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Biwa Ms Mary Meays 11 November 29, 1995 (9347-0020) • Evaluate data and prepare this technical report presenting the results of this investigation Site Description and Background The site is located on the southeast corner of the intersection of Pacific and Porter Avenues in Stockton, San Joaquin County, California In addition, the site is located in Section 21, Township 2 North, Range 6 East as shown on Figure 1 The results of previous site assessments and the removal of the steel fuel USTs were documented by Aegis Environmental, Inc in reports dated June 18, 1990, and January 4, 1991 The historical estimated ground water flow direction has been predominantly to the southeast Total petroleum hydrocarbons as gasoline (TPH-G) and benzene were detected at up to 12,000 and 110 parts per million (ppm), respectively, in the soil samples collected from well VEW-2 The extent of adsorbed-phase petroleum hydrocarbons appeared to be limited to the area beneath the former UST basin In late 1991 and early 1992, a 75-day vapor extraction test was performed onsite by Aegis Environmental, Inc During the test, vapors were extracted from wells VEW-1, VEW-2 and MW-3 Wells VEW-1 and VEW-2 were installed to address petroleum hydrocarbons in soil •� beneath the former steel USTs According to the Thini Quarter 1995 Ground WaterMonitonng Report prepared by Fugro on November 9, 1995, depth to ground water at the site is approximately 48 feet bg The October 5, 1995 ground water monitoring data indicates that the ground water flows in a northwesterly direction with a hydraulic gradient of 0 001 foot per foot Separate-phase petroleum hydrocarbons have been observed only in well MW-3, but have not been observed since August 1993 Dissolved-phase petroleum hydrocarbons have not been detected above reported laboratory detection limits in the water samples collected from well MW-1 since the February 1995 sampling event Pertinent excerpts of reports containing the laboratory results of the previous investigations are included in Attachment 2 Soil Boning Advancement and Sampling On September 21 and 22, 1995, Fugro personnel supervised the advancement and sampling of soil borings GE-01 through GE-04 (Figure 2), by Vironex of Foster City, California, using a GeoProbe sampling system The mobile hydraulically-driven GeoProbe sampling system advanced 1-114 inch diameter push rods up to 56 feet bg (GE03) GE01 was advanced on the southeast corner of the site GE02 was advanced approximately 9 feet east of the location of boring VEW-2 GE03 was advanced in the northwest portion of the site, approximately 3 5 feet northwest of the location of VEW-2 GE04 was advanced near the southern boundary of the site, approximately 8 feet south of well MW-3 93470200 ARP -2-