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, ATC Associates Inc �VJ 1117 Lone Palm Avenue, Suite B y Modesto, California 95351 . 209-579-2221 ASSOCIATES I N c fax 209-579-2225 activities and analytical results are detailed in ATC's Summary Report of Additional Subsurface Investigation, dated January 8, I999 In December 1999, ATC personnel supervised the advancement of soil borings MW2, MW3, and MW4 at the site to depths of approximately 65 feet bgs to evaluate groundwater for the presence of petroleum hydrocarbons and to determine the gradient direction and magnitude The borings were completed as monitoring wells Analytical data indicated that soil samples collected from boring MW2 contained detectable concentrations of petroleum hydrocarbons Petroleum hydrocarbons were also detected in a groundwater sample collected from well MW2 A groundwater sample collected from MW3 contained very low concentrations of only a few of the requested analytes Petroleum hydrocarbons were not detected in the groundwater sample collected from MW4 Field activities and analytical results are detailed in ATC's Summary Report of Additional Subsurface Investigation, dated February 24, 2000 In December 2001, soil-boring VEW1 was advanced to approximately 35 feet bgs, and borings VEW2 and VEW3 were advanced to approximately 45 feet bgs Borings MWS, MW6, and MW7 were advanced to approximately 65 feet bgs Soil borings VEW1, VEW2, and VEW3 were completed as 2-inch diameter vapor extraction wells and soil borings MWS, MW6, and MW7 were completed as 2-inch diameter groundwater monitoring wells Boring CPT1 was advanced to approximately 100 feet bgs utilizing a truck-mounted cone penetration test (CPT) rig A soil vapor extraction pilot test was conducted which yielded a radius of influence (ROI) of approximately 30 feet Approximately 2 64 pounds of total petroleum hydrocarbons quantified as gasoline (TPHS), benzene, toluene, ethylbenzene, and xylenes (BTEX) were removed during the vapor extraction pilot test Soil vapor extraction appeared to be a viable method for remediating TPHg and BTEX impacted soil at the site Field activities and analytical results are detailed in ATC's Remedial Investigation/Feasibility Study, dated November 19, 2002 GROUNDWATER ELEVATION Water level measurements were collected from wells MW I through MW7 on April 7, 2004 Water elevations ranged from a high of —30 93 to a low of —31 00 representing an average increase in water table elevation of 1 35 feet since January 13, 2004 The water level data were used to develop a groundwater elevation contour map (Figure 3) Review of the groundwater elevation contour map (Figure 3) indicates that the hydraulic gradient beneath the site on April 7, 2004 was relatively flat and the gradient direction varied across the site A summary of groundwater monitoring data is presented in Table I SAMPLING ACTIVITIES On April 7, 2004, groundwater samples were collected by ATC personnel from monitoring wells MW1 through MW7 The locations of the monitoring wells are shown on Figure 2 Prior to collection of the groundwater samples, the depth to water, pH, electrical conductivity, and S 16257712QR-2004 doc