MONITORING & EVALUATION of BLYTH OFFSHORE WIND FARM INSTALLATION & COMMISSIONING ETSU W/35/00563/REP/1 DTI/Pub URN 01/68

MONITORING & EVALUATION OF BLYTH OFFSHORE WIND FARM

INSTALLATION & COMMISSIONING

ETSU W/35/00563/REP/1

DTI/Pub URN 01/686

Contractor AMEC Border Wind Prepared by L Pepper

The work described in this report was carried out under contract as part of the New and Renewable Energy Programme, managed by ETSU on behalf of the Department of Trade and Industry. The views and judgements expressed in this report are those of the contractor and do not necessarily reflect those of ETSU or the Department of Trade and Industry.

First published 2001 © Crown copyright 2001 This is the first of seven reports to be published on specific areas covered by the monitoring and evaluation of the Blyth offshore wind farm project. The purpose of the reports is to evaluate and review the practical aspects of installation, access, operation and maintenance of the first UK offshore wind farm.

The other reports are as follows:

NAVAID Requirements for Offshore Wind Farms W/35/00563/REP/2 Review of Capital Expenditure W/35/00563/REP/3 Health and Safety Guidelines W/35/00563/REP/4 Review of Operational Costs W/35/00563/REP/5 Review of Operational Aspects W/35/00563/REP/6 Review of Wind Turbine Technical Performance W/35/00563/REP/7

The overall planned duration for this monitoring and evaluation project is 24 months. EXECUTIVE SUMMARY

1) THE AIM AND OBJECTIVES OF THE WORK

The principle aim of this report is to appraise the practical aspects of installation and commissioning of the offshore wind farm. The construction and installation activities of the project were monitored and reviewed by the project team to enable recommendations for future larger projects to be made.

This report particularly looks at how the project progressed against the construction and installation schedule with regard to weather conditions and operational procedures. The document not only describes the methods of installation, assembly and cable laying, but also reviews the effectiveness of those methods including any difficulties that were encountered and the solutions that were found.

2) OVERVIEW OF THE PROJECT

The wind farm off the coast of Blyth, Northumberland, is the first offshore wind farm to be built in the United Kingdom. Two 2 MW wind turbines have been installed at a distance of approximately 1km from the coast, in a water depth, at low tide, of about 6m with a tidal range of approximately 5m. The completed project is the first in Europe to be exposed to the full force of the North Sea weather as well as a significant tidal range. The site is also subject to breaking waves.

The site location is on a submerged rocky outcrop. A chart showing the location of the turbines and the cable route is in Appendix A. Each wind turbine has been erected onto a steel pile (monopile) that was drilled and grouted into the rock. The 3.8m diameter holes for the pile were drilled from a jack-up barge (the Wijslift), and the pile lifted off the supply barge by the crane on the jack-up barge and allowed to sink into the drilled socket. The monopile was then grouted into position and allowed to cure. When it had been confirmed that the monopile was secure in the hole, the sequence of erection was tower, nacelle and finally the rotor with the three blades attached.

The site has the benefit of all the consents required for the installation of the turbines. An Environmental Assessment was produced and detailed site investigation studies were carried out and evaluated in order to complete the detailed design of the structure.

The Blyth Offshore Wind Farm has been developed by Blyth Offshore Wind Limited, a joint venture company between Powergen Renewables, Shell, Nuon and AMEC Border Wind. The diversity of experience and skills within these organisations has been brought together to pioneer the first project in what promises to be a new and exciting industry for the UK.

1 3) SUMMARY OF WORK CARRIED OUT

The basic gantt chart below shows the planned activities against the actual activities, highlighting the delay to the start of installation and the effect that it had on the tasks that were linked to it. The delay in starting installation was primarily due to bad weather, particularly high winds and stormy seas. Limiting factors were set and during installation lifting operations could only take place on site when the wind speed was 8m/s or less and the swell no greater than 0.5m. If the weather conditions were not within the limits then the installation operations had to be postponed until improved conditions were forecast.

Gantt Chart Showing Actual v Planned Activities

2000 ID Task Name Dec Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec 1 Joint Venture Agreement 100% 2 Main Contracts in Place 100% 3 Turbines Delivered 0 100% 4 Monopiles Delivered P 100% 5 Modifications to Wijslift 100% 6 Turbine Installation 100% 7 Cable Laying 100% 8 G59 Test I 100% 9 Commissioning 1 00'

Key I i = Planned

Actual

The Gantt chart summarises the work that was carried out into 9 main areas, the full details of which are given in the main body of this report. The chart shows the difference between the planned and actual timings of the installation and commissioning activities.

Some changes were made to the planned procedures: namely the blade lifting procedure, and the route of the cable connecting the wind farm to shore. The biggest issue of all was the weather. This was always going to be an issue and obviously could not be relied upon.

Installation had been planned for the summer months in the hope of reducing the possibility of bad weather unfortunately the weather did not meet expectations. Many of the installation procedures could only be carried out in

11 very low swell and low winds. There were no solutions to the weather problems other than to constantly monitor weather forecasts and be ready to go whenever conditions were suitable.

4) CONCLUSION

In conclusion the installation and commissioning of the Blyth Offshore wind farm has highlighted many implications that should be taken into consideration for future offshore wind farms. The four major ones are discussed briefly below and in more detail in Section 6 of the report. In general terms future project teams should review their methods and operations throughout the installation and take into account and act on any lessons learned.

Installing a larger offshore wind farm would not require any more personnel than were involved on the Blyth Offshore project, if anything fewer people may be needed if the pile foundations are driven in, instead of drilling and grouting them in place. Fewer people are involved in pile driving operations and it also takes less time to drive a pile foundation in than to drill a hole, install the pile and grout it in place. However, the other aspect to consider is if two lots of equipment (2 x crane barge and flat barge) were used then obviously twice as many people would be needed and it would in theory take half the time.

4.1 Equipment

For future larger projects further offshore it would be preferable to have a crane barge that can jack up above the swell to lift and install the pile foundations and the turbine components, and a flat barge that could also be jacked up during lifting operations, to transport the components to site. The advantage being that if the barges were jacked up way above high water the lifting operations would not be subjected to any problems caused by swell.

Accommodation is another issue to consider when planning equipment. Obviously larger sites are going to be further offshore and quite probably some distance from ports, which means that daily transfer of personnel will not be an option. The only solution to this would be to have the personnel stay on the barges on site during the installation.

The final point to mention on equipment is self-propelled barges. The ones used during the installation of the Blyth Offshore wind farm were not self- propelled and had to be towed to site by tugs. While this did not cause any problems in the relatively short journey that had to be made from the River Tyne to site, it would have implications for larger offshore sites. Towing barges to a site further offshore would have an impact on the time that it would take to travel to site from port. Self-propelled barges would take less time to move to and from site and then once on site would be able to manoeuvre into position without the assistance of tugs.

ill The installations of offshore wind turbines are so dependent on the sea state and can be held up with severe delays even in supposedly “good ” weather months. Each delay in the installation programme is lost generating time and an increase to the cost of the project. If commissioning a specialist vessel considerably reduces these delays then the case is obvious.

