**UNITED STATES ENVIRONMENTAL PROTECTION AGENCY REGION III**  **1650 Arch Street Philadelphia, Pennsylvania 19103**  **DATE:** May

7 , 201 2 **SUBJECT:** Technical Support Document for Notice of Proposed Rulemaking

– Approval and

Promulgation of Air Quality Implementation Plans; Pennsylvania; Pittsburgh Beaver Valley Nonattainment Area Determinations of Attainment of the 1997 Annual Fine Particulate Standard **FROM:** Emly

n Vélez - Rosa , Environmental Engineer \s \ Office of Air Program Pl anning Lo retta Hayden , Environmental Engineer \s \ Office of Air Monitoring and Analysis **TO:** File **THRU:** Donna Mastro, Acting Associate Director \s \

Office of Air Program Planning **I . BACKGROUND**  On July 18, 1997, EPA e stablished an annual PM 2.5 NAAQS at 15.0 micrograms p er cubic meter (μg/m 3 ) (hereafter referred to as “the annual PM 2.5 NAAQS” or “the annual standard”) , based on a 3 - ye ar average of annual mean PM 2.5 concentrations (62 FR 36852) . At that time, EPA also established a 24 - hour standard of 65 μg/m 3

. See 40 CF R 50.7. T he 1997 PM 2.5 standards were based on significant evidence and numerous health studies demonstrating that serious health effects are associated with exposures to particulate matter. ( Today ’s action does not address the 24 - hour standard.) The p rocess for designating areas following promulgation of a new or revised NAAQS is contained in 107(d)(1) of the Clean Air Act (CAA). On January 5, 2005, EPA published its air quality designations and classifications for the 1997 PM 2.5 NAAQS based upon air quality monitoring data from those monitors for calendar years 2001 - 2003 (70 FR 944). These designations became effective on April 5 , 20 05. The Pittsburgh - Beaver Valley, Pennsylvania area was designated nonattainment for the 1997 annual PM 2.5 NAAQS durin g this designations process. The Pittsburgh - Beaver Valley PM 2.5 nonattainment area (hereafter referred to as “the Pittsburgh Area” or “the Area”) is comprised of the counties of Beaver, Butler, W ashington, and We stmoreland in their entireties, and portions of Allegheny , Armstrong, Greene, and Lawrence Counties. See 40 CFR 81.339 (Pennsylvania) .2

On October 17, 2006, EPA retained the 1997 annual PM 2.5 NAAQS at 15.0 μg/m 3 based on a 3 - ye ar average of annual mean PM 2.5 concentrations, and promulgated a new 24 - hour standard of 35 μg/m 3 (the “ 2006 24 - hour standard”) based on a 3 - ye ar average of the 98th percentile of 24 - hour concentrations (71 FR 61144). On November 13, 2009, EPA designated the Pittsburgh Area as non attainment for the 2006 24 - hour standard (74 FR 58688). Inthat action, EPA also clarified the designations for the PM 2.5 NAAQS promulgated in 1997 stating that the Pittsburgh Area was attainment for the 1997 24 - hour standard. Today ’s action, however, does not address either the 1997 or the 2006 24 - hour standard. Inresponse to legal challenges of the annual standard s promulgated in 2006, the U.S. Court of Appeals for the District of Columbia Circuit (D.C. Circuit) remanded this standard to EPA for further consideration. See American Farm Bureau F ederation and National Pork Producers Council, et al. v. EPA, 559 F.3d 512 (D.C. Cir. 2009). However, given that the 1997 and 2006 annual standards are essentially identical, attainment of the 1997 annual standard would also indicate attainment of the rem anded 2006 annual standard. On April 25, 2007, EPA promulgated its PM 2.5 implementation rule, codified at 40 CFR part 51, subpart Z, in which EPA provided guidance for state and tribal plans to implement the 1997 PM 2.5 standard (72 FR 20664) . This rule , at 40 CFR 51.1004(c), specifies some of the regulatory consequences of attaining the standard, as discussed later . **II. EPA REQUIREMENTS**  **A. PM**  **2.5 Attainment Requirements**  The annual PM 2.5 nonattainment designations triggered the C AA’s requirements under 172(c), which require the submission of an attainment plan for each designated nonattainment area. EPA’s 1997 PM 2.5 implementation rule , specifies that states must submit attainment plans for their nonattainment areas to EPA by no later than three ye ars from the effective date of designation, that is, by

