on the population of the affected MSA/CMSA or nonattainment area 
(whichever is larger). The MSA/CMSA basis for monitoring network 
requirements was chosen because it typically is the most representative 
of the area which encompasses the emissions sources contributing to 
nonattainment. The MSA/CMSA emissions density can also be effectively 
and conveniently portrayed by the surrogate of population. Additionally, 
a network which is adequate to characterize the ambient air of an MSA/
CMSA often must extend beyond the boundaries of such an area (especially 
for O<INF>3</INF> and its precursors); therefore, the use of smaller 
geographical units (such as counties or nonattainment areas which are 
smaller than the MSA/CMSA) for monitoring network design purposes is 
inappropriate. Various sampling requirements are imposed according to 
the size of the area to accommodate the impact of transport on the 
smaller MSAs/CMSAs, to account for the spatial variations inherent in 
large areas, to satisfy the differing data needs of large versus small 
areas due to the intractability of the O<INF>3</INF> nonattainment 
problem, and to recognize the potential economic impact of 
implementation on State and local government. Population figures must 
reflect the most recent decennial U.S. census population report. 
Specific guidance on determining network requirements is provided in 
reference 19. Minimum network requirements are outlined in table 2.

        Table 2--PAMS Minimum Monitoring Network Requirements \1\
------------------------------------------------------------------------
                                                 Minimum       Minimum
                                   Required     speciated     carbonyl
   Population of MSA/CMSA or      site type   VOC sampling    sampling
     nonattainment area \2\          \3\        frequency     frequency
                                                   \4\           \4\
------------------------------------------------------------------------
Less than 500,000..............  (\1\)        A or C        ............
                                 (\2\)        A or C        D or F \5\
500,000 to 1,000,000...........  (\1\)        A or C        ............
                                 (\2\)        B             E
                                 (\3\)        A or C        ............
1,000,000 to 2,000,000.........  (\1\)        A or C        ............
                                 (\2\)        B             E
                                 (\2\)        B             E
                                 (\3\)        A or C        ............
More than 2,000,000............  (\1\)        A or C        ............
                                 (\2\)        B             E
                                 (\2\)        B             E
                                 (\3\)        A or C        ............
                                 (\4\)        A or C        ............
------------------------------------------------------------------------
\1\ O3 and NOX (including NO and NO2) monitoring should be continuous
  measurements.
\2\ Whichever area is larger.
\3\ See Figure 5.
\4\ Frequency Requirements are as follows: A--Eight 3-hour samples every
  third day and one additional 24-hour sample every sixth day during the
  monitoring period; B--Eight 3-hour samples, every day during the
  monitoring period and one additional 24-hour sample every sixth day
  year-round; C--Eight 3-hour samples on the 5 peak O3 days plus each
  previous day, eight 3-hour samples every sixth day, and one additional
  24-hour sample every sixth day, during the monitoring period; D--Eight
  3-hour samples every third day during the monitoring period; E--Eight
  3-hour samples every day during the monitoring period; F--Eight 3-hour
  samples on the 5 peak O3 days plus each previous day and eight 3-hour
  samples every sixth day during the monitoring period. (NOTE: multiple
  samples taken on a daily basis must begin at midnight and consist of
  sequential, non-overlapping sampling periods.)
\5\ Carbonyl sampling frequency must match the chosen speciated VOC
  frequency.
Note that the use of Frequencies C or F requires the submittal of an
  ozone event forecasting scheme.

    For purposes of network implementation and transition, EPA 
recommends the following priority order for the establishment of sites:
    <bullet<ls-thn-eq> The type (2) site which provides the most 
comprehensive data concerning O<INF>3</INF> precursor emissions and 
toxic air pollutants,
    <bullet<ls-thn-eq> The type (3) site which provides a maximum 
O<INF>3</INF> measurement and total conversion of O<INF>3</INF> 
precursors,
    <bullet<ls-thn-eq> The type (1) site which delineates the effect of 
incoming precursor emissions and concentrations of O<INF>3</INF> and 
provides upwind boundary conditions,
    <bullet<ls-thn-eq> The type (4) site which provides extreme downwind 
boundary conditions, and
    <bullet<ls-thn-eq> The second type (2) site which provides 
comprehensive data concerning O<INF>3</INF> precursor emissions and 
toxic air pollutants in the second-most predominant morning wind 
direction on high O<INF>3</INF> days.
    Note also that O<INF>3</INF> event (peak day) monitoring will 
require the development of a scheme for forecasting such high 
O<INF>3</INF> days or will necessitate the stipulation of what 
meteorological conditions constitute a potential high O<INF>3</INF> day; 
monitoring could then be

[[Page 272]]

triggered only via meteorological projections. The O<INF>3</INF> event 
forecasting and monitoring scheme should be submitted as a part of the 
network description required by Sec. Sec. 58.40 and 58.41 and should be 
reviewed during each annual SLAMS Network Review specified in Sec. 
58.20.
    4.5 Transition Period. A variable period of time is proposed for 
phasing in the operation of all required PAMS. Within 1 year after (1) 
February 12, 1993, (2) or date of redesignation or reclassification of 
any existing O<INF>3</INF> nonattainment area to serious, severe, or 
extreme, or (3) the designation of a new area and classification to 
serious, severe, or extreme O<INF>3</INF> nonattainment, a minimum of 
one type (2) site must be operating. Operation of the remaining sites 
must, at a minimum, be phased in at the rate of one site per year during 
subsequent years as outlined in the approved PAMS network description 
provided by the State.
    4.6 Meteorological Monitoring. In order to support monitoring 
objectives associated with the need for various air quality analyses, 
model inputs and performance evaluations, meteorological monitoring 
including wind measurements at 10 meters above ground is required at 
each PAMS site. Monitoring should begin with site establishment. In 
addition, upper air meteorological monitoring is required for each PAMS 
area. Upper air monitoring should be initiated as soon as possible, but 
no later than 2 years after (1) February 12, 1993, (2) or date of 
redesignation or reclassification of any existing O<INF>3</INF> 
nonattainment area to serious, severe, or extreme, or (3) the 
designation of a new area and classification to serious, severe, or 
extreme O<INF>3</INF> nonattainment. The upper air monitoring site may 
be located separately from the type (1) through (4) sites, but the 
location should be representative of the upper air data in the 
nonattainment area. Upper air meteorological data must be collected 
during those days specified for monitoring by the sampling frequencies 
in table 2. of section 4.4 of this appendix D in accordance with current 
EPA guidance.

5. Summary.

    Table 6 of this appendix shows by pollutant, all of the spatial 
scales that are applicable for SLAMS and the required spatial scales for 
NAMS. There may also be some situations, as discussed later in appendix 
E of this part, where additional scales may be allowed for NAMS 
purposes.

                    Table 6--Summary of Spatial Scales for SLAMS and Required Scales for NAMS
----------------------------------------------------------------------------------------------------------------
                                                          Scales Applicable for SLAMS
        Spatial Scale        -----------------------------------------------------------------------------------
                                  SO2         CO          O3          NO2         Pb         PM10        PM2.5
----------------------------------------------------------------------------------------------------------------
Micro.......................  ..........   [bcheck]   ..........  ..........   [bcheck]    [bcheck]    [bcheck]
Middle......................   [bcheck]    [bcheck]    [bcheck]    [bcheck]    [bcheck]    [bcheck]    [bcheck]
Neighborhood................   [bcheck]    [bcheck]    [bcheck]    [bcheck]    [bcheck]    [bcheck]    [bcheck]
Urban.......................   [bcheck]   ..........   [bcheck]    [bcheck]    [bcheck]    [bcheck]    [bcheck]
Regional....................   [bcheck]   ..........   [bcheck]   ..........   [bcheck]    [bcheck]    [bcheck]

                                                           Scales Required for NAMS

Micro.......................  ..........   [bcheck]   ..........  ..........   [bcheck]    [bcheck]   [bcheck]1
Middle......................  ..........  ..........  ..........  ..........   [bcheck]    [bcheck]    [bcheck]1
Neighborhood................   [bcheck]    [bcheck]    [bcheck]    [bcheck]    [bcheck]    [bcheck]    [bcheck]
Urban.......................  ..........  ..........   [bcheck]    [bcheck]   ..........  ..........  [bcheck]2
Regional....................  ..........  ..........  ..........  ..........  ..........  ..........  [bcheck]2
----------------------------------------------------------------------------------------------------------------
\1\ Only permitted if representative of many such micro-scale environments in a residential district (for middle
  scale, at least two).
\2\ Either urban or regional scale for regional transport sites.

6. References

    1. Ludwig, F. L., J. H. S. 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.
    2. Ball, R. J. and G. E. Anderson. Optimum Site Exposure Criteria 
for SO<INF>2</INF> Monitoring. The Center for the Environment and Man, 
Inc., Hartford, CT. Prepared for U.S. Environmental Protection Agency, 
Research Triangle Park, NC. EPA Publication No. EPA-450/3-77-013. April 
1977.
    3. 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.
    4. Ludwig, F. L. and E. Shelar. Site Selecting 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.
    5. Guideline on Air Quality Models. OAQPS, U.S. Environmental 
Protection

[[Page 273]]

Agency, Research Triangle Park, NC. OAQPS No. 1.2-080. April 1978.
    6. Lead Guideline Document, U. S. Environmental Protection Agency, 
Research Triangle Park, NC. EPA-452/R-93-009.
    7. 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.)
    8. Johnson, D. E., et al. Epidemiologic Study of the Effects of 
Automobile Traffic on Blood Lead Levels, Southwest Research Institute, 
Houston, TX. Prepared for U.S. Environmental Protection Agency, Research 
Triangle Park, NC. EPA-600/1-78-055. August 1978.
    9. 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.)
    10. ``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.
    11. Cooper, J.A., et. al. Summary of the Portland Aerosol 
Characterization Study. (Presented at the 1979 Annual Air Pollution 
Association Meeting, Cincinnati, OH. APCA <greek-i>79-24.4).
    12. Bradway, R.M. and F.A. Record. National Assessment of the Urban 
Particulate Problem. Volume 1. Prepared for U.S. Environmental 
Protection Agency, Research Triangle Park, NC. EPA-450/3-76-024. July 
1976.
    13. U.S. Environmental Protection Agency, Air Quality Criteria for 
Particulate Matter and Sulfur Oxides, Volume 2. Environmental Criteria 
and Assessment Office, Research Triangle Park, NC. December 1981.
    14. Watson, J.G., et al. Analysis of Inhalable and Fine Particulate 
Matter Measurements. Prepared for U.S. Environmental Protection Agency, 
Research Triangle Park, NC. EPA-450/4-81-035. December 1981.
    15. Record, F.A. and L.A. Baci. Evaluation on Contribution of Wind 
Blown Dust from the Desert Levels of Particulate Matter in Desert 
Communities. GCA Technology Division, Bedford, MA. Prepared for U.S. 
Environmental Protection Agency, Research Triangle Park, NC. EPA-450/2-
80-078. August 1980.
    16. Goldstein, E.A. and Paly M. The Diesel Problem in New York City. 
Project on the Urban Environment. Natural Resources Defense Council, 
Inc., New York, NY. April 1985.
    17. 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.
    18. Watson et al. Guidance for Network Design and Optimum Site 
Exposure for PM<INF>2.5</INF> and PM<INF>10</INF>. Prepared for U.S. 
Environmental Protection Agency, Research Triangle Park, NC.
    19. National Air Pollutant Emissions Trends, 1900-1995, Office of 
Air Quality Planning and Standards, U. S. Environmental Protection 
Agency, Research Triangle Park, NC. EPA-454/R96-007, October 1996, 
updated annually.