4.2 Weather

Installation would be planned for “good ” weather months, however not a great deal can be done to prevent delays due to weather. A flexible working plan could be implemented to enable parts of the project to be carried out simultaneously. If there was a delay on one part of the project, work could still be progressing on another thus avoiding delay to the overall plan.

4.3 Site

Full information on the seabed conditions of a prospective offshore wind farm site will be needed initially for the design of the foundations. For instance if the intention is to drive pile foundations rather than drilling into rock then it is particularly important to know the seabed conditions as a certain depth of sediment will be needed for pile driving. (Piles cannot be driven into very hard rock).

The seabed conditions are also very important to the barge operators of the installation equipment that would be used. When the barges jack-up they put their legs down on to the seabed, and the operators need to know the conditions that they will be working with. Primarily they need to establish if the barge can operate at that site and secondly to plan their operations and procedures.

4.4 Electrical Protection

Although this was not an issue with the Blyth Offshore wind farm there will be implications for larger offshore wind farms. The Electricity Association Engineering Recommendation for G.59 - “Recommendations for the Connection of Embedded Generating Plant to the Regional Electricity Companies ’ Distribution Systems” is only valid for generation up to 5MW. For much larger wind farms the G.59 protection would not be used, a more sophisticated protection system would need to be in place. This would be determined from investigations and discussions with the Distribution Network Operators and also the National Grid Company.

This offshore wind farm was a first and hopefully this report goes some way to highlighting the issues and how they were dealt with.

iv CONTENTS

1 INTRODUCTION...... 1

1.1 Background ...... 1 1.2 Aims & Objectives of this Report ...... 3 1.3 Equipment U sed ...... 4 1.4 SEA CONDITIONS...... 5 2 INSTALLATION...... 7

2.1 Planning and Scheduling ...... 7 2.2 Casing Installation & Socket Drilling ...... 7 2.3 SPOIL DISPOSAL...... 8 2.4 Monopile ...... 10 2.5 Tower Installation ...... 13 2.6 Installation of the Rotor ...... 17 2.7 Installation of the High V oltage Turbine Cable...... 20 3 CABLE LAYING...... 22

3.1 Optical Fibre Package ...... 22 3.2 Planning and Scheduling ...... 22 3.3 Beach Preparatory Work ...... 23 3.4 VESSEL...... 24 3.5 NAVIGATIONAL AIDS...... 24 3.6 CABLE LANDING...... 24 3.7 Diving Operations ...... 25 3.8 Cable Lay Operations between the Northern & Southern TURBINES...... 25 3.9 Cable Lay Operations Across the River Blyth ...... 26 3.10 Weather Contingencies ...... 27 3.11 Daily Reporting ...... 28 4 COMMISSIONING...... 30

5 ISSUES...... 32

5.1 Blade Lifting Procedure ...... 32 5.2 Cable Route Across the River ...... 32 5.3 WEATHER...... 33 5.4 Installation Differences ...... 34 6 IMPLICATIONS FOR FUTURE PROJECTS...... 36

6.1 Equipment ...... 36 6.2 WEATHER...... 37 6.3 SITE...... 37 6.4 Electrical Protection ...... 37 APPENDIX A - TURBINE LOCATIONS & CABLE ROUTE...... 38 APPENDIX B - RESPONSIBILITY FLOW DIAGRAM 39 APPENDIX C - PROJECT DIARY 41 APPENDIX D - WIJSLIFT 6 & SEACORE DRILLING RIG...... 43 APPENDIX E - LIFTING OF THE MONOPILE...... 45

APPENDIX F - CROSS SECTION OF CABLE...... 47

APPENDIX G - 2.0MW BLYTH OFFSHORE WIND TURBINE...... 49

1 APPENDIX A NOT AVAILABLE ELECTRONICALLY

vi 2 INTRODUCTION

2.1 Background

The wind farm off the coast of Blyth, Northumberland, is the first offshore wind farm built in the United Kingdom. Two 2 MW (see Appendix G for a scale diagram) wind turbines have been installed at a distance of approximately 1km from the coast, in a water depth, at low tide, of about 6m with a tidal range of approximately 5m. The completed project is the first in Europe to be exposed to the full force of the North Sea weather as well as a significant tidal range. The site is subject to breaking waves.

The site location is on a submerged rocky outcrop. Each wind turbine has been erected onto a steel pile (monopile) that was drilled and grouted into the rock. The 3.8m diameter holes for the pile were drilled from a jack-up barge (the Wijslift), and the pile lifted off the supply barge by the crane on the jack up barge and allowed to sink into the drilled socket. The monopile was then grouted into position and allowed to cure. When it had been confirmed that the monopile was secure in the hole, the sequence of erection was tower, nacelle and finally the rotor with the three blades attached.

Before any work could commence on site an FEPA (Food and Environment Protection Act) licence had to be granted from MAFF (Ministry of Agriculture Fisheries and Food) as the installation involved disposing of the drilling spoil into the sea. Part of the conditions for this licence were that some diving surveys had to be carried out before and after installation to review any potential impacts on the marine flora and fauna in the surrounding area. The first dive survey was executed in June 2000, before any work commenced. This gave the marine biologists their initial data. They then suggested to MAFF that the post dive survey should not be carried out until June 2001 to enable any impacts to be monitored at the same stage of seasonal growth as the pre-construction survey. This would allow an accurate before and after comparison and was therefore agreed and approved by MAFF.

The Blyth Offshore Wind Farm has been developed by Blyth Offshore Wind Limited (BOWL), a joint venture company between Powergen Renewables, Shell, Nuon and AMEC Border Wind. The diversity of experience and skills within these organisations has been brought together to pioneer the first project in what promises to be a new and exciting industry for the UK.

Powergen Renewables is a 50/50 joint venture between Powergen and offshore oil services group Abbot. Shell Renewables is one of five core businesses for the Shell Group, established to develop commercial opportunities in renewable energy. Nuon is a large Dutch utility and is the

1 largest operator and developer of renewable energy projects in the Netherlands. AMEC Border Wind develops and operates innovative renewable energy projects and was behind the UK's first semi-offshore wind farm at Blyth Harbour.

A flow diagram showing the different responsibilities of the companies is included in Appendix B.

Two minor contracts were placed by BOWL. 1. For Shell to act as project manager 2. For AMEC Border Wind to provide project services

The contracts for this project were managed by AMEC Border Wind. This included the supply and installation of the monopiles, the supply and installation of the wind turbines and the laying and connection of the cables.

The contracts were:

• Global Marine - supply, installation & commissioning of cable (hook-up to free issue switchgear)

• AMEC/Seacore - supply of foundation monopiles, transportation and installation of wind turbines. (including lifting of towers etc.)

