UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

REGION III

1650 Arch Street

Philadelphia, Pennsylvania 19103

DATE: March 18, 2015

SUBJECT: Technical Support Document Regarding Monitoring Data –Pennsylvania; 

Determination of Attainment of the 2006 24-hour Fine Particulate Standards for 

the Liberty-Clairton Nonattainment Area

FROM: Emlyn Vélez-Rosa, Environmental Engineer \s\ 3/17/2015

Office of Air Program Planning

Loretta Hyden, Environmental Engineer \s\ 3/18/2015

Office of Air Monitoring & Analysis

TO: File- Part 52 SIP Action- Docket ID No. EPA-R03-OAR-2015-0175

THRU: Marilyn Powers, Acting Associate Director \s\ 3/17/2015

Office of Air Program Planning

I. INTRODUCTION

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

the Environmental Protection Agency’s (EPA’s) proposed determination that the LibertyClairton, PA 24-hour fine particulate (PM2.5) nonattainment area (the Liberty-Clairton Area) has 

attained the 2006 24-hour PM2.5 national ambient air quality standard (NAAQS).

II. BACKGROUND

On July 16, 1997, EPA established an annual PM2.5 NAAQS at 15.0 micrograms per cubic 

meter (μg/m3) (hereafter referred to as “the 1997 annual PM2.5 NAAQS”), based on a 3-year 

average of annual mean PM2.5 concentrations (62 FR 38652, July 18, 1997). See 40 CFR 50.7. 

On September 21, 2006, EPA promulgated a new 24-hour standard of 35 μg/m3based on a 3-

year average of the 98th percentile of 24-hour concentrations (71 FR 61144, October 17, 2006). 

The revised 2006 24-hour PM2.5 standard (hereafter “the 2006 24-hour PM2.5 NAAQS”) became 

effective on December 18, 2006. See 40 CFR 50.13.
2

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 (70 FR 944), EPA 

published its nonattainment area designations for the 1997 annual PM2.5 NAAQS based upon air 

quality monitoring data for calendar years 2001-2003. On November 13, 2009, EPA published 

designations for the 2006 24-hour PM2.5 NAAQS (74 FR 58688), which became effective on 

December 14, 2009. In both actions, EPA designated the Liberty-Clairton Area as nonattainment 

for the 1997 annual and 2006 24-hour PM2.5 NAAQS, respectively. The Liberty-Clairton Area is 

comprised of the following portion of Allegheny County: the boroughs of Lincoln, Glassport, 

Liberty, and Port Vue and the City of Clairton. See 40 CFR 81.339 (Pennsylvania). The LibertyClairton Area is surrounded by, but separate and distinct from the Pittsburgh-Beaver Valley 

PM2.5 nonattainment area.

A nonattainment designation under the CAA triggers additional planning requirements for 

states to show attainment of the NAAQS in the nonattainment areas by a statutory attainment 

date, as specified in the CAA. Since 2005, EPA had implemented the 1997 and 2006 PM2.5 

NAAQS based on the general implementation provisions of subpart 1 of Part D of Title I of the 

CAA (subpart 1). On January 4, 2013, in Natural Resources Defense Council v. EPA (NRDC v. 

EPA), the D.C. Circuit determined that EPA should be implementing its PM2.5 pollution standard 

under additional CAA requirements than those EPA had been following in subpart 1 and

remanded to EPA the “Final Clean Air Fine Particle Implementation Rule” (1997 PM2.5 

Implementation Rule) (72 FR 20586, April 25, 2007) and the “Implementation of the New 

Source Review (NSR) Program for Particulate Matter Less than 2.5 Micrometers (PM2.5)” final 

rule (2008 NSR PM2.5 Rule).1 706 F.3d 428 (D.C. Cir. 2013). The D.C. Circuit found that the 

EPA erred in implementing the 1997 PM2.5 NAAQS solely pursuant to subpart 1, without 

consideration of the particulate matter specific provisions of subpart 4 of Part D of Title I of the 

CAA (subpart 4). 

While the regulatory provisions of EPA’s 1997 PM2.5 Implementation Rule do not explicitly 

apply to the 2006 24-hour PM2.5 NAAQS, EPA’s underlying statutory interpretation has been the 

same for both standards. On March 2, 2012, EPA provided implementation guidance for the 

2006 24-hour PM2.5 NAAQS which reaffirmed and continued the framework and policy

approaches of the 1997 Implementation PM2.5 Rule.

