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i <br /> Ms. Mary Ways <br /> Quarterly Summary Report <br /> September 18, 1992 <br /> Page 2 <br /> The non-detectable to trace levels of BTEX compounds reported during the last two quarterly <br /> groundwater monitoring events suggest that operation of the soil vapor extraction system may be <br /> enhancing volatilization of dissolved fuel hydrocarbons present in groundwater underlying the former <br /> underground storage tank. This conclusion will be evaluated further with additional groundwater <br /> monitoring data. The next quarterly groundwater monitoring event is scheduled for November 1992. <br /> SOIL REMEDIATION <br /> In early April 1992, SEACOR installed a soil vapor extraction system at the site. The as-built system <br /> consists of a single vapor extraction well screened from 20 to 40 feet below ground surface, a trailer- <br /> mounted regenerative blower with a 200 cubic feet per minute (CFM) capacity, and two in-line <br /> granular activated carbon vapor phase treatment vessels (2,000 pound and 200 pound capacity). The <br /> vapor extraction and treatment equipment are all housed within a fenced compound. <br /> SEACOR began operating the soil vapor extraction system on April 15, 1992. Prior to and during <br /> system start-up, a representative from the San Joaquin Valley Unified Air Pollution Control District <br /> (SJVUAPD) inspected the system and provided SEACOR with an approval to operate. TPHg and <br /> •� BTEX concentrations in the influent vapor stream continue to show a decreasing trend. As of <br /> August 12, 1992, an estimated 207 pounds of gasoline had been removed from the subsurface soils. <br /> SEACOR is currently monitoring system operation in accordance with the requirements of the <br /> permit to operate from SJVUAPD. A copy of the August monthly status report provided to the <br /> SJVUAPD is included as an attachment to this letter. <br /> SEACOR plans to continue operating the soil vapor extraction system while TPHg and BTEX <br /> concentrations in the influent stream continue to show a declining trend. Soil vapor extraction will <br /> be discontinued when influent concentrations decrease to insignificant levels or stabilize. Following <br /> sytem shutdown, SEACOR will advance a soil boring adjacent to the vapor extraction well and <br /> collect subsurface soil samples to evaluate residual hydrocarbon concentrations. <br /> Please feel free to contact me at (415) 296-7877 if you have any questions or comments regarding <br /> this letter. <br /> Sincerely yours, <br /> Sci • & EngineeringAnalysis Corporation <br /> Bruce E. Scarbrough, R.G. #4931 <br /> Principal Geologist <br /> iAUG.QSR <br /> 50014-001-05 MK01 <br />