[44 FR 27571, May 10, 1979]

    Editorial Note: For Federal Register citations affecting appendix D 
to part 58, see the List of CFR Sections Affected, which appears in the 
Finding Aids section of the printed volume and on GPO Access.

    Effective Date Note: At 60 FR 52323, October 6, 1995, appendix D to 
part 58 was amended in part by adding Section 2.2. This section contains 
information collection and recordkeeping requirements and will not 
become effective until approval has been given by the Office of 
Management and Budget.

  Appendix E to Part 58--Probe and Monitoring Path Siting Criteria for 
                     Ambient Air Quality Monitoring

    1. Introduction
    2 Sulfur Dioxide (SO<INF>2</INF>), Ozone (O<INF>3</INF>), and 
Nitrogen Dioxide (NO<INF>2</INF>)
    2.1 Horizontal and Vertical Placement
    2.2 Spacing from Minor Sources (Applicable to SO<INF>2</INF> and 
O<INF>3</INF> Monitoring Only)
    2.3 Spacing From Obstructions
    2.4 Spacing From Trees
    2.5 Spacing From Roadways (Applicable to O<INF>3</INF> and 
NO<INF>2</INF> Only)
    2.6 Cumulative Interferences on a Monitoring Path
    2.7 Maximum Monitoring Path Length
    3 [Reserved]
    4. Carbon Monoxide (CO)
    4.1 Horizontal and Vertical Placement
    4.2 Spacing From Obstructions
    4.3 Spacing From Roadways
    4.4 Spacing From Trees and Other Considerations
    4.5 Cumulative Interferences on a Monitoring Path
    4.6 Maximum Monitoring Path Length
    5-6 [Reserved]
    7. Lead(Pb)
    7.1 Vertical Placement
    7.2 Spacing From Obstructions
    7.3 Spacing From Roadways
    7.4 Spacing From Trees and Other Considerations.
    8. Particulate Matter (PM<INF>10</INF> and PM<INF>2.5</INF>)

[[Page 274]]

    8.1 Vertical Placement
    8.2 Spacing From Obstructions
    8.3 Spacing From Roadways
    8.4 Other Considerations
    9. Probe Material and Pollutant Sample Residence Time
    10. Photochemical Assessment Monitoring Stations (PAMS)
    10.1 Horizontal and Vertical Placement
    10.2 Spacing From Obstructions
    10.3 Spacing From Roadways
    10.4 Spacing From Trees
    11. Discussion and Summary
    12. Summary
    13. References

1. Introduction
    This appendix contains specific location criteria applicable to 
ambient air quality monitoring probes and monitoring paths after the 
general station siting has been selected based on the monitoring 
objectives and spatial scale of representation discussed in appendix D 
of this part. Adherence to these siting criteria is necessary to ensure 
the uniform collection of compatible and comparable air quality data.
    The probe and monitoring path siting criteria discussed below 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 how and why the 
proposed siting deviates 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 11 of this appendix.
    The spatial scales of representation used in this appendix, i.e., 
micro, middle, neighborhood, urban, and regional, are defined and 
discussed in appendix D of this part. 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 a ``must'' are defined as requirements and exceptions must be 
approved through the waiver provisions. However, siting criteria that 
are phrased with a ``should'' are defined as goals to meet for 
consistency but are not requirements.

2. Sulfur Dioxide (SO<INF>2</INF>), Ozone (O<INF>3</INF>), and Nitrogen 
Dioxide (NO<INF>2</INF>)

    Open path analyzers may be used to measure SO<INF>2</INF>, 
O<INF>3</INF>, and NO<INF>2</INF> at SLAMS/NAMS sites for middle, 
neighborhood, urban, and regional scale measurement applications. 
Additional information on SO<INF>2</INF>, NO<INF>2</INF>, and 
O<INF>3</INF> monitor siting criteria may be found in references 11 and 
13.
    2.1 Horizontal and Vertical Placement. The probe or at least 80 
percent of the monitoring path must be located between 3 and 15 meters 
above ground level. The probe or at least 90 percent of the monitoring 
path must be at least 1 meter vertically or horizontally away from any 
supporting structure, walls, parapets, penthouses, etc., and away from 
dusty or dirty areas. If the probe or a significant portion of the 
monitoring path is located near the side of a building, 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.
    2.2 Spacing from Minor Sources (Applicable to SO<INF>2</INF> and 
O<INF>3</INF> Monitoring Only). Local minor sources of SO<INF>2</INF> 
can cause inappropriately high concentrations of SO<INF>2</INF> in the 
vicinity of probes and monitoring paths for SO<INF>2</INF>. Similarly, 
local sources of nitric oxide (NO) and ozone-reactive hydrocarbons can 
have a scavenging effect causing unrepresentatively low concentrations 
of O<INF>3</INF> in the vicinity of probes and monitoring paths for 
O<INF>3</INF>. To minimize these potential interferences, the probe or 
at least 90 percent of the monitoring path must be away from furnace or 
incineration flues or other minor sources of SO<INF>2</INF> or NO, 
particularly for open path analyzers because of their potential for 
greater exposure over the area covered by the monitoring path. The 
separation distance should take into account the heights of the flues, 
type of waste or fuel burned, and the sulfur content of the fuel. It is 
acceptable, however, to monitor for SO<INF>2</INF> near a point source 
of SO<INF>2</INF> when the objective is to assess the effect of this 
source on the represented population.
    2.3 Spacing From Obstructions. Buildings and other obstacles may 
possibly scavenge SO<INF>2</INF>, O<INF>3</INF>, or NO<INF>2</INF>. To 
avoid this interference, the probe or at least 90 percent of the 
monitoring path must have unrestricted airflow and be located away from 
obstacles so that the distance from the probe or monitoring path is at 
least twice the height that the obstacle protrudes above the probe or 
monitoring path. Generally, a probe or monitoring path located near or 
along a vertical wall is undesirable because air moving along the wall 
may be subject to possible removal mechanisms. A probe must have 
unrestricted airflow in an arc of at least 270 degrees around the inlet 
probe, or 180 degrees if the probe is on the side of a building. This 
arc must include the predominant wind direction for the season of 
greatest pollutant concentration potential. A sampling station having a 
probe located closer to an obstacle than this criterion allows should be 
classified as middle scale rather than neighborhood or urban scale, 
since the measurements from such a station would more closely represent 
the middle scale. A monitoring path must be clear of all trees, brush, 
buildings, plumes, dust, or other optical obstructions,

[[Page 275]]

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 affect the ability of 
the open path analyzer to continuously measure pollutant concentrations.
    Special consideration must be devoted to the use of open path 
analyzers due to their inherent potential sensitivity to certain types 
of interferences, or optical obstructions. While some of these potential 
interferences are comparable to those to which point monitors are 
subject, there are additional sources of potential interferences which 
are altogether different in character. Transient, but significant 
obscuration of especially longer measurement paths could be expected to 
occur as a result of certain prevailing meteorological conditions (e.g., 
heavy fog, rain, snow) and/or aerosol levels that are of a sufficient 
density to prevent the open path analyzer's light transmission. If 
certain compensating measures are not otherwise implemented at the onset 
of monitoring (e.g., shorter path lengths, higher light source 
intensity), data recovery during periods of greatest primary pollutant 
potential could be compromised. For instance, if heavy fog or high 
particulate levels are coincident with periods of projected NAAQS-
threatening pollutant potential, the representativeness of the resulting 
data record in reflecting maximum pollutant concentrations may be 
substantially impaired despite the fact that the site may otherwise 
exhibit an acceptable, even exceedingly high overall valid data capture 
rate.
    In seeking EPA approval for inclusion of a site using an open path 
analyzer into the formal SLAMS/NAMS or PSD network, monitoring agencies 
must submit an analysis which evaluates both obscuration potential for a 
proposed path length for the subject area and the effect this potential 
is projected to have on the representativeness of the data record. This 
analysis should include one or more of the following elements, as 
appropriate for the specific circumstance: climatological information, 
historical pollutant and aerosol information, modeling analysis results, 
and any related special study results.
    2.4 Spacing From Trees. Trees can provide surfaces for 
SO<INF>2</INF>, O<INF>3</INF>, or NO<INF>2</INF> adsorption or reactions 
and obstruct wind flow. To reduce this possible interference, the probe 
or at least 90 percent of the monitoring path should be 20 meters or 
more from the drip line of trees. If a tree or trees could be considered 
an obstacle, the probe or 90 percent of the monitoring path must meet 
the distance requirements of section 2.3 and be at least 10 meters from 
the drip line of the tree or trees. Since the scavenging effect of trees 
is greater for O<INF>3</INF> than for other criteria pollutants, strong 
consideration of this effect must be given to locating an O<INF>3</INF> 
probe or monitoring path to avoid this problem.
    2.5 Spacing From Roadways (Applicable to O<INF>3</INF> and 
NO<INF>2</INF> Only). In siting an O<INF>3</INF> analyzer, it is 
important to minimize destructive interferences from sources of NO, 
since NO readily reacts with O<INF>3</INF>. In siting NO<INF>2</INF> 
analyzers for neighborhood and urban scale monitoring, it is important 
to minimize interferences from automotive sources. Table 1 provides the 
required minimum separation distances between a roadway and a probe and 
between a roadway and at least 90 percent of a monitoring path for 
various ranges of daily roadway traffic. A sampling station having a 
point analyzer probe located closer to a roadway than allowed by the 
table 1 requirements should be classified as middle scale rather than 
neighborhood or urban scale, since the measurements from such a station 
would more closely represent the middle scale. If an open path analyzer 
is used at a site, the monitoring path(s) must not cross over a roadway 
with an average daily traffic count of 10,000 vehicles per day or more. 
For those situations where a monitoring path crosses a roadway with 
fewer than 10,000 vehicles per day, one must consider the entire segment 
of the monitoring path in the area of potential atmospheric interference 
from automobile emissions. Therefore, this calculation must include the 
length of the monitoring path over the roadway plus any segments of the 
monitoring path that lie in the area between the roadway and the minimum 
separation distance, as determined from table 1. The sum of these 
distances must not be greater than 10 percent of the total monitoring 
path length.

