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^ <br />� <br />f <br />� Members of [he Roseville City Council <br />Novem6er 18, 2010 <br />Page 2 <br />.� <br />During my reviea� of the EAW and the rela[ed MPCA file, I reviewed the odoi modeling <br />compieted with respect to [he proposed Asphalt Plant. The modeling shov✓s that when using [he air <br />quality control measures in the propozed air permit, odors from the plant (hydrogen sul(ide (H,SJJ will <br />be readily detectible beyond the property limits of the proposed site The extent of the area in which <br />[he odors will be perceptible may depe�d on each individual. We do not know lhat the mitigation <br />technology will be effective to the extent assumed by the model, and therefore may be perceptible in a <br />larger area than shown by the EA1N. <br />1 have speci(ically reviewed the odor discussion in the EAW. The EAW shows maximum <br />concentrations of hydrogen sulfide (HtS) o( 21.54. It also shows mazimum concentrations of hydrogen <br />sulfide (HzS� of 21.54 (Ng/m�) at the property line, 3.63 (µg/m') al the Gross National Golf Club, and 2.95 <br />(Ng/m3) at the nearest residence. The Agency (or Toxic Substances and Disease ftegistry �ATSDRj, a <br />federal public health agency of the U.S. Department of Health and Human Services, siates that HZS has <br />"...a characteristic rotten-egg odor that i; detectable at concentrations as Iow as 0.5 parts per billion <br />(ppb). At 25° C, 1 ppb H15 = 1.4 µg(m3 and 0.5 ppb under Ihe same conditions equal OJ Ng/m'. This <br />concentration is accepted as the concentration Ievei at which 5095 of the population wili detect the <br />rotten egg odor associated with HzS. The EAW provides a diagram of Acute Risk Impacts (Figure 13). <br />The diagram shows Maximum Acute Risk values ranging (rom 0.46 ?o OA2 plotted on a map of the area. <br />Assuming that the risks at different focations are mathematical ratios of the concentrations in the <br />modeied exhaust stream, corverting the b1ax Acute Risk values to H,S concentrations (��g/m3) shows <br />Ihat at least 50°r6 of the populetion will detect a rotten egg odor from HzS in an area From roughly <br />County Road C West on the north; Long take Road on [he east; County Road B West on the south; and <br />the second and tenth fairways of the Gross National Golf Club to the �vest. The table below conver[s <br />Max Awte Risk ralue5 to approximate H25 concentralions: <br />