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Quarterly Summar ort <br /> . Y Report <br /> Third Quarter 2001 <br /> Tosco (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 underground storage tanks (USTs) were removed <br /> from the site Two USTs contained gasoline and one contained diesel fuel Initial remedial <br /> activities included source removal of obviously impacted soil to a depth of approximately 18 feet <br /> below ground surface (bgs) beneath the center of the western fuel tank Additional remedial <br /> activities included source removal of obviously impacted soil in the area beneath the former <br /> dispenser and product lines A concrete pad restricted the lateral extent of excavation During <br /> excavation of impacted soil, unidentified fiberglass piping was found Additional excavation and <br /> . sampling was completed on April 8, 1999 to remove the unidentified piping Samples were <br /> collected from the bottom and side walls of the excavated area Following removal of the former <br /> station canopy, canopy footings and kiosk, additional over-excavation was completed in the <br /> dispenser area Over-excavation was terminated when obviously impacted soil was removed, the <br /> structural integrity of the sidewalk was endangered, or groundwater was encountered Residual <br /> hydrocarbons remain in the soil and groundwater A total of approximately 1,707 tons of soil <br /> was transported off-site for disposal at the Forward Landfill in Manteca, California Four <br /> groundwater monitoring wells were installed in December 1999 Vertical assessment conducted <br /> in July 2000 identified soil and groundwater impacts at depths of 60 feet bgs The SJCPHS/EHD <br /> verbally requested a workplan for further delineation of soil and groundwater impacts Three on- <br /> site groundwater monitoring wells were installed in December 2000 The lateral and vertical <br /> extent of soil impacts is generally delineated Deep zone groundwater impacts were identified <br /> Three groundwater monitoring wells were installed in August and September 2001 <br /> RECENT QUARTER ACTIVITIES <br /> Conducted groundwater monitoring of shallow and deep wells <br /> Submitted Quarterly Status Report <br /> Installed three additional deep groundwater monitoring wells <br /> 4409/822121 lba doe 2 10/18/01 <br />