Specification and Scope of Work for:
Lowering the NorNed Power Cable at
Westereems Shipping Channel
and
Remedial Burial of the NorNed
Power Cable along the cable route
for
Prepared by:
Checked by:
Primo Marine
Thijs van Traa, Miriam van Endt, Wino Snip
TenneT
Hans Scheefhals, Benjamin Rasing, Hans van Veen
Specification and Scope of Work for
Lowering the
NorNed power cable at Westereems Shipping Channel
and
Remedial Burial of the NorNed
power cable along the cable route
Table of Contents
1
INTRODUCTION ............................................................................................................... 3
1.1
1.2
1.3
1.4
2
LIST OF ABBREVIATIONS AND DEFINITIONS ...................................................................................... 3
GENERAL .................................................................................................................................. 6
COORDINATES OF CABLE – SHIPPING CHANNEL WESTEREEMS............................................................. 9
PROJECT GEODETICS ................................................................................................................... 9
SPECIFICATION FOR THE LOWERING AND REMEDIAL BURIAL WORKS ........................... 10
2.1
2.1.1
2.1.2
2.1.3
2.2
3
LOWERING OF THE CABLE IN THE WESTEREEMS SHIPPING CHANNEL................................................... 10
Design for Lowering the Cable ............................................................................................ 10
Cable DoB ............................................................................................................................ 11
Design of the longitudinal cable profile .............................................................................. 12
REMEDIAL BURIAL OF THE CABLE ALONG THE CABLE ROUTE .............................................................. 14
SCOPE OF WORK............................................................................................................ 15
3.1
3.2
3.3
4
LOWERING OPERATIONS OF THE CABLE IN THE WESTEREEMS (PART 1)............................................... 15
THE ENVISAGED REMEDIAL BURIAL OPERATIONS (PART 2)................................................................ 16
PLANNING .............................................................................................................................. 17
DETAILED REQUIREMENTS............................................................................................. 18
4.1
4.2
4.3
4.4
4.5
4.6
4.7
4.8
4.9
4.10
4.11
4.12
4.13
4.14
4.15
4.15.1
4.15.2
4.15.3
4.15.4
4.15.5
5
GENERAL ................................................................................................................................ 18
FAMILIARIZATION WITH EXISTING SURVEY DATA AND IDENTIFICATION OF ENVIRONMENTAL CONDITIONS .... 18
PERFORM DETAILED ENGINEERING AND PLANNING .......................................................................... 18
ISSUE OF PROJECT SPECIFIC HSE PLAN .......................................................................................... 18
PREPARATION OF TIME SCHEDULE ................................................................................................ 18
PREPARATION OF PRE-WORKS DELIVERABLES ................................................................................. 18
HAZOP, PRE-OPS MEETING AND SJA ............................................................................................ 19
INSTALLATION WAVE RIDER BUOY AND CURRENT METER ................................................................... 19
FACILITIES FOR TENNET (MARINE WARRANTY SURVEYOR AND TENNET REPRESENTATIVES) .................... 19
MOBILISATION AND CALIBRATIONS .............................................................................................. 19
PRE-LOWERING WORKS SURVEY ................................................................................................. 20
LOWERING TRIAL ...................................................................................................................... 20
LOWERING OF CABLE AND INTERMEDIATE SURVEYS ......................................................................... 21
DEMOBILISATION ..................................................................................................................... 21
REPORTING AND FINAL RESULTS REPORTING .................................................................................. 22
General ................................................................................................................................ 22
Data formats ....................................................................................................................... 22
Charts .................................................................................................................................. 22
Coordinate format requirements ........................................................................................ 23
Visual soft requirement ....................................................................................................... 23
ADDITIONAL REQUIREMENTS ........................................................................................ 24
5.1
5.2
5.3
6
MARINE OPERATIONS................................................................................................................ 24
ENVIRONMENT ........................................................................................................................ 24
PERMITS................................................................................................................................. 24
INFORMATION............................................................................................................... 25
6.1
6.2
6.3
PROPERTIES OF THE NORNED HVDC CABLE .................................................................................. 25
SOIL AND MORPHOLOGY ............................................................................................................ 25
CABLE ROUTE .......................................................................................................................... 25
LIST OF APPENDICES 1 - 9 ......................................................................................................................... 26
APPENDIX 10 : PRICING SCHEDULE ........................................................................................................... 27
Document1 Date 7/31/2017
Page 2 of 27
Specification and Scope of Work for
Lowering the
NorNed power cable at Westereems Shipping Channel
and
Remedial Burial of the NorNed
power cable along the cable route
1 INTRODUCTION
1.1
List of Abbreviations and Definitions
In this Scope of Work document and contractual documents to follow this tender, the
words and expressions defined shall have the following meanings assigned to them in
both singular or plural, except where the context requires otherwise:
Definition / Abbreviation
Meaning / Description
Applicant
Any legal entity participating in the tender
Authority
Local, regional or national governmental body
Cable
NorNed HVDC cable
CD
Chart Datum
Contract
All documents constituting the agreed terms and
conditions as listed the CoC document.
Contractor
Applicant who was awarded the contract for Lowering
and Remedial Burial Works, and the legal successors
in title to this person, but not (except with the prior
written consent of TenneT, which shall not be
unreasonably delayed or withheld) any assignee.
Contractor’s Operation
The dedicated full-time Site manager present at the
Site for the duration of the Site activities, who shall
have the authority to act and decide on behalf of
Contractor on all matters directly related to Site
activities.
Best and Final Offer from Contractor dated […] with
reference [….].
Conversion represents all activities that are required in
the event a modification is required to the Excavation
Spread due to a change in operations, e.g. from
Lowering operations to Remedial Burial operations or
vise versa
Cable Tracking
Manager ("COM")
Contractor's Offer
Conversion
CT
Demobilisation
DOB
After the TOR has approved the as-built survey and
issued the Taking-Over Certificate, Contractor can
commence with the demobilization from site.
Depth of Burial (measured from seabed to top of cable)
DP
Dynamic Positioning
DTM
Digital Terrain Model
Excavation Spread
All equipment and vessel(s) used by Contractor to
perform the Works.
