From: Richard Wayland/RTP/USEPA/US To: dominic_j._mancini@omb.eop.gov Cc: Lydia Wegman/RTP/USEPA/US@EPA Date: 12/12/2012 03:44 PM Subject: Fw: Revised Section VIII of premable
- Amendments to Ambient Monitoring and Reporting

Requirements Dom... may have missed the period after your initial. Hope you get this. Chet

__________________
Dom,
As we di scussed yesterday, this revised section does a few things: 1. We have provided more emphasis on ensuring near
- road environments represent population exposures. 2. We have added a reference citing our modeling results regarding the expected lower near
r oad gradients in the future. 3. We have substantially changed our presumption of micro
- and middle scale sites as applicable to the annual NAAQS. Previously we drafted that near
- road type locations are area wide. In this revised version we say that the re are cases where unique locations exist in the near road environment and that the annual NAAQS should not apply to those cases. States should provide a recommendation on this in their annual plans. 4. We have provided concrete examples of the types of locations that should not be applicable to the annual PM2.5 NAAQS, even if they are at a NO2 near
- road station. The attached file is a redline strikeout compared to the section VIII file that you have from earlier. I think this addresses your concerns from yesterday.***E.O. 12866 Revie w - Draft Do Not Cite, Quote, or Release During Review***; Monitoring Preamble Update 121212

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Page 2 of 62 VIII. Amendments to Ambient Monitoring and Reporting Requirements The EPA is finalizing a number of changes to the ambient air monitoring, reporting, and network design requirements associated with the PM NAAQS
. Ambient PM monitoring data are used to meet a variety of monitoring objectives including determining whether an area is in violation of the PM NAAQS
. Ambient PM monitoring data are collected by state, local, and tribal monitoring agencies (“monitoring agencies”) in accordance with the monitoring requirements contained in 40 CFR parts 50, 53, and 58
. This section discusses the monitoring changes t hat the EPA is finalizing to support the revised PM NAAQS summarized in sections II I .F, I V .F, and V I .F above
. The monitoring changes being finalized primarily relate to the revised primary PM 2.5 NAAQS. Several monitoring changes were proposed specifically in support of a potential secondary PM 2.5 visibility index; however, as explained in Section VI, EPA is not finalizing a secondary NAAQS using a visibility index and therefore is not finalizing the monitoring changes that would have been necessary to suppo rt it
. The EPA did not propose any monitoring changes associated with the PM 10 NAAQS and is not adopting any in this final rule. A. Issues Related to 40 CFR Part 53 (Reference and Equivalent Methods) To be used in a determination of compliance with the PM NAA QS, PM data are typically collected using samplers or monitors employing an FRM or FEM
. The EPA also allows use of alternative methods where explicitly stated in the monitoring methodology requirements (appendix C of 40 CFR part 58), such as PM 2.5 ARMs whi ch can be used to determine compliance with the NAAQS
. The EPA prescribes testing and approval criteria for FRM and FEM methods in 40 CFR part 53. 1. PM 2.5 and PM 10

- 2.5 Federal Equivalent Methods***E.O. 12866 Revie w - Draft Do Not Cite, Quote, or Release During Review***; Monitoring Preamble Update 121212

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Page 3 of 62 As described in the proposal, t he EPA continues to believe that an effective PM 2.5 monitoring strategy includes the use of both filter

- based FRM samplers and well

performing continuous PM 2.5 monitors
. Well

- performing continuous PM 2.5 monitors would include both non

- designated continuous PM 2.5 monitors and designat ed Class III 1 continuous FEMs that meet the performance criteria described in table C

- 4 of 40 CFR part 53 when comparing to a collocated FRM operated by the monitoring agency . Only designated methods (i.e., FRMs, FEMs, and ARMs) are approved to be used in comparison to the NAAQS; however, non

- designated methods may be useful to meet other monitoring objectives (e.g., reporting the AQI). The use of Class III continuous FEMs at SLAMS is described in more detail in section VII I
. B. 3.b.ii below
. Monitoring agenc ies are encouraged to evaluate the quality of data being generated by FEMs and, where appropriate, to reduce the use of manual, filter

- based samplers to improve operational efficiency and to lower overall operating costs
. To encourage such a strategy, the EPA is working with numerous stakeholders including the monitoring committee of NACAA, instrument manufacturers, and monitoring agencies to support national data analyses of continuous PM 2.5 FEM performance, and where such performance does not meet data qu ality objectives, to develop and institute a program of best practices to improve the quality and consistency of resulting data. The EPA believes that progress is being made to implement well performing PM 2.5 continuous FEMs across the nation
. As noted in the proposal , the first few steps involved the EPA developing and approving the testing and performance criteria which

1 Class III refers to those methods for PM 2.5 or PM 10

- 2.5 that are employed to provide PM 2.5 or PM 10

- 2.5 ambient air measurements representative of one

- hour or less integrated PM 2.5 or PM 10

- 2.5 concentrations, as well as 24

- hour measurements determined as, or equivalent to, the mean of 24 one

- hour consecutive measurements.***E.O. 12866 Revie w - Draft Do Not Cite, Quote, or Release During Review***; Monitoring Preamble Update 121212

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Page 4 of 62 were finalized in 2006, followed by instrument companies performing field testing and submitting applications to the EPA, and the EPA rev iew and approval, as appropriate, of Class III FEMs
. In the current step, monitoring agencies are testing and assessing the data comparability from continuous PM 2.5 FEMs
. While EPA did not propos e any changes to the performance or testing criteria in 40 CF R part 53 used to approve PM 2.5 continuous FEMs, the EPA did propose an administrative change to p art 53.9

– “Conditions of designations.” See 77 FR 39006. This section describes a number of conditions that must be met by a manufacturer as a condition of maintaining designation of an FRM or FEM
. Subsection (c) of this section reads , “ Any analyzer, PM 10 sampler, PM 2.5 sampler, or PM 10

- 2.5 sampler offered for sale as part of a FRM or FEM shall function within the limits of the performance specifications referred to in 40 CFR 53.20(a), 53.30(a), 53.50, or 53.60, as applicable, for at least 1 year after delivery and acceptance when maintained and operated in accordance with the manual referred to in 40 CFR 53.4(b)(3).” The EPA’s intent in this requirement is to ensure that monitoring methods work within performance criteria, which includes methods for PM 2.5 and PM 10

- 2.5 ; however, there wa s no s pecific reference to performance criteria for Class II 2 and III PM 2.5 and PM 10

- 2.5 methods
. T he EPA propose d to link the performance criteria referred to in 40 CFR part 53.35 associated with Class II and III PM 2.5 and PM 10

- 2.5 methods with this requirement for maintaining designation of approved FEMs
. The specific performance criteria identified in 40 CFR 53.35 for PM 2.5 and PM 10

- 2.5 methods are available in table C

- 4 to subpart C of 40 CFR part 53
. 2 Class II refers to those methods f or PM 2.5 or PM 10

- 2.5 in which integrated samples are taken by filtration and subjected to a subsequent filter conditioning process followed by a gravimetric mass determination, but which is not a Class I equivalent methods because of substantial deviations from the design specification of the sampler specified for reference methods in appendix L or O (as applicable) of part 50 of the CFR.***E.O. 12866 Revie w - Draft Do Not Cite, Quote, or Release During Review***; Monitoring Preamble Update 121212

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Page 5 of 62 All comments received on this proposed change were support ive and EPA is finalizing this change. The implication of this change is that instrument manufacturers and air agencies operating the equipment will have a shared responsibility for approved FEMs to meet required performance criteria for at least the first 12 months of operation, which is the typical warranty period for an instrument. By having a shared responsibility for an FEM to meet the performance criteria , instrument companies and air agencies will both be motivated to ensure the best practices for installing, operating, and servicing an instrument are carried out according to the instrument company’s operating manual and other readily available materials 3 in support of each method. 2. Use of C hemical S peciation N etwork (CSN) Methods to Support the Proposed New Secondary PM 2.5 Visibility I ndex NAAQS The EPA had proposed to use CSN methods to support the proposed new secondary PM 2.5 visibility index NAAQS; however, as explained in Section VI of this final rule, EPA is not finalizing the new secondary PM 2.5 visibility index NAAQS and therefore has no need to finalize the CSN methods to support such a standard. Despite our decision not to finalize formal requi rements for CSN methods, this network remains a critical component in our PM monitoring program. The EPA, monitoring agencies, and external scientists and policy makers use PM 2.5 data from the CSN to support several important monitoring objectives such as: development of modeling tools and the application of source apportionment modeling for control strategy development to implement the NAAQS; health effects and exposure research studies; assessment of the effectiveness of emission reductions strategies thr ough the
3 At the recent National Air Quality Conference in May of 2012, a training session on “Best Practices for Operating PM 2 .5 Continuous FEMs” was conducted. Presentations from this session are publically available on EPA’s web site at: http://www.epa.gov/ttn/amtic/2012present.html
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Page 6 of 62 characterization of air quality; and development of SIPs . The use of the CSN to support all of these objectives will continue. B. Changes to 40 CFR Part 58 (Ambient Air Quality Surveillance) 1. Terminology Changes The EPA propose d to revise several term s associated with PM 2.5 monitor placement to ensure consistency with other NAAQS and to conform with long

- standing practices in siting of equipment by monitoring agencies ( 77 FR 39007 )
. The EPA propose d to revoke the term “community

- oriented” and replace i t with the term “area

- wide.” The term “community

- oriented,” while used within the description of the design criteria for PM 2.5 , is not defined and has not been used in the design criteria for other NAAQS pollutants
. Appendix D to 40 CFR part 58 presents a functional usage of the term where sites at the neighborhood and urban scale area are considered to be “community

- oriented.” In addition, population

- oriented , micro

- or middle

- scale PM 2.5 monitoring may also be considered “community

- oriented” when determined by the Regional Administrator to represent many such locations throughout a metropolitan area
. The EPA propose d to replace this usage of “community

- oriented” with the term “area

wide” in the text of the PM 2.5 network design criteria and to define it in 40 CFR 58.1 to provide a more consistent usage of this concept throughout appendix D of 40 CFR part 58
. Specifically, t he EPA propose d that the terminology would read

– “Area

- wide means all monitors sited at neighborhood, urban, and regional scales, as well as those monitors sited at either micro

- or middle

- scale that are representative of many such locations in the same CBSA.” The EPA propose d to revoke the term “Community Monitoring Zone” (CMZ) and to remove references to it in 40 CFR part 5 8
. Community monitoring zone is currently***E.O. 12866 Revie w - Draft Do Not Cite, Quote, or Release During Review***; Monitoring Preamble Update 121212

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Page 7 of 62 defined as “an optional averaging area with established, well defined boundaries, such as county or census block, within an MPA 4 that has relatively uniform concentrations of annual PM 2.5 as defined by appendix N o f 40 CFR part 50 of this chapter
. Two or more community oriented state and local air monitoring stations (SLAMS) monitors within a CMZ that meet certain requirements as set forth in appendix N of 40 CFR part 50 may be averaged for making comparisons to the annual PM 2.5 NAAQS.” The EPA propose d to revoke this term and references to it since, as discussed in section VI I
. A .2 above, the EPA propos ed to eliminate all references to the now - revoked spatial averaging option throughout appendix N. The one comment di rectly addressing the proposed rule changes (from a state air agency) supported the proposal. A few industry commenters noted the change in the context of how monitoring data are used to compare to the NAAQS, but did not address the proposed specific termi nology changes. However, as explained in section III.E.3.a, several industry commenters did provide comments critical of EPA’s proposal to revoke spatial averaging which is related to revoking the term “Community Monitoring Zone”

. For the reasons explaine d above, the EPA is finalizing its proposed change to revoke the term “community

- oriented” and to replace it with the term “area

- wide.” The EPA is also finalizing its proposal to revoke the term “Community Monitoring Zone” (CMZ) and references to it in 40 CFR part 58.
2. Special Considerations for Comparability of PM 2.5 Ambient Air Monitoring Data to the NAAQS In general, a mbient monitors must meet a basic set of requirements before the
4 Monitoring Planning Area (MPA) m eans a contiguous geographic area with well established, well defined boundaries, such as a CBSA, county or State, having a common areas that is used for planning monitoring locations for PM 2.5 .***E.O. 12866 Revie w - Draft Do Not Cite, Quote, or Release During Review***; Monitoring Preamble Update 121212

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Page 8 of 62 resulting data can be used for comparison to the NAAQS . T hese requirements include the presence and implementation of an approved quality assurance project plan ; the use of methods that are reference, equivalent, or other approved method as described in appendix C to 40 CFR part 58 ; and compliance with the probe and siting path criteria as described in appendix E to 40 CFR part 58
. While these 40 CFR part 58 requirements apply to a ny monitor that provides data for comparison to the NAAQS, there are certain additional restrictions that apply only to PM 2.5 monitoring 5

. These additional restrictions provide that sites must be “population

- oriented” for comparison to either the 24

- hour or annual NAAQS, and specifically for comparison to the annual NAAQS, sites must be sited to represent area

