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1 C"ealogical Tecwcs 1tW Page 5 1 Additional Site Characterization Report Project No 662 2 February 20,2004 ' 2.2 Cone Penetrometer Testing ' Cone penetrometer testing (CPT) uses specialized technology to determine subsurface lithology It consists of using a large truck to apply massive force to drive a cone at the head of rods through the subsurface Friction, pore water pressure and tip resistance are ' measured as the cone moves downward and these values can be correlated to determine the type of soil present ' Prior to commencing work, encroachment & soil bonng/momtoring well permits were secured from the City of Manteca and the SJC/EHD The SJC/EHD was notified at least 48 ' hours in advance The subsurface was cleared of underground utilities by notifying Underground Service Alert On December 1 — 4, 2003, Gregg Drilling & Testing Inc (Gregg) of Martinez, California (C57#656407) mobilized to the site to perform the CPT boreholes The CPT testing began with a single deep boring CPT-4 to a depth of 80 feet bgs in the vicinity of existing deep ' well MW-104 (see Figure 2) The purpose of this boring was to determine the lithology lower than the terminal depth of the MW-104 boring (55 feet bgs) because the SJC/EHD stated that the vertical extent of the plume was undefined in that location After this borehole was completed, the rig was moved several feet and a new hole was advanced for the purpose of obtaining discrete water and soil samples ' The remainder of the CPT boreholes were advanced in similar fashion The CPT locations are designated as "CPT- X" in Figure 2 CPT locations CPT-1, CPT-2 and CPT-3 were ' placed in proximity to existing wells MW-I through MW-3 CPT-5 was placed approximately 40 southwest of the dispenser island to provide up gradient data CPT locations CPT-6, CPT-7 and CPT-8 were placed approximately 70 feet north, northeast and east of, respectively, the former UST excavation 2.3 Soil Sampling Procedure ' Soil sample depths were targeted to complete a site conceptual model illustrating the lateral and vertical extent of the soil plume at the site Gregg utilized a piston type soil sampler to ' obtain samples at depths designated by the field geologist The sampler contained two 6- inch brass sleeves designed to hold the soil sample When assembled it was attached to the end of the drill rods and then advanced to the targeted depth When the targeted depth was ' achieved, the rods were retracted 12 — 18 inches to allow the cone to slide upward into the hollow core of the sampler The rods were then advanced downward to allow soil to fill the empty brass sleeves and then the drill rods were removed to bring the core sample to the surface