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April 18,2019 Former Shell Service Station 2085 East Mariposa Road, Stockton Page 2 of 5 repair facility and single-family residences are located southeast across East 80' Street (which becomes Farmington Road north of the intersection with East Mariposa Road). PROPOSED SCOPE OF WORK In order to delineate the lateral and vertical extents of impacted soil and to provide an initial groundwater assessment, WPI has proposed to conduct soil and hydropunch groundwater sampling in the vicinity of boring B4 (Figure 2). Boring B4 is located within the former tank zone and samples at the maximum depth of 20 feet contained total petroleum hydrocarbons as gasoline (TPHg) at 5,260 mg/kg and diesel (TPHd) at 4,660 mg/kg. Three cone penetrometer test (CPT) borings will be advanced to a depth of 50 feet and soil and groundwater samples will be collected for analysis. Based on the Fourth Quarter 2018 groundwater gauging data collected from the former USA Service Station No. 110 (Case # 390090), the depth to groundwater in the closest well (MW-1), located approximately 240 feet northeast of the proposed sampling locations,was 42 feet; therefore, the sampling depth for ,groundwate5 in the proposed borings is estimated to be between approximately45 and 50 fee r' Pre-Field`Activities 'J Pre-field activities will include the following: • Creating a site-specific health and safety plan; • Scheduling subcontractors; • Obtaining necessary drilling permits; and • Notifying Underground Service Alert at least one week prior to commencement of work to perform an underground utility clearance for the planned drilling location. Field Activities Prior to any sampling activities, a utility line survey will be performed to locate all underground utility lines in the vicinity of the proposed locations. The proposed locations will be air knifed to a depth of five feet and to a width three inches larger that the width of the drill rods. Three CPT borings will be advanced and soil and groundwater samples collected from each boring by a state-licensed C-57 contractor. Details of the sampling procedures are in the table below. Number of Depth of Drilling Sample Sample Method Sample Analysis Borings Boring Method Interval 3 Estimated: CPT Rig Soil: Soil: Soil and Groundwater: 50 feet Five-foot Piston Sampler Total petroleum hydrocarbons as intervals diesel(TPHd)and gasoline between 5 Groundwater: (TPHg)using EPA Method feet and the Hydropunch 8015M;and for BTEX/fuel total depth Sampler oxygenates using EPA Method 8260B 8281 Commonwealth Ave. Buena Park,CA 90621 Phone(7l4)826-0352 24-hour(800)883-0352 Fax(714)523-7880