                                       
UNITED STATES ENVIRONMENTAL PROTECTION AGENCY                 Office of Air Quality and Planning Standards
                           109 T.W. Alexander Drive
                               Durham, NC 27709
                                       

                                   OFFICE OF
                               AIR AND RADIATION
                                                                                               	     
                                       

MEMORANDUM

                              
SUBJECT:	Data files used in the analysis of "Potential for Excess Local Deposition of Mercury in Areas near U.S. EGUs" for MATS docket EPA-HQ-OAR-2009-0234

FROM:	Halil Cakir
		Air Quality Analysis Division
		Office of Air Quality and Planning Standards

TO:		Docket EPA-HQ-OAR-2009-0234

DATE:		December 12, 2011



The purpose of this memorandum is to transmit data files which were used in the GIS analysis of excess local mercury deposition supporting the appropriate and necessary finding for the Mercury and Air Toxics Standard.  This analysis is described in the "Technical Support Document: Potential for Excess Local Deposition of Mercury in Areas near U.S. EGUs", which is available in the docket.  

The disc accompanying this memo contains the following information:

   a) ArcGIS 10 ArcMap document (Hot Spot Analysis.mxd) that saves map layouts, features, symbology, spatial extent of the maps, and relative path names.  
   b)  the CMAQ-modeled Hg excess deposition files for the 2005 and 2016 scenarios 
   c) the spatial averages of the U.S. EGU-attributable deposition (obtained by subtracting estimated mercury deposition with U.S. EGU Hg emissions zeroed out from baseline mercury deposition from all sources including U.S. EGU Hg emissions) across the grid cells with centers falling inside the 50 km and 500 km buffers. 


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