April 5, 2008. EPA’s PM 2.5 implementation rule outlines the SIP requirements for the attainment plan, which includes among other things, the submission of an attainment demonstration showing the air quality improvements expected to result from national and local control measures, an analysis of reasonably available control measures (RACM), including all reasonably

available control technology (RACT), reasonable further progress (RFP) plan, and conting ency

measures. EPA’s implementation rule also sets the attainment date in these areas as April 5, 2010, and the determination would be based on data from 2007 - 2009 (72 FR 20600). The Commonwealth of Pennsylvania is subject to these requirements since it contains several area s designated as nonattainment for the 1997 PM 2.5 NAAQS.3

**B. Monitoring Data**  Under EPA regulations at 40 CFR 50.7, the annual primary and secondary

PM 2.5 standards are met if, over a consecutive three year period, the annual arithmetic mean concentration is less than or equal to 15.0 ug/m 3 , as determ ined in accordance with 40 CFR part 50, appendix N. Data handling conventions and computations necessary for determining whether areas have met the PM 2.5 NAAQS, including requirements for data completeness, are listed in 40 CFR part 50 , appendix N . T he annual arithmetic mean at a monitoring site is to be calculated by averaging the four quarterly arithmetic mean concentrations observed during a calendar year at the site. Generally, the annual mean concentration averaged over three years must be less than 15.0 μg/m3 at all monitoring sites. Three years of valid annual means are required to produce a valid annual standard design value (DV) . For a single monitoring site, a ye ar meets data completeness requirements when at least 75 percent of the scheduled sampling days for each quart er of a site have valid data . As an exception, data from a year with high values not meeting the completeness requirements must be included for calculatin g the annual mean, according to 40 CFR part 58, appendix N. Specifically, for the 1997 annual PM 2.5 NAAQS, the data reflecting high values with less than 75% but at least 11 samples per quarter must be included in the calculation if the resulting annual m ean exceeds the standard. The use of less than complete data is subject to the approval of EPA, which may consider factors such as monitoring site closures/moves, monitoring diligence, and nearby concentrations in determining whether to use such data . Data that does not meet this completeness requirement is analy zed by EPA with substitution of conservative values to determine that some sites not meeting capture rates are still sufficient to show attainment. For comparing to the annual PM 2.5 NAAQS, o nly complete quality- assured, quality- controlled, and certified PM 2.5 d ata from Federal Reference Method (FRM), Federal Equivalent Method (FEM), or Approved Regional Method (ARM ) monitors submitted to EPA's Air Quality System (AQS) can be used in the DV calcu lations . Additionally, PM 2.5 data must be collected from monitoring sites that are eligible for making comparisons with the annual form of the PM 2.5 NAAQS, as set forth in 40 CFR 58.30 . **C. Monitoring Network**  An adequate monitoring network for PM 2.5 sh ould satisfy the specific minimum criteria for establishing state and local air monitoring stations for PM 2.5 data collection , as described in 40 CFR part 58, Appendix D , section 4.7. The minimum ambient air quality monitoring network requirements, used b y EPA to provide support to the SIPs, national air quality assessments, and policy decisions, include the minimum numbers and placement of monitors of each ty pe. T he pollut ant - specific monitoring network s are designed based on the statistical - based defini tions for metropolitan areas provided by the Office of Management and Budget and the Census Bureau, as well as their own political boundaries and geographical characteristics. Additionally, the4

monitoring network in place should be consistent with the mos t recent annual monitoring network plan submitted by the State or local agency and approved by

EPA . See 40 CFR 58.10 . For the Pittsburgh Area, the PM 2.5 monitoring network is located within the Pittsburgh Metropolitan Statistical Area (hereby “the Pittsb urgh MSA”), which includes the counties of Allegheny, Armstrong, Beaver, Butler, Fayette, Washington, and Westmoreland. For the annual PM 2.5 attainment determination of the Pittsburgh Area, the monitoring sites used for comparing with the annual PM 2.5 NAA QS must be located within the Pittsburgh Area and meet all the applicable data and monitoring requirements of 40 CFR part 50 and 40 CFR part 58 . **D. Determination of Attainment**  Upon a determination by

