East Anglia ONE Offshore Windfarm - National Infrastructure Planning

East Anglia ONE 

Offshore Windfarm 

Environmental Impact Assessment (EIA) 

Scoping Report 

Supplementary Information on Connection 

to the Onshore Electricity Transmission Network 

www.eastangliawind.com 

Kentish Flats Offshore Windfarm © Vattenfall AB

1 SUPPLEMENTARY INFORMATION IN RELATION TO THE 

CONNECTION OF EAST ANGLIA ONE TO THE ONSHORE ELECTRICITY 

TRANSMISSION NETWORK 

This document provides an indicative description of the associated 

development required to connect the proposed East Anglia ONE Offshore 

Wind Farm to the onshore electricity transmission network and considers the 

possible effects of this on the environment. 

It has been prepared in support of East Anglia Offshore Wind‟s (EAOW) 

request for an Environmental Impact Assessment (EIA) scoping opinion for 

the East Anglia ONE Offshore Wind Farm project. 

The purpose of this document is to provide indicative information on: 

The proposed connection location. 

The possible route (within a broad corridor) for the infrastructure 

required to connect East Anglia ONE to this location. 

An indication of the infrastructure required. 

The potential environmental effects. 

Following further study of the connection options, EAOW intends to make a 

further scoping request, in relation to this associated development, to the 

Infrastructure Planning Commission (IPC) under Regulation 8 of the EIA 

Regulations. 

In this document, „associated development‟ refers to the transmission 

infrastructure for East Anglia ONE Offshore Wind Farm, including on- or 

offshore substations/converter stations and on- and offshore cabling (export 

cables) / high voltage (HV) wires to connect the project to the national HV 

infrastructure. 

1 

EAST ANGLIA OFFHSORE WIND EAST ANGLIA ONE – SUPPLEMENTARY SCOPING INFORMATION

1.1 PROPOSED CONNECTION LOCATION 

EAOW has received a grid connection offer from National Grid which 

identifies that East Anglia ONE will be connected at Bramford Substation, 

Suffolk. 

1.2 CONNECTION ROUTE 

At this early stage, specific connection route(s) have not been identified. 

Figure FI1 shows the broad corridor within which East Anglia ONE could 

connect. This corridor has been identified following an initial desk top review 

of environmental and technical constraints, and in consultation with district 

and county councils. Strategic engineering and environmental studies will be 

undertaken within this corridor to identify the most appropriate route(s) for 

connection. Once a narrower connection corridor / potential connection 

routes have been identified, it is intended that a further scoping request will 

be made in relation to this. 

During the process of establishing cable routing options, the following 

documents will be referenced: 

1.3 CONNECTION INFRASTRUCTURE 

The Holford Rules: Guidelines for the Routing of New High 

Voltage Overhead Transmission Line with NGC1992 and 

SHETL2003 Notes. 

Parson Brinkerhoff (2009) Cavan-Tyrone and Meath-Cavan 400 kV 

Transmission Circuits – Comparison of High Voltage Transmission 

Options: Alternating Current Overhead and Underground, and 

Direct Underground. Report to Northern Ireland Electricity and 

EIR Grid. 

The required connection infrastructure, which will be sited within the broad 

corridor identified on Figure FI1, is expected to comprise: 

Alternating Current (AC)/ Direct Current (DC) converter station or 

AC substation local to the offshore windfarm, collecting power 

from up to four local substations located within the offshore wind 

farm. 

Cables from this converter station / substation local to the wind 

farm to a DC/AC converter or AC substation on the mainland 

(location to be determined). 

DC/AC converter station or AC substation (on the mainland) in 

proximity to the connection point to the national transmission 

system. 

Connection from the DC/AC converter station or AC substation on 

the mainland to the national transmission system (only required if 

the onshore converter station is not located adjacent to the national 

transmission system connection point). 

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1.3.1 EXPORT CABLING BETWEEN OFFSHORE SUBSTATIONS WITHIN THE WIND FARM 

AND AC /DC CONVERTER STATION(S) OR AC SUBSTATIONS LOCAL TO THE WIND 

FARM 

The higher voltage power from the local substations within the wind farm 

would be transferred to the converter station / substation local to the wind 

farm via subsea cables. Export cabling may require cable or pipeline 

crossings. 

1.3.2 AC /DC CONVERTER STATION OR AC SUBSTATION LOCAL TO THE WIND FARM 

A converter station located within the East Anglia ONE development site 

could be used to transform the electricity from AC to DC. Alternatively, an AC 

system with a collector substation may be deployed. 

