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S E C 0 R <br /> . Mr Mike Infurna <br /> March 8, 2005 <br /> Page 3 <br /> Quarterly Summary Report <br /> Fourth Quarter 2004 <br /> Former 76 Service Station #4409 <br /> 1502 N El Dorado Street, Stockton, California <br /> City/County ID# Stockton <br /> County San�Joa uin <br /> BACKGROUND <br /> The site is located on northeast corner of North EI Dorado Street and East Harding Way in Stockton, <br /> California, and is a former operating Unocal service station <br /> On April 7, 1999, three 10,000-gallon capacity underground storage tanks (USTs), which contained <br /> gasoline and diesel fuel, were removed from the site The tank pit area was overexcavated <br /> Excavation dimensions were approximately 35 feet by 40 feet by 15 feet deep <br /> Initial remedial activities included source removal by excavation of obviously impacted sod to a depth <br /> of approximately 18 feet below ground surface (bgs) beneath the center of the western fuel tank <br /> Additional remedial activities included source removal by excavation of obviously impacted sod in the <br /> area beneath the former dispenser and product lines A concrete pad restricted the lateral extent of <br /> excavation <br /> During excavation of impacted soil, unidentified fiberglass piping was found Additional excavation <br /> and sampling was completed on April 8, 1999 to remove the unidentified piping Samples were <br /> collected from the bottom and sidewalls of the excavated area <br /> Following removal of the former station canopy, canopy footings and kiosk, additional over- <br /> excavation was completed in the dispenser area Over-excavation was terminated when obviously <br /> impacted soil was removed, the structural integrity of the sidewalk was endangered, or groundwater <br /> was encountered A total of approximately 1,707 tons of sod was transported off-site for disposal at <br /> the Forward Landfill in Manteca, California <br /> Four shallow groundwater-monitoring wells (MW-1 through MW-4) were installed in December 1999 <br /> to assess the potential for hydrocarbon impact to groundwater beneath the site (Attachment A) <br /> Vertical geoprobe assessment was conducted in July 2000, and sod and groundwater impacts were <br /> encountered at depths of 60 feet bgs (GP-1 through GP-4) <br /> The San Joaquin County Environmental Health Department (SJCEHD) subsequently requested a <br /> work plan for further delineation of soil and groundwater impacts Three on-site deep groundwater- <br /> monitoring wells (MW-5 through MW-7, Attachment A) were installed in November 2000 These <br /> wells identified deep zone groundwater petroleum hydrocarbon impacts In August and September <br /> 2001, three additional deep zone groundwater monitoring wells (MW-8 through MW-10, Attachment <br /> A) were installed on-site to determine the extent of deep zone groundwater impacts In June and <br /> . July 2003, four off-site deep zone groundwater monitoring wells (MW-11 through MW-14, <br /> 11ConocoPhillipslRetaii Sdes144091Qssrs12004W02004_QSR doc SECOR lntemahona!Incorporated <br />