[Federal Register Volume 83, Number 69 (Tuesday, April 10, 2018)]
[Proposed Rules]
[Pages 15336-15343]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2018-07231]


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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 52

[EPA-R01-OAR-2014-0604; A-1-FRL-9976-36--Region 1]


Air Plan Approval; Vermont; Infrastructure Requirement for the 
2010 Sulfur Dioxide National Ambient Air Quality Standard

AGENCY: Environmental Protection Agency (EPA).

ACTION: Proposed rule.

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SUMMARY: The Environmental Protection Agency (EPA) is proposing to 
approve the remaining portion of a November 2, 2015 State 
Implementation Plan (SIP) revision submitted by the State of Vermont. 
This revision addresses the interstate transport requirements of the 
Clean Air Act (CAA), referred to as the good neighbor provision, with 
respect to the primary 2010 sulfur dioxide (SO2) national 
ambient air quality standard (NAAQS). This action proposes to approve 
Vermont's demonstration that the State is meeting its obligations 
regarding the transport of SO2 emissions into other states. 
This action is being taken under the Clean Air Act.

DATES: Written comments must be received on or before May 10, 2018.

ADDRESSES: Submit your comments, identified by Docket ID No. EPA-R01-
OAR-2014-0604 at www.regulations.gov, or via email to 
[email protected]. For comments submitted at Regulations.gov, follow 
the online instructions for submitting comments. Once submitted, 
comments cannot be edited or removed from Regulations.gov. For either 
manner of submission, the EPA may publish any comment received to its 
public docket. Do not submit electronically any information you 
consider to be Confidential Business Information (CBI) or other 
information whose disclosure is restricted by statute. Multimedia 
submissions (audio, video, etc.) must be accompanied by a written 
comment. The written comment is considered the official comment and 
should include discussion of all points you wish to make. The EPA will 
generally not consider comments or comment contents located outside of 
the primary submission (i.e., on the web, cloud, or other file sharing 
system). For additional submission methods, please contact the person 
identified in the FOR FURTHER INFORMATION CONTACT section. For the full 
EPA public comment policy, information about CBI or multimedia 
submissions, and general guidance on making effective comments, please 
visit www.epa.gov/dockets/commenting-epa-dockets. Publicly available 
docket materials are available at www.regulations.gov or at the U.S. 
Environmental Protection Agency, EPA New England Regional Office, 
Office of Ecosystem Protection, Air Quality Planning Unit, 5 Post 
Office Square--Suite 100, Boston, MA. EPA requests that if at all 
possible, you contact the contact listed in the FOR FURTHER INFORMATION 
CONTACT section to schedule your inspection. The Regional Office's 
official hours of business are Monday through Friday, 8:30 a.m. to 4:30 
p.m., excluding legal holidays.

FOR FURTHER INFORMATION CONTACT: Donald Dahl, Air Permits, Toxics, and 
Indoor Programs Unit, U.S. Environmental Protection Agency, EPA New 
England Regional Office, 5 Post Office Square--Suite 100, (Mail code 
OEP05-2), Boston, MA 02109--3912, tel. (617) 918-1657; or by email at 
[email protected].

SUPPLEMENTARY INFORMATION: Throughout this document whenever ``we,'' 
``us,'' or ``our'' is used, we mean EPA. The following outline is 
provided to aid in locating information in this preamble.

Table of Contents

I. Background
II. State Submittal
III. Summary of the Proposed Action
IV. Section 110(A)(2)(D)(i)(I)--Interstate Transport
    A. General Requirements and Historical Approaches for Criteria 
Pollutants
    B. Approach for Addressing the Interstate Transport Requirements 
of the 2010 Primary SO2 NAAQS in Vermont
V. Interstate Transport Demonstration for SO2 Emissions
    A. Prong 1 Analysis--Significant Contribution to SO2 
Nonattainment
    1. Impact on the Central New Hampshire Nonattainment Area
    2. SO2 Emissions Trends
    3. SO2 Ambient Air Quality
    4. Federally Enforceable Regulations Specific to SO2 
and Permitting Requirements
    5. Conclusion
    B. Prong 2 Analysis--Interference With Maintenance of the NAAQS
VI. Proposed Action
VII. Statutory and Executive Order Reviews

I. Background

    On June 22, 2010 (75 FR 35520), EPA promulgated a revised primary 
NAAQS for SO2 at a level of 75 ppb, based on a 3-year 
average of the annual 99th percentile of 1-hour daily maximum 
concentrations. Pursuant to section 110(a)(1) of the CAA, states are 
required to submit SIPs meeting the applicable requirements of section 
110(a)(2) within three years after promulgation of a new

[[Page 15337]]

or revised NAAQS, or within such shorter period as EPA may 
prescribe.\1\ These SIPs, which EPA has historically referred to as 
``infrastructure SIPs,'' are to provide for the ``implementation, 
maintenance, and enforcement'' of such NAAQS, and the requirements are 
designed to ensure that the structural components of each state's air 
quality management program are adequate to meet the state's 
responsibilities under the CAA. A detailed history, interpretation, and 
rationale of these SIPs and their requirements can be found in, among 
other documents, EPA's May 13, 2014 proposed rule titled, 
``Infrastructure SIP requirements for the 2008 Lead NAAQS,'' in the 
section ``What is the scope of this rulemaking?'' (see 79 FR 27241 at 
27242-27245). As noted above, section 110(a) of the CAA imposes an 
obligation upon states to submit to EPA a SIP submission for a new or 
revised NAAQS. The content of individual state submissions may vary 
depending upon the facts and circumstances, and may also vary depending 
upon what provisions the state's approved SIP already contains.
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    \1\ This requirement applies to both primary and secondary 
NAAQS, but EPA's approval in this document applies only to the 2010 
primary NAAQS for SO2 because EPA did not establish in 
2010 a new secondary NAAQS for SO2.
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    On November 2, 2015, the Vermont Department of Environmental 
Conservation (VT DEC) submitted proposed revisions to its SIP, 
certifying that its SIP meets the requirements of section 110(a)(2) of 
the CAA with respect to the 2008 ozone, 2010 NO2, and 2010 
SO2 primary NAAQS. On June 27, 2017 (82 FR 29005), EPA 
approved VT DEC's certification that its SIP was adequate to meet most 
of the program elements required by section 110(a)(2) of the CAA with 
respect to the 2008 ozone, 2010 NO2, and 2010 SO2 
NAAQS. EPA conditionally approved the State's submission in relation to 
subsections (C), (D), and (J) of CAA section 110(a)(2) in relation to 
the prevention of significant deterioration permit program.
    However, at that time, EPA did not take action on VT DEC's 
certification that its SIP met the requirements of section 
110(a)(2)(D)(i)(I) for the 2010 primary SO2 NAAQS. EPA is 
now proposing to approve VT DEC's November 2, 2015 certification that 
its SIP meets the requirements of CAA section 110(a)(2)(D)(i)(I), for 
purposes of the 2010 SO2 NAAQS.

