Page - 94 - in Book of Full Papers - Symposium Hydro Engineering

In DWR’s discussions with the contractor about the scope of work and schedule, it was determined that the November 1, 2017, completion target could not be met with a design concept that included both RCC foundation replacement and conventional reinforced-concrete slabs and walls. Therefore, an Interim RCC Foundation Replacement Concept was developed that restored the RCC walls, though at a lower level to allow up to 2800 m3/s (100,000 ft3/s) as a solution for an interim period only during the 2017-2018 Winter Flood Season. The plan was to shotcrete the inside of the RCC walls for the interim period, then remove the RCC walls in the 2018 construction season to allow completion of the reinforced-concrete slabs and walls as originally designed, as shown in Fig. 6. Figure 6 - Interim RCC Foundation Replacement Concept The characteristics of the Interim RCC Foundation Replacement Concept are provided below:  RCC is used as the foundation replacement material from Station 28+35 to 39+00.  A minimum RCC thickness of 1.5 meters (5 feet) perpendicular to the chute slope is provided in the RCC area of the FCO Spillway chute (Sta. 28+35 to 39+00).  The RCC foundation replacement is placed in horizontal layers below the planned final 4:1 finished grade of the reinforced-concrete spillway chute, creating a roughed-in 4:1 slope for the chute.  A final 30 cm (12 inch) thick layer of RCC would be placed monolithically on a 4:1 slope using a higher-strength enriched RCC mix to provide a durable surface for the 2017- 2018 Winter Flood Season, leaving the final RCC chute surface about 0.91 meter (3 feet) lower than the planned finished reinforced-concrete slab chute grade.  At the upper end of the RCC (Sta. 28+35), a vertical 0.91-meter (3-foot) step from the FCO Spillway update chute finished reinforced concrete surface to the downstream RCC surface would be used as an aeration ramp with a vertical chimney section at each abutment to allow air to be incorporated into future flows.  At the lower end of the RCC (Sta. 38+00 to 39+00), a 30.5 meter (100-foot) long transition section would slowly bring the RCC chute surface up flush with the finished FCO Spillway lower chute reinforced-concrete surface.  Shorter 4.9 meter (16-foot) high RCC walls would be constructed with a similar design as the initial concept - a vertical inside face, 4 meters (12.5 feet) across the top and 1:1 side slopes on the outside faces], which is designed to accommodate a design flow of 2,800 m3/s (100,000 ft3/s).  A minimum of 6 inches of the inner wall face would be constructed using reinforced shotcrete to provide a durable surface for the 2017-2018 Winter Flood Season. 94