• Vestas - supply of turbine (towers, nacelles & rotors) After the installation by AMEC, Vestas will commission the turbines. Normal commissioning period is one to two weeks, at Blyth it will be three months to fine tune the turbines because it is the first time that these machines have been used offshore.

There were two types of interface between the three main contracts

1. Information flow 2. Physical Interfaces

Safety Procedures and Quality Assurance were also interfaces that had to be managed.

The turbine was designed and manufactured by Vestas, which included the tower, nacelle, hub and blades.

The two-piece tower was manufactured at the Vestas tower manufacturing facility in Varde, Denmark, the nacelle and hub were assembled at Vestas V66 manufacturing facility in Ringkebing, Denmark and the blades were manufactured at Vestas blade manufacturing facility in Lem, Denmark. All of these parts were transported in special containers from the various sites to the port of Esbjerg and then shipped to the AMEC facility on the River Tyne, Newcastle.

2 The AMEC facility (Howdon Yard) on the River Tyne was used as the storage facility both before and during the installation of the wind turbines. The Howdon yard operates as a supply base which not only includes on site storage, but also permanent on site cranes that can lift large items of plant and equipment on and off vessels from the quayside. The location of the yard enabled delivery and transportation of materials to be by either road or sea. The yard is situated approximately 23km from the site location at Blyth which equated to 2 hours travelling time for the loaded barge to sail from the Howdon yard to the site at Blyth.

Prior to installation the turbines were delivered to the Howdon yard and stored there until they were needed, as well as the switchgear and basically any items of equipment or plant that were needed during installation and commissioning. The Wijslift was also based at the Howdon yard and the modifications that were needed to the vessel were completed while berthed at the yard.

The logistics and craneworks for the installation of the turbines were handled by AMEC Marine, but the fitting of the turbine parts was carried out by Vestas service engineers.

After the installation of the first turbine a review meeting took place with Vestas, AMEC Marine and AMEC Border Wind to go over the installation events. This evaluated how each part of the installation had progressed, where there were any deviations from the plan, what improvements could be made, what (if any) safety issues occurred and finally what action was required before the installation of the second turbine. The changes had to be discussed, agreed on and implemented quickly as the installation of the second turbine was time critical.

Included in this report are both of the methods used for the installation of the first turbine and then the different methods that were used for the second turbine.

The diary of the installation is in Appendix C.

2.2 Aims & Objectives of this Report

3 2.3 Equipment Used

• Coastal Explorer - this small survey vessel was chartered by Global Marine for use during the cable installation operations, it allowed the installation to proceed outside the restricted weather criteria of the Global Marine modular cable barge. • Andre B - was the spud leg dredger used to dig the cable trench across the river and was capable of working in wind speeds of 17-25 knots, force 5-6. (Spud legs on a vessel are legs that are lowered onto the sea /river bed. Lowering the legs lifts the vessel up by a small amount which results in increased stability of the vessel.) • Indus - this was the tug that was used to manoeuvre the Andre B and also to tow the ZH7 barge to and from the disposal ground and the river. • ZH7 - the barge / pontoon that was used to carry the dredged material for disposal. • RHIB - rigid hulled inflatable boat that was a fast boat used for crew transfer and general operational support. • Wijslift 6 - a six leg jack up barge owned and operated by AMEC Marine, equipped with a 250t capacity crane equipped with a 54m main boom and a 12m fly jib. (Jack-up legs lowered on to the sea bed to raise the vessel above the water.) • Atlas - the transport barge, a 55 x 22m dumb barge equipped with three 50T spud legs for mooring the vessel. • D H Bravo - the vessel used to control the spoil disposal operation, transfers of plant and materials locally and assist with barge movements. • Safety Boat - the Wijslift 6 is equipped with a 22ft RIB rescue boat powered by an inboard diesel with twin water jet unit. This is stored on deck ready for rapid deployment by the hydraulic deck crane. • Topcat & Cambois - support vessels to transport personnel to and from the site and also used to standby when certain operations were taking place. • Seacore Teredo 40 (T40) - a pile top/shaft drilling machine capable of drilling up to 6m diameter sockets. It can provide 30t continuous and 40t intermittent torque to the drill string/ drill bit and up to 150t of pull back. Two Seacore Volvo ‘Hushpack’ hydraulic power packs power the T40. • Drill Casing - the assembly had three parts; a 17m long x 3720mm primary conductor tube, flange bolted at the bottom to a 1.5m long x 3780mm gripper can. A sacrificial casing shoe with reinforced, saw tooth profile toe, sleeves into and was held by pneumatic grippers inside the gripper can. • Grout - CMS Pozament 80/20P high strength polymeric grout was used to grout the annulus between the rock and the pile. The grout contains a long chain organic polymer to resist wash out or dilution and has a short time period between initial and final set. It was therefore suitable for underwater grouting applications.

4 • Pump unit - the grout was mixed and placed using Seacore ’s twin pot colloidal mix/pump unit. The unit comprised two high shear colloidal mixing tanks above a single paddle wheel agitation holding tank. The grout was placed by two helical drive mono pumps, which drew directly from the bottom of the holding tank. • Spoil pumps - spoil material was pumped by two Pegson VS150 HF4 diesel pumps. They were capable of pumping 500m 3/hr to a head of 63m and could accommodate particles up to 98mm diameter in a water / solids ratio of 12.5:1 • Spoil Disposal Pipeline - was a 280mm outside diameter, 200m long MDPE spoil disposal pipeline that transported the material to a drop pipe with a sinker weight depositing it outside the exclusion zone. • Monopiles - 33m long, 3.5m diameter, 120t weight. They were designed by Vestas and LIC, whilst the engineering and manufacture was completed by Watson Steel.

2.4 Sea Conditions

To define the sea limits 0.5m marks were painted on the legs of the Wijslift in view of the Atlas so that the sea state can be measured, whilst the on site the wind speed was measured on the anemometer on the jib of the Wijslift. The limiting factors were set so that grouting operations could only take place during wind speeds of 10m/s or less in a swell of 0.5m or less. Lifting operations could only take place on site in wind speeds of 8m/s or less and in a swell no greater than 0.5m.

For lifting operations to take place at the Howdon yard the limits were set to wind speed of 10m/s or less and also authority had to be received from the harbourmaster before anything could be moved from Howdon to site off Blyth.

For personnel transfer to and from the Wijslift the main access ladder could be utilised at all states of the tide up to a deck level of+14.0m.

5 6 3 INSTALLATION

The installation of the offshore wind farm is described in detail throughout this section of the report describing the different activities and stages that were involved. When it came to planning and scheduling some of these activities were grouped together under one task heading in the project plan.