Flat Mass Impregnated (Cable)
FMI
Force Majeure
Document1 Date 7/31/2017
Any event or circumstance which is reasonably beyond
a Party’s control such as but not limited to war,
hostilities, rebellion, terrorism, revolution, riot,
Page 3 of 27
Specification and Scope of Work for
Lowering the
NorNed power cable at Westereems Shipping Channel
and
Remedial Burial of the NorNed
power cable along the cable route
FPV
commotion, labor disputes and strikes (with the
exception of labor disputes and strikes within
Contractors' organization and/or the organization of
Third Parties that Contractor may employ for the
Lowering/Reburial activities, munitions of war,
explosive materials and natural catastrophes such as
earthquake, hurricane, typhoon or tsunami.
Fall Pipe Vessel
GIS
Geographic Information System
GWDS /WSA
Generaldirektion Wasserstraßen und Schiffahrt/
Wasser und Schiffahrt Ambt Emden
HSE
Health Safety and Environment
HVDC
High Voltage Direct Current
KP
Kilometer Point
LAT
Lowest Astronomical Tide
Lowering
LSS
Lowering the NorNed Power Cable at Westereems
shipping channel
DTM Software Suite from McCarthy Taylor
MBE
Multi Beam Echosounder
MFE
Mass Flow Excavation
Mobilisation
MWS
The activity of Contractor to prepare and transit his
equipment to the site, ready for the Reburial
Operation. The mobilisation is deemed to be complete
when the TOR has accepted the calibrations and
Contractor is ready for commencing with the
Lowering/Reburial activities
Marine Warranty Surveyor
NAP
Nieuw Amsterdams Peil
OLT ?? par 19
Operational
The period that starts at the moment of completion of
Mobilisation of the VOO and ends on the day TenneT
has approved the activities and Contractor may start
demobilisation from the Site.
PBD
Protective Burial Depth
QC
Quality Control
RA
Risk Assessment
Remedial Burial
Reburial of the NorNed Power cable in the Waddenzee
RWS
Rijkswaterstaat
Document1 Date 7/31/2017
Page 4 of 27
Specification and Scope of Work for
Lowering the
NorNed power cable at Westereems Shipping Channel
and
Remedial Burial of the NorNed
power cable along the cable route
Site
Any location where Work is being performed
SOW
Scope Of Work as per this document
SSS
Side Scan Sonar
Subsea Excavation
Equipment
That part of the Excavation Spread that is subsea and
removes the soil and is in close vicinity of the cable.
TenneT
The company named herein and the legal successors
in title to this company, but not (except with the prior
written consent of Contractor, which shall not be
unreasonably delayed or withheld) any assignee.
TenneT’s Operation
The manager of TenneT who shall have the authority
Representative ("TOR")
to act and decide on behalf of TenneT on all matters
directly related to the Site activities
Third Party
Any party other than Applicant/Contractor, TenneT or
Authority.
Transit
Transit incorporates all activities while sailing to /
from port towards the Site before Mobilisation and
after Demobilisation.
VOO
Vessel of Opportunity, the (yet unidentified) main
vessel involved in the Lowering/Reburial Operation.
VTS
Vessel Traffic Service
Westereems
Westereems Shipping Channel
Work
All activities to be performed by Contractor under the
contract
Workability Analysis
Listing of limitations of Contractor's spread in relation
to Weather, waves, current, visibility other natural
conditions
WoW
WROV
Document1 Date 7/31/2017
Waiting on Weather due to weather conditions
exceeding limitations of spread and/or preventing safe
operations.
Working Class Remotely Operated Vehicle
Page 5 of 27
Specification and Scope of Work for
Lowering the
NorNed power cable at Westereems Shipping Channel
and
Remedial Burial of the NorNed
power cable along the cable route
1.2
General
The NorNed HVDC cable, constructed in the period between 2006 and 2008 is a HVDC
long distance 450 kV power exchange link between Feda in Norway and Eemshaven in
The Netherlands and for the first 270 kilometres consist of two identical single core mass
impregnated cables with one common double steel armoring. The total submarine cable
length is approximately 576 km. A detailed description of the cable design can be found in
Appendix 3.
Due to (1) deepening of the Westereems Shipping Channel and (2) unstable seabed, the
Cable burial depths must at these locations be increased while the Cable remains in
operation.
This document is part of the tender package for the Lowering campaign of the Cable in
the Westereems Shipping Channel (1) and Remedial Burial in some areas along the
Cable route (2) and defines the Scope of Work and Specifications for both Works.
Part 1
The Cable crosses the Westereems Shipping Channel at KP 40.182.
The Westereems Shipping Channel will be deepened for vessel traffic reasons and in
order to maintain the required burial depth the Cable has to be deepened accordingly
between KP 39 and KP 43 along the cable route.
Part 2
On multiple locations in the area between KP 0.0 (the starting point at the dike at
Eemshaven) and KP 57.0, due to its exposure to strong tidal currents and unstable
seabed soils, the burial depth is no longer in line with licence requirements. Since rockdumping is not allowed at these locations Remedial Burial activities are required to
uphold the protection of the Cable.
For reasons of cost and logistics TenneT preferably considers the joint scope of Part 1
and Part 2 to be executed in one continuous operation and one integral part of this
tender. Due to interactions with Third Parties performing the deepening of the
Westereems Shipping Channel (commissioned by RWS) various elements of the Work of
Part 1 may be split or rescheduled.
The above results in the following Lowering Works of the Cable:
1. Lowering the Cable where it crosses the Westereems Shipping Channel to a
depth of -19,10 meters (NAP) over top of cable (cable diameter approx. 220 mm.)
2. Remedial Burial of the Cable as described in the Scope of Work in areas along the
Cable route , as listed in Appendix 7 below.
TenneT has performed the pre-design of the Work and Contractor shall perform the
Work, in accordance with the Scope of Work and specifications defined in this document.
In May 2015 TenneT performed the Bathymetric/SSS/DOB survey of the Westereems
crossing and other relevant parts of the Cable, whereby the latest water depths and
depths of burial of the cable will be known and the results whereof will be handed over to
Contractor without delay.
It is TenneT’s intention to start the Works soon after contract award and Contractor will
finalize the Works for Part 1 latest December 2016, and for Part 2 latest May 2016.