- wide locations
. There is a relat ed provision that provides for comparing sites at micro

- or middle

- scales to the annual PM 2.5 NAAQS when the site is determined by the Regional Administrator to represent a larger region of localized high ambient PM 2.5 concentration
. The se provisions have been in the monitoring regulations since the inception of the PM 2.5 NAAQS. Nonetheless, these provisions and the fact that such monitoring requirements are not found in the requirements for all other criteria pollutants have created areas of uncertainty for EPA and state, local, and tribal agencies that base implementation decisions on monitoring requirements through programs such as dispersion modeling, SIP planning, and the calculation of transportation conformity budgets
. For example, in developing modeling guidance to support near

- road transportation conformity modeling, EPA struggled to determine how the identification of acceptable PM 2.5 receptor locations can be reconciled with the PM 2.5 monitoring

5 These are found in 40 CFR 58.30 (Special considerations for data comparisons to the NAAQS)
.***E.O. 12866 Revie w - Draft Do Not Cite, Quote, or Release During Review***; Monitoring Preamble Update 121212

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Page 9 of 62 regulations that reference potenti ally acceptable (or unacceptable) monitoring locations that may, or may not, be considered unique for purposes of comparing to the annual PM 2.5 NAAQS . Accordingly, the EPA propose d to revise these particular PM 2.5 requirements for consistency with long

- sta nding practices in all other NAAQS pollutant monitoring networks, and to ensure that interpretation of the monitoring rules does not cause ambiguity in implementation examples that also include the treatment of unmonitored areas (see 77 FR 39007

- 009 )
. Eac h of these topics is described below.
a. Eliminating the term “population oriented” from section 58.30 The EPA proposed to remove the term “populati on oriented” from section 58.30 so that there would no longer be an explicit requirement that PM 2.5 monitoring sites be “population

- oriented” for comparison to the PM 2.5 NAAQS. EPA noted that this requirement is not entirely consistent with the definition of “ambient” used in the NAAQS. The EPA’s definition of ambient air is specified in 40 CFR 50.1

– “ Ambient air means that portion of the atmosphere, external to buildings, to which the general public has access.” The EPA’s definition of “population

- oriented” is provided in 40 CFR 58.1

-

“ Population

- oriented monitoring (or sites) means residential areas, commercial areas, recreational areas, industrial areas where workers from more than one company are located, and other areas where a substantial number of people may spend a significant fraction of their day.” The NAAQS establish standards for concentrations “in the ambient air” 6

— i.e., air to which members of the public could be exposed

— and all monitors used for NAAQS regulatory purposes must be representative of ambient air

6 See 40 CFR part 50.***E.O. 12866 Revie w - Draft Do Not Cite, Quote, or Release During Review***; Monitoring Preamble Update 121212

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Page 10 of 62 concentrations. 7 Consistent with this requirement and the long

- standing pra ctice of monitor ing agencies locating ambient monitors, EPA’s experience is that PM 2.5 monitors are placed in areas that are representative of population exposures. There are no PM 2.5 monitors currently operating as “non

- population oriented” and EPA does not believe that the requirement for near

- road monitoring (discussed in detail further below) will result in monitors that are not representative of population exposures. At the same time, the specification that certain PM 2.5 monitors must be “population

- oriented” in the rules has created substantial confusion in how to treat potential locations of exposure for NAAQS

related regulatory requirements other than monitoring network design, such as in applying modeling as part of a PSD or SIP exercise
. 8 The EPA’s intention in proposing to remove the term “population oriented” from section 58.30 wa s to remove a potential source of inconsistency in the monitoring rules as they apply for all the NAAQS. As noted earlier, the NAAQS provide protection for the public health and welfa re in areas where the public can be exposed. For all other criteria pollutants, the monitoring requirements have no such restriction on the comparability of a monitor. In the case of PM 2.5 however, the additional restriction of monitors being required to be “population

- oriented” for comparability to the NAAQS has existed. The term “population oriented” has lacked a quantitative definition (e.g., the interpretation of “substantial number” in the definition of “population

- oriented”), therefore monitoring
a gencies and those stakeholders who based implementation strategies and decisions on monitoring regulations have been uncertain about which locations would meet

7 See, e.g, 40 CFR 58.1 (defining “federal reference method” as “a method for sampling and analyzing the ambient air for an air pollutant ...”) 8 Examples include dispersion modeling to support NAAQS att ainment planning, associated SIP development, and the calculation of transportation conformity budgets.***E.O. 12866 Revie w - Draft Do Not Cite, Quote, or Release During Review***; Monitoring Preamble Update 121212

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Page 11 of 62 requirements described in § 58.30, which do not exist for any other NAAQS. Monitoring agencies a re also not in a position to precisely forecast where future residential, commercial, or recreational development may occur, therefore requiring that PM 2.5 monitors that are to be compared to the NAAQS can only be located where “substantial numbers of peop le” live, work, or play (i.e., in the present tense) represents an unwise limitation on the flexibility of monitoring agencies to revise their PM 2.5 networks to account for anticipated changes in demographics or development as well as a contradiction with the inherent applicability of the NAAQS in ambient air locations where the public has access (e.g., in any location outside the perimeter of a indus trial facility). From an operational standpoint, we note that revok ing this term would not change the requirements in the PM 2.5 network design criteria
. To the extent that the phrase “population

- oriented” served to emphasize the need for micro

- or middle

- scale monitors to be representative of locations with population exposure to be comparable to the annual NAAQS, the definition of ambient air, together with the requirement in revised section 58.30 that such sites must be “area

- wide” to be comparable to t he annual NAAQS, adequately serves the same purpose. By rev ising the PM 2.5 monitoring rules to ensure consistency with the long

- standing definition of ambient air applied to the other NAAQS pollutants , the EPA will be able to more clearly define how to tre at potential exposure receptors for other NAAQS regulatory requirements , regardless of whether monitoring exists or not
. Public comments on this issue were supported by air agencies and public health and environmental groups. Two commenters from state age ncies supported the proposed change, with one noting further that regardless of a change it is still the air agency’s***E.O. 12866 Revie w - Draft Do Not Cite, Quote, or Release During Review***; Monitoring Preamble Update 121212

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Page 12 of 62 responsibility to plan a network with sites that are appropriate for comparison to the NAAQS. Several public health and environmental gro ups supported revoking “population oriented” as a condition for comparability of PM 2.5 monitoring sites to the NAAQS stating that retaining such a policy is inconsistent with the text, purpose and intent of the Clean Air Act. Most industry commenters did not support revoking “population

- oriented” as a condition for comparison to the NAAQS. Most of these comments raised concerns with using data from an area where potentially no one is exposed. In considering these comments, the EPA agrees that it is approp riate for individual air agencies to provide a recommendation in the annual monitoring network plan regarding whether any site may or may not be appropriate for co mparison to the PM 2.5 (or any) NAAQS. The roles of the air agency and the EPA in this process of identifying whether a site is, or is not, consistent with the network plan requirements for a NAAQ S are specified in the already

- established monitoring requirements of §58.10. In this approval process, the air agency initiates the recommendations and the EPA has the responsibility to approve, as appropriate, any plans that provide for changes to the network. EPA disagrees with the industry comments. As noted above, monitors (including those for PM 2.5 ) must already meet the test of be ing representativ e of ambient air to be compared to the NAAQS, and thus such monitors meeting this test will be sited in locations where people are already located, or where they could be exposed, whether or not the term “population oriented” appears in section 58.30. Mor eover, as discussed below, comparisons to the annual PM 2.5 NAAQS can be only be from monitors “ that are***E.O. 12866 Revie w - Draft Do Not Cite, Quote, or Release During Review***; Monitoring Preamble Update 121212

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Page 13 of 62 representative of area

- wide air quality ”. “Area

- wide” monitors are those at the neighborhood scale or larger, or at smaller scales if they are representative of many such locations in the same CBSA . EPA anticipates that a monitor that is sited as representative of ambient air at the neighborh ood scale or larger (or of ambient air at many smaller areas) will be representative of population exposure. This conclusion is further supported by the fact that all current monitors used for comparison with the PM 2.5 NAAQS are designated as “population

- oriented.” 9 After consideration of the public comments, the EPA is finalizing its decision to revoke use of “population

- oriented” as a condition for comparability of PM 2.5 monitoring sites to the NAAQS. The EPA concludes that the “population

- oriented” la nguage is unnecessary and inconsistent with other monitoring rules, and should therefore be removed
. b. Applicability of Micro

- and Middle

- scale Monitoring Sites to the Annual PM 2.5 NAAQS The EPA proposed language in 40 CFR section 58.30 to clarify when data from PM 2.5 monitoring sites at micro

- and middle

- scale locations can be compared to the annual PM 2.5 NAAQS. The EPA’s intent was to provide consistency and predictability in the interpretation of the monitoring regulations. The EPA’s current rules state that “PM 2.5 data that are representative, not of area

- wide but rather, of relatively unique population

- oriented micro

- scale, or localized hot spot, or unique population

- oriented middle

- scale impact sites are only eligible for comparison to the 24

- hour PM 2. 5 NAAQS. For example, if the PM 2.5 monitoring site is adjacent to a unique dominating local PM 2.5

9 The last known non population

- oriented site at Sun Metro in El Paso Texas (AQS ID: 48

- 141

- 0053), was shut down in October 2010 and is in the process o f being moved to a nearby neighborhood
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Page 14 of 62 source or can be shown to have average 24

- hour concentrations representative of a smaller than neighborhood spatial scale, then data from a monitor at the sit e would only be eligible for comparison to the 24

- hour PM 2.5 NAAQS.” We proposed clarifying language to explicitly state that measuring PM 2.5 in micro

- and middle

- scale environments near emissions of mobile sources, such as a highway, does not constitute b eing impacted by a “unique” source and so could be compared to the annual PM 2.5 NAAQS. We explained that mobile sources are rather ubiquitous and there are many locations throughout an urban area where elevated exposures attributable to such sources could occur. Therefore, we proposed that in most cases the potential location for a PM 2.5 monitoring site, including micro

- and middle

- scale sites near roadways, would be eligible for comparison to the annual NAAQS. We further noted that the existing definition of “middle scale” in appendix D to part 58 already indicates that traffic corridors can be middle scale, and hence not unique, and therefore comparable to the annual PM 2.5 NAAQS (as well as to the 24

- hour PM 2.5 NAAQS) (77 FR 39008). Air agencies that commented on this part of the proposed rule offered a variety of positions. One air agency stated that sites at these smaller scales should not be compared to the annual NAAQS. Another air agenc y stated that these sites should be considered for comparison with the annual PM 2.5 NAAQS only when the air agency initiates a decision that such sites at these smaller scales are area

- wide. A different air agency offered that all micro

- and middle

- scale s ites should be compared to the annual NAAQS since the wording of the provision is problematic and will be difficult for agencies to implement. Industry commenters were largely against finalizing such a provision. The major concern raised was that such a pr ovision combined with other related provisions***E.O. 12866 Revie w - Draft Do Not Cite, Quote, or Release During Review***; Monitoring Preamble Update 121212

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Page 15 of 62 represented an unwarranted tightening of the NAAQS. Some in dus t r y commenters point ed out that there are examples of unique locations in near road environments and as such EPA should not presume that PM 2.5 mon itors in these l o cat i ons should be ap plicable to the annual PM 2.5 NAAQS. In considering comments on this part of the rule, the EPA notes that there are already examples of where the States and EPA have d e te r mined certain micro

- and

m i d dle

- scale l o cations as applicable to th e annual NAAQS and other s where they were determined as not applicable to the annual PM 2.5 NAAQS . These cases exist where the and as described in the proposal, EPA repeats that the rules already provide that micro

and middle

- scale monitors are comparable to the NAAQS (i.e., both the 24

- hour and annual) where the States proposed and the Regional Administrator determine d s th at e ei ther t he micro

- scale or middle

- scale site did or did not represent s many similar areas in a CBSA (40 CFR 58.30 and section 4.7 to Appendix D, part 58). The EPA also notes that the existing descriptions of the types of micro

- and middle

- scale sites which are unique and cited in §58.30 are not being amended and that data fr om these types of sites would remain as not comparable to the annual PM 2.5 NAAQS. Accordingly, PM 2.5 data that are representative, not of area

- wide but rather, of relatively unique population

- oriented microscale, or localized hot spots, or unique middle s cale impact sites will only be eligible for comparison to the 24

- hour NAAQS. Our proposal was to clarify language to explicitly state that measuring PM 2.5 in micro

- and middle

- scale environments near emissions of mobile sources, such as a highway, does no t constitute being impacted by a “unique” source and so the site could be compared to the annual PM 2.5 NAAQS
. Howev er, in light of public comments pointing out that there are cases where near

- road***E.O. 12866 Revie w - Draft Do Not Cite, Quote, or Release During Review***; Monitoring Preamble Update 121212

