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 (SO 2 ), 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 SO 2 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 2monitoring 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) 222-2080H. 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 SO 2 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 50 2 , including the maximum ground level concentrations that exist around stationary SO 2 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 SO 2levels 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 SO 2NAAQS. 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.