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f 1 � 1 APPENDIX J TOTAL PETROLEUM HYDROCARBON-IMPACTED GROUND WATER VOLUME ASSUMPTIONS AND CALCULATIONS Masonite (former PREM DOR) 433 West Scotts Avenue, Stockton, California Volume of TPH Impacted Ground Water Pre-Excavation: Assumptions: • The distribution of maximum dissolved hydrocarbon concentrations on the site can be approximated by an elliptical cylinder(Figure 12);the distribution can be separated into three contoured areas(i.e. 10,000 µg/1, 1,000 gg/1 and 50 µg/1). • The effective porosity of soil at the site is estimated to be 40% (i.e. silt and fine sand). • Data collected from the ground water sampling events are representative of the maximum dissolved site conditions prior to remediation activities. • The thickness of dissolved plume is estimated to be between the average depth to ground water at the site and the bottom of monitoring well.screen intervals (i.e. 15 feet). The area of an ellipse cylinder can be calculated by the formula: Ae= (long radius, a)(short radius,b) (Tu ) 1) For the estimated 10,000 gg/l ellipse cylinder;a= 12.5 ft, b = 8 ft, and thickness c= 15 ft i Utilizing TPH data from well MW-2 and the 10,000 gg/1 contour line(Figure 12),the average pre-excavation TPH concentration is estimated to be 62,333 ug/1(equivalent to 0.000062333 grams per milliliter).A ml is very nearly equivalent to a cubic centimeter of water, which by definition equals one gram, this concentration is nearly a unitless number. i The area of the ellipse is given by: Ai0000= n (12.5)(8)= 314.2 ftz The volume of the ellipse cylinder is given by: V,0000=Ai0000 x c= 314.2 ftp x 15 ft =4,712 ft3 Water occupies the porosity in the soil,which is estimated to be 40%of the soil volume,so the total volume of water in the saturated portion of the ellipse is approximated by: V,0000= (0.40)(4,712 ft3)= 1,885 ft3 One ft3 is equal to 7.48 gallons, so the volume of the water in the ellipse is given by: Vi0000=(1,885 ft3)(7.48 gal/ft3)= 14,100 gallons One gallon of water weighs 8.337 lbs/gal, so the mass of the water in the ellipse is given by: M, — (14 100 gallons)(8.337 lb/ al 117,552 lbs i0000— � g )( g )_