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Page 16 of 62 envir o nments can be considered a unique location ; EPA is not finalizing this part of the rule language. However, we conclude that a near - road environment is not one of these unique or relatively unique areas, since roads are ubiquitous throughout a metropolitan
area. Examples of such locations that are considered unique and should therefore not be considered applicable to the annual PM 2.5 NAAQS are explained later in section VIII. B .3.b.i
. We are consequently adding to the regulatory text in section 58.30 a clarifying example on the treatment of near ro ad monitoring sites, indicating that a site “located in a near

- road environment where there are many other similar locations in the same CBSA “... would be considered representative of an area

- wide location and, therefore, eligible for comparison to the annu al PM 2.5 NAAQS.” As noted in the preamble to the proposed rule (77 FR 39008

- 09), air agencies and EPA will use the annual monitoring network plan described in 40 CFR 58.10 for identification and approval of sites that are suitable and sites that are not suitable for compar ison with against the annual PM 2.5 NAAQS. The EPA disagrees with those comments indicating that this change would represent a tightening of the NAAQS. As explained in section III.E.3.a on the form of the annual NAAQS, EPA carefully considered that areas s uch as traffic corridors were potential high exposure areas, including at

- risk populations, and therefore protections afforded by the standard, including the revised form, are appropriate for these locations. Monitoring in such areas as traffic corridors d oes not make the annual standard more stringent, but rather affords the populations of such middle

- and micro

- scale areas (wh e re determined to represe nt area
- wide air quality) the requisite level of protection from long

term exposure to PM 2.5 . In addition, as noted above, the change primarily provides an***E.O. 12866 Revie w - Draft Do Not Cite, Quote, or Release During Review***; Monitoring Preamble Update 121212

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Page 17 of 62 example of how to treat certain monitors in micro

- and middle

- scale environments that have always been eligible for comparison to the annual NAAQS (in cases where they where they were approved by the Region al Administrator as representing many areas within the CBSA), not the basic question of whether such monitors in micro

- and middle

scale environments were ever eligible for comparison to either the annual or 24

- hour NAAQS. 3. Changes to Monitoring for the National Ambient Air Monitoring System
a. Background As described in appendix D to 40 CFR part 58, the ambient air monitoring networks must be designed to meet three basic monitoring objectives: (a) Provide air pollution data to the general public in a timely manner
. Data can be presented to the public in a number of attractive ways including through air quality maps, newspapers, Internet sites, and as part of weather forecasts and public advisories
. (b) Support compliance with ambient air quality stand ards and emissions strategy development
. Data from FRM, FEM, and ARM monitors for NAAQS pollutants will be used for comparing an area’s air pollution levels against the NAAQS

. Data from monitors of various types can be used in the development of attainment and maintenance plans
. SLAMS, and especially National Core Monitoring Network (NCore) 10 station data, will be used to evaluate the regional air quality models used in developing emission strategies and to track trends in air pollution abatement control mea sures’ impact on improving air quality
. In monitoring locations near major air pollution sources, source

- oriented

10 NCore is a multi

- pollutant network that integrates several advanced measurements for particles, gases and meteorology ( U.S. EPA, 2011a, Appendix B, section B.4)
. Measurements required at NCore include PM 2.5 mass and speciation, PM 10

- 2.5 mass, ozone, CO , SO 2 , NO, NO y , and basic meteorology.***E.O. 12866 Revie w - Draft Do Not Cite, Quote, or Release During Review***; Monitoring Preamble Update 121212

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Page 18 of 62 monitoring data can provide insight into how well industrial sources are controlling their pollutant emissions
. (c) Support for air pollution research studies
. Air pollution data from the NCore network can be used to supplement data collected by researchers working on health effects assessments and atmospheric processes or for monitoring methods development work. To support the air quality man agement work indicated in the three basic air monitoring objectives, a network must be designed with a variety of types of monitoring sites
. Monitoring sites must be capable of informing managers about many things including the peak air pollution levels, t ypical levels in populated areas, air pollution transported into and outside of a city or region, and air pollution levels near specific
sources . Following is a listing of six general site types: (a) sites located to determine the highest concentrations ex pected to occur in the area covered by the network (highest concentration) ; (b) sites located to measure typical concentrations in areas of high population density (population oriented) ; (c) sites located to determine the impact of significant sources or s ource categories on air quality (source impact or source oriented) ; (d) sites located to determine general background concentration levels (general background) ; and (e) sites located to determine the extent of regional pollutant transport among populated a reas (regional transport) ; and in support of secondary standards (welfare related impacts)
. b. Primary PM 2.5 NAAQS The EPA propose d to add a near

- road component to the PM 2.5 network design criteria and to clarify the use of approved PM 2.5 continuous FEMs at S LAMS.***E.O. 12866 Revie w - Draft Do Not Cite, Quote, or Release During Review***; Monitoring Preamble Update 121212

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Page 19 of 62 i. Addition of a Near

- road Component to the PM 2.5 Monitoring Network The EPA proposed to add a near

- road component to the PM 2.5 monitoring network (77 FR 39009). The EPA explained that there are gradients in near

- roadway PM 2.5 that are most likely to be associated with heavily travelled roads ( particularly those with significant heavy

- duty diesel activity ) , and that the largest numbers of impacted populations are located in the largest CBSAs in the country (Ntziachristos et al., 2007 ; Ross et al., 2007; Yanosky et al., 2008; Zwack et al., 2011). The EPA further noted that by adding a modest number of PM 2.5 monitoring sites that are leveraged with measurements of other pollutants in the near

- road environment, a number of key monitoring objectives will be supported, including collection of NAAQS comparable data in the near

- road environment , support for long

- term health studies investigating adverse effects on people, providing a better understanding of pollutant gradients impacting neigh borhoods that parallel major roads, availability of data to validate performance of models simulating near

- road dispersion, characterization of areas with potentially elevated concentrations and/or poor air quality , implementation of a multi

pollutant para digm as stated in the NO 2 NAAQS proposed rule (74 FR 34442, July 15, 2009) , and monitoring goals consistent with existing objectives noted in the specific design criteria for PM 2.5 described in appendix D, 4.7.1(b) to 40 CFR part 58
. The monitoring method s that are appropriate for this purpose are an FRM, FEM, or ARM. The EPA recognize d that there are limitations in the ability of some of these methods to accurately measure PM 2.5 mass due to the incomplete retention of semi

volatile material on the samplin g medium (U.S. EPA, 2009a, section 3.4.1 .1)
. This limitation is relevant to the near

- road environment as well as to other environments***E.O. 12866 Revie w - Draft Do Not Cite, Quote, or Release During Review***; Monitoring Preamble Update 121212

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Page 20 of 62 where PM is expected to have semi

- volatile components . The EPA also recognize d that continuous PM 2.5 FEMs, which provide mass concentration data on an hourly basis, are better suited to accomplish the goals of near

- road monitoring as they will complement the time resolution of the other air quality measurements and traffic data collected at the same sites
. In this regard, pa rticular PM 2.5 FEMs are generally better suited for near

- road monitoring than FRMs
. However, filter

- based FRMs do offer some advantages which may be highly desirable for near

- road monitoring, such as readily available filters for later chemical analysis su ch as for elemental composition by x

- ray fluorescence and black carbon (BC) by transmissometry
. As a result of these tradeoffs, monitoring agencies are encouraged to select one or more PM 2.5 methods for deployment at near

– road monitoring stations that best meet their agencies monitoring objectives while ensuring that at least one of those methods is appropriate for comparison to the NAAQS (i.e., a FRM, FEM, or ARM). The EPA believes that by allowing monitoring agencies to choose the FRM, FEM, or ARM method( s) that best fits their needs, whether filter

- based or continuous, the data will still be able to meet the objectives cited above while ensuring maximum flexibility for the monitoring agencies in the operation of their network. Additionally, the EPA noted that the near

- road sites would provide a valuable platform for evaluating emerging monitoring technologies and for measuring other pollutants besides PM 2.5 mass to enhance knowledge of exposure in the near road environment and to support the characterizati on and comparison of specific method readings in an emission

- rich environment. Further, i n its response to the EPA on a “Review of the “Near

- road Guidance Document

– Outline” and “Near

- road Monitoring Pilot Study Objectives and Approach” ( U.S. EPA, 2010i), the CASAC AAMMS cited***E.O. 12866 Revie w - Draft Do Not Cite, Quote, or Release During Review***; Monitoring Preamble Update 121212

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Page 21 of 62 several other measurements that may be useful or potentially linked to health and welfare effects such as BC, ultrafine particles, and particle size distribution (Russell and Samet, 2010b, pp. xi and xii)
. The EPA agrees with these r ecommendations and encourages monitoring agencies to include these measurements, and others cited in the Subcommittee letter, where possible , in addition to the PM 2.5 mass measurement. The EPA also encourage s monitoring agencies to explore partnerships wit h instrument manufacturers and researchers to use the sites to evaluate the performance of emerging PM 2.5 monitoring methods in the near

- road environment, especially potential or current FEMs able to provide temporally resolved data and capture the semi

- vo latile components of PM 2.5 . Such emerging PM 2.5 methods could be operated as SPMs 11 to provide comparisons to the EPA approved methods supporting compliance to advance the understanding of instrument performance in the near

- road environment. Monitoring agencies are also encouraged to partner with instrument manufacturers and researchers to operate monitors able to measure other PM properties relevant for the near

- road environment (e.g., ultrafine particles , BC) to provide additional information about exposure to PM in this environment. The EPA is interested in supporting monitoring agenci es willing to operate and report the data from these supplemental monitors. EPA notes that the implementation of additional measurements, while encouraged, is completely voluntary to ensure maximum flexibility for state monitoring programs. The EPA belie ve s that requiring a modest network of near

- road compliance PM 2.5 monitors is necessary to provide characterization of concentrations in near

- road

11 SPMs means a monitor included in an air agency’s monitoring network that the agency has designated a a special purpose monitor in its monitoring network plan and in the Air Quality System database, and which the air agency does not count toward when showing compliance with the minimum monitoring requirements in appendix D to Part 58.***E.O. 12866 Revie w - Draft Do Not Cite, Quote, or Release During Review***; Monitoring Preamble Update 121212

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Page 22 of 62 environments including for comparison to the NAAQS. These long

- term monitors will supplement shorter

- term net works operated by researchers to support the tracking of long

- term trends 12 of near - road PM 2.5 mass concentrations and other pollutants in near

road environments where people are exposed
. Therefore, the EPA propose d to require
near - roadway monitoring of PM 2 .5 at one location within each CBSA with a population of one million persons or greater

. The EPA believes that this network will be adequate to support the NAAQS since the largest CBSAs are likely to have greater numbers of exposed populations, a higher li kelihood of elevated near

- road PM 2.5 concentrations, and a wide range of diverse situations with regard to traffic volumes, traffic patterns, roadway designs, terrain/topography, meteorology, climate, surrounding land use and population characteristics
. Given the latest population data available, th e proposed requirement would result in approximately 5 2 required near

- road PM 2.5 monitors across the country
. An indirect benefit of this network design is that monitoring agencies in these largest CBSAs are mo re likely to already have redundant monitors that could be relocated to the
near - road environment , reducing costs for equipment and ongoing operation. 13 While only a single near - road PM 2.5 monitor is required within each of the CBSAs, agencies may elect to add additional PM 2.5 monitoring sites in near

- road environments. While the EPA recognize d that the location of maximum concentration of PM 2.5 exposure from roadway sources might differ from the maximum location of NO 2 or o t her pollutants, the EPA propose d to require that near

- road PM 2.5 monitors be collocated with

12 For example, the emissions used for the PM NAAQS RIA modeling show that nationwide on

- road primary PM 2.5 emissions are expected to be reduced by 63% between 2007 and 2020. Additionally, the elemental carbon portion of the on

- road emissions is expected to drop by 81% between 2007 and 2020. Th erefore, we expect that measured near

- road PM 2.5 gradients will be much lower in the future as elemental carbon is a large fraction of the existing gradient. 13 EPA Regional Administrator approval would be required prior to the discontinuation of SLAMS monitors, based on the criteria described in 40 CFR 58. 14(c).***E.O. 12866 Revie w - Draft Do Not Cite, Quote, or Release During Review***; Monitoring Preamble Update 121212

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Page 23 of 62 the planned NO 2 monitors
. The NO 2 network design considers multiple factors that are also relevant for PM 2.5 concentrations ( i. e., average annual daily traffic , fleet mix , roadway design, congesti on patterns, terrain, and meteorology ) and significant thought and review has already gone into its design, including pilot studies at five locations, and the development of a technical assistance document in conjunction with the affected monitoring agenci es and the CASAC AAMMS (Russell and Samet, 2010b) to support deployment
. Further, this collocation will allow multiple pollutants to be tracked in the
near - road environment. To the extent that air agencies are still determining the optimum location for the ir multi

- pollutant 14 near - road monitoring stations, EPA encourages consideration of sites that best reflect measurement of maximum concentrations associated with exposure of people living in areas that parallel major roads, to maximize the value of the data for use later in health studies. Therefore, while compromises may be necessary when siting a multi

