The US Army Corps of Engineers, Rock Island District (District), requests your review of the Supplemental Environmental Assessment (SEA) titled, Dredge Material Management Program Buffalo Site 5 Access Channel Mississippi River, Pool 16, River Miles 471.3 to 471.5, dated February 2022. The District is interested in your review and comments regarding the alternative analysis and project outcomes. The District is also letting the public know how the District plans to meet its environmental compliance requirements.
The public is invited to submit comments regarding the alternative analysis and Proposed Alternative for this project through March 14, 2022.
Comments can be submitted via this online COMMENT FORM, through email at: PublicInvolvement@usace.army.mil, or by writing to the address below.
To request a paper copy or CD, contact the District’s Environmental Compliance Branch at 309-794-6104, email PublicInvolvement@usace.army.mil, or write to:
Department of the Army
US Army Corps of Engineers, Rock Island District
Attn: Bales(PD-P) Clock Tower Building
P. O. Box 2004
Rock Island, IL 61204-2004
PROJECT INFORMATION
The District is directed by Congress to maintain a 9-foot navigation channel on the Upper Mississippi River (UMR). The natural fluvial process causes the bedload of the UMR to be in a constantly moving, dynamic state. These sediments occasionally threaten navigation by causing the channel to become narrow and/or shallow at localized sites. Maintenance involves dredging of accumulated sediment to restore the channel to proper navigation dimensions.
The District prepared an Environmental Assessment (EA) titled, Dredged Material Placement Site, Buffalo Dredge Cut Pool 16, Upper Mississippi River Miles 472.0-473.2, October 1997. The EA was written to determine environmental impacts, a requirement necessary to support the DMMP report titled Dredged Material Management Plan for Dredged Material Placement, Site Plan for the Buffalo Dredge Cut, Upper Mississippi River Miles 472.0-473.2, March 1998 (Buffalo DMMP). The District must construct an access channel from the 9-foot navigation channel to the Buffalo DMMP Site 5, an upland placement site documented in the aforementioned DMMP and EA, now to reach and use the site. The District prepared this Supplemental Environmental Assessment tiered from the original Buffalo DMMP EA to comply with the National Environmental Policy Act of 1969 (NEPA) guidelines.
ALTERNATIVES CONSIDERED
- No-Action Alternative. Under the No-Action Alternative there would be limited river access to Buffalo DMMP Site 5, and the site would not be utilized. Other previously used placement sites would be used for dredging as long as capacity allowed. Without access to Buffalo DMMP Site 5, if capacity becomes limited, the District may need to use previously undisturbed bankline or in-water placement areas that may have more aquatic environmental impacts.
- Proposed Alternative. Dredge an access channel from the main channel to the right descending bank. Clear an access corridor for dredging equipment and create a water return corridor for return water.
PROPOSED ALTERNATIVE
Alternative 2, Dredge a channel mechanically or hydraulically from main river channel to the bankline adjacent to Buffalo DMMP Site 5, enabling access to the site at all river levels. Approximately 8,000 cubic yards of material would be moved from the access channel to the Buffalo DMMP Site 3 (471.6-472.0R). The access channel would be 100 feet wide and 7 feet deep extending approximately 600 feet out to the navigation channel. Following completion of the access channel, the District would offload construction equipment on shore for dredging operations at Buffalo DMMP Site 5. Minimal tree removal would be required through the riparian zone to create a 25-ft wide by 200-ft long access corridor for construction equipment to reach the Buffalo DMMP Site 5 placement area from shore, as well as create a clearing for return water pipes. Once construction equipment reached the placement area, the District would prepare Buffalo DMMP Site 5 for future hydraulic channel maintenance events including a new fine sediment basin for mechanically dredged fine material. This containment area would create space for the District to dispose of fine material in an upland area. Return water would be routed through three 20-inch pipes from the drop structures at Buffalo DMMP Site 5. Minor excavation is needed to bury pipes and establish proper flow from the drop structures back to the river pipes.
To identify the alignment that would best avoid and minimize impacts, the District considered a zone containing a variety of access channel alignments to avoid environmentally sensitive areas and reduce dredging requirements. Factors considered included bathymetry, sediment type, and the presence of protected mussel species. Alternative access channel alignments within this zone may be re-considered, fully compliant, and coordinated through the OSIT should issues with the selected alignment arise over the life of the Project. Maintenance dredging may be required throughout the life of the project for the access channel and would be kept as close to the original access channel as possible.