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5.9.3.8 Foundation excavation requirements necessary to provide a firm foundation for <br />the dam shall be documented in the Geotechnical Report. The Geotechnical Report shall <br />provide excavation requirements for shaping of the foundation to provide more uniform <br />foundation stresses or to minimize dam cracking. <br />5.9.3.9 Foundation drainage design shall be provided including justification for reduction <br />in uplift pressures on the dam. The efficiency of the drainage system to reduce uplift <br />pressures under the dam shall be based upon the geology of the dam foundation. The <br />ability to maintain the drainage system to meet the requirements assumed for the design <br />of the dam shall be addressed. <br />5.9.3.10 Confirmation of foundation design assumptions is required after the foundation <br />for the dam has been exposed. The project geologist and design engineer shall confirm <br />foundation conditions assumed for the design. Changes in foundation conditions from <br />assumptions made in the Geotechnical Report shall be communicated to the State <br />Engineer when they are identified during construction. Changes to the foundation design <br />for the dam shall be submitted to State Engineer's Office in a formal Change Order <br />Request during construction per the requirements of Rule 9. <br />5.9.4 Embankment Dam Design Requirements <br />5.9.4.1 Stability Analysis - Embankment dams shall be designed to have stable slopes <br />during construction, and under all conditions of reservoir operation, including rapid <br />draw-down of the reservoir. <br />5.9.4.1.1 Factors of safety shall be evaluated by slope stability analyses <br />methodologies that are acceptable to the State Engineer. The analysis models shall <br />adequately represent, for the critical cross section (or sections) of the dam, the <br />embankment geometry and internal zoning; shear strengths and unit weights of each <br />material; pore water pressures; and external loading or other relevant factors. Shear <br />strength and pore pressure assumptions used in stability analyses should be obtained <br />from tests that appropriately model the loading condition being analyzed. Where <br />appropriate, the analyses shall consider non-circular or wedge-shaped failure <br />surfaces, as well as circular failure surfaces. All parameters and assumptions used in <br />the analysis shall be summarized in a table, and justified in the Geotechnical Report. <br />A scale drawing, utilizing the same scale for vertical and horizontal dimensions, shall <br />be provided for each cross-sectional model used in the analysis, with the critical <br />failure surface(s) identified. Appropriate data sheets and representative computer <br />program output shall be provided in the report. <br />5.9.4.1.2 Minimum factors of safety for slope stability of embankment dams for <br />various loading conditions other than seismic loading are summarized in Table 5.5 <br />26