EPA that an area designated nonattainment for the annual PM 2.5 NAAQS has attained the standard, the requirements for such area to submit attainment demonstrations and associated RACM , including all RACT , RFP plan , contingency measures, and other planning SIPs related to attainment of the 1997 annual PM 2.5 NAAQS shall be suspended until such time as: the area is redesignated to attainment, at which time the requirements no longer apply ; or EPA determines that the area has violated the annual PM 2.5 NAAQS , at which time the area is again required to submit such plans. See 40 CFR 51.1004(c). Additionally, EPA will have met its statutory obligation pursuant to 179(c)(1) of the CAA to make a determination based on the area’s air quality data as of the attainment date whether the area attained the standard by that date. A determination of attainment does not shield an area from other required actions such as New Source Review (NSR), conformity and emission inventory

requirements, and provisions to address pollution transport, which would require emission reductio ns at sources or other ty pes of emission activities contributing significantly to nonattainment in other areas or states, or interfering with maintenance in those areas. Determinations as to whether individual areas have attained the NAAQS , and thus quali fy for the application of a determination of attainment , are being made in the context of rulemakings for individual areas. This Technical Support Document (TSD) provides an explanation of EPA’s analysis used to determine whether the Pittsburgh Area has attained the 1997 annual PM 2.5 NAAQS and whether the Area attained the standard by

the applicable attainment date. **III .**  **EPA’S EVALUATION OF AI**  **R QUALITY MONITORING DATA**  **A. Monitoring Network** EPA has determined that the PM 2.5 monitoring network for the Pittsburgh Area is adequate. First, the number of monitors in the Area meets the minimum regulatory requirements given in 40 CFR 58, appendix D. Second, the monitoring is in accordance with the monitoring plans that have been reviewed and approved by EPA.5

During the periods of 2007 - 2009 and 2008 - 2010, the Pittsburgh Area ha d in place a total of 10 PM 2.5 monitoring sites , wh ose data wa s eligible for comparison to the annual PM 2.5 NAA QS , in accordance with the monitorin g requirements of 40 CFR 50.38 . Two of these monitoring sites, 42 - 003 - 0093 (North Park) and 42 - 003 - 0095 (Moon) , did not collect complete PM 2.5 data during the monitoring periods, since both sites were temporarily shutdown on January , 2008 , as a result of monitorin g network reductions in Allegheny County ’s Air Quality Program. On January 2009, the two monitoring sites were reactivated after sufficient resources were acquired. However, in 2010 , Pennsylvania requested to shut down monitoring site 42 - 003 - 0095 (Moon) , on the basis that it wa s statistically insignificant and redundant. See “ Allegheny County ’s 2010 Five Year Monitoring Assessment , ” and “Pennsylvania’s 2010 Annual Network Plan .” On January , 2011 , after EPA’s approval, site 42 - 003 - 0095 was permanently shut down. See Appendix C . Additionally, the monitoring site ID 42 - 005 - 0001 ( Kittaning ) , located i n Armstrong County , did not collect sufficient data during the monitoring periods of 2007 - 2009 and 2008 - 2010. The monitor at site ID 42 - 005 - 0001 , installed to replace a non - federal reference method monitor operating at the site, commenced operation on July 1, 2009 . T hus , air quality data from site ID 42 - 005 - 0001 was not considered in this determination. EPA’s evaluation of the data used for this determination is provided in section s B and C . **B .**  **Air Quality Monitoring Data 2007**  **- 2009**  Inorder to determine that the Pittsburgh Area attained the annual 1997 PM 2.5 NAAQS by its attainment date of April 5, 2010, quality- assured, quality- controlled and state certified ambient air monitoring data for the 2007 - 2009 period was reviewed . The PM 2.5 monitoring data was measured by FRM, FEM, or ARM monitors, as d escribed in 40 CFR part 50 , appendix N . The 2007 - 20 09 monitoring data for the Pittsburgh Area is provided in Table 1 . See Appendix A. While most of the monitoring data satisfy the data completeness requirement, m onitoring sites ID 42 - 003 - 0093 (North Park) and ID 42 - 003 - 0095 (Moon) have missing data for the year 2008. To determine if the two monitors are in attainment with the annual PM 2.5 NAAQS during the monitoring periods 2007 - 2009 and 2008 - 2010 , EPA has addressed the missing data by applying a recently developed statistical procedure. A detailed explanation is provided in section D . **Table 1 .**  **Pittsburgh Area 2007**  **- 2009 PM**  **2.5 Da**  **ta (in**  **μg/m 3**  **) C**  **ounty Si**  **t e ID**  **Site Name 2007**  **Annual Mean**  **2008**

**Annual Mean**  **2009**

**Annual Mean**  **200 7**  **- 200**  **9**

**Design Value**  Allegheny 42 - 003 - 0067 South Fayette 13.5 10.8 10.8 11.7 Allegheny 42 - 003 - 0093 North Park 13.0 * 9.6 11.36

