Purpose
The U.S. Army Corps of Engineers is responsible for maintaining a 9-foot navigation channel in the Mississippi River as an important component of the inland navigation system.
Location
The St. Paul District is responsible for maintaining the Upper Mississippi River 9-Foot Channel from the head of navigation at Minneapolis, Minnesota, to Guttenberg, Iowa. The study is located in upper Pool 4 above Lake Pepin on the Mississippi River.
Description
Since 2012, the St. Paul District has dredged an average of 1,069,000 cubic yards annually at 35 locations using both federal and contract hydraulic and mechanical dredges on the Upper Mississippi River (UMR). The Corps extensively plans and actively manages dredged material placement for beneficial use, using innovative, revolutionary, and technological solutions, including habitat and recreation activities, all while improving navigation safety and reducing dredging requirements.
The purpose of the study is to investigate if any action(s) would reduce the dredging frequency in the study area. Navigation in upper Pool 4 has been negatively affected by sedimentation in the navigation channel. Sedimentation occurs in the navigation channel as the UMR enters Lake Pepin and velocities slow causing sedimentation. Placement site limitations are impacting the St. Paul District’s ability to dredge as needed in the UMR. The objective of the study is to reduce dredging frequency and enable a self-maintaining channel in the upper Pool 4 navigation channel from river miles 788 to 783 and improve channel conditions for both commercial and recreational traffic.
Status
The study has consisted of iterative hydraulic and sediment modeling of potential constructable solutions to improve conditions, such as wing dams, channel realignment, islands, and side channel closures. The study identified potential river training structures across secondary channels and island construction to channelize the river. Measures that wouldn’t improve conditions or would not be feasible were screened from consideration.
Minimal channel widths and depths are present in a few areas and require dredging to allow unrestricted navigation. The study area has limitations on dredged material placement opportunities. The St. Paul District continues to develop dredged material management plans for the UMR.
Authority
Congress authorized the UMR 9-Foot Channel Navigation Project via the Rivers and Harbors Act on July 3, 1930. Channel maintenance is 100% federally funded except for short segments of the Mississippi River in Minneapolis and on the Minnesota River.
Funding
The federal cost of channel maintenance for the St. Paul District is approximately $30 million annually, and funding needs continue to increase, partially due to the increased cost of managing dredged material.
The study to-date costs approximately $300,000.