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I T Multi-Phase Extraction. Pilot Test Report&Remedial Design Thrifty Station No 171 Page 3 Stockton,California November 30,2010 operation, every four hours for the first 24 hours of operation,and every four hours for the final 12 hours of operation. 2.1 Permitting and Notification Thermally treated vapor was released to the atmosphere in accordance with the air discharge permit and a groundwater discharge permit was obtained from the City of Stockton for the discharge of treated groundwater to the sanitary sewer. The San Joaquin County Environmental Health Department was notified 10 days in advance of field activities. 2.2 Health and Safety. Field work was conducted in a manner consistent with the approved site-specific Site Health and Safety PIan (HASP). Environ Strategy personnel and subcontracted employees were required to read and acknowledge understanding of the HASP prior to initiating work. A site health and safety "tailgate" meeting was held at the start of each work day to review specific potential physical, mechanical,chemical, and biological hazards. 2.3 MPE Pilot Test Results For the first 24 hours of testing, on October 25 and 26, 2010, extraction consisted of pulling a vacuum and extracting groundwater with a downhole pump capable of removing up to ten gallons per minute (gpm)from well EW-5S. Influent vapor samples were collected after the first hour and at the end of 24 hours, and submitted to Associated Laboratories, a state-certified laboratory, for analysis of total petroleum hydrocarbons quantified as gasoline (TPHg), benzene, toluene, ethyl-benzene, total xylenes (BTEX), methyl tert-butyl ether (MTBE), and other fuel oxygenates TBA, DIPE, ETBE, and TAME. Depth to water was measured hourly in monitoring wells EW-51), TB-7,TB-11 W,and VW-5. Vacuum response from wells EW-5D,TB-7, TB-1 I V, TB-11 W, and VW-5 were recorded hourly. Influent concentrations of VOCs were recorded hourly as well. Based-on laboratory analytical results, concentrations of TPHg in influent vapor increased from 27 parts per million (ppm) after one hour of extraction to 32 ppm after 24 hours of extraction at flow rates from 50 to 60 cubic feet per minute (cfm) . Concentrations of benzene decreased from 2.61 ppm to 2.51 ppm. Concentrations of toluene increased from 1.26 to 1.76 ppm. Concentrations of MTBE deceased from 9.50 ppm to 3.42 ppm and TBA decreased from 5.82 ppm to 1.35 ppm. Concentrations of etbylbenzene and total xylenes decreased from 0.579 ppm and 2.74 ppm to 0.521 ppm and 2.43 ppm, respectively. A total of 660 gallons of groundwater were extracted from well EW-5S at an approximate rate of 0.46 gallons per minute (gpm). Due to groundwater extraction rates being well below the capacity of the downhole pump, the extraction wells are assumed to be fully dewatered throughout pilot testing. • enviran strategy consultants, inc.