3.1 Planning and Scheduling

Monopile installation in the project plan actually covers all of the activities described in 2.2, 2.3 and 2.4. The time scheduled for the installation of the monopiles was originally 15 days in total, 7.5 days for each pile. In actual fact it only took 6 days to install the first monopile and then 7 days to install the second. The second installation took slightly longer as the second monopile was 2m longer than the first, so obviously the hole had to 2m deeper which added to the drilling time. This was a result of ground investigations at the site revealing a different formation in the rock at the second location. In effect the installation of the monopiles went according to plan.

After the monopiles were installed the plan was to carry straight on with the installation of the turbines. This task was initially scheduled for 2.5 days for each turbine. In reality after the monopiles were installed the weather took another turn for the worse and storms hit the site, the result being, the monopiles were installed for a period of two weeks before the turbine installation could be attempted.

The first turbine took 13 days to install but only 4 of those days were working days. The tower sections went on in the first 2 days, the nacelle was installed the following day and then a further 9 days were spent waiting for suitable weather and sea state to bring the rotor out to site and lift it into place. When that did happen it took 1 day to transport the rotor from the AMEC facility on the Tyne to the site and then to lift and install it.

The second turbine installation only took 5 days. The tower and nacelle installation was shortened from 3 to 2 days by changing the method of installation as described in 2.5. As with the first turbine installation suitable weather conditions were needed to transport and install the rotor, but in this case the waiting period was only 2 days as opposed to the previous 9.

Once again this highlights just how important good weather and sea conditions (low wind and swell) are for offshore installations.

3.2 Casing Installation & Socket Drilling

The monopiles had to be installed into drilled sockets as the site was on hard rock, too hard for the piles to be driven in. The drilling machine that was used for this project was the Seacore Teredo 40 (T40), which was a pile top/shaft drilling machine as shown in Fig. 1. The T40 was powered by two hydraulic power packs.

7 Fig. 1

Underneath the T40 a tubular steel guide was attached to act as upper support for the conductor and casing shoe assembly. A drawing of the Seacore drilling rig on the Wijslift 6 vessel is in Appendix D. The conductor and sacrificial casing shoe assembly assisted in keeping the drill string and the socket vertical. The assembly consisted of a conductor tube, flange and gripper can and enabled a ‘diver free’ operation of disconnecting the conductor from the sacrificial casing shoe on completion of the socket drilling.

A smaller drill bit was used initially to drill a centralising hole for the conductor assembly installation before the 3800mm diameter drill bit was used.

When the Seacore driller / engineer was satisfied with the socket levels the drill bit was pulled off the socket bottom. The conductor and gripper can assembly were pulled back up through the casing guide. The T40 was manoeuvred away from the socket location and the socket was then ready for the pile installation.

The were approximately 14 people involved during this operation, including the crew of the Wijslift 6, the Seacore personnel, a supervisor and a project management representative.

3.3 Spoil Disposal

A 200m long x 280mm diameter MDPE spoil disposal pipeline transported the pumped material to a drop pipe with sinker weight depositing outside the

8 exclusion zone. The reason for the use of the spoil pipe to remove the spoil from site was to ensure that the existing lobster holes on the exposed rock head did not become blocked. A licence and approval had to be obtained from the Ministry of Agriculture Fisheries and Food to authorise the deposit of substances in the sea as part of the Food and Environment Protection Act 1985.

The hose was assembled in 11.5m lengths with flanged ends. Each length incorporated one or two closed cell polyethylene flotation collars, each collar having a net buoyancy of 250kg. The collars enabled the floating hose to maintain positive buoyancy at all times during the pumping operation. Fig. 2 shows the spoil pipe in use as the drilling took place for the southern turbine.

Fig. 2

A specially designed and reinforced container positioned directly underneath the T40 spoil exhaust outlet acted as a buffer for the airlifted spoil prior to being pumped along the floating hose to outside the exclusion zone. The airlifted spoil material was highly aerated by the time it reached the atmosphere, so the 20ft container also ‘de-aired’ the water for more efficient pumping.

The spoil material was pumped by two Pegson VS 150 HF4 diesel pumps. The Pegson pumps were positioned on the deck of the Wijslift 6 drawing directly from the spoil container, through two 6" Bauer hoses. The pump outlets fed into a 10" steel manifold which was connected to the 200m long floating disposal pipeline.

During the drilling process the airlifted spoil material was collected in the buffer container and pumped along the floating hose for near seabed disposal outside the exclusion zone. A sinker weight on the end of the drop pipe

9 helped with the positioning of the flexible hose and enabled distribution of the spoil material on the seabed.

During the drilling operations the support vessel operated 24 hours to monitor the spoil disposal system. The vessel moved the end of the pipeline at regular intervals to maintain even dispersion of the spoil. No formal records of this operation were kept.

3.4 Monopile

At the AMEC facility (the storage yard) the monopile was loaded onto the Atlas spud leg barge that was moored alongside. Once the hole had been drilled for a monopile it was delivered to site (from the storing yard) by the Atlas barge. The monopile was then lifted off the barge, positioned in the hole and grouted in place.

3.4.1 Installation Operational Requirements

At the site of the wind farm the lifting operations for the monopile were limited to and could only be carried out when the wind speed was 8m/s or less and the swell was no greater than 0.5m. Restrictions also applied at the storing yard when lifting the monopile onto the Atlas barge. There the wind speed had to be no greater than 10m/s.

The wind speed at site was measured on the Anemometer on the jib of the Wijslift, whilst the swell was measured against a marked up leg. A log of the wind and wave conditions was kept as soon as the Wijslift was on station.

In order for the Atlas barge to travel from the storing yard to site, authority had to be received from the harbourmaster and a storm haven had to be made available in Blyth Harbour.

3.4.2 Loading Monopile Sections onto Atlas

When the monopile sections were being loaded onto the Atlas barge, it had to be moored alongside the quay and secured with mooring lines. The spud legs were also dropped and the preparations for sea fastening were carried out. The lifting slings were then attached to the monopile and when the weather was deemed suitable (see 2.3.2) the sections were placed and secured onto the deck of the Atlas and then the sea fastenings were completed as shown in Fig. 3.

10 Fig. 3

Once the socket drilling had been completed the T40 was manoeuvred out of the way of the socket location. An open rock socket then existed in the seabed with the sacrificial casing shoe installed.

The pile seating lugs positioned at the pile toe were adjusted in accordance with the final level of the socket bottom. All of the necessary hoses, strops, survey aids and the like were assembled on to the pile ready for pile installation.

At site the Wijslift jib was brought into position over the monopile and a single wire hook on the main jib head was used to find the centre of gravity. Once the centre of gravity had been located the sea fastenings were then detached.

11 Fig. 4

For both monopiles the units were lifted and rotated until they were suspended vertically (as shown in Fig. 4) and then presented over the centre of the rock socket and lowered through the pile gates into the water. (Appendix E shows a drawing of this procedure). The pile gates offered guidance to the pile as it was lowered into the top of the rock socket, sufficient sea water was pumped into the pile to ensure it sank into the socket. Pile lowering continued until the pile ‘feet’ were fully seated on the socket bottom. The pile position, orientation, vertically and level were checked from the shore survey stations and adjustments made as necessary. Following confirmation of the pile survey, the pile was flooded to a designated level (for grouting operations) and the crane released.

