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I I I I I I I I I I I I I I I I I I I concrete must also be moist cured with water for seven (7) days after placement to decrease the permeability. 4. Patchin!! and Groutin!!. Patching and grouting of the structure will require all deteriorated areas to be cut out and sandblasted prior to placing grout. Grout for all patching will be pre-packaged, non-shrink grouts. Bonding compounds will be required for all applications as recommended by the grout manufacturers. Grouting under the existing base slab would be accomplished by coring holes through the slab and installing a grout nipple in the slab. The grout mixture shall consist of 1 part Portland cement to Ih part sand to 1 part water. 5. Abutment Protection. The abutments on each end of the structure will be protected with a three-foot (3 ') layer of thirty-inch (30") riprap. The riprap sizing will range from thirty inches (30") to three inches (3") in size. 6. Gates. Several options and alternatives were considered for necessary gates to control the pool level behind the structure. The control gate operators will be electric motor driven as manufactured by Hydro Gate or Waterman Industries specifically for radial gates. 7. Overflow Section. The overflow section will be designed to minimi7e the downstream erosion of the river channel and minimi7e the backwater created during high flows over the section. Consideration will also.be given to details to minimi7e the accumulation of trash on the wall. The elimination of debris collecting on the structure is not possible, but the crest can be configured to help minimize the accumulation. The overflow section will be approximately 120 feet wide. The crest will be of a ogee configuration with a sloping upstream face. The downstream face will be shaped to pass the head resulting from a flow from a to-year flood. The stilling basin will also be sized for the to-year flood. The design of the stilling basin consists of a flat bottom with baffle blocks used for energy dissipation and reduction in the overall length of the basin. The base stilling basin will be set approximately two feet (2') lower than the existing apron to improve tailwater conditions. 8. Drains. Drains are recommended under the downstream erosion protection apron to improve its stability. Drains will reduce the pressure under the slab and will reduce the possibility of it floating when there is a full head of water against the overflow wall. The drains will consist of a gravel blanket and PVC pipe under the slab with weep holes through the downstream cutoff wall. The weep holes will be constructed of slotted pipe with fIlter materials to ensure fmes are not removed from under the structure. PAGE 13 _ CbapcerV