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i Mr. James Barton, PG 24 April 2014 Page 4 • Notify USA a.minimum of two business days before any subsurface work and conduct a utility clearance using a private utility locator to identify subsurface utilities and other potential obstructions. Proposed.investigation locations may be adjusted based upon the USA and private utility clearance. The RWQCB will be notified of any changes prior to the commencement of field work. Task 1: Perform CPT/Grab-Groundwater Investigation to Delineate the Extent of Toluene Ln Groundwater both Laterally and Vertically Task 1 consists of characterizing the soil behavior type by CPT and depth-discrete groundwater sampling at the four locations shown in Figure 26. The field procedures associated with this task are similar to those described in Section 7.2 of the CPT-13 Area Investigation Report and Work Plan?and are presented below. Cone Penetrometer Testing(CPT) Two CPT borings will be advanced off-site and to the north of the CPT-13 area and Church Street. The purpose of the CPT investigation is to (1) provide detailed information of the geology in the apparent downgradient direction of the CPT-13 area, and (2) to identify appropriate depth intervals for sampling groundwater for analysis of toluene. Gregg Drilling & Testing, Inc. of Martinez, California, (Gregg) will provide the equipment and personnel to perform the CPT work. All work will be completed under supervision of Geosyntec personnel. The CPT probe will be advanced to a target depth of 1.30 feet bgs to identify the depth of the water bearing zones including the deep aquifer underlying the Site. The following parameters will be measured or detected at 5.cm (0.16 ft) depth-intervals at each CPT location: • Tip resistance (Qt); • Sleeve friction (Fs); and a Dynamic pore pressure (Ut). G Note that two grab groundwater sample locations are tentative pending permission to obstruct the driveways of private residences. 7 Geosyntec,2013.CPT-13 Area Investigation Report and Work Plan, Dopaco,Inc.Area, 800 West Church Street, Stockton, California, 95203, GeoTracker Global ID T10000003890.30 May. Offsite Characterization Workplan engineers I scientists I innovators i I