UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

REGION III

1650 Arch Street

Philadelphia, Pennsylvania 19103

DATE: May 7, 2012

SUBJECT: Technical Support Document for Notice of Proposed Rulemaking – Approval and 

Promulgation of Air Quality Implementation Plans; Pennsylvania; PittsburghBeaver Valley Nonattainment Area Determinations of Attainment of the 1997 

Annual Fine Particulate Standard

 

FROM: Emlyn Vélez-Rosa, Environmental Engineer \s\

Office of Air Program Planning 

Loretta 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 established an annual PM2.5 NAAQS at 15.0 micrograms per cubic meter 

(μg/m3) (hereafter referred to as “the annual PM2.5 NAAQS” or “the annual standard”), based on 

a 3-year average of annual mean PM2.5 concentrations (62 FR 36852). At that time, EPA also 

established a 24-hour standard of 65 μg/m3. See 40 CFR 50.7. The 1997 PM2.5 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 process 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 PM2.5 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, 2005. The Pittsburgh-Beaver Valley, Pennsylvania 

area was designated nonattainment for the 1997 annual PM2.5 NAAQS during this designations 

process. The Pittsburgh-Beaver Valley PM2.5 nonattainment area (hereafter referred to as “the 

Pittsburgh Area” or “the Area”) is comprised of the counties of Beaver, Butler, Washington, and 

Westmoreland 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 PM2.5 NAAQS at 15.0 μg/m3based on a 3-

year average of annual mean PM2.5 concentrations, and promulgated a new 24-hour standard of 

35 μg/m3(the “2006 24-hour standard”) based on a 3-year average of the 98th percentile of 24-

hour concentrations (71 FR 61144). On November 13, 2009, EPA designated the Pittsburgh 

Area as nonattainment for the 2006 24-hour standard (74 FR 58688). In that action, EPA also 

clarified the designations for the PM2.5 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.

In response to legal challenges of the annual standards 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 Federation 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 remanded 2006 annual standard. 

On April 25, 2007, EPA promulgated its PM2.5 implementation rule, codified at 40 CFR part 51, 

subpart Z, in which EPA provided guidance for state and tribal plans to implement the 1997 

PM2.5 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. PM2.5 Attainment Requirements 

The annual PM2.5 nonattainment designations triggered the CAA’s requirements under 172(c), 

which require the submission of an attainment plan for each designated nonattainment area. 

EPA’s 1997 PM2.5 implementation rule, specifies that states must submit attainment plans for 

their nonattainment areas to EPA by no later than three years from the effective date of 

designation, that is, by April 5, 2008. EPA’s PM2.5 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 contingency 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 areas designated as nonattainment for the 1997 PM2.5 NAAQS. 
3

B. Monitoring Data 

Under EPA regulations at 40 CFR 50.7, the annual primary and secondary PM2.5 standards are 

met if, over a consecutive three year period, the annual arithmetic mean concentration is less than 

or equal to 15.0 ug/m3, as determined in accordance with 40 CFR part 50, appendix N. Data 

handling conventions and computations necessary for determining whether areas have met the 

PM2.5 NAAQS, including requirements for data completeness, are listed in 40 CFR part 50, 

appendix N. 

The 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 year meets data completeness 

requirements when at least 75 percent of the scheduled sampling days for each quarter 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 calculating the annual mean, according to 40 

CFR part 58, appendix N. Specifically, for the 1997 annual PM2.5 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 mean 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 analyzed 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 PM2.5 NAAQS, only complete quality-assured, quality-controlled, 

and certified PM2.5 data 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 calculations. Additionally, PM2.5 data must be collected from 

monitoring sites that are eligible for making comparisons with the annual form of the PM2.5 

NAAQS, as set forth in 40 CFR 58.30.

