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y t <br /> COMPUTATION SHEET <br /> PROJECT TITLE ARCO Service Station 2076 PROJECT NO 20805-144 004 <br /> DESCRIPTION Mass of Petroleum Hydrocarbons in Soil SHEET 1 OF 5 <br /> PREP BY DATE CHKD BY DATE <br /> These calculations present the total mass of petroleum hydrocarbons (TPHG) in sod The data set contains <br /> analytical results for UST cavity and piping trench sod samples and exploratory boring sod samples collected through <br /> 1993 Isoconcentration plots of the analytical data were prepared for depths of 2 to 6 feet, 6 to 14 feet,14 to 20 feet, <br /> and 20 to 35 feet bgs The area enclosed by the respective isoconcentration lines was determined using a planimeter <br /> Sod types encountered during drilling include fine grained sand (SP), fine to medium grained and fine to coarse <br /> grained sand (SW), silty sand (SM), silt to clayey silt(ML), and clay (CL) Average bulk density values for the soil <br /> types encountered of 100 pcf for sand (SP,SW,SM) and 120 pcf for silt (ML) were used in the calculations The <br /> depths at which clay is encountered exceed the vertical extent of petroleum hydrocarbon impact <br /> Assumptions concentrations within isoconcentration line are assumed constant <br /> the concentration does not vary with depth <br /> Soil type from 2 to 6 feet and 6 to 14 feet assumed to be sands with bulk density of 100 pcf <br /> Sod type in vicinity of former UST cavity assumed to be sands with bulk density of 100 pcf <br /> Sod type at 20 to 35 feet consists of interbedded sand and silt, an average bulk density <br /> of 110 pcf was used across this interval <br /> Planimeter Data <br /> Depth Interval Contour Line Area (ft2) Volume (ft3) Corr Vol (ft3) <br /> 2 to 6 ft 10,000 ppm 336 134 <br /> 1,000 ppm 499 1996 1862 <br /> 100 ppm 1163 4652 2656 <br /> 10 ppm 2968 11872 7220 <br /> 1 ppm 3712 14848 2976 <br /> 14-te-20 ft 10,000 ppm 0 0 <br /> 1,000 ppm 0 0 0 <br /> 100 ppm 63 378 378 <br /> 10 ppm 1033 6198 5820 <br /> 1ppm 1837 11022 4824 <br /> 14 to 20 ft 10,000 ppm 317 190 <br /> 1,000 ppm 175 1050 860 <br /> 100 ppm 609 3654 2604 <br /> 10 ppm 895 5370 1716 <br /> 1 ppm 1189 7134 1764 <br /> Equation Mass of TPHG =volume of sod X soil density X pounds TPHG/pound of soil <br /> corrected volume subtracts the area enclosed within the 10,000 ppm contour from the <br /> are enclosed within the 1,000 ppm contour, etc , to prevent estimating the mass twice <br /> H,/exceldaVarco/2076calc As <br />