November 30, 2011 

Lisa P. Jackson, Administrator 

U.S. Environmental Protection Agency 

Mail Code: 6102T 

1200 Pennsylvania Ave., NW 

Washington, DC 20460 

Attention: Docket ID No. EPA-HQ-OAR-2010-1059 

 Re: Draft Guidance for 1-Hour SO2 NAAQS SIP Submissions

Dear Administrator Jackson: 

The Northeast States for Coordinated Air Use Management (NESCAUM) offers the following 

comments on the U.S. Environmental Protection Agency’s (EPA’s) draft non-binding guidance, 

entitled “Guidance for 1-Hour SO2 NAAQS SIP Submissions,” as referenced in the October 3, 

2011 notice of availability published in the Federal Register (76 FR 61098-61100). NESCAUM 

is the regional association of air pollution control agencies representing Connecticut, Maine, 

Massachusetts, New Hampshire, New Jersey, New York, Rhode Island, and Vermont. 

The guidance is intended to assist state and tribal governments in preparing their 1-hour primary 

sulfur dioxide (SO2) National Ambient Air Quality Standard (NAAQS) State Implementation 

Plan (SIP) submittals, which are due June 3, 2013. While we appreciate EPA’s efforts to get 

guidance out in a timely manner, we are very concerned with the SIP-related impacts, both 

statutory and workload-related, that appear to be assumed in the draft. 

 

Areas designated as “unclassifiable” for SO2 are required to develop and submit attainment SIPs

within one year of designation. The workload burden required for SIP development is 

significant and would require states to shift resources from other program areas in order to 

complete attainment SIPs and maintenance plans, due by June 2013, for all areas, including those 

that might be able to be classified as “attainment” under an extended designation timeline. States 

are concerned about their ability to complete their work within the prescribed deadlines, as well 

as consequences for late submittals. EPA should explore how it can best provide states that are 

diligently attempting to complete their work the adequate time to do so. 

To this end, we urge EPA to judiciously use the authority granted it under Section 

107(d)(1)(B)(i) of the Clean Air Act by working closely with the states to determine where SO2

designations should be delayed for one year, until June 2013. This would selectively target those 

areas of a state where insufficient information exists to reasonably conclude there will be a 

nonattainment problem. The one-year extensions for these areas would: 
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NESCAUM - Docket I.D. # EPA-HQ-OAR-2010-1059 November 30, 2011

(1) conserve scarce state resources by allowing them to focus the earliest modeling and 

planning efforts on those areas and sources most likely to have or contribute to an SO2

NAAQS problem; 

(2) allow states and EPA more time to generate and analyze data to inform final designations 

in those areas likely attaining the SO2 NAAQS; 

(3) provide states with additional time to complete the modeling and permit revisions 

necessary to demonstrate attainment with the SO2 NAAQS in areas likely attaining, and; 

(4) help minimize – where warranted – the need for states and EPA to engage in time 

consuming and costly SIP development and processing associated with overly broad 

“unclassifiable” designations. 

 

Such a selective approach under Section 107(d)(1)(B)(i) will allow states to more efficiently 

focus early planning efforts and limited resources where they are most needed, and avoid using 

staff resources on those areas likely attaining the standard. It will also help prevent shifting 

limited resources from other air quality planning efforts, such as ground-level ozone – a 

significant regional concern in the Northeast. We believe this approach would allow states to 

work in a smarter, more streamlined approach consistent with the Administration’s stated goal of 

reducing unnecessary regulatory burdens. It will also allow states to better allocate scarce 

resources, and focus early action on areas where it is most needed to protect public health. 

The remainder of NESCAUM’s comments focuses on the need for EPA to clarify key statements 

and requirements in the guidance. The sections and page numbers referenced below correspond 

with those in the Public Review Draft of the guidance, dated September 22, 2011, which was 

available on EPA’s website at: http://www.epa.gov/oaqps001/sulfurdioxide/implement.html. 

Section IV. Section 110(a)(1) and (2) NAAQS maintenance/infrastructure elements 

Comment: The two statements in the draft guidance listed below should be revised to 

explicitly indicate whether the 100 tons per year (tpy) threshold corresponds to actual or 

allowable emissions. 

 Page 9: “We expect that states would focus performance of attainment demonstration 

modeling on areas with larger sources (e.g., those source emitting over 100 tons per year 

(tpy) of SO2), and any other sources that we anticipate to cause or contribute to a 

violation to determine compliance with the new SO2 NAAQS.” 

 Page 10: “EPA believes it is reasonable to expect states to demonstrate, at a minimum, 

that major SO2 sources (≥ 100 tpy) are not causing or contributing to violations of the 1-

hour SO2 NAAQS.” 

