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-~ - - - <br />2.0 HONITORZNC WELLS <br />Prior to slurry wall construction and dam grouting, five monitoring wells, <br />numbered P-!6 through P-20 (sample points 27 through 31 on Figure 2), were <br />installed downstream of the lover tailings dam. The installation of these <br />yells began on June 29, 1982. Drilling began vith hole number 16 and pro- <br />gressed sequentially through hole number 20. The monitoring well installation <br />program vas completed on July 9, 1982. <br />Three monitoring yells, P-16, P-17, and P-18 were installed approximately 100 <br />Eeet downstream of the slurry vall centerline near existing sampling point <br />number 25. The screened sections vere sealed into rock at varying depths <br />ranging from 42 to 80 feet. Tvo other wells, P-19 and P-20, vere installed <br />through the toe of the embankment near its intersection vith the ground <br />surface. These yells.were also sealed into rock, at depths of 28 to 33 <br />feet. Appendix A contains the boring logs for each yell borehole. Appendix B <br />contains the as-built dravings for the yells. <br />r- <br />The purpose of the wells vas to: <br />o Evaluate piezometric surface changes with construction <br />of the slurry vall and completion of the grouting <br />program. <br />o Measure piezometric pressures at each screened horizon <br />in order to define zones and directions of seepage <br />floe. <br />o Provide vater quality data to evaluate changes in <br />ground water quality after slurry vall construction. <br />,~ The borings vere advanced with a Mobile B-80 drill rig using a roller bit and <br />NW rasing to top of competent rock and vith a NX diamond bit to core into <br />rock. Standard penetration test samples vere taken at regular intervals in <br />1 the soil above the rock. <br />2 <br />