C. Monitoring Network

An adequate monitoring network for PM2.5 should satisfy the specific minimum criteria for 

establishing state and local air monitoring stations for PM2.5 data collection, as described in 40 

CFR part 58, Appendix D, section 4.7. The minimum ambient air quality monitoring network 

requirements, used by EPA to provide support to the SIPs, national air quality assessments, and 

policy decisions, include the minimum numbers and placement of monitors of each type. The 

pollutant-specific monitoring networks are designed based on the statistical-based definitions 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, the 
4

monitoring network in place should be consistent with the most 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 PM2.5 monitoring network is located within the Pittsburgh 

Metropolitan Statistical Area (hereby “the Pittsburgh MSA”), which includes the counties of

Allegheny, Armstrong, Beaver, Butler, Fayette, Washington, and Westmoreland. For the annual 

PM2.5 attainment determination of the Pittsburgh Area, the monitoring sites used for comparing 

with the annual PM2.5 NAAQS 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 PM2.5

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 PM2.5 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 PM2.5

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 reductions at sources or other types 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 qualify 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 PM2.5 NAAQS and whether the Area attained the 

standard by the applicable attainment date. 

III. EPA’S EVALUATION OF AIR QUALITY MONITORING DATA

A. Monitoring Network 

EPA has determined that the PM2.5 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 had in place a total of 10

PM2.5 monitoring sites, whose data was eligible for comparison to the annual PM2.5 NAAQS, in 

accordance with the monitoring 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 PM2.5 data during 

the monitoring periods, since both sites were temporarily shutdown on January, 2008, as a result 

of monitoring 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 was 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 in 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. Thus, 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 sections B and C.

B. Air Quality Monitoring Data 2007-2009

In order to determine that the Pittsburgh Area attained the annual 1997 PM2.5 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 PM2.5 monitoring data was 

measured by FRM, FEM, or ARM monitors, as described in 40 CFR part 50, appendix N. The 

2007-2009 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, monitoring 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 PM2.5 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 PM2.5 Data (in μg/m3)

County Site ID Site Name

2007 

Annual 

Mean

2008 

Annual 

Mean

2009 

Annual 

Mean

2007 - 2009 

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 11.3
6

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 Washington 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 PM2.5, consistent with the requirements 

contained 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 was calculated as the 3-year average of annual mean 

PM2.5 concentrations at the monitor, and was compared to the 1997 PM2.5 annual NAAQS. The 

DV for the Pittsburgh Area is the highest 3-year average of the annual means measured at all the 

monitors in the Area during this time, which meets the criteria to be used for comparison to the 

annual PM2.5 NAAQS. As shown in Table 1, the DV for the Pittsburgh Area for 2007-2009 is 

14.3 ug/m3, based on the data recorded at the North Braddock monitor. Since the DV of the 

Pittsburgh Area is below the level of the annual PM2.5 NAAQS, 15.0 ug/m3, the Area attained the 

annual PM2.5 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

In order to demonstrate that the Pittsburgh Area is attaining the annual 1997 PM2.5 NAAQS and 

has clean data for 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 were reviewed. EPA’s 

determination that the Pittsburgh Area attains the annual 1997 PM2.5 NAAQS is based upon the 

quality-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 part 50 

appendix N. The 2008-2010 design values of the primary monitors used to determine attainment 

of the Pittsburgh Area are listed in Table 2. As explained previously, missing data for 2008 at

sites ID 42-003-0093 and ID 42-003-0095 has been addressed to determine whether the annual 

PM2.5 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 PM2.5 Data (in μg/m3)

County Site ID Site Name

2008 

Annual 

Mean

2009 

Annual 

Mean

2010 

Annual 

Mean

2008 - 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 PM2.5, consistent with the requirements 

contained in 40 CFR part 50 and recorded in the EPA’s AQS database for the Pittsburgh Area 

from 2008-2010. The highest DV for the most recent 3 years, 2008-2010, for the Pittsburgh Area 

is 13.4 ug/m3, based on the data collected at the Greensburg site. The resulting DV for the Area 

is an average concentration well below the annual standard 15.0 ug/m3; therefore, the Pittsburgh

