ARCHIVED REPORTS XR0000784 - Laserfiche WebLink

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Mr Edward C Ralston March 13, 2001 Page 4 Groundwater analytical results are presented in Table 2 and summarized on Figure 2 Gettler Ryan's monitoring report, including groundwater sample analytical reports and chain of custody documents, are presented in Attachment D The groundwater flow conditions at the time of the groundwater sampling event are presented on Figure 3 The gradient was approximately 0 0015 foot per foot to the north This is consistent with historical gradients and flow directions • Well Surveying. Upon completion, the wells were surveyed by Morrow Surveying, a licensed surveyor for elevation relative to mean sea level Groundwater gradient was interpreted utilizing wellhead elevations and depths to water The Surveyor's map is presented in Attachment E • Sensitive Receptor Survey, IT previously reported the locations of water supply wells in the March 11, 1999 Offsite Resgarch and Sensitive Receptor Report A total of 12 water wells were identified within 1/2-mile radius of the subject site The primary uses are for irrigation and industrial purposes The nearest wells are located approximately 0 15 mile west/southwest of the site and are in the upgradient direction Monitoring well MW-8 delineated the upgradient extent of groundwater impacts The nearest downgradient wells are approximately 0 3 mile • northeast of the site A copy of the well location map and a tabular summary of the well survey data are presented in Attachment F CONCLUSIONS Site assessment activities identified the following subsurface conditions • Site soils consist of interbedded sands and silty clay • The lateral extent of petroleum hydrocarbon impact to soil is generally defined with exception of the capillary fringe TPH-g concentrations generally decrease with distance from the UST complex Three soil samples collected at depths of 10 to 15 feet bgs contained TPH-g at concentrations exceeding 100 ppm Benzene was detected in five soil samples at concentrations less than 1 ppm The petroleum hydrocarbon impacts to soil are likely due to migration of impacted groundwater away from the site • The vertical extent of petroleum hydrocarbon impacts to soil was previously delineated by boring GP-1 • Depth to groundwater ranges from approximately 10 77 to 12 48 feet bgs and the gradient is to the north at the magnitude of approximately 0 0015 ft/ft. • The extent of off-site groundwater impacts has not been defined to the north, east, • and west Groundwater samples collected from on- and downgradient off-site 911005 1C/1205wp 0301 doe IT Corporation