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; Pittsburgh-Beaver 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

er 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).

On October 17, 2006, EPA retained the 1997 annual PM2.5 NAAQS at 15.0
μg/m3 based 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.  

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 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. 

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

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.

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

** 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,
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.

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.

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
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

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)

 

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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)

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 

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