October 2015

Revision to the

State Implementation Plan 

for Air Quality

Demonstration that Maine Complies with the

Good Neighbor Requirements of

Clean Air Act Section 110(a)(2)(D)(i)(I) for the

2008 Ozone National Ambient Air Quality Standard

Prepared by the

Bureau of Air Quality
Page | 1

Summary

Sections 110(a)(l) and (2) of the Clean Air Act (CAA) require all states to summarize any necessary 

revisions to their State Implementation Plans (SIP) to implement, maintain and enforce any revised or new

national ambient air quality standard (NAAQS). These SIP revisions are commonly referred to as

“infrastructure SIPs.” In March 2008, the U.S. Environmental Protection Agency (EPA) revised the ozone

NAAQS, and in July 2012, completed the designation process for nonattainment areas. The Maine 

Department of Environmental Protection (DEP) subsequently submitted Maine’s infrastructure SIP on June 

7, 2013.

This SIP revision supplements DEP’s June 2013 submittal, further addressing the CAA §110(a)(2)(D)(i)(I)

(“good neighbor”) requirements to demonstrate that emissions from sources in Maine do not significantly

contribute to nonattainment in, or interfere with maintenance by, any other state with respect to the 2008 

ozone NAAQS. DEP’s analysis of recent ozone monitoring data, recent EPA modeling for the Cross State 

Air Pollution Rule (CSAPR) and a potential new transport rule demonstrates that Maine meets its good 

neighbor requirements for the 2008 NAAQS.

1

Background and Introduction

On March 12, 2008, EPA revised the primary and secondary ozone NAAQS.

2

Specifically, EPA 

established both the primary and secondary 8-hour standards at 75 parts per billion, based on the 3-year 

average of the fourth-highest value of the yearly distribution of 8-hour daily maximum concentrations. 

EPA promulgated initial designations on April 30, 2012, designating Maine as unclassifiable/attainment.

3

Pursuant to CAA §110(a)(l) and (2), all states must submit necessary revisions to their SIP to provide for 

the implementation, maintenance and enforcement of revised or new NAAQS. States must maintain a

comprehensive air quality management program, including enforceable emission limitations, an ambient 

monitoring program, an enforcement program, air quality modeling, and adequate personnel, resources, and 

legal authority. The “good neighbor” provisions of the CAA require each SIP to prohibit its emissions from

significantly contributing to nonattainment or maintenance of the ozone NAAQS in other states, or

interfering with programs to prevent significant deterioration of air quality or to achieve reasonable 

progress toward the national visibility goal for Federal class I areas (national parks and wilderness areas).

Based on timing requirements in the CAA, states were required to submit ozone infrastructure SIP

revisions by March 2011. However, due to legal challenges to the 2008 ozone NAAQS, and EPA’s

reconsideration of the standard, nonattainment area designations remained unknown until March 2011.

Following EPA’s completion of designations in July 2012, DEP submitted Maine’s ozone infrastructure

SIP on June 7, 2013, after meeting the public participation requirements of 40 CFR 51, Appendix V, 

Section 2.1. In accordance with EPA’s recommendation, the DEP forestalled submitting the 

110(a)(2)(D)(i)(I) components at that time.4 The DEP’s submission awaits EPA approval at this time.

In January 2015, EPA issued guidance to assist in preparing SIP revisions to address compliance with CAA 

§110(a)(2)(D)(i)(I) for the 2008 ozone NAAQS. The guidance discusses elements previously used to 

address interstate transport for other NAAQS and presented new, preliminary EPA atmospheric ozone

modeling (modeling) results for 2018 based on emission reductions anticipated from previously adopted air 

pollution control programs. EPA’s preliminary modeling identified states that are projected to significantly

 

1 Memorandum from Stephen Page to EPA Regional Air Directors, Regions 1-10 on Good Neighbor SIP Provision for

the 2008 Ozone NAAQS, January 22, 2015.

2 The NAAQS revisions were published in the 3/27/2008 Federal Register and became effective on 5/27/2008.

3 The designationsrulemaking was published in the 5/21/2012 Federal Register, and became effective 7/20/2012.

4

In comments to DEP dated February 7, 2013 EPA suggested “[i]n light of ongoing litigation, we suggest Maine 

address the ‘significantly contribute to nonattainment or maintenance in another state’ portion of element D(i) . . . at a 

later time.”
Page | 2

contribute (at least 1% of the NAAQS) to nonattainment/maintenance concerns in other states in 2018. 

