Lincoln D. Chafee

Governor OFFICE OFTHE REGIONAL ADMINISTRATOR 

State Of Rhode Island and Providence Plantations 

RECEIVED 

MAY 232011 

H. Curtis Spalding, Regional Administrator 

EPA Region I 

5 Post Office Square, Suite 100 

Boston, MA 02109-3912 

Dear Mr. Spalding: 

Pursuant to the requirements of Section 107(d)(1) of the Clean Air Act Amendments of 1990, 

Rhode Island is hereby submitting its recommendation for the State's attainment status 

designation for the revised National Ambient Air Quality Standard (NAAQS) for sulfur dioxide 

(SO2), which was promulgated on June 2, 2010.1 

A monitoring site is in compliance with the revised NAAQS if the design value for that site is 

less than or equal to 75 ppb. The design value is calculated by averaging the 99th percentile 

maximum daily one-hour SO2 concentrations measured at the site each year in three consecutive 

years. The design values for the past ten years for Rhode Island's current SO 2 monitoring site, 

which is located at Brown University in Providence, are as follows: 

Year Design Value (ppb) 

2001 56 

2002 47 

2003 44 

2004 42 

2005 45 

2006 42 

2007 38 

2008 30 

2009 28 

2010 25

'75 FR 35520, June 22, 2010, http://www.epa.gov/ttnlnaags/standards/s02/fr/20100622.pdf

State House, Room 227, Providence, Rhode Island 02903-1196 • (401) 222-2080 
H. Curtis Spalding, Regional Administrator 

May 18, 2011 

Page Two 

Since these design values are considerably lower than the 75 ppb NAAQS and have steadily 

decreased with time, the Providence site is clearly in monitored attainment of the revised 

standard. Note that SO2 levels that were measured at a site operated on Dorrance Street in 

downtown Providence until 2007 were consistently lower than those at the Brown University 

site. 

However, monitoring data alone "may not be adequate to fully characterize ambient 

concentrations of 502 , including the maximum ground level concentrations that exist around 

stationary SO2 sources"2 For that reason, the revised NAAQS requires states to submit air 

quality dispersion modeling analyses to be used in conjunction with monitoring data to determine 

whether an area is in attainment of the standard. Rhode Island has not yet conducted the required 

modeling analysis; in fact, EPA has not yet released comprehensive guidance specifying 

appropriate methodology for such analyses. 

Since monitored SO2 levels in Rhode Island do not exceed the revised NAAQS and modeling 

data are not yet available, I am recommending that Rhode Island be designated at this time as 

'unclassifiable" for the 2010 SO2 NAAQS. As required in the revised NAAQS, Rhode Island 

will submit a revision of its State Implementation Plan (SIP) by June 2013 that will, using 

refined dispersion modeling, identify emissions sources that have the potential to cause or 

contribute to modeled violations of the revised NAAQS and demonstrate that SO 2 emissions 

from those sources will be sufficiently controlled to ensure attainment of the NAAQS in the State 

as expeditiously as possible, but no later than August 2017. The SIP revision will specify 

mechanisms that will be utilized to implement and enforce emission reduction requirements. 

If you have any questions about this issue, please feel free to contact Barbara Morin at the Rhode 

Island Department of Environmental Management's Office of Air Resources at (401) 222-4700, 

extension 7012.

Lincoln D. Chafee 

Governor 

2 USEPA Memorandum from Stephen D. Page, director, Office of Air Quality Planning and Standards, "Area 

Designations for the 2010 Revised Primary Sulfur Dioxide National Ambient Air Quality Standards, March 24, 

2011.