- pollutant near road monitoring station, on balance, the EPA believes this is the most efficient and beneficial approach for deployment of this component of the network
. The EPA notes that the planned 52 near

- road monitors represent a small number of the total approximate 900 operating PM 2.5 monitoring stations across the country. The EPA could have proposed more near

- road sites, however, the addition of sites in lower population CBSAs is not expected to lead to much if any difference in characterization of air quality since the bump in PM 2.5 concentration associated with near

- road environments in lower population CBSAs, which typically have correspondingly les s travelled roads, is expected to be very small. The EPA could also have proposed multiple sites in larger

14 NO 2 , CO, and now PM 2.5 measurements are all expected to be collocated at near

- road monitoring stations.***E.O. 12866 Revie w - Draft Do Not Cite, Quote, or Release During Review***; Monitoring Preamble Update 121212

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Page 24 of 62 CBSAs; however, State monitoring programs are already working towards representative
near - road monitoring stations and there is a synergistic value i n ensuring these measurements are collocated with multiple other measurements to serve the monitoring objectives noted above. Since EPA has already finalized requirement of CO monitoring at near
- road stations in CBSA’s with a population of 1 million or mor e at sites that are collocated with NO 2 , there would be less value in requiring any more than 52 PM 2.5 monitors as any more stations will not have CO for use in multi

- pollutant monitoring objectives (e.g., health studies and model evaluation). Ideally, nea r - road sites would be located at the elevation and distance from the road where maximum concentration of PM 2.5 levels exposure occur s in this environment, representing locations where populations are exposed ; for example, in apartment s and other housing ; s chools located al ong major roadways ; indu s trial parks where workers exposed ; and in recreational areas such as greenways, bikeways, and other park facilities that are often dev e lop ed along roads. and within reasonable proximity to an other area wide PM 2.5 compliance monitoring site at which a similar PM monitor is used (i.e., for comparison purposes) . However, S s pecific to probe and siting criteria for near

- road PM 2.5 monitors, which is explained later in this section, EPA did not set additional criteria on what the elevation and distance requirements should be, beyond what is already defined for PM 2.5 or near - road NO 2 monitors for reasons explained above. Also, the EPA did not propose that the near

- road PM 2.5 monitors be located within a specific distance o f other
area - wide sites; however, monitoring agencies are encouraged to consider that a near

road site selected in accordance with monitoring requirements and also located in proximity to a robust area

- wide site, such as an NCore station, would provide use ful***E.O. 12866 Revie w - Draft Do Not Cite, Quote, or Release During Review***; Monitoring Preamble Update 121212

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Page 25 of 62 information in characterizing the near

- road contribution to multiple pollutants, including PM 2.5 and tracking the decreasing trend that is expected in the PM 2.5 nea r - ro a d gradient over time
. The timeline to implement the near

- road PM 2.5 monitors should be as minimally disruptive to on

- going operations of monitoring agency programs as possible recognizing monitoring agenc y ies resource constraints , while still meeting the need to collect for
near - road PM 2.5 data in a timely fashion
. Since the near

- road PM 2.5 monitors were proposed to be collocated with the emerging near

- road NO 2 network that was scheduled to be operational by January 1, 2013 15 , the EPA believes it is appropriate to wait until after the near

- road NO 2 network is established before impl ementing the near

- road PM 2.5 monitors. Therefore, the EPA propose d that each PM 2.5 monitor planned for collocation with a near

- road NO 2 monitoring site be implemented no later than January 1, 2015
. The EPA received comments from a number of air agencies, i ndustrial groups, and environmental and public health organizations on its proposal to require PM 2.5 monitoring in near

- road environments. Among comments from air agencies, several commenters did not support the addition of near road monitoring citing the challenges of siting these stations and the additional cost it would require to operate the monitors. Several air agencies recognized the value of adding monitors to provide better characterization of exposures in near

- road environments, but recommended a slower deployment of the PM 2.5 monitors so that it can be phased in over a multi

- year period. Several air agencies recommended that the PM 2.5 monitoring in the near

- road environment be deployed on a phased

- in schedule with the
15 The EPA has proposed a revised timeline for deployment of the near

- road NO 2 monitors, where all CBSAs with one million or more people are to have their first near

road NO 2 station operational by January 1, 2014 (77 FR 64244, October 19, 2012).***E.O. 12866 Revie w - Draft Do Not Cite, Quote, or Release During Review***; Monitoring Preamble Update 121212

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Page 26 of 62 first such monitors being req uired no sooner than one year after deployment of the NO 2 sites. These air agencies stated that phasing in of the PM 2.5 monitors in the near road environment would allow more time to learn and share information on what worked best in deploying the NO 2 monitors at near

- road monitoring stations, since NO 2 is the first pollutant required to be monitored at near

- road stations. A few air agencies identified a need to more clearly support or require the maintenance of as much of the existing network of neigh borhood scale PM 2.5 monitoring sites as possible in regulatory text. These neighborhood scale PM 2.5 sites were identified by commenters as the most broadly representative sites for characterizing CBSA wide exposures that are supportive of a number of monit oring objectives. A few air agencies also identified a need for flexibility in the proposed network design requirement that PM 2.5 near - road monitors must be collocated with the NO 2 monitors in the near

- road environment. The commenters suggested allowing fl exibility for air agencies to meet the requirement for PM 2.5 in a
near - road environment by siting at a different near

- road location where PM 2.5 concentrations are expected to be high. Most industry commenters did not support the addition of near

- road monit oring for PM 2.5 , again arguing that using data from such monitors, for comparison to the NAAQS, combined with other changes (i.e., elimination of “population

- oriented” as a criteria for comparison to the NAAQS and the elimination of spatial averaging) woul d represent, in their judgement, a tightening of the PM 2.5 NAAQS. A few of these commenters asserted that monitoring in the near

- road environment is not representative of ambient air exposures. A few industry comments noted that if the EPA required PM 2.5 monitoring in the near

- road environment, any data collected should not be used for***E.O. 12866 Revie w - Draft Do Not Cite, Quote, or Release During Review***; Monitoring Preamble Update 121212

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Page 27 of 62 comparison to the NAAQS. One commenter stated it had no problem with monitoring in the near

- road environment, so long as any such monitoring used to compare to the PM 2.5
an nual NAAQS is population

– oriented. One commenter stated that the decision to co

locate with NO 2 monitors was based on convenience and the intent of the NO 2 near - road monitoring is to find the highest micro

- scale concentrations within a few meters of the

m ost heavily travelled expressways, representing a unique situation. Environmental and public health groups strongly support the addition of PM 2.5 monitoring to the near

- road environment. Commenters cited the large number of people that live in proximity to major roadways 16 in their support for adding these monitors, that such protection of people in these environments in long overdue, and that such data therefore be used for comparison to the NAAQS. Regarding comments from air agencies that the near

- road monitors are challenging to site and that there is additional cost in operating these monitors, the EPA maintains that the major challenges in siting would already be accomplished by implementing the required NO 2 monitoring stations in near

- road environmen ts since the EPA fully expects that the PM 2.5 monitors will be placed at the NO 2 near roadway stations and has revised the PM 2.5 monitoring requirements consistent with that expectation. The EPA also points out that the requirements for the minimum number of PM 2.5 monitors is unchanged and that in most cases the addition of near

- road PM 2.5 monitors can be accomplished by relocating an existing monitor, with no net increase in
16 One study identified that 45 million Americans live within 300 feet of a major roadwa y or other source of mobile emissions. The commenters information is based on the American Housing Survey, which is available on the web at: http://www.census.gov/housing/ahs/data/ahs2009.h tml
. The survey provides an estimate of the county’s housing units in the U.S. that are located with 300 feet of a highway with four or more lanes, or a railroad, or an airport.***E.O. 12866 Revie w - Draft Do Not Cite, Quote, or Release During Review***; Monitoring Preamble Update 121212

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Page 28 of 62 monitors. Thus, while we are requiring a new component of the PM 2.5 monitoring net work, the overall size of the network is expected to remain about the same, and we expect that air agencies can meet this requirement by relocating existing lower

- priority monitors. In considering comments from air agencies on a schedule for implementing P M 2.5 monitors at near road monitoring stations, the EPA is persuaded by commenters from air agencies who stated that a phased deployment of the PM 2.5 monitors would be a better approach as it would allow agencies to learn from the deployment of the NO 2
mon itors and a first phase of PM 2.5 monitors. Phasing in the deployment of monitors is also consistent with previous CASAC advice (Russell and Samet, 2010b) o n a schedule for deployment of near

- road NO 2 monitors. Regarding comments from air agencies on mainta ining the neighborhood scale monitoring stations as the largest part of the network as these sites are the most broadly representative of exposures across CBSAs, the EPA supports such a goal. Neighborhood scale monitoring sites remain the backbone of the P M 2.5 monitoring network and they will continue to represent over two thirds of the operating network following the deployment of the near

- road monitors. The EPA expects that each CBSA required to monitor for PM 2.5 will maintain its existing highest concent ration area

- wide monitoring site (referred to as the design value site) and not attempt to move such sites to near

- road environments. Maintaining the area

- wide and largely neighborhood scale design value sites is critical to the long

- standing goal of using data to support a variety of monitoring objectives. The EPA also recognizes that while every PM 2.5 monitor has value in some capacity at its current location, air agencies are expected to recommend relocation of monitors that are relatively low in priorit y to meet the near

- road requirement.***E.O. 12866 Revie w - Draft Do Not Cite, Quote, or Release During Review***; Monitoring Preamble Update 121212

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Page 29 of 62 Regarding comments from air agencies on the need for flexibility in the network design requirement that PM 2.5 near - road monitors must be collocated with the NO 2 monitors in the near

- road environment, the EPA points out that it prefers to maintain this requirement so that the multi

- pollutant data are available to support the monitoring objectives cited above. However, the EPA also recognizes there may be cases whe re an air agency recommends siting their near

- road PM 2.5 monitor in another high concentration near

- road environment. The EPA believes such cases will be very limited, but that these situations can be supported in one of two ways. First, EPA and the air ag ency can use their discretion to site two near

- road PM 2.5 monitors in the area. Second, the EPA can use its discretion in approving a deviation from the PM 2.5 monitoring requirements as already exists in the network design criteria. Such deviations are to be approved by the Regional Administrator as described in section 4.7.1 of Appendix D to part 58. Regarding the comment that PM 2.5 monitors in near

- road environments were sited for convenience , which due to siting with NO 2 monitors a few meters from the r oad presents a unique situation, the EPA disagrees that these monitors were sited solely for convenience or that they would represent a unique situation within an urban area
. On the initial point , t he EPA believes that the characterization of representati ve maximum PM 2.5 concentration s due to on
- road mobile sources and the appropriate location of such PM 2.5 monitors will be the same approximate locations that are the focus of the near - road NO 2 network
. This is due to the fact that PM 2.5 , like NO X, is disp roportionately influenced by heavy duty (HD) vehicles which are predominantly diesel fueled, when compared to light duty (LD) vehicles which are primarily gasoline fueled. Specifically, for both PM 2.5 and***E.O. 12866 Revie w - Draft Do Not Cite, Quote, or Release During Review***; Monitoring Preamble Update 121212

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Page 30 of 62 NOx, HD vehicles emit more of these two pollutants and their precursors on a per vehicle basis than LD vehicles. The EPA recognize d this fact in the near

- road NO 2 network by requiring states to consider the fleet mix of candidate road segments where near

- road monitoring might occur. In the design of the NO 2 near - road network where the PM 2.5 monitors will be installed, s tates were instructed to place a higher priority on those highly trafficked roads which have more diesel fueled vehicles using a metric called the fleet equivalent average annual daily tra ffic
. 17 As such, the Agency believes it is appropriate that required near

- road PM 2.5 monitors would be located with near

- road NO 2 monitors as they are similarly influenced not only by fleet mix but also by total traffic count, congestion patterns, roadway design, terrain, and meteorology. On the s econd point with regard to such sites representing a unique situation within an urban area , EPA again points out that the determination of a near

- ro a d micro

- or middle

- scale site being considered to represent “ar ea - wide” air quality or “ unique ” will be made on a case by case basis with the monitoring agency providing such rec o mmend a tion s in their a nnual monit or ing network plans described in §58.10. Examples of such “unique” micro

- and middle

- scale locations are provided later in this section. these major roadways are ubiquitous throughout metropolitan areas and as such represent many such locations that occur within an urban area and the resulting exposure of the population in residential, commercial and recr eational areas
. We do not accept the comment that siting some monitors in near roadway environments makes the standard impermissibly stricter. A significant fraction of the population lives in proximity to major roads. These exposures occur in locations that

17 See the Near

- road NO 2 Monitoring Technical Assistance Document at: http://www.epa.gov/ttn/amtic/files/nearroad/NearRoadTAD.pdf***E.O. 12866 Revie w - Draft Do Not Cite, Quote, or Release During Review***; Monitoring Preamble Update 121212

