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r h DISCO PROPERTY,STOCKTON,CALIFORNIA i • Updating the site specific health and safety plan per OSHA requirements. • Obtaining the necessary permits for drilling (i.e.,PHS drilling and well permits). • Reviewing the utility lines in the area to verify safe drilling locations. I Subtask 2 Field Activities Under this subtask,three borings will be drilled and sampled and two of these borings will be converted to monitoring wells.Boring SB97-1 will be located at the north end of the former pump island. Borings SB97-2 (MW-11) and SB97-3 (MW-11D)will be placed near the southeast comer of the former pump island near known high concentrations of the j' constituents of concern (Figure 1). Borings SB97-1 and SB97-2 will be advanced to a depth of approximately 10 feet below the groundwater table. Each of these borings will be continuously logged and samples will be collected for chemical analyses. Based on the field screening and analytical results,the boring with the highest level of contamination will be converted into a shallow monitoring well (MW-11). After the installation of MW-11, a deep boring (SB97-3)will be drilled in the vicinity of MW-11 to evaluate the vertical extent of soil and groundwater contamination. After the total depth of groundwater contamination has ! been determined,boring SB97-3 will be converted into a deep monitoring well(MW-11D). Each boring will be: • cored continuously to its intended total depth; • screened with a photoionization detector (PID), • sampled and field tested for Total Petroleum Hydrocarbons (TPH) as gasoline using a field test kit such as Petroflag, and • sampled and analyzed by a state-certified laboratory for analysis of TPH as gasoline and benzene,toluene,ethyl benzene, and xylenes (BTEX). Soil samples from distinct lithological units in the deep boring will be collected and submitted to a geotechnical laboratory for the analysis of falling head permeability using ASTM method 5084, dry bulk density using ASA 930.2,moisture content ASTM D2216,and total organic carbon using ASTM D2974. Approximately 3.to 4 soil samples per boring will be submitted to the certified laboratory for testing(Table 1). The testing will be performed to verify the field results and help calibrate the field screening techniques. As discussed above,one shallow (MW-11) and one deep (MW-11D) monitoring well will be installed in the borings that contain the highest levels on petroleum contamination. The exact location and screen interval of these monitoring wells will be determined with j concurrence from Ron Rowe of PHS. The well screen for MW-11 will be placed across the top of the static water level.This well will be designed to afford the opportunity to monitor the top of the uppermost portion of the aquifer and allow for approximately 13 feet of water level rise. The base of the screen will be at 65 feet below ground surface which coincides with the top of the screened interval of the next shallowest,existing monitoring point(NP-2) in the area of the former pump 3