Document1 Date 7/31/2017
Page 6 of 27
Specification and Scope of Work for
Lowering the
NorNed power cable at Westereems Shipping Channel
and
Remedial Burial of the NorNed
power cable along the cable route
It should be duly noted that TenneT does not allow any physical contact by the
Subsea Excavation Equipment with the Cable during the Work. It should moreover
be noted that during the Work, the Cable will remain fully powered.
Apart from the critical execution of work over a live cable, this fact prevents putting a
signal (tone) on the Cable. Contractor shall moreover be aware of the absence of a
residual magnetic field from the Cable, due to the nature of its design. Still, Contractor is
required to be able to monitor the Cable during the Lowering and Remedial Burial
operations.
Although located geographically in the Netherlands, a part of the Remedial Burial route
falls under the jurisdiction of the Dutch and German Authorities. (GWDS/WSA)
Document1 Date 7/31/2017
Page 7 of 27
Specification and Scope of Work for
Lowering the
NorNed power cable at Westereems Shipping Channel
and
Remedial Burial of the NorNed
power cable along the cable route
Figure 1.1 presents the southern part of the Cable route and Figure 1.2 presents the
Westereems Crossing Location.
Figure 1.1 Overview Cable section KP 5 – KP 48
Figure 1.2 Westereems Shipping Channel Crossing Location
Document1 Date 7/31/2017
Page 8 of 27
Specification and Scope of Work for
Lowering the
NorNed power cable at Westereems Shipping Channel
and
Remedial Burial of the NorNed
power cable along the cable route
1.3
Coordinates of Cable – Shipping Channel Westereems
The crossing location where the centerline of the Westereems Shipping Channel and the
Cable intersect is defined as:
WGS’84 :
53º 36.865’ N
006º 23.920’ E
RD :
X = 221942 m
Y = 625856 m
ED’50 UTM 31N
724889.03
5946203.88
KP Cable :
KP 40.182
LAT-NAP difference
1,61 m
1.4
Project geodetics
The project geodetic system is UTM 31N - ED’50.
Vertical reference will be NAP (equals MSL).
Document1 Date 7/31/2017
Page 9 of 27
Specification and Scope of Work for
Lowering the
NorNed power cable at Westereems Shipping Channel
and
Remedial Burial of the NorNed
power cable along the cable route
2 Specification for the Lowering and Remedial Burial Works
2.1 Lowering of the Cable in the Westereems Shipping Channel
2.1.1
Design for Lowering the Cable
The (RWS) design for the deepening of the Westereems is presented in Appendix 1:
“Tracébesluit Lengteprofiel”, Bijlage 1b Tekeningen lengteprofiel_tcm318-360043.pdf”
(drawing nr. 077240328-2) and “Tracébesluit Dwarsprofielen”, “Bijlage 1a Tekeningen
dwarsprofielen_tcm318-360044.pdf” (drawing nr. 077240328-1), as well as an overview
drawing (“overzichtstekening”) Bijlage 1c.
From “Bijlage 1b Tekeningen dwarsprofielen_tcm318-360044.pdf” the cross section
(“dwarsprofiel A”) at the Westereems has been copied and presented in Figure 2.1 below.
As can be seen from this figure the cross section has a mid-channel navigational depth of
NAP – 16,10 m.
Figure 2.1 Westereems cross section near the crossing location of Cable
At the location of the crossing between the Cable and the Westereems, the present
shipping channel will be deepened (and afterwards maintained) from a depth of
approximately NAP – 15,40 m to a navigational depth of NAP -16,10 m. to facilitate the
passage of bulk carriers.
To guarantee this navigational depth, which will be the presented depth (in LAT) on the
Admiralty charts, the shipping channel will be dredged by RWS to a depth of NAP-16,60
m plus a dredging tolerance. This tolerance is set to be 0,50 m. Thus in practice the
dredging work for the navigational depth has to be expected to be down to a level of NAP
-17,10 m.
The centre of the Westereems will be deepened over a (toe to toe) width of 200,00 m.
The side slopes in the RWS dredging design of the Westereems Deepening are 1 in 10
Vertical to Horizontal.
For the two banks, each 184,00 m wide, the depth level (NAP -12,00 m in Figure 2.1) will
be maintained for car carriers. The total width of the profile is 650,00 m.
Since the present depth of the Westereems at the location of the crossing with the Cable
is in the order of NAP -15,40 m, these banks will not require any dredging at this specific
location.
Document1 Date 7/31/2017
Page 10 of 27
Specification and Scope of Work for
Lowering the
NorNed power cable at Westereems Shipping Channel
and
Remedial Burial of the NorNed
power cable along the cable route
Therefore dredging for the deepening of the Westereems navigational channel at the
Cable crossing will be limited to the 200.00 m wide “centre” channel and its 1:10 side
slopes.
Bathymetry and Cable profile data as used in the pre-design can be found in Negometrix
attached files for Contractor’s information and as presented in Appendix 9.
2.1.2 Cable DoB
The seabed profile over the Cable crossing area, including the adjacent areas where
dredging operations most likely have to be performed, is taken from the 2007 survey and
is presented in Appendix 2
Tenderers will moreover be supplied with the latest DoB data of the Cable of the May
2015 survey, as soon as these data become available.
Reference is made to the pre-design drawings in Appendix 2: 0316_TT_LSS_0001 and
0316_TT_LSS_002 in Appendix 2, presenting plan view, longitudinal profile and a cross
section of the Cable.
The relevant cross profile of the deepened Westereems for the Cable crossing is taken as
per RWS design drawings profile “dwarsprofiel A”, see Figure 2.1 above, as that is the
cross profile closest to the Cable crossing location.
The table below presents the levels of Westereems and the Cable.
Actual depth Westereems
NAP – 15,00 m to -15,70 m
Depth at the crossing
location
Future nautical depth
NAP – 16,10 m
Over a width of 200,00 m
(toe to toe)
Current depth
Cable
NAP – 16,60 m – up to 17,90 m
RWS dredging tolerance at
Cable crossing
+/- 0,50 m
New maximum physical
depth Westereems at
Cable crossing
NAP – 17,10 m
= Dredged depth: 16,10
m
+ over depth of 0,50 m
+ tolerance of 0,50 m
New design depth
Cable (top of cable)
NAP – 19,10 m
3,00 m below NAP -16,10
m
Table 1 Depths
Document1 Date 7/31/2017
Page 11 of 27
Specification and Scope of Work for
Lowering the
NorNed power cable at Westereems Shipping Channel
and
Remedial Burial of the NorNed
power cable along the cable route
2.1.3
Design of the longitudinal cable profile
The Cable Lowering campaign will take place prior to the Westereems deepening
campaign which will be performed by Third Parties (and commissioned by RWS).
