SUBJECT: Technical Support Document Regarding Monitoring Data —Delaware, Maryland,

New Jersey, and Pennsylvania; Determinations of Attainment ofthe 1997 Annual

Fine Particulate Standard for the Philadelphia-Wilmington Nonattainment Area

FROM: äfa enior Air Quality Planning Specialist

OfficeAir Program Planning — /46

Loretta Hden, Environmental Engineer

Office of Air Monitoring & Analysis

TO: F N

(2- 1<Y\ /f///i

THRU: Cristina Fernandez, Associate Director

Office of Air Program Planning

This document provides a technical review ofthe air quality monitoring data used to support the

Environmental Protection Agency’s (EPA’s) proposed determination that the PhiladelphiaWilmington-Atlantic City, PA-NJ-DE annual PM25 nonattainment area (the Philadelphia Area)has attained the 1997 annual PM2.5national ambient air quality standard (NAAQS) by its

statutory attainment date and EPA’s proposed clean data determination for the Philadelphia

Area.

I. BACKGROUND

The Philadelphia Area includes the New Castle County in Delaware; Burlington, Camden, and

Gloucester Counties in New Jersey; and Bucks, Chester, Delaware, Montgomery, and

Philadelphia Counties in Pennsylvania. The attainment date for the 1997 annual PM2.5NAAQS

is April 5, 2010. See 40 CFR 5 1.1004(a).

II. EVALUATION OF AIR QUALITY MONITORING DATA

A. Data Requirements

The criteria for determining if an area is attaining the 1997 annual PM2.5NAAQS are set out in

40 CFR 50.13 and appendix N. The annual PM2.5NAAQS is met when the annual design value

is less than or equal to 15.0 micrograms per cubic meter (jig/m 3). Three years of valid annual
concentrations in determining whether to use such data.

The data must be collected and quality-assured in accordance with 40 CFR part 58, and must be

recorded in EPA’s Air Quality System (AQS). The data supporting attainment of the standard

must be complete in accordance with 40 CFR part 50, appendix N.B. Certified Air Quality Monitoring Data, 2007-2009 and 2008-2010

The States of Delaware, and New Jersey, and the Commonwealth of Pennsylvania (“the States”)submitted quality assured air quality monitoring data into AQS. The States then certified that

data. While most of the monitoring data is complete, several monitors had completeness issues,

as described below in the Data Completeness Issues section. Attached are two AQS reportscontaining annual PM2.5data for the Philadelphia Area for 2007 to 2009 and 2008-20 10. Tables

1 and 2, below, summarizes those reports.

Notes: Max Q = site passed the maximum

C = complete

Inc = incomplete

*

= site started operating in 2008.

Table I 2007-2009 Philadelphia krea Annual PM2.çDesign Values & Data Completeness

2007-2009 Complete Annual Mean Data State County Site ID Design Value Quarters__

2007 2008 2009 (jig/rn 3) 2007 2008 2009 Complete

NewCastle 100031003 13.4 13.0 10.2 12.2 4 3 4 MaxQ

DE 100031007 12.5 11.5 10.0 11.3 4 4 4 MaxQ

100031012 13.4 12.5 10.6 12.2 4 4 4 C100032004 14.4 13.5 11.2 13.0 4 4 4 C

NJ Camden 340071007 13.8 11.9 9.5 11.7 4 4 4 C

Gloucester 340150004 13.3 11.5 9.3 11.4 3 4 3 MaxQ

Bucks 420170012 13.0 12.7 10.8 12.2 4 4 4 CChester 420290100 14.1 13.7 14.1 13.9 2 3 2 Inc

Delaware 420450002 14.7 13.9 12.4 13.7 4 4 4 C

PA Montgomery 420910013 13.1 11.7 10.4 11.7 4 4 4 C Philadelphia 421010004 13.7 13.0 10.8 12.5 4 4 4 C

421010024 12.9 12.0 9.9 11.6 3 4 3 MaxQ421010047 14.3 13.5 11.1 13.0 3 4 3 MaxQ421010055 * 13.5 11.3 12.4 * 4 4 C

421010057 12.0 13.3 11.1 12.1 4 4 4 C

quarter data substitution test.

