Mid Suffolk District Council High Street, Needham Market, Ipswich, IP6 8DL Telephone: (01449) 724500 / Facsimile: (01449) 724627 www.midsuffolk.gov.uk Suffolk Coastal District Council Melton Hill, Woodbridge, Suffolk, IP12 1AU Telephone: (01394) 383789 / Facsimile: (01394) 385100 www.suffolkcoastal.gov.uk Ms. A Sidgwick SLR Consulting Limited BY EMAIL Please ask for: Mr. Elvin / Mr. Perkin Direct line: 01449 724935 / 01502 523073 Fax number: Your reference: Our reference: E-mail: Please reply to: 7 December 2016 Dear Ms Sidgwick The East Anglia ONE Offshore Wind Farm Order 2014 Requirement 29 (1) Installation of Cable Ducts I refer to your email dated 2 November 2016. Mid Suffolk District Council and Suffolk Coastal District Council hereby discharge Requirement 29 (1) (b) in accordance with East Anglia ONE Offshore Windfarm Cable Method Statement (Document reference EA1-CON-R-IBR-021238, dated 2 November 2016). Yours sincerely Michael Evans Strategic Director Babergh and Mid Suffolk District Councils Philip Ridley Head of Planning & Coastal Management Suffolk Coastal and Waveney District Councils CC Katherine Potts – Suffolk County Council
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Dear Ms Sidgwick The East Anglia ONE Offshore Wind Farm Order 2014 Requirement 29 (1) Installation of Cable Ducts I refer to your email dated 2 November 2016. Mid Suffolk District Council and Suffolk Coastal District Council hereby discharge Requirement 29 (1) (b) in accordance with East Anglia ONE Offshore Windfarm Cable Method Statement (Document reference EA1-CON-R-IBR-021238, dated 2 November 2016). Yours sincerely
Michael Evans Strategic Director Babergh and Mid Suffolk District Councils
Philip Ridley Head of Planning & Coastal Management Suffolk Coastal and Waveney District Councils
CC Katherine Potts – Suffolk County Council
www.scottishpowerrenewables.com
East Anglia ONE OffshoreWindfarm
Cable Method StatementDCO Requirement 29 (1) (b)Final for Approval
ID: EA1-CON-R-IBR-021238
Created by / date: IEC / 28 Oct 2016Checked by / date: RM / 02 Nov 2016Approved by / date: PS / 02 Nov 2016
East Anglia ONE Offshore Windfarm November, 2016
Cable Method Statement
East Anglia ONE – EA1-CON-R-IBR-021238 Page 2
REVISION CONTROL
Revision and Approvals
Rev Date Reason for Issue Originated by Checked by Approved by
0 20/06/2016 Initial Draft MO JK DH
1 01/08/2016 Interim for Consultation IEC MC PS
2 02/11/2016 Final For Approval IEC RM PS
East Anglia ONE Offshore Windfarm November, 2016
Cable Method Statement
East Anglia ONE – EA1-CON-R-IBR-021238 Page 3
Table of contents
Abbreviations 4
1 Introduction 5
1.1 Project Overview 5
1.2 Purpose and Scope 5
2 Construction Overview 6
2.1 Cable Route and Working Width 6
2.2 Specialist Techniques 6
2.3 Construction Consolidation Sites 7
2.4 Construction Zones 8
3 Construction Methodology 9
3.1 Site Preparation 9
3.2 Site Enabling Works 10
3.3 Open Trench Duct Installation 11
3.4 Trenchless Duct Installation 13
3.5 Cable Installation 15
3.6 Reinstatement 16
4 Programme 17
4.1 Overview 17
4.2 Site Enabling Works Programme 17
4.3 Cable Civils Works Programme 19
4.4 Trenchless Works Programme 19
4.5 Cable Installation Programme 20
4.6 Re-instatement 21
FiguresFigure 1 Typical Trench Layout for EA ONE
Figure 2 Typical Trench Layout for EA THREE
Figure 3 Typical Trenchless Layout for Category 1 HDD
AppendicesAppendix 1 Onshore Cable Route Overview
Appendix 2 Typical Construction Cross Sections
Appendix 3 Construction Zones Plans
East Anglia ONE Offshore Windfarm November, 2016
Cable Method Statement
East Anglia ONE – EA1-CON-R-IBR-021238 Page 4
AbbreviationsAC Alternating Current
CCS Construction Consolidation Site
CCT Consents Compliance Team
DC Direct Current
DCO Development Consent Order
EA Environment Agency
EIA Environmental Impact Assessment
EMS Environmental Management System
ES Environmental Statement
FID Final Investment Decision
GIS Geographical Information System
HDD Horizontal Directional Drill
HSE Health Safety and Environment
LPA Local Planning Authority
MW Megawatts
SED Special Engineering Difficulty
SPR ScottishPower Renewables
East Anglia ONE Offshore Windfarm November, 2016
Cable Method Statement
East Anglia ONE – EA1-CON-R-IBR-021238 Page 5
1 Introduction1.1 Project Overview
1. East Anglia ONE Limited (EAOL) was awarded a Development Consent Order (DCO) by the Secretary of State; Department
of Energy and Climate Change (DECC) on June 17th 2014 for East Anglia ONE Offshore Wind Farm (EA ONE). The DCO
granted consent for the development of a 1200MW offshore windfarm and associated infrastructure.