Area is attaining the annual PM2.5 NAAQS, based on the most recent complete, quality-assured 

and state 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 PM2.5 Data (in μg/m3)

County Site ID Site Name 2011 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*

Allegheny 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 data
8

** 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 PM2.5 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 PM2.5 design value, but were incomplete in 2008

due their temporary shutdown. In order to determine whether the annual PM2.5 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 determined predicted DVs for the monitors

for the annual PM2.5 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 PM2.5 NAAQS by replacing the missing data of the 

target monitor with data from another monitor (candidate monitor) located within or in the 

vicinity of the nonattainment area. The first step of the statistical method is to establish a linear 

regression relationship between the target monitor and the candidate monitor, and then to use the

linear regression to fill in the missing data for the target monitor in any quarter of the three-year 

period that did not satisfy the 75 percent completeness requirements based on 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 PM2.5 NAAQS. The diagnostic DV is used to judge whether 

these locations would likely have monitored attainment of the annual PM2.5 NAAQS had the 

monitors collected complete valid data during this time. 

The candidate monitor is selected based on 3 different aspects. The correlation value (R2) from 

the linear regression should indicate a “strong” linear relationship of the PM2.5 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.

The PM2.5 monitoring network within the Pittsburgh MSA has 12 PM2.5 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 methodology 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 PM2.5 NAAQS had the 

monitor collected complete valid data during this time. The candidate monitor selected, 
9

Lawrenceville, AQS ID: 420030008, has complete data for 2007-2009 and 2008-2010.

2. Eligibility

EPA established criteria to assure that the diagnostic annual DV for the North Park and Moon 

monitors 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 candidate monitor, Lawrence, and for the number of days of samples

that the candidate 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

In order 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-

year 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 for 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 candidate 

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, candidate 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 met 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 Design Values

The following includes a step-by-step explanation of the methodology used to determine the 

diagnostic design values for the target monitors (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 on 

the highest “R-squared” of the linear regression) with the target monitor. 

(2) Using the regression equation relating concentrations at the target monitor and the 

candidate monitor, estimates of the 24-hour average concentrations were made at the target 

monitor for all missing scheduled days in the initially incomplete quarter, during the most recent 

three-year period at the target monitor. Estimates were only made for days on which a 

concentration is available at the candidate monitor. Estimates were not made for any days in the 

quarter for which the target monitor had 75 percent or more complete data initially. The 

estimates were combined with any reported data at the target monitor during the recent 3-year 

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 target monitor was recorded. If the candidate monitor had a lower sampling 

frequency than the target monitor, some missing scheduled days for the target were not 

substituted for the regression-based estimates. When the candidate monitor had a lower 

sampling frequency than the target monitor, the target monitor sampling schedule was assumed 

to be a combination of the target and candidate monitors schedules, weighted by the number of 

originally present and originally missing scheduled days at the target monitor. 

(3) If after performing the process in step 2, the results produced all 12 quarters at the 

target monitor having at least 75 percent of scheduled values, the candidate monitor was selected 

as the candidate for the remaining steps. If 75 percent of the scheduled values for the target 

monitor were not obtained, then step 2 was repeated for the next best correlated site. This 

process was repeated until the target monitor had 75 percent of its scheduled values.

Step 3 – Diagnostic Design Value Computed

The three-year diagnostic design values for 2007- 2009 and 2008-2010 were calculated using the 

actual observations of the target 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 PM2.5 NAAQS level of 15.0 ug/m3.
11

Step 4 – Statistical confidence of a design value below the annual PM2.5 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 PM2.5 NAAQS. In order to show that there 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 PM2.5 NAAQS, further analysis was performed as 

follows:

(1) Residuals were calculated from the regression.

(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 (with 

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 trials, the 3-year design value was calculated. This 

will provide a pseudo confidence interval for the partially imputed current-period design 

value for the target.

