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I I I I I I I I I I I I I I I I I I I Geotechnical Engineering Investigation Case 4: Zoned embankment, Reservoir Water EI. 10,270 feet, upper 40 feet (elevation 10,250 to 10,290 feet) are fractured rock extending to the upstream face of the embankment, foundation rocks fractured and penneability of the downstream shell material is the same as that of the fractured rock. Case 5: Homogeneous embankment, Reservoir EI. 10,270 feet. Penneability = 10-2 ft/sec Seepage Analyses Results The seepage analyses results for all cases analyzed, zoned and homogeneous embankment, and with different reservoir elevations, indicate that the exit point should theoretically be located at the toe rock buttress of the embankment. The analyses do not account for water inflow that may be entering the embankment laterally from the left abutment. The initial finite element mesh along with the corresponding flow nets are included in Appendix D. The computer output for the first and final iterations are also included. Hydro-Triad reported that the entry point for the dye test was about 15 feet upstream of the upstream geomembrane anchor trench, about elevation 10,268 feet. The exit point was about elevation 10,225 feet on the downstream abutment-embankment groin. The finite element analyses indicate that the exit points range from elevation 10,220 to 10,230 feet (refer to nodal points 155 to 170) for the computer model we prepared, material properties we assumed and given reservoir level. These values are thus in general agreement with field observations, considering that iflateral groundwater inflow is occurring from the abutment the phreatic surface and exit points would logically be higher along the embankment's face. It should also be noted that the phreatic surface elevation of the computer model correlates very closely with the piezometer readings, CA-I and CE-2, which correspond to nodal points 35,43 and 51. Examination of the final finite element meshes and flow nets indicate that the factors of safety against piping at the exit points range between 2 and 3.5 along the downstream face. The lower factors of safety correspond to the higher reservoir pool. It should also be noted that the weight of the downstream rock benn was ignored along the lower seepage areas. The possibility of soil piping is considered somewhat unlikely because the embankment shell is predominantly composed ofsand and gravel with fines content generally between 2 and 10 percent. In addition, the downstream shell's material composition meets the filter criteria, as set Continental Dam Page 16