2. In February 2015 EAOL secured a Contract for Difference (CfD) award to build a 714MW project and ScottishPower
Renewables announced its role in leading East Anglia ONE towards construction. In April 2015 EAOL submitted a non-
material change application to DECC to amend the consent from direct current (DC) technology to alternating current (AC).
In March 2016 DECC authorised the proposed change application and issued a Corrections and Amendments Order.
3. The onshore construction works associated with EA ONE comprise of the following, which is based on the AC technology
with an installed capacity of 714MW and transmission connection of 680MW:
A landfall site at Bawdsey, Suffolk.
Up to six underground cables, approx. 37km in length.
Up to four cable ducts for the East Anglia THREE projects.
An onshore substation located at Bramford next to existing National Grid infrastructure.
4. The scope of this document relates to the installation of cable ducts and underground cables along the onshore cable route
as part of the onshore construction works.
1.2 Purpose and Scope
5. This Cable Method Statement sets out the method and programme for installing cables ducts and cables as part of the EA
ONE onshore construction works. These works include the installation of cable ducts for proposed East Anglia THREE
project which will be installed alongside the cable ducts and cables for EA ONE and herein are referred to as the ‘onshore
cable works’.
6. This Cable Method Statement has been produced to fulfil DCO Requirement 29 (1) (b) which states:
29.—(1) Save in relation to plots 448 to 450, 453 to 454 and 457 to 471 in the book of
reference—
(a) all cable ducts forming part of the onshore connection works must be installed
simultaneously together with the onshore cables for the authorised project forming part of
the onshore connection works unless sub-paragraph (2) applies; and
(b) no stage of the connection works shall commence until a written method statement
showing the programme for laying the onshore cables for the authorised project and all
cable ducts as part of a single cable laying operation has for that stage been submitted to
and approved in writing by the relevant planning authority. The method statement must
include an implementation timetable for laying the cables for the authorised project and
all ducts and must be carried out as approved.
7. All works shall be in compliance with all documents produced to fulfil all other DCO Requirements, which include, but are not
limited to;
Ecological Management Plan (EA1-CON-F-GBE-008547);
Cable Landscape Management Plan (EA1-CON-R-IBR-010129);
Code of Construction Practice (EA1-CON-F-GBE-008547);
Archaeological Written Scheme of Investigation (EA1-CON-F-IBR-010138);
Fencing and Enclosures Plan (EA1-CON-R-IBR-009818); and
Highways and Access Improvements Plan (EA1-CON-R-IBR-009582).
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East Anglia ONE – EA1-CON-R-IBR-021238 Page 6
2 Construction Overview2.1 Cable Route and Working Width
8. The onshore cable route comprises a 37km corridor between the Suffolk coast at Bawdsey and the substation at Bramford,
passing the northern side of Ipswich. The onshore cable works comprise the installation of electricity transmission cables and
ducts, between the landfall location at Bawdsey and the new substation station adjacent to the existing substation at
Bramford. A plan showing the overview of the onshore cable route is presented in Appendix 1. The majority of the route will
be constructed using trenching methods while in certain locations trenchless techniques will be used.
9. Construction activities will be undertaken within a temporarily fenced strip of land known as the working width. The working
width is determined by electrical and civil engineering considerations and allows for sufficient spacing between the cables
trenches to prevent the cables overheating, plus room for the associated temporary construction works i.e. spoil storage,
drainage, haul road, works areas for personnel and machinery. A figure showing typical cross sections of the working width is
presented in Appendix 2.