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Notes: Max Q site passed the maximum quarter data

C = complete

C. EPA’s Analysis ofthe 2007-2009 and 2008-20 10 Philadelphia Area Monitoring Data

EPA has reviewed the ambient air monitoring data for PM25,consistent with the requirements

contained in 40 CFR part 50 and recorded in the AQS for the Philadelphia Area from 2007

through 2010. All monitors measured concentrations averaging well below the annual standardof 15.0 ig/m 3.The highest design value for the most recent 3 year period, 2008-20 10, for thePhiladelphia Area is 13.8 jig/m 3,based on monitoring data collected at monitor 420290100 in

Chester County, Pennsylvania, the “New Garden” monitor.

Data Completeness Issues

1) Maximum Ouarter Data Substitution Test

As shown in Tables 1 and 2, several monitors in the Philadelphia Area have less than 4 quarters

of complete data for one or more year in both the 2007-2009 and 2008-20 10 monitoring periods.

For these monitors, EPA applied the data substitution test set out in the April 1999 EPAguidance document “Guideline on Data Handling Conventions for the PM NAAQS,” attached.

This test is used for monitors with missing data. Maximum recorded values are substituted for

the missing data. The resulting design value is compared to the standard. The monitor passes ifthe design value with maximum values substituted meets the standard. Specifically, the testrequires replacing the missing data with the maximum concentration recorded at the site duringthe same quarter over the three-year period in question, provided that the following criteria are

met. The site must have valid data for at least 50 percent ofthe scheduled number ofsamples for

NJ Camden 340071007 11.9 9.5 9.5 10.3 4 4 4 C

Gloucester 340150004 11.5 9.3 9.1 10.0 4 4 3 MaxQ

PA Bucks 420170012 12.7 10.8 10.5 11.3 4 4 4 C

Chester 420290100 13.7 14.1 13.8 13.8 3 4 4 MaxQ

Delaware 420450002 13.9 12.3 13.2 13.3 4 4 4 CMontgomery 420910013 11.7 10.4 9.5 10.5 4 4 4 C

Philadelphia 421010004 13.0 10.8 10.7 11.5 4 4 4 C

421010024 12.0 9.9 9.6 10.5 4 4 4 C

421010047 13.5 11.1 11.0 11.9 4 4 4 C

421010055 13.5 11.3 11.3 12.0 4 4 4 C421010057 13.3 11.1 10.9 11.7 4 4 4 C

Inc = incomplete

substitution test.

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above could not be used to show attainment for the 2007

2009 monitoring period. The monitor

at this location had various mechanical issues and has since been replaced with a continuous

monitor that is meeting quarterly completeness requirements. In order to determine whether the

NAAQS was met for the 2007-2009 period for the New Garden monitor, EPA has applied a

recently developed procedure to address the missing data. EPA’s procedure is described in the

following section.

Addressing Missing DataEPA developed an objective statistical method to determine if monitors that lack complete datawould have met the NAAQS in subsequent time periods. The first step of the statistical method

used to determine whether an incomplete monitor would have met the NAAQS is to establish a

linear regression relationship between the target monitor and another monitor in or close to the

nonattainment area. The linear regression is then used to fill in the missing data for the targetmonitor. The results are checked with an additional statistical technique, known asbootstrapping, to verify ifthe conclusion of attainment is correct. The Philadelphia Area has 16

monitoring locations, but because ofthe unique siting and local impacts to the New Gardenmonitor, a PM2.5monitoring site in Cecil County, Maryland was selected as the candidate

monitor. This monitor is outside of the non-attainment area, but is approximately 10 miles away

from New Garden with similar siting and local impacts.

The monitor of interest in this analysis is the New Garden monitor. This site has struggled withcompleteness issues since 2006 and has not had a valid design value since 2005. See Figure 1,

Attached. The goal ofthis methodology is to appropriately fill in the missing data from 2007

and 2008 to judge whether this location would likely have monitored attainment ofthe NAAQS

had the monitor had complete data.

