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Geo(cgicafTechinics Inc, *%I N.O� Page 2 <br /> City of Escalon <br /> Cost Pre-Approval <br /> 1 Project 750.2 <br /> April 23, 1999 <br /> 1 Previous work at this site includes two limited soil borings, soil sample analysis, and the removal <br /> of the USTs and pump islands. During removal activities, soil samples were collected which <br /> showed the presence of BTEX, TPH-G and MTBE. <br /> i On February 12 & 23, 1999 Geological Technics Inc. (GTI) drilled six boreholes, collected soil <br /> and groundwater samples (including one groundwater sample from each borehole via <br /> hydropunch methods) and tested these samples for petroleum hydrocarbons. <br /> The probable source for the majority of this contamination was either the dispenser island or <br /> piping near HP-1. <br /> It appears that the contamination primarily moved vertically in the soil with veryIittle later <br /> al <br /> spread. Supportive evidence is the elevated concentrations in HP contracted to te non-detects <br /> in boreholes HP-2, HP-3, HP-4 and HP-6, which are only a short distance from HP-1. HP-5, <br /> only 30 feet from HP-1, contained low levels of BTEX and moderate to low levels of MTBE and <br /> TBA. <br /> Once the contaminant reached groundwater, it spread out laterally, impacting the groundwater at <br /> HP-1, HP-2, HP-4 & HP-5. From review of theroundwater analytical ytical data there does not <br /> appear to be a preferential spread of the groundwater plume in one direction as a result of a <br /> I groundwater gradient direction. With HP-3 & 6 non-detect, it appears that the groundwater <br /> I plume may not be very large. <br /> Proposed Direction of Project <br /> There are four primary components of this project. Each one is outlined below and issues with <br /> each component are discussed. <br /> 1. Perform Project Preparation Work <br /> 0 Project coordination & organization <br /> • Prepare a Work Plan& Site Map for the work outlined below <br /> • Obtain drilling, SJVUAPCD permits, Encroachment Permit <br /> 2. Perform Soil & Groundwater Investigation <br /> 9 Drill & Install 4 Monitoring Wells (MWs) <br /> • 3-water table wells (75' deep) <br /> 1-deeper aquifer well (105' deep) <br /> • Test soil samples collected during drilling of boreholes for TPH-G, BTEX, Oxygenated <br /> Fuel Compounds (OFC) <br /> • Prepare a Site Characterization Report of well installation and testing <br /> 3. Perforin Groundwater Monitoring for 1 Year <br /> • Purge & Sample 4 Monitoring Wells each quarter <br /> • Test samples for TPH-G, BTEX, OFC <br /> • Prepare 4 Groundwater Monitoring Reports <br /> 4. Perform a Feasibility Study for Soil Vapor Extraction <br /> • Drill& Install 4 Vapor Extraction Wells <br /> ■ 2-well 55' deep <br /> ■ 2-well 27' deep <br /> • Trench and connect VEWs & MWs via Piping to area of future treatment compound <br /> ■ 1 SO' of trenching <br /> 0 600' of piping (a pipe to each well) <br />