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CVATC . A S S b C 1 A T E S l H C on September 28, 1998 the well was developed and sampled Analytical data indicated that soil and groundwater samples contained detectable concentrations of petroleum hydrocarbons Field activities and analytical results were 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 determine the gradient direction and magnitude The borings were completed as groundwater 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 December 15, 2000 Water levels ranged from 48 51 to 48 81 feet below the tops of the well casing elevations • representing an average decrease in the water table elevation of approximately 0 65 feet since September 2000 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 southwest with a northwest component The average hydraulic gradient on December 15, 2000 was calculated to be 0 002 ft/ft or approximately 11 ft/mile A summary of groundwater monitoring data is presented in Table 1 SAMPLING ACTIVITIES On December 15, 2000, groundwater samples were collected by ATC personnel from monitoring wells MW1 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 dedicated 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 Sequoia -- Analytical (FLAP Cert No 1624) for chemical analysis of total petroleum hydrocarbons as gasoline (TPHg), total petroleum hydrocarbons as diesel (TPHd), total petroleum hydrocarbons as kerosene (TPHk), benzene, toluene, ethylbenzene, and xylenes (BTEX) utilizing EPA 8015 and 8020 methodologies, and oxygenate fuel additives including methyl tertiary butyl ether (MTBE) utilizing EPA 8260 methodology w I625771reponsl4"-2000 doe 2