Allegheny 42 - 003 - 0095 Moon 13.6 * 9.4 11.5 Allegheny 42 - 003 - 1008 Harrison 15.1 13.4 12.7 13.7 Allegheny 42 - 003 - 1301 North Braddock 16.6 14.1 12.1 14.3 Beaver 42 - 007 - 0014 Beaver Falls 15.9 13.7 13.0 14.2 Washington 42 - 125 - 0005 Charleroi 15.6 13.0 12.6 13.7 Washington 42 - 125 - 0200 Wash ington 14.8 12.3 11.1 12.7 Washington 42 - 125 - 5001 Florence 13.8 11.3 12.2 12.4 Westmoreland 42 - 129 - 0008 Greensburg 15.3 12.7 13.5 13.8 * Incomplete data EPA has reviewed the ambient air monitoring data for PM 2.5 , consistent with the requirements cont ained in 40 CFR part 50 and recorded in the EPA ’s AQS database for the Pittsburgh Area from 2007 - 2009. The DV for each monitor wa s calculated as the 3 - ye ar average of annual mean PM 2.5 concentrations at the monitor, and was compared to the 1997 PM 2.5 annu al NAAQS. T he DV for the Pittsburgh Area is the highest 3 - ye ar average of the annual means measured at all the monitors in the Area during this time, which meet s the criteria to be used for comparison to the annual PM 2.5 NAAQ S. As shown in Table 1, the D V for the Pittsburgh Area for 2007 - 2009 is 14.3 ug/m 3 , based on the data recorded at the North Braddock monitor. Since the DV of the Pittsburgh Area is below the level of the annual PM 2.5 NAAQS , 15.0 ug/m 3 , the Area attained the annual PM 2.5 NAAQS by

its applicable attainment date based on quality- assured and state certified data . **C .**  **Air Quality Monitoring Data**  **2008 -**  **2010 and Preliminary Data for 2011**  Inorder to demonstrate that the Pittsburgh Area is attaining the annual 1997 PM 2.5 NAAQS and has clean data f

or purposes of 40 CFR 51 .1004(c), air quality data from EPA’s AQS from calendar years 2008 - 2010 and preliminary data for year 2011 w ere reviewed. EPA’s determination that the Pittsburgh Area attains the annual 1997 PM 2.5 NAAQS is based upon the qu ality- assured, quality- controlled and state certified ambient air monitoring data for the 2008 - 2010 period, as measured by FRM, FEM , or ARM monitors described in 40 CFR p art 50 a ppendix N. The 2008 - 2010 design values of the primary monitors used to determ ine attainment of the Pittsburgh Area are listed in Table 2 . As explained previously, m issing data for 2008 at sites ID 42 - 003 - 0093 and ID 42 - 003 - 0095 has be en addressed to determine whether the annual PM 2.5 NAAQS has been attained for the monitors . The statistical procedures and the conclusion of attainment of these two monitors are provided in section D . The 2011 preliminary data, which is incomplete and has not yet been quality- assured or certified, is provided in Table 3. See Appendix A.7

**Table 2**  **. Pittsburgh**  **Area 2008 -**  **2010 PM**  **2.5 Data**  **( in**  **μg/m 3**  **) C**  **ounty Si**  **t e ID**  **Site Name 2008**  **Annual Mean**  **2009**

**Annual Mean**  **2010 Annual**  **Mean 200**  **8 -**  **2010**

**Design Value**  Allegheny 42 - 003 - 0067 South Fayette 10.8 10.8 11.7 11 .1 Allegheny 42 - 003 - 0093 North Park * 9.6 10.5 10.1 Allegheny 42 - 003 - 0095 Moon * 9.4 11.5 10.5 Allegheny 42 - 003 - 1008 Harrison 13.4 12.7 13.0 13.0 Allegheny 42 - 003 - 1301 North Braddock 14.1 12.1 13.7 13.3 Beaver 42 - 007 - 0014 Beaver Falls 13.7 13.0 13.2 13.1 Washington 42 - 125 - 0005 Charleroi 13.0 12.6 12.5 12.9 Washington 42 - 125 - 0200 Washington 12.3 11.1 12.1 11.8 Washington 42 - 125 - 5001 Florence 11.3 12.2 8.9 10.8 Westmoreland 42 - 129 - 0008 Greensburg 12.7 13.5 14.0 13.4 * Incomplete data EPA has reviewed the ambient air monitoring data for PM 2.5 , cons istent with the requirements contained in 40 CFR part 50 and recorded in the EPA’s AQS database for the Pittsburgh Area from 200 8 - 20 10 . The highest DV for the most recent 3 years, 2008 - 2010, for the Pittsburgh Area is 13.4 ug/m 3 , based on the data collect ed at the Greensburg site. The resulting DV for the Area is an average concentration well below the annual standard 15.0 ug/m 3 ; therefore, the Pittsburgh Area is attaining the annual PM 2.5 NAAQS , based on the most recent complete, quality- assured and stat e certified data available . Additionally, preliminary data available to date for 2011 , when considered in conjunction with data from monitoring periods 2007 - 2009 and 2008 - 2010 , indicate that the Pittsburgh Area continues to attain the standard. **Table 3**  **. Pittsburgh**  **Area 2011**  **Preliminary PM**  **2.5 Data**  **(in μg/m**  **3 )**  **C ounty**  **Site ID Site Name**  **2 011**  **Annual Mean**  Allegheny 42 - 003 - 0067 South Fayette 10.6 Allegheny 42 - 003 - 0093 North Park 9.0* Allegheny 42 - 003 - 0095 Moon ** Allegheny 42 - 003 - 1008 Harrison 11.6* Alle gheny 42 - 003 - 1301 North Braddock 12.3* Beaver 42 - 007 - 0014 Beaver Falls 11.7 Washington 42 - 125 - 0005 Charleroi 12.0* Washington 42 - 125 - 0200 Washington 10.8 Washington 42 - 125 - 5001 Florence 5.9 Westmoreland 42 - 129 - 0008 Greensburg 13.7* * Incomplete data8

