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cieologual hckjucs lie Page 3 Valentine(Castle Motors) ' Report—Additional Site Charactenzation Project No7232 21 20 January 21,2004 Geological Technics Inc (GTI) submitted our June 27, 2002 "Add-tional Site Characterization Work Plan - Monitoring Well Installation"work plan to meet the SJC/EHD directive The plan included a site conceptual model, geologic cross sections and it summarized the historical site investigation work The work plan also proposed a single on- site deep well to define the vertical extent of the groundwater plume and sax sets of off-site monitonng well clusters to define the lateral extent of the contamination ' In their letter correspondence dated October 22, 2002, the SJC/EHD reviewed GTI's June 27, 2002 work plan and made several comments the deep well was denied approval as not necessary at this time, only three of the sax off-site well locations were approved, the first borehole should be continuously logged, and they required that continuous multi- chambered tubing (CMTTM) wells be used instead of discretely screened, multiple PVC wells GTI responded by submitting our October 29, 2002 work plan addendum that incorporated and addressed the concerns raised by SJC/EHD The following sections summarize the field activities that were completed according to the ' approved June 27, 2002 GTI work plan 2.0 SOIL & GROUNDWATER INVESTIGATION To further investigate the lateral extent of soil and groundwater impacted with petroleum hydrocarbons, GTI supervised the installation of three continuous multi-chambered tubing (CMTTM) wells on November 20 —26, 2003 (MW-7, MW-8 and MW-9, respectively) Each CMTTM well was constructed with three discretely screened intervals with the bottom cap comprising an integral fourth screen at the terminal depth The MW-7 CMTTM well ' borehole was installed across E Castle Street approximately 120 feet northwest of the location of the former dispenser island The MW-8 CMTTM well borehole was placed across N El Dorado approximately 140 feet east of the location of the former dispenser island in the predominant down gradient groundwater direction The MW-9 CMTTM well ' borehole was placed in an up gradient location on W Adams Street approximately 220 feet from the former dispenser island See Figure 2 for borehole locations 2.1 Soil Borings 1 Prior to commencing work, a soil boring/monitoring well permit was secured from the County, an encroachment permit was secured from the City of Stockton and the SJC/EHD was notified at least 48 hours in advance The subsurface was cleared of underground utilities by notifying Underground Service Alert Borings MW-7, MW-8, and MW-9 were drilled using an 8 00-inch outside diameter continuous flight hollow stem auger owned and operated by V&W Drilling of Isleton, CA (C57# 720904) The shallow borings were advanced to approximately 95 feet below grade surface (bgs) Groundwater was encountered in the boreholes at approximately 36 5 feet bgs ' 2.2 Soil Sampling Procedure In accordance with SJC/EHD directives, the first borehole (MW-7) was continuously cored for geological evaluation from the depth of first water (36 ft) to total depth In the other two