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Site Background Information West Clay Properties <br /> Page 2 of 6 <br /> October 1999- Seven soil borings (B-10 through B46) were advanced to collect and analyze soil <br /> samples, in addition, one soil sample collected from boring B-11 was analyzed for permeability, <br /> porosity, total organic content and specific gravity Petroleum hydrocarbon-impacted soil was <br /> detected in soil samples collected from all soil borings except B-13,the highest concentrations were <br />' detected in soil samples collected from boring B-10, located adjacent to the former UST No 3 <br /> excavation <br />' July 2001 -An 8-hour step draw-down ground water extraction pilot test was conducted at the site <br /> High concentrations of petroleum hydrocarbons were detected in extracted ground water samples <br />' November 2004 - Based on the results of the July 2001 pilot test, a 24-hour constant rate ground <br /> water extraction feasibility test was performed at the site Detected concentrations of target analytes <br /> in extracted ground water samples were significantly lower than those reported for the July 2001 <br />' pilot test <br />' Ground Water Monitoring- Based on analytical results of ground water samples collected during <br /> quarterly monitoring and site assessment activities, the lateral extent of impacted soil has been <br /> defined to the north,east and west However,the vertical extent of the contamination plume,as well <br />' as the lateral extent to the south, is not well defined <br /> Cluster UST Area (North Area) <br /> December 1998 - Two 10,000-gallon USTs and one 6,000-gallon UST were removed from a <br /> common excavation at the site <br />' October 1999-AGE advanced one soil boring(B-9)for collection of soil and ground water samples <br /> Significant concentrations of petroleum hydrocarbons were detected in samples collected from the <br />' boring Based on the findings from boring B-9,monitoring wells MW-9 and MW-10 were installed <br /> near the former UST excavation area <br />' July 2000 - Nine pilot borings were advanced at the site for installation of monitoring wells <br /> MW-11A/B.through MW-13A/B, air-sparging well AS-1 and ground water extraction wells EW-1 <br /> and EW-2 Petroleum hydrocarbons were detected in soil samples collected from pilot bonngs EW-1 <br />' and MW-13B <br /> November 2002 - Four pilot borings were advanced at the site for installation of monitoring wells <br />' MW-14AB and MW-15A/B Target analytes were not detected above laboratory reporting limits <br /> in the soil samples submitted for analyses <br />' December 2003 - Approximately 340 cubic yards of petroleum hydrocarbon-impacted soil was <br /> excavated from the former UST location Soil was disposed of at Forward Landfill in Manteca, <br /> California Based on the low to non-detect concentrations of petroleum hydrocarbons in the soil <br /> Advanced GeoE nviron mental,Inc <br /> 1 <br />