EPA held a workshop in April 2015 to facilitate discussions, if necessary, on control and emission budget

approaches that could be used to meet the good neighbor obligations.

5 At that meeting, EPA indicated plans 

to release updated modeling incorporating inventory improvements during the summer of 2015, continue

the transport discussions, and propose rulemaking in late 2015 for a federal implementation plan (FIP) 

backstop, to take effect in states that do not timely submit approvable SIPs. 

EPA’s January 2015 guidance refers to a four-step process used previously to address ozone transport:

1) Identify downwind air quality problems;

2) Identify upwind states that contribute enough to those downwind air quality problems to warrant 

further review and analysis;

3) Identify the emissions reductions necessary to prevent an identified upwind state from 

contributing significantly to those downwind air quality problems; and

4) Adoption of permanent and enforceable measures needed to achieve those emission 

reductions.

Maine’s good neighbor SIP revision is consistent with this four-step process.

Through this SIP submittal, DEP analyzed both ambient monitoring data and EPA modeling results to 

demonstrate that Maine’s existing control programs ensure that emissions from Maine do not 

significantly contribute to nonattainment or maintenance issues in any other state with respect to the 2008

ozone NAAQS. Therefore, Maine complies with the requirements of CAA §110(a)(2)(D)(i)(I).

Methodology

The “good neighbor” provisions of CAA §110(a)(2)(D)(i)(I) require each state’s SIP to prohibit emissions 

that significantly contribute to nonattainment in, or interfere with maintenance by, any other state with 

respect to any NAAQS. DEP used the following methodology to implement the four-step process outlined 

in EPA’s January 2015 guidance to identify and address Maine’s good neighbor obligation.

DEP examined the results of EPA’s modeling set out in the January 2015 guidance to:

• Identify monitors outside of Maine that are projected to have nonattainment or maintenance 

issues in 2018; and

• Determine if the modeled impacts associated with emissions from Maine sources are projected 

to exceed the screening threshold at any of the nonattainment/maintenance monitors in 2018.

EPA’s modeling did not identify any significant impacts by Maine emissions to downwind air quality 

problems in 2018. Therefore DEP determined it was unnecessary to undertake further analysis regarding the 

effectiveness of current control techniques.

The following sections document the application of the above methodology and DEP’s findings regarding

Maine’s compliance with CAA §110(a)(2)(D)(i)(I) for the 2008 ozone NAAQS.

Identification of Monitors Significantly Impacted by Maine Emissions in 2018

In the January 2015 guidance, EPA released preliminary ozone modeling results for 2018, based on emission 

reductions anticipated from previously adopted state and federal control programs.6 EPA used the CSAPR 

modeling approach to assess the effects of interstate transport on attainment and maintenance of the 2008 

 

5 Based on the upholding of the CSAPR framework by the Supreme Court, EPA’s actions will focus on what it

considers to be cost-effective actions that are achievable by the start of the 2017 ozone season, when moderate areas 

are required to achieve compliance with the 2008 ozone NAAQS.

6 EPA has posted a memorandum, technical support document, and related data files documenting the January 2015 

preliminary modeling at: http://www.epa.gov/airtransport/ozonetransportNAAQS.html. 
Page | 3

ozone NAAQS. EPA modeled 2011 base year and 2018 projected emissions using the Comprehensive Air 

Quality Model with Extensions (CAMx), version 6.10 and 2011 meteorological data. Results from 2011 and 

2018 were used to develop a relative response factor (RRF) for each ozone monitoring site, which is the 

fractional change in the modeled 8-hour daily maximum ozone levels between the two years.

EPA then used a methodology described in its draft guidance for attainment demonstration modeling to 

identify ozone monitoring sites that it projected to be in nonattainment or have maintenance issues with the 

2008 ozone NAAQS in 2018.7 The approach entailed calculating the maximum and average of the monitored 

ozone design values for the five years centered on the 2011 base year (2009 – 2013) for each ozone monitor. 

Those values were multiplied by the corresponding RRFs to project average and maximum 2018 design 

values. Sites with average projected 2018 design value that exceeded 75 ppb, the 2008 ozone NAAQS, were 

identified as projected 2018 nonattainment monitors. Monitoring sites with 2018 average projected design 

values below the NAAQS but with 2018 maximum projected design values that exceeded the NAAQS were 

identified as projected 2018 maintenance monitors.