10. In accordance with the DCO the working width shall not exceed 55m, except at the horizontal directional drilling locations
specified in Requirement 10 part (6), where the working width is increased to allow for the requirements of the specialist
technique.
2.2 Specialist Techniques
11. The onshore cable route traverses a number of major transport networks and natural obstacles. To enable the installation of
the cable across these major features, specialist techniques are required, namely use of Horizontal Directional Drilling (HDD).
These key locations are listed below and are referred to as ‘Category 1’ HDD sites (locations shown in Appendix 1), in
accordance with the DCO Requirement 10, the working width at these areas is increased, to between 110m and 160m
depending on the location (see Table 2-1 for details), to accommodate the method of work:
Millers Wood
Network Rail tracks west of A14 and River Gipping
A14 Trunk Road
A12 Trunk Road
Network Rail tracks to the south of Woodbridge and Martlesham Creek
Kirton Creek
River Deben
Coastal Landfall, Bawdsey
12. These HDD sites will require additional equipment, storage and ancillary facilities to that required for the conventional open
trench installation methods in order to accommodate the drilling activities. As such, a specialist HDD compound will be set up
at each side of the HDD location to enable the specialist plant and materials to be delivered directly and to facilitate the
drilling activities.
13. In addition to the above major features, a number of other features have been identified where the conventional open cut
trenching technique is not appropriate. At these locations ‘trenchless’ methods will also to be implemented, which will
comprise of a smaller HDD or auger bore. These sites are referred to as ‘Category 2’ HDD/trenchless. As the features to be
crossed are less significant, they will not require any additional compounds and works will take place within the standard 55m
working width. Table 2-1 provides a list all the HDD / trenchless locations.
14. All of the onshore cable works will be supported by nine Construction Consolidation Sites (CCSs) (referenced A to I), these
are construction compounds which will be utilised for welfare, site staff accommodation, parking, as well as providing secure
storage for materials, plant and equipment. The CCSs are categorised as Primary and Secondary, there are two Primary
CCSs; CCS B will be a designated storage and delivery facility and the main administrative compound and CCS E will be a
designated storage and delivery facility with designated office space. The remaining seven Secondary CCSs shall be for the
purpose of access, storage and deliveries. A list of the CCS locations is presented in Table 2-2 and the locations are shown
on the presented in the Appendix 1.
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Table 2-2 Construction Consolidation Site Locations
CCS Ref CCS Type Address
A Secondary Bullen Lane, Bramford, Ipswich, Suffolk IP8
B Primary Paper Mill Lane, Claydon, Ipswich, Suffolk IP6 0AP
C Secondary Witnesham Road, Ipswich, Suffolk IP6
D Secondary Church Road, Ipswich, Suffolk IP6 9DS
E Primary Top Street, Martlesham, Suffolk IP12
F Secondary Woodbridge Road, Newbourne, Woodbridge, Suffolk IP12 4PA
G Secondary Park Lane, Ipswich, Suffolk IP10
H Secondary Sheepgate Lane, Ipswich, Suffolk IP10 0QZ
I Secondary Ferry Road, Woodbridge, Suffolk IP12 3AS
2.4 Construction Zones
15. For the purpose of construction the onshore cable works has been divided into eleven construction zones. The construction
zones are based on a combination of access controls and lock-out points, which are defined by the presence of natural
barriers or other constraints that will interrupt the continuity of access to the onshore cable route. These eleven construction
zones are the main basis of construction programme development. Table 2-3 lists the breakdown of these zones and
includes the corresponding Work Package Numbers (Work No.), referred to within the DCO and their locations are shown on
the plans presented in Appendix 3.
Table 2-3 Construction Zones
Zone DCO WorkNo.
