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31 August 2005 <br /> AGE-NC Project No 96-0232 <br /> Page 20 of 30 <br /> segment) The volume of the western impacted ground water segment can be determined by utilizing <br /> the formula for an elliptic cone(V=1/3Tcabh),where`a' represents the semi-major axis,`b'represents <br /> the semi-minor axis and `h' represents the height of the elliptic cone For the western segment, a <br /> semi-minor axis of 10 feet, a semi-major axis of 84 feet, a height of 143 feet and an average MTBE <br /> concentration of 8 95 µg/1 were used to estimate the coned elliptical volume of MTBE-impacted <br /> ground water The volume of the eastern impacted ground water segment can be determined by <br /> utilizing the formula for an elliptic, cone shaped cylinder (V=nh((al-ao)(b,-bo)/3+ao(bi-bo)+bo(al- <br /> a0)1/2+a0b0)),where `a' represents the semi-major axis, `b' represents the semi-minor axis and `h' <br /> represents the height of the elliptic, cone shaped cylinder, an average MTBE concentration of 260 <br /> µg/l were used to estimate the elliptic, cone shaped cylinder volume of MTBE-impacted ground <br /> water When the data collected at the site is plotted in both plan view and cross sectional views,the <br /> apparent volume of MTBE impacted ground water remaining at the site totals approximately <br /> 1,082,009 gallons, which yielded a total of approximately 1 75 pounds of MTBE, or an estimated <br /> 0 28 gallons of MTBE remaining in ground water at the site Volume calculations are included in <br /> Appendix M <br /> 5.0. CORRECTIVE ACTION <br /> Between November 2000 and August 2004, ground water P&T remediation was performed at the <br /> site by selectively extracting MTBE-impacted ground water from onsite,First Zone wells EW-2 and <br /> EW-4 through EW-10, each extraction well was independently adjusted to continuously extract <br /> ground water at a flow rate of approximately 4 to 5 GPM All extracted MTBE-impacted ground <br /> water was routed through a ground water treatment system consisting of four 2,000 pound media <br /> vessels containing coconut shell, liquid phase granular activated carbon (GAC) <br /> During the above referenced P&T operational period, a grand total of approximately 27,086,201 <br /> gallons of MTBE-impacted water was treated and discharged to a conveyance ditch (located <br /> approximately 450 feet towards the south)under RWQCB General Order 5-00-119 for discharge to <br /> surface waters of ground water from cleanup of petroleum fuel pollution and under National <br /> Pollutant Discharge Elimination System (NPDES) waste water discharge permit no CAG915001 <br /> From the 27,086,201 gallons of treated ground water, a grand total of 13 33 pounds of MTBE was <br /> estimated to have been removed <br /> Laboratory analysis of ground water extraction well samples (EW-1 through EW-10) historically <br /> detected MTBE from all ten wells,the greatest MTBE concentrations were historically detected from <br /> wells EW-1 and EW-2 (southwest corner of UST tank pit area) at concentrations as high as 3,300 <br /> gg/l(July 2000) Declining MTBE concentrations were evident from all ten ground water extraction <br /> wells during operation of the P&T remediation system, at various stages during P&T operations, <br /> MTBE concentrations approached non detectable levels from all ten of the extraction wells <br /> Advanced GeoEnvironmental,Inc <br />