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' San Luis Mine Phase II, Raise 2 Design Report ' 2.4 piezometers As per the Amendment, a series of five vibrating wire piezometers were installed at the base of the ' Phase I embankment immediately above the liner. These piezometers were installed to monitor phreatic conditions within the embankment in order to confum that the structure remains drained ' as designed. Data compiled for the Phase II Raise 1 design indicated that these piezometers were not functioning properly and they were replaced with five standpipe piezometers installed from the 8590 ft crest of the main embanlanent to a depth approximately 10 ft above the liner. ' Five standpipe piezometers were also installed along the 8605 ft crest of the Raise 1 embankment ' which extend into the tailings immediately beneath the base of the raise fill. In addition, Five standpipe piezometers were installed along the upstream toe of Raise 1. Thesd piezometers were designed to be free standing with a base on the tailings supporting Raise 1 for burial by subsequent tailings. These piezometers were installed to monitor the phreatic conditions in the tailings which will support Raise 2 and will be covered when Raise 2 is constructed. The additional Raise 1 crest ' and tailings piezometers were installed to fulfill the requirements of Stipulation 1 of Technical Revision No. TR-016. Figure 9 shows the piezometer locations. Details of the piezometer installations and monitoring data are presented !in_,;Apppendix B.4. No water was detected in any of the embankment or tailings at the time of the field investigations presented herein. This data confirms the lack of saturated tailings overlying the upstream toe of Raise 1 as identified by the CPT pore pressure dissipation data and the lack of a phreatic surface ' in the embattlattent fill. ' 2.5 Laboratory Testing Samples collected from the borings were saved for laboratory testing. Physical testing consisted of ' grain size analyses, Atterburg Limits and triaxial shear. Previous test work indicates that the whole tailings consist of approximately 60 percent by weight which is finer than a No. 200 sieve (0.74mm). Grain size analyses of sand tailings indicate that 30 to 50 percent of this material is finer than a No. 200 sieve. Grain size analyses of the finer grained ' tailings ("slimes") indicate that 70 to 95 percent of this material is finer than a No. 200 sieve. Grain size analyses of mixed tailings indicate that 50 to 70 percent of this material is finer than a No. 200 sieve. The gradation test results are presented in Appendix D. ~ Y 2-7 ro~ec[ o.