II. State Submittal

    Vermont presented several facts in its SIP submission on the effect 
of SO2 emissions from sources within Vermont on downwind and 
neighboring states' SO2 nonattainment areas and those 
states' ability to maintain the 2010 SO2 NAAQS. The SIP 
submission notes statewide SO2 emissions from point sources 
in 2011 were less than 500 tons total. Vermont also included two data 
points regarding ambient monitoring data in its November 2015 
submittal. First, the design value from an instate monitor in Rutland 
for the period 2012-2014 was 13 ppb, which is only 17% of the 2010 
SO2 standard. Vermont also stated the most recent design 
value (2013) for the central New Hampshire nonattainment area was 23 
ppb. Finally, Vermont states in its SIP submission that ``[n]o source 
or sources within Vermont have been identified as contributing 
significantly to nonattainment in any other state or are the subject of 
an active finding under section 126 of the CAA with respect to 
SO2 or any other air pollutant.''

III. Summary of the Proposed Action

    This proposed approval of Vermont's November 2, 2015 SIP submission 
addressing interstate transport of SO2 is intended to show 
that the State is meeting its obligations regarding CAA section 
110(a)(2)(D)(i)(I) relative to the primary 2010 SO2 
NAAQS.\2\ Interstate transport requirements for all NAAQS pollutants 
prohibit any source, or other type of emissions activity, in one state 
from emitting any air pollutant in amounts that will contribute 
significantly to nonattainment, or interfere with maintenance, of the 
NAAQS in another state. As part of this analysis, and as explained in 
detail below, EPA has taken several approaches to addressing interstate 
transport in other actions based on the characteristics of the 
pollutant, the interstate problem presented by emissions of that 
pollutant, the sources that emit the pollutant, and the information 
available to assess transport of that pollutant.
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    \2\ This proposed approval of Vermont's SIP submission under CAA 
section 110(a)(2)(D)(i)(I) is based on the information contained in 
the administrative record for this action, and does not prejudge any 
other future EPA action that may make other determinations regarding 
Vermont's air quality status. Any such future actions, such as area 
designations under any NAAQS, will be based on their own 
administrative records and EPA's analyses of information that 
becomes available at those times. Future available information may 
include, and is not limited to, monitoring data and modeling 
analyses conducted pursuant to EPA's Data Requirements Rule (80 FR 
51052, August 21, 2015) and information submitted to EPA by states, 
air agencies, and third-party stakeholders such as citizen groups 
and industry representatives.
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    Despite being emitted from a similar universe of point and nonpoint 
sources, interstate transport of SO2 is unlike the transport 
of fine particulate matter (PM2.5) or ozone that EPA has 
addressed in other actions, in that SO2 is not a regional 
mixing pollutant that commonly contributes to widespread nonattainment 
of the SO2 NAAQS over a large, multi-state area. While in 
certain respects transport of SO2 is more analogous to the 
transport of lead (Pb) because SO2's and Pb's physical 
properties result in localized impacts very near the emissions source, 
in another respect the physical properties and release height of 
SO2 are such that impacts of SO2 do not 
experience the same sharp decrease in ambient concentrations as rapidly 
and as nearby as they do for Pb. While emissions of SO2 
travel farther and have sufficiently wider-ranging impacts than 
emissions of Pb such that it is reasonable to require a different 
approach for assessing SO2 transport than assessing Pb 
transport, the differences are not significant enough to treat 
SO2 in a manner similar to the way in which EPA treats and 
analyzes regional transport pollutants such as ozone or 
PM2.5.
    Put simply, a different approach is needed for interstate transport 
of SO2 than the approach used for the other pollutants 
identified above: The approaches EPA has adopted for Pb transport are 
too tightly circumscribed to the source, and the approaches for ozone 
or PM2.5 transport are too regionally focused. 
SO2 transport is therefore a unique case, and EPA's 
evaluation of whether Vermont has met is transport obligations in 
relation to SO2 was accomplished in several discrete steps.
    First, EPA evaluated the universe of sources in Vermont likely to 
be responsible for SO2 emissions that could contribute to 
interstate transport. An assessment of the 2014 National Emissions 
Inventory (NEI) for Vermont made it clear that the vast majority of 
SO2 emissions in Vermont are from fuel combustion at point 
and nonpoint sources,\3\ and therefore it would be reasonable to 
evaluate the downwind impacts of emissions from these two fuel 
combustion source categories, combined, in order to help determine 
whether the State has met is transport obligations.
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    \3\ See EPA's web page, www.epa.gov/air-emissions-inventories/national-emissions-inventory-nei, for a description of what types of 
sources of air emissions are considered point and nonpoint sources.
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    Second, EPA selected a spatial scale--essentially, the geographic 
area and distance around the point sources in which we could reasonably 
expect SO2 impacts to occur--that would be

