ANNA PRZYBORSKA, M. MUZYKA, J. ANDRZEJEWSKI, J. … · 2020-05-03 · the spreading of suspended...

THE SPREADING OF SUSPENDED MATTER FORMED DURING

CONSTRUCTION WORKS OF OFFSHORE WIND FARMS

ANNA PRZYBORSKA , M. MUZYKA , J . ANDRZEJEWSKI , J . JAKACKI , D. RAK

I N S T I T U T E O F O C EA N O LO GY P O L I S H A C A DE M Y O F S C I E N C ES

O C E A N A N D AT M O S P H E R E N U M E R I C A L M O D E L L I N G L A B O R ATO R Y

Anna Przyborska et al. , aniast@iopan.gda.pl

Scheme of an offshore wind farm and typical connection infrastructure

wind turbines

Onshoretransformer station

internal cables export cables

Offshoretransformer station

Source:

Anna Przyborska et al. , aniast@iopan.gda.pl THE SPREADING OF SUSPENDED MATTER FORMED DURING CONSTRUCTION WORKS OF OFFSHORE WIND FARMS

Study area

Location of the study area (green polygon), model domain and bathymetry

The analyzed investment is located inthe central part of the South BalticSea, at the foot of the northern slopesof the Słupsk Bank, about 55 km fromthe shoreline opposite the Ustkacommune.

Geologically the sea bed in the windmill area consists of layers gravel-stonebottom with sandy ribbons

Technical parameters km2

Area of the offshore wind farm 41,3

Area of the buffer zone 13,6

Area occupied by the wind farm 27,7

Anna Przyborska et al. , aniast@iopan.gda.pl THE SPREADING OF SUSPENDED MATTER FORMED DURING CONSTRUCTION WORKS OF OFFSHORE WIND FARMS

Location of the study area (green polygon), model domain and bathymetry

Materials and methods• model has been built based on

MIKE, tools supplied by DHI andWRF,

• all the implemented modelscover the entire Baltic Sea

• the Baltic bathymetry comesfrom NavSim,

• the MIKE model is based onflexible mesh, which allows highspatial resolution in theinteresting area. The verticalresolution is the sigma coordinatesystem, a coordinate system usedin computational models foroceanography, witch 25 sigmalayers.

Anna Przyborska et al. , aniast@iopan.gda.pl THE SPREADING OF SUSPENDED MATTER FORMED DURING CONSTRUCTION WORKS OF OFFSHORE WIND FARMS

Materials and methods:

The Baltic Sea coupled model diagram

• the main part of the couple modelis the Hydrodynamic Model - MikeFlow Model for simulation ofcurrents, water levels, salinity andwater temperature,

• the hydrodynamic models requirethe atmospheric data provided bythe forecasting model (WRF) andthe other data provided by theSpectral Wave Model (SW),

• the MIKE 21/3 Coupled Model FMincludes a dynamic couplingbetween the Mud TransportModule (MT) and the SandTransport Module (ST).

MIKE 21/3 Couple Model FM by DHI

MIKE 3 HDMIKE 21 SW

MIKE ST i MT

WRF

Anna Przyborska et al. , aniast@iopan.gda.pl THE SPREADING OF SUSPENDED MATTER FORMED DURING CONSTRUCTION WORKS OF OFFSHORE WIND FARMS

Results:

Suspended sediment concentration 24, 30, 36 and 42h after starting dreading work starting dreading work (for one wind farm)

)

t=24h t=30h

t=36h t=42h

Anna Przyborska et al. , aniast@iopan.gda.pl THE SPREADING OF SUSPENDED MATTER FORMED DURING CONSTRUCTION WORKS OF OFFSHORE WIND FARMS

Results:

Possible change of suspended sediment concentration during 24h-120h for case working on more than one wind turbine (cumulative case)

t=96h t=120h

t=72ht=24h

THE SPREADING OF SUSPENDED MATTER FORMED DURING CONSTRUCTION WORKS OF OFFSHORE WIND FARMS

Distribution of the maximum concentration of suspended sediment

FOR ONE WIND FARM CUMULATIVE CASE

THE SPREADING OF SUSPENDED MATTER FORMED DURING CONSTRUCTION WORKS OF OFFSHORE WIND FARMS

Deposit of sediments during construction work

FOR ONE WIND FARM CUMULATIVE CASE

Anna Przyborska et al. , aniast@iopan.gda.pl

Final remarks:

• Impact of dredging works on the spreading of suspended matter resulting from construction of the Offshore Wind will depend primarily on the type of foundation and on the scope of dredging and installation works carried out at the same time,

• Suspended sediment from dredging activities related to the construction of one turbine will remain at a level of more than 10 mg/l for maximum 42 hours,

• The range of the suspended sediment will not exceed 15 km.

• Bottom level change due to dredging is negligible, maximum values (less than 1 mm) will be at the locations of the dredging works and will decrease with the distance from the farm

• Cumulative impacts significantly increase the concentration of suspended sediment and the impact area. To avoid cumulative impacts, the works should not be carried out at distances closer than 2 km