** No data available, since the monitor’s removal in January 1, 2011. **D .**  **Data Completeness Issues for Monitoring Periods 2007**  **- 2009 and 2008**  **- 2010**  Sites 42 - 003 - 0093 (North Park) and 42 - 003 - 0095 (Moon) have the only monitors in the Pittsburgh Area without a valid attaining annual PM 2.5 design value for the monitoring periods of 2007 - 2009 and 2008 - 2010 due to incomplete data in 2008 . Air quality data recorded at the two monitors have never showed a violating annual PM 2.5 design value, but were incomplete in 2008 due their temporary

shutdown . Inorder to determine whether the annual PM 2.5 NAAQS has been attained for the North Park and Moon monitors, EPA has applied a recently developed statistical procedure to address the missing data, and determine d predicted DVs for the monitor s for the annual PM 2.5 NAAQS for 2007 - 2009 and 2008 - 2010. **1. Method**  **Description** The general concept of the statistical method used is to determine whether an incomplete monitor (target monitor) would have met the annual PM 2.5 NAAQS by replacing the missing data of the target monitor with data from another monitor (candidate monitor) located with in or in the vicinity of the nonattainment area. The first step of the statistical method is to establish a linear regression relations hip between the target monitor and the candidate m onitor, and then to use the linear regression to fill in the missing data for the target monitor in any quarter of the three - ye ar period that did not satisfy the 75 percent completeness requirements based o n actual observations. A “diagnostic DV ” for the monitoring period is calculated with the imputed data and then checked with an additional statistical technique, referred as bootstrapping, to verify if the monitor has attained the annual PM 2.5 NAAQS. The diagnostic DV is used to judge whether these locations would likely have monitored attainment of the annual PM 2.5 NAAQS had the monitors collected complete valid data during this time . The candidate monitor is selected based on 3 different aspects. T h e correlation value (R2 ) from the linear regression should indicate a “strong” linear relationship of the PM 2.5 data from the candidate monitor and the target monitor. Then, the mean of the quarterly data captured (expressed in percentage) which provides the average data collection rate at each site, should determine that the site has sufficient data during the missing period of the target monitor. Additionally, pairing the site data assists in establishing more precise comparisons with fewer observations . T he PM 2.5 monitoring network within the Pittsburgh MSA has 1 2 PM 2.5 monitoring locations which provide an ample number of monitors to compare to the target monitor. The target monitors in this analysis are the North Park and Moon monitors. The methodo logy is used to appropriately

fill in the missing data of 2008 for these two monitors, to judge whether each monitoring location would likely have monitored attainment of the annual PM 2.5 NAAQS had the monitor collected complete valid data during this time . The candidate monitor selected,9

Lawrenceville, AQS ID: 420030008 , has complete data for 2 007 - 2009 and 2008 - 201 0 . **2. Eligibility**  EPA established criteria to assure that the diagnostic annual DV for the North Park and Moon monitor s for each monitoring period , as estimated by the method, was robust enough to allow consideration of the results in a weight of evidence decision. EPA established criteria for both the operating period of the c andidate monitor , L awrence, and for the number of days of samples that the c andidate monitor and each of the target monitors, North Park and Moon , have in common. EPA has not established bright lines or specific requirements for determining diagnostic DVs for monitors with less than complete data. **Operating Time** Ino rder to establish a significant relationship between the monitors, the candidate monitor must have operated during the monitoring periods of 2007 - 2009 and 2008 - 2010 in the Pittsburgh MSA. The candidate monitor is not required to have complete data in all 12 quarters of each 3 - ye ar period, yet should have collected sufficient observations to fill in the missing days of the target monitor, for the target monitor to satisfy the 75 percent completeness in each quarter. **Paired samples** Pairs of sample data f