From To ApproximateLength (m)
1 37E to 36 Substation Pound Lane 3930
2 36 to 35A Pound Lane East of Network Rail and RiverGipping HDD
835
3 34B to 33A East of Network Rail and RiverGipping HDD
East of A14/Old Ipswich RoadHDD
785
4 32 to 29 East of A14/Old Ipswich RoadHDD
East of Clopton Lane 6520
5 29 to 26 East of Clopton Lane West of River Lark 4870
6 25C to 21 West of River Lark North of Network Rail &Martlesham Creek HDD
3410
7 20 to 18 North of Network Rail &Martlesham Creek HDD
East of Waldringfield RoadCamp Site
3450
8 15 (part of) East of Waldringfield RoadCamp Site
South of Ipswich Road (HeathRoad)
410
9 17 to 15 South of Ipswich Road (HeathRoad)
North of Kirton Creek HDD 3190
10 14 to 8 North of Kirton Creek HDD West of River Deben HDD 4250
11 7B to 3B West of River Deben HDD Landfall 4900
East Anglia ONE Offshore Windfarm November, 2016
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East Anglia ONE – EA1-CON-R-IBR-021238 Page 9
3 Construction Methodology16. This section describes the construction methodology associated with the installation of the onshore cable works, these works
comprise of the following and a description of each is provided in the following sections:
Site Preparation;
Site Enabling Works;
Open Trench Duct Installation;
Trenchless Duct Installation (e.g. HDD);
Cable Installation; and
Reinstatement.
3.1 Site Preparation
17. The site preparation works comprise the following activities:
Highways Improvements;
Archaeology Mitigation Works; and
Vegetation Clearance.
18. The site preparation works will be undertaken prior to the commencement of the main construction works. A brief description
of each of the activities is provided in sections 3.1.1 to 3.1.3. All of these activities are covered by independent DCO
Requirements, detailed plans have been prepared to fulfil these requirements.
3.1.1 Highways Improvements
19. To facilitate safe access and egress for the onshore cable works a series of highways improvements are required which
require road alterations works to be completed prior to the main construction work commencing. Such improvements include
junction improvements and the installation of passing places. All identified highway improvement works will be completed
prior to the construction works commencing in the associated area to ensure the road network is suitable for construction
use.
20. Full details of the improvement works are presented in the Highways Improvements and Access Management Plan (EA1-
CON-R-IBR-009582), which has been produced to fulfil DCO Requirement 14 and 25 (c).
3.1.2 Archaeology Mitigation Works
21. An Archaeological Written Scheme of Investigation (WSI) (EA1-CON-F-IBR-010138) has been prepared to fulfil DCO
Requirement 18. The WSI identifies areas where a programme of archaeological investigation (evaluation, mitigation,
excavation, built heritage recording and watching brief) is required, and the measures which will be taken to protect, preserve
in situ or record any significant archaeological remains that may be found.
22. The programme of archaeological investigation works will be undertaken in accordance with the approved WSI in all
identified archaeological sensitive areas prior to the commencement of the main construction works. Further details provided
in the Archaeological Written Scheme of Investigation (EA1-CON-F-IBR-010138).
3.1.3 Vegetation Clearance
23. A Cable Landscape Management Plan (CLMP) (EA1-CON-R-IBR-010129) has been prepared to fulfil DCO Requirement 12.
The CLMP identifies the trees and hedgerows that will be removed along the onshore cable route to facilitate the construction
activities. In order to avoid any impact on potential breeding birds where possible vegetation clearance will be completed
outside the breeding bird season (March to September).
24. All vegetation clearance will be completed in accordance with the Cable Landscape Management Plan (EA1-CON-R-IBR-
010129). An Arboricultural Clerk of Works will be appointed to ensure that all tree works are undertaken to the required
standards.
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East Anglia ONE – EA1-CON-R-IBR-021238 Page 10
3.2 Site Enabling Works
25. The site enabling works comprise the following activities:
Access improvements;
Construction of CCSs;
Preparation of working width (i.e. installation of fencing);
Topsoil stripping; and
Installation of the haul road.
26. A description of these activities, in sequence, is provided in sections 3.2.1 to 3.2.5. All temporary works associated with the
enabling works, will be continuously monitored and maintained throughout the construction period. Where required
maintenance and/or repairs of the haul road, fencing etc. will be undertaken.
3.2.1 Access Improvements
27. To facilitate safe access and egress for the onshore cable works a series of access improvements are required which include
the widening of existing entrancesand the installation of new bellmouths onto public roads. Full details of the improvement
works are presented in the Highways Improvements and Access Management Plan (EA1-CON-R-IBR-009582).
3.2.2 Construction of CCSs
28. The construction of the CCSs involves stripping of topsoil, importing and laying stone for the compound base and installing
cabins and welfare facilities. The two Primary CCSs (‘B’ and ‘E’) will be the first to be installed. Once these two main
compounds are installed, the Secondary CCSs will be installed to provide access points to allow the haul road construction to
start.
