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(tATC A S S O C I A T E S I N C %ow/ top of the well screen. Analytical results indicated the presence of petroleum hydrocarbons. Results are summarized in AGE'S Quarterly Report-July 1998. In March 1999, ATC supervised the advancement of two soil borings at the site and the borings were subsequently completed as groundwater monitoring wells MW2 and MW3. Analytical data indicated that soil samples collected from wells MW2 and MW3 contained no detectable concentrations of petroleum hydrocarbons. The groundwater sample collected from well MW2 contained trace amounts of toluene. The March 1999 subsurface investigation results are detailed in ATC's Summary Report of Groundwater Monitoring Well Installations, dated June 3, 1999. SAMPLING ACTIVITIES On September 3, 1999, groundwater samples were collected by ATC Associates personnel from monitoring wells MW1 through MW3. The locations of the monitoring 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 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 Sequoia Analytical (ELAP Cert. No. 1210) for chemical analysis of total petroleum hydrocarbons as gasoline (TPHg), utilizing EPA methods 8015 modified, benzene, toluene, ethylbenzene, and xylenes (BTEX) utilizing EPA methods 8020, and oxygenate fuel additives utilizing EPA method 8260. Groundwater well purge and sample logs are contained in Attachment 1. ANALYTICAL RESULTS The groundwater samples collected from wells MW2 and MW3 contained no detectable concentrations of TPHg, BTEX, or oxygenate fuel additives. The groundwater sample collected from well MW1 contained benzene, xylenes, and methyl tertiary butyl ether (MTBE) at concentrations of 3.02 parts per billion (ppb), 4.10 ppb, and 66.3 ppb, respectively. Analytical results of groundwater samples are summarized in Table 2. Laboratory data sheets and chain-of- custody documentation are contained in Attachment 2. GROUNDWATER FLOW DIRECTION Water level measurements were collected from wells MW1 through MW3 on September 3, 1999. Water levels ranged from 35.81 to 36.31 feet below the top of well casing elevations, representing an average decrease in the water table elevation of approximately 1.74 feet since June 1999. 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 towards the east. The average hydraulic gradient on September 3, w:\62574\62574.05\quartly\3gr-I999.doc 2