3,4,3 Grouting

A high strength polymeric grout was used to grout the annulus between the rock and the pile. This type of grout was used as it contains a long chain organic polymer to resist wash out or dilution and has a short time period between initial and final set, and is therefore suitable for underwater grouting applications.

The fresh water needed to mix the grout was supplied from the Wijslift ballast tanks, which were filled at the quay prior to sailing. Pile grouting was undertaken as a continuous staged operation through a series of integral grout tubes that were installed in the pile during its fabrication. Each pile was grouted in four stages. The first stage pumped grout along two pipes through the base of the pile. The following grout stages two, three and four pumped grout through pairs of pipes running down the inside of the pile diametrically opposite and terminating through the side of the pile.

12 Grout migration up the rock socket / pile annulus was monitored by a grout probe deployed down the next grout stage pipes. Once the probe detects grout at the bottom of the next stage grout pipes grouting operations were suspended briefly and the feed hoses disconnected from the last completed stage and reconnected to the next. This operation was continued until the grout overflowed at the top of the annulus onto the seabed concluding pile grouting.

The pile gates remained in place providing lateral support to the pile until the grout maintained its Pile Release Strength for up to 12 hours.

During the grouting operations grout cube samples were taken for each grout stage. 15 cubes were taken per monopile for crushing at the following times:

• 3 @ 24 hours • 3 @ 3 days • 3 @ 7 days • 6 @ 28 days

Extra cubes were taken at the early stages of the grouting operation so that early Ultimate Compressive Strength results could be obtained using an on board portable crushing facility. The cubes listed above were maintained on deck in a water tank until they were transferred to a laboratory near Newcastle. It was the cube test results that proved when the grout had reached its pile release strength.

The same personnel were involved in the grouting procedure as carried out the installation of the monopile. All in all the two operations combined involved approximately 20 people, made up of AMEC Marine and Seacore personnel. There were various people who travelled out to the site throughout the operations to see what was involved, but they were there purely as observers and therefore have been discounted from the number of people actually involved.

3.5 Tower Installation

At the storing yard the Atlas was moored alongside the quay edge and secured with mooring lines. As with the monopiles the spud legs were dropped and preparations made for sea-fastening. The switchgear, tower sections and nacelle were individually lifted from the shore side onto the Atlas and the sea fastenings completed. (See 1.4 for details of the sea and weather conditions for the lifting operations).

The loadings of the equipment were as follows:

Lower Tower 56500kg Upper Tower 29000kg Nacelle Transport mode 72000kg Nacelle Installation mode 63000kg Tools Container 8500kg Nacelle Transport frame 9000kg

13 Cable Drum 2000kg

The switchgear, access platform, two tower sections and nacelle were carried on the Atlas to site. When the Atlas reached the site at Blyth the first item to be placed onto the monopile was the switchgear unit, but before any equipment could be transferred a man had to be placed on the monopile to receive the load.

Fig. 5

The access platform was lifted into position and secured before the tower sections were installed. (Fig. 5 shows the access platform being guided into position). To lift the tower sections the Wijslift jib was brought into position over each of the sections and the single wire hook was used to find the centre of gravity. Once the centre of gravity had been found the sea fastenings were detached.

For the tower sections each unit was lifted and rotated until it was suspended from the top end alone while a minimum of two tag lines had to be attached to the extremes of the lift. (Fig. 6 shows one of the lower tower sections as it was first lifted horizontally off the barge). The tower section was then brought back over the Atlas deck with one metre minimum clearance to allow the bolted lifting shoe to be un-bolted and disconnected. The tailing block continued to be lowered to leave the unit solely suspended below the head lifting beam. The tailing sling was either disconnected or raised above the base of the tower unit.

14 Fig. 6

For the second tower installation the Wijslift was brought back into the harbour where the lower tower section and nacelle were loaded onto the Wijslift to be taken out to the site of the northern turbine and therefore eliminating lifting those turbine components from being lifted off the Atlas barge. (This installation method was a revision to the original and was decided upon after the project team reviewed the first turbine installation and the problems that had been encountered). As the Wijslift was jacked up above high water those lifts could take place in swell conditions that otherwise would have prevented the lifts from going ahead had the components been on the Atlas. This resulted in the second tower installation being a lot quicker than the first as it eliminated one of the limiting factors, sea state / swell.

At each tower connection at least 40 bolts had to be in place and the torques equally spread around the third points of the circumference before the crane could be disconnected from the load. When the tower base was secured a man climbed the tower to release the lifting equipment from the top of the tower section. Likewise when the upper section of the tower was being installed two men were in place in the top of the lower section to bolt the two sections together. (Fig. 7 shows the top tower section being aligned to the lower section). Then when sections were joined and torqued together the men had to climb to the top of the tower to release the lifting equipment.

15 Fig. 7

When placing the Nacelle particular attention had to be paid to wind and sea conditions. The nacelle was lifted together with its transport frame onto the Wijslift deck so that the crane operator on the Wijslift could be sure of enough height and clearance by lifting straight from the deck of the Wijslift up to the top of the tower. (The Wijslift had been previously been jacked up and was therefore quite a bit higher than when the nacelle was lifted from the deck of the Atlas barge). The transport frame provided protection as it left the floating craft. Once on the Wijslift the nacelle was un-bolted from its transport frame for lifting into place. Fig. 8 shows the nacelle in place on the top of the tower.

Fig. 8

16 All personnel that were working at height within the Tower during assembly used the harnessing arrangements provided within each tower section.

3.6 Installation of the Rotor

The assembly of the rotor was completed at the storing yard. Once completed the unit was lifted from the shore onto the Atlas barge and sea fastened in place before being transported to site and securely positioned next to the Wijslift barge. The site surface conditions were the same as for the lift of the tower sections (see section 2.3.2).

3.6.1 Loading Rotor onto the Atlas

The rotor was the last item to be placed on the barge. The barge had to be turned prior to the installation in order to avoid any possible damage to the blades, two of which overhung the edge of the barge.

Once the rotor was secured on the deck the support that was needed under the three blades had to be built up. (This was used to stabilise the blades for transport.) The blades were rested in wooden frames and edge protectors were installed prior to any strapping of the blades.

The tip packing was placed in position on the deck and the sea fastening chains were prepared at the hub securing point. The lifting slings were then attached to the rotor assembly, it was then lifted together with the nose cone onto the barge and the sea fastenings were completed. The tag-lines were then attached to each tip and the barge sailed in this condition. Fig. 9 shows the rotor as it was finally lowered onto the barge.