3.2.3 Preparation of Working Width
29. Temporary fencing and gateways will be erected along the boundary of the working width. The default fencing type will be a
basic type, e.g. post and rail or post and wire, visually defining the boundary of the working width. Where the boundary
interface requires a higher level of protection, for instance livestock fields or housing developments, then protective fencing
will be used. Signage and notices will be fixed along this boundary to inform members of the public of the works being
undertaken. Full details of the fencing to be installed are detailed in the Fencing and Enclosures Plan (EA1-CON-R-IBR-
009818).
30. High visibility signage and suitable protection will be installed to denote any third party utility crossings (such as gas pipelines
or overhead power lines). An Arboricultural Clerk of Works will be appointed during construction to oversee the erection of
fencing for the protection of trees and hedgerows that are to be retained.
3.2.4 Topsoil Stripping
31. Once the working width has been prepared, the remaining topsoil will be stripped from: the haul road location, trench areas
and subsoil storage areas, and then stored in a designated area within the working width (see typical cross section in
Appendix 2). Topsoil storage and management shall be compliant with the relevant standards and guidance as set out in the
Cable Landscape Management Plan (EA1-CON-R-IBR-010129), which includes but is not limited to:
Maximum storage heights of mounds: 2m for topsoil.
Topsoil to be stripped in the driest condition possible.
Use tracked equipment wherever possible to reduce compaction.
Confine movement of trucks or dumpers to designated temporary haul routes.
Do not incorporate vegetation into topsoil to be stored.
Do not strip soils during or after heavy rainfall or when there are pools if water on the surface.
Do not strip topsoil too deeply so that subsoil becomes incorporated, thereby reducing fertility.
Do not remove topsoil from below the spread of trees and hedgerows to be retained.
To prevent compaction of topsoil and subsoil during stockpiling, the stockpiles shall be formed by tipping in mounds
which shall not subsequently be tracked over by vehicles.
Stockpiles shall be kept free of pernicious weeds.
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Cable Method Statement
East Anglia ONE – EA1-CON-R-IBR-021238 Page 11
Topsoil and subsoil shall not be allowed to be mixed or cross contaminated with one another or any other unsuitable
materials.
No soils shall be stored within the Root Protection Area of trees or shrubs.
32. Topsoil shall be stored to one side of the working width, in such a way that it is not mixed with any subsoil. Storage time will
be minimised, to prevent the soil deteriorating in quality. Topsoil stripped from different fields will be stored separately, as will
soil from specific hedgerow banks or woodland strips.
3.2.5 Installation of Haul Road
33. A temporary haul road will be installed along the cable route between the CCS locations and access points onto the local
public roads. The haul road will installed for a width of 5.5m along a designated route, following the initial topsoil stripping.
The temporary haul road will be constructed working from the installed CCS locations in two directions, away from the CCS
and towards the adjacent CCS, along the onshore cable route following the initial topsoil stripping.
34. Temporary haul road construction will typically involve the placement of a depth of suitable imported stone material onto a
geotextile on existing subsoil. In order to reduce the volume of imported stone material, the preferred method of temporary
haul road construction will involve the improvement of the underlying conditions prior to the installation of the imported stone.
The methods will follow one of the following options to improve the bearing capacity of the sub-soil; the placement of a geo-
grid material or chemical stabilisation. The type of method used will depend on a number of factors including ground
conditions, programme and landowner requirements. In the event that the stabilisation cannot be achieved then the
temporary haul road will be constructed using the traditional method and be at an increased depth of imported stone.
35. In some special circumstances the temporary haul road may comprise a temporary “trackway”, this will only be the case
where the haul road is required only for a short period of time (i.e. weeks) at locations where through road access is not
required.
36. Temporary crossings at watercourses and drainage ditches will be installed where haul road access is required across such
features. The design of each crossing will have prior approval from the relevant drainage authority. Further details on
watercourse crossings are provided in the Watercourse Crossing Method Statement within the Code of Construction Practice
(EA1-CON-F-GBE-008547).
3.3 Open Trench Duct Installation
37. The open trenching method will be used for the installation of cable ducts along the majority of the onshore cable route. The
open trench method involves the excavation of a trench, using a suitably sized tracked excavator (or similar equipment),
followed by the installation of the cable ducts and then the backfilling of the trench. The ducts will be laid to a minimum depth
to the top of the cables of approximately 1.25m below ground level, unless a shallower depth is required to avoid existing
utilities. The ducts for EA ONE will be installed in two parallel trenches, each trench will contain three power cable ducts and
one fibre optic cable duct. Figure 1 below shows the typical content and layout of the ducts as installed in open trenches for
EA ONE, however the width of trench and spacing between them would vary depending on the depth of burial.
