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Wenck Associates, Inc. 1800 Pioneer Creek Ctr. P.O. Box 249 Maple Plain, MN 55359 -0249 Wenck (783)479.4200 Fax (763)479 -4242 E -mail: wenckmwenak.com TECHNICAL MEMORANDUM TO: Kent Peterson, Bituminous Roadways FROM: Jared Anderson Ed Hoefs, Wenck Associates, Inc. CC: Greg Korstad, Larkin Hoffman RE: Additional Odor/Hydrogen Sulfide Ambient Air Quality Analysis DATE: October 20, 2010 This memorandum summarizes the results from additional hydrogen sulfide air d p@ si on modeling for Bituminous Roadways' proposed asphalt plant/asphalt cement storage facility, to be located in Roseville, Minnesota. Hot mix asphalt production and asphalt cement storage and handling can result in odors. Odors can be traced primarily to hydrogen sulfide in asphalt cement. Hydrogen sulfide can be present due to sulfur in crude oil. To address the potential for hydrogen sulfide impacts from the proposed operation, an odor impact analysis for the proposed project was conducted. Prior modeling analyses have included emission sources from the hot mix asphalt plant, the asphalt cement storage facility and the asphalt tanker railcar heating. On October 15, 2010 you requested that Wenck Associates, Inc. (Wenck) summarize the predicted 1 -hour hydrogen sulfide (H2S) concentrations from the proposed hot mix asphalt (HMA) plant alone in comparison with the H2S concentrations from the proposed asphalt cement storage facility as well as the asphalt tanker railcar heating. Similar to all other modeling analyses completed for the proposed HMA plant and asphalt cement storage facility, Wenck used AERMOD to complete the modeling analysis. The maximum predicted H2S concentrations at the property boundaries from these proposed groups of emission sources are listed in Table 1. Also listed in Table 1 are the odor thresholds relied upon in the Environmental Assessment Worksheet that the predicted impacts are compared against. The results in Table 1 assume that activated carbon would be used to control the H2S emissions while the railcars are being heated. Table 1. 1 Hour Hydrogen Sulfide Predicted Concentrations U ated Modeling EAW Modeling Impact HMA Tank Railcar All Sources with All Sources with Plant Farm Heating Railcars Controlled' Railcars Uncontrolled' (Pg/m (P01 (Pg/m g/m (Pg/m Modeled Concentration 4.4 6.9 1.9 7.2 18,8 Odor Nuisance Threshold 56 Minnesota State Standard 42 Odor Detection Threshold 11 'The concentrations listed for the H MA Plant, Tank Farm. and Railcar Heating operations are not additive because their individual maximum impacts occur under different t -hour events and locations in the model compared to the maximum event for all units operating simultaneously. N Vl'ahnicatO23•Bunminous RN I I 2009 Roseville C WItodenndunemnW2s•memo doe