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r. APPENDIX J DISSOLVED TPH VOLUME ASSUMPTIONS AND CALCULATIONS PAGE 4OF5 Volume Of TPH-g Impacted Ground Water Post Excavation: Assumptions: • The distribution of dissolved hydrocarbon concentrations on the site can be approximated by an elliptical cylinder (Figure 13); and • The effective porosity of soil at the site is estimated to be 40%. • The average of data collected from post-remediation ground water sampling events are representative of existing site conditions. • 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 can be calculated by the formula: Apost eXe= (long radius, a)(short radius,'b) ( Tc ) For the estimated ellipse cylinder volume: a=9.5 ft,b =20 ft, and thickness c= 15 ft The average post excavation TPH concentration for the ellipse is estimated to be 410 ug/l. This concentration is equivalent to 0.000000410 grams per ml. 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. The area of the ellipse is given by: Apost eXe = Tc (9.5)(20)= 597 fe The volume of the ellipse is given by: Vpost eXe=Apost eXc x c= 597 ft2 x 15 ft =8,955 ft3 Water occupies the porosity in the soil,which is estimated at this site to be 40% of the soil volume, so the total volume of water in the saturated portion of the ellipse cylinder is approximated by: • Vpost eXe= (0.40)(8,955 ft) 3,582 ft3 One cubic foot of water contains 7.48 gallons,which weighs 8.337 lbs/gal,so the volume of the water in the ellipse cylinder is given by: Vpost eXe = (3,582 ft3)(7.48 gal/ft') = 26,793 gallons One gallon of water weighs 8.337 lbs/gal, so the mass of the water in the ellipse cylinder is given by: Mpost eXe= (26,793 gallons)(8.337 lb/gal) =223,373 lbs f