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UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

REGION III

1650 Arch Street

Philadelphia, Pennsylvania 19103

DATE: February 22, 2011

SUBJECT: Technical Support Document - Delaware, 7 DE Administrative Code 1125 –

Requirements for Preconstruction Review, Section 3.0 – Prevention of Significant 

Deterioration of Air Quality

/s/

FROM: Sharon McCauley, Environmental Protection Specialist

Office of Permits and Air Toxics (3AP10) 

TO: File

THRU: Kathleen Anderson, Associate Director

Office of Permits and Air Toxics (3AP10)

I. BACKGROUND

This State Implementation Plan (SIP) revision request governs the permits for constructing and 

significantly modifying major stationary sources of air pollutants in Prevention of Significant 

Deterioration (PSD) areas located in Delaware. This regulatory revision was made effective as a 

legislative rule in Delaware on April 11, 2010. These current Delaware regulations can be found 

in Regulation 1125, Section 3.0. This SIP revision, as proposed, will only replace the current 

regulations found in 1125 which establish NOx as a precursor to Ozone, but will keep in tact the 

formally approved Delaware SIP increments for NOx found in the Federal Register notice for 

Delaware dated July 27, 1993. 

Delaware’s proposed SIP submission addresses changes needed in the part C PSD permit 

program. This SIP submission also corrects deficiencies identified by EPA in the March 27, 

2008 Federal Register notice entitled, “Completeness Findings for Section 110(a) State 

implementation Plans for the 8 hour Ozone National Ambient Air Quality Standards (1997 

Ozone NAAQS)”, (73 FR 16205). EPA’s proposed approval of this SIP submission addresses 

Delaware’s compliance with the portion of Clean Air Act (CAA) Section 110 (a)(2)(C) & (J) 

relating to the Part C permit program for the 1997 NAAQS Ozone NAAQS, because this 

proposed approval would approve regulating NOx as a precursor to ozone in Delaware’s SIP in 

accordance with the Federal Register notice dated November 29, 2005 (70 FR 71612) that 

finalized NOx as a precursor for ozone regulations set forth at 40 CFR 51.166 and in 40 CFR 

52.21. 
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EPA has determined that the current amendments to Delaware's PSD permit program at 7 DE 

Administrative Code 1125 – Requirements for Preconstruction Review, Section 3.0 – Prevention 

of Significant Deterioration of Air Quality, as submitted on April 1, 2010, meet the minimum 

requirements of 40 CFR 51.166 and the CAA. This SIP proposal is being proposed as a full 

approvable revision to the Delaware SIP. No other changes to the currently approved SIP are 

being proposed for approval at this time. 

II. SUMMARY OF ACTION

This rule establishes a state construction permit program consistent with the federal Clean Air 

Act’s Title I program and implementing regulations at 40 CFR §51.166, “Prevention of 

Significant Deterioration of Air Quality.” 7 DE Administrative Code 1125 – Requirements for 

Preconstruction Review, Section 3.0 – Prevention of Significant Deterioration of Air Quality is 

part of the SIP and sets forth the criteria and procedures for major stationary sources to obtain a 

permit to construct, operate and/or modify a major stationary source.

As required by 40 CFR Part 51, Subpart I - “Review of New Sources and Modifications,” this 

rule adopts criteria and procedures for the prevention of significant deterioration of air quality 

that are consistent with the governing federal regulation at 40 CFR §51.166. Promulgation of this 

rule by the Legislature is necessary for Delaware to fulfill its responsibilities under 40 CFR Part 

51 and the CAA, as amended. Revisions to the Delaware rule are simply adding new references 

to include NOx as a precursor to Ozone to comport with federal counterpart language. The 

Delaware Department of Natural Resources and Environmental Control has now submitted a 

final rule 7 DE Administrative Code 1125 – Requirements for Preconstruction Review, Section 

3.0 – Prevention of Significant Deterioration of Air Quality as a proposed revision to the SIP.

III. INFRASTRUCTURE

Delaware’s proposed SIP submission addresses changes needed in the part C PSD permit 

program. This SIP submission also corrects deficiencies identified by EPA in the March 27, 

2008 Federal Register notice entitled, “Completeness Findings for Section 110(a) State 

implementation Plans for the 8 hour Ozone National Ambient Air Quality Standards (1997 

Ozone NAAQS)”, (73 FR 16205). EPA’s proposed approval of this SIP submission addresses 

Delaware’s compliance with the portion of Clean Air Act (CAA) Section 110 (a)(2)(C) & (J) 

relating to the Part C permit program for the 1997 NAAQS Ozone NAAQS, because this 

proposed approval would approve regulating NOx as a precursor to ozone in Delaware’s SIP in 

accordance with the Federal Register notice dated November 29, 2005 (70 FR 71612) that 

finalized NOx as a precursor for ozone regulations set forth at 40 CFR 51.166 and in 40 CFR 

52.21. 

IV. PROGRAM REVIEW

A. Delaware Submittal

The Delaware submittal includes new references which were added to the State rule to
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include NOx as a precursor to Ozone to comport with federal counterpart language.

B. Public Notice

Public notice was provided and a public hearing was held in the State of Delaware on 

January 5, 2010 and no comments were received regarding the changes made to 

Regulation 1125.

C. Regulatory Review of Proposed SIP 

DNREC Regulation 1125 Section 3.1 Definitions

The following is a brief summary of the changes.

Regulation 

3.1

Modified Definition of Major Stationary Source was modified to include 

NOx as a precursor to Ozone along with volatile organic 

compounds.

DNREC Regulation 1125 Section 3.7.7.1Review of Major Stationary Sources and Major 

Modifications – Source Applicability and Exemptions

The following is a brief summary of the changes.

Section Status Description

Regulation 

3.7.7.1

Modified No de Minimus air quality level is provided for ozone....

DNREC Regulation 1125 Section 3.11.1.5Air Quality Analysis

The following is a brief summary of the changes.

Section Status Description

Regulation 

3.11.1.5

Modified Modified to include NOx as precursor to ozone.

Note: While reviewing the proposed SIP submittal it was noted that the previously approved 

NOx increments as approved in Federal Register notice 58 FR 40065 dated July 27, 1993 were 

not found in the current submittal of Delaware’s regulation under 1125, Section 3.0 and Section 

1.9. EPA will propose approving the addition of NOx as a precursor to Ozone to the regulations 

noted above, and will in effect, maintain the prior SIP approval of the NOx increments, as 

previously approved in 1993. 

V. RECOMMENDED AGENCY ACTION

EPA recommends approving the revision to Delaware's SIP to include changes to 7 DE 

Administrative Code 1125 – Requirements for Preconstruction Review, Section 3.0 – Prevention 

of Significant Deterioration of Air Quality. As previously noted, this revision will establish NOx

as a precursor to ozone in the State of Delaware SIP.