[[Page 15338]]

appropriate for its analysis, ultimately settling on utilizing an 
``urban scale'' with dimensions from 4 to 50 kilometers from point and 
nonpoint sources, given the usefulness of that range in assessing 
trends in both area-wide air quality and the effectiveness of large-
scale pollution control strategies. As such, EPA utilized an assessment 
up to 50 kilometers from fuel-combustion sources in order to assess 
trends in area-wide air quality that might have an impact on the 
transport of SO2 from Vermont to downwind states.
    Third, EPA assessed all available data at the time of this 
rulemaking regarding SO2 emissions in Vermont and their 
possible impacts in downwind states, including: (1) SO2 
ambient air quality; (2) SO2 emissions and SO2 
emissions trends; (3) SIP-approved SO2 regulations and 
permitting requirements; and (4) other SIP-approved or federally-
promulgated regulations which may yield reductions of SO2 at 
Vermont's fuel-combustion point and nonpoint sources.
    Fourth, using the universe of information identified in steps 1-3 
(i.e., emissions sources, spatial scale and available data, and 
enforceable regulations), EPA then conducted an analysis under CAA 
section 110(a)(2)(D)(i)(I) to evaluate whether or not fuel-combustion 
sources in Vermont would significantly contribute to SO2 
nonattainment in other states, and then whether emissions from those 
sources would interfere with maintenance of the SO2 NAAQS in 
other states.
    Based on the analysis provided by the State in its November 2, 2015 
SIP submission and EPA's assessment of the information discussed at 
length below, EPA proposes to find that sources or other emissions 
activity within Vermont will not contribute significantly to 
nonattainment, nor will they interfere with maintenance of the 2010 
primary SO2 NAAQS in any other state.

IV. Section 110(a)(2)(D)(i)(I)--Interstate Transport

A. General Requirements and Historical Approaches for Criteria 
Pollutants

    Section 110(a)(2)(D)(i)(I) requires SIPs to include provisions 
prohibiting any source or other type of emissions activity in one state 
from emitting any air pollutant in amounts that will contribute 
significantly to nonattainment, or interfere with maintenance, of the 
NAAQS in another state. The two clauses of this section are referred to 
as prong 1 (significant contribution to nonattainment) and prong 2 
(interference with maintenance of the NAAQS).
    EPA's most recent infrastructure SIP guidance, the September 13, 
2013 ``Guidance on Infrastructure State Implementation Plan (SIP) 
Elements under Clean Air Act Sections 110(a)(1) and 110(a)(2),'' did 
not explicitly include criteria for how the Agency would evaluate 
infrastructure SIP submissions intended to address section 
110(a)(2)(D)(i)(I).\4\ With respect to certain pollutants, such as 
ozone and particulate matter, EPA has addressed interstate transport in 
eastern states in the context of regional rulemaking actions that 
quantify state emission reduction obligations.\5\ In other actions, 
such as EPA action on western state SIPs addressing ozone and 
particulate matter, EPA has considered a variety of factors on a case-
by-case basis to determine whether emissions from one state interfere 
with the attainment and maintenance of the NAAQS in another state. In 
such actions, EPA has considered available information such as current 
air quality, emissions data and trends, meteorology, and topography.\6\
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    \4\ At the time the September 13, 2013 guidance was issued, EPA 
was litigating challenges raised with respect to its Cross State Air 
Pollution Rule (``CSAPR''), 76 FR 48208 (August 8, 2011), designed 
to address the CAA section 110(a)(2)(D)(i)(I) interstate transport 
requirements with respect to the 1997 ozone and the 1997 and 2006 
PM2.5 NAAQS. CSAPR was vacated and remanded by the D.C. 
Circuit in 2012 pursuant to EME Homer City Generation, L.P. v. EPA, 
696 F.3d 7. EPA subsequently sought review of the D.C. Circuit's 
decision by the Supreme Court, which was granted in June 2013. As 
EPA was in the process of litigating the interpretation of section 
110(a)(2)(D)(i)(I) at the time the infrastructure SIP guidance was 
issued, EPA did not issue guidance specific to that provision. The 
Supreme Court subsequently vacated the D.C. Circuit's decision and 
remanded the case to that court for further review. 134 S.Ct. 1584 
(2014). On July 28, 2015, the D.C. Circuit issued a decision 
upholding CSAPR, but remanding certain elements for reconsideration. 
795 F.3d 118.
    \5\ NOX SIP Call, 63 FR 57371 (October 27, 1998); 
Clean Air Interstate Rule (CAIR), 70 FR 25172 (May 12, 2005); CSAPR, 
76 FR 48208 (August 8, 2011).
    \6\ See, e.g., Approval and Promulgation of Implementation 
Plans; State of California; Interstate Transport of Pollution; 
Significant Contribution to Nonattainment and Interference With 
Maintenance Requirements, Proposed Rule, 76 FR 146516, 14616-14626 
(March 17, 2011); Final Rule, 76 FR 34872 (June 15, 2011); Approval 
and Promulgation of State Implementation Plans; State of Colorado; 
Interstate Transport of Pollution for the 2006 24-Hour 
PM2.5 NAAQS, Proposed Rule, 80 FR 27121, 27124-27125 (May 
12, 2015); Final Rule, 80 FR 47862 (August 10, 2015).
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    For other pollutants such as Pb, EPA has suggested the applicable 
interstate transport requirements of section 110(a)(2)(D)(i)(I) can be 
met through a state's assessment as to whether or not emissions from Pb 
sources located in close proximity to its borders have emissions that 
impact a neighboring state such that they contribute significantly to 
nonattainment or interfere with maintenance in that state. For example, 
EPA noted in an October 14, 2011 memorandum titled, ``Guidance on 
Infrastructure SIP Elements Required Under Sections 110(a)(1) and 
110(a)(2) for the 2008 Pb NAAQS,'' \7\ that the physical properties of 
Pb prevent its emissions from experiencing the same travel or formation 
phenomena as PM2.5 or ozone, and there is a sharp decrease 
in Pb concentrations, at least in the coarse fraction, as the distance 
from a Pb source increases. Accordingly, while it may be possible for a 
source in a state to emit Pb in a location and in quantities that may 
contribute significantly to nonattainment in, or interfere with 
maintenance by, any other state, EPA anticipates that this would be a 
rare situation, e.g., where large sources are in close proximity to 
state boundaries.\8\ Our rationale and explanation for approving the 
applicable interstate transport requirements under section 
110(a)(2)(D)(i)(I) for the 2008 Pb NAAQS, consistent with EPA's 
interpretation of the October 14, 2011 guidance document, can be found 
in, among other instances, the proposed approval and a subsequent final 
approval of interstate transport SIPs submitted by Illinois, Michigan, 
Minnesota, and Wisconsin.\9\
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    \7\ https://www3.epa.gov/ttn/naaqs/aqmguide/collection/cp2/20111014_page_lead_caa_110_infrastructure_guidance.pdf.
    \8\ Id. at pp 7-8.
    \9\ See 79 FR 27241 at 27249 (May 13, 2014) and 79 FR 41439 
(July 16, 2014).
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B. Approach for Addressing the Interstate Transport Requirements of the 
2010 Primary SO2 NAAQS in Vermont

