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FMS #24 Site Investigation Report <br />California Army National Guard <br />day/yr <br />Table 3-7. Risk and Hazard Estimates — Inhalation of Volatile Organic Compounds <br />DTSC <br />= Department of Toxic Substances Control_ <br />FMS <br />= Field Maintenance Shop <br />glmole <br />— grams per mole <br />Current Conditions — Existing <br />Commercial/industrial Land Use <br />ppbv <br />= parts per billion by volume <br />yrs <br />= years <br />m/m3 <br />micrograms per cubic meter <br />Stockton FMS #24 Site, <br />Stockton, California <br />Description <br />Variable <br />Value <br />Equations <br />Attenuation Factor, Current Commercial <br />a <br />0.001 dimensionless <br />Cancer Risk: <br />Averaging Time, carcinogens <br />ATS <br />70 yrs <br />d <br />IRA,, <br />IRAQ x EF x EDQ x ET <br />= x 701cg x <br />URF x Risk URF <br />C� <br />aJr x[. <br />Averaging Time, noneareinogens, adult <br />AT.,, <br />25 yrs <br />20 m3 <br />x AT,, x 365 days I year <br />Body weight, adult <br />BW,, <br />70 kg <br />Chemical Concentration in indoor air <br />Cair <br />chemical -specific gg/m3 <br />Noncarcinogenic Hazard: <br />Soil -Gas Concentration <br />Csoi€-gas <br />chemical -specific µg/m3 <br />Exposure Duration, adult <br />ED,, <br />25 yrs <br />IIRAQ <br />x EF x ED,, x ET <br />Exposure Frequency <br />EF <br />250 days/yr <br />Hazard = <br />x Carr x <br />Fraction of EF breathing air at the site <br />ET <br />1 unitless <br />RX X 20 m3 x 1 <br />BWQ x AT„, Q <br />x 365 days/ year <br />Inhalation Rate, adult <br />IRAs <br />14 m3/8 -hr day <br />1 d 70 kg <br />Inhalation Reference Concentration <br />RfC <br />chemical -specific µg/m3 <br />where: <br />Inhalation Unit -Risk Factor <br />URF; <br />chemical -specific (µghn)-i <br />Carr = a x Csarr-gas <br />Soil Gas <br />Molecular <br />Cancer <br />Hazard <br />Concentrations <br />Weight <br />Csoli-gas a (XC <br />Cair URF; d Risk <br />% of <br />RfC d <br />Quotient <br />% of <br />Compound (ppbv)(g/mole) <br />(pg/M3) dimensionless <br />(pglm3)(pg/m3)-' (dimensionless) <br />Tota! <br />pglm3 <br />(dimensionless) <br />Total <br />Volatile Organic Compounds <br />Benzene 6.5 <br />78.11 <br />2.11E+01 0.001 <br />2.11E-02 2.90E-05 1.05E-07 <br />21% <br />6.00E+01 <br />1.69E-04 <br />4% <br />Naphthalene 13 <br />128.16 <br />6.93E+01 0.001 <br />6.93E-02 3.40E-05 4.03E-07 <br />79% <br />9.00E+00 <br />3.69E-03 <br />93% <br />Toluene 7.1 <br />92.13 <br />2.72E+01 0.001 <br />1.28E-02 No Toxicity Value — <br />— <br />3.00E+02 <br />4.35E-05 <br />1% <br />m- &p -Xylenes 19 <br />106.17 <br />8.39E+01 0.001 <br />8.39E-02 No Toxicity Value <br />— <br />7.00E+02 <br />5.75E-05 <br />1% <br />Cancer Risk <br />Hazard Index <br />Cumulative: 5E-07 <br />0.0040 <br />a Maximum detected concentration from any of the four samples collected from 8 feet below ground surface. <br />b Unit conversion for soil -gas concentrations: <br />Concentration (µg/m3) = [Concentration (ppbv) -1,0001 x MWx41.5957 <br />where: <br />MW = molecular weight of the compound (g/mole); 41.5957 = <br />constant ([mole•µg-L]/[m3•g•µL]), based on the Universal Gas Constant (R), unit conversion factors, standard temperature (20°C), and standard <br />pressure (1 atm). <br />` Default attenuation factor (Table 2; DTSC, 2005) for existing slab -on -grade <br />commercial land use <br />d Toxicity values from the California Environmental Protection Agency, Office of Environmental Health Hazard Assessment (http://www.oehha.ca.gov/risk/Chemica]DBlindex.asp ). <br />day/yr <br />= days per year <br />DTSC <br />= Department of Toxic Substances Control_ <br />FMS <br />= Field Maintenance Shop <br />glmole <br />— grams per mole <br />kg <br />kilogram <br />ppbv <br />= parts per billion by volume <br />yrs <br />= years <br />m/m3 <br />micrograms per cubic meter <br />B-18 December 2007 <br />