CITY OF PHILADELPHIA 

Department of Public Health 

Environmental Protection Division 

Air Management Services 

InterOffice Memo 

To: File 

From: Edward Wiener 

Date: March 8, 2016 

Subject: Clarifications Regarding RACT Certifications and De-Minimis Determinations

Introduction: 

The Clean Air Act (CAA) requires that moderate (or worse) ozone nonattainment areas 

implement reasonably available control technology (RACT) controls on all major sources of 

volatile organic compounds (VOC) and nitrogen oxides (NOx). Philadelphia County is part of 

the Philadelphia-Wilmington-Atlantic City moderate ozone nonattainment area for the 1997 8-

hour ozone NAAQS. The purpose of this document is to clarify source-specific RACT 

certifications that were previously submitted and/or are being submitted as a SIP revisions to 

EPA. This document also addresses AMS’ revised approach in determining sources (i.e., 

emissions units) which are “de-minimis” for 1997 8-hour RACT determinations. 

RACT Certifications

By definition, a major source threshold is provided for RACT applicability based on the 

classification of the nonattainment area in which the source is located. For RACT purposes, a 

major source of NOx and VOC in Philadelphia under the 1997 8-hour ozone NAAQS is that 

which emits more than 100 and 50 tons per year of NOx and VOC, respectively. AMS evaluated 

RACT controls for all major NOx and/or VOC emitting facilities in Philadelphia under the 1997 

8-hour ozone NAAQS, and documented such evaluations for each facility in technical 

memorandums. The RACT evaluations have been submitted to EPA for approval as a revision 

to the Pennsylvania State Implementation Plan (SIP). A list of major NOx and/or VOC emitting 

facilities evaluated by AMS for 1997 8-hour ozone RACT is provided in Table 2 of this SIP 

revision. 

AMS has evaluated RACT for a number of facilities that are major NOx and/or VOC sources 

under the 1997 8-hour ozone NAAQS and are subject to previous case-by-case RACT 

determinations under the 1-hour ozone standard, as approved in the SIP in 40 CFR 

52.2020(d)(1). Based on these evaluations, AMS is certifying that the 1-hour ozone standard 
case-by-case RACT controls for certain emissions units in certain major NOx and/or VOC 

emitting facilities continue to represent case-by-case RACT for the 1997 8-hour ozone standard. 

The technical memorandums document the RACT evaluation for each major NOx and/or VOC 

emitting facility in Philadelphia and include each certification as well as additional supporting 

information. AMS submitted on February 18, 2015 or is submitting to EPA the technical 

memorandums as part of SIP revisions to address Philadelphia’s 1997 8-hour ozone RACT 

demonstration. 

Further, AMS certifies that certain NOx and/or VOC emitting facilities that were subject to caseby-case RACT determinations under the 1-hour ozone standard, are no longer subject to RACT 

under the 1997 8-hour ozone standard because they have either shutdown or are no longer 

considered major sources of RACT, as defined above. These facilities have been identified by 

AMS in the November 1, 2014 Memorandum document titled “1-Hour RACT Facilities not in 8-

Hour RACT”, which was previously submitted to EPA as part of the on February 18, 2015 

RACT SIP revision. 

For those facilities that have shutdown, as listed in the aforementioned document, AMS further 

requests EPA to remove from the SIP (40 CFR 52.2020(d)(1)) any previous case-by-case RACT 

determinations approved under the 1-hour ozone standard. AMS certifies that none of these 

shutdown facilities have active operating permits or air pollution licenses for any equipment, and 

that under Pennsylvania and Philadelphia regulations, they cannot operate until further 

notification and issuance of applicable permits. AMS has included appropriate supporting 

information for this certification in the February 18, 2015 RACT SIP revision for Philadelphia. 

AMS clarifies that those NOx and/or VOC emitting facilities that are subject to case-by-case 

RACT determinations under the 1-hour ozone standard and that are no longer major sources of 

NOx or VOC subject to RACT requirements under the 1997 8-hour ozone standard, continue to 

remain subject to the 1-hour ozone RACT determinations in the Pennsylvania SIP under 40 CFR 

52.2020(d)(1). 

De Minimis Emission Sources

AMS has determined some emission units at certain major NOx and VOC emitting facilities to 

be “de minimis” due to their low potential emissions and not requiring further RACT analysis. 

In the February 18, 2015 RACT SIP revision, AMS had defined “de minimis” emission sources 

by establishing as general guidelines specific potential-to-emit (PTE) thresholds of 5 tons per 

year (tpy) for NOx and 2.7 tpy for VOC. Because sources or emissions units vary in 

characteristics such as age, size, and potential controls, AMS has decided to follow EPA’s 

recommendation to not establish specific cut-off thresholds in determining RACT applicability 

and changed this approach to determine de minimis sources on a case-by-case basis. Sources 

which have been determined de minimis are those for which the installation and operation of 

controls would be unreasonable due to size and level of emissions, based on AMS engineering 

and permitting knowledge. See EPA Comment No. 8 in the January 9, 2015 Comment and 
Response Document created by AMS. In this RACT SIP revision, revised case-by-case de 

minimis determinations have been provided for each affected emissions unit in the corresponding 

technical memorandums.