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KLEINFELDER 4 GROUNDWATER ASSESSMENT This section summarizes the monitoring well construction, development, sampling, and surveying, and presents the results of both quarters of the gradient and analytical data The monitoring wells were installed to assess the groundwater in the vicinity of the T2/T3 tank site 4.1 MONITORING WELL CONSTRUCTION The monitoring wells were constructed inside of 8-inch diameter hollow-stem flight augers The wells were constructed of 2-inch diameter, Schedule 40 flush threaded ASTM-F480 PVC pipe, and 0 020 millslott well screen Each of the wells was screened from approximately 30 to 50 feet below the ground surface Lonestar #2112 sand was used for the filter pack, 3 318-inch bentonite pellets prevented grout infiltration into the filter pack Each of the wells was sealed to surface with an approximately 4 percent bentonite grout installed through tremie pipe The well casing was sealed at the surface with a locking compression style plug Each well head was completed inside a traffic rated monitoring well vault box A summary of the construction details is presented on Table 2 Well construction details are shown on the boring logs included in Appendix B 4 2 MONITORING WELL DEVELOPMENT AND SAMPLING On January 20, 1993, the three monitoring wells were developed to draw sediment from the formation and filter pack into the well, set the filter pack, and increase the hydraulic conductivity of the well Development was accomplished using a bailer After development, each well was purged until the discharge water was relatively clear of sediment. Approximately 40 gallons (approximately 15 well volumes) were purged from each of the wells On January 26, and March 25, 1993, water samples were collected from the wells Prior to sampling, water levels were measured in each of the wells as follows A Simco Model 51453 conductivity based water level indicator was used to measure the depth to groundwater to the nearest 0 01 foot 24-220152-Doo/FR12-105 (1993) Page 7 of 18 July 27, 1993 copyright 1993 Kteinfelder, Inc.