   Table 1--Minimum Separation Distance Between Roadways and Probes or
Monitoring Paths for Monitoring Neighborhood--and Urban--Scale Ozone and
                            Nitrogen Dioxide
------------------------------------------------------------------------
                                                               Minimum
                                                             separation
      Roadway average daily traffic, vehicles per day       distance,\1\
                                                               meters
------------------------------------------------------------------------
<=10,000..................................................            10
15,000....................................................            20
20,000....................................................            30
40,000....................................................            50
70,000....................................................           100
[gteqt]110,000............................................           250
------------------------------------------------------------------------
\1\ Distance from the edge of the nearest traffic lane. The distance for
  intermediate traffic counts should be interpolated from the table
  values based on the actual traffic count.

    2.6 Cumulative Interferences on a Monitoring Path. The cumulative 
length or portion of a monitoring path that is affected by minor 
sources, obstructions, trees, or roadways must not exceed 10 percent of 
the total monitoring path length.

[[Page 276]]

    2.7 Maximum Monitoring Path Length. The monitoring path length must 
not exceed 1 kilometer for 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 station meets the objectives and 
spatial scales defined for SLAMS in appendix D. Therefore, the Regional 
Administrator or the Regional Administrator's designee may require 
shorter path lengths, as needed on an individual basis, to ensure that 
the SLAMS meet the appendix D requirements. Likewise, the Administrator 
or the Administrator's designee may specify the maximum path length used 
at monitoring stations designated as NAMS or PAMS as needed on an 
individual basis.
3. [Reserved]
4. Carbon Monoxide (CO)
    Open path analyzers may be used to measure CO at SLAMS/NAMS sites 
for middle or neighborhood scale measurement applications. Additional 
information on CO monitor siting criteria may be found in reference 12.
    4.1 Horizontal and Vertical Placement. Because of the importance of 
measuring population exposure to CO concentrations, air should be 
sampled at average breathing heights. However, practical factors require 
that the inlet probe be higher. The required height of the inlet probe 
for CO monitoring is therefore 3<plus-minus<ls-thn-eq>\1/2\ meters for a 
microscale site, which is a compromise between representative breathing 
height and prevention of vandalism. The recommended 1 meter range of 
heights is also a compromise to some extent. For consistency and 
comparability, it would be desirable to have all inlets at exactly the 
same height, but practical considerations often prevent this. Some 
reasonable range must be specified and 1 meter provides adequate leeway 
to meet most requirements.
    For the middle and neighborhood scale stations, the vertical 
concentration gradients are not as great as for the microscale station. 
This is because the diffusion from roads is greater and the 
concentrations would represent larger areas than for the microscale. 
Therefore, the probe or at least 80 percent of the monitoring path must 
be located between 3 and 15 meters above ground level for middle and 
neighborhood scale stations. The probe or at least 90 percent of the 
monitoring path must be at least 1 meter vertically or horizontally away 
from any supporting structure, walls, parapets, penthouses, etc., and 
away from dusty or dirty areas. If the probe or a significant portion of 
the monitoring path is located near the side of a building, then it 
should be located on the windward side of the building relative to both 
the prevailing wind direction during the season of highest concentration 
potential and the location of sources of interest, i.e., roadways.
    4.2 Spacing From Obstructions. Buildings and other obstacles may 
restrict airflow around a probe or monitoring path. To avoid this 
interference, the probe or at least 90 percent of the monitoring path 
must have unrestricted airflow and be located away from obstacles so 
that the distance from the probe or monitoring path is at least twice 
the height that the obstacle protrudes above the probe or monitoring 
path. A probe or monitoring path located near or along a vertical wall 
is undesirable because air moving along the wall may be subject to 
possible removal mechanisms. A probe must have unrestricted airflow in 
an arc of at least 270 degrees around the inlet probe, or 180 degrees if 
the probe is on the side of a building. This arc must include the 
predominant wind direction for the season of greatest pollutant 
concentration potential. 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 affect the ability of the open 
path analyzer to continuously measure pollutant concentrations.
    Special consideration must be devoted to the use of open path 
analyzers due to their inherent potential sensitivity to certain types 
of interferences, or optical obstructions. While some of these potential 
interferences are comparable to those to which point monitors are 
subject, there are additional sources of potential interferences which 
are altogether different in character. Transient, but significant 
obscuration of especially longer measurement paths could be expected to 
occur as a result of certain prevailing meteorological conditions (e.g., 
heavy fog, rain, snow) and/or aerosol levels that are of a sufficient 
density to prevent the open path analyzer's light transmission. If 
certain compensating measures are not otherwise implemented at the onset 
of monitoring (e.g., shorter path lengths, higher light source 
intensity), data recovery during periods of greatest primary pollutant 
potential could be compromised. For instance, if heavy fog or high 
particulate levels are coincident with periods of projected NAAQS-
threatening pollutant potential, the representativeness of the resulting 
data record in reflecting maximum pollutant concentrations may be 
substantially impaired despite

[[Page 277]]

the fact that the site may otherwise exhibit an acceptable, even 
exceedingly high overall valid data capture rate.
    In seeking EPA approval for inclusion of a site using an open path 
analyzer into the formal SLAMS/NAMS or PSD network, monitoring agencies 
must submit an analysis which evaluates both obscuration potential for a 
proposed path length for the subject area and the effect this potential 
is projected to have on the representativeness of the data record. This 
analysis should include one or more of the following elements, as 
appropriate for the specific circumstance: climatological information, 
historical pollutant and aerosol information, modeling analysis results, 
and any related special study results.
    4.3 Spacing From Roadways. Street canyon and traffic corridor 
stations (microscale) are intended to provide a measurement of the 
influence of the immediate source on the pollution exposure of the 
population. In order to provide some reasonable consistency and 
comparability in the air quality data from microscale stations, a 
minimum distance of 2 meters and a maximum distance of 10 meters from 
the edge of the nearest traffic lane must be maintained for these CO 
monitoring inlet probes. This should give consistency to the data, yet 
still allow flexibility of finding suitable locations.
    Street canyon/corridor (microscale) inlet probes must be located at 
least 10 meters from an intersection and 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. Also, the 
practical difficulty of positioning sampling inlets is less at midblock 
locations than at the intersection. However, the final siting of the 
monitor must meet the objectives and intent of appendix D, sections 2.4, 
3, 3.3, and appendix E, section 4.
    In determining the minimum separation between a neighborhood scale 
monitoring station and a specific line source, the presumption is made 
that measurements should not be substantially influenced by any one 
roadway. Computations were made to determine the separation distance, 
and table 2 provides the required minimum separation distance between 
roadways and a probe or 90 percent of a monitoring path. Probes or 
monitoring paths that are located closer to roads than this criterion 
allows should not be classified as a neighborhood scale, since the 
measurements from such a station would closely represent the middle 
scale. Therefore, stations not meeting this criterion should be 
classified as middle scale.

   Table 2--Minimum Separation Distance Between Roadways and Probes or
   Monitoring Paths for Monitoring Neighborhood Scale Carbon Monoxide
------------------------------------------------------------------------
                                                               Minimum
                                                              separation
                                                               distance
                                                               \1\ for
      Roadway average daily traffic, vehicles per day         probes or
                                                               90% of a
                                                              monitoring
                                                                 path
                                                               (meters)
------------------------------------------------------------------------
<=10,000...................................................           10
 15,000....................................................           25
 20,000....................................................           45
 30,000....................................................           80
 40,000....................................................          115
 50,000....................................................          135
 <=60,000..................................................          150
------------------------------------------------------------------------
\1\ Distance from the edge of the nearest traffic lane. The distance for
  intermediate traffic counts should be interpolated from the table
  values based on the actual traffic count.

