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Mr. R K Hancock, III <br />Mr. Chazles M. Machovec <br />• Apri14, 2005 <br />Page 5 of 10 <br />direction, any receptor within that 100-m grid, or any receptor on the HGTI property <br />boundary, was removed from the analysis if it fell within a 20-meter buffer area <br />measured from the edge of the road. Thus, any receptor within 29 meters from road <br />centerline, given an 18-meter wide haul road, was removed. These excluded receptors <br />were run in a sepazate analysis with all sources except the TAHR to ensure that no <br />violations occurred at these locations from the remaining sources. The receptor grid is <br />presented in Figure 1. <br />Background Data <br />Ms. Nancy Chick of the APCD provided MMA a 24-hour average background <br />concentration of 23 µg/m3 and an annual average of 11 µg/m3. These data were from the <br />Colowyo monitoring program, and reflect lower values than what was used in the <br />December 2004 application (35 and I1 µg/m3.) <br />Results <br />Model results for this modified analysis aze presented in Table 1, and all modeling input <br />and output files are located on CD in Attachment B. For the TAHR run, ISCST3 <br />predicted a 24-hour highest second-high concentration for the maximum 24-hour <br />• production scenazio of 123.6 µg/m3, with the TAHR being the only contributor to the <br />impact. Adding background of 23 µg/m3 gives a total prediction of 146.6 µg/m3, below <br />the standard of 150 µg/m3. The maximum annual concentration for the TAHR model run <br />was predicted to be 29.2 µg/m3. Adding the background of 10 µg/m3 gives a total <br />concentration of 39.2 µg/m3, again below the standard of 50 µg/m3. Figures 2 and 3 <br />provide ispoleth maps of the 24-hour and annual impacts, respectively. <br />The modeling for the excluded receptors and all sources except the T.AIIR predicted no <br />violations of the standards. For the maximum 24-hour production scenario, the highest <br />second-high was 61.4 µg/m3 and after adding background (23 µg(m3), the total impact is <br />64.9 µg/m3. For annual, the predicted annual maximum was 13.4 µg/m3 and 23.4 µg/m3 <br />with background. <br />Conclusions <br />The additional analyses presented herein should now resolve any remaining APCD <br />issues. The modeling demonstrates that HGTI will be in full compliance with applicable <br />standards. A permit to construct should thus be granted as expeditiously as possible <br />given HGTI's projected commencement of activities in mid-April. Due to the emission <br />changes and the tons per day maximum, a new APEN and filing fee is presented in <br />Attachment C, and emission calculation sheets aze in Appendix D. <br />• <br />44luvemess Drive Earl ~ Building C ~ Englewood, Colorado 80112 <br />303/790-1332 ~ Fax 303/790-7820 <br />www.mcvehil-monnett.cam <br />