In anticipation of this Westereems deepening campaign the Cable shall be lowered to
such a level that the drag head of the trailing suction hopper dredger, will stay clear of the
top of the Cable by 3,00 m.
The future nautical depth of the section of the Westereems at the crossing with the Cable
is NAP – 16,10 m and the width of 200,00 m (toe to toe). The maximum dredging depth
including over dredging and dredging tolerances is NAP -17,10 m.
The Cable (top of cable) shall be buried at least 3,00 m below the nautical depth over the
full width of the Westereems shipping channel.
For the deepening of the Westereems the Cable is to be lowered at least over the approx
200,00 m section where the Cable coincides with the dredging profile for the
Westereems.
It is assumed in order to be able to lower the Cable to its future depth, dredging/MFE-ing
has to be performed over a length of around 750,00 m along the cable (375,00 m either
side of the Cable). This distance is assumed to be required for creating sufficient over
length in the Cable thereby facilitating the Lowering process.
Please refer to the drawing in Appendix 2 where these ranges can be seen.
The chainages as used in Appendix 2 are defined along a straight line between the
following 2 points (here stated in RD coordinates, project coordinates will be in ED50UTM-31N) :
No
Chainage 0.0000 m
Chainage 951.985 m
RD X
221972.43
221908.71
RD Y
625396.68
626346.51
The centre line of the Cable deepened profile is defined as follows points (here stated in
RD coordinates, project coordinates will be in ED50- UTM-31N):
No
RD X
RD Y
Bathy
(2010)
T1 221965.70
W1 221947.82
W2 221941.84
625496.46
625755.84
625855.89
-14,40
-15,20
-15,30
W3 221935.91
T2 221916.63
625955.92
626246.82
-15,40
-14,50
Document1 Date 7/31/2017
Cable
Profile Remark
(situation design
assumed)
-17,10
-17,10 Start transition in
-16,90
-19,40 Toe line dredged channel
-17,70
-19,40 Cable crossing centre
line Westereems
-17,90
-19,40 Toe line dredged channel
-17,60
-16,40 End transition out
Page 12 of 27
Specification and Scope of Work for
Lowering the
NorNed power cable at Westereems Shipping Channel
and
Remedial Burial of the NorNed
power cable along the cable route
Figure 2.2 presents the 3D view of the conceptual pre-design of Cable Lowering at the
Westereems and Figure 2.3 presents the plan view of the pre-design. The presented predesign is assuming an open trench with the Cable in the middle.
Figure 2.2 Pre-Design of envisaged dredging profile of the Cable at the Westereems Shipping Channel
Figure 2.3 Plan view of the conceptual design, with in black the contours of the Westereems deepening profile as per RWS
design profile “Dwarsprofiel A” (ref. Fig. 2.1).
Document1 Date 7/31/2017
Page 13 of 27
Specification and Scope of Work for
Lowering the
NorNed power cable at Westereems Shipping Channel
and
Remedial Burial of the NorNed
power cable along the cable route
The purpose of the presented pre-design is to provide information regarding quantification
of the extents and volumes of the Lowering operations when executed by dredging.
In case of dredging activities over the Cable, TenneT has not decided yet whether
mechanical backfilling is required.
Contractor is requested to (preliminary) engineer a safe and efficient solution to lower the
Cable at the crossing location with the Westereems. The presented pre-design is to be
considered a possible approach. Alternatives to the presented approach are requested
and welcomed explicitly.
2.2
Remedial Burial of the Cable along the cable route
Remedial Burial of the Cable as described in the Scope of Work in areas along the cable
route, listed in Appendix 7 below and envisaged for Remedial Burial Works.
The purpose of the Remedial Burial of the Cable is to obtain a safe and stable position of
the Cable at the required DoB over a considerable period of time.
The depth of cover of the Cable in the areas to be remedially buried, is of such a
magnitude that Remedial Burial of the Cable can be ideally executed by MFE techniques
and no additional dredging is foreseen.
Contractor has to be aware of the fact that the areas of the Remedial Burial Works lies in
a channel between sand banks and Contractor should plan his Remedial Burial Works
properly in order to avoid unnecessary down time.
Document1 Date 7/31/2017
Page 14 of 27
Specification and Scope of Work for
Lowering the
NorNed power cable at Westereems Shipping Channel
and
Remedial Burial of the NorNed
power cable along the cable route
3 SCOPE OF WORK
3.1
Lowering Operations of the Cable in the Westereems (Part 1)
This section specifies the Scope of Work for the Lowering campaign of the Cable in the
Westereems.
With regard to the manner in which the Lowering operation has to take place, TenneT has
in principle considered the use of Lowering the Cable by combined dredging and Mass
Flow Excavation (MFE). This last technique has shown good results in the past in areas
with suitable seabed conditions, i.e. sandy soils.
However, if Contractor has a, in his opinion, viable alternative, he is free to propose such
an alternative. In doing so Contractor has to keep in mind, that at no time physical contact
is allowed with the Cable and all burial work has to be carried out at a minimum safe
distance of 2,00 meters away from the Cable. Contractor shall moreover have to
demonstrate his experience in the protection by burial of live subsea cables or pipelines
by his proposed technique and/or method and is subject to a Lowering trial in order to
demonstrate compliance with Tennet's requirements.
The Scope of Work of the Lowering operation shall include, but is not limited to:
1. Familiarization with and acknowledgement of existing survey data and identification
of the environmental conditions in the Westereems crossing area.
2. Perform all necessary detailed engineering and planning of the complete Lowering
Work. Provide organigram and CVs of proposed key personnel
3. Draft and issue project specific HSE plan and relevant operating procedures for the
Lowering Work
4. Workability specifications, adverse weather procedures, bridging document etc.
5. Preparation of schedule
6. Preparation of pre-works deliverables, such as work methodology.
7. Hazop, Pre-ops meeting and SJA
8. Installation wave rider buoy and current meter.
9. Provide facilities for the Marine Warranty Surveyor (if applicable)
10. Provide facilities for two (2) TenneT Representatives
11. Mobilization and calibrations, inclusive of all equipment acceptance tests.
12. Pre-Lowering Works survey (Bathymetric).
13. Demonstrate the correct functioning of the CT device.
14. Lowering trial, if required or applicable.
15. Lowering of the Cable, monitoring the process with intermediate surveys
(Bathymetric and DoB) and As-built survey (Bathymetric and DoB).
