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Human Health Risk Assessment <br /> Former Mobil Oil Bulk Plant 04-343 <br /> 500 East Grant Line Road <br /> Tracy, California <br /> could introduce air containing BTEX into a building. The introduction cf toxicants in air from <br /> outside the building is quantified from the Wowing equation: <br /> COW = Q *DL <br /> ws * mh <br />' Where: Q = Chemical flux (from previous equation)(g/cm'-sec) <br /> DL = Downwind length of contamination (cm) <br /> 1 ws = Wind speed (cm/sec) <br /> mh = Mixing height of air mass (cm) <br />' C,,(s) = Concentration of chemical from outdoor air (g/cm3) <br /> 5.3.2.4 Calculation of Chemical Concentrations in Indoor Air <br /> For the future exposure scenario, the site is considered paved and .leveloped with a retail <br /> facility. The model presented estimates the indoor air concentration : a chemical. Included <br />' in this model is an attenuation factor of 10-3 (0.001), which ac(.!-.unts for the decreased <br /> permeability of a concrete foundation. The equations which predict thr, chemical concentration <br /> in indoor air resulting from flux through the concrete foundation are: <br />' CXS) = F * b * A <br /> VR <br /> Where: F = Flux of chemical (from previous equation) <br /> b = Attenuation factor for building foundation (dimensionless) <br />' A = Surface area of building floor (cm2) <br /> VR = Building ventilation rate (cm3/sec) <br /> C;(s) = Concentration of toxicant from indoor air comfronent (g/cm) <br /> VR = A * H * E * CF <br /> A = Surface area of building floor (cm2) <br /> H = Ceiling height of building (cm) <br />' E = Air exchange rate (volume changes/hour) <br /> CF = Correction factor (hours/second) <br /> VR = Building ventilation rate (cm3/spr) <br /> 30-0136-11 <br /> 5-9 <br />:1 <br />