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• Quarterly Summary Report <br /> First Quarter 2001 <br /> Tosca (Former Unocal) Service Station #4409 <br /> 1502 North El Dorado <br /> Stockton, California <br /> CITY Stockton <br /> COUNTY San Joaquin <br /> BACKGROUND <br /> The site is located on the northeast corner of Harding Way and El Dorado Street in Stockton, <br /> California The site is a former Unocal service station that retailed gasoline and diesel fuel On <br /> April 7, 1999, three 10,000-gallon capacity USTs were removed from the site Two USTs <br /> contained gasoline and one contained diesel fuel Initial remedial activities included source <br /> removal of obviously impacted soil to a depth of approximately 18 feet bgs beneath the center of <br /> the western fuel tank Additional remedial activities included source removal of obviously <br /> impacted soil in the area beneath the former dispenser and product lines A concrete pad <br /> restricted the lateral extent of excavation During excavation of impacted soil, unidentified <br /> fiberglass piping was found Additional excavation and sampling was completed on <br /> April 8, 1999 to remove the unidentified piping Samples were collected from the bottom and <br /> side walls of the excavated area Following removal of the former station canopy, canopy <br /> footings and kiosk, additional over-excavation was completed in the dispenser area Over- <br /> excavation was terminated when obviously impacted soil was removed, the structural integrity of <br /> the sidewalk was endangered, or groundwater was encountered Residual hydrocarbons remain <br /> in the soil and groundwater A total of approximately 1,707 tons of soil was transported offsite <br /> for disposal at the Forward Landfill in Manteca, California Four groundwater monitoring wells <br /> were installed in December 1999 Vertical assessment conducted in July 2000 identified soil and <br /> groundwater impacts at depths of 60 feet bgs The SJCPHS/EHD verbally requested a workplan <br /> for further delineation of soil and groundwater impacts Three on-site groundwater monitoring <br /> wells were installed in December 2000 The lateral and vertical extent of soil impacts is <br /> generally delineated Deep zone groundwater impacts were identified <br /> RECENT QUARTER ACTIVITIES <br /> • Developed and sampled deep monitoring wells installed during Fourth Quarter 2000 <br /> • Submitted Vertical Assessment Report <br /> 1� <br /> 822121/1 gsr01 2 03/13/01 <br />