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i Mr Nuel Henderson Page 2 of 4 Groundwater flowed in a northeasterly direction, and the average gradient across the site was approximately 0 0025 feet per foot A potentiometric surface map generated using the groundwater elevation data from all site momtormg wells is shown on Figure 2 Groundwater monitoring data are summarized in Table 1 Monitoring data sheets and well construction details are included in Attachment A On November 13 and 14, 2002, a Ground Zero technician collected groundwater samples from monitoring wells MW3 through MW6, MW8, MW10, MWI I and MW14 and from vapor wells VW3, VW4 and VW6 A minimum of three well casing volumes was purged from each well prior to sampling During the purging process, physical parameters (pH, electrical conductivity, and temperature) were monitored Subsequent to parameter stabilization, and a minimum of 80% recovery of initial depth to groundwater measurements, groundwater samples were collected and placed in an iced cooler for transport to Argon Laboratories (FLAP#2359) under chain of custody protocol Analysis consisted of gasoline oxygenates, EDB and 1,2-DCA by EPA Method 8260, TPHg by EPA Method 8015 modified and BTEX by EPA Method 8020 Purge water was transferred into labeled 55-gallon drums approved by the Department of Transportation (DOT), which are stored onsite within a secured area Purge logs are included in Attachment A GROUNDWATER ANALYTICAL RESULTS Groundwater Monitoring Wells TPHg was detected in all sampled wells except MW6, MW10 and MWI I Benzene was detected in all wells sampled except for MW6 and MW10 Dissolved TPHg and BTEX in the monitoring wells were within historical ranges, and appear to be stable to decreasing TPHg and BTEX concentration data are summarized in Table 2 Attachment B contains laboratory reports and chain of custody documentation Graphs depicting TPHg and benzene concentrations over time are included in Attachment C MTBE was the only gasoline oxygenate detected in the sampled wells, and continues to below laboratory method detection limits in wells MW5, MW6 and MW8 MTBE was detected in wells MW3 (5,300 parts per billion - ppb), MW4 (4,700 ppb), MW 11 (23 ppb) and MW 14 (210,000 ppb), which are located along the southern portion of the site (Figure 2) MTBE was also reported in downgradient well MW10 (north side of Market Street) at concentration of 4 2 ppb Concentrations of dissolved MTBE detected in wells MW3 and MW4 had decreases of up to 4 5x since last sampled, while the levels reported m MWl I and MW14 are the highest to date These wells are clearly affected by offsite MTBE releases EDB was not detected in any monitoring wells sampled, however, 1,2-DCA was detected for the first time in wells MW5 and MW6 at concentrations of 66 ppb and 6 2 ppb, respectively 1,2-DCA was also present at low levels in monitoring wells MW10 and MW11 Analytical results for gasoline oxygenates, EDB and 1,2-DCA are summarized in Table 3 Attachment B contains laboratory reports and chain of custody documentation i 11GZA FSISYS011Data\GROUNDZEIROEK\QMR1200214gm2042 doc