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r� <br /> f 06 December 2000 <br /> =� AGE-NC Project No. 95-0100 <br /> j Page 4 of 6 <br /> ,i <br /> 3.0. FINDINGS <br /> Field data was utilized to select soil and ground water samples for laboratory analysis. Petroleum <br /> hydrocarbon impact to soil was assessed and quantified by laboratory analysis. Laboratory analysis <br /> of eight soil samples detected TPH-g or BTEX compounds in four soil samples. Soil vapor samples <br /> were collected from the positive pressure.blower during one event during the quarter and one in the <br /> f = last quarter of the year, the data collected was used to estimate the mass of hydrocarbons removed <br /> from the soil at the site. Ground water elevation,flow direction and gradient were determined from <br /> field data collected on 07 August 2000; the contaminant impact to ground water was assessed from <br /> f z the laboratory data. <br /> =: 3.1. SOIL VAPOR EXTRACTION <br /> During the later portion of the reporting period, the active blower operated at an extraction flow rate <br /> of 60 scfm. An induced vacuum (negative pressure) of approximately 24 inches of water was <br /> monitored in the piping between the blower and the extraction wells. Vacuum pressures as high as <br /> 0.4 inches of water were measured at vapor well VW-1. <br /> Y TPH-g was detected in the 14 September and 20 October 2000 samples collected from the soil vapor <br /> ., stream at concentrations of 890 micrograms per liter (µg/1) and 730 ,ug/l, respectively. BTEX was <br /> detected at concentrations as high as 80 µg/l of xylene. <br /> The analytical results are summarized in Appendix C. The laboratory report (MAI 47594 and <br /> 51019), Quality Assurance and Quality Control (QA/QC) reports and chain-of-custody forms are <br /> included in Appendix C. <br /> 3.2. MASS OF RECOVERED HYDROCARBONS <br /> The mass:of extracted hydrocarbons was calculated for a limited time period using the average <br /> hydrocarbon concentrations of influent vapor samples collected and average flow rates. A total of <br /> ` approximately 25 gallons of gasoline were calculated to have been removed between 14 September <br /> and 20 October 2000. The mass calculations are attached in Appendix D. The hydrocarbon mass <br /> removed during the operating period was calculated using the following equation M= C•Q•t. <br /> where: M- cumulative mass recovered (lig) <br /> C.= vapor concentration (kg/m3) <br /> Q = extraction flow rate (m3/hr) <br /> t— operational period, in hours <br /> Advanced GcoEnvironmcntal,inc. <br />