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Ms Margaret Lagono <br /> Page 2 of 4 <br /> led to the discovery of a damaged instrument The instrument was repaired and all wellhead elevations <br /> except for MWl l and MW12 (inaccessible) were resurveyed on April 10, 2001 Water levels rose 151 <br /> ' feet since last monitored on November 20, 2000 The potentnometric surface was above the top of the <br /> screened intervals in all monitoring wells except wells MW13 and MW14 and in vapor wells VWl, VW3 <br /> and VW4 Groundwater flow direction was generally to the east with a gradient averaging approximately <br /> ' 0 0025 feet per foot A groundwater gradient map generated using the March 6, 2001, monitoring data is <br /> shown on Figure 2 Groundwater monitoring data are summarized in Table 1 Monitoring logs and well <br /> construction information are included in Attachment A <br /> ' On March 6, 2001 through March 8, 2001, a Ground Zero technician collected groundwater samples from <br /> groundwater monitoring wells MW 1 through MW 14 and vapor wells VW 1 through VW6 A minimum of <br /> three well casing volumes was purged from each well prior to sampling During the purging process, <br /> physical parameters (pH, conductivity, and temperature) were monitored in each well and allowed to <br /> stabilize before collecting groundwater samples Samples were collected after a minimum of 80% water <br /> level recovery Purge water was contained in labeled 55-gallon drums approved by the Department of <br /> Transportation (DOT) The drums are stored onsite On January 26, 2001 American Valley Waste Oil <br /> transported 980 gallons of purge water offsite for disposal Purge logs are included in Attachment A <br /> Samples collected for analysis were placed in an iced cooler and transported under chain of custody to <br /> Argon Laboratories (FLAP #2359) TPHg and BTEX were analyzed using EPA method 8015 modified <br /> and EPA method 8020, respectively Oxygenates, EDB, 1,2 DCA, methanol and ethanol were analyzed <br /> '• using EPA method 8260 <br /> Groundwater Analytical Results <br /> ' Groundwater Monitoring Wells <br /> TPHg was detected mall wells except MW6, MW7,MW9 and MW 11 Benzene was detected in each well <br /> ' except MW9 and MW 11 Overall, TPHg and BTEX concentrations at the site appear to be stable to <br /> decreasing TPHg and BTEX concentrations are summanzed in Table 2 Attachment B contains <br /> laboratory reports and chain of custody documentation Graphs depicting TPHg and benzene <br /> ' concentrations over time are included in Attachment C <br /> MTBE was detected in the wells on the southern portion of the property (MW3, MW4, MW7, MW 12 and <br /> ' MW 14) and in the wells offsite on the north side of Market Street (MW9 and MW 10) These wells are <br /> affected by offsite releases of gasoline hydrocarbons EDB was detected in monitoring well MW2, 1,2 <br /> DCA was present in the samples from monitoring wells MW2, MW9, MW 10, MW 11 and MW 12 <br /> Analytical results for oxygenates and gasoline additives are summarized in Table 3 Attachment B <br /> contains laboratory reports and chain of custody documentation <br /> Vapor Extraction Wells <br /> Petroleum hydrocarbons were detected in all samples collected from the vapor extraction wells In paired <br /> deep/shallow vapor wells VW1/VW2 and VW4/VW5, the wells with the deeper screened intervals <br /> exhibited higher concentrations of target analytes than the shallower wells <br /> . The only oxygenates/additives detected in the vapor wells were 590 parts per billion (ppb) EDB in vapor <br /> ' well VW1 and 190 ppb 1,2 DCA in vapor well VW4 TPHg and BTEX concentrations are summarized in <br /> ' mdcVWiQe¢oa <br />