ARCHIVED REPORTS XR0010073 - Laserfiche WebLink

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Additional field modifications were added during the April 19, 2001 work This consisted of moving borehole locations to attempt to delineate the edges of the contaminant plume based upon drilling field observations The final borehole locations are presented on Figure 1 Reconnaissance Groundwater Sam_RIin A total of eleven boreholes were sampled in April 25, 2000 and April 9, 2001 using push or dull rods as temporary casing Boring PB-14 collapsed winch prevented the collection of a groundwater sample Borehole PB-20 collapsed upon the GeoProbe sampler and the threads failed which attached the sampling equipment Very severe flowing conditions completely covered the sampler equipment preventing recovery, and the borehole was cemented at that point Depth to groundwater measurements were made to the nearest one-one hundredth of one foot from existing grade, and also checked for the presence of separate phase product prior to sample collection The groundwater sample was carefully collected with a clean disposable bailer, or GeoProbe water sampler, which advances a clean screen into the aquifer strata, and poured into the appropriate laboratory prepared container with minimum cavitation and headspace Each water sample was labeled, logged onto a chain- of-custody hain- ofcustody form, and placed in a chilled ice chest on crushed ice • Subsurface Conditions A total of twelve exploratory borings were drilled at the locations shown on Figure 1, the deepest of winch was advanced to a termination depth of 26 feet The site is underlain by silty clay to depths of about 8- to 10-feet Thus clay is underlain by interbedded clay, clayey sand, silty sand, and sand to depths of about 20- to 24-feet, and compose the aquifer strata The sand is locally very clean and tends to flow and caused partial or total borehole collapse in all bonngs The aquifer strata are underlain by interbedded silty clay, clayey sand and clayey silt, which compose the underlying field confining strata at winch the bonngs were terminated in the range of about 24- to 26-feet Groundwater occurred at depths of about 12- to 14-feet and rose to about 9-feet indicating the aquifer strata are unconfined to very weakly confined On the basis of selected field groundwater measurements, groundwater appears to flow to the north, however there was insufficient time for levels to equilibrate for adequate data to plot a contour flow direction The historic groundwater flow direction as mapped in the existing monitoring wells is consistently northerly Page 5