    This document describes EPA's evaluation of Vermont's conclusion 
contained in the State's November 2, 2015 infrastructure SIP submission 
that the State satisfies the requirements of CAA section 
110(a)(2)(D)(i)(I) for the 2010 SO2 NAAQS.\10\
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    \10\ EPA notes that the evaluation of other states' satisfaction 
of section 110(a)(2)(D)(i)(I) for the 2010 SO2 NAAQS can 
be informed by similar factors found in this proposed rulemaking, 
but may not be identical to the approach taken in this or any future 
rulemaking for Vermont, depending on available information and 
state-specific circumstances.
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    As previously noted, section 110(a)(2)(D)(i)(I) requires an 
evaluation of any source or other type of emissions activity in one 
state and how emissions from these sources or activities may impact air 
quality in other states. As the analysis contained in Vermont's 
submittal demonstrates, a state's obligation to demonstrate that it is 
meeting section 110(a)(2)(D)(i)(I) cannot

[[Page 15339]]

be based solely on the fact that there are no data requirements rule 
(DRR) sources within the state. Therefore, EPA believes that a 
reasonable starting point for determining which sources and emissions 
activities in Vermont are likely to impact downwind air quality with 
respect to the SO2 NAAQS is by using information in the 
NEI.\11\ The NEI is a comprehensive and detailed estimate of air 
emissions of criteria pollutants, criteria precursors, and hazardous 
air pollutants from air emissions sources, and is updated every three 
years using information provided by the states. At the time of this 
rulemaking, the most recently available dataset is the 2014 NEI, and 
the state summary for Vermont is included in the table below.
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    \11\ https://www.epa.gov/air-emissions-inventories/national-emissions-inventory.

            Table 1--Summary of 2014 NEI SO2 Data for Vermont
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                                                               Emissions
                          Category                             (tons per
                                                                 year)
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Fuel Combustion: Electric Utilities.........................           2
Fuel Combustion: Industrial.................................         442
Fuel Combustion: Other......................................         891
Waste Disposal and Recycling................................          61
Highway Vehicles............................................          65
Off-Highway.................................................          30
Miscellaneous...............................................          10
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  Total.....................................................       1,501
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    The EPA observes that according to the 2014 NEI, the vast majority 
of SO2 emissions in Vermont originate from fuel combustion 
at point and nonpoint sources. Therefore, an assessment of Vermont's 
satisfaction of all applicable requirements under section 
110(a)(2)(D)(i)(I) of the CAA for the 2010 SO2 NAAQS may 
reasonably be based upon evaluating the downwind impacts of emissions 
from the combined fuel combustion categories (i.e., electric utilities, 
industrial processes, and other sources \12\).
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    \12\ The ``other'' category of fuel combustion in Vermont is 
comprised almost entirely of residential heating through fuel oil 
and wood combustion.
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    The definitions contained in Appendix D to 40 CFR part 58 are 
helpful indicators of the travel and formation phenomenon for 
SO2 originating from stationary sources in its 
stoichiometric gaseous form in the context of the 2010 primary 
SO2 NAAQS. Notably, section 4.4 of Appendix D titled, 
``Sulfur Dioxide (SO2) Design Criteria'' provides 
definitions for SO2 Monitoring Spatial Scales for 
microscale, middle scale, neighborhood, and urban scale monitors. The 
microscale includes areas in close proximity to SO2 point 
and area sources, and those areas extend approximately 100 meters from 
a facility. The middle scale generally represents air quality levels in 
areas 100 meters to 500 meters from a facility, and may include 
locations of maximum expected short-term concentrations due to the 
proximity of major SO2 point, area, and non-road sources. 
The neighborhood scale characterizes air quality conditions between 0.5 
kilometers and 4 kilometers from a facility, and emissions from 
stationary and point sources may under certain plume conditions, result 
in high SO2 concentrations at this scale. Lastly, the urban 
scale is used to estimate concentrations over large portions of an 
urban area with dimensions of 4 to 50 kilometers from a facility, and 
such measurements would be useful for assessing trends and 
concentrations in area-wide air quality, and hence, the effectiveness 
of large-scale pollution control strategies. Based on these definitions 
contained in EPA's own regulations, we believe that it is appropriate 
to examine the impacts of emissions from electric utilities and 
industrial processes in Vermont in distances ranging from 0 km to 50 km 
from the facility. In other words, SO2 emissions from 
stationary sources in the context of the 2010 primary NAAQS do not 
exhibit the same long-distance travel, regional transport or formation 
phenomena as either ozone or PM2.5, but rather, these 
emissions behave more like Pb with localized dispersion. Therefore, an 
assessment up to 50 kilometers from potential sources would be useful 
for assessing trends and SO2 concentrations in area-wide air 
quality.\13\
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    \13\ EPA recognizes in Appendix A.1 titled, ``AERMOD (AMS/EPA 
Regulatory Model)--'' of Appendix W to 40 CFR part 51 that the model 
is appropriate for predicting SO2 up to 50 kilometers.
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    The largest category of SO2 emissions in Table 1 is for 
``other'' fuel combustion sources. The majority of emissions in this 
category is from residential fuel combustion (758 tons per year), or 
50% of the total statewide SO2 emissions for 2014. 
Residential homes combusting fuel are considered nonpoint sources. For 
any state where the SO2 contribution from nonpoint sources 
make up a majority of all statewide SO2 emissions, EPA 
believes it is reasonable to evaluate any regulations intended to 
address fuel oil, specifically with respect to the sulfur content in 
order to determine interstate transport impacts from the category of 
``other'' sources of fuel combustion.
    Our current implementation strategy for the 2010 primary 
SO2 NAAQS includes the flexibility to characterize air 
quality for stationary sources via either data collected at ambient air 
quality monitors sited to capture the points of maximum concentration, 
or air dispersion modeling.\14\ Our assessment of SO2 
emissions from fuel combustion categories in the State and their 
potential impacts on neighboring states are informed by all available 
data at the time of this rulemaking, and include: SO2 
ambient air quality; SO2 emissions and SO2 
emissions trends; SIP-approved SO2 regulations and 
permitting requirements; and, other SIP-approved or federally 
promulgated regulations which may yield reductions of SO2.
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    \14\ https://www.epa.gov/so2-pollution/2010-1-hour-sulfur-dioxide-so2-primary-national-ambient-air-quality-standards-naaqs.
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V. Interstate Transport Demonstration for SO2 Emissions