East Anglia ONE Offshore Windfarm November, 2016
Cable Method Statement
East Anglia ONE – EA1-CON-R-IBR-021238 Page 12
Figure 1 Typical Trench Layout for EA ONE
38. A further trench will be excavated in parallel to install three power cable ducts and a fibre optic duct for the future EA THREE
project. Figure 2 below shows the typical content and layout of the ducts to be installed for EA THREE. A cross section
showing EA ONE and EA THREE trenches are included in Appendix 2.
Figure 2 Typical Trench Layout for EA THREE
39. Once trenches are excavated the ducts will be installed within the trench. Ducting will be delivered to Primary CCS Sites and
then will be transferred, via the haul road or along the designated routes of the public road network, to the Secondary CCS
Sites for temporary storage or onto the required location on the onshore cable route. The ducts will be surrounded by a
thermally stable backfill of cement bound sand (CBS) or selected sands to ensure a known thermal conductivity around the
East Anglia ONE Offshore Windfarm November, 2016
Cable Method Statement
East Anglia ONE – EA1-CON-R-IBR-021238 Page 13
cables in order to maintain the cable rating (capacity to carry current). The trench will then be backfilled with the excavated
subsoil to working level.
40. Cable protection tiles would be fitted above the cables in each trench, featuring indented lettering warning of the danger of
electricity below. Plastic warning tape will be placed between the protection tiles and the ground surface, alerting future
excavators to the danger of the electric cables below.
41. The excavation of the trenches, duct installation and backfilling will be sequenced to minimise the amount of material
required to be moved to temporary storage or removed from site. The excavations will be progressed in stages, opening a
length of trench, installing the ducts then reinstating the trench with the same excavated subsoil back to working level. The
trenches for EA ONE will be installed first, starting with the cable trenches furthest away from the haul road, followed by the
trench for EA THREEs.
42. Particular care will be taken to ensure that the existing land drainage regime is not compromised as a result of the
construction. Pre-construction survey and local landowner information will be utilised to identify drainage locations, known
drainage features will be marked with appropriate wooden stakes along the line of the drain. Land drainage systems will be
maintained during construction, and be reinstated on completion. Temporary cut-off drains will be installed. These will be
installed parallel to the trenchs, before the start of construction, to intercept runoff from the stripped ground and stockpiled
soils before it reaches the trenches. These interceptor drains will discharge to local drainage ditches after passing through
treatment, as appropriate, to minimise sediment release. A further description of the control measures available to be used
are included in the Surface Water & Drainage Management Plan (EA1-GRD-F-IEC-007683).
3.4 Trenchless Duct Installation
43. Where, due to the existence of features, it is not possible to install the cable ducts using the open trench method, trenchless
installation techniques shall be used. Trenchless techniques require the use of specialist drilling and pulling equipment to
install the cable ducting, avoiding the need to dig an open trench. The most widely used of these techniques is HDD,
however other methods such as auger boring may be used where appropriate.
44. The locations where trenchless duct installation is required are defined in Table 2-1. Two main categories of trenchless
operation have been identified along the onshore cable route as Category 1 and Category 2 (see Section 2.2 for further
details). Category 1 trenchless locations are to address those sites with major features, corresponding to the locations
identified in the DCO Requirement 10. All of these crossings will be carried out using the HDD technique. The Category 2
trenchless crossings will use a combination of smaller HDD or auger boring, as appropriate to the location.
45. At each of these Category 1 HDD locations there will be an access installed to each side of the crossing, either using the haul
road or a new access created directly off the public road dependent on location and sufficient space allocated for a HDD
compound. These crossings have a wider corridor, as identified in the DCO, and their profiles are based on drilling a series of
a single bores for each cable. This is in order to meet the performance requirements of the circuits installed at greater depths.
Figure 3 shows typical cross-sections of the nine main cable ducts that are required for installation of ducts for EA ONE and
EA THREE, these are also presented in Appendix 4. Configurations will depend on length of the drills and how deep the drills
need to go. Flat cable formation is required for deeper drills, trefoil is required for shallower drills. The latter will be deployed
where ever possible so that minimum width and construction time is used.
46. Category 2 trenchless locations are required for crossings of lesser features or to reduce disruption and are shorter in length
to the Category 1 locations. The cable corridor working width at these trenchless locations is not widened beyond 55m and
access to these locations will be provided through the temporary haul road.
