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1 08 June 2001 <br /> AGE-NC Project No 95-0137 <br />' Page 7 of 9 <br /> ' 3 4 MASS OF RECOVERED HYDROCARBONS <br /> The hydrocarbon mass (TPH-g) removed during the operating period was calculated using the <br /> ' following equation M = C•Q•t <br /> where M= cumulative mass recovered (kg) <br /> C _ soil-vapor concentration(kg/m') <br /> Q = extraction flow rate (m'/hr) <br /> t=operational period, in hours <br /> ' The operational time was divided into four time periods The estimated mass of hydrocarbons <br /> removed was based on laboratory analysis of soil-vapor samples The mass of extracted <br /> ' hydrocarbons was calculated for each time period using average hydrocarbon concentrations of <br /> influent soil-vapor sample data and average air flow rates The operational results are summarized <br /> 1 on Table 4 <br /> Approximately 1,300 kg or 460 gallons of hydrocarbons were extracted and destroyed by the SVE <br /> lienetwork between 05 December 2000 and 09 April 2001 The volume and mass calculations are <br /> attached in Appendix E <br /> ' 3 5 GROUND WATER GRADIENT AND FLOW DIRECTION <br /> ' The elevation of ground water in each well was calculated by subtracting the depth to ground water <br /> from the surveyed well casing elevations (Table 5) <br /> ' Depths to ground water ranged from 18 51 to 20 23 feet below the well casing tops The relative <br /> ground water elevations at the site ranged from 79 92 feet to 80 06 feet There was an average <br /> decrease of the relative ground water elevation at the site of 0 2 feet over the last quarter <br /> ' The ground water flow ranges from northwest to northeast(Figure 3) The hydraulic gradient, away <br /> from the former UST area, was calculated to be 0 0017, directed toward the west The hydraulic <br /> ' gradient was stepper west of the former UST and remediation area <br /> ' 3 6 ANALYTICAL RESULTS OF GROUND WATER SAMPLES <br /> TPH-g was detected in five of the eight ground water samples, at concentrations ranging from <br /> ' 130 kzg/l in sample MW-8 to 1,900 4gll in samples MW-2 TPH-d was detected in seven of the eight <br /> ground water samples collected at concentrations ranging from 200 µg/1 in samples MW-1 to <br /> ' 2,000µgll in MW-6 (off-site Jimco) <br /> Advanced Geo Environmental,Inc <br />