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Geol kat rechnicsInc. Page 2 Groundwater Monitoring Report Project No.750.2 April 1,2005 Laboratory analysis of the groundwater samples, collected during the February 16, 2005, groundwater-monitoring event, indicate all the monitoring wells are non-detect above laboratory reporting limits for all analyzed constituents. The soil vapor extraction system was reactivated in September 2004 and has been in operation since September 24, 2004. The system was off for approximately 16 days for modifications. As of March 30, 2005, the system has removed an estimated cumulative total of 336 gallons or 637 pounds of TPH-G. The system is scheduled to be shut down on April 15, 2005. 1.0 INTRODUCTION The COE site is located at 1305 Escalon Ave, Escalon, California. Figure 1 is a vicinity map and Figure 2 is a site map. This property was previously an Arco Gas and Mini Mart. r Previous work at this site includes two limited soil borings, soil sample analysis, and the removal of the USTs and pump islands. During removal activities, soil samples were collected which showed the presence of BTEX,TPH-G and MTBE. On February 12 & 23, 1999 Geological Technics Inc. (GTI) drilled six boreholes, collected soil and groundwater samples (including one groundwater sample from each borehole via hydropunch methods) and tested these samples for petroleum hydrocarbons. Analytical results show the presence of BTEX, TPH-G and oxygenated fuel compounds in the soil and groundwater. From April of 1999 through January of 2000 three groundwater monitoring wells and four vapor extraction wells were installed on the site. Soil samples collected during the drilling of these wells show low to moderate levels of BTEX, TPH-G, MTBE and TBA in MW-1. Low levels of MTBE were detected in MW-2. Soil samples collected from VEW-1 showed low levels of total xylenes and MTBE. On June 12, 2000, GTI and Del-Tech Geotechnical Support Services (Del-Tech)performed a vapor extraction pilot test at the site. Laboratory and field test results indicate the site is conducive to remediation by vapor extraction. On June 12, 2000, Ms. Lori Duncan of SJCEHD requested in writing that a work plan be prepared to define the lateral and vertical extent of the groundwater plume at the site. On r„ June 29, 2000, GTI prepared a work plan proposing the installation of two water table monitoring wells and one deep, discretely screened monitoring well. Ms Duncan approved the work plan on July 7, 2000. The work was performed during the week of October 16, 2000. V V