dredging, disposal management and impacts on lake sediments us army corps of engineers
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Dredging, Disposal Management and Impacts on Lake SedimentsUS Army Corps
of Engineers
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Great Lakes HarborsUS Army Corpsof Engineers
• Corps maintains 139 channels and harbors (total harbors on the Great Lakes is over 200)– 68 commercial harbors
• Represents 24% of Nation’s commercial harbors
– 71 recreation harbors• Represents 12% of Nation’s recreation harbors• About 700,000 recreation vessels traverse the lakes annually
Duluth Harbor, MNCommercial
Arcadia, MIRecreation
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Operation & Maintenance BudgetUS Army Corpsof Engineers
• Annual budget to operate and maintain Corps navigation projects on the Great Lakes ranges from $82M to $89M– Includes surveys, dredging, structure and lock maintenance
• Cost to dredge Corps projects ranges from $16M to $24M annually, with an average of $20M– Federal yardage dredged is 3.5 - 4.0 million cubic yards
– Including non-Federal harbors yardage is 5 - 6 million cubic yards
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Great Lakes DredgingUS Army Corpsof Engineers
• Corps dredges 26 - 41 projects annually– Average is about 35 for deep and shallow draft harbors
– Average 9 recreation harbors
• In FY 2000 Corps dredged 41 projects– 25 were commercial and 16 recreation
• In FY 2001 Corps estimates 40 projects will be dredged– 24 are commercial and 16 recreation
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US Army Corpsof Engineers
• Did the low lake levels in 1999 & 2000 change the way the Corps dredges within the Great Lakes?– No
– Projects are dredged to depths to meet user needs, up to authorized depths below low water datum (LWD)
• LWD establishes the depth to which projects are maintained
• Harbors dredged to project depth whether lake levels are high or low
• Some channels maintained to less than authorized depth
• Projects are dredged based on shoaling rates and commercial importance (priority) of the project
• High lake levels allow dredging at recreation harbors to be deferred
Dredging (con’t)
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US Army Corpsof Engineers
• Commercial navigation industry was impacted by low lake levels in 1999 and 2000– Industry was used to above average lake levels
• One inch loss in draft equates to a loss of 270 tons of cargo carrying capacity for a 1000-foot vessel
• In general, lake levels do not impact dredging– Some impact at tributaries entering the lake
• Sediments drop out quicker with lower lake levels
• Corps now has authority to dredge deeper– Section 343, WRDA 2000, allows Corps to dredge to
provide authorized depths when lake levels go below LWD
Dredging (con’t)
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US Army Corpsof Engineers
• Did the Corps dredge all harbors which had shoaling problems in 2000?– Funding constraints prevented dredging at some
recreation harbors
• Previous high lake levels masked the issue of a lack of funding for all needed dredging
• Some harbors have issues preventing dredging– Lack of a disposal site
– Other environmental issues
Dredging (con’t)
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US Army Corpsof Engineers
• If low lake levels continue in FY 2001, what impact will this have on the way the Corps dredges?– Commercial harbors will receive highest priority
– Funding constraints will impact some recreation harbors• The Corps will dredge as many harbors as funding allows
– In FY 2000 the Corps dredged more harbors than it had originally scheduled due to dropping lake levels
Dredging (con’t)
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Confined Disposal FacilitiesUS Army Corpsof Engineers
• Disposal of dredged material used to be unconfined and placed in the open water– Least cost alternative
• Lake water quality degradation dictated alternative disposal methods be investigated
• Public Law 91-611 provided funds to construct CDFs– First CDF constructed in early 1970s
• 44 CDFs constructed on the Great Lakes• Current disposal methods include open water, beach
nourishment, or a CDF
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Dredging and Its PlacementUS Army Corpsof Engineers
• Quantity dredged averages 3.6 M CY of sediments
• Cost to dredge averages $20 M annually
• About a 50 - 50 split between confinement and open lake disposal, but recent trend is towards more confinement
– Confined disposal accounts for 55 percent of material– Open lake disposal or beach nourishment accounts for 45 percent of material Pt. Mouillee
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Great Lakes Dredged Material Testing & Evaluation Manual
• Regional guidance developed by USEPA
and Corps• Applicable to dredged material discharges
to Great Lakes, connecting channels, and
tributaries
• Tiered testing approach consistent with national
guidance, but using regionally chosen methods• Available online:
www.epa.gov/glnpo/sediment/gltem
US Army Corpsof Engineers
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Confined Disposal FacilitiesUS Army Corpsof Engineers
• Existing CDFs won’t last forever– Slightly less than half are filled or inactive
• Corps is assessing each project’s disposal needs– Dredged Material Management Plans developed to
assess disposal needs over a 20 year period
• All new CDFs require cost sharing with a sponsor– WRDA 1996 establishes cost sharing requirements
• Non-federal cost linked to project depth requirements– Approximately from 10 to 50 percent of total cost
• Allows for private disposal facilities
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Disposal ManagementUS Army Corpsof Engineers
• What can be done to extend the useful life of existing containment facilities?– Better consolidation of dredged material
• Use of ditches to drain water
– Beneficial re-use of dredged material• Beach & near-shore nourishment
• Mining and treatment of material for some productive use– habitat restoration, landscaping, road construction fill, agricultural
soils, strip mine restoration, or temporary cover for landfills
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Disposal Management (con’t)US Army Corpsof Engineers
• Beneficial use of dredged material offers a sustainable long-term management option for dredged material
• Regulatory and public perception issues are major obstacles to beneficial use– State regulations lack a coordinated regulatory approach
to beneficial use
– Better communicate pertinent information to the public
– Institutionalize the concept that dredged material is a valuable resource
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Disposal Management (con’t)US Army Corpsof Engineers
• The Corps is dredging the same quantity of sediments while the quality of it is improving– Sources of pollutants becoming less
• Dredging reduces pollutants within channels
• Requirement for confining dredged sediments will continue in the future– The Public and State agencies will require it
• Requirements for dredged material management will increase rather than decrease in the future– Trend is to confine more dredged material
– Unused capacity of CDFs is diminishing
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Cooperative EffortsUS Army Corpsof Engineers
• Corps is working with the USEPA and State / local agencies to clean up toxic harbor sediments
• Examples– Ashtabula Harbor
– Indiana Harbor
– Waukegan Harbor
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Impacts on Lake SedimentsUS Army Corpsof Engineers
• Effect of lower lake levels and vessel traffic – Vessels closer to channel bottom
• Prop wash aggravates sediments
• Suspends toxic materials within the water column
• Effect of lower lake levels on tributaries– More scour occurs near the mouth of a tributary
• Causes more sediments / toxic materials to enter lake
• Sediments more mobile with low lake level conditions
• No studies which quantify the effect between low lake levels and toxic sediments– Conceptual efforts and cannot quantify numbers / impacts
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Dredging, Disposal Management and Impacts on Lake SedimentsUS Army Corps
of Engineers
Questions ?