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S Report—Monitor Well Installation and Sampling New Jerusalem School February 26,1999 �.. Page-3 3.3 MONITOR WELL CONSTRUCTION 'r The monitor wells were constructed with 23 feet of 2-inch outside diameter, Schedule 40, flush-threaded, machine-slotted PVC screen (slot size 0.020). A flush-threaded PVC bottom cap was placed at the bottom of the screen. Blank PVC casing was installed above the screen to the ground surface_ No glue or solvents were used in the construction of the wells. A sand pack of 93 Monterey sand was placed in the annular space to approximately one foot above the �., top of the well screen. Approximately one-half foot to one foot of bentonite pellets was placed above the sand to form a protective sea]. The bentonite was hydrated using potable water. A seal of neat cement was poured in the annulus from the bentonite seal to the ground surface. A locking compression cap and a traffic box were installed for each monitoring well. Monitor well construction diagrams are shown on the Drilling logs included in Appendix B. 3.4 WELL COLLAR SURVEY A survey was conducted by a licensed professional surveyor to determine the location and relative elevations of the newly installed monitor well collars. The well collars were surveyed using an assumed ,... datum elevation with a vertical accuracy of 0.01 foot and a horizontal accuracy of 1.0 foot. The measuring point for water-level measurements was marked on each well collar. The groundwater gradient, discussed in Section 6 of this report, was estimated using the survey information and depth to water measurements from each well. 3.5 MONITOR WELL DEVELOPMENT On December 21, 1998, each monitor well was developed by surging. On December 24, 1998, the monitor wells were developed by bailing until the purged groundwater was relatively free of sediment (clear of particles visible to the unaided eye). All well-development equipment was cleaned prior to use in each well by washing in a solution of laboratory-grade, non-phosphate detergent and hydrocarbon-free water, and double rinsing with hydrocarbon-free water. The purged groundwater was containerized in drums, sealed, labeled, and left on site to await disposal pending results of laboratory analyses. ,.., Groundwater well development field forms are included in Appendix C. 3.6 GROUNDWATER SAMPLING On December 29, 1998, a Condor representative was on site to measure water levels and collect groundwater samples from the facility's irrigation well and domestic well and the recently installed monitor wells. All down-hole field equipment was decontaminated in the field with a solution of +-� laboratory-grade, non-phosphate detergent and hydrocarbon-free water and rinsed with hydrocarbon-free water prior to use in each well. All field instruments were calibrated to the manufacturer's recommended standards_ The water level in each monitor well was measured to the nearest 0.01 foot with a battery- _. operated, flat-tape, water-level meter. A new, disposable, polyethylene bailer was lowered into each monitor well to collect a field-inspection sample. The bailer sample was inspected for floating product, sheen, discoloration, and odor. No floating product or sheen was observed in any of the monitor wells during the groundwater sampling. Petroleum hydrocarbon odors were not noted in the ground-water samples collected from monitor wells MW-1,MW-2,or MW-3. The monitor wells were purged with a new, disposable, polyethylene bailer. Each well was purged until three well-casing volumes of water had been removed and the electrical conductivity, pH, and temperature of the water had stabilized. The purge water was discharged to 55-gallon drums and left on site to await disposal. Groundwater Monitoring Field Forms are included in Appendix C. 4%� LM CONDOR �r