1. Session 5: Dredging in sensitve areas
CEDA dredging days – October 2008
Session 5: Dredging in sensitve areas
Date: 2 Oct 2008
Time: 10:50 – 11:10
Author: Jeroen Gheysens
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2. Overview Main project information Dredging in sensitive areas
Environmental monitoring
Dredging of contaminated materials
Reclamation area layout
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3. Geographical Location
SÃO PAULO
RIO DE JANEIRO
BRAZIL
Reclamation Area
Dredging Area
SEPETIBA BAY
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4. General Info on Project
CLIENT:
ThyssenKrupp CSA Companhia Siderúrgica
CONTRACTOR:
Consorcium Dredging International nv – Boskalis International bv
EXECUTION PERIOD
September 2006 – April 2008
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5. Access Channel Harbour Basin Length 4,3km Bottom width 128m
RECLAMATION
AREA
Access Channel
Length 4,3km
Bottom width 128m
Dredging depth -14,5m CD
Volume m³
Harbour Basin
Turning circle 250m
Volume m³
DREDGING AREA
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6. Large Cutter Suction Dredger (CSD)
Boosters
Cosel: kW
DI 509: kW
Nieuwe Merwede: kW
Large Cutter Suction Dredger (CSD)
Vlaanderen XIX: kW
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7. Confined Disposal Facilities
CDF m³
CDF m³
Contaminated Material
Volume m³
Capping Material
Volume m³
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8. Environmental CSD Beaver St. Lawrence
Cutter Power: 171 kW
Pump Power: 839 kW
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9. Overview Main project information Dredging in sensitive areas
Environmental monitoring
Dredging of contaminated materials
Reclamation area layout
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10. Dredging in sensitive areas
Sepetiba Bay: historical contamination, mainly heavy metals – Mangroves - Fishery
Environmental effects
Spreading and settlement of resuspended solids
Impact on soil organisms during operation
Alteration of bathymetry
Changing shoreline configuration
MINIMISE THE ENVIRONMENTAL EFFECTS!
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11. Dredging in sensitive areas
Minimise the environmental effects
Understand the environmental situation and identify the most sensitive areas
Selection of dredging equipment
Identification of environmental impacts
Selecting the most appropriate working method
Well trained, experienced and environmental aware crew
Environmental management and monitoring plan
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12. Overview Main project information Dredging in sensitive areas
Environmental monitoring
Dredging of contaminated materials
Reclamation area layout
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13. Environmental Monitoring
Water quality monitoring
Suspended solids dewatering < 500mg/l
Capping of CDF’s
Capping layer of 1m with ‘no contamination’
Noise level monitoring
< 65dB (background level)
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14. Environmental Monitoring
Baseline monitoring
Identification of the situation before the start of the works
Relationship turbidity – suspended solids
Background monitoring
Weekly basis (background locations)
Identify turbidity from other sources
River discharges
Heavy rainfall
Seasonal fluctuations
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15. Environmental Monitoring
Water quality monitoring
Daily measurements at fixed locations
Turbidity (~ Suspended Solids)
Water temperature
Salinity
Instrument Depth
DREDGING AREA
RECLAMATION
AREA
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16. Fixed points in the river São Francisco TSS (mg/l) = 1,14 NTU
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17. Fixed points in the Sepetiba Bay TSS (mg/l) = 2,74 NTU
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18. Points around the dredger TSS (mg/l) = 2,74 NTU
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19. Overview Main project information Dredging in sensitive areas
Environmental monitoring
Dredging of contaminated materials
Reclamation area layout
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20. Confined Disposal Facilities
CDF m³
CDF m³
Contaminated Material
Volume m³
Capping Material
Volume m³
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21. Dredging of contaminated materials
Minimise spillage, turbidity and turbulence
Minimise storage by high concentration dredging
Minimise noise and unpleasant smells
Optimise precision for accurate and selective thin layer dredging
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22. Dredging of contaminated materials
Environmental Sweep Dredger vs Environmental Disc Cutter
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23. Overview Main project information Dredging in sensitive areas
Environmental monitoring
Dredging of contaminated materials
Reclamation area layout
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24. Reclamation area layout
Mangroves (high environmental sensitive area)
Protect from salt water of the dredging process
Risk of bund wall failures (Monitoring!)
Reduce suspended solids dewatering
Maximise travel distance of water on the area
Weir boxes (managing water levels on the area)
Monitoring!
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