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