or the target monitors and candidate monitors from the most recent 20 - quarter period of operation of the target monitor were used. The “period of operation” of the target monitor was based on the date of the last reported sample from the monitor. The can didate monitor had at least 100 historical sample pairs in common with the target monitor during this period. When there were more than 100 pairs in the 20 - quarter period all available pairs were used. In addition to the 100 pairs over the 20 quarters, c andidate monitors had at least 20 paired days of data in common with the target monitor for each calendar quarter (adding together the number of days in a given calendar quarter [Q1, Q2, Q3, or Q4] across the 20 - quarter period). Several candidate sites me t the eligibility criteria of 100 pairs over the 20 - quarters, and at least 20 paired days of data in common with the target monitors for each calendar quarter. **3. Method for**  **Determining D esign**  **V alues**  The following include s a step - by- step explanation of the methodology used to determine the diagnostic d esi gn values for the t arget monitor s (North Park and Moon). The methodology was repeated for each target monitor for both monitoring periods of 2007 - 2009 and 2008 - 2010. Results are discussed in detail in the following section . **Step 1**

– Organize data and perform linear regression(s) between target monitor and possible candidate monitors.10

All the available paired data within the period limit (see the Eligibility section) was used to develop a linear regression to predict target concentrations from candidate concentrations. A regression was performed for each possible pairing that met the criteria utilized for 100 data points and 20 data points per calendar quarter (across all years) in the most recent 20 quarters for each candidate monitor in the Pittsburgh MSA . **Step 2**

– Select Candidate site The Pittsburgh MSA has a large number of monitors which could have been used as candidate sites. During both time periods , 2007 - 2009 and 2008 - 2010, only one candidate monitor , Lawrenceville , AQS ID 420030008 , was selected for both the North Park and Moon monitors. The follow steps were used to select the candidate monitor : ( 1 ) All possible candidate monitors were placed in order of highest correlation (based o n the highest “R - squared ” of the linear regression) with the t arget monitor . ( 2 ) Using the regression equation relating concentrations at the t arget monitor and the c andidate monitor, estimates of the 24 - hour average concentrations were made at the t arget monitor for all missing scheduled days in the initially incomplete quarter, during the most recent three - ye ar period at the t arget monitor . Estimates were only made for days on which a concentration is available at the c andidate monitor. Estimates were not made for any days in the quarter for which the t arget monitor had 75 percent or m ore complete data initially . The estimates were combined with any reported data at the t arget monitor during the recent 3 - ye ar period , and the data capture rates were computed for the originally incomplete quarter. The computation of these data capture rates was based on the assumption that the required sampling frequency for the t arget monitor was recorded. If the c andidate monitor had a lower sampling frequency than the t arget monitor, some missing scheduled days for the t arget were not substituted for the regression - based estimates. When the c andidate monitor had a lower sampling frequency

than the t arget monitor, the t arget monitor sampling schedule was assumed to be a combination of the t arget and c andidate monitors schedules, weighted by the number of originally present and originally

missing scheduled days at the t arget monitor. ( 3 ) If after performing the process in step 2, the results produce d all 12 quart ers at the t arget monitor having at least 75 percent of scheduled values, the c andidate monitor was selected as the c andidate for the remaining steps. If 75 percent of the scheduled values for the t arget monitor were not obtained, then step 2 was repeated for the next best correlated site. This process was repeated until the t arget monitor had 75 percent of its scheduled values. **Step 3**

– Diagnostic Design Value Computed The three - ye ar diagnostic design values for 2007 - 2009 and 2008 - 2010 were calculated using the actual observations of the t arget monitor and the regression - based estimates of daily concentrations. The diagnostic design value for the North Park and Moon monitors in the Pittsburgh Area were below the annual PM 2.5 NAAQS level of 15.0 ug/m 3