Concept for determining design values

The method for determining a design value (DVs) for a monitor with incomplete data (NewGarden) is to establish a linear regression relationship between the site with incomplete data(New Garden) and another site (Cecil County) in the vicinity ofthe nonattainment area which

has more complete data in the period in which the incomplete site (New Garden) is datadeficient. The linear regression relationship is based on time periods in which both the New

Garden and Cecil County monitors were operating. The linear regression equation developed

from the relationship between the New Garden and Cecil County monitor is used to fill in

missing data for the New Garden site in any quarter in the most recent three-year period that did

not have 75 percent completeness based on actual observations, so that the normal data

completeness requirement of 75 percent of data in each quarter ofthe three years is met. After

the missing data for the site is filled in, the results are verified through an additional statisticaltest. The additional statistical test used, referred to as bootstrapping, examines the differences

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of the comparison monitor (Cecil County) and for the number of days of samples that the

comparisons monitor (Cecil County) and the New Garden monitor have in common. EPA has

not established bright lines or specific requirements for determining DVs for monitors with less

than complete data.

Operatingperiod

The candidate monitor (Cecil County) operated during the 3-year period (2007-2009) area in

which the target monitor (New Garden) has incomplete data which establishes a significant

relationship between the monitors. The candidate monitor (Cecil County) does not necessarily

have to have complete data in all 12 quarters ofthe 3-year period, but the candidate monitor

(Cecil County) has enough observations to allow it to be used to fill in enough missing days for

the target monitor (New Garden), so that the New Garden monitor will end up with at least 75percent completeness in all 12 quarters.

Paired samples

Pairs ofsample data for the New Garden monitor and Cecil County monitor from the most recent20-quarter period of operation of the target monitor was used. The “period of operation” ofthe

New Garden monitor was based on the date ofthe last reported sample from the monitor. The

Cecil County monitor had at least 100 historical sample pairs in common with the New Garden

monitor during this period. When there were more than 100 pairs in the 20-quarter period allavailable pairs were used. In addition to the 100 pairs over the 20-quarters, candidate monitorshad at least 20 paired days of data in common with the New Garden monitor for each calendar

quarter (adding together the number of days in a given calendar quarter [Qi, Q2, Q3, or Q4jacross the 20-quarter period). Several candidate sites met the eligibility criteria of 100 pairs overthe 20-quarters, and at least 20 paired days of data in common with the New Garden monitor foreach calendar quarter.

Method for determining design values

Step 1 — Organize data and perform linear regression(s) between the New Garden and candidate

monitors in the Philadelphia Area.

All the available paired data within the period limit described in the Eligibility section was usedto 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 vicinity of the Philadelphia Area.

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1) All candidate monitors were placed into order of highest correlation (highest r-squared in

the linear regression) with New Garden.

2) Using the regression equation relating concentrations at the New Garden monitor and the

Cecil County monitor, estimates ofthe 24-hour average concentrations were made at the

New Garden monitor for all missing scheduled days in the initially incomplete quarters,

in the most recent three-year period at New Garden. Estimates were only made for days

on which a concentration is available at the Cecil County monitor. Estimates were not

made for any days in the quarter for which the New Garden monitor had 75 percent ormore complete data initially. The estimates were combined with any reported data at the

New Garden monitor in the recent 3-year period and the data capture rates were

computed for the originally incomplete quarter. The computation of data capture rates

required an assumption that the required sampling frequency for the New Garden monitorwas recorded. Ifthe Cecil County monitor had a lower sampling frequency than the

New Garden monitor, some missing scheduled days for the New Garden monitor were

not substituted for the regression-based estimates. When the Cecil county monitor had a

lower sampling frequency than the New Garden monitor, the New Garden monitor

sampling schedule was assumed to be a combination of the New Garden and Cecil

County monitors schedules, weighted by the number of originally present and originally

missing scheduled days at the New Garden monitor.

3) If, after performing the process in Step 2, the results produce all 12 quarters at the New

Garden monitor having at least 75 percent of scheduled values, the Cecil County monitor

was selected as the Candidate for the remaining steps.