    4.4 Spacing From Trees and Other Considerations. Since CO is 
relatively nonreactive, the major factor concerning trees is as 
obstructions to normal wind flow patterns. For middle and neighborhood 
scale stations, trees should not be located between the major sources of 
CO, usually vehicles on a heavily traveled road, and the monitor. The 
probe or at least 90 percent of the monitoring path must be 10 meters or 
more from the drip line of trees which are between the probe or the 
monitoring path and the road and which extend at least 5 meters above 
the probe or monitoring path. For microscale stations, no trees or 
shrubs should be located between the probe and the roadway.
    4.5 Cumulative Interferences on a Monitoring Path. The cumulative 
length or portion of a monitoring path that is affected by obstructions, 
trees, or roadways must not exceed 10 percent of the total monitoring 
path length.
    4.6 Maximum Monitoring Path Length. The monitoring path length must 
not exceed 1 kilometer for analyzers used for neighborhood scale 
monitoring applications, or 300 meters for middle scale monitoring 
applications. 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 station meets the objectives and spatial 
scales defined for SLAMS in appendix D. Therefore, the Regional 
Administrator or the Regional Administrator's designee may require 
shorter path lengths, as needed on an individual basis, to ensure that 
the SLAMS meet the appendix D requirements. Likewise, the Administrator 
or the Administrator's designee may specify the maximum path length used

[[Page 278]]

at monitoring stations designated as NAMS or PAMS as needed on an 
individual basis.
5.-6. [Reserved]
7. Lead (Pb)
    7.1 Vertical Placement. Optimal placement of the sampler inlet for 
Pb monitoring should be at breathing height level. However, practical 
factors such as prevention of vandalism, security, and safety 
precautions must also be considered when siting a Pb monitor. Given 
these considerations, the sampler inlet for microscale Pb monitors must 
be 2-7 meters above ground level. The lower limit was based on a 
compromise between ease of servicing the sampler and the desire to avoid 
unrepresentative conditions due to re-entrainment from dusty surfaces. 
The upper limit represents a compromise between the desire to have 
measurements which are most representative of population exposures and a 
consideration of the practical factors noted above.
    For middle or larger spatial scales, increased diffusion results in 
vertical concentration gradients which are not as great as for the small 
scales. Thus, the required height of the air intake for middle or larger 
scales is 2-15 meters.
    7.2 Spacing From Obstructions. The sampler must be located away from 
obstacles such as buildings, so that the distance between obstacles and 
the sampler is at least twice the height that the obstacle protrudes 
above the sampler.
    A minimum of 2 meters of separation from walls, parapets, and 
penthouses is required for rooftop samplers. No furnace or incinerator 
flues should be nearby. The height and type of flues and the type, 
quality, and quantity of waste or fuel burned determine the separation 
distances. For example, if the emissions from the chimney have high lead 
content and there is a high probability that the plume would impact on 
the sampler during most of the sampling period, then other buildings/
locations in the area that are free from the described sources should be 
chosen for the monitoring site.
    There must be unrestricted airflow in an arc of at least 270[deg] 
around the sampler.
Since the intent of the category (a) site is to measure the maximum 
concentrations from a road or point source, there must be no significant 
obstruction between a road or point source and the monitor, even though 
other spacing from obstruction criteria are met. The predominant 
direction for the season with the greatest pollutant concentration 
potential must be included in the 270[deg] arc.
    7.3. Spacing from Roadways. This criteria applies only to those Pb 
sites designed to assess lead concentrations from mobile sources. 
Numerous studies have shown that ambient Pb levels near mobile sources 
are a function of the traffic volume and are most pronounced at ADT 
<ls-thn-eq>30,000 within the first 15 meters on the downwind side of the 
roadways. Numberous studies have shown that ambient lead levels near 
mobile source are a function of the traffic volume and are most 
pronounced at ADT <ls-thn-eq>=30,000 within the first 15 meters, on the 
downwind side of the roadways. (1, 16-19) Therefore, stations to measure 
the peak concentration from mobile sources should be located at the 
distance most likely to produce the highest concentrations. For the 
microscale station, the location must be between 5 and 15 meters from 
the major roadway. For the middle scale station, a range of acceptable 
distances from the major roadway is shown in table 4. This table also 
includes separation distances between a roadway and neighborhood or 
larger scale stations. These distances are based upon the data of 
reference 16 which illustrates that lead levels remain fairly constant 
after certain horizontal distances from the roadway. As depicted in the 
above reference, this distance is a function of the traffic volume.

 Table 3--Separation Distance Between Pb Stations and Roadways (Edge of
                          Nearest Traffic Lane)
------------------------------------------------------------------------
                                          Separation distance between
                                         roadways and stations, meters
                                      ----------------------------------
    Roadway average daily traffic                           Neighborhood
           vehicles per day             Micro     Middle        urban
                                        scale      scale      regional
                                                                scale
------------------------------------------------------------------------
[lE]10,000...........................     5-15  \1\<ls-thn  \1\<ls-thn-e
                                                -15-50              q50
 20,000..............................     5-15  <ls-thn-eq  <ls-thn-eq>7
                                                >15-75                5
[gE]40,000...........................     5-15  <ls-thn-eq  <ls-thn-eq>1
                                                >15-100              00
------------------------------------------------------------------------
\1\ Distances should be interpolated based on traffic flow.

    7.4. Spacing from trees and other considerations. Trees can provide 
surfaces for deposition or adsorption of Pb particles and obstruct 
normal wind flow patterns. For microscale and middle scale category (a) 
sites there must not be any tree(s) between the source of the Pb and the 
sampler. For neighborhood scale category (b) sites, the sampler should 
be at least 20 meters from the drip line of trees. The sampler must, 
however, be placed at least 10 meters from the drip line of trees which 
could be classified as an obstruction, i.e., the distance between the 
tree(s) and the sampler is less than the height that the tree protrudes 
above the sampler.

8. Particulate Matter (PM<INF>10</INF> and PM<INF>2.5</INF>)

    8.1 Vertical Placement. Although there are limited studies on the 
PM<INF>10</INF> concentration gradients around roadways or other ground 
level sources, References 1, 2, 4, 18 and 19 of this appendix show a 
distinct variation in the distribution of TSP and Pb levels near 
roadways, TSP, which is greatly affected by gravity, has large 
concentration gradients, both horizontal and vertical, immediately 
adjacent to roads. Lead, being predominately

[[Page 279]]

sub-micron in size, behaves more like a gas and exhibits smaller 
vertical and horizontal gradients than TSP. PM<INF>10</INF>, being 
intermediate in size between these two extremes exhibits dispersion 
properties of both gas and settleable particulates and does show 
vertical and horizontal gradients. \30\ Similar to monitoring for other 
pollutants, optimal placement of the sampler inlet for PM<INF>10</INF> 
monitoring should be at breathing height level. However, practical 
factors such as prevention of vandalism, security, and safety 
precautions must also be considered when siting a PM<INF>10</INF> 
monitor. Given these considerations, the sampler inlet for microscale 
PM<INF>10</INF> monitors must be 2-7 meters above ground level. The 
lower limit was based on a compromise between ease of servicing the 
sampler and the desire to avoid re-entrainment from dusty surfaces. The 
upper limit represents a compromise between the desire to have 
measurements which are most representative of population exposures and a 
consideration of the practical factors noted above. Although microscale 
or middle scale stations are not the preferred spatial scale for 
PM<INF>2.5</INF> sites, there are situations where such sites are 
representative of several locations within an area where large segments 
of the population may live or work (e.g., central business district of 
Metropolitan area). In these cases, the sampler inlet for such 
microscale PM<INF>2.5</INF> stations must also be 2-7 meters above 
ground level.
    For middle or larger spatial scales, increased diffusion results in 
vertical concentration gradients that are not as great as for the 
microscale. Thus, the required height of the air intake for middle or 
larger scales is 2-15 meters.
    8.2 Spacing From Obstructions. If the sampler is located on a roof 
or other structure, then there must be a minimum of 2 meters separation 
from walls, parapets, penthouses, etc. No furnace or incineration flues 
should be nearby. This separation distance from flues is dependent on 
the height of the flues, type of waste or fuel burned, and quality of 
the fuel (ash content). In the case of emissions from a chimney 
resulting from natural gas combustion, as a precautionary measure, the 
sampler should be placed at least 5 meters from the chimney.
    On the other hand, if fuel oil, coal, or solid waste is burned and 
the stack is sufficiently short so that the plume could reasonably be 
expected to impact on the sampler intake a significant part of the time, 
other buildings/locations in the area that are free from these types of 
sources should be considered for sampling. Trees provide surfaces for 
particulate desposition and also restrict airflow. Therefore, the 
sampler should be placed at least 20 meters from the dripline and must 
be 10 meters from the dripline when the tree(s) acts as an obstruction.
    The sampler must also be located away from obstacles such as 
buildings, so that the distance between obstacles and the sampler is at 
least twice the height that the obstacle protrudes above the sampler 
except for street canyon sites. Sampling stations that are located 
closer to obstacles than this criterion allows should not be classified 
as neighborhood, urban, or regional scale, since the measurements from 
such a station would closely represent middle scale stations. Therefore, 
stations not meeting the criterion should be classified as middle scale.
    There must be unrestricted airflow in an arc of at least 270[deg] 
around the sampler except for street canyon sites. Since the intent of 
the category (a) site is to measure the maximum concentrations from a 
road or point source, there must be no significant obstruction between a 
road or point source and the monitor, even though other spacing from 
obstruction criteria are met. The predominant direction for the season 
with the greatest pollutant concentration potential must be included in 
the 270[deg] arc.
    8.3 Spacing From Roads. 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.
    The intent is to locate category (a) NAMS sites in areas of highest 
concentrations whether it be from 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 the microscale traffic corridor 
station, the location must be between 5 and 15 meters from the major 
roadway. For the microscale street canyon site the location must be 
between 2 and 10 meters from the roadway. For the middle scale station, 
a range of acceptable distances from the roadway is shown in Figure 2. 
This figure also includes separation distances between a roadway and 
neighborhood or larger scale stations by default. Any station, 2 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 2, if a PM sampler is primarily influenced by 
roadway emissions and that sampler is set back 10 meters from a 30,000 
ADT road, the station should be classified as a micro scale, if the 
sampler height is between 2 and 7 meters. If the sampler height is 
between 7 and 15 meters, the station should be classified as middle 
scale. If the sample 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.

[[Page 280]]

[GRAPHIC] [TIFF OMITTED] TC01JY92.003

    It is important to note that the separation distances shown in 
Figure 2 are measured from the edge of the nearest traffic lane of the 
roadway presumed to have the most influence on the site. In general, 
this presumption is an oversimplification of the usual urban settings 
which normally have several streets that impact a given site. The 
effects

[[Page 281]]

of surrounding streets, wind speed, wind direction and topography should 
be considered along with Figure 2 before a final decision is made on the 
most appropriate spatial scale assigned to the sampling station.
    8.4 Other Considerations. For those areas that are primarily 
influenced by stationary source emissions as opposed to roadway 
emissions, guidance in locating these areas may be found in the 
guideline document Optimum Network Design and Site Exposure Criteria for 
Particulate Matter. \2\\9\
    Stations should not be located in an unpaved area unless there is 
vegetative ground cover year round, so that the impact of wind blown 
dusts will be kept to a minimum.

