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,• E a Ms Lon Duncan April 4, 2000 0 Page 2 of 6 entrance and approximately 53 feet west of the entrance to the alley that borders the east side of the building The UST was removed under permit from San Joaquin County Public Health Services, Environmental Health Division (PHS/EHD) on March 26, 1997 A soil sample collected from beneath the tank contained elevated levels of petroleum hydrocarbons, lead, and chlorinated solvents Analytical results are summarized in Table 1 Based on these data, PHS/EHD requested a workplan to investigate the lateral and vertical extent of contamination The August 24, 1998 Workplan prepared by Ground Zero proposed a general scope of work consisting of drilling and sampling soil borings in the vicinity of the former UST to further investigate the vertical and lateral extent of residual soil contamination and to determine of groundwater had been impacted The initial investigation, performed on January 19, 1999, determined that soil and groundwater in the vicinity of the former waste oil UST has been impacted by petroleum hydrocarbon constituents and lead The vertical extent of soil contammation in the vicinity of the former waste oil tank has been defined However, due to slow drilling progress attributed to very tight soil conditions, only three of the four proposed borings were completed and the full lateral extent of soil and groundwater contamination could not be determined Analytical results of the initial investigation are presented in Tables 2 and 3 Soil boring locations are shown on Figure 2 The results of the investigation were presented to PHS/EHD in the Subsurface Invesugatron Summary Report(Ground Zero Analysis,May 20, 1999) By letter dated June 21, 1999 PHS/EHD commented on the report and directed the responsible party to submit a workplan for additional investigation A workplan addendum for additional investigation was submitted to PHS/EHD on August 19, 1999 Investigations Undertaken Per the directive of San Joaquin County PHS/EHD, five additional soil borings were advanced by Ground Zero to further define the extent of soil and groundwater contamination at the site Boring SB4 was located approximately 15 feet southeast of the former UST, boring SB5 was located approximately 8 feet east of the former UST, boring SB6 was located approximately 19 feet northwest of the former UST, boring SB7 was located approximately 39 feet northwest of the former UST, and boring SB8 was located approximately 36 feet north of the former UST Soil boring locations are shown on Figure 2 INVESTIGATIVE PROCEDURES On October 26 and 27, 1999, Sean Garvey of Ground Zero supervised the subsurface investigation in the vicinity of the former UST Ms. Lori Duncan of San Joaquin County PHS/EHD conducted the site inspection and observed field activities Fisch advanced the borings under the supervision of field geologist Sean Garvey, and project manager John Lane, a California Registered Geologist Bonngs SB4, SB5, SB7 and SBS were advanced to depths of approximately 31 feet below ground surface (bgs), and boring SB6 was advanced to . approximately 37 feet bgs Fisch utilized a truck mounted Geoprobe 5400 direct push ng to advance the borings and collect soil samples Soil samples were collected at 5-foot intervals using a 1 % -inch diameter by 24-mch long core sampler The sampler was lined with clear acetate sleeves, affording sroundzelgabbudladd_bonng_tpt doe