A. Prong 1 Analysis--Significant Contribution to SO2 Nonattainment

    Prong 1 of the good neighbor provision requires state plans to 
prohibit emissions that will significantly contribute to nonattainment 
of a NAAQS in another state. In order to evaluate Vermont's 
satisfaction of prong 1, EPA evaluated the State's SIP submission in 
relation to the following five factors: (1) The impact on the Central 
New Hampshire Nonattainment Area; (2) SO2 emission trends 
for Vermont and neighboring states; (3) SO2 ambient air 
quality data; (4) SIP-approved regulations specific to SO2 
emissions and permit requirements; and (5) other SIP-approved or 
federally-enforceable regulations that, while not directly intended to 
address or reduce SO2 emissions, may yield reductions of the 
pollutant. A detailed discussion of each of these factors is below.
1. Impact on the Central New Hampshire Nonattainment Area
    The nearest nonattainment area to Vermont for the 2010 
SO2 NAAQS is in New Hampshire. On August 5, 2013, EPA 
designated the Central New Hampshire Nonattainment Area, an area 
surrounding Merrimack Station, a coal-fired power plant, as 
nonattainment for the 2010 SO2 NAAQS. See 78 FR 47191. On 
September 28, 2017, EPA proposed approval of New Hampshire's attainment 
plan for this nonattainment area. See 82 FR45242. The State's plan did 
not rely on any reductions in SO2 emissions from sources in 
Vermont to demonstrate the Central New Hampshire Nonattainment Area 
will attain the 2010 SO2 NAAQS by the 2018

[[Page 15340]]

attainment date. Furthermore, no comments received on EPA's proposed 
approval of the State's plan suggest SO2 emissions from 
sources in Vermont should be considered in any attainment 
demonstration.\15\
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    \15\ See docket for Air Plan Approval; NH; Attainment Plan for 
the Central New Hampshire 2010 1-Hour SO2 Nonattainment 
Area at https://www.regulations.gov/docket?D=EPA-R01-OAR-2017-0083.
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2. SO2 Emissions Trends
    As noted above, EPA's approach for addressing the interstate 
transport of SO2 in Vermont is based upon emissions from 
fuel combustion at electric utilities, industrial sources, and 
residential heating. As part of the SIP submittal, Vermont observed 
that, in accordance with the most recently available designations 
guidance at the time,\16\ there were no facilities in Vermont with 
reported actual emissions greater than or equal to 500 tons per year of 
SO2 in 2014.
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    \16\ March 24, 2011 guidance document titled, ``Area 
Designations for the 2010 Revised Primary Sulfur Dioxide National 
Ambient Air Quality Standards.'' See, e.g., http://dnr.wi.gov/topic/AirQuality/documents/SO2DesignationsGuidance2011.pdf.
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    According to the 2014 NEI data, the highest SO2 
emissions from a single point source was 158 tons from Agrimark in 
Middlebury, Vermont and the next largest emitter of SO2 from 
an industrial or electric generating facility in Vermont was Fibermark, 
located in Brattleboro, which emitted 12 tons of SO2.
    As demonstrated by the data in Table 2, statewide SO2 
emissions in Vermont and in its three neighboring states, New 
Hampshire, Massachusetts and New York, have significantly decreased 
over time. This decreasing trend should continue into the near future 
in Vermont, New York, and Massachusetts as these three states have 
adopted strategies to lower the sulfur content (by weight) of fuel 
oil.\17\ By July 1, 2018, the home heating oil in these three states 
will be limited to 15 parts per million (ppm) of sulfur by weight.
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    \17\ On May 22, 2012, EPA approved Vermont's low sulfur fuel 
regulation. See 77 FR 30212. On September 19, 2013, EPA approved 
Massachusetts' low sulfur fuel regulation. See 78 FR 57487. On 
August 8, 2012, EPA approved New York's low sulfur fuel statute. See 
77 FR 51915.

