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0001491cal7',WhAcstnc. Page 3 Additional Site Characterization Work Plan Project No.724.2 March 8,2005 Monitoring Report" dated November 12, 2004 we recommended performing a Cone Penetrometer Testing (CPT) investigation to further define the cross gradient extent of the plume north of MW-108/208 and the down gradient extent east of the well set MW-109/209. SJC/EHD directed the submittal of a work plan to update the site conceptual model by CPT borings. The following sections include the work plan to advance the CPT borings. r 2.0 PROPOSED INVESTIGATION TPH-gasoline range contaminant concentrations in the monitoring wells are low enough to consider the site closure issue. However, the groundwater monitoring results suggests that there may be an off-site source of contamination that is mixing with the northern portion of the subject plume along Charter Way and the down gradient extent of the plume to the east is undefined beyond well MW-209. Therefore, groundwater/soil investigation is necessary to delineate the groundwater plume margins and to update the site conceptual model. GTI r recommended performing Cone Penetrometer Testing (CPT) to the north of MW-108/208 and to the east of MW-109/209 to define the ground water plume margin in our r "Groundwater Monitoring Report, Yd Quarter 2004" dated November 12, 2004. CPT technology will limit mobilizations to the site and will allow investigation above and below the groundwater table. More information on the CPT process is included below in Section 3.1. GTI proposes to install two CPT boreholes to the south side of Charter Way and two CPT boreholes east of the site on Aurora Street (see Figure 3 for locations of the CPT boreholes). r 3.0 CONE PENETROMETER TESTING & SAMPLING The following sections describe CPT technology and the sampling procedures for obtaining discrete soil and groundwater samples. 3.1 Cone Penetrometer Testing CPT uses specialized technology to determine subsurface lithology. It consists of using large truck to apply massive force to drive a cone at the head of rods through the subsurfa( Friction, pore water pressure and tip resistance are measured as the cone moves downy and these values can be correlated to determine the type of soil present. Once this liths, W information is collected, a second hole is advanced next to the first. The second bore' advanced for the purpose of collecting discrete soil and groundwater samples. The 0 these samples will be selected by GTI staff in the field for optimal site characterizat;