The final choice of whether to use an AC or DC system would depend on a 

review of electrical, commercial and environmental factors. 

Any offshore substations and offshore converter station would have helicopter 

landing platforms as well as access from the sea. The substation / converter 

station would sit on top of a foundation. Foundation types would be as for 

the turbines (as described in Section 3.5.4 of the scoping document for the 

offshore elements of the project (July 2010)). 

1.3.3 EXPORT WIRES/CABLES FROM THE AC/DC CONVERTER STATION LOCAL TO THE 

WIND FARM TO A DC/AC CONVERTER STATION ON THE MAINLAND. 

Power will flow from the project to the mainland via high voltage direct 

current (HVDC) or AC circuits. It is anticipated that the majority, if not all, of 

this circuit will be subsea or underground. A route has not yet been identified 

but will be within the broad corridor shown on Figure FI1, following 

consultation and a review of technical, environmental and commercial 

constraints. 

Depending on seabed conditions, subsea cabling would be buried (by 

ploughing or jetting), covered with rocks or concrete mattresses, or pinned to 

the seabed. 

Onshore sections would be installed using excavators. Horizontal Directional 

Drilling (HDD) could be used in locations where there are sensitive surface 

features. 

The precise number and routing of cables will be designed to minimise 

environmental impact and to optimise the electrical losses, cost of the cables, 

cost of installation and the redundancy offered when a failure occurs. 

3 


1.3.4 DC/AC CONVERTER STATION (ON THE MAINLAND) IN PROXIMITY TO THE 

CONNECTION POINT TO THE NATIONAL TRANSMISSION SYSTEM. 

An onshore converter station would measure approximately 100m x 50m x 

25m high. The height of the station would be determined by the electrical 

components within the building; it is expected that a short section of the 

station would be at a height of 25m to accommodate large electrical 

equipment, with the rest of the building at a lower level. 

1.4 POTENTIAL ENVIRONMENTAL EFFECTS 

1.4.1 Baseline Environmental Conditions 

Figure FI2 identifies the broad cable corridor within which the required 

infrastructure would be sited. 

Key European environmental designations within this corridor are 

summarised below. 

Offshore 

The corridor covers a section of the Outer Thames Special 

Protection Area (SPA), designated for wintering red-throated 

divers. 

Inshore and intertidal area 

Three estuaries within the broad cable corridor are designated for 

their ornithological importance: 

a. Stour and Orwell Estuaries SPA / Ramsar: designated for 

supporting a large number of overwintering Annex 1 

species 

b. Deben Estuary SPA / Ramsar: designated for supporting 

over 1% of the UK wintering population of Brent Goose and 

0.8% of the wintering population of Avocet. 

The broad corridor also includes the: 

c. Hamford Water SPA, designated for its internationally 

important numbers of waterbirds during the passage and 

winter periods, as well as for breeding terns in summer. 

d. Sandlings SPA, designated for its bird communities of 

conservation value including woodlark and nightjar. 

Key activities for consideration include maintenance dredging of the Orwell 

and Stour, and the presence of commercial and recreational vessels. 

Onshore, the area highlighted is dominated by the town of Ipswich which is 

surrounded by smaller settlements and arable farmland. The broad cable 

corridor includes a network of roads and railway routes. 

The main settlements in the broad cable corridor are Ipswich, and the ports of 

Harwich and Felixstowe. Ipswich is a town with a population of just over 

4 


117,000. Port of Felixstowe is the largest container port in the UK and one of 

the largest in Europe. The area is crossed by several major roads serving 

Ipswich and the ports. 

The Suffolk Landscape Typology describes the countryside between Ipswich 

and the coast as primarily a rich agricultural landscape of estate farmlands 

(Ancient estate farmlands, Rolling estate farmlands, Plateau estate farmlands, 

Estate sandlands and Rolling estate sandlands) intersected by Coastal levels, 

Saltmarsh and Intertidal flats. 

1.5 POTENTIAL ENVIRONMENTAL EFFECTS 

The potential environmental effects of the proposed infrastructure are 

summarised below. 

It must be noted that there is presently a considerable level of uncertainty 

regarding the precise nature of the connection infrastructure required for East 

Anglia ONE. Detailed routeing studies are proposed and preferred routeing 

options will be discussed with the relevant authorities at an early stage. A 

Scoping Document will then be provided giving more specific baseline 

information, identifying the surveys required, and describing the potential 

environmental effects to be assessed within the Environmental Impact 

Assessment. 

