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City of Stockton, Fire Station No. 12 A68105.01 <br /> August 7, 1995 Page 10 <br /> specific parameters that are considered in this analysis include; depth to groundwater below <br /> contaminated soil, subsurface fractures, average annual precipitation, man-made conduits, <br /> and unique site features (i.e. recharge area, coarse soil, nearby wells, etc.). <br /> The site specific parameters used in the leaching potential analysis are outlined as follows. <br /> • Groundwater depth - 50 feet BSG <br /> • Subsurface fractures - none observed <br /> low <br /> • Average annual precipitation - 10 to 25 inches <br /> .,� • Man-made conduits - none observed <br /> • Unique site features - none observed <br /> The soil sampling location which analytical results indicated the greatest concentrations of <br /> PPCs were selected for the leaching potential analysis (i.e. soil boring B-2 at 10 feet BSG). <br /> Copies of this analysis is presented in Appendix D. The application of the leaching <br /> potential analysis indicate that the PPC impacted soils in the vicinity of the former UST <br /> location at the depth of 10 feet BSG do not appear to pose a potential threat to <br /> groundwater quality. <br /> 6.5 Disposal of Drill Cuttings and Decontamination Rinsate: Based on soil sample <br /> analytical results and the criteria published in Appendix C of the Leaking Underground Fuel <br /> _ Tank (LUFT) Field Manual, it appears that the drill cuttings and decontamination rinsate <br /> do not contain hazardous concentrations of PPCs. However, this material should be <br /> �► disposed and/or treated of in an appropriate manner. <br /> 7.0 CONCLUSIONS <br /> • The soil profile at the site consists of interbedded strata of sand with silt or clay and clay <br /> alternating with strata of silt; <br /> • The vertical extent of PPC migration appears to extend no deeper than 15 feet BSG in <br /> the soil beneath the former UST location; <br /> • The lateral extent of PPC migration does not appear to extend greater than 2 to 4 feet <br /> beyond the north and south boundary, respectively, of the former UST excavation; <br /> • The volume of impacted soil was estimated to be 75.4 cubic yards, the mass of impacted <br /> soil was estimated to be 113 tons, the area of impacted soil was estimated to be 28.3 <br /> square yards, the mass of fuel released was estimated to be 5.2 lbs of gasoline and 4.3 <br /> L lbs of diesel, and the volume of fuel released was estimated to be 0.8 gallons of gasoline <br />