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24 June 2005 <br /> AGE-NC Project No. 97-0290 <br /> Page 5 of 7 <br /> The analytical results are summarized in Table 6. The laboratory reports (CTEL Project Nos.: <br /> CT214-0410178,-0411001,-0411177,-0412191,-0501131,-0502117-0503292),QA/QC reports <br /> and chain of custody forms are included in Appendix D. <br /> 3.4. SOIL-VAPOR EXTRACTION ANALYSIS <br /> After a one-month hiatus,the S VE system was restarted on 27 October for rebound response testing; <br /> the SVE extraction system operated continually through 29 March 2005. The hydrocarbon mass _ <br /> (TPH-g)removed during the operating period was calculated using the following equation: <br /> M=C•Q•t <br /> where: <br /> 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 calculated mass of hydrocarbons removed was based on laboratory analysis of soil-vapor <br /> samples and an average of the soil vapor flow rates. The mass of extracted hydrocarbons was <br /> calculated using average hydrocarbon concentrations of soil-vapor samples collected between late <br /> October 2004 and March 2005;a calculated total of 127 lbs of gasoline(TPH-g)was removed during <br /> this period. A conservative estimate of 50 µg/1 (highest value) was used to determine the TPH-g <br /> mass extracted during sampling intervals in which TPH-g was not detected'(<50 gg/1)in soil vapor <br /> samples.Operational parameters are presented in Table 5.The volume/mass calculations and sample <br /> concentration graph are presented in Appendix E. <br /> 4.0. SUMMARY AND CONCLUSIONS <br /> Based on the data collected from the site,AGE finds: <br /> • At the time of the December 2004 monitoring event,ground water flow was inferred to be <br /> towards the south and southwest, which is consistent with historical ground water flow <br /> directions. The ground water elevation increased an average of 1.33 feet between the third <br /> and fourth quarter 2004 monitoring events,but ground water was within the screen interval <br /> of the on- and off-site wells. <br /> • Historically, the highest concentrations of contaminants have been detected in the area of <br /> wells MW-2,located at the former UST location,and MW-4,located directly down-gradient <br /> ofthe former USTs.However,the concentrations of dissolved BTEX and TPH have steadily <br /> Advanced GeoEnvironmental,Inc. <br />