At this initial stage, the following caveats therefore apply. 

1: The baseline information given in this document is extremely high level. 

2: Discussions with consultees will be required after the submission of this 

document in order to define the geographical extent and intensity of primary 

data collection. This information will be presented in detail in a subsequent 

scoping request. 

3: Ultimately, the identification, and modelling, of potential environmental 

effects will be based on a “Rochdale Envelope” approach with regard to the 

size, location and layout of project infrastructure, and the construction, 

operation and decommissioning methodologies. Generic effects only are 

therefore identified at this time. 

4: The environmental effects identified in this document assume that the 

onshore export cable infrastructure will be undergrounded. 

Potential Physical Environmental Effects 

Suspended Sediments 

� Increased suspended sediment levels during construction and 

decommissioning of offshore infrastructure. 

5 


� Change in seabed morphology during construction and 

decommissioning of offshore infrastructure. This could include 

physical disturbance to sedimentary structures and bedforms, 

solid geology or geomorphological features. 

� Changes in sediment processes during operation and 

decommissioning of offshore infrastructure. This could include 

modifications to sediment transport pathways in the immediate 

vicinity of operating devices, and sediment accretion or erosion 

(scour). 

� Damage to geological features in the footprint of offshore 

infrastructure during construction and decommissioning. 

� Scour around offshore infrastructure and, for cables, the 

resulting potential for the development of “free-spans”. 

Water Quality 


� Release of contaminants during construction, operation and 

decommissioning from various activities including cable burial, 

grouting, drilling, and vessel movements. Contaminants may 

also be released during the operational phase as a result of 

erosion of sacrificial anodes or release of anti-fouling 

compounds. 

� Accidental release of contaminants during construction, 

operation and decommissioning. Contaminants may include 

fuel and lubricating oils, cleaning fluids, paints, specialised 

chemicals and litter. 

� Disturbance of existing contaminants in the marine environment 

during construction, operation and decommissioning. 

Onshore 

� Disturbance of watercourses during construction of onshore 

converter stations or cable laying. 

� Accidental pollution of watercourses during construction and 

decommissioning/removal of onshore converter stations or 

cables. 

� Disturbance of terrestrial contaminants during construction of 

onshore converter stations or cable laying. 

Potential Biological Environmental Effects 

Habitats and Flora and Fauna 


� Direct habitat loss associated with cable laying and the 

construction of foundations for converter station. 

� Addition of new habitat from the construction of offshore 

converter station (although this may differ from existing habitat). 

� Secondary habitat disturbance due to sediment re-suspension 

and deposition leading to increased turbidity and smothering of 

fauna. 

6 


� Decrease in flow velocities due to the presence of offshore 

converter station substructure acting as an impediment to wave 

loads. 

� Noise effects associated with construction of offshore cables or 

converter station. 

� Electromagnetic field (EMF) effects during operation of export 

cables and convertor station. 

� Permanent physical loss of terrestrial habitats and species in the 

footprint of any onshore cables or converter station. 

� Temporary disturbance of terrestrial habitats and species during 

construction of onshore cables or converter station. 

Marine Mammals 

Birds 

Fish 

� Noise effects associated with construction of offshore cables or 

converter station. Temporary disturbance associated with 

construction may lead to longer-term displacement. 

� Increased collision risk from vessel traffic associated with 

construction and maintenance of offshore cabling or converter 

station. 

� Accidental release of contaminants, such as hydraulic oil, from 

vessels associated with the construction, maintenance and 

decommissioning of offshore cabling or converter. 

� Entanglement associated with laying of export cables. Due to 

their rigid nature, cables are unlikely to pose a major threat of 

entanglement, but they may be difficult to detect given their 

small cross-sectional area. 


cables and convertor station. 

� Impacts on prey species during construction, operation and 

decommissioning of any offshore cabling or converter station. 

Offshore and onshore 

� Habitat loss due to disturbance during construction and 

decommissioning of onshore or offshore converter stations and 

export cable laying. 

� Habitat loss during operation due to presence of onshore or 

offshore converter stations. 

� Direct disturbance during construction, maintenance and 

decommissioning of offshore cabling or converter station. 

� Noise and vibration disturbance due to construction, 

maintenance and decommissioning of offshore cabling or 

converter station. Studies have suggested that demersal 

spawning activity, by hearing specialist species such as herring, 

can be disrupted (and eggs damaged) through the noise and 

vibration effects associated with the construction of offshore 

wind farms. The significance of this effect would be dependent 

upon the foundation type used for the converter station and the 

method of its construction. 

