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MEMORANDUM To: Project File 8032 From: Kimiye Touchi Subject: Tracy VOC Remediation System - Hydrochloric Acid Emission Predictions Date: December 24, 1997 The Tracy Yard VOC Remediation System involves the extraction of VOCs from the subsurface and their destruction via thermal oxidation in a catalytic oxidizer. Byproducts of thermal oxidation of HVOCs include carbon dioxide, water and hydrochloric acid. Emissions of hydrochloric acid are regulated by the State of California and must not exceed 7.0 ug/m3 at sensitive receptors. Hydrochloric acid concentrations experienced by nearby receptors may be evaluated using dispersion modeling techniques. One simple model used by San Joaquin Valley Unified Air Pollution Control District is SCREEN3. (Disclaimer: SCREEN3 is a simple model and is used primarily as a screening tool. If concentrations generated by the model are borderline, the County recommends the use of a more sophisticated model to make the final determination.) Attachment A. Attachment A provides the results of a number of modeling runs. Concentrations have been generated by SCREEN3 a various distances from the catalytic oxidizer, using 1.29 lb/d VOC emission rate as the basis for the calculations. Runs were performed at outlet temperatures of 300°F and 600°F, without building downwash, based on the following assumptions: All modeling runs used the following assumptions: Source Type: Point Stack Height (m): 7.6 Stack inside diameter (m): 0.10 Stack Exit Velocity (m/s): Calculated Stack Gas Exit Temp (K): 588 (600°F) or 422 (300°F) Ambient Air Temperature (K): 293 Receptor Height (M): 2.0 Urban/Rural Option: Rural Meteorology: All windspeeds and directions Terrain Ht. above stack base (M): 0 Attachment B. Attachment B presents calculated concentrations at various distances from the catalytic oxidizer, ranging from 1 to 5,000 meters from the stack, based on total HVOC emissions of 1.29, 1.0, and 0.5 pounds of HVOCs per day. In general, modeling runs conducted at stack temperatures of 600°F and 300°F, respectively, indicate that hydrochloric acid emissions, in the absence of building