WORK PLANS_CASE 4 - Laserfiche WebLink

Home Browse Search

inspection records for Port sites (dating back to 1987) indicate that no groundwater was encountered during excavation or soil resampling to a depth of as much as 16 feet bgs. Groundwater flow directions in the vicinity of the site appear to be variable, ranging from west 60 northwest to east southeast. Flow direction changes may be due to tidal influences produced by the deep water channel to the north and the San Joaquin River to the west and southwest of the Port area. 3.0 PROPOSED SCOPE OF WORK The proposed scope of work includes advancing three borings using the Geoprobe direct-push method, and collecting soil and/or groundwater samples for analysis of PHCs. Field, analytical, and historical data will be evaluated to determine the lateral and vertical extent of 69 PHC impact in the soils and groundwater beneath the site. A Site Investigation and Evaluation Report will be prepared including documentation of field work and a summary of findings and recommendations. 60 r`. 3.1 FIELD INVESTIGATION The following sections describe the approach and methodology for the field investigation. v Prior to initiating any field work, an application for "Permit to Construct Monitoring Wells and/or Soil Borings for the Purpose of Subsurface Investigation," will be submitted to and approval obtained from the PHS/EHD. LO 3.1.1 Approach Due to the unusually wet winters over the past few years, water levels in the vicinity of the site have risen substantially since the tank was removed. It is anticipated that there will be only a small interval, if any, of unsaturated soils (vadose zone) between the bottom elevation of the former excavation and the water table. If that proves true, then the subsurface investigation will focus primarily on evaluation of the lateral extent of PHCs in groundwater. In order to reduce the potential for contamination of groundwater due to penetration through v contaminated soils and translocation of contamination by drill tools, an initial boring (Bl-1, Figure 2) will be advanced about 10 feet away from the location of the former tank. In the initial boring, continuous core samples will be collected from the approximate depth of the �. bottom elevation of the former tank to about 10 feet below the water table. These soil samples will allow characterization of the subsurface lithology and depth to groundwater at the tank site, and will provide target locations for collection of soil and groundwater samples in the 60 3 98tMstum1mv.WN 1. BOYAHAN & ROSS, INC. a JAW Environmental Scientists & Engineers Ls