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Page 31 of 62 represent ambient air for which the agency has a responsibility to ensure the public is protected with an adequate margin of safety. Ignoring monitoring results from such areas (or not monitoring at all) would abdicate this responsibility. Put anoth er way, monitoring in such areas does not make the standard stricter, but rather affords requisite protection to the populations, among them at

- risk populations, exposed to fine particulate in these
areas. Thus, the EPA has made a determination to protect all area

- wide locations, including those locations with populations living near major roads that are representative of many such locations throughout an area. As discussed above, EPA concludes that the requirement to locate monitors to represent ambient a ir, along with other siting requirements, will ensure that monitors represent PM 2.5 concentrations in areas of potential public exposure
. We do recognize, however, the possibility that some near

- road monitoring stations may b e representative of relatively unique locations versus the more representative area

- wide situation mentioned above. This could occur because an air agency made a siting decision based on NO 2 criteria that resulted in the characterization of a microscale environment that is not considere d area

- wide for PM 2.5 ; for example, due to proximity to a unique source like a tunnel entrance, nearby major point source, or other relatively unique microscale hot spot. In these types of scenarios, air agencies would identify the site as a unique monitor comparable only to the 24

- hour PM 2.5 NAAQS per the language in section 58.30, and not comparable to the annual NAAQS , through the Annual Monitoring Network Plan process described earlier . Although EPA expects most
near - road PM 2.5 monitors to be sited to r epresent area
- wide conditions, since a vast***E.O. 12866 Revie w - Draft Do Not Cite, Quote, or Release During Review***; Monitoring Preamble Update 121212

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Page 32 of 62 majority of the near

- road stations have yet to be installed, we believe that providing such clarity and flexibility in siting and NAAQS comparability is warranted.
After careful consideration of the public comme nts, the EPA is finalizing its decision to add PM 2.5 monitors to the near

- road monitoring stations. The EPA is finalizing this decision as the near

- road environment is an area where significant public exposure can occur, recognizing that this is a gap in t he current PM 2.5 monitoring networks, and because these PM 2.5 monitors will be collocated with NO 2 monitors in the
near - road environment, there will not be a significant additional burden on the air agencies 18 . However, in recognition of the comments from a ir agencies above, EPA is finalizing a revised and phased schedule for deployment of the PM 2.5 monitors at near

road stations. A minimum of one PM 2.5 monitor in each CBSA with a population greater than or equal to ≥ 2.5 million is to be collocated at a near

- road NO 2 monitoring station and must to be operational by January 1, 2015. The remaining CBSAs (i.e., those CBSAs with populations greater than or equal to ≥ 1M, but less than 2.5M) must operational by January 1, 2 017. This schedule will ensure that air agencies have sufficient time to learn from deployment of the NO 2 monitors in near

- road environments, that the highest population CBSAs begin operating their PM 2.5 monitors in near

- road environments first, and that t he remaining PM 2.5 monitors are deployed on the same schedule as the CO monitors (also, required by January 1, 2017 19 ). In consideration of the comments regarding maintaining neighborhood scale monitoring sites as the largest portion of the network, the EPA is revising the wording of a requirement t hat requires at least one site
18 The incremental one

- time cost of moving the 52 monitors required to be located in the near - road environment is described in section X.B

– Paperwork reduction Act. 19 76 FR 54294, August 31, 2011***E.O. 12866 Revie w - Draft Do Not Cite, Quote, or Release During Review***; Monitoring Preamble Update 121212

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Page 33 of 62 to be in an area

- wide location of expected maximum concentration , to wording that states that such sites must be in an area

- wide location of expected maximum concentration while also being at the neighborhood or larger scale of representation
. ii. Use of PM 2.5 Continuous FEMs at SLAMS The EPA propose d that each agency specify its intention and rationale to use or not use data from continuous PM 2.5 FEMs that are eligible for comparison to the NAAQS as part of its annual monitoring network plan due to the applicable EPA Region Office by July 1 each year
. The proposal also provide d that the EPA Regional Administrator would be responsible for approving annual monitoring network plans where ag encies have provided a recommendation that certain PM 2.5 FEMs be considered ineligible for comparison to the NAAQS
. In 2006, the EPA finalized new performance criteria for approval of continuous PM 2.5 monitors as either Class III FEMs or ARMs . At the time of proposal, the EPA ha d already approved six PM 2.5 continuous FEMs 20 and there are nearly 200 of these monitors already operating in State, local, and Tribal networks
. Monitoring agencies have been deploying and field

- testing these units over the last couple of years and the EPA recently compiled an assessment of the FEM data in relationship to collocated FRMs (Hanley and Reff, 2011; U.S. EPA, 2011a, pp. 4

- 50 to 4

- 51)
. As described in the proposal (FR 38983) , the EPA found that some sites with continuous PM 2.5 FEMs have an acceptable degree of comparability with collocated FRMs, while others had poor data comparability that would not meet the performance criteria used to approve the FEMs (71 FR 61285

- 61286, Table C

- 4, October 17, 2006)
. The EPA is encouraging use of the FEM data from

20 The EPA maintains a list of approved Reference and Equival ent Methods on its web site at: http://www.epa.gov/ttn/amtic/criteria.html
.***E.O. 12866 Revie w - Draft Do Not Cite, Quote, or Release During Review***; Monitoring Preamble Update 121212

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Page 34 of 62 those sites with acceptable data comparability including for purposes of comparison to the NAAQS
. For sites with unacceptable data comparability, the EPA is working closely with the monitoring committee of the NACAA, instrument manufacturers, and monitoring agencies to document best practices on these methods to improve the comparability and consistency of resulting data wherever possible . Th e EPA believe s that the performance of many of these continuous PM 2.5 FEMs at locations with poor data comparability can be improved to a point where the acceptance criteria noted above can be met. Given the varying data comparability of continuous PM 2.5 FEMs noted above, we believe that a need exists for flexibility in the approac hes for how such data are used , particularly for the objective of determining NAAQS compliance
. Accordingly, we propose d that monitoring agencies address the use of data from PM 2.5 continuous FEMs in their annual monitoring network plans due to the applica ble EPA Regional Office by July 1 of each year for any cases where the agency believes that the data generated by PM 2.5 continuous FEMs in their network should not to be compared to the NAAQS
. The annual network plans would include assessments such as comp arisons of continuous FEMs to collocated FRMs, and analyses of whether the resulting statistical performance would meet the established approval criteria
. Based on these quantitative analyses, monitoring agencies would have the option of requesting that da ta from continuous FEMs be excluded from NAAQS comparison subject to EPA approval ; however, these data could still be utilized for other objectives such as AQI reporting. The issue exists of whether such data use provisions should be prospective only (i.e ., future NAAQS comparability excluded based on an analysis of recent past***E.O. 12866 Revie w - Draft Do Not Cite, Quote, or Release During Review***; Monitoring Preamble Update 121212

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Page 35 of 62 performance) or a combination of retrospective and prospective (i.e., the implications of unacceptable FEM performance impacting usage of previously collected data as well as future data) . In the proposal, the EPA stated that in most cases, monitoring agencies should be restricted to addressing prospective data issues to provide stability and predictability in the long

- term PM 2.5 data sets used for supporting attainment decisions
. Ho wever , in the first year after this proposed option would become effective, we indicated it would be appropriate to provide monitoring agencies with a one

- time opportunity to review already reported continuous PM 2.5 FEM data and request that data with unacceptable performance be restricted (retrospectively) from NAAQS comparability
. Accordingly, in the first year after this rule becomes effective, we propose d that monitoring agencies have the option of requesting in their annual monitoring network plans that a portion or all of the existing continuous PM 2.5 FEM data, as applicable, as well as future data, be restricted from NAAQS comparability for the period of time that the plan covers. 21 In the proposal we stated tha t a nnual monitoring network plans in subsequent years would only need to cover new data for the period of time that the plan covers. As noted above, in cases where an agency is operating a PM 2.5 continuous FEM that is not meeting the expected performance criteria used to approve the FEMs (71 FR 61285 to 61286, Table C

- 4, October 17, 2006) when compared to their collocated FRMs, an agency can recommend that the data not be used for comparison to the NAAQS
. However, all required SLAMS would still be required to have an operating FRM (or other well performing FEM) to ensure a data record is available for comparison to the

21 Data from any PM 2.5 monitor being used to meet minimum monitoring requirements could not be restricted from NAAQS comparability.***E.O. 12866 Revie w - Draft Do Not Cite, Quote, or Release During Review***; Monitoring Preamble Update 121212

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Page 36 of 62 NAAQS
. In cases where a PM 2.5 continuous FEM was not meeting the expected performance criteria, and the Regional Administrator has approved a recommendation that the FEM data not be considered eligible for comparison to the NAAQS, the data would still be required to be loaded to AQS; however, these data would be identified distinctly from data used for comparison to the NAAQS
. The goal of pro posing to allow monitoring agencies the opportunity to recommend not having data from PM 2.5 continuous FEMs as comparable to the NAAQS is to ensure that only high quality data (i.e., data from FRMs which are already well established and new continuous FEMs that meet the performance criteria used to approve FEMs when compared to collocated FRMs operated in each agencies network) are used when comparing data to the PM 2.5 NAAQS
. Under the current monitoring regulations, a monitoring agency can identify a PM 2.5 continuous FEM as a n SPM, which allows the monitor to be operated for up to 24 months without its data being used in comparison to the NAAQS
. While 24 months should be sufficient time to operate the monitor across all seasons, assess the data quality, and in some cases resolve operational issues with the instrument, it may still leave some agencies with m onitor s whose data are not sufficiently comparable to data from their FRMs
. In these cases there may be a disincentive to continue operating the PM 2.5 con tinuous FEM, especially in networks where the monitoring data are near the level of the NAAQS
. With the proposed provision , where a monitoring agency can recommend not having data from PM 2.5 continuous FEMs be comparable to the NAAQS, a monitoring agency c an continue to operate their PM 2.5 continuous FEM to support other monitoring objectives (e.g., diurnal characterization of PM 2.5 , AQI forecasting and reporting), while working through options for improved data***E.O. 12866 Revie w - Draft Do Not Cite, Quote, or Release During Review***; Monitoring Preamble Update 121212

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Page 37 of 62 comparability while still providing data for comparison to the NAAQS from an FRM
. The EPA believes that an assessment of FEM performance should include several elements based on the original performance criteria . Th e Agency also believe s that certain modifications to the performance criteria are appr opriate in recognition of the differences between how monitoring agencies operate routine monitors and how instrument manufacturers conduct required FRM and FEM testing protocols
. The details below summarize these issues
. The EPA propose d to use the performance criteria used to approve the FEMs (71 FR 61285 to 61286, Table C

- 4, October 17, 2006) for those agencies that recommend not having data from PM 2.5 continuous FEMs be comparable to the NAAQS
. To accommodate how routine monitoring net works operate, the EPA propose d that agencies seeking to demonstrate insufficient data comparability base their assessment mainly on collocated data from FRMs and continuous FEMs at monitoring stations in their network
. The EPA does not believe it is pract ical to utilize the requirement in table C

- 4 of 40 CFR part 53 for having multiple FRMs and FEMs at each site since such arrangements are not typically found in monitoring agency networks
. Accordingly, the requirement for assessing intra

- method replicate p recision would be inapplicable
. Another consideration is the range of 24

- hour data concentrations, for instance, the performance criteria in table C

- 4 of 40 CFR part 53, provides for an acceptable concentration range of 3 to 200 μg/m 3

. However, the EPA not e s that during an evaluation of data quality from two FEMs ( U.S. EPA, 2011a, p. 4

- 50), th e Agency found that including low concentration data w as helpful for understanding whether an intercept or slope was driving a potential bias in an instrument
. Therefo re, the EPA propose d that agencies may include low concentration***E.O. 12866 Revie w - Draft Do Not Cite, Quote, or Release During Review***; Monitoring Preamble Update 121212

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Page 38 of 62 data (i.e., below 3 μg/m 3 ) for purposes of evaluating the data comparability of continuous FEMs
. With regard to the minimum number of samples needed for the assessment, the EPA note s that a m inimum of 23 sample pairs are specified for each season in table C

- 4 of 40 CFR part 53
. Having 23 sample pairs per season should be easily obtainable within one year for sites with a FRM operating on at least a 1 in 3 day sample frequency and we propose d t hat this requirement be applicable to the assessments being discussed here
. For sites on a one in 6 day sampling frequency, two years of data may be necessary to meet this requirement
. The EPA recognizes that it would be best to assess the data based on th e most recently available information; however, having data across all seasons in multiple years will provide a more robust data set for use in the data comparability assessment; therefore , the EPA propose d that data quality assessments be permitted to uti lize up to the last three years of data for purposes of recommending not having data from PM 2.5 continuous FEMs be comparable to the NAAQS. The EPA recognizes that only a portion of continuous PM 2.5 FEMs will be collocated with FRMs, and it would be imprac tical to restrict the applicability of data comparability assessments to only those sites that had collocated FRM and FEM monitors
. In these cases, the monitoring agency will be permitted to group the sites that are not collocated with an FRM with another similar site that is collocated with an FRM for purposes of recommending that the data are not eligible for use in comparison to the NAAQS
. Monitoring agencies may recommend having PM 2.5 continuous FEM data eligible for comparison to the NAAQS from locations where the method has been demonstrated to provide acceptable data comparability, while also recommending not having it eligible in other types of areas where the method has not been de monstrated to***E.O. 12866 Revie w - Draft Do Not Cite, Quote, or Release During Review***; Monitoring Preamble Update 121212