2

 Thus, EPA believes that the statutory 

provisions of subpart 4 are also applicable to the 2006 24-hour PM2.5 NAAQS. 

 

1 EPA’s 2008 NSR PM2.5 Rule relates to requirements for the NSR permitting program required by parts C and D of 

title I of the CAA. The details and provisions of the 2008 NSR PM2.5 Rule are not relevant to this proposed 

rulemaking. 

2 EPA subsequently withdrew the implementation guidance on June 6, 2013 subsequent to the D.C. Circuit’s 

decision in NRDC v. EPA. EPA’s June 6, 2013 withdrawal memorandum is available at 

http://www.epa.gov/ttn/naaqs/pm/pdfs/implementationguidancewithdrawmemo.pdf.
3

Among other things, subpart 4 requires EPA to classify nonattainment areas for the PM2.5 

NAAQS based on the severity of their pollution problem. On April 25, 2014, subsequent to the 

January 4, 2013 Court decision, EPA finalized a rule identifying the classification of all PM2.5 

areas currently designated nonattainment for the 1997 and 2006 PM2.5 NAAQS as “Moderate,” 

consistent with subpart 4 of the CAA. See 79 FR 31566 (June 2, 2014). Consequently, the 

Liberty-Clairton Area was classified as Moderate for the 2006 24-hour PM2.5 NAAQS.

Under section 188(c)(1) of the CAA, a moderate nonattainment area shall attain the PM2.5 

NAAQS as expeditiously as practicable but no later than the end of the sixth calendar year after 

the area’s designation to nonattainment. Because the designation of nonattainment areas for the 

2006 24-hour PM2.5 NAAQS became effective on December 14, 2009, the presumptive sixth 

year attainment date for most moderate nonattainment areas would be no later than December 

2015. Under EPA’s longstanding Clean Data Policy interpretation, a determination that a 

nonattainment area has attained the NAAQS prior its statutory applicable attainment date 

suspends the state’s obligation to submit attainment-related planning requirements of the CAA 

for so long as the area continues to attain the standard.

3

 These include requirements to submit an 

attainment demonstration, reasonable further progress (RFP), reasonably available control 

measures (RACM), and contingency measures, because the purpose of these provisions is to help 

reach attainment, a goal which has already been achieved. To determine attainment, EPA 

commonly uses three calendar years of complete air quality monitoring data for the 

nonattainment area. 

III. EPA’s REQUIREMENTS

A. 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. 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 comparison with the PM2.5 NAAQS, only 

air quality data measured by a Federal Reference Method (FRM), a Federal Equivalent Method 

 

3 For an EPA memorandum discussing interpretation that three years of data showing attainment of a NAAQS 

suspends requirements to submit certain attainment plan SIP requirements including those in section 172 of the 

CAA, see Reasonable Further Progress, Attainment Demonstration, and Related Requirements for Ozone 

Nonattainment Areas Meeting the Ozone National Ambient Air Quality Standard, EPA Memorandum from John S. 

Seitz, Director, Office of Air Quality Planning Standards, May 10, 1995 (Seitz Memorandum), located at 

http://www.epa.gov/ttn/caaa/t1/memoranda/clean15.pdf.
4

(FEM), or an Approved Regional Method (ARM), in accordance with 40 CFR part 53 or part 58 

shall be used.

B. Monitoring Data 

Under EPA regulations at 40 CFR 50.13(c), the 2006 24-hour primary and secondary PM2.5

NAAQS are met when the 98th percentile 24-hour concentration, as determined in accordance 

with 40 CFR part 50, appendix N, is less than or equal to 35 ug/m3. Data handling conventions 

and computations necessary for determining whether areas have met the PM2.5 NAAQS, 

including requirements for data completeness, are also provided in 40 CFR part 50, appendix N. 

Specifically, the 2006 24-hour PM2.5 NAAQS is met when the 24-hour design value at each 

monitoring site is less than or equal to 35 μg/m3. The comparison of the 24-hour design value to 

the 2006 24-hour PM2.5 NAAQS shall be based on 3 consecutive, complete years of air quality 

data. 

Three years of valid annual 98th percentile PM2.5 mass concentrations are required to 

produce a valid 24-hour PM2.5 design value. The 98

th percentile is defined as the daily value out 

of a year of PM2.5 monitoring data below which 98 percent of all daily values fall. A year meets 

data completeness requirements when at least 75 percent of the scheduled sampling days for each 

quarter have valid data. However, years shall be considered valid, notwithstanding quarters with 

less than complete data (even quarters with less than 11 samples), if the resulting annual 98th

percentile value or resulting 24-hour standard design value is greater than the level of 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 for comparisons to the 2006 24-hour 

PM2.5 NAAQS. 

