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C_ Vvi A S S O C I A T E S I N C and groundwater are impacted by petroleum hydrocarbons Site activities were summarized In ATC's Summary Report of Subsurface Investigation, dated January 15, 1999 In December 2000, ATC personnel supervised the advancement of one cone penetrometer (CPT) boring to 140 feet bgs Also In December 2000 ATC personnel supervised the advancement of four soil borings to 80 feet bgs and one soil boring to 100 feet bgs The soil borings were converted into groundwater monitoring wells Analytical results of soil samples and groundwater samples indicated that soil and groundwater are impacted by petroleum hydrocarbons Site activities were summarized in ATC's Summary Report of Additional Subsurface Investigation, dated March 6, 2001 SAMPLING ACTIVITIES On April 4, 2002, ATC personnel collected groundwater samples from monitoring wells MW1, MW3 through MW 10, and the on-site groundwater supply well DW A groundwater sample was not collected from well MW2 because of the presence of floating free product in the well The locations of the wells are shown on Figure 2 Prior to collection of groundwater samples, the depth to water, pH, electrical conductivity, and temperature were measured In the monitoring wells and recorded A minimum of three well casing volumes were purged from each monitoring well prior to sampling The wells were allowed to recover and samples were collected from each well using dedicated disposable bailers The groundwater samples collected from each well were submitted to State-certified Argon Laboratories Inc (ELAP Cert No 2359) in Ceres, California for chemical analysis of total petroleum hydrocarbons as gasoline (TPHg) utilizing EPA method 8015 modified, benzene, toluene, ethylbenzene, and xylenes (BTEX) utilizing EPA method 8020, and methyl tertiary butyl ether (MTBE), ethyl tertiary butyl ether (ETBE) di-isopropyl ether (DIPE), tertiary amyl ether (TAME), tertiary butyl ether(TBA), 1,2-dlchloroethane (1,2-DCA), and 1,2-dlbromoethane (EDB) utilizing EPA method 8260 Groundwater well purge and sample logs are contained In Attachment 1 ANALYTICAL RESULTS Groundwater samples collected from wells MW I, MW3, MW6, and MW8 contained the highest . concentrations of TPHg and BTEX Concentrations of TPHg ranged from 210,000 parts per billion (ppb) in well MW6 to 7,600 ppb In well MW8 Concentrations of benzene ranged from 11,000 ppb in well MW1 to 120 ppb In well MW8 Groundwater samples collected from wells MW4, MW7, and MW10 contained detectable concentrations of TPHg and BTEX constituents The groundwater sample collected from wells MW5 and MW9 contained no detectable concentrations of TPHg or BTEX Groundwater samples collected from wells MWI. and MW3 • through MW10 contained no detectable concentrations of oxygenate fuel additives although l many of the reporting limits were elevated due to dilution The groundwater sample collected from on-site supply well DW contained detectable concentrations of TPHg and BTEX, but w\I63931quartlyllgr-2002 doc 2