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# • D E PARTM E NT O F ENVIRONM ENT AL PROTE C TIO N

P A UL R LE PAGE

GOVERNO R
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 ofEnvironmental Protection submitted amendments to the Chapter I00 Definitions rule into Maine's State Implementation Plan as part ofits 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 I00. 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 ofthe 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 ofthe 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 I00, 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 I0, February 8, 1988 , for nitrogen dioxide (N02) and October 20, 2010 for PM2.5 represented as follows:

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W l \)' d (l \\ \\ \\ Ill.H il l t;O\ I dl f'A. For Attainment Areas : (1 ) For sulfur dioxide (S02) and PM 10, this term shall include the actual emis sions representative of S02 and PM 10 sources in existence on August 7, 1977, and the allowable emissions ofsources 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 ofsources 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 ofoperation 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 ofoperations 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 ofthe 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 ofthe 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 ofthe 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 ofthe 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 ofpending SIPs , the Department is withdrawing its submis sion 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 ofAir Quality

cc: Ida McDonnell, EPA Patrick Bird, EPA SIP file

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