ARCHIVED REPORTS XR0010898 - Laserfiche WebLink

Home Browse Search

06 February 2001 AGE-NC Project No. 95-0118 Page 5 of 7 i collected from the soil vapor stream at concentrations of 550.micrograms per liter(pg/1), 370µg11 and 160µg/l,respectively.BTEX was detected at concentrations as high as 53µg11 of xylene(11-27- 00). The analytical results are summarized in Table 5. The laboratory. report (MAI 54322, 56710 and . 58606),Quality Assurance and Quality Control (QA/QC) reports and chain-of-custody forms are J included in Appendix D. 3.2. MASS OF RECOVERED HYDROCARBONS The mass of extracted hydrocarbons was calculated for a limited time period using the average hydrocarbon concentrations of influent vapor samples collected and average flow rates. A total of approximately 15 gallons of gasoline was calculated to have been removed between 27 November 2000 and 23 January 2001. The mass calculations are attached in Appendix D. The hydrocarbon mass removed during the operating period was calculated using the following equation M= C•Q•t. where: M=cumulative mass recovered(kg) `s C=vapor concentration(kg/m3) Q= extraction flow rate (m3/hr) t=operational period, in hours i 3.3. RELATIVE GROUND WATER ELEVATION AND GRADIENT The relative ground water elevation in each well was calculated by subtracting the ground water depth from the surveyed casing elevations. The depth to ground water and the relative ground water elevations are surninanzed in Table 1. The depth to ground water, as measured from the casing tops,ranged from 33.14 feet to 34.83 feet. The relative groundwater elevations ranged.from 65.05 to 66.00 feet. The average relative ground water elevation increased 1.5 feet since the last ground water monitoring event. The prevailing ground water flow direction is to the north at a maximum gradient of 0.017. Relative ground water elevation contours are depicted in Figure 3. Advanced GeoEnvironmental,Inc. f f i ,J f