Step 3— Design Value Computed

The three-year design value was calculated using the actual observations ofthe New Garden

monitor and the regression-based estimates of daily concentrations. The design value for the

New Garden monitor in the Philadelphia Area was below the NAAQS.

Step 4 —Statistical confidence of a design value below the NAAQS checked

The results of Step 3 showed the design value for the New Garden monitor in Philadelphia Area

to be below the NAAQS. In order to show that there is at most a 10 percent probability that the

actual design value (had the New Garden monitor operated more days) was above the NAAQS,further analysis was performed as follows:

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provide a pseudo confidence interval for the partially imputed current-period designvalue for New Garden.

e) Since none of the 1000 runs resulted in a design value above the NAAQS, the New

Garden is considered to have met the NAAQS.

Determining the design value for New Garden monitor 420290100

Steps 1 and 2 were performed with New Garden (monitor 420290100) as the target monitor. The

results of the regressions can be found in Figure 2, attached. On Figure 2, the New Gardenmonitor is listed as Site A. The Cecil County site that was used is listed as Site B. The monitor

Cecil County, (AQS ID: 240150003), was best suited to be used as Site B because it is similarly

sited to the New Garden monitor making the Cecil County site influenced by similar impacts.

Cecil County met the operating period and paired data eligibility criteria for being a Candidatesite. The results ofthe regression between the New Garden and Cecil county monitor is shown

in Figure 3, attached. Estimates for the missing data for 2007 and 2008, were made. As a resultof filling in the missing data, the New Garden monitor now had complete data for 2007 and

2008. A design value of 14.0 ig/m 3was calculated for the New Garden monitor when the

missing data was filled in Figure 4, attached.

The statistical confidence ofthe design value was checked using the method outlined in Stej 4.The results ofthe 1000 bootstrap trials provided the following results: 3 DVs of 13.8 jig/m , 72

DVs of 13.9 Ig/m 3,559 DVs of 14.0 tg/m 3,344 DVs of 14.1 tg/m 3,and 22 DVs of 14.2 jtg/m 3.

None ofthe 1000 bootstrapping trials resulted in a violating DV, which provides statistical

confidence that the New Garden monitor is attaining the 1997 annual PM2,5NAAQS. Figure 5,

attached, shows the results ofthe bootstrapping.

3) Monitor Shutdowns and Startups

Monitors 421010136 and 421010055, Philadelphia County, Pennsylvania

Monitor 421010136, known as “Elmwood,” was shut down by the Philadelphia Air Management

Services (AMS) on December 31, 2007. The physical site went under construction to be updated

with a new shelter, fencing and concrete pad. The last complete annual design value at the

Elmwood monitor was 13.6 j.tg/m 3,considering 2002-2004 data, which meets the annual

NAAQS. Because this monitor was shut down after 2007, data from Elmwood is not reflected in

Tables 1 and 2.

A new monitoring site located at 24th and Ritner Streets, approximately 2 miles from the

Elmwood site, was started shortly after in January 2008. This “Ritner” site, monitor 421010055,

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stat

o

. NJDEP, in coo

d

at

o

with EPA, is actively pursuing the establishment of a new

monitoring station in Camden. Therefore, it is not appropriate to consider this monitor in the

determination of attainment for the Philadelphia Area. The last valid annual design value was

13.4 ig/m 3,considering 2005- 2007 data. This design value meets the annual NAAQS.

Attachments:

- EPA AQS Quick Look Report (AMP48O), dated August 18, 2011, containing 2007-2010

annual PM25 air quality data for Delaware, New Jersey, and Buck County, Pennsylvania

portions ofthe Philadelphia Area.

- EPA AQS Quick Look Report (AMP48O), dated August 18, 2011, containing 2007-2010

annual PM2.5air quality data for the Chester, Delaware, Montgomery, and PhiladelphiaCounties, Pennsylvania.

- Figure 1. Philadelphia Annual Design Value History.

- Figure 2. Philadelphia Sites and 2007-2009 DVs & Data Capture.

- Figure 3. Linear Regression Results.

- Figure 4. Imputation and Resulting Data Capture and DV Recalculation.

- Figure 5. Bootstrapping Residuals (and DV Recalculations).

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