.11

**Step 4**

– Statistical confidence of a design value below the annual PM 2.5 NAAQS The results of Step 3 showed the diagnostic design values for the North Park and Moon monitors in Pittsburgh Area to be below the annual PM 2.5 NAAQS . In order to show that th ere is , at most , a 10 percent probability

that the actual design values (had the North Park and Moon monitors operated more days) were above the annual PM 2.5 NAAQS , further analysis was performed as follows: ( 1 ) Residuals were calculated from the regressi on. ( 2 ) A bootstrap analysis was performed, repeating the regression - based substitution in Step 2 but adding to each estimated 24 - hour value that substitutes for a missing scheduled monitored value a plus or minus residual that has been randomly drawn (w ith replacement) from the pool of regression residuals. This step randomly applies real residuals from the linear regression to the imputed current - period Target values. ( 3 ) Repeat ( 2 ) for a total of 1000 runs. ( 4 ) For each of the 1000 bootstrap tri als, the 3 - ye ar design value was calculated. This will provide a pseudo confidence interval for the partially imputed current - period design value for the t arget. ( 5 ) Since none of the 1000 runs resulted in diagnostic d esign values above the annual PM 2.5 NAAQS , the North Park and Moon monitors were considered to have met the annual PM 2.5 NAAQS . For determining the diagnostic design values for the North Park (AQS ID: 420030093) and Moon (AQS ID: 420030095), Steps 1 and 2 were performed separately for e ach of the monitors as the target monitor and for each annual design value. **4. Statistical Results of**  **North Park (** **AQS ID: 420030093 )**  **and Moon (** **AQS ID: 420030095 )**  **monitors** EPA’s statistical results from the methodology used for determining the diagnostic design values for the North Park and Moon Monitors are provided as attachments to this document, and discussed in this section. See Appendix B - 1, B - 2, B - 3 and B - 4 of this TSD. **2007 -** **2009 Annual Design Value for the North Park Monitor**  Figure 1 shows the 2007 - 2009 annual DVs and d ata c apture rates for each monitoring site in the Pittsburgh MSA. InFigure 1, the t arget monitor , North Park (AQS ID: 42 - 003 - 0093), is listed as Site A1 ; and the candidate site , L awrenceville (AQS ID: 42 - 003 - 0008), is listed as Site B1 . The Lawrenceville monitor had the highest correlation with North Park monitor and met the operating period and paired data eligibility criteria for being a c andidate site. The results of the linear12

regression between the North Park and Lawrenceville monitors for the 2007 - 2009 annual design value are shown in Figure 2 . Estimates for all deficient quarterly data for 2007 - 2009 were made. A fter filling in the missing data, the North Park monitor now ha s all complete data for the monitoring period of 2007 - 2009. Then, a 2007 - 2009 diagnostic annual DV of 11.3  g/m 3 was calculated for the North Park monitor (see Figure 3 ) . The statistical confidence of th is design value was checked using the method outlined in Step 4. None of the 1000 bootstrapping trials resulted in a violating DV, which provides statistical confidence that the North Park monitor is attaining the annual PM 2.5 NAAQS . The results of the 1000 bootstrap trials are provided in Figure 4 . **2007 -** **2009 Annual Design Value for the Moon Moni** **tor** Figure 5 shows the 2007 - 2009 annual DVs and data capture rates for each monitoring site in the Pittsburgh MSA . InFigure 5, the target monitor, Moon (AQS ID: 42 - 003 - 0095 ), is listed as Site A2; and the candidate site, L awrenceville (AQS ID: 42 - 003 - 00 08), is listed as Site B2. The Lawrenceville monitor had the highest correlation with the Moon monitor and met the operating period and paired data eligibility criteria for being a candidate site. The results of the linear regression between the Moon and Lawrenceville monitors for determining the 2007 - 2009 annual DV are shown in Figure 6 . Estimates for the missing data during the 2007 - 2008 time period were made. As a result of filling in the missing data, the Moon monitor now had al l complete data for 2 007 - 2009. Then, a 2007 - 2009 diagnostic annual DV of 11.6  g/m 3 was calculated for the Moon monitor (see Figure 7 ) . The statistical confidence of th is design value was checked using the method outlined in Step 4. The results of the 1000 bootstrap trials are provided in Figure 8. None of the 1000 bootstrapping trials resulted in a violating DV, which provides statistical confidence that the Moon monitor is attaining the annual PM 2.5 NAAQS. **200 8** **- 20** **10 Annual Design Value**  **for the North Park Monitor** Figure 9 shows the 2008 - 2010 annual DVs and data capture rates for each monitoring site in the Pittsburgh MSA. InFigure 9, the target monitor, North Park (AQS ID: 42 - 003 - 0093), is listed as Site A3; and the candidate site, L awrenceville (AQS ID: 42 - 003 - 0008), i s listed as Site B3. The Lawrenceville monitor had the highest correlation with North Park and met the operating period and paired data eligibility criteria for being a c andidate site. The results of the regression between the North Park and Lawrencevill e monitors for the 2008 - 2010 annual DV are shown in Figure 10 . Estimates for the missing data for the 2008 - 2010 time period were made. As a result, the North Park monitor now ha s all complete data for 2008 - 2010. A 2008 - 2010 diagnostic annual design valu e of 10.3  g/m 3 was calculated for the North Park monitor when the missing data was filled in Figure 11 . The statistical confidence of th is design value was checked using the method outlined in Step 4. The results of the 1000 bootstrap trials are provide d in Figure 13 . None of the 1000 bootstrapping trials resulted in a violating DV, which provides statistical confidence that the North Park monitor is attaining the annual PM 2.5 NAAQS. **200 8** **- 20** **10 Annual Design Value**  **for the Moon Monitor**13

