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Session 5: Dredging in sensitve areas

Date: 2 Oct 2008Time: 10:50 – 11:10Author: Jeroen Gheysens

CEDA dredging days – October 2008

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Overview• Main project information

• Dredging in sensitive areas

• Environmental monitoring

• Dredging of contaminated materials

• Reclamation area layout

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BRAZIL

SEPETIBA BAYReclamation Area

Dredging Area

Geographical Location

SÃO PAULO

RIO DE JANEIRO

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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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DREDGING AREA

RECLAMATION

AREA

• Access Channel– Length 4,3km– Bottom width 128m– Dredging depth -14,5m CD– Volume 6.600.000 m³

• Harbour Basin– Turning circle 250m– Dredging depth -14,5m CD– Volume 4.500.000 m³

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• Large Cutter Suction Dredger (CSD)– Vlaanderen XIX: 8.358 kW

• Boosters– Cosel: 5.500 kW– DI 509: 4.475 kW– Nieuwe Merwede: 2.984 kW

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• Confined Disposal Facilities– CDF 1 135.000 m³– CDF 2 141.000 m³

• Contaminated Material– Volume 131.000 m³

• Capping Material– Volume 54.000 m³

Contaminated Areas

Capping Areas

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• Environmental CSD Beaver St. Lawrence– Cutter Power: 171 kW– Pump Power: 839 kW

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Overview• Main project information

• Dredging in sensitive areas

• Environmental monitoring

• Dredging of contaminated materials

• Reclamation area layout

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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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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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Overview• Main project information

• Dredging in sensitive areas

• Environmental monitoring

• Dredging of contaminated materials

• Reclamation area layout

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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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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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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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• Fixed points in the river São Francisco• TSS (mg/l) = 1,14 NTU

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Santa Cruz Piraí C10 C18 CONAMA Limit for Freshwater Baseline from S. Fransisco Rv

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precipitation C20 C30 C40 C50 Baseline from Sepetiba Bay

• Fixed points in the Sepetiba Bay• TSS (mg/l) = 2,74 NTU

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• Points around the dredger• TSS (mg/l) = 2,74 NTU

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precipitation D2N D2S D2W D2E D3N D3S D3W D3E

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Overview• Main project information

• Dredging in sensitive areas

• Environmental monitoring

• Dredging of contaminated materials

• Reclamation area layout

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• Confined Disposal Facilities– CDF 1 135.000 m³– CDF 2 141.000 m³

• Contaminated Material– Volume 131.000 m³

• Capping Material– Volume 54.000 m³

Contaminated Areas

Capping Areas

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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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Dredging of contaminated materials

Environmental Sweep Dredger vs Environmental Disc Cutter

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Overview• Main project information

• Dredging in sensitive areas

• Environmental monitoring

• Dredging of contaminated materials

• Reclamation area layout

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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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