Comment: Footnote 7 on Page 9 should be revised to the following (revised wording is in 

italics): “In cases where large sources of SO2 emissions are located on the borders of the 

other states, the states should coordinate the modeling methodology applied and the 
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NESCAUM - Docket I.D. # EPA-HQ-OAR-2010-1059 November 30, 2011

modeling inputs with each other during the development of the SIP submittals for the 

affected areas (i.e., before the modeling is submitted to EPA).” 

Section IV(B)(2)(a) Section 110(a)(1) SIPs: Maintenance demonstration: Refined dispersion 

 modeling 

Comment: Pages 16-17. This section suggests that states focus on those sources emitting 

more than 100 tpy of actual emissions. If a state were to base its approach on actual 

emissions, does EPA have a preferred method for calculating actual emissions? For 

example, the method could be based on an average of the last three years of available 

emissions data, the average of the last two years of available data, the latest year of available 

data (representing normal operating conditions), or the highest annual emissions reported in 

the last three years. 

Section IV(B)(3)(b) Section 110(a)(1) SIPs: Control strategy: SO2 limits for sources using 

 control measures to meet the Cross-state Air Pollution Rule and MACT rules 

Comment: Pages 21-23. This section states that many sources will be installing SO2 add-on 

controls due to the Cross-State Air Pollution Rule or the Utility MACT standards and that 

there is a need to establish enforceable 1-hour SO2 emission limits on these specific sources. 

This raises a broader issue applicable to all sources that could potentially require modeling 

for the purposes of determining compliance with SO2 NAAQS, i.e., if a source does not have 

a 1-hour SO2 emission limit, is it acceptable to use a longer term emission limit to represent 

the source’s 1-hour limit? 

For example, a large, existing source may have a 24-hour and an annual SO2 emission limit, 

but no 1-hour emission limit. Would it be acceptable to use the 24-hour emission limit in the 

1-hour SO2 NAAQS modeling, or would the facility’s permit need to be modified so that 

there is a 1-hour emission limit to use in the 1-hour SO2 NAAQS modeling? 

Appendix A, Section 5.1 Determining sources to model 

Comment: The draft guidance has no requirement if a source with allowable SO2 emissions 

above 100 tpy is not included in a state’s SIP modeling. EPA should require the state to 

provide some type of justification on why it was not modeled (e.g., very low actual 

emissions, high stacks, or future control anticipated). 

Comment: When modeling a facility with multiple SO2 emission points, such as an oil 

refinery or a glass plant, is there an hourly emission rate that the state can consider “de 

minimus” and, therefore, not include in the modeling? If such guidance is provided, we 

recommend it should be made a function of stack height. Example criteria would be to 

include the following in the modeling: 
Draft Guidance for 1-Hour SO2 NAAQS SIP Submissions Page 4 

NESCAUM - Docket I.D. # EPA-HQ-OAR-2010-1059 November 30, 2011

a) 2.5 lbs/hr or more with a stack height greater than 50 ft, 

b) 0.7 lbs/hr or more with a stack height between 20 and 50 ft, 

c) 0.3 lbs/hr or more with a stack height less than 20 ft. 

Appendix A, Section 6.3 Good Engineering Practice (GEP) stack height 

 

Comment: When building dimensions are input into the current version of AERMOD, the 

increased turbulence from building downwash effects is incorporated into the plume’s 

dispersion, even when a stack is at its GEP stack height. It is unclear in the draft guidance 

whether building dimensions need to be input into AERMOD for stacks with a height 

considered to be GEP. This needs clarification. 

Appendix A, Section 6.6 Urban/rural determination 

Comment: EPA should revise the beginning of the second paragraph in this section to read 

as follows (changes are in italics): “In addition, special emphasis must be placed in making 

accurate land use classification determinations for regulatory SO2 modeling. Topographic 

maps may not provide current representative land use classification. Therefore, physical 

surveying as well as the study of current aerial photos may be incorporated into this process. 

For SO2 modeling, the urban/rural determination is of great importance because AERMOD 

invokes a 4-hour half life for urban SO2 sources.” 

Thank you for the opportunity to comment. If you or your staff has any questions regarding the 

issues raised in this letter, please contact Laura Shields at NESCAUM at 617-259-2084. 

Sincerely, 

Arthur N. Marin 

Executive Director 

Cc: NESCAUM Directors 

Gina McCarthy, EPA/OAR 

Mary Henigin, EPA/OAQPS 

Anna Wood, EPA/OAQPS 

Scott Mathias, EPA/OAQPS 

Larry Wallace, EPA/OAQPS 

David Conroy, EPA Region 1 

William S. Baker, EPA Region 2