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Multi-Phase Extraction Pilot Test Report&Remedial Design Thrifty 5tados No 171 Page 4 Stockton,California November 30.2010 Depth to water readings indicated that groundwater in well TB-11 W was lowered from 44.65 feet bgs prior to extraction to 45.48 bgs, 0.83' feet of groundwater drawdown, after 24 hours of extraction at EW-5S. Groundwater in well VW-5 was lowered from 43.15 feet bgs prior to extraction to 43.50 bgs, 0.35 feet of groundwater drawdown. Groundwater drawdown during extraction from shallow well EW-5S was negligible in observation wells EW-5D and TB-7. The greatest vacuum response was observed in well TB-7, which ranged from 1.25 inches of water(in H2O)to 1.90 in H2O during extraction at well EW-5S. Vacuum response at well VW- 5 ranged from 0.60 in H2O to 0.75 in H2O. Minimal vacuum response were observe in wells EW-5D and TB-I IW. From mid-day October 26 to October 27, 2010, multi-phase extraction was performed at well EW-51) for a period of 24 hours at flow rates from 19 to 27 cfm. Concentrations of TPHg in influent vapor decreased from 192 ppm to 118 ppm after 24 hours of extraction. Concentrations of benzene decreased from 2.99 ppm to 2.77 ppm. Concentrations of toluene increased from 3.51 to 9.38 ppm. Concentrations of ethylbenzene and total xylenes increased from 0.961 ppm and 3.37 ppm to 2.33 ppm and 8.85 ppm, respectively. Concentrations of MTBE and TBA were below laboratory detection limits (non-detect). A total of 1,850 gallons of groundwater were extracted from well EW-5D at an approximate rate of 1.28 gallons per minute(gpm). Groundwater drawdown was observed in well VW-5 (0.24') after 24 hours of extraction at EW-5D. Groundwater depth in wells EB-5S, TB-7 and VW-5 rose from groundwater levels observed at the end of extraction from EW-5S due to drawdown from previous extraction. During extraction at EW-5D vacuum response in observation well TB-7 began at 1.25 in H2O and declined to zero after seven hours of extraction from well EW-5D. Minimal vacuum response was observed in wells EW-5S, TB-11 V,TB-1 IW and VW-5. On October 27 and 28, 2010, multi-phase extraction was performed at well TB-7 for a period of 24 hours. Concentrations of TPHg in influent vapor decreased from 136 ppm to 106 ppm after 24 hours of extraction. Concentrations of benzene decreased from 0.376 ppm to 0.108 ppm. Concentrations of toluene decreased from 2.43 to 0.388 ppm. Concentrations of ethylbenzene and total xylenes decreased from 0.963 and 3.996 ppm to 0.237 and 1.398 ppm, respectively. Concentrations of MTBE was reported as below laboratory detection limits at the beginning of the 24-hour test and 0.022 ppm after the test. Concentrations of TBA were below laboratory detection limits. A total of 1,280 gallons of groundwater were extracted from well TB-7 at an approximate rate of 0.89 gallons per minute (gpm). environ strategy consultants, inc.