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SECTIONFOUR Formulation of Alternatives <br /> 4-3 <br />spillway chute will be installed, with a new floor slab and chute walls being constructed on the <br />interior of the remaining portion of the existing chute. A drainage system will be installed <br />beneath the spillway chute. This system will consist of an 8-inch. HDPE underdrain pipe <br />embedded in drain gravel with a layer of filter sand on the outside of the gravel. Spillway chute <br />walls will be anchored to the adjacent ground with soil nail anchors and rock bolts, and <br />foundation anchors will be installed to anchor the chute floor to the underlying embankment. <br />Instrumentation proposed for Continental Dam includes structural survey points on the <br />reinforced concrete spillway, movement monuments on the filter blanket, two new nested <br />piezometers near the maximum section, and a metering manhole on the toe drain pipe. The <br />existing piezometers are to be modified to accommodate the revised grading on the downstream <br />face of the dam. <br />Borrow for filter sand, drain gravel, and common fill is expected to be required for the <br />dam rehabilitation and will be imported. Excavation will take place for construction of the filter <br />blanket, toe drain, spillway chute, and stilling basin. The excavated materials can be screened <br />and then used as common fill material or riprap. <br />Design drawings and a detailed construction cost estimate are presented in Appendix D.