The EPA also performed nationwide state-level ozone source apportionment modeling using the CAMx 

Ozone Source Apportionment Technology/Anthropogenic Precursor Culpability Analysis (OSAT/APCA) 

technique to quantify the contribution of 2018 oxides of nitrogen (NOx) and volatile organic compound 

(VOC) emissions from all sources in each state to projected 2018 ozone concentrations at monitoring sites. If 

a state’s interstate transport impact in 2018 equaled or exceeded the screening threshold of 1% of the ozone 

NAAQS at a nonattainment or maintenance monitor in another state, then the upwind state is “linked” to the 

downwind state, potentially requiring additional emission reductions to meet the CAA good neighbor 

provision. If the modeling shows a state does not contribute above the screening threshold to any downwind 

problem monitor, then EPA concludes that no further action is needed to comply with the CAA good 

neighbor provision.

Table 1 summarizes EPA’s 2018 modeling results, showing Maine’s impacts at projected out-of-state 

nonattainment/maintenance monitors located in the eastern half of the country.

8 Emissions from Maine are 

projected to have a maximum impact in 2018 of 0.01 ppb at the monitor in Fairfield County Connecticut. 

Maine impacts at the monitors of concern are non-detects, well below the 1% screening threshold of 0.75 

ppb for the 2008 NAAQS. Therefore, in accordance with EPA’s January 2015 guidance, Maine complies 

with the CAA §110(a)(2)(D)(i)(I) good neighbor provisions for the 2008 ozone NAAQS. 

Based on the EPA’s modeling described above, Maine’s emissions are not projected to have significant 

impacts at any monitors located at nonattainment or maintenance areas in other states. 

 

7 EPA, “Modeling Guidance for Demonstrating Attainment of Air Quality Goals for Ozone, PM2.5, and Regional

Haze- December 2014 DRAFT” http://www.epa.gov/scram001/guidance/guide/Draft_O3-PMRH_Modeling_Guidance2014.pdf

8 EPA included Texas in its analysis of eastern states.
Page | 4

Table 1: Maine Contributions to Monitors Projected by EPA Modeling to Have

2018 Nonattainment or Maintenance Issues

2018

Nonattainment Areas 

Contributions (ppb)

Maintenance Areas 

Contributions (ppb)

Contribution 

as a Percent of 

Average Daily 

Value

State

Average Design 

Value Monitoring Site Maine Maine

CT 76.7 90013007 -

CT 77.5 90019003 0.01 0.01%

CT 74.1 90010017 -

CT 75.8 90099002 -

KY 73.7 211110067 -

MD 79.4 240251001 -

MI 74.5 260050003 -

MO 74.1 291831002 -

NJ 72.3 340071001 -

NJ 74.0 340150002 -

NY 78.2 361030002 -

NY 74.6 360850067 -

PA 74.7 421010024 -

TX 80.5 480391004 -

TX 77.0 481210034 -

TX 76.4 482010024 -

TX 76.6 482011034 -

TX 77.7 482011039 -

TX 79.7 484392003 -

TX 78.3 484393009 -

TX 75.0 480850005 -

TX 73.7 481130069 -

TX 75.2 481130075 -

TX 75.1 481211032 -

TX 75.4 482010029 -

TX 75.0 482010055 -

TX 75.5 484390075 -

TX 74.2 484393011 -

WI 75.4 551170006 -

Summary and Conclusions

This SIP revision addresses Maine’s “good neighbor” obligations under CAA §110(a)(2)(D)(i)(I), evaluating

whether Maine emissions contribute significantly to nonattainment in, or interfere with maintenance by, any

other state regarding the 2008 ozone NAAQS. DEP’s analyses included a review of EPA’s January 2015 

guidance memorandum and preliminary transport modeling results.
Page | 5

As described earlier, DEP’s analyses resulted in the following findings: EPA’s preliminary transport 

modeling for 2018 show ozone contributions from Maine emissions are below the significant level at all outof-state monitors modeled as either nonattainment or maintenance concerns in 2018.

Based on the analyses described in this SIP revision, DEP concludes Maine complies, and will remain in 

compliance with the good neighbor provisions of CAA §110(a)(2)(D)(i)(I) for the 2008 ozone NAAQS.