    Table 2--Statewide SO2 Data (Tons per Year) for Vermont, New Hampshire, New York, and Massachusetts \18\
----------------------------------------------------------------------------------------------------------------
                                                                                                   % Change from
              State                    2000            2005            2010            2016        2000 to 2016
----------------------------------------------------------------------------------------------------------------
Vermont.........................           9,438           7,038           3,659           1,455             -85
New Hampshire...................          68,768          63,634          35,716           5,462             -92
Massachusetts...................         208,146         139,937          57,892          13,518             -94
New York........................         543,868         386,568         170,247          59,520             -89
----------------------------------------------------------------------------------------------------------------

3. SO2 Ambient Air Quality
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    \18\ See Air Pollution Emissions Trend Data at https://www.epa.gov/air-emissions-inventories/air-pollutant-emissions-trends-data.
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    Data collected at an ambient air quality monitor located in 
Rutland, Vermont indicates that the monitored values of SO2 
in the State have remained below the NAAQS. Relevant data from Air 
Quality Standards (AQS) Design Value (DV) \19\ reports for recent and 
complete 3-year periods are summarized in Table 3.
---------------------------------------------------------------------------

    \19\ A ``Design Value'' is a statistic that describes the air 
quality status of a given location relative to the level of the 
NAAQS. The interpretation of the 2010 primary SO2 NAAQS 
(set at 75 parts per billion [ppb]) including the data handling 
conventions and calculations necessary for determining compliance 
with the NAAQS can be found in Appendix T to 40 CFR part 50.

                       Table 3--Trend in SO2 Design Values for the AQS Monitor in Vermont
----------------------------------------------------------------------------------------------------------------
                                                                        2012-2014 DV  2013-2015 DV  2014-2016 DV
             AQS monitor site                    Monitor location           (ppb)         (ppb)         (ppb)
----------------------------------------------------------------------------------------------------------------
50-021-0002..............................  Rutland....................           13             9             6
----------------------------------------------------------------------------------------------------------------

    As shown in Table 3 above, the DVs at the Rutland monitor for all 
periods between 2012 and 2016 have decreased. The most recent DV for 
the Rutland monitor, covering the years 2014-2016, is 6 ppb, which is 
92% below the NAAQS.\20\
---------------------------------------------------------------------------

    \20\ There is another ambient monitor in Underhill, Vermont that 
only had a valid DV for 2014-2016. The DV was 2 ppb.
---------------------------------------------------------------------------

    However, the absence of a violating ambient air quality monitor 
within the State is insufficient to demonstrate that Vermont has met 
its interstate transport obligation. While the decreasing DVs may help 
to assist in characterizing air quality within Vermont, prong 1 of 
section 110(a)(2)(D)(i)(I) specifically addresses what effects sources 
within Vermont may have on air quality in neighboring states. 
Therefore, an evaluation and analysis of SO2 emissions data 
from facilities within the State, together with the potential effects 
of such emissions on ambient air quality in neighboring states, is 
appropriate.
    As previously discussed, EPA's definitions of spatial scales for 
SO2 monitoring networks indicate that the maximum impacts 
from stationary sources can be expected within 4 kilometers of such 
sources, and that distances up to 50 kilometers would be useful for 
assessing trends and concentrations in area-wide air quality. The only 
neighboring states within 50 km of an SO2 source in Vermont 
are Massachusetts, New Hampshire, and New York. As a result, no further 
analysis of other Northeast states was conducted for assessing the 
impacts of the interstate transport of SO2 pollution from 
facilities located in Vermont.
    There are four ambient SO2 monitors operating in 
Massachusetts, New Hampshire, and New York within 50 km of Vermont's 
border. These monitors are identified in Table 4, along with those 
monitors' DVs for SO2 in the last three, three-year periods. 
As shown in Table 4, SO2 DVs for these monitors are 
decreasing, with the exception of Wilmington, NY which increased 1 ppb 
between the 2013-2015 and 2014-2016

[[Page 15341]]

periods. The highest DV for the most recent DV period (between 2014-
2016) is 8% of the NAAQS.

                  Table 4--Trend in SO2 Design Values for AQS Monitors Within 50 km of Vermont
----------------------------------------------------------------------------------------------------------------
                                                                   2012-2014 DV    2013-2015 DV    2014-2016 DV
           AQS monitor site                 Monitor location           (ppb)           (ppb)           (ppb)
----------------------------------------------------------------------------------------------------------------
25-015-4002...........................  Quabbin Summit, MA......               6               5               4
33-011-5001...........................  Pack Monadock, NH.......               5               5               3
36-001-00012..........................  Loudonville Reservoir,                 8               8               6
                                         NY.
36-031-0003...........................  Wilmington, NY..........               3               3               4
----------------------------------------------------------------------------------------------------------------