(5) Since none of the 1000 runs resulted in diagnostic design values above the annual 

PM2.5 NAAQS, the North Park and Moon monitors were considered to have met the 

annual PM2.5 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 each 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 data capture rates for each monitoring site in the

Pittsburgh MSA. In Figure 1, the target monitor, North Park (AQS ID: 42-003-0093), is listed as 

Site A1; and the candidate site, Lawrenceville (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 candidate site. The results of the linear 
12

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. 

After filling in the missing data, the North Park monitor now has all complete data for the 

monitoring period of 2007-2009. Then, a 2007-2009 diagnostic annual DV of 11.3 g/m3 was 

calculated for the North Park monitor (see Figure 3). The statistical confidence of this 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 PM2.5 NAAQS. The results of the 1000 bootstrap trials are provided in 

Figure 4.

2007-2009 Annual Design Value for the Moon Monitor

Figure 5 shows the 2007-2009 annual DVs and data capture rates for each monitoring site in the

Pittsburgh MSA. In Figure 5, the target monitor, Moon (AQS ID: 42-003-0095), is listed as Site 

A2; and the candidate site, Lawrenceville (AQS ID: 42-003-0008), 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 all complete 

data for 2007-2009. Then, a 2007-2009 diagnostic annual DV of 11.6 g/m3 was calculated for 

the Moon monitor (see Figure 7). The statistical confidence of this 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 PM2.5 NAAQS. 

2008-2010 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. In Figure 9, the target monitor, North Park (AQS ID: 42-003-0093), is listed as 

Site A3; and the candidate site, Lawrenceville (AQS ID: 42-003-0008), is 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 candidate site. The results of the regression 

between the North Park and Lawrenceville 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 has all complete data for 2008-2010. A 2008-2010 diagnostic 

annual design value of 10.3 g/m3 was calculated for the North Park monitor when the missing 

data was filled in Figure 11. The statistical confidence of this design value was checked using 

the method outlined in Step 4. The results of the 1000 bootstrap trials are provided 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 PM2.5 NAAQS. 

2008-2010 Annual Design Value for the Moon Monitor
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Figure 13 shows the 2008-2010 annual DVs and data capture rates for each monitoring site in the 

Pittsburgh MSA. In Figure 13, the target monitor, Moon (AQS ID: 42-003-0095), is listed as 

Site A4; and the candidate site, Lawrenceville (AQS ID: 42-003-0008), is listed as Site B4. The 

Lawrenceville monitor had the highest correlation with Moon and met the operating period and 

paired data eligibility criteria for being a candidate site. The results of the regression between the 

Moon and Lawrenceville 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 has all complete data for 2008-2010. A 2008-2010 diagnostic annual design value 

of 10.8 g/m3 was calculated for the Moon monitor when the missing data was filled in Figure 

15. The statistical confidence of this 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 1000 

bootstrapping trials resulted in a violating DV, which provides statistical confidence that the 

Moon monitor is attaining the annual PM2.5 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 PM2.5 NAAQS. Therefore, EPA is suspending the attainment-related SIP 

requirements for the annual 1997 PM2.5 NAAQS pursuant to 40 CFR 51.1004(c). Also, based 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 Area attained the annual 

1997 PM2.5 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 PM2.5 Design Value for North Park 

Monitor (AQS ID: 42-003-0093)

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

- Figure 2. Linear Regression Results 

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

- -Figure 4. Bootstrapping Residuals (and DV Recalculations)

Appendix B-2: Statistical Results of 2007-2009 Annual PM2.5 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

- -Figure 8. Bootstrapping Residuals (and DV Recalculations)

Appendix B-3: Statistical Results of 2008-2010 Annual PM2.5 Design Value for North Park 

Monitor (AQS ID: 42-003-0093)
14

- Figure 9. Pittsburgh Sites and 2008-2010 DVs & Data Capture

- Figure 10. Linear Regression Results 

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

- -Figure 12. Bootstrapping Residuals (and DV Recalculations)

Appendix B-4: Statistical Results of 2008-2010 Annual PM2.5 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-

- 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