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APPENDIX M . MTBE DISSOLVED VOLUME-MASS CALCULATIONS FLAG CITY CHEVRON 6421 Capitol Avenue, Lodi CA Assumptions The general shape of MTBE-impacted ground water at the site can be modeled as an elbow-shaped plume{Figures 14, 15, and 16) By splitting the plume into two segments (western and eastern), the volume can be calculated for each segment The western segment can be determined utilizing the equation for an elliptic cone Vcoae=l/s 7C a b h, where"a"is the is the semi-mayor axis of the cone,"b"is the semi-minor alas, and"h"is the height The eastern segment can be determined utilizing the equation for an elliptic,conic-shaped cylinder Vv.ui,w,.wtd=n h 1(al-ao)(bl-bo)/3+Jao(bl-bo)+bo(al-ao)ln+no bo), where al and ao are the semi-major axes of the cylinder,b, and bo are the semi-mmor axes,and"h" is the height In each segment,the average on-site MTBE concentration was calculated by summmg the detected concentrations and dividing by the total number of detections The average on-site MTBE concentration in the western(Vw)elliptic cone was calculated to be approximately 8 95 µg/1, or 8 95 • 10'9 µg/pg, the average on-site MTBE concentration in the eastern(VF)elliptic cone was calculated to be 260 pg/l,or 2 60+ 10 7 pg/pg _ r � { 1)Volume of MTBE-impacted ground water in Western Segment Elliptic Cone(V,,) For the estimated west half a=84 ft, b= 10 ft,h= 143 ft V.=(1 05)(84 ft)(10 ft)(143 ft)-+ 125,726 ft Water occupies the porosity in the soil,which is estimated to be 30%of the soil volume, so the total volume of water in the saturated portion of coned ellipse is approximated by Vw=(30)(125,726 ft)=37,718 ft One cubic foot of water contains 7 48 gallons, so the volume of the water in the coned ellipse is given by Advanced GeoEnvironmental,Inc