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Page 39 of 62 meet data comparability criteria
. For example, a rural site may be more closely associated with aged particles where volatilization issues are minimized resulting in acceptable data comparability between filter

- based and continuous methods, w hile a highly populated urban site with fresh emissions with higher volatility may result in higher readings on the PM 2.5 continuous FEM that would not meet the expected performance criteria as compared to a collocated FRM
. In all cases where a monitoring agency chose to group sites for purposes of identifying a subset of PM 2.5 continuous FEMs that would not be comparable to the NAAQS, the assessment submitted with the annual monitoring network plan would have to provide sufficient detail to support the ide ntification of which combinations of method and sites would, and would not, be comparable to the NAAQS, as well as the rationale and quantitative basis for the grouping and recommendation. Most comments received on this issue were from air agencies. All ai r agencies either supported the proposal or supported it with a recommendation to continue to allow for retrospective assessments to be used such that data would not be compared to the NAAQS, if such an assessment showed that the data were not of sufficien t comparability to a collocated FRM such that the continuous FEM should not be compared to the NAAQS. One air agency supported the proposal, except though it had reservations about how to best group sites together when a particular PM 2.5 continuous FEM is not collocated with a FRM. The EPA notes the support by air agencies to finalize this provision. EPA also notes that all commenters who offered input on the retrospective use of assessments were supportive of allowing continued retrospective assessments in annual monitoring***E.O. 12866 Revie w - Draft Do Not Cite, Quote, or Release During Review***; Monitoring Preamble Update 121212

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Page 40 of 62 network s plans so that data may be recommended as excluded from comparison to the NAAQS under certain provisions. However, the EPA has some reservations about how and under what circumstances such an allowance should be made. The EPA notes the concern expressed f

rom one agency about how to best group sites together when considering an assessment. On the issue of whether to allow data collected to be retrospectively excluded from comparison to the NAAQS, the EPA notes there are a number of considerations, including that several air agencies support such a policy. The EPA has evaluated how this issue can be achieved and believes that some consideration should be allowed, but also wants to ensure there is a consistent and easily recognizable interpretation of such cas es where air agencies recommend excluding already collected and reported data. To help illustrate the possible outcomes of how this could work consider the following examples. Example 1: An agency finds that the bias between a collocated PM 2.5 continuous F EM and FRM are acceptable, but near the limit of that acceptability and then finds a year later that the assessment indicates that the bias is just outside the limit of that acceptability. Such relatively small changes where an assessment indicates flippi ng in or out of the acceptable bias are in themselves acceptable since the overall Data Quality Objectives (DQOs) can still be met. The overall DQOs can still be met since there are a number of other factors that feed into the DQOs such as precision, data completeness, and especially sample frequency, which when operating a continuous FEM is a daily sample. Daily sampling provides less uncertainty than sampling at the one

- in

- three day or one

- in

- six day sampling frequencies, which are routinely employed by f ilter

- based FRM samplers. Therefore, in this example the existing data should still be compared to the NAAQS, but***E.O. 12866 Revie w - Draft Do Not Cite, Quote, or Release During Review***; Monitoring Preamble Update 121212

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Page 41 of 62 the air agency should thoughtfully consider whether to recommend 22 and the EPA will consider whether to approve that any new data from PM 2.5 co ntinuous FEMs are used in comparison to the NAAQS. If an air agency recommends to not use a PM 2.5 continuous FEM for comparison to the NAAQS, it would need to ensure another approved method (i.e, a filter

- based FRM/FEM or other continuous FEM which is per forming within acceptable performance criteria) is operating at the site or sites of interest. This would be expected for all SLAMS, but at a minimum the design value monitoring station for the area of interest would be required to have another approved PM 2.5 method (i.e., an FRM, other filter

- based FEM, or other continuous FEM or ARM with acceptable data comparability) operating on the required sample frequency or more often for that location. Example 2: A PM 2.5 continuous FEM operated by an air agency is found to have a significant bias compared to a collocated FRM. If the air agency finds cause to invalidate the data (e.g., a flow sensor is found to be outside of acceptable limits), then it should invalidate the relevant data (i.e., data from the period g oing back to the last successful flow check or audit or other information that points to a cause that the flow sensor is not meeting its performance criteria) for all data uses and there is no follow

- up issue of retrospective analysis. A case of finding ca use to invalidate data would be based on validation criteria found in an air agencies approved quality assurance project plan (QAPP). Example 3: A PM 2.5 continuous FEM operated by an air agency and previously identified as appropriate to compare to the NAA QS, is found to have a significant and unacceptable bias compared to a collocated FRM and there is no other reason to invalidate the data. That is, all other information points to the data being valid; however, there has been a significant shift in the com parability of the PM 2.5 continuous FEM
22 Through the annual monitoring network plan explained in §58.10.***E.O. 12866 Revie w - Draft Do Not Cite, Quote, or Release During Review***; Monitoring Preamble Update 121212

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Page 42 of 62 compared to a collocated FRM (which itself is found to be operating correctly and data are valid). A significant shift in the comparability would be noticeable by comparing assessments for a site from one year to the next and seeing a significant and unacceptable change in one of the key statistical metrics used in the evaluation (i.e., additive or multiplicative bias). Such a case of retrospectively recommending not using PM 2.5 continuous FEM data should also take int o account all other available information that can help inform approving such a recommendation as part of an annual monitoring network plan. For example, do data from the PM 2.5 performance evaluation program data also suggest an unacceptable bias for a spe cific period of interest with this method as used in the air agencies network? Note: This type of assessment is often limited by the small number of samples taken in the PEP program relative to the large number of collocated samples expected when an FRM an d PM 2.5 continuous FEM are collocated. In this type of example, the air agency might want to recommend not using the continuous FEM data for comparison to the NAAQS; however, the continuous FEM data could be appropriate for use in reporting the Air Quality Index (AQI) or other data uses either as is or if statistically correlated 23 and corrected back to the collocated FRM. So in this last example, the PM 2.5 continuous FEM data would be stored separately in the EPA’s data system so that they are eligible for use in AQI calculations, but not used in comparison to the NAAQS, if approved by the EPA. Again, the air agency should thoughtfully consider and state its position and rationale in the annual monitoring network plan on whether any future data should be compared to the NAAQS.
23 The EPA has had a long

- standing policy of allowing PM 2.5 continuous data to be statistically correlated and corrected to use in AQI reporting
. A report is available on this : See “ Data Quality Objectives (DQOs) for Relating Federal Reference Method (FRM) and Continuous PM 2.5 Measurements to Report an Air Quality Index (AQI), EPA

- 454/ B

- 02

- 002, November 2002”.***E.O. 12866 Revie w - Draft Do Not Cite, Quote, or Release During Review***; Monitoring Preamble Update 121212

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Page 43 of 62 Another issue to consider is the transparent and consistent use of PM 2.5 continuous FEM data from a method where one air agency recom mends using the data for comparison to the NAAQS and another specifically recommends to not use it for comparison to the NAAQS. The use of the annual monitoring plans ensures that the process is transparent; however, it may not ensure a consistent approach if one agency recommends exclusion of data and another agency does not. For example, consider two adjacent air agencies operating the same make and model of a PM 2.5 continuous FEM, where one air agency recommends using data and the other air agency recomm ends not using it for comparison to the NAAQS. While on its face it may seem straightforward that a method with acceptable comparability to a collocated FRM should perform similarly in other air agency networks where they have similar aerosol composition a nd climate, in practice there are a number of other variables that affect data comparability. Such factors that lead to differences in comparability might include differences in installation, training, development of SOPs, control of shelter conditions, ma intenance of the continuous FEM, and performance of the FRMs which are being used as the basis of comparison to the continuous FEM. Also, there may be cases where the concentration levels are so far away from the level of the NAAQS (either substantially hi gher or lower) that it would not matter if the data are excluded or not, the same NAAQS determination would result. The EPA has considered these issues and in general believes that it would still be acceptable for one agency to use data for comparison to t he NAAQS, while another agency does not, even if it’s the same method used in adjacent air agency networks. On the issue of grouping sites for purposes of allowing monitors that are not***E.O. 12866 Revie w - Draft Do Not Cite, Quote, or Release During Review***; Monitoring Preamble Update 121212

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Page 44 of 62 collocated to be included when recommending a method should not be co mpared to the NAAQS, the EPA believes that it is not necessary to provide specific details on what criteria are necessary to group sites as air agencies are in the best position to determine a recommendation of when such sites should or should not be group ed. However, to illustrate examples of possible ways to group sites, the air agency could take into account factors such as whether the sites are all in either a rural or urban location, since urban locations tend to be impacted more directly by fresh emis sions which are known to be more volatile, or whether there is consistency in the climate for the sites of interest as might be the case for sites near a large water body or at a high altitude. The EPA will consider these issues when evaluating air agency requests for approval. The EPA is finalizing its proposal to allow each air agency to specify its intention to use or not use data from continuous PM 2.5 FEMs that are eligible for comparison to the NAAQS as part of their annual monitoring network plan due to the applicable EPA Region Office by July 1 each year where adequate FRM data are available. The EPA’s approval of an annual monitoring network plan 24 as a whole, or in part, will constitute concurrence with an air agency’s recommendation to use or not us e data from continuous PM 2.5 FEMs as eligible for comparison to the NAAQS , unless otherwise noted in the approval of the plan. The absence of an air agency statement specifying a position on use of data from a continuous PM 2.5 FEM for comparison to the NAA QS will be interpreted as meaning that all such data are applicable for comparison to the NAAQS following the provisions in Part 50, Appendix N on data handling and Part 58 on the monitoring requirements. In finalizing this decision the EPA will ensure, as proposed, that air

24 Approval of an annual monitoring network plan is subject to approval of the EPA Regional Administrator as provided for in §58.10(a)(2).***E.O. 12866 Revie w - Draft Do Not Cite, Quote, or Release During Review***; Monitoring Preamble Update 121212

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Page 45 of 62 agencies can identify already collected data from PM 2.5 continuous FEMs that should not be used for comparison to the NAAQS. After considering comments in support of allowing additional retrospective assessments, the EPA is also finaliz ing an approach of allowing for the continued use of retrospective assessments to inform when already collected data should not be compared to the NAAQS, if there has been a significant change in the assessment of that data from previous years.
c. Revoking P M 10

- 2.5 Speciation Requirements at NCore Sites The EPA propose d to revoke the requirement for PM 10

- 2.5 speciation monitoring as part of the current suite of NCore monitoring requirements
. The requirement to monitor for PM 10

- 2.5 mass (total) at all NCore multi

- pollutant sites remains . PM 10

- 2.5 mass
m onitoring commenced on January 1, 2011 as part of the nationwide startup of the NCore network ( U.S. EPA, 2011a, p. 1

- 15). As part of the process to further define appropriate techniqu es for PM 10

- 2.5 speciation monitoring, a public consultation with the CASAC AAMMS on monitoring issues related to PM 10

- 2.5 speciation was held in February 2009 (74 FR 4196, January 23, 2009) . T he subcommittee noted the lack of consensus on appropriate samp ling and analytical methods for PM 10

- 2.5 speciation and expressed concern that the Agency’s commitment to launch the PM 10

- 2.5 monitoring network without sufficient time to analyze the data from a planned pilot project was premature (Russell, 2009)
. Based o n the noted lack of consensus on PM 10

- 2.5 speciation monitoring techniques, the Agency did implement a small pilot monitoring project to evaluate the available monitoring and analytical technologies
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Page 46 of 62 The EPA pilot monitoring project was completed in 2011, with plans to analyze the data and prepare a final report on findings and recommendations in 201 3. At that time, the EPA will consider what PM 10

- 2.5 speciation sampling techniques, analytical methodologies, and monitoring design strategies would be most a ppropriate as part of a potential nation

- wide monitoring deployment
. Such a deployment could be based on the NCore multi

- pollutant framework or some other strategy that allows flexibility and targets measurements in areas with higher levels of coarse parti cles
. All comments received from air agencies and multi

- state organizations were supportive of the removal of the PM 10

- 2.5 speciation requirement. A few industry commenters raised concerns about the availability of PM 10

- 2.5 speciation data for research p urposes. One environmental group opposed revoking the PM 10

- 2.5 speciation requirement and expressed the need for PM 10

- 2.5 data to support health effects research and future regulatory efforts. The EPA has considered the comments from air agencies that wer e all supportive of revoking the requirement, as well as the industry and environmental groups concerns that PM 10

- 2.5 speciation data will not be available for research. In considering these comments, the EPA recognizes the importance of efforts to develo p and evaluate speciation monitoring approaches for PM 10

- 2.5 given that t here is relatively little information available on the chemical and biological composition of PM 10