Figure 13 shows the 2008 - 2010 annual DVs and data capture rates for each monitoring site in the Pittsburgh MSA . InFigure 13 , the target monitor, Moon (AQS ID: 42 - 003 - 0095 ), is listed as Site A4; and the candidate site, L awrenceville (AQS ID: 42 - 003 - 0008), is listed as S ite B4. The Lawrenceville monitor had the highest correlation with Moon and met the operating period and paired data eligibility

criteria for being a c andidate site. The results of the regression between the Moon and L awrenceville monitors for 2008 - 2010 annual design value are shown in Figure 14 . Estimates for the missing data for the 2008 - 2010 time period were made. As a result , the Moon monitor now ha s all complete data for 2008 - 2010. A 2008 - 2010 diagnostic annual design value of 10.8  g/m 3 was calcu lated for the Moon monitor when the missing data was filled in Figure 15. The statistical confidence of th is design value was checked using the method outlined in Step 4. The results of the 1000 bootstrap trials are provided in Figure 16. None of the 10 00 bootstrapping trials resulted in a violating DV, which provides statistical confidence that the Moon monitor is attaining the annual PM 2.5 NAAQS. **V .**  **RECOMMENDED AGENCY ACTION** Based on quality- assured, quality- controlled, and state certified ambient air monitoring data from 2008 - 2010 from the Pittsburgh Area, EPA is making the determination that the Area attains the annual 1997 PM 2.5 NAAQS. Therefore , EPA is suspending the attainment - related SIP requirements for the annual 1997 PM 2.5 NAAQS pursuant to 40 CFR 51.1004(c). Also, b ased on the quality- assured, quality- controlled, and state certified ambient air monitoring data from 2007 - 2009 for the Pittsburgh Area, EPA is making the determination that the Are a attained the annual 1997 PM 2.5 NAAQS by

its attainment date of April 5, 2010. **Attachments :**  Appendix A: EPA AQS Preliminary Design Value Report (AMP480) dated March 23, 2012 Appendix B - 1: Statistical Results of 2007 - 2009 Annual PM 2.5 Design Value for North Park Monitor (AQS ID: 42 - 003 - 0093)

- F igure 1. Pittsburgh Sites and 2007 - 2009 DVs & Data Capture

- Figure 2. Linear Regression Results

- Figure 3. Imputation and Resulting Data Capture and DV Recalculation

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- Figure 4. Bootstrapping Residuals (and DV Recalculations) Appendix B - 2: Statistical Results of 2007 - 2009 Annual PM 2.5 Design Value for Moon Monitor (AQS ID: 42 - 003 - 0095 )

- Figure 5. Pittsburgh Sites and 2007 - 2009 DVs & Data Capture

- Figure 6. Linear Regression Results

- Figure 7. Imputation and Resulting Data Capture and DV Recalculation

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- Figure 8. Bootstrapping Residuals (and DV Recalculations) Appendix B - 3: Statistical Results of 200 8 - 2010 Annual PM 2.5 Design Value for North Park Monitor (AQS ID: 42 - 003 - 0093)14

- Figure 9. Pittsburgh Sites and 2 008 - 2010 DVs & Data Capture

- Figure 10. Li near Regression Results

- Figure 11. Imputation and Resulting Data Capture and DV Recalculation

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- Figure 12. Bootstrapping Residuals (and DV Recalculations) Appendix B - 4: Statistical Results of 200 8 - 2010 Annual PM 2.5 Design Value for Moon Monitor (AQS ID : 42 - 003 - 0095 )

- Figure 13 . Pittsburgh Sites and 2008 - 2010 DVs & Data Capture

- Figure 14. Linear Regression Results

- Figure 15. Imputation and Resulting Data Capture and DV Recalculation

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- Figure 16. Bootstrapping Residuals (and DV Recalculations) Appendix C: E - mail Correspondence from EPA to ACHD dated 2/19/2008 - Approval of Allegheny

County Air Monitoring Network Reduction Request