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17 February 2003 <br /> i <br /> ' AGE-NC Project No 95-0137 <br /> Page 5 of 7 <br /> ' 3 3 MASS OF RECOVERED HYDROCARBONS <br /> The hydrocarbon mass (TPH-g) removed during the operating period was calculated using the <br /> ' equation f <br /> M= C•Q•t <br /> where M= cumulative mass recovered (kg) <br /> { g} <br /> C = soil-vapor concentration (kg/m') <br /> rQ= extraction flow rate (m'/hr) <br /> t= operational period, in hours <br /> The estimated mass of hydrocarbons removed was based on laboratory analysis of soil-vapor <br /> samples, the flow rate and operational time The operational time for the quarter was divided into <br /> two time periods The mass of extracted hydrocarbons was calculated for each time period using <br /> average influent soil-vapor sample hydrocarbon concentrations and average air flow rates The <br /> operational results are summarized on Table 1 A total of 38 kg, 84 lbs or 13 3 gallons hydrocarbons <br /> as gasoline was removed between 19 September and 12 December 2002 The volume and mass <br /> calculations are attached in Appendix C <br /> 1 <br /> 3 4 GROUND WATER GRADIENT AND FLOW DIRECTION <br /> Depths to ground water on 02 January 2003 ranged from 22 27 to 23 35 feet below the well casing <br /> tops, the water depths had decreased an average of 0 73 feet from the September 2002 monitoring <br /> event The calculated ground water elevations ranged from 34 47 feet(MW-4)to 34 67 feet(MW-5), <br /> and ground water flow was inferred to be northwest at a hydraulic gradient of 0 001 foot/foot <br /> (Figure 3) <br /> 3 5 ANALYTICAL.RESULTS OF GROUND WATER SAMPLES <br /> ' TPH-g w as detected i n ground w ater samples MW-2, M W-3 and M W-4 at c oncentrations o f <br /> 220 microgram per liter(}tg/l), 160 µg/1 and 280 pg/l,,.espectively TPH-d was detected in all of the <br /> ' ground water samples at concentrations ranging from 130µg/1(MW-4)to 2,200µg/l(MW-3) TPH- <br /> mo was detected In all samples except MW-4 at com cnttations ranging from 270 4g/1 (MW-1) to <br /> 700 µg/1 (MW-3) <br /> ' Benzene and xylenes were the only two BTEX compounds detected Benzene was detected in sample <br /> • MW-2 at a concentration of 0 53 µg/l and xylene was detected in sample MW-3 at a concentration <br /> ' of 0 59 gg/1 <br /> Advanced GeoEnvi ron mental,Inc <br /> 1 <br />