16. Demobilization.
17. Post-works reporting and final results.
During the Works a Guard Vessel maybe on site if required by the authorities, to warn off
other shipping traffic. In case the Guard Vessel is required, it will be provided by
Contractor.
Document1 Date 7/31/2017
Page 15 of 27
Specification and Scope of Work for
Lowering the
NorNed power cable at Westereems Shipping Channel
and
Remedial Burial of the NorNed
power cable along the cable route
3.2
The envisaged Remedial Burial operations (Part 2)
The Cable route from KP 0 to KP 57 passes through an area with a very dynamic shifting
seabed. Earlier Remedial Burial Works (2012) by means of Mass Flow Excavation have
for the greater part shown good results. However the seabed has in the meantime shifted
to such an extent, that Remedial Burial is once again required in some areas.
The Cable shall be remedially buried by Contractor to the specified DoB whereby it
should be noted that between KP 0 and KP 40 the DoB shall be at least 2,00 m.
according to the permit and moreover in the following sections the target DoB shall be
even 3,00 m:
1. At the entrance to the Eemshaven harbour (KP 2.5 - KP 3.6),
2. In the crossing of the Hubertgat fairway (KP 35.5 – KP 36.5),
3. Between KP 19 and KP 22,
4. Between KP 23.6 and KP 24.1,
and as is indicated in Appendix 7 (total scope/length to be defined between 8,7 to 13,1
km) .
Remedial Burial tolerances:
 for the area with the 2,00 m burial requirement, the lower tolerance is 0,00 m
(zero) and the higher tolerance is 1,00 m (i.e. max DoB at 3,00 m),
 for the area with the 3,00 m burial requirement the tolerance is +/- 0,20 m.
With regard to the manner in which the Remedial Burial has to take place, TenneT has as
mentioned before in principle considered the use of Remedial Burial by Mass Flow
Excavation (MFE).
However, if Contractor has a, in his opinion, viable alternative, he is free to propose such
an alternative. In doing so Contractor has to keep in mind, that at no time physical contact
is allowed with the Cable and all burial work has to be carried out at a minimum safe
distance of 2,00 meters away from the Cable. Contractor shall moreover have to
demonstrate his experience in the protection by burial of live subsea cables or pipelines
by his proposed technique and/or method and may be subject to a Remedial Burial trial in
order to demonstrate compliance with Tennet's requirements..
The purpose of the Remedial Burial is to remove the soil around the Cable area in such a
way that the Cable ultimately sinks lower into the seabed to its specified depth. When the
Cable has been (re-)buried to the specified depth it shall be evenly supported by the
seabed at the bottom of its trench. During the Remedial Burial operation it is likely that
trench sedimentation takes place in the excavated area and which shall be taken into
account by Contractor.
The areas in which the Cable has to be remedially buried, is shown in Appendix 7.
Document1 Date 7/31/2017
Page 16 of 27
Specification and Scope of Work for
Lowering the
NorNed power cable at Westereems Shipping Channel
and
Remedial Burial of the NorNed
power cable along the cable route
The items of the Scope of Work are similar to the one for the Lowering operation and
shall include, but not limited to:
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
16.
17.
Familiarization with and acknowledgement of existing survey data and identification
of the environmental conditions in the Westereems crossing area.
Perform all necessary detailed engineering and planning of the complete Remedial
Burial operation. Provide organigram and CVs of proposed key personnel
Draft and issue project specific HSE plan and relevant operating procedures for the
Remedial Burial operation
Workability specifications, adverse weather procedures, bridging document etc.
Preparation of schedule.
Preparation of pre-works deliverables, such as work methodology.
Hazop, Pre-ops meeting and SJA
Installation wave rider buoy and current meter.
Provide facilities for the Marine Warranty Surveyor (if applicable)
Provide facilities for two (2) TenneT Representatives
Mobilization and calibrations, inclusive of all equipment acceptance tests.
Pre- Remedial Burial Works survey (Bathymetric).
Demonstrate the correct functioning of the CT device.
Remedial Burial trial, if so required by TenneT.
Remedial Burial of the Cable, monitoring the process with intermediate surveys
(Bathymetric and DoB) and As-built survey (Bathymetric and DoB)
Demobilization
Post-works reporting and final results.
It has not been envisaged that a Guard Vessel will be required during the Remedial Burial
Works. However, if so required by the Authorities, the Guard Vessel will be provided by
Contractor.
3.3
Planning
It is TenneT’s intention to start the Works soon after contract award and Contractor will
finalize the Works for Part 1 latest December 2016, and Part 2 latest May 2016.
All design documents of Contractor shall be finalized and approved by TenneT and MWS
minimum 8 weeks before start of execution, in order to obtain the necessary licenses and
permits. It is the intention of TenneT to start up the licenses process after contract award
based on the pre-design documents (e.g. Method Statement) delivered by Contractor.
Document1 Date 7/31/2017
Page 17 of 27
Specification and Scope of Work for
Lowering the
NorNed power cable at Westereems Shipping Channel
and
Remedial Burial of the NorNed
power cable along the cable route
4 DETAILED REQUIREMENTS
4.1
General
The detailed requirements are the same for both Lots, i.e. the Lowering operations as
well as the Remedial Burial operations (is seen as "Lowering") as follows:
4.2
Familiarization with existing Survey data and identification of environmental
conditions
TenneT will provide historic as well as recent survey data after Contract award.
Contractor shall familiarize himself with the survey and soil data that will be provided by
the TenneT after Contract award. In addition Contractor shall identify the environmental
conditions in the Westereems crossing area such as wind, waves, current and tide.
4.3
Perform detailed engineering and planning
Contractor shall perform all the necessary engineering and planning for the Lowering and
Remedial Burial campaigns. The plans shall include extensive engineering and relevant
calculations of the forces produced by the Subsea Excavation Equipment on the Cable
whilst operating. TenneT shall liaise, through TenneT, with the MWS for acceptance of
the thus presented design (e.g. forces). Full cooperation and obeying the MWS’
overruling advice during the tender stage as well as during the execution of the Works is
imperative for both TenneT and Contractor.
