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Title: Environmental Assessment for Sunflower Advance Maintenance Dredge Cut on the Tombigbee River, Clark and Washington Counties, Alabama
Authors: United States. Army. Corps of Engineers. Mobile District.
Keywords: Dredging
Environmental management
Tombigbee River (Miss. and Ala.)
Publisher: United States. Army. Corps of Engineers. Mobile District.
Abstract: The Mobile District has conducted annual maintenance dredging most years in the Sunflower reach of the Tombigbee River portion of the Black Warrior-Tombigbee Waterway, specifically between Miles 79.0 and 78.0 in order to maintain the federally authorized navigation channel for commercial traffic. The amount of dredging has varied over the years. Between 2011 and 2016, the average amount of material removed from the channel was approximately 83,000 cubic yards per year, at an average cost of $4.00 per cubic yard, or $332,000 per year. Historically, since 1981 the average volume has been approximately 105,000 cubic yards, with two events exceeding 250,000 cubic yards. The river thalweg crosses from the left descending bank toward the right descending bank in a relatively short length of river near River Mile 79.2. As is typical of many river crossings, there is a tendency for shoaling that has the potential to present hazards to navigation during lower river stages. The alignment of this crossing can also be problematic for navigation as it involves a sharp transition from one side of the river to the other. The reach between River Miles 79.1 – 78.0 has also shown a tendency to become too shallow for navigation and requires repetitive channel dredging to maintain the navigation channel. Specifically, the bar along the left descending bank has a tendency to build out toward the right descending bank leaving insufficient navigable width for barge tows to safely traverse this reach. Frequent dredging of this reach requires disposal management to ensure future navigation operations. Since 1984, this dredged material has predominantly been placed within the Sunflower upland dredged disposal site located off the left descending bank at River Mile 78.3. There are several sites along the river channel that have also been used for dredged material disposal in recent years if conditions and dredge quantities were small enough to allow. Prior to using the upland dredged disposal area, within bank disposal areas were utilized. However, the upland dredged disposal site located off the left descending bank at River Mile 78.3 has reached capacity. Constructing this advanced maintenance cut will reduce dredging frequencies, projected quantities of dredged material, and upland dredged disposal area capacity needs. The reduction in dredging needs would eliminate the need for acquisition of low-lying riverfront property for construction of a new approximate 70 acre upland disposal area for dredged material.
Description: Environmental Assessment
Rights: Approved for Public Release; Distribution is Unlimited
Size: 138 pages / 13.41 Mb
Types of Materials: PDF/A
Appears in Collections:Environmental Documents

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