17 Fig. 9

The assembled rotor on the deck of the Atlas barge was:

Total weight 24000kg

3,6,2 Lifting the Rotor into position

The Atlas barge arrived on site at Blyth with tugs controlling its position. The position was fixed using anchors controlled from the Atlas barge. The Wijslift Fly jib was brought into position over the load and the tailing crane was attached to the Tailing Blade tip. The sea fastenings were then detached from the blades.

The rotor was positioned with the flange uppermost. Using the Wijslift crane the lift started, then the nose cone was wheeled into position under the hub. Securing bolts were fitted into the cone apex before the cone was released.

A tandem lift was used to move the completed rotor assembly from the deck of the Atlas spud leg barge, onto the nacelle of the rotor tower. The rotor was lifted from a face down position on the Atlas, to a near vertical position next to the tower as shown in Fig. 10. The blades were rotated past 90 degrees through the vertical position. The rotor was then secured to the tower and the lifting apparatus and the tag lines removed.

18 Fig. 10

The hub was released from the hook and the line and blade packing was released, but the hub could not be un-pinned and rotated until it had been turned in plan to be running parallel with the face of the Wijslift. Fig. 11 shows the rotor finally installed.

Fig. 11

19 3.7 Installation of the High Voltage Turbine Cable

The installation had to be done before the Wijslift could move due to the fact that the generator on board was needed to operate the nacelle service crane as there was no electrical power in the turbine at that time. The cable drum was lifted in a frame that was then mounted on to the access platform. The nacelle service crane was used for pulling the cable inside through the door and also during the installation.

The cable was wound around the cable loop in the lower part of the top tower section. From the cable loop down the HV cable was fastened with cable strips to support for the leader. The cable was then fed down below the lower platform of the tower bottom section and into the HV switch. The signal and supply cables were fastened with cable strips to the HV cable all of the way down together with the protective conductors. Protection tubes for the cables had to be mounted at platforms and fences to reduce the risk of contact with swinging cables.

As with the installation and the grouting of the monopile, the same teams of people were involved with installing the turbine, from the access platform to the rotor and landing of the tower cable. There were 15 people working on site during the turbine installation. The operations being directed by the Vestas personnel and the AMEC crane operator.

20 21 4 CABLE LAYING The scope of work for the installation of the power cable between the two offshore wind turbines and the mainland included:

1) Procurement of the cable 2) Mobilisation of installation vessel 3) Loading of the cables 4) Diver swim survey across the harbour and of site of the turbines 5) Installation of the duct across the harbour mouth 6) Installation of the cable across the harbour mouth 7) Installation of the cable between the offshore wind turbines 8) Installation of the cable between the southern turbine and the breakwater 9) Reinstatement of the beach 10) Demobilisation of the installation vessel

The route of the cable is shown in Appendix A.

The submarine cable used for the project was 70sqmm EPR Double Wire Armour with 16 fibre optic package. A diagram of the cross section of this cable is shown in Appendix F.

4.1 Optical Fibre Package

The optic fibres were contained in a seamless, laser welded, hard drawn stainless steel tube filled with a thixotropic compound. The fibres are submarine telecommunications grade, single mode compliant. The cable load elongation performance is crucial to the fibre long term performance and effective service life. Therefore the optic package was of a loose tube construction ensuring that the fibres see no strain at the designated working load.

4.2 Planning and Scheduling

The task names used in the project plan do not directly correspond the activities described in this section. As with the installation of the monopiles and turbines some of the cable laying activities were grouped together under one task name for planning purposes.

In the original plan the duration for cable laying was sixty days. In actual fact the cable laying process took 3.5 months. However, as with the installation of the turbines not all of this time was working time. The delays in installing the turbines had a ‘knock-on ’ effect on the cable laying activities i.e. the cable could not be laid between the turbines or from the turbines to the beach until the turbines had been installed and the vessels used during the installation had moved off site.

When the cable lay commenced between the turbines and from the south turbine to the beach it took 5 days as planned. The cable was laid from the

22 south turbine to the beach first, but again due to bad weather and high seas the cable lay between the turbines could not be done until 2 or 3 days later. This particular task was originally scheduled to only take 1 day and ended up taking 3 days as the sea state was constantly changing which disrupted the diving operations.

The cable lay across the river and the dredging work that proceeded it also took longer than planned. The planned duration was 15 days when it actually took about thirty days. Again this was not thirty working days. There were approximately 7 to 10 days of ‘downtime ’ when the crew of the dredger carried out repairs to their hydraulic system and also changed buckets that were broken digging the rock out of the river bed. The working time was twenty days, which is still longer than planned, but was due to the trench and ducts backfilling before the cable could be pulled through.

The weather was still a big problem during the cable laying activities even those that were being carried out onshore. For example there were occasions when work could not be carried out on the pier as the wind was too strong. As a result the plan was constantly shifting and it almost ended up being a case of completing jobs and parts of jobs as and when they got the chance.

To summarise the cable laying was held up initially by the delay in the turbine installation and then later by the weather and also unforeseen conditions (e.g. trenches backfilling etc.). The following sections describe in more detail the activities that took place.

4.3 Beach Preparatory Work

Site perimeter barricades for the beach work area were provided throughout the operations for public safety. This was due to the fact that tension on the cable could be experienced on the beach and an exclusion zone was required in the interests of public safety. A clear path of the cable pull line was created. Fig. 12 shows the cable trench on the beach disappearing into the sea.

23 Fig. 12

Liaison was established with the Harbour Commission and obviously the Harbour Master in order to advise them of operations and provide them with information.

4.4 Vessel

The Coastal Explorer was chartered by Global Marine Systems Limited to be used throughout the cable laying operations between both turbines and also from the southern turbine to the pier. The cable handling equipment was loaded on board and bolted into place. Once the vessel had been mobilised, the cable drum was loaded on board and installation commenced.

4.5 Navigational Aids

Navigational, tracking, monitoring and recording systems consisted of the following:

1 x DGPS receiver, which provided a “Helmsman’s display” and had a data logging feature that recorded the position of the installed cable.

4.6 Cable Landing

The installation vessel was moored in the close to the base of the Southern Turbine. The cable end was then passed up the “J-Tube” via a short

24 messenger line, utilising a small winch or hydraulic Tirfor. Once the required amount of cable had been installed and secured into the turbine, the cable lay could commence.

When the installation vessel approached the shore, the cable end was passed to the beach team via divers (wading depth), who then pulled the remaining cable onto the beach, until the required amount of the cable was ashore.

4.7 Diving Operations

The diving operations were carried out both safely and efficiently. It was imperative that all diving operations were thoroughly planned, briefed and executed in accordance with all appropriate diving regulations. (The Coastal Explorer was also used as the dive support vessel.) The works included:

• Surveying proposed shore end route • Assisting with the pulling rope • Removing the cable floats • Surveying the as laid cable (where necessary) • Supporting cable lay and burial operations • Attachment of Uraduct (product name for ducting used to give extra protection to the cable where required).