Acceptance (certificate of approval) of these documents by MWS and TenneT is
imperative before any Works can commence.
Moreover, engineering and planning shall specifically include a lay-out of the survey and
monitoring equipment as well as method statement for the uses thereof clearly showing
how the Works will be monitored. An organigram and CV's of proposed key personnel will
be required at this stage as well.
4.4
Issue of project specific HSE Plan
Contractor shall draft and issue a comprehensive HSE plan and relevant operating
procedures (incl. adverse weather procedure and bridging document) that clearly
demonstrate its ability to establish all necessary safety procedures and routines and to
take all necessary precautions in connection with the safe performance of the Works.
4.5
Preparation of time schedule
Contractor shall produce a time schedule for the Lowering campaign. With this time
schedule Contractor shall describe his workability, i.e. what his limitations are with regard
to wind, wave and current for his operations and present it according to Appendix 8
Workability Matrix.
4.6
Preparation of pre-works deliverables
The pre-works deliverables for the Lowering campaign shall be as follows:
1. Mobilization Plan
2. General methodology plan incl. but not limited to Survey, Calibrations, especially
CT operations.
Document1 Date 7/31/2017
Page 18 of 27
Specification and Scope of Work for
Lowering the
NorNed power cable at Westereems Shipping Channel
and
Remedial Burial of the NorNed
power cable along the cable route
3. Workability analysis defining safe working limits, i.e. H-sign., wind speed, current,
station keeping capability plots, for Lowering Equipment near the Cable (see also
4.5 above and Appendix 8).
4. Turbidity analysis/monitoring (optional to be advised by TenneT incl. price
quotation)
5. Lowering trial procedure (if required) in an area indicated by TenneT, but in any
case close to the actual Lowering area.
6. Lowering procedures, including Lowering plan (defining number of passes), and
contingencies.
7. Project Risk Analysis (RA).
8. Vessel operations procedure, possibly including Guard Vessel coordination
operations.
9. Quality Control Plan (QC).
10. Communication plan.
11. Schedule of activities.
4.7
Hazop, pre-ops meeting and SJA
Contractor shall conduct a Hazop and pre-ops meeting on the basis of the
aforementioned deliverables. A Safe Job Analysis (SJA) shall be done shortly before the
execution of the Works or in the event a Lowering trial is required, before the start
thereof.
4.8
Installation wave rider buoy and current meter
Contractor shall install a wave rider buoy and a current meter on site during all Lowering
Works and make logged data available to TenneT (also on-line) for workability analysis
purposes. TenneT shall have to agree beforehand on the locations, proposed by
Contractor, for the wave rider buoy and current meter.
4.9
Facilities for TenneT (Marine Warranty Surveyor and TenneT
Representatives)
The Contractor shall provide the following facilities for one Marine Warranty Surveyor (if
applicable) and two (2) TenneT Representatives:
 Transportation to and from the offshore site, if applicable.
 Lodging in single cabins to senior crewmember standard as well as messing.
 Office facilities, such as desks, lockable drawers, properly working internet
connection, (sat)phone, office stationary.
 Screens to monitor operations
4.10 Mobilisation and calibrations
The mobilization shall include all equipment calibrations and associated documentation.
These calibrations will be witnessed by the onboard TenneT Representative.
Acceptance of these items by TenneT is imperative for before any Works can commence.
The mobilization acceptance tests shall include but not be limited to:
1. Wet test of Lowering equipment, incl. peripherals operational and interfaced to
surface equipment.
2. Survey equipment: Multi-Beam Echo sounders, Cable Tracker (CT) fully
operational and calibrated.
3. Vessels MFE and dredging equipment sensors calibrated and fully functional
4. USBL system(s) fully operational and calibrated.
5. Calibration of wave and current measuring equipment.
Document1 Date 7/31/2017
Page 19 of 27
Specification and Scope of Work for
Lowering the
NorNed power cable at Westereems Shipping Channel
and
Remedial Burial of the NorNed
power cable along the cable route
6. Positioning of subsea Lowering equipment fully calibrated.
7. Provide real time CT displays of cross profiles showing the cable superimposed
on an image of the seabed
8. Fully operational survey system including vessel’s survey sensors, Visual soft
system
4.11 Pre-Lowering Works survey
Contractor shall conduct a bathymetric survey for its own (DTM) use prior to any Lowering
Works.
The requirements for the surveys are as follows:
1. Contractor shall operate a subsea sensor for monitoring the position of the
Cable during the Lowering campaign, whereby it should once again be noted
that no signal (tone) can be provided on the Cable.
2. Accurate Lowering survey with multiple MBE systems, positioned in such
locations on the vessel that a “before” and “after” position of the Cable, visible
on the monitors, can be established and recorded.
3. Accurate DoB survey using CT equipment for the Lowering campaign.
4. The sampling interval for DoB survey shall be 1,00 m or less along the Cable.
The accuracies for the survey shall be as listed below or better:
1. Bathymetric survey:
2. DoB survey:
3. MBE corridor width:
2 sigma (X,Y,Z) < 20,00 cm.
max.10% of burial depth, (X,Y) < 20,00 cm.
50,00 m either side of route.
4.12 Lowering trial
Prior to any Lowering Works near the Cable a trial shall be performed, if so required by
TenneT. This trial shall be performed parallel to the cable route at a minimum distance of
50,00 m from the Cable, where the present water depth is around 13,00 meters.
The aim of this trial is to demonstrate:
1. The subsea accuracy and effectiveness of the Subsea Excavation Equipment.
2. Station keeping capability of the Excavation Spread in the ambient tidal currents.
3. Ability of the Subsea Excavation Equipment to produce a small trench to the depth
of NAP – 19,40 m over a minimum length of 10,00 meters at the trench bottom.
4. To measure siltation of the trial trench and estimate siltation of the Cable trench as
well as providing an estimate of the siltation i.e. the decrease in the navigational
depth of the shipping channel as a result of the excavation Works.
All of the above to be proven by online and offline survey data in order to facilitate
hardcopy proof of the trial work done as well as showing the installed survey suite’s
capability to deal with the specifics of the project.
