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• -~- <br /> <br />:'his blanket will extend approximately one-guarter of the base width of <br />the dam. The purpose of the blanket aryl drain are to intercept water <br />due to consolidation as well as mssible underseepage beneath the dam. <br />This will prevent softening of the tce. Thickness of the blanket will <br />vary from 3 feet near the maximusa section and taper to 2 feet north of <br />Sta. 8+00. The upstream slope will be protected with riprap, and the <br />channel portion of the downstream toe will also be protected with <br />riprap. The riprap material will come fran cemented sandstone layers <br />and the overburden excavation. The spillway channel will be protected <br />with a gabion slope mattress filler with rock. The outlet works will <br />consist of an 19-inch diameter CtiP pipe with a sliding gate valve on <br />• the upstream face of the embankment. <br />Stability Analysis: Stability analysis was performed using data <br />previously obtained for the foundation soils and data presented in the <br />report for the embankment soils. A computer search of the most <br />critical failure circles usirg the modified Fellenius method was made. <br />The maximum dam height near Station 3 was used in the analysis. <br />Results of the analysis are shown on Figs. 3C and 3C. They show the <br />dam section to be safe under all conditions. The most critical time <br />for darn stability will be durin; and shortly after construction. In <br />order to insure stability during construction, it is recommended that ! <br />the actual construction time be extended as much as practical, particu- 3 <br />larly after the lower 20 feet of height. Piezometers wi~,l~be used to <br />• monitor the excess pore water pressure durirxl construction. <br />