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<br />Slope stability will be designed to a safety factor of 1.25. A slope safety factor is typically determined by a <br />combination of the degree of uncenainty of the slope and foundation, and the consequences of failure. The <br />chosen safety factor is consistent with a designed slope in a moderate hazard location. The fill slope is in a <br />quarry and would Likely impact only the quarry owner if the slope failed. However, the fill slope will <br />t:ventually be above a proposed reservoir and there is a small risk that a failure could displace water if it were <br />to fail into the reservoir, potentially resulting in direct displacement overflow, or a wave if the failure was <br />rapid. Although this scenario is not likely because of a substantial buffer zone between the slope and the <br />reservoir, it is appropriate to use a moderately high safety factor to account for this condition. Additional <br />factors to consider are that the fill slope will be founded on a firm rock foundation, and it will be constructed <br />with engineering controls and will have relatively well defined and controlled properties in comparison to an <br />unconvolled fill or a poorly defined natural slope. <br />Design of the engineered fill slope will evaluate the use of several different soil materials with varying degrees <br />of compaction. In the event that these soils alone can not safely support the desired slope angle, the use of <br />geotextile as reinforcement, and soil augmentation with cement and/or fly ash will be considered. The fill <br />slope will be founded on rock. In areas presently containing fill and material stockpiles at the fill slope toe, <br />these previously placed soils will either be removed or evaluated for suitability for incorporation into the fill <br />slope. <br />Drainage of the slope will be accommodated with a series of blanket and strip drains. These drains will be <br />located at the slope toe and at the back edges of the lower benches. Additionally, a drain will intercept the <br />known ground water seep on the bench at El. 6,650 ft and convey the water out of the fill. Drains will be <br />constructed of coarse granular crushed rock, if necessary, with a separation and filter layer of finer crushed <br />rock or geotextile to prevent piping of surrounding materials and clogging of the drain rock. <br />A fill slope design submittal(s) will be made to DMG as part of the Annual Report Geotechnical Addendum <br />submitted each year by CAMAS. Laboratory testing is already underway and Haley & Aldrich intends to have <br />a design completed during the Fal] of 1998 that can be included as part of the 1998 Annual Report submittal. <br />In addition, because the construction of this rather large engineered fill will likely take place over a period of <br />years, performance and construction QA/QC information for the fill slope will become a regular part of future <br />Annual Reports during its construction. [f inswmentation becomes part of [he final slope design plan, <br />instrumentation data and analysis wit( also be provided to DMG annually for geotechnical review. <br />rxr XII - 3 <br />