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Transcript of US Army Corps of Engineers BUILDING STRONG ® 2012 Alabama Water Resources Conference Orange Beach,...
US Army Corps of Engineers
BUILDING STRONG®
2012 Alabama Water Resources Conference Orange Beach, AlabamaSeptember 6, 2012
Beneficial Use Opportunities of Dredged Material from the Upper Mobile Bay Federal Navigation Channel
Larry ParsonPhysical ScientistU.S. Army Corps of EngineersMobile District
BUILDING STRONG®
•Approximately 4 MCY of material removed from Mobile Bay Channel annually at a cost of $12 million
•Currently restricted to hopper dredges and transported up to 40 miles for disposal in the Mobile-North ODMDS
•Historically dredging utilized cutterhead dredges with open-water disposal sites along channel
•Hopper dredges not able to keep up with maintenance requirements
•Limits the Corps’ access to smaller % of available dredging fleet
•Removes sediment from system•Exploring beneficial use opportunities
Description & Challenges
BUILDING STRONG®
Hopper Dredge
BUILDING STRONG®
Hopper Dredge
BUILDING STRONG®
Cutterhead Dredge
BUILDING STRONG®
• Investigate opportunities to resume in-bay disposal practice options for Mobile Bay navigation channel
•Utilizing environmentally accepted alternatives for beneficial uses of dredged material
•Demonstrate open water disposal with monitoring and predicting movement of sediment associated with in-bay disposal areas
•Utilization of cutterhead dredges providing flexibilities to employ a greater percentage of the available dredging fleet
Goals and Objectives
BUILDING STRONG®
Mobile BayInteragency Working Group (IWG)
• Establish and engage IWG to help identify and implement in-bay disposal and beneficial use opportunities
- Alabama Department of Conservation and Natural - State Lands Division ADCNR, Marine Resources Division- Alabama Department of Environmental Management- Alabama State Port Authority- U.S. Fish and Wildlife Service- NOAA, National Marine Fisheries Service- Alabama/Mississippi Sea Grant- Mobile Bay National Estuarine Program - The Nature Conservancy (TNC)
BUILDING STRONG®
• Is removing all the dredged sediment from the Bay the smart thing to do?
• Open water disposal has been recently conducted • 1998 – Hurricane Georges• 2005 – Hurricane Katrina
• Mobile Bay is a well studied system with numerous investigations regarding the affects of thin layer disposal showing minimal impacts
• Opportunity to resolve these issues in a manner that is sustainable while maximizing future benefits and minimizing impacts
• What is the best path forward?
In-bay Beneficial Use Considerations
BUILDING STRONG®
• Brookley Hole- Short term- In progress
• In-bay disposal- Long term- In progress
• Tidal marsh creation in upper Bay- Long term- Planning phase
Three Beneficial Use Opportunities
BUILDING STRONG®
• Old borrow source for creation of Brookley Air Field
• Baseline surveys reveal hypoxic conditions resulting in degraded ecological productivity
• 1.2 MCY of initial fill from upper Mobile Bay Channel
• Fill Options- Fill to some level of productivity- Fill to surrounding grade through
successive dredging cycles- Combination of emergent feature w/
marsh vegetation grading into shallow submerged environment
• Leveraging other research programs- Conducted baseline characterizations- Continued post-fill monitoring
• Monitoring results will be used to determine desired level of restoration
BU of Dredged Material to Fill Borrow Pit (Brookley Hole) – In progress
BUILDING STRONG®
Open Bay Disposal in Upper Mobile Bay (In progress)
Northern limit of pipeline dredging
Southern limit of pipeline dredging
Old Hollingers Island Channel
•Hopper dredges not able to keep up with shoaling rates in upper Bay channel
•Critical need to return channel to full operational dimensions
•Utilize hydraulic cutterhead dredges
- 9 MCY dredged from channel
•Thin-layer disposal techniques
•Using pre-established historical disposal areas
•Partnering with other programs to conduct monitoring and modeling
•Significant savings in dredging costs
BUILDING STRONG®
Potential Long Term Beneficial Use Sites in Upper Mobile Bay
12
High Priority
1,200 Acres
Medium Priority
780 Acres
Low Priority
700 Acres
BU sites as refined and prioritized from the April 12 Meeting
Establishment of Long Term BU Site in Upper Mobile Bay
• Engagement of Interagency Working Group to help plan and implement semi-contained, large scale open water disposal area in upper Mobile Bay
• BU opportunities associated with navigation activities in Mobile Bay
• Builds on requests of Alabama State Port Authority (ASPA) to partner in implementation of more effective sediment management associated with maintaining Mobile Harbor
• Leverage various funding sources
• Develop feasibility level BU design
• ASPA will take lead on the final design, NEPA coordination, and permitting actions.
BUILDING STRONG®
• Establishment of IWG• Emphasize connection between maintenance dredging requirements, beneficial uses, and sediment management methods that reduce dredging costs
• Integration of the regulatory, planning, engineering, and operational processes
• Reducing amount of sediment disposal in the ODMDS• Return sediment into natural system• Establish long-term beneficial use site in upper Mobile Bay• Implementation of environmental restoration alternatives
Benefits to Navigation Program and Environment