4. Federally Enforceable Regulations Specific to SO2 and 
Permitting Requirements
    The State has various regulations to ensure that SO2 
emissions are not expected to substantially increase in the future. One 
notable example consists of the federally-enforceable conditions 
contained in Vermont's Air Pollution Control Regulation (APCR), 
Subchapter II, Section 5-221, ``Prohibition of Pollution Potential 
Materials in Fuel.'' This regulation, last approved by EPA into the SIP 
on May 22, 2012 (77 FR 30212) limits the amount of sulfur by weight in 
fuel oil. As discussed earlier in this document, the 2014 NEI indicates 
that the single largest, albeit diffuse, source category of 
SO2 emissions in Vermont is from fuel combustion for 
residential heating (891 tons). Starting on July 1, 2014 the sulfur 
content for home heating oil in Vermont was lowered to 500 parts per 
million (ppm), or 0.05% by weight. An additional reduction in the 
amount of SO2 emissions from the use of home heating oil 
will occur after July 1, 2018 when the sulfur content will be reduced 
from 500 ppm to 15 ppm or 0.0015% by weight, representing a 97% 
decrease in SO2 emissions from residential oil combustion.
    In addition, for the purposes of ensuring that SO2 
emissions at new or modified stationary sources in Vermont do not 
adversely impact air quality, the State's SIP-approved nonattainment 
new source review (NNSR) and prevention of significant deterioration 
(PSD) programs are contained in APCR, Subchapter V ``Review of New Air 
Contaminant Sources.'' This regulation ensures that SO2 
emissions due to new facility construction or to modifications at 
existing facilities will not adversely impact air quality in Vermont 
and will likely not adversely impact air quality in neighboring states.
    Finally, in addition to the State's SIP-approved regulations, EPA 
observes that facilities in Vermont are also subject to the federal 
requirements contained in regulations such as the National Emission 
Standards for Hazardous Air Pollutants for Major Sources: Industrial, 
Commercial, and Institutional Boilers and Process Heaters. This 
regulation reduces acid gases, which have a co-benefit of reducing 
SO2 emissions.
5. Conclusion
    As discussed, EPA has considered the following information in 
evaluating the State's satisfaction of the requirements of prong 1 of 
CAA section 110(a)(2)(D)(i)(I):
    (1) Past and projected SO2 emission trends demonstrate 
that ambient SO2 air quality issues in neighboring states 
are unlikely to occur due to SO2 emissions from sources in 
Vermont; and
    (2) Current SIP provisions and other federal programs will further 
reduce SO2 emissions from sources within Vermont.
    Based on the analysis provided by the State in its November 2, 2015 
SIP submission and based on each of the factors listed above, EPA 
proposes to find that any sources or other emissions activity within 
the State will not contribute significantly to nonattainment of the 
2010 primary SO2 NAAQS in any other state.

B. Prong 2 Analysis--Interference With Maintenance of the 
SO2 NAAQS

    Prong 2 of the good neighbor provision requires state plans to 
prohibit emissions that will interfere with maintenance of a NAAQS in 
another state. Given the continuing trend of decreased SO2 
emissions from sources within Vermont, EPA believes that a reasonable 
criterion to ensure that sources or other emissions activity 
originating within Vermont do not interfere with its neighboring 
states' ability to maintain the NAAQS consists of evaluating whether 
these decreases in emissions can be maintained over time.
    As shown in Table 2, above, state-wide SO2 emissions in 
Vermont, and the three neighboring states of Massachusetts, New 
Hampshire, and New York, have significantly decreased since 2000. Three 
of these states (Massachusetts, New York, and Vermont) have EPA-
approved low sulfur fuel oil requirements in their SIPs, requiring the 
sulfur content in home heating oil and other sources using distillate 
oil to be lowered by an additional 97% no later than July 1, 2018.\21\ 
According to 2014 NEI data, home heating oil is the largest category of 
SO2 emissions in three of the states, Vermont, 
Massachusetts, and New Hampshire. In New York, home heating oil was not 
the largest category of SO2 emissions in the 2014 NEI 
because the sulfur content in home heating oil was reduced by the State 
to 15 ppm on July 1, 2012.
---------------------------------------------------------------------------

    \21\ See 77 FR 30212 (May 22, 2012) for Vermont, 78 FR 57487 
(September 19, 2013) for Massachusetts, and 77 FR 51915 (August 8, 
2012), for New York.
---------------------------------------------------------------------------

    Utilizing home heating oil usage data from the U. S. Energy 
Information Administration and SIP-approved limits on the sulfur 
content of home heating oil, future SO2 emissions from home 
heating oil can be forecasted in Massachusetts and Vermont where the 
reduction in sulfur content to 15 ppm will not take effect until July 
1, 2018. According to EPA's guidance titled ``Compilation of Air 
Pollutant Emission Factors (AP42)'' Chapter 1.3 titled, ``Fuel Oil 
Combustion,'' \22\ more than 95% of the sulfur in fuel is converted to 
SO2. Table 5 provides the estimated SO2 emissions 
from Massachusetts and Vermont based on home heating oil usage in 2016 
and using the average annual home heating oil usage over a five-year 
period (2012-2016) \23\ to estimate the SO2 emissions in 
2019, when the sulfur content limit of 15 ppm will be in place for the 
entire calendar year heating season.
---------------------------------------------------------------------------

    \22\ See emission factors at https://www3.epa.gov/ttn/chief/ap42/ch01/final/c01s03.pdf.
    \23\ See residential fuel oil usage at https://www.eia.gov/dnav/pet/pet_cons_821usea_a_epd0_var_mgal_a.htm.

[[Page 15342]]



                             Table 5--Estimated SO2 Emissions From Home Heating Oil
----------------------------------------------------------------------------------------------------------------
                                                                                    Estimate of     Estimate of
                                                                   Average home    SO2 emissions   SO2 emissions
                                                                    heating oil     (tons) from     (tons) from
                              State                                 usage 2012-     households      households
                                                                    2016 (1,000      using oil       using oil
                                                                       gal)           (2016)          (2019)
 
----------------------------------------------------------------------------------------------------------------
Vermont.........................................................          70,701             254               8
Massachusetts...................................................         545,075           1,643              58
----------------------------------------------------------------------------------------------------------------

    While EPA does not currently have a way to quantify the impacts of 
multiple small, diffuse sources of SO2 on air quality in 
neighboring states, the drastic decrease in the allowable sulfur 
content in fuel oil in Vermont and the associated reductions in 
SO2 emissions, combined with the diffuse nature of these 
emissions, makes it unlikely that the current and future emissions from 
residential combustion of fuel oil are likely to lead to interference 
of maintenance of the NAAQS in a neighboring state. Specifically, by 
2018, in both Massachusetts and Vermont, the yearly SO2 
emissions from a household using 1,000 gallons of fuel oil will drop to 
under 0.21 pounds per year.
    As shown in Table 2, statewide SO2 emissions in Vermont 
have decreased over time. Several factors have caused this decrease in 
emissions, including the effective date of APCR Subchapter II, Section 
5-221 and industrial boilers switching to lower sulfur emitting fuels 
due to economics. According to emission trends data,\24\ SO2 
emissions from industrial sources decreased in Vermont by almost 90% 
from 2000 to 2016. The EPA believes that since actual SO2 
emissions from the facilities currently operating in Vermont have 
decreased between 2000 and 2016, this trend shows that emissions 
originating in Vermont are not expected to interfere with the 
neighboring states' ability to maintain the 2010 SO2 NAAQS.
---------------------------------------------------------------------------

