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DISCO PROPERTY,STOCKTON,CALIFORNIA <br /> island.Therefore,if water elevation decreases below the base of MW-11, other existing <br /> wells will be able to resume monitoring the top of the uppermost saturated interval. <br /> Due to the anticipated depth of MW-11D (i.e.,greater than 100 feet below ground surface), <br /> this boring and well will be installed differently than the other borings. MW-11D will be <br /> installed with the following general protocols: <br /> • Drilling shall be conducted to prevent cross contamination of the impacted <br /> groundwater with deeper water bearing zones. <br /> • Drilling will continue until there are no significant concentrations of petroleum <br /> constituents in the soil or groundwater. <br /> • Grab groundwater sampling using Hydropunch or equivalent techniques. <br /> • Sampling of grab groundwater samples will be collected in permeable water bearing <br /> intervals below 90 feet bgs and submitted for 24-hour analysis of TPH-gasoline,BTEX <br /> and MTBE. <br /> • Converting the boring to monitoring well MW-11D will be conducted after the 24-hour <br /> analytical results indicate that the depth is below the contaminated soil and <br /> groundwater and concurrence has been obtained from Ron Rowe of PHS. <br /> After both MW-11 and MW-11D have been completed, these wells will be developed and <br /> sampled according to standard protocols previously used at the Disco property. <br /> Subtask 3 Laboratory Analysis <br /> Selected soil and grab groundwater samples from each of the borings in Activity I will be <br /> submitted to a state certified laboratory.The samples will be analyzed for gasoline <br /> constituents and geotechnical parameters as specified in Table 1. The soil samples will be <br /> analyzed using a standard 10-day time period. The grab groundwater samples will be <br /> analyzed in a 24-hour time period. <br /> Subtask 4 Reporting <br /> Under this Subtask,a letter report will be issued summarizing the findings of Activity I. The <br /> report will include the boring logs,tabulate the field and laboratory chemistry findings, <br /> and recommend refinements to the plans for Activities II and III. <br /> Activity II - Groundwater Investigation Downgradient of Former Disco Tanks <br /> This activity is designed to characterize potential offsite migration that may have occurred <br /> as a result of shifting groundwater flow directions. Coincident with rising static water <br /> elevations in the uppermost aquifer is a shift of groundwater flow from primarily north in <br /> 1991 to south in 1995, and currently southeast using the most recent water level <br /> measurements. Based on discussions with PHS staff, there is a need to characterize the <br /> extent of petroleum hydrocarbons in groundwater in the new downgradient direction. <br /> 4 <br />