ARCHIVED REPORTS_XR0002356 - Laserfiche WebLink

Home Browse Search

(VATC A S S O C I A T E S I N C context of a site conceptual model that includes analytical data collected during removal of a waste oil tank from the site in September 2003. SAMPLING ACTIVITIES On November 26, 2003, ATC personnel collected groundwater samples from monitoring wells MWI through MW8. The locations of the wells are shown on Figure 2. Prior to collection of groundwater samples, the depth to water, pH, electrical conductivity, and temperature were measured in the monitoring wells and recorded. A minimum of three well casing volumes were purged from each monitoring well prior to sampling. The wells were allowed to recover and samples were collected from each well using disposable polyethylene bailers. The groundwater samples collected from each well were submitted to State-certified Argon Laboratories Inc. (ELAP Cert. No. 2359) in Ceres, California for chemical analysis of TPHg utilizing EPA method 8015 modified; benzene, toluene, ethylbenzene, and xylenes (BTEX) utilizing EPA method 8020; and methyl tertiary butyl ether (MTBE), ethyl tertiary butyl ether (ETBE) di-isopropyl ether (RIPE), tertiary amyl ether (TAME), tertiary butyl ether (TBA), 1,2- dichloroethane (1,2-DCA), and 1,2-dibromoethane (EDB) utilizing EPA method 8260. Groundwater well purge and sample logs are contained in Attachment 1. GROUNDWATER FLOW DIRECTION Water level measurements were collected from wells MW1 through MW8 on November 26, 2003. Water levels in the shallow aquifer ranged from 5.24 to 7.37 feet below the tops of the well casing elevations, representing an average increase in the shallow water table elevation of approximately 0.39 feet since September 2003. The water level data were used to develop the groundwater elevation contour map (Figure 2). Assuming that horizontal isotropic conditions prevail, groundwater in the uppermost aquifer beneath the site flowed towards the north. The average hydraulic gradient on November 26, 2003 was calculated to be 0.001 ft/ft or approximately 5 ft/mile. A summary of groundwater monitoring data is presented in Table 1. ANALYTICAL RESULTS The groundwater sample collected from well MW4 contained detectable concentrations of TPHg, benzene, and ethyl benzene constituents. Groundwater samples collected from wells MW 1, MW2, MW3 and MW5 through MW8 contained no detectable concentrations of TPHg or BTEX constituents. Grgundwater samples collected from wells MW1, MW4, MW5, MW6, and MW8 contained detectable concentrations MTBE ranging from 9.0 parts per billion (ppb) in MW 1 to 260 ppb in well MW5. The groundwater sample from well MW4 contained a detectable concentration of TBA and the groundwater samples from wells MW5 and MW8 contained detectable concentrations of TAME. Groundwater samples collected from wells MW2, MW3, and MW7 contained no detectable concentrations of MTBE, ETBE, DIPE, TAME, TBA, t,2- DCA, or EDB. Analytical results of groundwater samples are summarized in Table 2. s:lenviromental125847100371reportsl4gr-2003.doe 3 '