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City of Stockton A68104.02B <br /> August 28, 1996 Page 7 <br />' Material (ie , seal, bentorute clay, and filter pack sand) removed from the borehole by <br /> overdnlling as well as the decontamination rulsate generated by the cleaning of the drill <br /> tools were placed in United States Department of Transportation approved drums. The <br />' drums were sealed, labeled and left at the site for disposal by the client as recommended <br /> in the following section <br />' 4.1 Disposal of Drill Cuttings and Decontamination Rinsate The analytical results of <br /> soil and groundwater samples collected from the soil borings and monitoring well installed <br /> during the assessment work did not detect PPCs Based on these analyses, it is presumed <br /> that the drill cuttings and decontamination rinsate do not contain detectable concentrations <br /> of PPCs Therefore with the approval of SJCPHS, it is recommended that the City of <br /> Stockton dispose of this material on site Dell cuttings may be used in routine landscape <br /> tmaintenance for fill dirt. Decontamination ansate may be discharged for irrigation on the <br /> ground surface Well casing was disposed of in normal waste disposal containers. <br />' <br /> 5.0 CONCLUSIONS <br /> Based on the findings of the soil and groundwater assessment work (Twining, 1995), and on <br /> the completion of the well destruction as here-in documented, Twining offers the following <br /> conclusions. <br /> • PPC migration in soil appears to have extended vertically no deeper than 20 feet <br />' BSG beneath the former UST location, <br /> • PPC migration in soil appears to have extended laterally no more than 10 feet from <br />' the former UST location, <br /> • The total mass of PPCs remaining in soil at the site appears to be no greater than <br /> 4.2 pounds, which represents a volume of approximately 0 7 gallons; <br /> • Based on analytical results of groundwater sampling analysis, it does not appear that <br /> PPCs in soil have migrated to groundwater below the former UST location, and <br /> • The monitoring well MW-1 at the site has been properly destroyed consistent with <br /> the SJCPHS and State of California requirements <br />