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STAT E O F MAIN E 

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D E PARTM E NT O F ENVIRONM ENTAL PROTE CTIO N 

PAUL R LEPAGE 

GOVERNOR 

March 3, 2016 

David Conroy, Chief 

Air Programs Branch 

U.S. EPA Region I-NE 

5 Post Office Square 

Mail Code: OEP 05-2 

Boston, Ma. 02109-3912 

Dear Mr. Conroy: 

On February 14, 2013, the Department of Environmental Protection submitted 

amendments to the Chapter I 00 Definitions rule into Maine's State Implementation Plan 

as part of its efforts to implement federal new source review (NSR) requirements for the 

PM 2.5 National Ambient Air Quality Standards and greenhouse gas emissions. The 

amendments to Chapter 100 included revisions and/or additions to a number of 

definitions, including "baseline concentration," in Section 16 of Chapter I 00. 

These amendments were adopted in accordance with Maine Administrative Procedures 

Act, 38 MRS Chapter 375, which makes a "proposed rule" subject to public notice and 

comment opportunities. 38 MRS § 8052. "Proposed rule" is defined to mean "a rule that 

an agency has formally proposed for adoption through submission of the rule to the 

Secretary of State for publication pursuant to section 8053, subsection 5." 5 MRS § 

8002(8-A). That definition does not distinguish between new elements of the rule 

proposed for adoption for the first time, and those pre-existing elements that are proposed 

for adoption. Therefore, all elements of the proposed rule - both new and pre-existing -

are subject to the public's opportunity for comment. Accordingly, the Department's 

rulemaking process afforded the opportunity to comment on the entirety of Chapter I 00, 

including the definition of "baseline concentration". The Department intends to replace 

the current SIP-approved definition of "baseline concentration" with the following 

definition as contained in its February 14, 2013 submittal: 

"16. Baseline concentration. "Baseline concentration" means the actual ambient 

air quality which existed in an area as of: August 7, 1977, for S02 and PM I 0, 

February 8, 1988, for nitrogen dioxide (N02) and October 20, 2010 for PM2.5 

represented as follows: 

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A. For Attainment Areas: 

(1 ) For sulfur dioxide (S02) and PM 10, this term shall include the actual 

emissions representative of S02 and PM 10 sources in existence on August 

7, 1977, and the allowable emissions of sources which commenced 

construction before January 6, 1975, but were not in operation by August 

7, 1977. 

(2) For nitrogen oxides (NOx) (measured as N02), this term shall include the 

actual emissions representative of sources in existence on February 8, 

1988. For sources starting operation after February 8, 1985, but prior to 

February 8, 1988, representative emissions shall be determined after three 

years of operation and be based on two years of actual emissions more 

representative of normal operation. NOx sources commencing 

construction by February 8, 1988, but not in operation by that date shall 

use allowable emissions for baseline concentration until three years after 

start of operations at which time actual emissions more representative of 

normal operation for that source shall be determined and used for baseline 

concentration. 

The actual NOx (measured as N02) emissions increases or decreases at 

any source occurring after February 8, 1988, shall not be included in the 

baseline concentration but shall be included in the determination of the 

increment consumed, except as specified in the previous paragraph. 

(3) For PM2.5, this term shall include the actual emissions representative of 

sources in existence on October 20, 2010. 

The actual PM2.5 emissions increases or decreases at any source occurring 

after October 20, 2010, shall not be included in the baseline concentration 

but shall be included in the determination of the increment consumed. 

B. For Nonattainment Areas: 

(1) For areas designated nonattainment at the baseline date(s), baseline 

concentration means the actual ambient air quality that exists in the 

affected areas at the date the DEP receives the first major new source or 

major modification application after the date EPA approves the 

designation of the area to attainment. 

(2) The following S02 and PM10 emissions shall not be included in the 

baseline concentration but shall be included in the determination of the 

applicable maximum allowable increases: 

2 
(a) Actual emissions from any source on which construction commenced 

between January 6, 1975 and August 7, 1977; and 

(b) Actual emission increases and decreases at any source occurring after 

August 7, 1977." 

In an effort to facilitate EPA' s review and approval of pending SIPs, the Department is 

withdrawing its submission of " regulated pollutant" as found in Section 149 of Chapter 

100, and the definition of "significant emissions increase" as found in Section 156 of 

Chapter 100. The Department is also withdrawing the February 14, 2013 submittal of its 

Chapter 140 Part 70 Air Emission License Regulation at this point in time, and will be resubmitting these rules for approval under the Title V program. Should you have any 

questions, please contact Jeff Crawford at (207) 287-7647. 

Marc A. R. Cone, Director 

Bureau of Air Quality 

cc: Ida McDonnell, EPA 

Patrick Bird, EPA 

SIP file 

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