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L <br /> Data from nearby studies indicate that the current depth to groundwater in the vicinity ranges <br /> from about 5 to 10 feet bgs (SPGC, 1998, and EMCON, 1998). Seasonal fluctuations in the <br /> water table appear to range from about 3 to 5 feet, with some as much as 6 to 9 feet. <br /> Historically, water levels in this area have risen as much as 8 feet since 1994. Tank removal <br /> inspection records for Port sites (dating back to 1987) indicate that no groundwater was <br /> • encountered during excavation or soil resampling to a depth of as much as 16 feet bgs. <br /> `, Groundwater flow directions in the vicinity of the site appear to be variable, ranging from west <br /> northwest to east southeast. Flow direction changes may be due to tidal influences produced <br /> by the deep water channel to the north and the San Joaquin River to the west and southwest <br /> of the Port area. <br /> 3.0 PROPOSED SCOPE OF WORK <br /> k. The proposed scope of work includes advancing three borings using the Geoprobe direct-push <br /> method, and collecting soil and/or groundwater samples for analysis of PHCs. Field, <br /> analytical, and historical data will be evaluated to determine the lateral and vertical extent of <br /> 6' PHC impact in the soils and groundwater beneath the site. A Site Investigation and Evaluation <br /> Report will be prepared including documentation of field work and a summary of findings and <br /> recommendations. <br /> *- 3.1 FIELD INVESTIGATION <br /> L The following sections describe the approach and methodology for the field investigation. <br /> Prior to initiating any field work, an application for "Permit to Construct Monitoring Wells <br /> and/or Soil Borings for the Purpose of Subsurface Investigation," will be submitted to and <br /> approval obtained from the PHS/EHD. <br /> 3.1.1 Approach <br /> Water levels in the vicinity of the site have risen substantially since the tank was removed. <br /> � It is anticipated that there will be only a small interval, if any, of unsaturated soils (vadose <br /> zone) between the bottom of the former excavation and the water table. If that proves true, <br /> then the subsurface investigation will focus primarily on evaluation of the lateral extent of <br /> i. PHCs in groundwater. <br /> In order to reduce the potential for contamination of groundwater due to penetration through <br /> contaminated soils and translocation of contamination by drill tools, an initial boring <br /> 3 981171S4USTINV.WPN <br /> IFR, BOYAHAN & ROSS, INC. <br /> Environmental Scientists & Engineers <br />