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ATC Associates Inc (: VY 1117 Lone Palm Avenue, Suite B J%TcModesto, California 95351 209-579-2221 AS S O C I ATE S INC fax 209-579-2225 In late April 1988, the open excavation associated with the former USTs was expanded by excavating petroleum impacted vadose zone soils Kleinfelder's Soil Removal Report dated May 3, 1988, approximately 350 to 400 cubic yards of soil were excavated from April 25 to 28, 1988 Laboratory analyses of soil samples collected from the sidewalls of the enlarged excavation indicated low concentrations of petroleum hydrocarbons remained at the south and southeastern portion of the excavation On February 26, 1993, Parker Environmental Services (P E S ) advanced seven soil bonngs (BHI through B117) Soil samples were collected from each boring and a groundwater sample was collected from each boring except BH7 Petroleum hydrocarbons were detected in soil samples collected from all the bonngs except BHI and BH3 Petroleum hydrocarbons were detected in all of the groundwater samples Water level measurements collected at the site on March 2, 1993 indicated the groundwater flow direction was to the southeast Refer to P E S 's Interim Report on Subsurface Investigation Work at Cheaper # 37 for more details From July to October 1995, P E S conducted subsurface investigation activities that included mstalling four monitoring wells (MW5 through MW8) and advancing 14 hand augured soil borings (138 through B21) Borings B15 through B21 were advanced off-site to the west, southwest, and south Groundwater was encountered at approximately 6 5 feet bgs Soil and groundwater samples were collected from B8, BIO through B18, B20, B21, and MW5 through MW7 A groundwater sample was also collected from MW8 Petroleum hydrocarbons were '� ''5j detected in all of the soil samples except for the samples collected from MW/through MW7, B14 SPN1 located east of the former UST location, and B20 and B21 located off-site to the southwest and south, respectively Petroleum hydrocarbons were detected in the groundwater samples except for the samples collected from B14, B20, B21, MW1, MW2, MW3, MW6, and MW7 MW4 was not sampled due to the presence of approximately 0 02 inches of free product The reported groundwater flow direction on September 25, 1995 was approximately due north Refer to the report prepared by P E S titled Environmental Site Investigation Methods and Findings Drilling of Soil Borings, Drilling and Installation of Groundwater Monitoring Wells Collection and Analyses of Soil and Groundwater Samples, dated November 17, 1995 for more information In a letter dated April 11, 2002, the San Joaquin County Environmental Health Department (EHD) indicated that upgradient monitoring wells MW2 and MW3 could be reduced to annual monitoring and that the lateral and vertical extent of soil contanunation remains undefined The EHD requested submittal of a workplan to define the lateral and vertical extent of soil contamination In response to the EHD request, H2OGEOL submitted the Work Plan for Additional Soil Characterization dated June 10, 2003, which proposed advancing 14 hand auger borings at the site for the purpose of collecting soil samples In a letter dated November 14, 2003, the EHD indicated that the proposed scope in the H2OGEOL workplan was not adequate or necessary The EHD requested that a workplan be prepared in the context of a site conceptual model that includes analytical data collected during removal of a waste oil tank from the site in September 2003 The requested workplan was submitted by ATC on February 2, 2004 s lenvumnenW\25847\0037Veportsl3gr-2004 dw 2 J