7 


� Direct habitat loss associated with cable laying and the 

construction of the foundations for the converter station. 

� Secondary habitat disturbance due to sediment re-suspension 

and deposition due to construction and decommissioning of any 

offshore converter station and/or export cable laying activities. 

Suspended sediments generated through the construction 

activities have the potential to impair respiratory or reproductive 

functions, or disrupt migration/spawning activity in sensitive 

species of both fish and crustacea. 


cables and convertor station. The issues relating to the effects of 

EMF (generated by the cables) upon the movement and 

behaviour of sensitive species are still being researched. The 

major group of organisms that are known to be electroreceptive 

are elasmobranchs (sharks, skates and rays). 

� Collision risk presented by the increase in equipment and vessels 

required during construction and decommissioning, and 

potential effects on shoaling behaviour of pelagic species due to 

the presence of the converter station during operation. 

� Increase in habitat heterogeneity due to the potential artificial 

reef effects of the converter station during operation. 

Potential Human Environmental Effects 

Commercial Fishing 

� Loss of or restricted access to fishing grounds during the 

construction, maintenance, operation and decommissioning of 

offshore converter station and / or export cable laying. 

� Increased steaming time to port during the construction, 

maintenance, operation and decommissioning of offshore 

converter station and / or export cable laying. 

� Increased conflict over diminished grounds. Exclusion from one 

fishing area may increase fishing activity in other existing fishing 

grounds, thus increasing the intensity of effort in particular 

areas. 

� Impacts on fish and shellfish resources during construction, 

operation, maintenance and decommissioning of offshore 

converter station and cable laying. 

� Loss or damage to gear during construction, operation, 

maintenance or decommissioning of any offshore converter 

station or cabling. The cables and foundations could act as 

seabed obstacles which could pose a hazard to vessels or gear. 

Navigation 

� Temporary disturbance to regular shipping traffic during 

construction and decommissioning of offshore cabling or 


� Increased navigational and collision risk during construction, 

maintenance and decommissioning of offshore cabling or 

converter station due to increased numbers of vessels in area, 

8 


increased risk of pollution events and presence of new physical 

objects. 

Landscape and Visual 


� Change to landscape/seascape character during the construction, 

operation and decommissioning of any onshore converter station 

and cable laying. 

Onshore 

� Change to visual effects (views and visual amenity) during 

construction, operation and decommissioning of any onshore 

converter station and cable laying. 

Archaeology 


� Disturbance and destruction of known and unknown wrecks 

during construction and maintenance of any offshore converter 

station or cabling. 

� Disturbance and destruction of known and unknown 

archaeological submarine sites and artefacts during construction 

and maintenance of offshore converter station or cabling. 

Onshore 

� Disturbance and destruction of known and unknown 

archaeological terrestrial sites and artefacts during construction 

and maintenance of any onshore converter station or cabling. 

� Influence to cultural setting of nearby known archaeological 

terrestrial sites and artefacts during operation of any onshore 


Noise 


� Noise generated from traffic during the construction, 

maintenance and decommissioning of offshore converter station 

or cabling. Noise sources are likely to include foundation 

installation activity, vessel movements (or helicopter movements 

in cases of poor weather), foundation removal activity. 

Onshore 

� Noise generated from traffic (including heavy plant) during the 

construction, maintenance and decommissioning of any onshore 

converter station or cabling. Construction noise will be subject to 

controls set by the Local Authority. 

Tourism and Recreation 

Offshore and Onshore 

� Temporary disruption to recreational activity during 

construction/decommissioning of offshore or onshore converter 

station or cabling. 

9 


� Visual effects on landscape/seascape during operation of any 

offshore or onshore converter station could potentially deter 

tourism. 

Other Users 


� Disturbance during construction and decommissioning of 

existing munitions contamination in the marine environment. 

� Disturbance to dredging activity. 

Onshore 

� Temporary disruption to local traffic and access during 

construction and decommissioning of any onshore converter 

station/cabling. The duration and magnitude of effects will 

depend upon the methods by which construction materials and 

plant are transported to site, and on the necessity or otherwise of 

laying cables along roadside or railway verges. 

10 


52°30'0"N 

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Projection: U TM 31N 

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E ast Anglia O ne project area 

Indicative cable corridor area 

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") 400 kv substations 

Bramford 

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R ef: E AO W 1_CabCoAoI_v01_100928rs, Bram ford_GridSStn_v01_100813rs_O SN G, R ound_3_Zones_Iteration_III (N am e = N orfolk) 

1°20'0"E 

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3 14/09/10 R S Indicative cable corridor am ended (northern lim it). 