The diving team were under the control of a suitably qualified Diving Supervisor who had direct overall control, and responsibility for the safety of the diving team. However, in order for diving operations to commence, and to continue, authorisation was required from the Diving Supervisor, the Offshore Superintendent and the Beach Master (or their appointed Deputy). Diving operations would have ceased forthwith if, at any time, for operational or safety reasons authorisation had been withdrawn by one of these people.

4.8 Cable Lay Operations between the Northern & Southern Turbines

When permission had been received from the shore that the lay could commence the Offshore Superintendent took over responsibility for the cable lay. Once all the pre checks had been completed the vessel moved to the North Turbine and moored up at the base of the turbine. A messenger line was run up the “J-Tube” and a small winch or hydraulic Tirfor was installed at the top of the “J-Tube”. The cable was then hauled up the J-Tube via the messenger line. Once the required amount of cable had been hauled up the cable was then secured inside the turbine tower. The cable that was laid between the two turbines and also from the southern turbine to the beach was laid directly onto the sea bed. Fig. 13 shows the cable laying vessel in operation between the two turbines.

25 Fig. 13

The cable was paid out from the cable drum, controlled by the powered cable stand, via the overhead cable roller quadrant and cable pathway. The cable lead was visible at all times from the deck vessel.

4.9 Cable Lav Operations Across the River Blyth

Due to the changes in burial criteria (see Section 5.2), Global Marine Systems Ltd researched the use of a suitable dredger to remove the 2m of mud overburden and to cut a trench into the bedrock. A cross section of the harbour was drawn up showing the depth of burial that had to be achieved. A spud leg dredger was mobilised complete with a built in dredging arm that was able to operate throughout most of the tidal range and the spoil was loaded onto a pontoon and dumped at the Port of Blyth’s dedicated spoil dumping area. Fig 14 shows the dredger in operation with the pontoon alongside. An extension to the Blyth Harbour Commission licence for the deposit of materials at sea was obtained for the duration of the river dredging operations.

26 Fig. 14

As the trench was excavated a duct was installed. It was positioned into the trench by divers and weighted so that it would sink. At the breakwater the duct met with another directionally drilled duct, and as a manhole had previously been excavated on the harbour wall it allowed the cables between the river and offshore sections to be terminated.

The cable for the harbour crossing was delivered to site on a drum. This drum was set up on the shore / quayside and pulled through the duct to the manhole utilising a winch.

4.10 Weather Contingencies

The majority of the cable laying operations were governed by the weather or more to the point reliant on “good ” weather. Prior to the start of each operation and in addition to the daily weather forecasts received during operations, long term weather forecasts were also obtained from a professional weather service to cover the period of operations. To ensure the safety of personnel and the security of the cable, work was never started if bad weather was forecast. Similarly when the weather proved to be different to that forecast and weather changed for the worse all work was stopped and equipment and personnel made safe. Specific weather conditions were not laid down for each operation, offshore superintendent and the dive supervisor had the training, knowledge and expertise to interpret weather forecasts and swell to know in what conditions the work could be carried out.

27 4.11 Daily Reporting

A report was submitted daily, starting from the day of the departure from the mobilisation port and finishing on arrival at the demobilisation port. The daily report contained the following:

a) time, date and number of the report b) weather conditions experienced during the preceding 24 hours c) geographical position of the vessel at the time of the report d) summary of the work performed during the preceding 24 hours e) summary of the planned work for next 24 hours f) time spent on effective work during the preceding 24 hours g) weather downtime h) vessel / equipment downtime during each 24 hour period i) summary of plant installed and burial performance j) any other pertinent information about the operation and progress k) endorsement of the report by the Customer ’s Senior Representative

During the cable laying operations the numbers of people that were directly involved varied from stage to stage, i.e. vessels and divers were used for the offshore cable laying as opposed to one or two cable hands laying the cable into the onshore switchroom. There were on average 10 people + 1 supervisor working throughout the cable laying operations.

28 29 5 COMMISSIONING

There were various stages to commissioning the wind farm. Initially Vestas had priority over access to the turbines and a procedure was put in place where any personnel going out to work on the turbines had to complete a permit stating exactly who was going out, what work they were going to do and also giving mobile phone numbers for communications purposes. Then when they returned back to the site office the permit had to be signed off to say that the work was completed for that day.

During this period of time the marine lanterns and foghorn for navigational purposes had to be fitted and the cable jointing team had to have access to terminate the power cable onto the switchgear in each tower. Once the power cable terminations were completed both in the turbines and onshore in the switchroom and the installation was tested the Distribution Network Operator was then able to energise the wind farm i.e. connect the wind farm to the grid.

At this time the communication system was completed. This required the fibre optic cores to be terminated in each turbine and also in the control room onshore. Once the terminations were complete the various items of equipment needed to send and receive signals down the fibres were connected and tested to enable the turbine controllers to be accessed remotely from the control room. (The turbines can be checked using the onshore computer as well as stopped and restarted if need be.)

Even though the wind farm now had power the final commissioning tests and generation could not take place until the protection engineer from the Distribution Network Operator had witnessed the testing of the G.59 protection relay in each turbine. (This relay disconnects the wind farm in the event of a problem with the grid.) Once the tests were complete the final commissioning of the wind turbines could take place, including a 240 hour continuous generation test.

30 31 6 ISSUES

6.1 Blade Lifting Procedure

The initial procedure that was discussed for lifting and installing the blades was to lift the blades using a horizontal method and installing them separately.

The idea was to use a large clamp about 3m in length that would be attached to the crane hook. Before the blades could be installed the nacelle would be installed with the hub attached. Inside the nacelle the coupling between the generator and the gearbox would have to be disconnected and a hydraulic motor connected to the gearbox to enable the hub to be turned for the blades installation.

The clamp was to be attached to each blade in turn about its centre of gravity, then the blade would be lifted up horizontally and offered up to the flange on the hub, bolted on and the clamp released (via remote control). Once that blade was in place and the clamp removed the hub would be rotated so that the next flange was in line for the next blade to be lifted horizontally. The process would then be repeated for the third and final blade.

There were three main problems that prevented this procedure from being used:

1. Vestas wanted to test this method of lifting and installation on land based projects first, but those projects were delayed and put back until the point where if testing had gone ahead we would have been into the planned installation dates. 2. There were delays with the clamp manufacturer which could have resulted in only one clamp being made and no back up 3. There were also similar problems with the hydraulic motor for the nacelle and that there would be no back up and also the motor was very heavy and difficult to manoeuvre up to the nacelle and back down again once the blades had been installed.

The solution to the problems posed by the initial blade lifting and installation procedure was to use a completely different, yet tried and tested method as described in Section 2.3 in this report.

6.2 Cable Route Across the River

A change to the channel depth resulted in change of method of laying cable.