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East Anglia ONE – EA1-CON-R-IBR-021238 Page 14
Figure 3 Typical Trenchless Layouts
47. The HDD method involves drilling under the obstacle at an appropriate depth using drill which can travel horizontally and
vertically. It requires two areas of hard standing to be installed at each side of the HDD crossing. The first will provide space
for the installation of the HDD rig site where the HDD enters the ground, and the second is at the exit point on the other side
of the crossing. The exit point is also typically the area where the ducting will be joined together into longer strings from
where it will be pulled through the bored hole, back towards the HDD rig site.
48. For a Category 1 HDD, a typical entry point site (area of approximately 75m x 100m), would be required to accommodate the
drilling rig, ancillary equipment, offices, working facilities and storage of drilling fluid, water and drill pipes. At the exit point of
each crossing, an area of approximately 30m x 25m would be required to accommodate the exit pit and mud storage tanks
and ducts for the crossing.
49. A typical HDD operation (Category 1 or Category 2) involves three distinct stages:
1. Drilling a pilot hole from the entry point to the exit point.
2. Reaming (widening) of the bore using special cutting heads, to enlarge the bore to the required diameter.
3. Pulling one or more ducts back through the reamed hole.
50. The addition of a drilling fluid, such as bentonite (a type of clay), is used to lubricate the drill head during cutting and also to
assist in the removal of waste spoil out of the hole, as it is widened (reamed). This procedure is repeated until the drilled
hole has reached the intended final diameter. The hole is typically cut to a size 1.5 times larger than the duct it has to carry.
This additional diameter is to allow the easier removal of drill cuttings and the installation of the duct, allowing for any soil
expansion that may occur during pulling. At each HDD site, the above process will be repeated until all of the required ducts
are installed at the crossing.
51. Once all the individual ducts have been installed, the drilling rig and associated plant and equipment will be removed. The
retained drilling mud and collected cuttings will be sampled, analysed and disposed of to an off-site waste disposal facility, in
accordance with the Waste Management Plan (EA1-GRD-F-IEC-007682).
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East Anglia ONE – EA1-CON-R-IBR-021238 Page 15
52. Category 2 trenchless crossings will use a combination of smaller HDD method (as described above) and/or auger boring, as
appropriate to the location. The auger boring method requires the excavation of pits on either side of the feature to the depth
of the required installation. Continuous flights are rotated and simultaneously pushed into the ground at this depth. As the
bore progresses the ground is cut and the auger flights convey the material back into the work pit.
3.5 Cable Installation
53. Once the cable duct installation is completed then works will commence on the installation of the cable within the ducting
system. As the onshore cabling typically comes on drums of up to 2,000m in length, jointing bays will be required along the
cable route to join the sections of cable together. These jointing bays, approximately 10m long x 5m wide x 5m deep, will be
constructed at regular intervals along the onshore cable route to allow cable pulling and jointing at a later stage. The joint bay
will be excavated, a concrete poured floor will be created and concrete or brick walls will be installed. The bay will be topped
with concrete slabs which will be covered with subsoil to a depth of 1.1m.
54. Access to the joint bays will be required during operation for routine integrity testing. Access will take the form of an
inspection pit with a manhole cover which will be visible at the surface.
55. Associated with each of the joint bays will be an area of temporary hard-standing suitable to safely accommodate cable
drums and pulling equipment. These areas will be constructed using imported stone or using temporary “trackway”, which
would then be used at different locations along the route.
56. Cables will be delivered to the respective CCSs for secure storage and handling. The cable drums will be lifted from the
delivery trailer onto a hard standing for temporary secure storage. From the CCSs, the cables will be transferred, along the
haul road, by tractor and cable drum trailer to the corresponding joint bays when required for pulling operations.
57. The cable pulling system will consist of a steel bond attached to the cable end and then to a powered winching system, with
free spinning cable rollers placed along the bottom of the joint bay up to the end of the cable duct. Other variants of cable
pulling systems can be used, which could include the use of motorised rollers or tracked caterpillar drives to push the cable
forwards, as it is pulled from the opposite end.
58. The cable drum will be placed on a raised spindle mounted on a hydraulic cable trailer. The cable will then be pulled from the
drum into the trench on the pre-installed rollers, and once drawn through will leave the sealed ends in each joint bay ready for
jointing to previous and successive cable lengths.