Document1 Date 7/31/2017
Page 20 of 27
Specification and Scope of Work for
Lowering the
NorNed power cable at Westereems Shipping Channel
and
Remedial Burial of the NorNed
power cable along the cable route
4.13 Lowering of Cable and intermediate surveys
The Contractor shall deepen the Cable whereby bottom of the Cable will rest at a
minimum depth of NAP – 19,40 m.
The longitudinal profile of the Cable shall be along the lines of TenneT provided
preliminary design, which is described in Appendix 2 of this document.
The Lowering shall be carried out in accordance with the following tolerances:
1. Lower tolerance: design depth.
2. Deeper tolerance: design depth + 0,50 m.
When the Cable has been deepened to the design depth it shall rest evenly supported by
the seabed. The dredged spoil shall be displaced in such a manner that it shall not cause
reduction of the navigational depths in the shipping channel. A dumping area will be
indicated by TenneT and as was instructed by the Authorities.
Therefore Contractor shall:
1. When working on the Cable, Contractor will work in a safe manner, e.g. working at
all times “below” the ambient tidal current with his Lowering tool, e.g. drag/MFE
head, so that in the event of a black-out or other calamity on the Excavation
Spread a safe drift-off situation will exist.
2. Operate a system that continuously monitors and shows the xyz position of the
Subsea Excavation Equipment to the Cable location during the Lowering process.
Accurate Lowering survey with multiple MBE systems, positioned in such locations
on the vessel that a “before” and “after” position of the Cable, visible on the
monitors, can be established and recorded. During operations strictly adhere to
the procedure of monitoring “live” the effects of his Lowering technique, e.g. mass
flow excavation, by means of multiple MBE monitoring and recording of the Cable
position.
3. Accurate DoB survey using CT equipment for the Lowering campaign.
4. The sampling interval for DoB survey shall be 1,00 m or less for the Lowering in
the Westereems and 10,00 m for the Remedial Burial along the cable.
5. Detail how he plans to monitor the actual data from the wave rider buoy and the
current meter in order to predict his workability and position of the excavation
equipment, such that avoidance of any contact with the Cable is guaranteed at all
times.
6. Adhere to the minimum bending radii at all times.
7. Be able to demonstrate that the Cable has been lowered to the specified
contractual depth.
The intermediate and (draft) as-built survey results shall be presented to TenneT
representative within 6 hours after survey for preliminary approval.
4.14 Demobilisation
After TenneT representative has approved the preliminary as-built survey, TenneT
Representative shall issue a Taking-Over Certificate to Contractor, where after Contractor
can commence with the demobilization from site. The demobilization of the Guard vessel
shall be taken care of by Contractor after consultation with TenneT
Document1 Date 7/31/2017
Page 21 of 27
Specification and Scope of Work for
Lowering the
NorNed power cable at Westereems Shipping Channel
and
Remedial Burial of the NorNed
power cable along the cable route
4.15 Reporting and final results reporting
4.15.1 General
The requirements for the reporting and of the final results are as follows:
1. Provide draft Lowering Report including (TenneT provided format) charts, tabular
format results etc. for comments to TenneT. Thereafter the final agreed upon
Lowering Report shall be prepared and submitted to TenneT in both hard copy
and electronic medium to be specified by the TenneT for review.
2. Evaluation and Close Out Report.
3. Provision to TenneT of a twice daily weather report by a TenneT approved
meteorological institute/service.
4. During operations, provision to TenneT of a Daily Progress Report comprising of,
but not limited to:
a. date of report and report number.
b. ancillary vessels and their locations.
c. personnel on board.
d. Toolbox meetings and drills.
e. event log for working, stand by (weather, in port etc), transit, mechanical
breakdown, for the day as well as cumulative, etc.
f. planned work for next 24 hours.
g. incident reporting (including LTIF)
5. A Field report shall be submitted after the operations.
The first Daily Progress Report shall be issued at the commencement of the mobilization.
4.15.2 Data formats
1. Alignment Charts according to TenneT provided examples (including historic
data).
2. All DTM’s in both 1 x 1 m and 0,25 x 0,25 m grid not exceeding 50 MB.
3. Tabular format (min. every 5,00 m.) of Cable DoB and bathymetry results
(including final and pre-works results).
Tabular results and DTMs from MBE/CT surveys shall be (draft) delivered onboard in
(Easting Northing Elevation) ASCII text files and shall be gridded to both 1 x 1 m and 0,25
x 0,25 m.
4.15.3 Charts
The results from the survey shall be (draft) presented onboard on alignment sheets,
which will have the same format as the attached chart examples.
The historic data present on the alignment sheets will be provided at Contract award.
An overview chart, with larger scale charts (scale to be determined by the TenneT) shall
be presented for Westereems Crossing area or other areas of particular interest upon
request.
Charts shall be delivered in DWG and PDF formats.
Document1 Date 7/31/2017
Page 22 of 27
Specification and Scope of Work for
Lowering the
NorNed power cable at Westereems Shipping Channel
and
Remedial Burial of the NorNed
power cable along the cable route
4.15.4 Coordinate format requirements
All final charts and data shall be supplied in both RD and UTM 31N-ED’50 format. Vertical
reference shall be in NAP.
Cable transformation parameters (WGS’84 to UTM 31N-ED’50 will be supplied by
TenneT)
4.15.5 Visual soft requirement
Contractor shall supply Online Video including navigation (Node, KP, E, N, Z, date, time,
depth) data for SSS / MBE / CT Subsea equipment / Navigation displays, which shall be
stored in a VisualSoft database for TenneT’s review with Visual Review software. Online
commentary shall also be recorded when applicable.
TenneT will advise which video needs to be logged.
Delivery shall be on separate dedicated (min. USB 3.0) hard disks, sub-folders KP-named
and divided into segments not exceeding 30 minutes recording time.
Document1 Date 7/31/2017
Page 23 of 27
Specification and Scope of Work for
Lowering the
NorNed power cable at Westereems Shipping Channel
and
Remedial Burial of the NorNed
power cable along the cable route
5 ADDITIONAL REQUIREMENTS
5.1
Marine operations
Since Westereems is a shipping channel Contractor shall not block the channel as to
guarantee the free and safe passage of all marine traffic during the execution of the
Works.
Contractor shall request a permit, under the "scheepvaartreglement Eemsmond", from the
shipping authorities for the Work.
