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KLEINFELDER 3.1.3 MONITORING WELL INSTALLATION Three monitoring wells were installed through obvious hydrocarbon stained areas at the Weston Ranch parcels. Monitoring well MW-1 was installed at area HS-4 in central boring B-2, MW-2 was installed at area HS-1 in central boring B-10, and MW-3 was installed at area HS-1 in central boring B-11. The locations of the HS areas and monitoring wells are shown on Plates 2 and 3, Appendix A. While drilling, water was encountered at an approximate depth of 11 feet below grade at HS-4, 5 feet at HS-1, and 6 feet at HS-2. The monitoring wells were constructed as follows: o The soil borings were drilled with 8-inch hollow-stem augers. o The well casing is 2-inch inside diameter, flush-threaded joint, Schedule 40 PVC pipe. The PVC casing was steam cleaned prior to installation in each borehole. o Well screen sections are perforated with 0.010-inch factory-cut slots. o The annular space between the wall of the borings and the casing was backfilled with Lone Star Industries 0/30 sand to approximately 1 foot above the top of the perforated section. o A 2-foot bentonite plug was placed above the sand pack to provide a seal against surface water infiltration. o Each well was secured inside a locking well cover. A confined aquifer condition was not indicated; therefore, the screen section was installed 1 to 2.5 feet above and 5 to 8 feet below the first encountered ground water. The ground water zone consists primarily of silt and fine sand, therefore, 0.01-inch slotted screen and 0/30 filter sand were selected for well construction. The smaller slot size and finer sand pack were used to best duplicate the natural aquifer condition and aid in well development. Specific construction details for each monitoring well are presented on Plates 9, 17, and 18, Appendix A. 161-89-107 6