9. Probe Material and Pollutant Sample Residence Time

    For the reactive gases, SO<INF>2</INF>, NO<INF>2</INF>, and 
O<INF>3</INF>, special probe material must be used for point analyzers. 
Studies <SUP>20-24</SUP> have been conducted to determine the 
suitability of materials such as polypropylene, polyethylene, polyvinyl 
chloride, Tygon, aluminum, brass, stainless steel, copper, Pyrex glass 
and Teflon for use as intake sampling lines. Of the above materials, 
only Pyrex glass and Teflon have been found to be acceptable for use as 
intake sampling lines for all the reactive gaseous pollutants. 
Furthermore, the EPA\25\ has specified borosilicate glass or FEP Teflon 
as the only acceptable probe materials for delivering test atmospheres 
in the determination of reference or equivalent methods. Therefore, 
borosilicate glass, FEP Teflon, or their equivalent must be used for 
existing and new NAMS or SLAMS.
---------------------------------------------------------------------------

    \20-29\ See References at end of this appendix.
---------------------------------------------------------------------------

    For VOC monitoring at those SLAMS designated as 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 its equivalent are the acceptable probe materials for VOC and 
carbonyl sampling. Care must be taken to ensure that the sample 
residence time is 20 seconds or less.
    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 also critical. Ozone in the 
presence of NO will show significant losses even in the most inert probe 
material when the residence time exceeds 20 seconds. \26\ Other studies 
\27-28\ indicate that a 10-second or less residence time is easily 
achievable. Therefore, sampling probes for reactive gas monitors at 
SLAMS or NAMS must have a sample residence time less than 20 seconds.

    10. Photochemical Assessment Monitoring Stations (PAMS)

    10.1 Horizontal and Vertical Placement. The probe or at least 80 
percent of the monitoring path must be located 3 to 15 meters above 
ground level. This range provides a practical compromise for finding 
suitable sites for the multipollutant PAMS. The probe or at least 90 
percent of the monitoring path must be at least 1 meter vertically or 
horizontally away from any supporting structure, walls, parapets, 
penthouses, etc., and away from dusty or dirty areas.
    10.2 Spacing From Obstructions. The probe or at least 90 percent of 
the monitoring path must be located away from obstacles and buildings 
such that the distance between the obstacles and the probe or the 
monitoring path is at least twice the height that the obstacle protrudes 
above the probe or monitoring path. There must be unrestricted airflow 
in an arc of at least 270[deg] around the probe inlet. Additionally, the 
predominant wind direction for the period of greatest pollutant 
concentration (as described for each site in section 4.2 of appendix D) 
must be included in the 270[deg] arc. If the probe is located on the 
side of the building, 180[deg] clearance is required. 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 affect the ability of the open path analyzer to continuously 
measure pollutant concentrations.
    Special consideration must be devoted to the use of open path 
analyzers due to their inherent potential sensitivity to certain types 
of interferences, or optical obstructions. While some of these potential 
interferences are comparable to those to which point monitors are 
subject, there are additional sources of potential interferences which 
are altogether different in character. Transient, but significant 
obscuration of especially longer measurement paths could be expected to 
occur as a result of certain prevailing meteorological conditions (e.g., 
heavy fog, rain, snow) and/or aerosol levels that are of a sufficient 
density to prevent the open path analyzer's light transmission. If 
certain compensating measures are not otherwise implemented at the onset 
of monitoring (e.g., shorter path lengths, higher light source 
intensity), data recovery during periods of greatest primary pollutant 
potential could be compromised. For instance, if heavy fog or high 
particulate levels are coincident with periods of projected NAAQS-
threatening pollutant potential, the representativeness of the resulting 
data record

[[Page 282]]

in reflecting maximum pollutant concentrations may be substantially 
impaired despite the fact that the site may otherwise exhibit an 
acceptable, even exceedingly high overall valid data capture rate.
    In seeking EPA approval for inclusion of a site using an open path 
analyzer into the formal SLAMS/NAMS or PSD network, monitoring agencies 
must submit an analysis which evaluates both obscuration potential for a 
proposed path length for the subject area and the effect this potential 
is projected to have on the representativeness of the data record. This 
analysis should include one or more of the following elements, as 
appropriate for the specific circumstance: climatological information, 
historical pollutant and aerosol information, modeling analysis results, 
and any related special study results.
    10.3 Spacing From Roadways. It is important in the probe and 
monitoring path siting process to minimize destructive interferences 
from sources of NO since NO readily reacts with O<INF>3</INF>. Table 4 
below provides the required minimum separation distances between 
roadways and PAMS (excluding upper air measuring stations):

         Table 4--Separation Distance Between Pams and Roadways
                     [Edge of Nearest Traffic Lane]
------------------------------------------------------------------------
                                                               Minimum
                                                              separation
                                                               distance
                                                               between
      Roadway average daily traffic, vehicles per day          roadways
                                                                 and
                                                             stations in
                                                              meters \1\
------------------------------------------------------------------------
<10,000....................................................  <ls-thn-eq>
                                                                      10
15,000.....................................................           20
20,000.....................................................           30
40,000.....................................................           50
70,000.....................................................          100
<ls-thn-eq>110,000.........................................          250
------------------------------------------------------------------------
\1\ Distance from the edge of the nearest traffic lane. The distance for
  intermediate traffic counts should be interpolated from the table
  based on the actual traffic flow.

    10.4 Spacing From Trees. Trees can provide surfaces for adsorption 
and/or reactions to occur and can obstruct normal wind flow patterns. To 
minimize these effects at PAMS, the probe or at least 90 percent of the 
monitoring path should be placed at least 20 meters from the drip line 
of trees. Since the scavenging effect of trees is greater for 
O<INF>3</INF> than for the other criteria pollutants, strong 
consideration of this effect must be given in locating the PAMS probe or 
monitoring path to avoid this problem. Therefore, the probe or at least 
90 percent of the monitoring path must be at least 10 meters from the 
drip line of trees.

11. Waiver Provisions

    It is believed that most sampling probes or monitors can be located 
so that they meet the requirements of this appendix. New stations with 
rare exceptions, can be located within the limits of this appendix. 
However, some existing stations may not meet these requirements and yet 
still produce useful data for some purposes. EPA will consider a written 
request from the State Agency to waive one or more siting criteria for 
some monitoring stations providing that the State can adequately 
demonstrate the need (purpose) for monitoring or establishing a 
monitoring station at that location. For establishing a new station. a 
waiver may be granted only if both of the following criteria are met:
    The site can be demonstrated to be as representative of the 
monitoring area as it would be if the siting criteria were being met.
    The monitor or probe cannot reasonably be located so as to meet the 
siting criteria because of physical constraints (e.g., inability to 
locate the required type of station the necessary distance from roadways 
or obstructions).
    However, for an existing station, a waiver may be granted if either 
of the above criteria are met.
    Cost benefits, historical trends, and other factors may be used to 
add support to the above, however, they in themselves, will not be 
acceptable reasons for granting a waiver. Written requests for waivers 
must be submitted to the Regional Administrator. For those SLAMS also 
designated as NAMS, the request will be forwarded to the Administrator. 
For those SLAMS also designated as NAMS or PAMS, the request will be 
forwarded to the Administrator.

12. Summary

    Table 5 presents a summary of the general requirements for probe and 
monitoring path siting criteria with respect to distances and heights. 
It is apparent from table 5 that different elevation distances above the 
ground are shown for the various pollutants. The discussion in the text 
for each of the pollutants described reasons for elevating the monitor, 
probe, or monitoring path. The differences in the specified range of 
heights are based on the vertical concentration gradients. For CO, the 
gradients in the vertical direction are very large for the microscale, 
so a small range of heights has been used. The upper limit of 15 meters 
was specified for consistency between pollutants and to allow the use of 
a single manifold or monitoring path for monitoring more than one 
pollutant.

[[Page 283]]

                                              Table 5--Summary of Probe and Monitoring Path Siting Criteria
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                         Horizontal and
                                                              Height from ground to    vertical distance     Distance from trees       Distance from
                                         Scale [maximum          probe or 80% of        from supporting       to probe or 90% of    roadways to probe or
             Pollutant                   monitoring path        monitoring path A    structures B to probe    monitoring path A      monitoring path A
                                         length, meters]            (meters)          or 90% of monitoring         (meters)               (meters)
                                                                                        path A  (meters)
--------------------------------------------------------------------------------------------------------------------------------------------------------
SO2 C,D,E,F........................  Middle [300m]           3-15..................  <ls-thn-eq>1.........  <ls-thn-eq>10........  N/A.
                                      Neighborhood, Urban,
                                      and Regional [1km].
CO D,E,G...........................  Micro Middle [300m]     3<plus-minus<ls-thn-    <ls-thn-eq>1.........  <ls-thn-eq>10........  2-10; See table 2 for
                                      Neighborhood [1km].     eq>0.5; 3-15.                                                         middle and
                                                                                                                                    neighborhood scales.
O3 C,D,E...........................  Middle [300m]           3-15..................  <ls-thn-eq>1.........  <ls-thn-eq>10........  See table 1 for all
                                      Neighborhood, Urban,                                                                          scales.
                                      and Regional [1km].
Ozone precursors (for PAMS) C,D,E..  Neighborhood and Urban  3-15..................  <ls-thn-eq>1.........  <ls-thn-eq>10........  See table 4 for all
                                     [1 km]................                                                                         scales.
NO2 C,D,E..........................  Middle [300m]           3-15..................  <ls-thn-eq>1.........  <ls-thn-eq>10........  See table 1 for all
                                      Neighborhood and                                                                              scales.
                                      Urban [1km].
Pb C,D,E,F,H.......................  Micro; Middle,          2-7 (Micro); 2-15 (All  <ls-thn-eq>2 (All      <ls-thn-eq>10 (All     5-15 (Micro); See
                                      Neighborhood, Urban     other scales).          scales, horizontal     scales).               table 3 for all
                                      and Regional.                                   distance only).                               other scales.
PM-10 C,D,E,F,H....................  Micro; Middle,          2-7 (Micro); 2-15 (All  <ls-thn-eq>2 (All      <ls-thn-eq>10 (All     2-10 (Micro); See
                                      Neighborhood, Urban     other scales).          scales, horizontal     scales).               Figure 2 for all
                                      and Regional.                                   distance only).                               other scales.
--------------------------------------------------------------------------------------------------------------------------------------------------------
N/A--Not applicable.
A Monitoring path for open path analyzers is applicable only to middle or neighborhood scale CO monitoring and all applicable scales for monitoring SO2,
  O3, O3 precursors, and NO2.
B When probe is located on a rooftop, this separation distance is in reference to walls, parapets, or penthouses located on roof.
C Should be >20 meters from the dripline of tree(s) and must be 10 meters from the dripline when the tree(s) act as an obstruction.
D Distance from sampler, probe, or 90% of monitoring path to obstacle, such as a building, must be at least twice the height the obstacle protrudes
  above the sampler, probe, or monitoring path. Sites not meeting this criterion may be classified as middle scale (see text).
E Must have unrestricted airflow 270[deg] around the probe or sampler; 180[deg] if the probe is on the side of a building.
F The probe, sampler, or monitoring path should be away from minor sources, such as furnace or incineration flues. The separation distance is dependent
  on the height of the minor source's emission point (such as a flue), the type of fuel or waste burned, and the quality of the fuel (sulfur, ash, or
  lead content). This criterion is designed to avoid undue influences from minor sources.
G For microscale CO monitoring sites, the probe must be >10 meters from a street intersection and preferably at a midblock location.
H For collocated Pb and PM-10 samplers, a 2-4 meter separation distance between collocated samplers must be met.

