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1 <br /> Y <br /> The groundwater depth and flow direction data measured at the Knowles Roek site <br />' correspond with those measured at the Wells Fargo site. The regional groundwater flow <br /> direction in the area is toward the northeast which corresponds with the flow directions <br /> measured at the Wells Fargo and Knowles Roek sites. The groundwater flow direction at <br /> the Top Filling Station site differs from the measured flow direction at the Wells Fargo and <br /> Knowles Roek sites by almost 90 degrees. The variations in groundwater flow direction <br /> may be from seasonal fluctuations of groundwater elevation and/or anomalous <br /> measurements <br />' MTBE has not been detected beneath the Wells Fargo property. The monitoring wells at <br /> the Top site with high TPH-g and benzene concentrations also have elevated levels of <br /> MTBE. Since the use of MTBE in fuels is relatively recent (widespread use of MTBE <br /> began in the 1980's) it appears that the Top Filling Station contaminant plume is also <br /> relatively recent and not due to previous activities at 49 South Wilson Way. <br /> The concentrations of TPH-g and BTEX beneath the Wells Fargo Property are much lower <br /> than the concentrations at the Top or Roek site. <br />' OBJECTIVE AND SCOPE OF WORK <br /> The first objective of this investigation was to explore for the former location of the former <br /> USTs beneath the subject property, using geophysical methods. <br /> IThe second objective was to gather additional information regarding the soil and <br /> groundwater beneath the site. In order to achieve this objective, Building Analytics <br /> proposed to advance three soil borings to groundwater, and two shallow soil borings <br /> within the bank building. <br /> To accomplish the objectives,Building Analytics performed the following tasks: <br /> a. Marked the boring locations and called Underground Service Alert(USA) to perform <br /> utility clearance. Subsequently, a private utility locating company cleared the proposed <br /> boring location for underground utilities; <br /> b. Contracted with a State of California Registered Geophysicist to perform a subsurface <br /> geophysical survey utilizing shallow ground penetrating radar (GPR), electro-magnetic <br /> profiling(EM)and magnetometer(Mag)technologies; <br /> c. Contacted SJCEHD and applied for Well Construction Permits; <br /> d. Advanced three soil borings to a maximum depth of 70 feet bgs and converted the <br /> borings into groundwater monitoring wells MW-1, MW-2 and MW-3; <br /> e. Advanced two soil probes within the building to 15 and 25 feet bgs; <br /> f. Collected soil samples at five-foot bgs intervals and submitted selected samples for <br />' analysis of TPH and BTEX in accordance with EPA Methods 8015M (Simulated <br /> Distillation),and 8020,respectively; <br /> g. Surveyed the monitoring well elevations and locations; <br /> h. Collected one groundwater sample from each monitoring well along with a blind <br /> duplicate, and submitted the sample for analysis of TPH, BTEX, MTBE and volatile <br /> 4 197046a - Stockton <br />