- 2.5 and on the health effects associated with the various components (U.S. EPA, 2009a, section 2.3.4). Without more information on the chemical speciation of PM 10

- 2.5 , the apparent variability in associations with health effects across locations is difficult to characterize (U.S. EPA, 2009a, section 6.5.2.3). However, the EPA believes that until a final report on the***E.O. 12866 Revie w - Draft Do Not Cite, Quote, or Release During Review***; Monitoring Preamble Update 121212

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Page 47 of 62 findings from the pilot study is completed in 2013 and the results of the study can be considered, PM 10

- 2.5 speciation is not ready for nationwide deployment. Therefore, the EPA is finalizing its decision to revoke the PM 1 0

- 2.5 speciation requirement at NCore stations. Given the continued importance of characterizing PM 10

- 2.5 species, and given that ongoing and future research will likely further inform the development of speciation methods, the appropriateness of requiring speciation monitoring for PM 10

- 2.5 will be revisited in future reviews.

d. Measurements for the Proposed New PM 2.5 Visibility Index NAAQS The EPA proposed requirements for sampling of PM 2.5 chemical speciation in states with large C BSAs. However, as explain ed in s ection VI, the EPA is not finalizing the proposed secondary PM 2.5 visibility i ndex NAAQS and therefore is not finalizing the proposed monitoring changes associated with that standard. 4. Revisions to the Quality Assurance Requirements for SLAMS, SPMs, and PSD
a . Quality Assurance Weight of Evidence The EPA propose d to use a weight

- of

- evidence approach for determining whether the quality of data is appropriate for regulatory decision

- making purposes . W hile t he EPA believes that it is essential to require a minimum set of checks and procedures in appendix A to support the successful implementation of a quality system, the success or failure of any one check or series of checks should not preclude the EPA from determining that data are of acceptable quality to be used for regulatory decision

- making purposes . Accordingly, the EPA proposed to include additional wording in appendix A to clarify the role that appendix A generated data quality indicators have in the overall quality system that supports ambient air monitoring activities
.***E.O. 12866 Revie w - Draft Do Not Cite, Quote, or Release During Review***; Monitoring Preamble Update 121212

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Page 48 of 62 The EPA received eight comments on the weight of evidence approach with the majority of commenters endorsing the approach. One commenter felt that the “ paragraph, as written, undermin es the importance of the quality control/quality assurance system dictated in Part 58
. ” Some that supported the approach also provided a word of caution that “ w hile a common sense approach to the assessment of quality data is important, minimum requirement s are necessary to ensure scientifically

- defensible data is being used in decision making”. The EPA agrees with the commenter’s points that data should be subject to a minimum set of requirements for data collection, reporting and quality. In developing th e weight of evidence approach , the EPA is not attempting to diminish the requirements of appendix A but rather ensure that other elements of a quality system that air agencies implement and are documented in their QAPP can also be used when judging whether data are valid for a particular monitoring objective. While the EPA considers the appendix A requirements the minimum for reporting, it is not the only data that the EPA and the air agencies use to judge quality. Therefore , if an appendix A requirement fo r some reason is not complete, the EPA concludes that it should not necessarily be the sole reason to declare the data invalid or unusable. One commenter who felt that the approach may be appropriate also suggested that the language of the proposal was vag ue and may weaken the ability of air monitoring agencies to validate their own data and instead allows the EPA to make decisions regarding data validity. In the majority of cases when the quality of ambient air data is called into question, the EPA Regions and air agencies work together and reach consensus on data usability. The EPA agrees that the air agencies know more about their data and it is the air agencies responsibility to certify the data as valid. In most cases , the EPA and the air agencies will be in agreement on the***E.O. 12866 Revie w - Draft Do Not Cite, Quote, or Release During Review***; Monitoring Preamble Update 121212

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Page 49 of 62 validity and usability of this data. However, since the EPA is responsible for making final regulatory decisions concerning the NAAQS , in rare cases it may ultimately have to make a validity decision that the air agencies may no t agree with. After consideration o f the general support received, the EPA will finalize the language as proposed. For the reasons explained above, the EPA concludes that this will not undermine the quality assurance system, but rather strengthen it. A few commenters, although supporting the weight of evidence approach, also commented that appendix A minimum requirements should not only apply to all air quality data collected by state, local, and tribal agencies, but also to “secondary” data collected by ot her monitoring efforts

. The EPA understands that this term is used by these commenters to either represent the Chemical Speciation and IMPROVE Network data being used to calculate light extinction for the secondary PM 2.5 visibility index NAAQS, or for crit eria pollutant data collected by entities other than the state, local or tribal monitoring organizations. The EPA agrees with the comments that the appendix A requirements must apply to the CSN and IMPROVE data , if the data were being used for comparison t o the secondary NAAQS, and included the term “PM 2.5 CSN” to refer to both networks. However, since as explained in Section VI, the secondary PM 2.5 visibility index NAAQS is not being finalized , the EPA will be removing any text related to the CSN and IMPROVE requirements from appendix A. If the term is being used by commenters to refer to criteria pollutant data collected by entities other than the state, local or tribal monitoring organizations then the appendix A requirements, as has always been the case, apply to those monitors

. b. Quality Assurance Requirements for the Chemical Speciation Network***E.O. 12866 Revie w - Draft Do Not Cite, Quote, or Release During Review***; Monitoring Preamble Update 121212

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Page 50 of 62 The EPA propose d to include requirements for flow rate verifications and flow rate audits for the PM 2.5 CSN. Air agencies currently perform t hese audits even though they are not currently required. Thus , although they w ould be considered a new requirement, they are not new implementation activities. In addition, the CSN already includes six collocated sites which the EPA proposes to include in the 40 CFR part 5 8 appendix A requirements. The EPA propose d that PSD sites would not be required to collocate a second set of instruments for speciated PM 2.5 mass monitoring. There were no comments that specifically addressed the addition of collocation and flow rate requirements in appendix A for the chemical speciation network (CSN) . Since these flow rates have historically been included in the Agencies ’ CSN Network Quality Assurance Project Plan and i mplemented for many years, air agencies may not have considered them any additional burden on the program. However, as explained in Section VI, the secondary PM 2.5 visibility index NAAQS is not being finalized; therefore, the EPA will not include these QA requirements into appendix A since the networks will not produce data to be used for NAAQS decisions.
c. Waivers for Maximum Allowable Separation of Collocated PM 2.5 Samplers and Monitors The EPA proposed to allow waivers, when approved by the EPA Region al Administrator, for collocation of PM 2.5 samplers and monitors of up to 10 meters so long as the site is at a neighborhood s cale or larger. The EPA proposed to allow waivers for the maximum allowable distance associated with collocated PM 2.5 samplers and monitors. Ensuring PM 2.5 continuous FEMs and PM 2.5 FRMs meet collocation requirements (i.e., 1 to 4 meters for PM 2.5 samplers with flow rates of less than 200 liters/minute) can be challenging, since in some cases multiple instruments, FEMs***E.O. 12866 Revie w - Draft Do Not Cite, Quote, or Release During Review***; Monitoring Preamble Update 121212

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Page 51 of 62 installed in t he shelter and FRMs installed on a platform, are being sited at the same station. The EPA believes that instruments spaced farther apart could be maintained within the operational precision of the instruments, especially at sites located at larger scales o f representation (e.g., neighborhood scale and larger). All comments received responded in support of the requirement allowing up to 10 meter horizontal spacing for sites at a neighborhood or larger scale of representation. The EPA received no negative co mments on this part of the proposal . During stakeholder presentations of the proposal, the EPA received a verbal comment that air agencies were also having difficulty meeting the one meter vertical criteria since PM 2.5 FEMs are typically housed in shelters with inlets extending through shelter roofs while the collocated FRM monitors are placed outside, usually on platforms somewhat lower to the ground
. After considering this comment, and further discussion with EPA O ffice of R esearch and Development on spac ing requirements, the agency will amend the appendix A requirements to allow for a 1

- 3 meter vertical spacing which may be approved by the Regional Administrator for sites at a neighborhood or larger scale of representation. In addition, the language will be amended to allow for waiver approvals during annual network plan approval processes. Alternatively, the existing waiver provision outlined in paragraph 10 of Appendix E may be used. 5. Revisions to Probe and Monitoring Path Siting Criteria
a. Near

- road Component to the PM 2.5 Monitoring Network The EPA propose d that the probe and siting criteria for the near

- road component
o f the PM 2.5 monitoring network design follow the same probe and siting criteria as the NO 2 near - road monitoring sites
. These requirements would provide that the monitoring***E.O. 12866 Revie w - Draft Do Not Cite, Quote, or Release During Review***; Monitoring Preamble Update 121212

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Page 52 of 62 probe be sited “...as near as practicable to the outside nearest edge of the traffic lanes of the target road segments; but shall not be located at a distance greater than 50 meters, in the horizontal, fro m the outside nearest edge of the traffic lanes of the target road segment” (section 6.4 of appendix E to 40 CFR part 58)

. The EPA received comments from several stakeholders on the probe and siting criteria for PM 2.5 monitors in the near

- road environment . One public health group offered detailed comments on the probe and siting criteria for PM 2.5 monitors in near

- road environments. While the commenter offered support for collocating the PM 2.5 monitors with NO 2 monitors in the near

- road environment, there was concern expressed regarding allowing monitors at sites of more than 15 meters from the traffic corridor which is the source of the air quality concern. The commenter points out that the EPA’s existing rules for siting localized hot spot sites in areas of highest concentration require sites at microscale locations which provide for a distance of no more than 15 meters from a major roadway. Several air agencies offered consistent comments that the inlet of the PM 2.5 monitors should be the same as that of the near

- roadway NO 2 monitors; however, one of the commenters suggested that the requirements for distance to the nearest vertical wall or obstruction should match the requirements for current micro and middle scale installations of PM 2.5 monitors. The con cern expressed is that a wall or obstruction may disrupt the normal downwind flow across a roadway. In reviewing comments on probe and monitoring path criteria for PM 2.5 monitors in near road environments, and whether to make any changes, the EPA has sev eral issues to consider. One of the most important things to consider is what the intended network design of these monitors should be. As stated in the proposal our goal is to “better***E.O. 12866 Revie w - Draft Do Not Cite, Quote, or Release During Review***; Monitoring Preamble Update 121212

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Page 53 of 62 understand the health impacts of these (near

- road PM 2.5 ) exposures,” th at a number of monitoring objectives can be supported by having near

- road PM 2.5 monitors, and that while it might be that the location of maximum concentration of PM 2.5 exposure from
near - roadway sources might differ from the maximum location of NO 2 or oth er pollutants, we proposed to require that the near

- road PM 2.5 monitors be collocated with the planned NO 2 monitors. The EPA did not propose to change the distance from obstructions for PM 2.5 monitors in its proposal. As we stated in the proposal, the planned NO 2 monitors are using several relevant factors that are also relevant for siting of PM 2.5 (e.g., average annual daily traffic and fleet mix [accounting for heavy duty vehicles] by road segment) and that significant thought and review are going int o the design of the near

- road stations. Therefore, the EPA is not persuaded that we should provide any additional constraints to the siting of the station (i.e., the distance from the roadway) than is already provided for in the NO 2 near - road monitor probe and monitoring path siting criteria. The EPA is concerned that additional constraints (i.e., to require sites within 15 meters of the road), might have some advantages, but also might unnecessarily eliminate otherwise useful near

- road locations that on ba lance might be a better candidate location. The EPA recognizes that there may be cases where the physical location of a
near - road monitoring s tation is farther than 15 meters, but no greater than 50 meters from the roadway, but such cases are presumed to still be the most useful location for the siting of the NO 2 monitors, which we then proposed to collocate with PM 2.5 . Regardless of the actual distance of the inlet for the PM 2.5 monitor at the near

- road monitoring station, so long as it is collocated with the approved near

- road station for NO 2 and meets existing***E.O. 12866 Revie w - Draft Do Not Cite, Quote, or Release During Review***; Monitoring Preamble Update 121212

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Page 54 of 62 criteria, the EPA will consider this site to be appropriate as a near

- road PM 2.5 monitoring station. As explained in the proposal, there are a number of reasons to collect multi

pollutant data in t he near

- road environment. The EPA believes that these sites will be sufficient as representative maximum concentration sites for NO 2 and PM 2.5 in the near

road environment. As noted above, where an air agency believes a different location is a more approp riate site for a near

- road PM 2.5 monitor, the EPA can use its discretion in approving a deviation from the PM 2.5 monitoring requirements as already exists in the network design criteria. A deviation would be appropriate for consideration where, for exampl e, a state provides quantitative evidence de monstrating that peak ambient PM 2.5 concentrations would occur in a near

- road location which meets siting criteria but is not a
near - road NO 2 monitoring site . Such deviations are to be approved by the Regional Administrator as described in section 4.7.1 of Appendix D to part 58. While it is still desirable for the near

- road stations to be as close to the road as practical, there may be differences in the scale of representation of the near

- road PM 2.5 monitor fro m one location to another, while the NO 2 near - road monitors are at the same scale of representation (i.e., micro

- scale) in different locations. This is a result of the scale of representation being based on the pollutant at a location and not the location alone. Therefore, in cases where the station is 20 meters from a major road, the NO 2 measurement may still be micro

- scale, while the PM 2.5 measurement would be middle

scale if the average daily traffic count were sufficiently large enough. 25 If a site with both measurements were 10 meters from a major road they would both be expected to be micro

- scale sites.