13. 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.

[[Page 284]]

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. National Assessment of the Urban Particulate 
Problem: Volume 1, National Assessment. GCA Technology Division, 
Bedford, MA. U.S. Environmental Protection Agency, Research Triangle 
Park, NC. EPA Publication No. EPA-450/3-75-024. June 1976.
    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<INF>2</INF> Monitoring. The Center for the Environment and Man, Inc., 
Hartford, CT. Prepared for U.S. Environmental Protection Agency, 
Research Triangle Park, NC. EPA Publication No. EPA-450/3-77-013. April 
1977.
    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 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. Epidemiologic Study of the Effects of 
Automobile Traffic on Blood Lead Levels, Southwest Research Institute, 
Houston, TX. Prepared for U.S. Environmental Protection Agency, Research 
Triangle Park, NC. EPA-600/1-78-055, August 1978.
    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. CFR Title 40 part 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

[[Page 285]]

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 1987.

[44 FR 27571, May 10, 1979; 44 FR 72592, Dec. 14, 1979, as amended at 46 
FR 44170, Sept. 3, 1981; 51 FR 9598, Mar. 19, 1986; 52 FR 24744--24748, 
July 1, 1987; 52 FR 27286, July 20, 1987; 58 FR 8474, 8475, Feb. 12, 
1993; 60 FR 52324, Oct. 6, 1995; 62 FR 38854, July 18, 1997; 64 FR 3036, 
Jan. 20, 1999]

       Appendix F to Part 58--Annual SLAMS Air Quality Information

    1. General
    2. Required Information
    2.1 Sulfur Dioxide (SO<INF>2</INF>)
    2.1.1 Site and Monitoring Information
    2.1.2 Annual Summary Statistics
    2.2 Total Suspended Particulates (TSP)
    2.2.1 Site and Monitoring Information
    2.2.2 Annual Summary Statistics
    2.2.3 Episode and Other Unscheduled Sampling Data
    2.3 Carbon Monoxide (CO)
    2.3.1 Site and Monitoring Information
    2.3.2 Annual Summary Statistics
    2.4 Nitrogen Dioxide (NO<INF>2</INF>)
    2.4.1 Site and Monitoring Information
    2.4.2 Annual Summary Statistics
    2.5 Ozone(O<INF>3</INF>)
    2.5.1 Site and Monitoring Information
    2.5.2 Annual Summary Statistics
    2.6 Lead (Pb)
    2.6.1 Site and Monitoring Information
    2.6.2 Annual Summary Statistics
    2.7 Particulate Matter (PM<INF>10</INF>)
    2.7.1 Site and Monitoring Information
    2.7.2 Annual Summary Statistics
    2.7.3 Annual Summary Statistics
    2.7.4 Episode and Other Unscheduled Sampling Data

1. General

    This appendix describes information to be compiled and submitted 
annually to EPA for each ambient monitoring station in the SLAMS Network 
in accordance with Sec. 58.26. The annual summary statistics that are 
described in section 2 below shall be construed as only the minimum 
necessary statistics needed by EPA to overview national air quality 
status. They will be used by EPA to convey information to a variety of 
interested parties including environmental groups, Federal agencies, the 
Congress, and private citizens upon request. As the need arises, EPA may 
issue modifications to these minimum requirements to reflect changes in 
EPA policy concerning the National Ambient Air Quality Standards 
(NAAQS).
    As indicated in Sec. 58.26(c), the contents of the SLAMS annual 
report shall be certified by the senior air pollution control officer in 
the State to be accurate to the best of his knowledge. In addition, the 
manner in which the data were collected must be certified to have 
conformed to the applicable quality assurance, air monitoring 
methodology, and probe siting criteria given in appendices A, C, and E 
to this part. A certified statement to this effect must be included with 
the annual report. As required by Sec. 58.26(a), the report must be 
submitted by July 1 of each year for data collected during the period 
January 1 to December 31 of the previous year.
    EPA recognizes that most air pollution control agencies routinely 
publish air quality statistical summaries and interpretive reports. EPA 
encourages State and local agencies to continue publication of such 
reports and recommends that they be expanded, where appropriate, to 
include analysis of air quality trends, population exposure, and 
pollutant distributions. At their discretion, State and local agencies 
may wish to integrate the SLAMS report into routine agency publications.

2. Required Information

    This paragraph describes air quality monitoring information and 
summary statistics which must be included in the SLAMS annual report. 
The required information is itemized below by pollutant. Throughout this 
appendix, the time of occurrence refers to the ending hour. For example, 
the ending hour of an 8-hour CO average from 12:01 a.m. to 8:00 a.m. 
would be 8:00 a.m.
    For the purposes of range assignments the following rounding 
convention will be used. The air quality concentration should be rounded 
to the number of significant digits used in specifying the concentration 
intervals. The digit to the right of the last significant digit 
determines the rounding process. If this digit is greater than or equal 
to 5, the last significant digit is rounded up. The insignificant digits 
are truncated. For example, 100.5 ug/m<SUP>3</SUP> rounds to 101 ug/
m<SUP>3</SUP> and 0.1245 ppm rounds to 0.12 ppm.
    2.1 Sulfur Dioxide (SO<INF>2</INF>)
    2.1.1 Site and Monitoring Information. City name (when applicable), 
county name and street address of site location. AIRS-AQS site code. 
AIRS-AQS monitoring method code. Number of hourly observations. (1) 
Number of daily observations. (2)
    2.1.2 Annual Summary Statistics. Annual arithmetic mean (ppm). 
Highest and second highest 24-hour averages (3) (ppm) and dates of 
occurrence. Highest and second highest 3-hour averages (1, 3) (ppm) and 
dates and times (1) (ending hour) of occurrence. Number of exceedances 
of the 24-hour primary

[[Page 286]]

NAAQS. (3) Number of exceedances of the 3-hour secondary NAAQS. (3) 
Number of 24-hour average concentrations (4) in ranges:

------------------------------------------------------------------------
                       Range                           Number of values
------------------------------------------------------------------------
0.00 to 0.04 (ppm).................................  ...................
0.05 to 0.08.......................................  ...................
0.09 to 0.12.......................................  ...................
0.13 to 0.16.......................................  ...................
0.17 to 0.20.......................................  ...................
0.21 to 0.24.......................................  ...................
0.25 to 0.28.......................................  ...................
Greater than .28...................................  ...................
------------------------------------------------------------------------

    2.2 Total Suspended Particulates (TSP)
    2.2.1 Site and Monitoring Information. City name (when applicable), 
county name and street address of site location. AIRS-AQS site code. 
Number of daily observations.
    2.2.2 Annual Summary Statistics. Annual arithmetic mean ([mu]g/m 
\3\) as specified in appendix K of part 50. Daily TSP values exceeding 
the level of the 24-hour PM<INF>10</INF> NAAQS and dates of occurrence. 
If more than 10 occurrences, list only the 10 highest daily values. 
Sampling schedule used such as once every six days, once every three 
days, etc. Number of additional sampling days beyond sampling schedule 
used. Number of 24-hour average concentrations in ranges:

------------------------------------------------------------------------
                       Range                           Number of values
------------------------------------------------------------------------
  0 to 50 ([mu]g/m \3\)............................  ...................
  51 to 100........................................  ...................
  101 to 150.......................................  ...................
  151 to 200.......................................  ...................
  201 to 250.......................................  ...................
  251 to 300.......................................  ...................
  301 to 400.......................................  ...................
  Greater than 400.................................  ...................
------------------------------------------------------------------------

    2.2.3 Episode and Other Unscheduled Sampling Data. List episode 
measurements, other unscheduled sampling data, and dates of occurrence. 
List the regularly scheduled sample measurements and date of occurrence 
that preceded the episode or unscheduled measurement.
    2.3 Carbon Monoxide (CO)
    2.3.1 Site and Monitoring Information. City name (when applicable), 
county name and street address of site location. AIRS-AQS site code. 
AIRS-AQS monitoring method code. Number of hourly observations.
    2.3.2 Annual Summary Statistics. Highest and second highest 1-hour 
values (ppm) and date and time of occurrence. Highest and second highest 
8-hour averages (3) (ppm) and date and time of occurrence (ending hour). 
Number of exceedances of the 1-hour primary NAAQS. Number of exceedances 
of the 8-hour average primary NAAQS. (3) Number of 8-hour average 
concentrations (4) in ranges:

------------------------------------------------------------------------
                       Range                           Number of values
------------------------------------------------------------------------
0 to 4 (ppm).......................................  ...................
5 to 8 (ppm).......................................  ...................
9 to 12............................................  ...................
13 to 16...........................................  ...................
17 to 20...........................................  ...................
21 to 24...........................................  ...................
25 to 28...........................................  ...................
Greater than 28....................................  ...................
------------------------------------------------------------------------