Contractor shall be responsible for the communications and complete liaison with other
marine traffic and VTS EMS, including any special permits that may be required for
working in this shipping channel..
Prior to commencement of the Works Contractor shall submit a description of the Works
to VTS EMS. Contractor shall provide VTS EMS with daily nautical information through
the designated VHF channel. (as described in permit(s))
During the campaign(s) Contractor shall have a Guard Vessel on site (option in Contract).
This Guard vessel shall be of a standard acceptable by the Dutch and German
Authorities. Contractor is responsible of communicating his intentions with regard to his
work and position with the Guard Vessel and jointly advise her position as to optimize the
results of the guard duties.
5.2
Environment
The Lowering site is located near Natural Park Waddenzee, which is environmentally
sensitive. Contractor shall abide by all Marpol regulations in force, as well as with the
local and country (Dutch , German) specific regulations which are applicable.
This is a shallow water area where the tidal current velocities can be very high and there
is a significant tidal range as well.
5.3
Permits
TenneT will arrange, and be responsible for Permits and Licenses to be acquired as
owner of the Cable. Applicant will arrange and be responsible for all other (working)
Permits and Licenses.
Wasser- und Schifffahrtsamt Emden
Dipl.-Bauingenieur Jens Memmen
Am Eisenbahndock 3
26725 Emden
Contact:
Tel: +49 4921 802 331
Fax: +49 4921 802 379
Mobiel: +49 160 745 80 42
[email protected]
Rijkswaterstaat Noord Nederland
Afdeling Handhaving
Mevr. Jeltje de Groot
Postbus 2301
8901 JH Leeuwarden
Tel: +31625141989
Document1 Date 7/31/2017
Page 24 of 27
Specification and Scope of Work for
Lowering the
NorNed power cable at Westereems Shipping Channel
and
Remedial Burial of the NorNed
power cable along the cable route
6 INFORMATION
6.1
Properties of the NorNed HVDC Cable
The Cable at this crossing section is the Flat Mass Impregnated (FMI) cable.
The main FMI cable properties are presented in Appendix 3, Cable properties.
6.2
Soil and morphology
The actual Cable position is influenced by the morphological behavior of the seabed,
such as sedimentation/erosion and moving sandwaves. Reference is made to document
“29928 Route Update 1999” in Appendix 4.
For borehole information reference is made to Appendix 5 : Borehole information
A summary has been presented below.
A Soil Investigation in connection with the widening and Lowering of the
Westereems has been executed in the spring of 2011.
Four boreholes 1A, 2A and 1B and 2B have been added to the originally planned
number of boreholes in connection with the envisaged repositioning of the Cable
to a lower level.
This summary aims to aid to the comprehension of the report for readers who
might have difficulty with the Dutch language.
The 4 boreholes made by means of a vibratory coring apparatus in the vicinity of
the crossing have reached a depth of respectively -20,23 -19,67 -20,05 and 19,86 m relative to NAP.
A description of the samples and pictures of the opened liners can be found in the
report. Please note that the maximum penetration depth of the corer has not been
reached.
All 4 boreholes show silty sand layers locally intersected by thin clay layers. Shell
debris is often present. The carbonate content of the material varies.
Laboratory tests include granulometry curves of samples. These can be made
available on request.
Mini CPT tests have been performed at some distance from the crossing. The
interpretation of the measured values, according to the writer(s) of the report,
should be done with caution. This applies especially to the relative density values.
However the friction coefficient found in all tests points to a continued presence of
sand to a depth of 24,00 m below NAP.
6.3
Cable Route
Theoretical (as-planned) route coordinates are to be found in Appendix 6. Actual as found
Cable location to be supplied after receiving the results of the planned May 2015
Bathymetric / SSS/ DOB survey.
Document1 Date 7/31/2017
Page 25 of 27
Specification and Scope of Work for
Lowering the
NorNed power cable at Westereems Shipping Channel
and
Remedial Burial of the NorNed
power cable along the cable route
List of Appendices 1 - 9
Appendix 1
Drawings “Tracébesluit RWS Project 9S4530.A0 –
Appendix 2
Positions trench pre-design crossing and crossing example
Appendix 3
Cable properties
Appendix 4
Document “29928 Route Update 1999”
Appendix 5
Borehole information
Appendix 6
Route position list “N 0219 J W8-TW-G_20070124 - NorNed RPL”
Appendix 7
Areas envisaged for remedial burial
Appendix 8
Workability Matrix
Appendix 9
Bathymetry and cable position list over crossing area.
Document1 Date 7/31/2017
Page 26 of 27
Specification and Scope of Work for
Lowering the
NorNed power cable at Westereems Shipping Channel
and
Remedial Burial of the NorNed
power cable along the cable route
Appendix 10 : PRICING SCHEDULE
Preliminary proposed schedule to be used in tender stage where a total of 3 pricing
scenario's will be requested :
 Part 1 as stand alone
 Part 2 as stand alone
 Part 1 and Part 2 in one campaign
For commercial and Contractual principles reference is made to prequalification criteria.
 All prices shall be quoted in Euro
 All prices shall exclude Value Added Tax
Scenario Part 1
Name of Vessel
Scheduled
duration in days
n.a.
n.a.
n.a.
n.a.
Description of Lumpsum activity (detailed per VOO)
Project management and engineering & Preparation of pre-works
deliverables
Mobilisation and Calibrations (specify)
Conversion Rate
Demobilisation
Reporting and submission of final Results
a)
Description of day rate activity (detailed per VOO)
Name of Vessel
SubTotal
Lumpsum
Scheduled
duration in days
Lumpsum in
Euro
Pre-Lowering Works survey
Working (specify workability)
Stand-by on site or in Eemshaven
Transit
Lowering trial & Lowering of Cable cable and intermediate
surveys
Working (specify workability)
Stand-by on site or in Eemshaven
Transit
Provision and installation of wave rider buoy, current meter, tide
gauge
Provision of Guard vessel (option)
Turbidity measurement during the Works (option)
b)
Sub Total
Dayrates
Target Budget
(a + b)
Other Commercial Conditions
Percentage
Contractors share in underrun of target budget will be
Contractors day rates will, in case of budget overrun, be
reduced with
Mark-up on Sub-contracts will be
Document1 Date 7/31/2017
Page 27 of 27
Day rate in Euro