59. Temporary weather-proof structures (‘tents’) will be erected over each joint bay when the construction team are ready for
cable jointing to commence. This is to provide a dry and clean atmosphere to carry out jointing tasks to the required quality.
Artificial lighting and heating will also be required, should seasonal and weather conditions dictate.
60. On completion of the cable installation and jointing works, the joint bay structure will be left in situ and the land around them
reinstated leaving access to the inspection pit used for testing of circuits and commissioning works. On completion of testing
and commissioning works area above the joint bays will be backfilled and the ground fully reinstated with the exception of the
surface manholes.
61. The onshore cable route will be marked with marker posts at key locations such as field boundaries and main river crossings.
These will be visible from the ground and all marker posts will be located to minimise interference with agricultural activities.
62. The cable installation will continue throughout the route, potentially with simultaneous installation at several locations,
depending on progress and programme as detailed in Section 4.
East Anglia ONE Offshore Windfarm November, 2016
Cable Method Statement
East Anglia ONE – EA1-CON-R-IBR-021238 Page 16
3.6 Reinstatement
63. After the completion of cable installation, testing and commissioning, the reinstatement works will commence, which will
comprise:
Removal of all temporary infrastructure including the haul road and associated infrastructure (e.g. flume crossings,
temporary bridges).
Topsoil will be re-instated along the working width. This will be graded, levelled and seeded where required in
accordance with the Cable Landscape Management Plan (EA1-CON-R-IBR-021236).
Hedgerows and trees will be replanted in line with Cable Landscape Management Plan during the first appropriate
planting season following site restoration.
CCS and HDD compounds will be removed and reinstated to match original profiles.
Temporary fencing will be removed and affected ground reinstated.
All temporary signage associated with traffic routes will be removed.
64. All public roads will be reinstated in line with New Roads and Street Works Act 1991 Specification for the Reinstatement of
Openings in Highways.
East Anglia ONE Offshore Windfarm November, 2016
Cable Method Statement
East Anglia ONE – EA1-CON-R-IBR-021238 Page 17
4 Programme4.1 Overview
65. The main construction works for the onshore cable route are planned to take place over two years between March 2017 and
February 2019. The works will be completed in four packages, with a contractor being appointed to undertake each package;
Site Enabling Works (as detailed in Section 3.1 and reinstatement works).
Cable Civil Works (duct installation via open trench method).
Trenchless Works (duct installation via trenchless method e.g. HDD).
Cable Installation.
66. As indicated in section 3.1 some site preparation activities will be undertaken prior to the start of the main construction works.
These works are programmed to commence from December 2016.
67. A summary of the overall main construction works programme is shown in Table 4-1, on completion of the construction
works, commissioning works will continue until full operation. Further details on each package of works are provided in the
following sections, which include an anticipated breakdown of the programme into the construction zones (as detailed in 2.4
and shown in Appendix 2). Please note the programme presented does not account for potential unforeseen events, such as
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Note:This map has been produced to the latest known information at the time of issue, and has been produced for your information only.Please consult with the SPR GIS team to ensure the content is still current before using the information contained on this map.To the fullest extent permitted by law, we accept no responsibility or liability (whether in contract, tort (including negligence) or otherwise in respect of any errors or omissions in the information contained in the map and shall not be liable for any loss, damage or expense caused by such errors or omissions.
Note:This map has been produced to the latest known information at the time of issue, and has been produced for your information only.Please consult with the SPR GIS team to ensure the content is still current before using the information contained on this map.To the fullest extent permitted by law, we accept no responsibility or liability (whether in contract, tort (including negligence) or otherwise in respect of any errors or omissions in the information contained in the map and shall not be liable for any loss, damage or expense caused by such errors or omissions.
Note:This map has been produced to the latest known information at the time of issue, and has been produced for your information only.Please consult with the SPR GIS team to ensure the content is still current before using the information contained on this map.To the fullest extent permitted by law, we accept no responsibility or liability (whether in contract, tort (including negligence) or otherwise in respect of any errors or omissions in the information contained in the map and shall not be liable for any loss, damage or expense caused by such errors or omissions.
Note:This map has been produced to the latest known information at the time of issue, and has been produced for your information only.Please consult with the SPR GIS team to ensure the content is still current before using the information contained on this map.To the fullest extent permitted by law, we accept no responsibility or liability (whether in contract, tort (including negligence) or otherwise in respect of any errors or omissions in the information contained in the map and shall not be liable for any loss, damage or expense caused by such errors or omissions.