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Site Characterization Report: 7500 West Eleventh Street, Tracy, CA. Page 5 <br /> �F a <br /> _�.. <br /> with low concentrations of associated BTEX compounds, and MTBE from less than <br /> detectable concentrations to 4.5 mg/Kg. (The San Joaquin Company Inc. 1999.) <br /> 2.6 Back-filling of Excavations <br /> To secure the site, gravel with particle sizes in the range 3-in. to 1.5-in with very little <br /> fines was placed in the bottom of Tank Pit No. 1, from which the four registered storage <br /> tanks had been removed, until the gravel's surface was just above the water table. It was <br /> t then compacted by vibration so that the bottom of the pit was stable and dry. The <br /> remainder of the pit was then filled with clean overburden and other material that had <br /> is <br /> covered the tanks. Available material from the excavations of the tank pits was also used <br /> to backfill Tank Pit No. 2 and similar material was used to back-fill the Dispenser Pit,but <br /> a sheet of industrial plastic was laid over the bottom of that open pit before the backfill <br /> material was placed. <br /> At the request of the SJCPHS, six samples from various depths between 4 and 6 ft. were <br /> recovered from the materials used to backfill the Dispenser Pit and analyzed for TPHd, <br /> TPHg, the BTEX compounds, fuel oxygenates and total lead. (The San Joaquin Company <br /> Inc. 1999.) All six samples contained diesel at various concentrations between 69 mg/Kg <br /> and 4,100 mg/Kg. Gasoline was detected in only two of the samples at 2.2 mg/Kg and <br /> 760 mg/Kg. All samples contained extremely low concentrations of one or more of the <br /> BTEX compounds. MTBE was detected in four of the six samples, but this analyte was <br /> also at extremely low concentrations. The concentration of lead in the samples varied <br /> ? >' from Not Detectable to 11 mg/Kg, which is within the range naturally present in soil in <br /> the Tracy area. (The San Joaquin Company 2000.) <br /> 2.7 Disposition of Stockpiled Soil <br /> It was originally planned to treat the remaining stockpile of affected soil on-site by <br /> ' aeration and bioremediation. However, at the direction of the SJCPHS, that material, <br /> which amounted to 521.25 tons, was loaded onto trucks on November 5, 1999 and <br /> transported for disposal at Forward's, Class 11 disposal facility in Manteca, California. <br /> F <br /> 1 <br /> sic <br /> i , <br /> � r <br />