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(\TIATC • A S S O C I A T E S I N C In December 1999 ATC personnel supervised the advancement of soil boirngs MW2, MW3, and MW4 at the site to depths of approximately 65 feet bgs to evaluate groundwater for the presence of petroleum hydrocarbons and determine the gradient direction and magnitude The borings were completed as monitoring wells Analytical data indicated that soil samples from boring MW2 contained detectable concentrations of petroleum hydrocarbons Petroleum hydrocarbons were also detected in the groundwater from well MW2 Well MW3 contained very low concentrations of only a few constituents and well MW4 was nondetect Field activities and analytical results were detailed in ATC's Summary Report of Additional Subsurface Investigation, dated February 24, 2000 GROUNDWATER ELEVATION Water level measurements were collected from wells MW 1 through MW4 on June 15, 2001 Water level elevations ranged from a high of—23 32 to a low of—23 38 representing an average decrease in water table elevation of 0 63 feet since March 2001 The water level data were used to develop the groundwater elevation contour map (Figure 3) Assuming that horizontal isotropic conditions prevail, groundwater in the uppermost aquifer beneath the site flowed generally towards the south with a slight depression located at the approximate former tank location The average hydraulic gradient on June 15, 2001 was calculated to be 0 001 ft/ft or approximately 5 ft/mile A summary of groundwater monitoring data is presented in Table 1 • SAMPLING ACTIVITIES On June 15, 2001, groundwater samples were collected by ATC personnel from monitoring wells MW 1 through MW4 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 temperature were measured in 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 1 The groundwater samples collected from the wells were submitted to State certified Argon Laboratories (ELAP Cert No 2359) for chemical analysis of total petroleum hydrocarbons as gasoline (TPHg), total petroleum hydrocarbons as diesel (TPHd), and total petroleum hydrocarbons as kerosene (TPHk) utilizing EPA method 8015 modified, benzene toluene, ethylbenzene, and xylenes (BTEX) utilizing EPA method 8020, and oxygenate fuel additives including methyl tert butyl ether (MTBE) utilizing EPA method 8260 ANALYTICAL RESULTS - - The groundwater samples collected from wells MW 1 and MW2 contained detectable concentrations of TPHg at concentrations of 980 µg/L and 400 gg/L, respectively Benzene was detected at wells MW 1 and MW2 at concentrations of 27 pg/L and 17 gg/L, respectively w Iwordpro15257712QA 2001 doe 2