25 See Table E

- 1 in Appendix E to Part 58 for defining the scale of representation of a PM sa mpler based on its distance to the nearest traffic lane and average daily traffic count.***E.O. 12866 Revie w - Draft Do Not Cite, Quote, or Release During Review***; Monitoring Preamble Update 121212

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Page 55 of 62 In considering the comment on distance from obstructions, the EPA notes that a monitoring station with multiple measurements is effectively considered c ollocated for those measurements, even though the actual location of the inlets is slightly different from each other within the station. For example, a gas monitor (e.g., for carbon monoxide) may be pulling ambient air from a manifold with an inlet locate d on one part of a station roof, while a PM monitor is pulling air directly from its inlet located a few meters away on the same roof. The EPA believes it is appropriate and consistent with the public comment above on distance from obstructions to maintain the existing requirements for distance from obstructions on a pollutant by pollutant basis, even if they are different for PM 2.5 and NO 2 monitors that will be at the same station. Air agencies will need to consider these distances from obstructions for e ach pollutant inlet probe (i.e., >1 meter for NO 2 monitors and >2 meters for PM 2.5 monitors) in locating monitors at the station. The EPA is maintaining the existing probe and siting criteria for PM 2.5 monitors; however, we are finalizing the provision that the required near

- road component of the PM 2.5 monitoring network design shall be collocated with a required NO 2 monitor at
near - road monitoring station. These near

- road NO 2 monitoring stations are to be sited “...as near as practicable to the outside nearest edge of the traffic lanes of the target road segments; but shall not be located at a distance greater than 50 meters, in the horizontal, from the outside nearest edge of the traffic lanes of the tar get road segment” (section 6.4 of appendix E to 40 CFR part 58). The EPA is retaining the existing requirement that PM 2.5 inlets, including those at near road stations, must be >2 meters from obstructions. b. CSN Network***E.O. 12866 Revie w - Draft Do Not Cite, Quote, or Release During Review***; Monitoring Preamble Update 121212

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Page 56 of 62 As explained in Section VI, the EPA is not finalizing the proposed secondary standard based on a PM 2.5 visibility index and therefore will not be finalizing probe and siting criteria associated with the use of CSN measurements.
c. Reinsertion of Table E

- 1 to Appendix E The EPA propos ed to reinse rt t able E

- 1 to a ppendix E of 40 CFR p art 58
. T his t able presents the minimum separation distance between roadways and probes or monitoring paths for monitoring neighborhood and urban scale ozone (O 3 ) and oxides of nitrogen (NO, NO 2 , NO x , NO y )
. This table was inadvertently removed during a previous CFR revision process . The only comments received on this topic were supportive of the reinsertion of table E

- 1; therefore, the EPA is finalizing the reinsert ion of this table, unchanged from its prior iteration, back into the CFR
. 6. Additional Ambient Air Monitoring Topics
a. Annual Monitoring Network Plan and Periodic Assessment In October of 2006, the EPA finalized new requirements for each state, or where applicable, local agency to perform and submit to their EPA Regional Offices an Assessment of the Air Quality Surveillance System (40 CFR 58.10)
. This assessment is required every five years
. The first required five year assessments were due to EPA Regional Offices by July 1, 2010
. The assessments are intended to provide a comprehensive look at each monitoring agenc y’ s ambient air monitoring network to ensure that the network is meeting the minimum monitoring objectives defined in appendix D to 40 CFR part 58, whether new sites are needed, whether existing sites ar e no longer needed and can be terminated, and whether new technologies are appropriate***E.O. 12866 Revie w - Draft Do Not Cite, Quote, or Release During Review***; Monitoring Preamble Update 121212

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Page 57 of 62 for incorporation into the ambient air monitoring network. 26 Since each agency has completed its first required five

- year assessment, and several monitoring rule requirem ents have either been added or changed since this requirement was added in 2006, the EPA th ought it wa s appropriate to review this requirement and solicit comment on any possible changes the EPA should consider that may improve the usefulness of the assess ments
. Specifically, the EPA solicit ed comment on ways to either streamline or add additional criteria for future assessments
. The EPA also propose d to remove references to “community monitoring zones” and “spatial averaging” in the annual monitoring netw ork plans due to EPA Regional Offices by July 1 of each year
. The Agency propose d to remove these references since, as discussed in section VI I .A.2 above, the EPA propos ed to remove all references to the spatial averaging option throughout 40 CFR part 50 a ppendix N
. Consistent with these changes, the EPA also propose d to remove references to community monitoring zones under the annual monitoring network plans described in 40 CFR 58.10
. The EPA received comments from several air agencies on the five year
as sessments. Most comments on the five year assessments focused on the type and usefulness of assessment tools made available to air agencies during the last review. Of specific note were concerns that assessment tools used to evaluate networks on a regional or national basis do not provide the spatial resolution necessary to adequately assess state networks on a scale most useful to air agencies. This is especially true when attempting to evaluate smaller scale monitoring or pollutant gradients associated wi th near

- road and source oriented monitoring. Suggestions for improvement identified the need for the EPA
26 The EPA provides a link to these assessments on EPA’s website at: http://www.epa.gov/ttn/amtic/plans.html
. A detailed description of the requirements for the assessments is described in 40 CFR 58.10.***E.O. 12866 Revie w - Draft Do Not Cite, Quote, or Release During Review***; Monitoring Preamble Update 121212

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Page 58 of 62 to work closely with air agencies early in the next cycle of assessments (due in 2015) so that any tools developed can be of benefit to the questions a ir agencies need to address for their programs. The EPA did not receive any comments on removing references to community monitoring zones specifically as it pertains to their listing in the annual monitoring network plans described in 40 CFR 58.10. 27 The EP A took comment on potential improvements to the five year assessments. All the recommendations received focused on the types of assessments to perform and ensuring that the EPA works closely with air agencies so that assessments will be of benefit to the a ir agencies. No specific recommendations were made to add or remove any of the requirements of the five year assessments and consequently the EPA is not making any changes. The EPA intends to work with air agencies to ensure future tools are as helpful as practible. Consistent with the decision to end the practice of spatial averaging, the EPA is finalizing the removal of language that referenc es “community monitoring zones” and “spatial averaging” in the annual monitoring network plans due to EPA Regional Offices by July 1 of each year
. b. Operating Schedules The EPA generally requires PM 2.5 SLAMS to operate on at least a 1

- day

- in

- 3 sampling schedule, unless a reduced sampling frequency is approved such as might be the case with a site that has a collocated continuous operating PM 2.5 monitor. 28 However, in the 2006 monitoring rule amendments, the EPA finalized a new requirement for the

27 Comments on the substantive question of whether to revoke references to community monitoring zones were addressed in section VIII.B.1
. 28 All NCore stations must op erate on at least a one

- in

- three day sample frequency for filter

- based PM sampling.***E.O. 12866 Revie w - Draft Do Not Cite, Quote, or Release During Review***; Monitoring Preamble Update 121212

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Page 59 of 62 operating schedule of PM 2.5 SLAMS sites (40 CFR 58.12)
. The new requirement stated that sites with a design value within plus or minus five percent of the 24

- hour PM 2.5 NAAQS must have an FRM or FEM operating on a daily sampling schedule
. This requirement was included to minimize any statistical error associated with the form of the 24

- hour PM 2.5 NAAQS (i.e., the 98 th percentile)
. In section II I .F, the Administrator is finalizing revisions to the level of the primary annual PM 2.5 NAAQS
. Accordingly, possible changes to sampling frequency requirements were also considered
. The EPA had previously considered how sample frequency aff ects the Data Quality Objectives in a consultation with the CASAC AAMMS in September of 2005 (70 FR 51353 to 51354, August 30, 2005)
. As a result of that consultation, the EPA proposed (71 FR 2710 to 2808, January 17, 2006) and finalized (71 FR 61236 to 61 328, October 17, 2006) changes to the sample frequency requirements as part of the monitoring rule changes in 2006
. In that work, the EPA demonstrated that having a higher sample count is generally more useful to minimize uncertainty for a percentile stand ard than an annual average . Given the decision to strengthen the primary annual PM 2.5 NAAQS and the known burden of performing daily sampling using the filter

- based samplers that are still a mainstay in monitoring agency networks, the issue of needing dail y sampling for sites that have design values close to the level of the 24

- hour PM 2.5 standard was reconsidered if the site already has a design value above the level of the primary annual PM 2.5 NAAQS
. In a related issue, since the EPA finalized the requir ement for daily sampling at sites within 5 percent of the 24

- hour PM 2.5 NAAQS in 2006, there has been confusion over the procedures for adjusting sample frequencies, where necessary, to account for***E.O. 12866 Revie w - Draft Do Not Cite, Quote, or Release During Review***; Monitoring Preamble Update 121212

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Page 60 of 62 variations in year

- to
- year design values
. Therefore, the E PA propose d to revise this requirement in the following ways: (1) The EPA propose d that monitors would only be required to operate on a daily schedule if their 24

- hour design values we re within five percent of the 24

- hour PM 2.5 NAAQS and the site ha d a des ign value that wa s not above the level of the annual PM 2.5 NAAQS
. (2) The EPA propose d that review of data for purposes of determining applicability of this requirement at a minimum be included in each agency’s annual monitoring network plan described in 4 0 CFR 58.10 based on the three most recent years of ambient data that were certified as of the May 1 annual deadline
. However, monitoring agencies may request changes to sample frequency at any time of the year by submitting such a request to their applica ble EPA Regional Office
. Changes in sampling frequency are expected to take place by January 1 of the following year . Increased sampling is expected to be conducted for at least three years, unless a reduction in sampling frequency has been approved in a subsequent annual monitoring network plan or otherwise approved by the Regional Administrator
. Comments received on the sample frequency requirements for PM 2.5 were from air agencies, who were generally supportive of the EPA’s proposed approach. The EPA i s finalizing its proposal to modify the sample frequency requirements for triggering daily sampling so that only those areas with 24

- hour design values within five percent of the 24

- hour PM 2.5 NAAQS and where the design value site is not above the level of the annual PM 2.5 NAAQS would be required to operate on a daily sample frequency. The EPA is also finalizing all other aspects of this part of the proposal.
c. Data Reporting and Certification for CSN and IMPROVE Data***E.O. 12866 Revie w - Draft Do Not Cite, Quote, or Release During Review***; Monitoring Preamble Update 121212

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Page 61 of 62 The EPA is not finalizing its proposal on minor changes to reporting and certification of data associated with CSN and IMPROVE networks since as explained in Section VI, EPA is not finalizing a secondary standard to support visibility impairment that would have used CSN and IMPROVE data. d. Requirem ents for Archiving Filters The EPA propose d to extend the requirement for archival of PM 2.5 , PM 10 , and PM 10

- 2.5 filters from manual low

- volume samplers (samplers with a flow rate of less than 200 liters/minute) at SLAMS from one year after data collection to five years after data collection
. The archive of low

- volume PM filters is an important resource for on

- going research and development of emission control strategies and for use in health and epidemiology research
. During a workshop on Ambient Air Qualit y Monitoring and Health Research in 2008, retaining filters for laboratory analysis was identified as a key recommendation to provide daily measurements of metals and elements ( U.S. EPA, 2008d, pp. 17 to 21) . The EPA’s previous requirement of one

- year is n ot sufficiently long for retrospective analysis of important episodes and for use in long

- term epidemiology research
. Since initially requiring filter archival of low

- volume PM filters in 1997, the EPA has always recommended longer archiving of filters and most agencies are already doing so
. However, a small number of agencies have reported discarding older filters, despite the minimal cost of storing these filters. Since cold storage of a large number of filters may be cost prohibitive and of little benefi t in retaining key aerosol species in the

x - ray fluorescence (XRF) analyses, the EPA proposed to minimize the costs of retaining filters by only requiring cold storage during the first year after sample collection
. All comments received on this issue were from air agencies, which were largely***E.O. 12866 Revie w - Draft Do Not Cite, Quote, or Release During Review***; Monitoring Preamble Update 121212

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Page 62 of 62 supportive of such a change to this requirement. One air agency did report that it would present a hardship to store filters for such a long period of time as they did not have the room to support such a requirement. The EPA is finalizing the requirement for archival of PM 2.5 , PM 10 , and PM 10

- 2.5 filters from manual low

- volume samplers (samplers with a flow rate of less than 200 liters/minute) at SLAMS for a minimum of five years after data collection , with cold storage only required for the first 12 months of archiving . EPA will work closely with air agencies through its EPA Regional Offices and laboratories to support any air agency unable to store filters for the new five year requirement.