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' Mr.Nuel Henderson <br /> Page 2 of 4 <br /> potentiometric surface was above the top of the screened intervals in monitoring wells MW4 <br /> through MW13B, MW15B, MW15C, MW16B and vapor wells VW1 and VW4. Vapor well <br /> VW5 was dry. Groundwater flowed in a northeasterly direction. The gradient across the site <br /> was approximately 0.002-0.003 feet per foot. A potentiometric surface map generated using <br /> the August 24, 2004 groundwater elevation data from all site groundwater monitoring wells is <br /> ' shown on Figure 2. Groundwater monitoring data are summarized in Table 1. Monitoring <br /> data sheets and well construction details are included in Attachment A. <br /> On August 24, 25 and 26, 2004 a Ground Zero technician collected groundwater samples from <br /> monitoring wells MW1 through MW5, MW7, MWS, MW9, MW12, MW13B, MW14, <br /> MW15A through MW15C, MW16A and MW16B; and from vapor wells VW1 and VW3. <br /> A minimum of three well casing volumes was purged from each well prior to sampling. <br /> ' During the purging process, physical parameters (pH, electrical conductivity, and temperature) <br /> were monitored. Subsequent to parameter stabilization, and 100% recovery of initial depth to <br /> groundwater measurements, groundwater samples were collected and placed in an iced cooler <br /> for transport to Argon Laboratories (ELAP #2359) under chain of custody protocol. <br /> Analysis consisted of gasoline oxygenates, EDB and 1,2-DCA by EPA Method 8260B, TPHg <br /> ' by EPA Method 8015B and BTEX by EPA Method 8021B. Purge water was transferred into <br /> marked 55-gallon drums approved by the Department of Transportation (DOT). The waste is <br /> stored onsite within a secured area. Purge logs are included in Attachment A. <br /> GROUNDWATER ANALYTICAL RESULTS <br /> Groundwater Monitoring Wells <br /> ' TPHg and benzene were detected in all sampled wells except MW 1 (were only TPHg was <br /> detected), MW7, MW9, MW12 and MW 15A, MW 15B (were only TPHg was detected), and <br /> ' <br /> MW15C. Dissolved TPHg and BTEX levels in the remaining monitoring wells were within <br /> historical ranges, and appear to be stable to decreasing. TPHg and BTEX concentration data <br /> are summarized in Table 2. Attachment B contains laboratory reports and chain of custody <br /> documentation. Attachment C contains graphs of contaminant concentrations over time. <br /> MTBE was below laboratory method detection limits (MDLs) in wells MW1, MW2, MW5, <br /> ' MW13B, MW15C and MW16B. MTBE was detected in wells MW3 (25,000 parts per billion <br /> - ppb), MW4 (4,400 ppb), MW7 (140 ppb), MWS (5.5 ppb), MW9 (33 ppb), MW12 (110 <br /> ppb), MW14 (43,000 ppb) and MW16A (580 ppb). These wells, except MW8 and MW9, are <br /> ' located along the southern portion of the site (Figure 2). In downgradient wells MW 15A and <br /> MW 15B, MTBE was reported at concentrations of 3.0 ppb and 450 ppb, respectively. These <br /> ' wells are clearly affected by offsite releases. <br /> ' \\GZA_FSIVOL_11DATAIGROUNDZE\ROEKIQMR120040grn20O4.da: <br />