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2-7 were identified with the same designation as the monitoring wells Monitoring Wells MW-4, MW-5, and MW-6 were installed during the supplemental Phase H Investigation Monitoring wells were constructed using flush-threaded, 2-inch diameter, Schedule 40 poly- vinyl chloride {PVC} riser and 10 feet of PVC, 0 010-mch mill-slotted screen fitted with a flush-threaded end cap The PVC casing was inserted into the boring with the hollow-stem augers left in place to the total depth of the boring The screen interval was placed with the top of the screen approximately 2 feet above the static water level at the tune of installation PVC riser was added so the top of the casing was approximately 1 5 to 2 feet above the ground surface Clean silica sand was placed in the annular space between the screen and the borehole wall to a depth approximately 1 to 2 feet above the top of the screen Hollow- stem augers were incrementally removed from the boring as the sand pack was being placed A bentomte pellet seal, with a thickness of approximately 1 to 2 feet, was placed on top of the sand pack and hydrated with potable water The bentonite pellets were permitted to set up for a minimum of 1 hour A bentonite/cement grout mix was placed on top of the ben- tonite seal in the annular space until it reached the ground surface The PVC casing was capped with a locking watertight hd A locking protective steel casing was placed over the ' PVC casing Detailed as-built drawings of each monitoring well are contained with the bor- ing logs in Appendix B Monitoring well construction data are provided in Table 2 Development of the monitoring wells was completed approximately 24 hours after mstalla- ' tion Water was bailed from each well for a penod of up to 60 minutes to remove fine cuttings that were produced during drilling Approximately 10 to 20 well volumes were removed from each well and pH, specific conductance, and temperature were measured after each successive 5 gallons of water removed. Monitoring well development was not consid- ered completed until successive pH, specific conductance, and temperature measurements were within 10 percent Summary sheets of each monitoring well development are presented in Appendix D Water removed was placed in 55-gallon drums and staged at the site for disposal 29025 I ' "REALISTIC SOLUTIONS FOR HAZARDOUS WASTE PROBLEMS"