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I Mr Nuel Henderson Page 2 of 4 . A potentiometric surface map generated using the groundwater elevation data from all site monitoring 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 May 28, 29 and 30, 2003, a Ground Zero technician collected groundwater samples from monitoring wells MW3 through MW6, MW8, MW10, MW11, MW13B through MW16B and from vapor wells VW4 and VW6 Samples were not collected from vapor wells VW2 and VW5 as they were dry (Table 1) 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 (ELAP #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 8021B Purge water was transferred into labeled 55-gallon drums approved by the Department of Transportation (DOT) The waste is 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, MW11, MW15A and MW15C Benzene was detected in all wells sampled except for MW6, MW I0, MW 11, MW15A and MW 15B Dissolved TPHg and BTEX levels in the remaining 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 continues to below laboratory method detection limits in wells MW5, MW6, MW8, MW 13B and MW15C MTBE was detected in wells MW3 (28,000 parts per billion - ppb), MW4 (10,000 ppb), MW11 (26 ppb) and MW14 (100,000 ppb), which are located along the southern portion of the site (Figure 2) In downgradient wells MW10 (north side of Market Street), MW15A and MW15B (Eugema and Market) MTBE was reported at concentrations of 2 5 ppb, 33 ppb and 190 ppb, respectively Elevated levels of MTBE were also found in cross-gradient wells MW 16A and MW 16B These wells are clearly affected by offsite releases DIPE was at non-detectable levels in all sampled wells except for well MW 11 (2 9 ppb) EDB was not detected in any of the monitoring wells sampled 1,2-DCA was detected in wells MW10, MWl I, MW 1313, MW 15A and MW 15B Concentrations of 1,2-DCA ranged from 4 7 ppb (MW 15A) to 940 ppb (MW 13B) 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 G 1GROUNDZEIROEKIQMR1200312gm2003 doc