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ATC Associates Inc 1117 Lone Palm Avenue, Suite B mow Modesto, California 95351 (:VAT%• 209-579-2221 AS s a C A r C- s INC fax 209-579-2225 activities and analytical results are detailed in ATC's Summary Report of Additional Subsurface Investigation, dated January 8, 1999 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 Invertrgation, dated February 24, 2000 In December 2001, soil-boring VEW 1 was advanced to approximately 35 feet bgs, and borings VEW2 and VEW3 were advanced to approximately 45 feet bgs Borings MW5, MW6, and MW7 were advanced to approximately 65 feet bgs Soil borings VEW I, VEW2, and VEW3 were completed as 2-inch diameter vapor extraction wells and soil borings MW5, 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, at a vacuum of 11 5 inches of water Approximately 2 64 pounds of total petroleum hydrocarbons quantified as gasoline (TPHg), 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 InvestrgationlTeasibility Study, dated November 19, 2002 SAMPLING ACTIVITIES On October 6, 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 was measured in the monitoring wells and pH, electrical conductivity, and temperature were recorded and turbidity was visually observed for groundwater purged from each monitoring well and recorded A minimum of three well casing volumes was purged from each well prior to sampling The wells were allowed to recover and a sample was collected from each well using a disposable bailer Groundwater well purge and sample logs are contained in Attachment I = The groundwater samples collected from the wells were submitted to State certified Argon Laboratories Environmental Laboratory Accreditation Program (ELAP) Certification No 2359, for chemical analyses of TPHg, total petroleum hydrocarbons quantified as diesel (TPHd), and total petroleum hydrocarbons quantified as kerosene (TPHk) utilizing EPA Method 8015B, S 1625774QR-2004 doc 2