For any man-made lake, getting water out of the reservoir is just as important as keeping it in. At the new Lake Fort Smith, water will be withdrawn for drinking water and discharged over the spillway when the lake level exceeds 911 feet above mean sea level.
Controlled release of water to the treatment plant will be made through a large diameter tunnel through the west abutment. Water directed to the treatment plant will flow through two pipes contained within the tunnel. Having more than one pipe improves the reliability of the water supply system. If one pipe fails or is closed for maintenance, water can still be delivered to the treatment plant through the other pipe.
Overflows from the reservoir would pass over a spillway. The original concept for the new spillway was a single channel sweeping around the west end of the dam similar to the current configuration, but larger. In this design, the spillway would handle both routine discharges from the lake and flood flows.
Currently, discharges from Lake Fort Smith pass through a single spillway.
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Studies have determined, however, that principal and auxiliary spillways will be necessary for the new lake. The plan currently being considered for the principal spillway consists of an approximately 300-foot long, side-discharge, S-shaped weir leading to a
trough near the west end of the dam. Water that enters the spillway would flow down and approximately 1,500 foot-long concrete channel on the west abutment of the dam. At the bottom of the channel, water would pass over energy
dissipation structures, then enter a stilling basin before flowing into Frog Bayou (see figures on next page).
The principal spillway would be able to discharge water produced by an up to 100-year flood. Water in excess of the 100-year flood level would pass out of the lake through the auxiliary spillway. The latter spillway would consist of a large channel cut into the bedrock between the west abutment of the dam and Highway 71.
New State Park
Merlin E. Seamon Associates, a recreation facility design subconsultant to Burns & McDonnell, continues to work with the city and the Arkansas Department of Parks and Tourism on designs for a new state park to replace the park to be eliminated by the new dam.
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