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Navigation Conditions at Lock and Dam 22, Mississippi River Hydraulic Model Investigation
ARMY ENGINEER WATERWAYS EXPERIMENT STATION VICKSBURG MS
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Lock and Dam 22 is located on the Mississippi River, 301.2 miles upstream of its confluence with the Ohio River. The principal existing structures are the main 110 by 600 ft lock located along the right descending bank, an incomplete auxiliary lock located riverward of the main lock, and a 1,024 ft long dam with ten 60 ft wide tainter gates and three 100 ft wide roller gates. An overflow dike with top elevation of 459.5 elevations el are in feet referred to the National Geodetic Vertical Datum extends from the dam to high ground on the left bank. The dam provides a navigation pool that extends upstream about 24 miles to lock and Dam 21. The dam is operated to maintain a navigation pool of el 459.5 at the dam. As the riverflow increases, the gates are raised so the normal pool el 459.5 will not be exceeded. A fixed bed model reproduced about 3.5 miles of the Mississippi River and adjacent overbank from about 10,700 ft upstream to about 7,700 ft downstream of the existing dam to an undistorted scale of 1120. Three locations are being considered for a new lock at Dam 22. The model investigation was concerned with evaluating navigation conditions for each lock location and identifying any needed modifications to the navigation channel alignment, guard wall lengths, or remedial structures. This information will also be used in the preliminary design of locks at other dam sites along the upper Mississippi River. Results of the investigation revealed that with all locations a system of dikes along the left bank and a ported upper guard wall would reduce the outdraft, eliminate the need for a helper towboat, and improve navigation conditions for tows entering and leaving the upper lock approach.
APPROVED FOR PUBLIC RELEASE