1°30'0"E 

CblCorr clipped to R .Stour to S and district bdry to W . Grid circuits 

21 07/09/10 13/08/10 R S and Indicative 400 kv substns cable corridor digitised to amreflect ended. 

1:50k O S 

A 28/09/10 R S F irst Issue 

Rev Date By Comment 

1°30'0"E 

O riginal A3 

Plot Scale 

1:350,000 

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0 2 4km 0 2 4nm 

© British Crown and SeaZone Solutions L im ited. Al rights reserved. Products L icence N o. 042010.006. This product 

has been derived in part from m aterial obtained from the U K Hydrographic O ffice with the perm ission of the Controler of 

Her M ajesty’s Stationery O ffice and the U K Hydrographic O ffice (www.ukho.gov.uk). N O T TO BE U SE D F O R N AVIGATIO N . 

© E ast Anglia O ffshore W ind L im ited 2010. Contains O rdnance Survey data © Crown copyright, Al rights reserved 2010. 

L icence num ber 0100049003. 

2°0'0"E 

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2°10'0"E 

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East Anglia Offshore Wind 

E ast Anglia O ne project area and indicative cable 

corridor 

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D rg N o 6115-700-PA-035 

R ev 

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E ast Anglia O ffshore W ind zone boundary 

Breckland District 

") 400 kv substation 

St. Edmundsbury District (B) 

D istrict boundary 

Mid Suffolk District 

Babergh District 

Colchester District (B) 

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Legend 

D atum : W GS84 

Projection: U TM 31N 

© E SR I 

E ast Anglia O ne project area 

Indicative cable corridor area 

1°0'0"E 

1°0'0"E 

Circuits connecting to 400 kv substations 

R AM SAR 

Special Area of Conservation (SAC) 

Candidate Special Area of Conservation (cS AC) 

Special Protection Area (SPA) 

Proposed Special P rotection Area (pS PA) 

County boundary 

Bramford 

Tendring District 

1°10'0"E 

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Suffolk Coastal District 

1°20'0"E 

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South Norfolk District 

Waveney District 

Outer Thames Estuary 

1°30'0"E 

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3 16/08/10 R S N orthern onshore extent of cable corridor area am ended. 

2 

16/08/10 R S 

A 28/09/10 R S F irst Issue 

Rev Date By Comment 

CblCorr brdy am ended to m atch O S district+county bdrys. Chart changed to 1408-0. 

Paralel line added btw Sizewel+Bram ford. CblCorr clipped to S bdry of W aveney D C bdry. 

Sizewell 

O riginal A3 

Plot Scale 

1:350,000 





R ef: E AO W 1_CabCoAoI_v01_100928rs, Sizewel_GridSStn_v01_100813rs_O SN G, N orfolk_GridSStn_v01_100813rs_O SN G, Bram ford_GridSStn_v01_100813rs_O SN G, GridL ines_N orfolk_v01_100813rs_O GN G, county_region, district_borough_unitary_region, cSAC_M arine, pSPA_O uterTham esE stuary_Z5v3, R AM SAR _E ngland_100923, SAC_E ngland_100923, SPA_E ngland_100923, R ound_3_Zones_Iteration_III (N am e = N orfolk) 

1°40'0"E 

1°40'0"E 

1°50'0"E 

1°50'0"E 

0 2 4km 0 2 4nm 

© British Crown and SeaZone Solutions L im ited. Al rights reserved. Products L icence N o. 042010.006. This product 

has been derived in part from m aterial obtained from the U K Hydrographic O ffice with the perm ission of the Controler of 

Her M ajesty’s Stationery O ffice and the U K Hydrographic O ffice (www.ukho.gov.uk). N O T TO BE U SE D F O R N AVIGATIO N . 

© E ast Anglia O ffshore W ind L im ited 2010. Contains O rdnance Survey data © Crown copyright, Al rights reserved 2010. 

L icence num ber 0100049003. © N atural E ngland. © J N CC. 

2°0'0"E 

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East Anglia Offshore Wind 

Indicative cable corridor 

International nature conservation designations 

2°30'0"E 

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R ev 

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A 

28/09/10 

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F 

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F igure 

F I 2 

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East Anglia ONE Offshore Windfarm - National Infrastructure Planning

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