ARCHIVED REPORTS_XR0012020 - Laserfiche WebLink

Home Browse Search

i Ms Margaret Lagono ' Page 2 of 4 • technician surveyed and tied in well casing elevations at the ARCO site, and exchanged depth to ' water data with Delta Water levels at the site rose approximately 0 42 feet since last monitored on March 6, 2001 The tpotentiometric surface was above the top of the screened intervals in all wells except monitoring wells MW13 and MW14 and vapor wells VW2, VW5 and VW6 Groundwater flowed in an easterly direction, and the average gradient was approximately 0 0025 feet per foot A ' groundwater gradient map generated using the monitoring data from all wells is shown on Figure 2 Groundwater monitoring data are summarized in Table 1 and Table 4 Monitoring logs are included in Attachment A On May 23, 2001 through May 25, 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% recovery of initial depth to groundwater measurements Purge water was contained in labeled 55-gallon drums approved by the Department of ' Transportation (DOT), which are stored onsite within a secured area 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 Gasoline oxygenates, EDB, 1,2 ' DCA, methanol and ethanol were analyzed using EPA method 8260 Groundwater Analytical Results ' Groundwater Monitoring Wells TPHg was detected in all wells except MW6, MW7, and MW9 through MW l2 Benzene was ' detected in each well except MW7, MW9, MW 10 and MW 12 Overall, TPHg and BTEX concentrations at the site appear to be stable to decreasing TPHg and BTEX concentrations 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 was detected in wells located along the southern portion of the property (MW3, MW4, MW7, MW 12 and MW 14) and in the wells located offsite along the north side of Market Street ' (MW9 and MW10) These wells are affected by offsite releases EDB was detected in monitoring well MW2, and 1,2 DCA was present in monitoring wells MW2, MW10, MW11 and MW 12 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 roeklgmr12QM2001