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' RM Associates 701-0102 To address the remediation of soil and groundwater impacted by a leaking underground gasoline storage tank, in July 1997, On-Site Technologies, Inc prepared a Corrective Action Plan(CAP) for the site The report was approved by the San Joaquin County Public Health Services Environmental Services Division as an Interim Remedial Action Plan pending demonstrated effectiveness of the ' measures proposed in the Plan To provide clarity many of the elements of the July 1997 report have been excerpted and presented herein, rather than simply making reference to the previous report However, referral to the earlier report is recommended for the most comprehensive detail(see ' references listed under Section 7 0) 21 Investigative History Subsequent phases of site investigation involving groundwater monitoring well installations were ' conducted on three occasions In December 1989, Blymer installed three monitoring wells,presently designated as BEI-MW1, BEI- ' MW2, and BEI-MW3 Prior to the monitoring well installation in November 1989, a soil boring designated as BEI-13-9 had been drilled adjacent to the UST The record indicates that monitoring well BEI-MW3 is located within a few feet of BEI-13-9, although the exact relative position is not ' precise In November 1991, SRK installed thrce monitoring wells and two test borings The monitoring wells are designated on the site plan Figure 2 as SRK-MWI, SRK-MW2, and SRK-MW3 In April 1996, Park installed two monitoring wells on the Union Pacific Railroad property ' immediately adjacent to the south boundary of the site The wells are designated as MW-7 and MW- 8 Their respective locations are illustrated on the site plan (Figure 2) ' In October 1997, On-Site Technologies, Inc installed four groundwater extraction wells The wells are designated on Figure 2 as EW-1 through EW-4 iThe well construction details for all of the wells cited above are presented in Table 1 ' 22 Soil Investigation The soil boring logs and geologic cross-sections presented below indicate what has already been ' confirmed by the remediation effort at the site, that the proposed and performed soil vapor and groundwater extraction is an effective method for reducing hydrocarbon concentrations in the soil and groundwater at this site ' 22.1 Soil Boring Logs Soil boring logs are presented as Item I in Appendix A Page 2 of 11