    2.4 Nitrogen Dioxide (NO<INF>2</INF>)
    2.4.1 Site and Monitoring Information. City name (when applicable), 
county name, and street address of site location. AIRS-AQS site code. 
AIRS-AQS monitoring method code. Number of hourly observations. (1) 
Number of daily observations. (2)
    2.4.2 Annual Summary Statistics. Annual arithmetic mean (ppm). 
Highest and second highest hourly averages (3) (ppm) and their dates and 
time of occurrence. Highest and second highest 24-hour averages (2) and 
their date of occurrence (ppm). Number of hourly average concentrations 
in ranges. (1)

------------------------------------------------------------------------
                       Range                           Number of values
------------------------------------------------------------------------
.0 to .04 (ppm)....................................  ...................
.05 to .08.........................................  ...................
.09 to .12.........................................  ...................
.13 to .16.........................................  ...................
.17 to .20.........................................  ...................
.21 to .24.........................................  ...................
.25 to .28.........................................  ...................
Greater than 0.28..................................  ...................
------------------------------------------------------------------------

    2.5 Ozone (O<INF>3</INF>)
    2.5.1 Site and Monitoring Information. City name (when applicable), 
county name and street address of site location. AIRS-AQS site code. 
AIRS-AQS monitoring method code. Number of hourly observations.
    2.5.2 Annual Summary Statistics. Four highest daily maximum hour 
values (ppm) and their dates and time of occurrence. Number of 
exceedances of the daily maximum 1-hour primary NAAQS. Number of daily 
maximum hour concentrations in ranges:

------------------------------------------------------------------------
                       Range                           Number of values
------------------------------------------------------------------------
0 to .04 (ppm).....................................  ...................
.05 to .08.........................................  ...................
.09 to .12.........................................  ...................
.13 to .16.........................................  ...................
.17 to .20.........................................  ...................
.21 to .24.........................................  ...................
.25 to .28.........................................  ...................
Greater than .28...................................  ...................
------------------------------------------------------------------------

    2.6 Lead (Pb).
    2.6.1 Site and Monitoring Information. City name (when applicable), 
county name, and street address of site location, AIRS-AQS site code. 
AIRS-AQS monitoring method code. Sampling interval of submitted data, 
e.g., twenty-four hour or quarterly composites.
    2.6.2 Annual Summary Statistics. The four quarterly arithmetic 
averages given to two decimal places for the year together with the

[[Page 287]]

number of twenty-four hour samples included in the average, as in the 
following format:

------------------------------------------------------------------------
                                                               Quarterly
                                                              arithmetic
               Quarter                   Number of 24-hour      average
                                              samples          ([mu]g/m
                                                                 \3\)
------------------------------------------------------------------------
Jan.-March..........................  ......................  ..........
April-June..........................  ......................  ..........
July-Sept...........................  ......................  ..........
Oct.-Dec............................  ......................  ..........
------------------------------------------------------------------------

    2.7 Particulate Matter (PM<INF>10</INF>)
    2.7.1 Site and Monitoring Information. City name (when applicable), 
county name, and street address of site location. AIRS-AQS site code. 
Number of daily observations.
    2.7.2 Annual Summary Statistics. Annual arithmetic mean ([mu]g/m 
\3\) as specified in appendix K of part 50. All daily PM<INF>10</INF> 
values above the level of the 24-hour PM<INF>10</INF> NAAQS and dates of 
occurrence. Sampling schedule used such as once every six days, once 
every three days, etc. Number of additional sampling days beyond 
sampling schedule used. Number of 24-hour average concentrations in 
ranges:

------------------------------------------------------------------------
                       Range                           Number of values
------------------------------------------------------------------------
0 to 25 ([mu]g/m \3\)..............................  ...................
26 to 50...........................................  ...................
51 to 75...........................................  ...................
76 to 100..........................................  ...................
101 to 125.........................................  ...................
126 to 150.........................................  ...................
151 to 175.........................................  ...................
176 to 200.........................................  ...................
Greater than 200...................................  ...................
------------------------------------------------------------------------

    2.7.3 Annual Summary Statistics. Annual arithmetic mean ([mu]g/
m<SUP>3</SUP>) as specified in 40 CFR part 50, appendix N. All daily PM-
fine values above the level of the 24-hour PM-fine NAAQS and dates of 
occurrence. Sampling schedule used such as once every 6 days, everyday, 
etc. Number of 24-hour average concentrations in ranges:

------------------------------------------------------------------------
                       Range                           Number of Values
------------------------------------------------------------------------
0 to 15 ([mu]g/m3).................................  ...................
16 to 30...........................................  ...................
31 to 50...........................................  ...................
51 to 70...........................................  ...................
71 to 90...........................................  ...................
91 to 110..........................................  ...................
Greater than 110...................................  ...................
------------------------------------------------------------------------

    2.7.4 Episode and Other Unscheduled Sampling Data. List episode 
measurements, other unscheduled sampling data, and dates of occurrence. 
List the regularly scheduled sample measurements and date of occurrence 
that preceded the episode or unscheduled measurement.

    Footnotes

    1. Continuous methods only.
    2. Manual or intermittent methods only.
    3. Based on nonoverlapping values computed according to procedures 
described in reference (1) or on individual intermittent measurements.
    4. Based on overlapping running averages for continuous measurements 
as described in reference (1) or on individual measurement for 
intermittent methods.

Reference

    1. ``Guidelines for the Interpretation of Air Quality Standards'' 
U.S. Environmental Protection Agency, Office of Air Quality Planning and 
Standards, Research Triangle Park, NC 27711. OAQPS No. 1.2-008, 
February, 1977.

[44 FR 27571, May 10, 1979, as amended at 46 FR 44171, Sept. 3, 1981; 51 
FR 9600, Mar. 19, 1986; 52 FR 24748, 24749, July 1, 1987; 59 FR 41628, 
Aug. 12, 1994; 62 FR 38854, July 18, 1997]

    Appendix G to Part 58--Uniform Air Quality Index (AQI) and Daily 
                                Reporting

                          General Requirements

    1. What is the AQI?
    2. Why report the AQI?
    3. Must I report the AQI?
    4. What goes into my AQI report?
    5. Is my AQI report for my MSA only?
    6. How do I get my AQI report to the public?
    7. How often must I report the AQI?
    8. May I make exceptions to these reporting requirements?

                               Calculation

    9. How does the AQI relate to air pollution levels?
    10. Where do I get the pollutant concentrations to calculate the 
AQI?
    11. Do I have to forecast the AQI?
    12. How do I calculate the AQI?

                   Background and Reference Materials

    13. What additional information should I know?

                          General Requirements

                           1. What Is the AQI?

    The AQI is a tool that simplifies reporting air quality to the 
general public. The AQI incorporates into a single index concentrations 
of 5 criteria pollutants: ozone (O<INF>3</INF>), particulate matter 
(PM), carbon monoxide (CO), sulfur dioxide (SO<INF>2</INF>), and 
nitrogen dioxide (NO<INF>2</INF>). The scale of the index is divided 
into general categories that are associated with health messages.

                         2. Why Report the AQI?

    The AQI offers various advantages:
    a. It is simple to create and understand.
    b. It conveys the health implications of air quality.

[[Page 288]]

    c. It promotes uniform use throughout the country.

                        3. Must I Report the AQI?

    You must report the AQI daily if yours is a metropolitan statistical 
area (MSA) with a population over 350,000.

                    4. What Goes Into My AQI Report?

    i. Your AQI report must contain the following:
    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 critical 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 you choose to report in a color format, the associated color. 
Use only the following descriptors and colors for the six AQI 
categories:

                         Table 1--AQI Categories
------------------------------------------------------------------------
                                                          And this color
           For this AQI             Use this descriptor         1
------------------------------------------------------------------------
0 to 50..........................  ``Good''............  Green.
----------------------------------
51 to 100........................  ``Moderate''........  Yellow.
----------------------------------
101 to 150.......................  ``Unhealthy for       Orange.
                                    Sensitive Groups''.
----------------------------------
151 to 200.......................  ``Unhealthy''.......  Red.
----------------------------------
201 to 300.......................  ``Very Unhealthy''..  Purple.
----------------------------------
301 and above....................  ``Hazardous''.......  Maroon.\1\
------------------------------------------------------------------------
1 Specific colors can be found in the most recent reporting guidance
  (Guideline for Public Reporting of Daily Air Quality--Air Quality
  Index (AQI)).

    f. The pollutant specific sensitive groups for any reported index 
value greater than 100. Use the following sensitive groups for each 
pollutant:

------------------------------------------------------------------------
 When this pollutant has an index value    Report these sensitive groups
             above 100 * * *                           * * *
------------------------------------------------------------------------
Ozone...................................  Children and people with
                                           asthma are the groups most at
                                           risk.
-----------------------------------------
PM2.5...................................  People with respiratory or
                                           heart disease, the elderly
                                           and children are the groups
                                           most at risk.
-----------------------------------------
PM10....................................  People with respiratory
                                           disease are the group most at
                                           risk.
-----------------------------------------
CO......................................  People with heart disease are
                                           the group most at risk.
-----------------------------------------
SO2.....................................  People with asthma are the
                                           group most at risk.
-----------------------------------------
NO2.....................................  Children and people with
                                           respiratory disease are the
                                           groups most at risk.
------------------------------------------------------------------------

    ii. When appropriate, your AQI report may also contain the 
following:
    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 unusual AQI values.
    e. Actual pollutant concentrations.

                  5. Is My AQI Report for My MSA Only?

    Generally, your AQI report applies to your MSA only. However, if a 
significant air quality problem exists (AQI greater than 100) in areas 
significantly impacted by your MSA but not in it (for example, 
O<INF>3</INF> concentrations are often highest downwind and outside an 
urban area), you should identify these areas and report the AQI for 
these areas as well.

