Dredging, Disposal Management and Impacts on Lake Sediments US Army Corps of Engineers.
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Dredging, Disposal Management and Impacts on Lake Sediments US Army Corps of Engineers
Great Lakes Harbors US Army Corps of 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, MN Commercial Arcadia, MI Recreation
Operation & Maintenance Budget US Army Corps of 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
Great Lakes Dredging US Army Corps of 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
US Army Corps of 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)
US Army Corps of 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)
US Army Corps of 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)
US Army Corps of 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)
Confined Disposal Facilities US Army Corps of 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
Dredging and Its Placement US Army Corps of 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
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 Corps of Engineers
Confined Disposal Facilities US Army Corps of 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
Disposal Management US Army Corps of 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
Disposal Management (con’t) US Army Corps of 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
Disposal Management (con’t) US Army Corps of 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
Cooperative Efforts US Army Corps of Engineers Corps is working with the USEPA and State / local agencies to clean up toxic harbor sediments Examples –Ashtabula Harbor –Indiana Harbor –Waukegan Harbor
Impacts on Lake Sediments US Army Corps of 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
Dredging, Disposal Management and Impacts on Lake Sediments US Army Corps of Engineers Questions ?
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