All valid FRM/FEM/ARM PM2.5 mass concentration data produced by suitable monitors are 

required to be submitted to EPA’s Air Quality System (AQS) in μg/m3and must be used in the

design value calculations. Generally, EPA will only use such data if they have been certified by 

the reporting organization. When the data for a particular monitoring site and year meet the data 

completeness requirements, the 98th percentile is calculated for each monitoring site by 

following the steps outlined in subsection 4.5 of 40 CFR part 50, appendix N. The 24-hour 

design value is then calculated by averaging the annual 98th percentiles for the 3-year period. 

For the purposes of comparing the calculated 24-hour design value to the applicable level of the 

NAAQS (35 μg/m3), the final results of the 24-hour design value calculations are rounded to the 

nearest 1 μg/m3(that is, decimals 0.5 and greater are rounded up to the nearest whole number, 

and any decimal lower than 0.5 is rounded down to the nearest whole number). Results for all 

intermediate calculations must not be rounded.
5

IV. EVALUATION OF AIR QUALITY MONITORING DATA

A. Monitoring Network Adequacy

Allegheny County Health Department (ACHD) maintains and operates a total of two PM2.5 

monitoring sites in the Liberty-Clairton Area, whose data met the requirements for use in 

determining attainment of the 2006 24-hour PM2.5 NAAQS. EPA has previously determined that 

the PM2.5 monitoring network for the Liberty-Clairton Area is adequate. As documented, the 

two monitors in the Liberty-Clairton Area measure ambient air quality by following one of 

EPA’s approved FEM, FRM, or ARM, in accordance with 40 CFR part 53 and part 58. EPA 

found that the number of monitors in the Liberty-Clairton Area continues to meet the minimum 

regulatory requirements given in 40 CFR part 58, appendix D, section 4.7. The monitoring 

network in place is in accordance with Allegheny County’s most recent annual monitoring 

network plan approved by EPA, as required by 40 CFR 58.10.4 

B. Certified Air Quality Monitoring Data, 2012-2014

ACHD submitted and certified quality-assured air quality PM2.5 monitoring data for the LibertyClairton Area into AQS. The 2012-2014 data recorded meets the completeness requirements of 

40 CFR part 50, appendix N, thus allowing a valid design value calculation for each monitoring

site for the 2012-2014 period. Attached to this document is a “Design Value Report” from AQS,

containing daily PM2.5 data for the Liberty-Clairton Area for 2012-2014, as summarized in 

Table 1. 

Table 1: 2012-2014 Liberty-Clairton Area Daily PM2.5 Monitoring Data & Completeness

Monitor Name AQS Site ID Location

98th Percentile 2012-2014 

Design Value 

(μg/m3)

Complete 

2012 2013 2014 Data?

Liberty 42-003-0064 Liberty Borough 42.5 31.1 32.2 35 Yes

Clairton 42-003-3007 City of Clairton 19.2 17.1 31.2 23 Yes

Following the computation procedures of 40 CFR part 50, appendix N, the design values for both 

monitors in the Liberty-Clairton Area are 35 and 25 μg/m3, respectively, for the 2012-2014 

monitoring period. Consistent with EPA’s requirements of 40 CFR 50, the monitors in the 

Liberty-Clairton Area are showing attainment of the 2006 PM2.5 NAAQS, based on 2012-2014 

 

4 The ACHD’s 2014 annual ambient monitoring network plan was approved by EPA in a November 21, 2014 letter 

from Shawn M. Garvin, Regional Administrator, EPA Region III, to Jayme Graham, Program Manager of the 

Allegheny County Health Department. 
6

quality-assured and certified air quality data.

V. CONCLUSION

EPA has reviewed quality-assured, quality-controlled, and certified 2012-2014 ambient air 

quality monitoring data for the Liberty-Clairton Area. EPA finds that the Liberty-Clairton Area 

has attained the 2006 24-hour PM2.5 NAAQS, based on the most recent available PM2.5 air 

quality data.

ATTACHMENT

- Appendix A: EPA AQS “Design Value Report” (AMP480) dated February 3, 2015, 

containing PM2.5 air quality data for 2012-2014 for the Liberty-Clairton Area