              6. How Do I Get My AQI Report to the Public?

    You must furnish the daily report to the appropriate news media 
(radio, television, and newspapers). You must make the daily report 
publicly available at one or more places of public access, or by any 
other means, including a recorded phone message, a public Internet site, 
or facsimile transmission. When the AQI value is greater than 100, it is 
particularly critical that the reporting to the various news media be as 
extensive as possible. At a minimum, it should include notification to 
the media with the largest market coverages for the area in question.

                   7. How Often Must I Report the AQI?

    You must report the AQI at least 5 days per week. Exceptions to this 
requirement are in section 8 of this appendix.

        8. May I Make Exceptions to These Reporting Requirements?

    i. If the index value for a particular pollutant remains below 50 
for a season or year, then you may exclude the pollutant from your 
calculation of the AQI in section 12.
    ii. If all index values remain below 50 for a year, then you may 
report the AQI at your discretion. In subsequent years, if pollutant 
levels rise to where the AQI would be above 50, then the AQI must be 
reported as required in sections 3, 4, 6, and 7 of this appendix.

[[Page 289]]

                               Calculation

           9. How Does the AQI Relate to Air Pollution Levels?

    For each pollutant, the AQI transforms ambient concentrations to a 
scale from 0 to 500. The AQI is keyed as appropriate to the national 
ambient air quality standards (NAAQS) for each pollutant. In most cases, 
the index value of 100 is associated with the numerical level of the 
short-term standard (i.e., averaging time of 24-hours or less) for each 
pollutant. Different approaches are taken for NO<INF>2</INF>, for which 
no short-term standard has been established, and for PM<INF>2.5</INF>, 
for which the annual standard is the principal vehicle for protecting 
against short-term concentrations. The index value of 50 is associated 
with the numerical level of the annual standard for a pollutant, if 
there is one, at one-half the level of the short-term standard for the 
pollutant, or at the level at which it is appropriate to begin to 
provide guidance on cautionary language. Higher categories of the index 
are based on increasingly serious health effects and increasing 
proportions of the population that are likely to be affected. The index 
is related to other air pollution concentrations through linear 
interpolation based on these levels. The AQI is equal to the highest of 
the numbers corresponding to each pollutant. For the purposes of 
reporting the AQI, the sub-indexes for PM<INF>10</INF> and 
PM<INF>2.5</INF> are to be considered separately. The pollutant 
responsible for the highest index value (the reported AQI) is called the 
``critical'' pollutant.

  10. Where Do I Get the Pollutant Concentrations To Calculate the AQI?

    You must use concentration data from population-oriented State/Local 
Air Monitoring Station (SLAMS) or parts of the SLAMS required under 40 
CFR 58.20 for each pollutant except PM. For PM, you need only calculate 
and report the AQI on days for which you have measured air quality data 
(e.g., particulate monitors often report values only every sixth day). 
You may use particulate measurements from monitors that are not 
reference or equivalent methods (for example, continuous PM<INF>10</INF> 
or PM<INF>2.5</INF> monitors) if you can relate these measurements by 
statistical linear regression to reference or equivalent method 
measurements.

                   11. Do I Have to Forecast the AQI?

    You should forecast the AQI to provide timely air quality 
information to the public, but this is not required. If you choose to 
forecast the AQI, then you may consider both long-term and short-term 
forecasts. You can forecast the AQI at least 24-hours in advance using 
the most accurate and reasonable procedures considering meteorology, 
topography, availability of data, and forecasting expertise. The 
document ``Guideline for Developing an Ozone Forecasting Program'' (the 
Forecasting Guidance) will help you start a forecasting program. You can 
also issue short-term forecasts by predicting 8-hour ozone values from 
1-hour ozone values using methods suggested in the Reporting Guidance, 
``Guideline for Public Reporting of Daily Air Quality.''

                     12. How Do I Calculate the AQI?

    i. The AQI is the highest value calculated for each pollutant as 
follows:
    a. Identify the highest concentration among all of the monitors 
within each reporting area and truncate the pollutant concentration to 
one more than the significant digits used to express the level of the 
NAAQS for that pollutant. This is equivalent to the rounding conventions 
used in the NAAQS.
    b. Using Table 2, find the two breakpoints that contain the 
concentration.
    c. Using Equation 1, calculate the index.
    d. Round the index to the nearest integer.

[[Page 290]]

                                                            Table 2--Breakpoints for the AQI
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                             These breakpoints                                               Equal these AQIs * *
-----------------------------------------------------------------------------------------------------------           *
                                                                       PM10                                -----------------------        Category
         O3 (ppm)  8-hour           O3 (ppm)  1-  PM2.5  ([mu]g/m3   ([mu]g/m3    CO (ppm)     SO2 (ppm)
                                       hour 1             )              )                                   NO2 (ppm)      AQI
--------------------------------------------------------------------------------------------------------------------------------------------------------
0.000-0.064.......................  ............   0.0-15.4           0-54      0.0-4.4      0.000-0.034     ( 2 )       0-50      Good.
0.065-0.084.......................  ............  15.5-40.4         55-154      4.5-9.4      0.035-0.144     ( 2 )       51-100    Moderate.
0.085-0.104.......................  0.125-0.164   40.5-65.4         155-254     9.5-12.4     0.145-0.224     ( 2 )       101-150   Unhealthy for
                                                                                                                                    sensitive groups.
0.105-0.124.......................  0.165-0.204   \4\ 65.5-150.4    255-354     12.5-15.4    0.225-0.304     ( 2 )       151-200   Unhealthy.
0.125-0.374.......................  0.205-0.404   \4\ 150.5-250.4   355-424     15.5-30.4    0.305-0.604    0.65-1.24    201-300   Very unhealthy.
( 3 ).............................  0.405-0.504   \4\ 250.5-350.4   425-504     30.5-40.4    0.605-0.804    1.25-1.64    301-400   .....................
( 3 ).............................  0.505-0.604   \4\ 350.5-500.4   505-604     40.5-50.4    0.805-1.004    1.65-2.04    401-500   Hazardous.
--------------------------------------------------------------------------------------------------------------------------------------------------------
1 Areas are generally required to report the AQI based on 8-hour ozone values. However, there are a small number of areas where an AQI based on 1-hour
  ozone values would be more precautionary. In these cases, in addition to calculating the 8-hour ozone index value, the 1-hour ozone index value may be
  calculated, and the maximum of the two values reported.
2 NO2 has no short-term NAAQS and can generate an AQI only above an AQI value of 200.
3 8-hour O3 values do not define higher AQI values (>= 301). AQI values of 301 or higher are calculated with 1-hour O3 concentrations.
4 If a different SHL for PM2.5 is promulgated, these numbers will change accordingly.

[[Page 291]]

    ii. If the concentration is equal to a breakpoint, then the index is 
equal to the corresponding index value in Table 2. However, Equation 1 
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. You must also note that in some areas, the AQI based on 1-
hour O<INF>3</INF> will be more precautionary than using 8-hour values 
(see footnote 1 to Table 2). In these cases, you may use 1-hour values 
as well as 8-hour values to calculate index values and then use the 
maximum index value as the AQI for O<INF>3</INF>.
[GRAPHIC] [TIFF OMITTED] TR04AU99.044

Where:

I<INF>p</INF> = the index value for pollutant<INF>p</INF>
C<INF>p</INF> = the truncated concentration of pollutant<INF>p</INF>
BP<INF>Hi</INF> = the breakpoint that is greater than or equal to 
C<INF>p</INF>
BP<INF>Lo</INF> = the breakpoint that is less than or equal to 
C<INF>p</INF>
I<INF>Hi</INF> = the AQI value corresponding to BP<INF>Hi</INF>
I<INF>lo</INF> = the AQI value corresponding to BP<INF>Lo</INF>.

    iii. If the concentration is larger than the highest breakpoint in 
Table 2 then you may use the last two breakpoints in Table 2 when you 
apply Equation 1.

                                 Example

    iv. Using Table 2 and Equation 1, 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 you observe a PM<INF>10</INF> 
value of 210 [mu]g/m<SUP>3</SUP>, a 1-hour O<INF>3</INF> value of 0.156 
ppm, and an 8-hour O<INF>3</INF> value of 0.130 ppm, then do this:
    a. Find the breakpoints for PM<INF>10</INF> at 210 [mu]g/
m<SUP>3</SUP> as 155 [mu]g/m<SUP>3</SUP> and 254 [mu]g/m<SUP>3</SUP>, 
corresponding to index values 101 and 150;
    b. Find the breakpoints for 1-hour O<INF>3</INF> at 0.156 ppm as 
0.125 ppm and 0.164 ppm, corresponding to index values 101 and 150;
    c. Find the breakpoints for 8-hour O<INF>3</INF> at 0.130 ppm as 
0.125 ppm and 0.374 ppm, corresponding to index values 201 and 300;
    d. Apply Equation 1 for 210 [mu]g/m<SUP>3</SUP>, PM<INF>10</INF>:
    [GRAPHIC] [TIFF OMITTED] TR04AU99.045
    
    e. Apply Equation 1 for 0.156 ppm, 1-hour O<INF>3</INF>:
    [GRAPHIC] [TIFF OMITTED] TR04AU99.046
    
    f. Apply Equation 1 for 0.130 ppm, 8-hour O<INF>3</INF>:
    [GRAPHIC] [TIFF OMITTED] TR04AU99.047
    
    g. Find the maximum, 203. This is the AQI. The minimal AQI report 
would read:
    v. Today, the AQI for my city is 203 which is very unhealthy, due to 
ozone. Children and people with asthma are the groups most at risk.

                   Background and Reference Materials

             13. What Additional Information Should I Know?

    The EPA has developed a computer program to calculate the AQI for 
you. The program works with Windows 95, it prompts for inputs, and it 
displays all the pertinent information for the AQI (the index value, 
color, category, sensitive group, health effects, and cautionary 
language). The EPA has also prepared a brochure on the AQI that explains 
the index in detail (The Air Quality Index), Reporting Guidance 
(Guideline for Public Reporting of Daily Air Quality) that provides 
associated health effects and cautionary statements, and Forecasting 
Guidance (Guideline for Developing an Ozone Forecasting Program) that 
explains the steps necessary to start an air pollution forecasting 
program. You can download the program and the guidance documents at 
www.epa.gov/airnow.

[64 FR 42547, Aug. 4, 1999]