    \24\ See Air Pollution Emissions Trend Data at https://www.epa.gov/air-emissions-inventories/air-pollutant-emissions-trends-data.
---------------------------------------------------------------------------

    As discussed above, EPA expects SO2 from point sources 
combusting fuel oil in Vermont will be lower in the future due to the 
lowering of the sulfur content in fuels as required by APCR Subchapter 
II, Section 5-221.
    Lastly, any future large sources of SO2 emissions will 
be addressed by Vermont's SIP-approved Prevention of Significant 
Deterioration (PSD) program. Future minor sources of SO2 
emissions will be addressed by the State's minor new source review 
permit program. The permitting regulations contained within these 
programs, along with the other factors already discussed, are expected 
to help ensure that ambient concentrations of SO2 in 
Massachusetts, New Hampshire or New York are not exceeded as a result 
of new facility construction or modification occurring in Vermont.
    It is also worth noting the air quality trends for ambient 
SO2 in the Northeastern United States.\25\ This region has 
experienced a 77% decrease in the annual 99th percentile of daily 
maximum 1-hour averages between 2000 and 2015 based on 46 monitoring 
sites, and the most recently available data for 2015 indicates that the 
mean value at these sites was 17.4 ppb, a value less than 25% of the 
NAAQS. When this trend is evaluated alongside the monitored 
SO2 concentrations within the State of Vermont as well as 
the SO2 concentrations recorded at monitors in 
Massachusetts, New York, and New Hampshire within 50 km of Vermont's 
border, EPA does not believe that sources or emissions activity from 
within Vermont are significantly different than the overall decreasing 
monitored SO2 concentration trend in the Northeast region. 
As a result, EPA finds it unlikely that sources or emissions activity 
from within Vermont will interfere with other states' ability to 
maintain the 2010 primary SO2 NAAQS.
---------------------------------------------------------------------------

    \25\ See https://www.epa.gov/air-trends/sulfur-dioxide-trends.
---------------------------------------------------------------------------

    Based on each of factors contained in the prong 2 maintenance 
analysis above, EPA proposes to find that sources or other emissions 
activity within the State will not interfere with maintenance of the 
2010 primary SO2 NAAQS in any other state.

VI. Proposed Action

    Considering the above analysis, EPA is proposing to approve 
Vermont's November 2, 2015 infrastructure submittal for the 2010 
primary SO2 NAAQS as it pertains to Section 
110(a)(2)(D)(i)(I) of the CAA. EPA is soliciting public comments on the 
issues discussed in this document. These comments will be considered 
before taking final action. Interested parties may participate in the 
Federal rulemaking procedure by submitting comments to this proposed 
rule by following the instructions listed in the ADDRESSES section of 
this Federal Register.

VII. Statutory and Executive Order Reviews

    Under the Clean Air Act, the Administrator is required to approve a 
SIP submission that complies with the provisions of the Act and 
applicable Federal regulations. 42 U.S.C. 7410(k); 40 CFR 52.02(a). 
Thus, in reviewing SIP submissions, EPA's role is to approve state 
choices, provided that they meet the criteria of the Clean Air Act. 
Accordingly, this proposed action merely approves state law as meeting 
Federal requirements and does not impose additional requirements beyond 
those imposed by state law. For that reason, this proposed action:
     Is not a significant regulatory action subject to review 
by the Office of Management and Budget under Executive Orders12866 (58 
FR 51735, October 4, 1993) and 13563 (76 FR 3821, January 21, 2011);
     Does not impose an information collection burden under the 
provisions of the Paperwork Reduction Act (44 U.S.C. 3501 et seq.);
     Is certified as not having a significant economic impact 
on a substantial number of small entities under the Regulatory 
Flexibility Act (5 U.S.C. 601 et seq.);
     Does not contain any unfunded mandate or significantly or 
uniquely affect small governments, as described in the Unfunded 
Mandates Reform Act of 1995 (Pub. L. 104-4);
     Does not have Federalism implications as specified in 
Executive Order 13132 (64 FR 43255, August 10, 1999);
     is not an economically significant regulatory action based 
on health or safety risks subject to Executive Order 13045 (62 FR 
19885, April 23, 1997);
     Is not a significant regulatory action subject to 
Executive Order 13211 (66 FR 28355, May 22, 2001);
     Is not subject to requirements of Section 12(d) of the 
National Technology Transfer and Advancement Act of 1995 (15 U.S.C. 272 
note) because

[[Page 15343]]

application of those requirements would be inconsistent with the Clean 
Air Act; and
     Does not provide EPA with the discretionary authority to 
address, as appropriate, disproportionate human health or environmental 
effects, using practicable and legally permissible methods, under 
Executive Order 12898 (59 FR 7629, February 16, 1994).
    In addition, the SIP is not approved to apply on any Indian 
reservation land or in any other area where EPA or an Indian tribe has 
demonstrated that a tribe has jurisdiction. In those areas of Indian 
country, the rule does not have tribal implications and will not impose 
substantial direct costs on tribal governments or preempt tribal law as 
specified by Executive Order 13175 (65 FR 67249, November 9, 2000).

List of Subjects in 40 CFR Part 52

    Environmental protection, Air pollution control, Incorporation by 
reference, Intergovernmental relations, Reporting and recordkeeping 
requirements, Sulfur oxides.

    Dated: April 2, 2018.
Alexandra Dunn,
Regional Administrator, EPA Region 1.
[FR Doc. 2018-07231 Filed 4-9-18; 8:45 am]
BILLING CODE 6560-50-P