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%woe � <br /> down to reverse the present northeasterlyflow of that <br /> portion of groundwater impacted by petroleum hydrocarbons <br /> (the hydraulic gradient at the site is low. . . about 1/4 inch <br /> per foot) . <br /> Soil Vapor Extraction <br /> Vapor and liquid phase (sorbed) contaminants in vadose soil <br /> will be removed using Soil Vapor Extraction ( SVE) tech- <br /> nology. As you know, SVE systems operate on the principle <br /> that many components of gasoline will volatilize at ambient <br /> soil temperatures , with the volatilized contaminants then <br /> entering the void spaces between soil particles until <br /> equilibrium is achieved. when an appropriate vacuum is <br /> applied to the soil the vapors are removed from the soil <br /> pore spaces . This partitioning is described by Henry 's Law <br /> Constant and Raoult ' s Law. <br /> It is our intention to use an electrically powered, three <br /> horsepower Masport M Series Model M20F Vacuum Pump with a <br /> maximum draw of 53 scfm, or its equivalent , to draw vapors <br /> from contaminated vadose soil . Gasoline vapors located <br /> between 1 and 7-8 feet below ground surface (bgs) will be <br /> drawn through 0 . 020" slotted PVC casing and into the <br /> aforementioned aerobic bioreactor system where they will be <br /> dissolved in water and biologically degraded. Initially, <br /> the existing groundwater monitoring well MW-1 will be used <br /> as the extraction point , with additional wells being placed <br /> as necessary. <br /> Concentrations of Total Petroleum Hydrocarbons as Gasoline <br /> (TPH-G) and benzene, toluene, ethylbenzene, and xylenes <br /> (BTEX) will be monitored by sampling the air stream with a <br /> Tedlar sample bag or evacuated cannister . The frequency of <br /> sampling will depend on system performance, but a sample <br /> will be taken to establish an initial base line and <br /> periodically, thereafter, to determine the progress' of <br /> remediation. <br /> It is proposed that the SVE extraction system operate 16 <br /> hours per day, 7 days per week with an anticipated project <br /> life of no more than 6 months , or as otherwise specified <br /> within the Permit for Authority to Construct to be acquired <br /> from the San Joaquin Valley Unified Air Pollution Control <br /> District (SJVUAPCD) . <br /> As contaminants are removed during SVE, the residual soil <br /> contamination level decreases and less volatile compounds <br /> comprise a greater portion of the residual contamination. <br /> Page 11 <br />