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i Mr Nuel Henderson Page 2 of 4 The potentiometric surface was above the top of the screened intervals in monitoring wells MW4 through MW13B, MW 15B, MW 15C, MW 16B and vapor wells VW 1 and VW4 Vapor wells VW2 and VW5 were dry Groundwater flowed in an east-northeasterly direction The average gradient across the site was approximately 0 002 feet per foot A potentiometric surface map generated using the groundwater elevation data from all site groundwater 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 August 27 and 28, 2003, a Ground Zero technician collected groundwater samples from monitoring wells MW1 through MW5, MW7, MW8, MW9, MW12, MW13B through MW16B and from vapor wells VW1 and VW3 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 site 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 8260B, 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 MW7, MW9, MW12, MW 15A and MW 15C Benzene was detected in all wells sampled except for MW7, MW9, MW12, and MW15A through MW 15C 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 MTBE continues to below laboratory method detection limits (MDLs) in wells MW1, MW2, I MW5, MW8, MW13B and MW15C MTBE was detected in wells MW3 (34,000 parts per billion - ppb), MW4 (7,500 ppb), MW7 (68 ppb), MW12 (60 ppb) and MW14 (63,000 ppb), which are located along the southern portion of the site (Figure 2) In downgradient wells MW 15A and MW 15B (Eugenia and Market) MTBE was reported at concentrations of 8 6 ppb IIGZA_FSIVOL_IIDATAIGROUNDZEIROEKIQMR1200313gm2003 doc