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{ Multi-Phase Extraction Pilot Test Report &Remedial Design' Thrifty Station No 171 Page 5 Stocldon,Calirornia 'a November 30,2010 Groundwater drawdown was greatest in observation well TB-12W (0.24') after 24 hours of extraction at TB-7. Groundwater drawdown in observation F wells EW-5D and VW-5 were measured as 0.17' and 0.13% respectively, after 24 hours of drawdown. Groundwater drawdown from observation well TB-I 1 W was measured as 0.13'. Groundwater in observation well EW-5S increased slightly due to drawdown from previous extraction. is During extraction at TB-7 the largest vacuum response observed was.in well TB-12W (2.25 in ; H2O). 'Vacuum response observed in well VW-5 ranged from 0.50 in H2O to 0.65 in H2O. Vacuum response observed in wells EW-5S, EW-51), TB-I IV and TB-I IW ranged from 0.00 in H2O to 0.15 in H2O. I L From October 28 to 30, 2010, multi-phase extraction was performed'at wells EW-51), EW-5S, and TB;k-7 simultaneously for a period of 48 hours. Concentrations of TPHg in combined influent vapor increased from 73 parts per million (ppm) to 287 ppm after 24 hours of extraction. Concentrations of benzene increased from 0.073 ppm to 1.19 ppm. Concentrations of toluene increased from 0.462 to 8.05 ppm. Concentrations of ethylberizene and total xylenes increased from 0.383 ppm and 1.967 ppm to 1.38 ppm and 10.33 ppm;.respectively. Concentrations of MTBE in the combined influent was reported as non-detect at the beginning of the 48 hour test and 896 ppm at the end of the 48 hour test: IN Concentrations`of TBA were below laboratory detection limits. A total of 9,170 gallons of groundwater were,extracted during the 48 hours at an approximate rate of 3.18 gallons per minute (gpm). f During extraction from wells EW-5D,EW-5S, and TB-7, groundwater'drawdown was greatest in well VW-5 (0.37') Groundwater drawdown: in well TB-9W was measured as 0.34'. Groundwater depth decreased in observation wells TB-i IV and TB-12V. Vacuum response after 24 hours of extraction from wells EW-513; EW-5S, and TB-7 was greatest in well TB-12W (2.20 in H20). Vacuum response observed in well V W-5 ranged from 0.50 in H20-to 0.60 in H2O. Vacuum response observed in wells TB-6, TB-9V, TB-9W, TB-I 1 V and TB-11 W and TB-12V ranged from 0.00 in H2O to 0.15 in H2O. si Influent concentrations of TPHg in vapor during pilot testing were, significantly higher than previous vapor sample results during MPE system operation. Previous�influent concentrations of TPHg in combined influent was 74 ppm (6104109), compared to 287 ppm during testing from all three wells on 10130110. Previous individual well concentratiohs of TPHg in well.EW-5S was 210 pplil (8116109), compared to 436 ppm during testing from all,three wells on 10/30110. Previous individual well concentrations of TPHg.in well TB-7 was 31 ppm (6111109), compared h to 420 ppm during testing from all three wells on 10/30/10. Pr'eviousl individual vapor samplesu were not collected from well EW-5D. environ strategy consultants; inc.