Initially it was understood that the cable had to be buried 2m below the current dredged depth of the river so the initial plan was to prepare a deep trench across the river below bed level and bury the cable in the trench without using any ducts. However, Blyth Harbour Commission actually required the cable to be buried under the River Blyth at a depth of 2m below the maximum

32 dredged depth and as a result a change was made to the proposal. Different marine plant was now required in the form of a dredger which would be used to dredge down below the maximum dredged depth. As the requirement was now to go below the bedrock the new proposal was to excavate a shallower trench in the bedrock of the river bed, lay ducting, then pin the duct to the floor of the trench and lay the cable through the duct.

Herbosch-Kiere was the company who supplied the spud leg dredger to assist with the cable laying activities across the river Blyth. All dumping was carried out in accordance with an extension granted to Blyth Harbour Commission dumping licence to cover this operation, therefore Blyth Harbour Commission had to be kept fully informed.

When dredging commenced there were no problems removing the silt and mud, but when the dredger reached rock it was a lot harder than they had first thought. This caused several problems, mainly breakages of dredger equipment which resulted in delays as the equipment had to be replaced.

Global Marine Systems and the dredger crew found that they had reached the required depth fairly quickly in some parts of the river and not in others, but across the river they hit what they classed as bedrock and proposed that they dig a metre below this level and that would be sufficient depth to bury the cable at. This required approval from Blyth Harbour Commission.

The Harbour Master and Port Engineer viewed the equipment that the dredger was using while they were working on the trench and this proved to them that the profile and depths that the dredger was reporting they had reached were true. When the dredger had excavated the trench across the river from the east pier to the quayside the Harbour Commission went back on the dredger and followed the trench across the river agreeing the profile and depth and giving their dispensation on the original depth that they had requested for the full length of the trench. This immediately solved the potential problem of having to bring in specialist rock breaking equipment.

6.3 Weather

The weather was always going to be an issue and could not be relied upon. Trying to arrange and plan a project so that installation takes place in certain months of the year, i.e. the summer months would hopefully reduce the possibility of bad weather affecting progress.

This was initially the case for this particular project, but unfortunately (and unusually for that time of year) the weather took a turn for the worse and in particular caused an increase in the swell.

As explained earlier in this document many of the installation procedures could only be carried out in swell of 0.5m or less. The reason being that it was unknown how the equipment being used would react in certain conditions.

33 Even at low swell there is still a chance of “rogue ” waves and the reaction to these waves could have caused damage to the turbine items on the Atlas barge.

For instance if the load was taken on the crane and the crane started to lift a part of the turbine and all of a sudden a wave comes along that would lift the barge, the barge would react, lift up and hit the bottom of the load, causing damage to that part of the turbine. Cranes cannot move quickly and the hooks holding the load cannot get the load out of the way very quickly. (Soft slings were used to try and reduce or prevent any damage to the turbine during lifting.)

There were no solutions to the weather problems other than to constantly monitor weather forecasts and have everything geared up and ready to go when a suitable weather window was available.

6.4 Installation Differences

When the first turbine was installed each component was taken to site on the Atlas barge and had to be lifted from the barge by the crane on the Wijslift. The Wijslift was jacked-up above the sea and was therefore stationary while the Atlas barge was moving up and down with the swell. Having realised that this was restricting lifting operations to times when the swell and wind were very low and therefore causing delays, the decision was taken to do things differently for the second turbine installation.

The Wijslift was towed back to the Howdon yard where the lower tower section and the nacelle were lifted on to the Wijslift to be taken out to site. This resulted in those two components being lifted directly off the deck of the Wijslift. As the Wijslift was jacked-up above high water those lifts could take place in higher swell conditions that otherwise would have prevented the lifts from going ahead had the components been on the Atlas barge.

As a result the second turbine installation happening in a shorter time frame and eliminated the issue of sea state and swell.

34 35 7 IMPLICATIONS FOR FUTURE PROJECTS

The installation and commissioning of the Blyth Offshore wind farm has highlighted many implications that should be taken into consideration for future offshore wind farms. The four major ones are discussed in more detail below, but in general terms future project teams should review their methods and operations throughout the installation and take into account and act on any lessons learned.

7.1 Equipment

For future larger projects further offshore it would be preferable to have a crane barge that can jack up above the swell to lift and install the pile foundations and the turbine components, and a flat barge that could also be jacked up during lifting operations, to transport the components to site. If the crane barge and the flat barge were jacked up way above high water then all of the lifting operations would be static lifts, i.e. neither the flat barge or the crane barge would be moving and would be independent of the swell, eliminating that as a major problem for the lift.

Another issue to consider with equipment is having enough accommodation on the barges for all of the personnel involved with the installation. Obviously larger sites are going to be further offshore and quite probably some distance from ports, which means that daily transfer of personnel will not be an option. The only solution to this would be to have the personnel stay on the barges on site during the installation.

The barges used during the installation of the Blyth Offshore wind farm were not self-propelled and had to be towed to site by tugs. While this did not cause any problems in the relatively short journey that had to be made from the River Tyne to site, it would have implications for larger offshore sites. Towing barges to a site further offshore would have an impact on the time that it would take to travel to site from port. Once on the site the tugs would also be required to help position the barges. Self-propelled barges would take less time to move to and from site and then once on site would be able to manoeuvre into position without the assistance of tugs.

If this means specialist vessels have to be commissioned then the case is obvious. The installations of offshore wind turbines are so dependent on the

36 sea state and can be held up with severe delays even in supposedly “good ” weather months. Each delay in the installation programme is lost generating time and an increase to the cost of the project. Obviously installing a larger wind farm with an increased number of turbines could justify the capital expenditure on more specialist vessels.

7.2 Weather

7.3 Site

When a site has been selected for an offshore wind farm full information is needed on the seabed conditions, initially for the design of the foundations. For instance if the intention is to drive pile foundations rather than drilling into rock then it is particularly important to know the seabed conditions as a certain depth of sediment will be needed for pile driving. (Piles cannot be driven into very hard rock).

Secondly seabed conditions are needed from the point of view of the installation equipment that would be used. When the barges jack-up they put their legs down on to the seabed, so the barge operators need to know the conditions to establish first of all if the barge can operate at that site and secondly to plan their operations and procedures.

7.4 Electrical Protection

37 Appendix A - TURBINE LOCATIONS & CABLE ROUTE (NOT AVAILABLE ELECTRONICALLY)

38 APPENDIX B - responsibility flow diagram

Shell Nuon AMEC Border Powergen Wind SHAREHOLDERS Huub den Henk Dave Farrier Rooijen Kouwenhoven David Still

PROJECT BOWL COMPANY

Huub den Rooijen

PROJECT MANAGEMENT

Norman Rogers Bill Grainger

Global Marine AMEC Marine Vestas Systems MAIN CONTRACTORS Steve Thwaite Preben Poulsen Andy Shaw

AMEC Watson Seacore LIC Falmouth Divers SUB CONTRACTORS Duncan Watt Phil Wilkinson Carsten Brendstrup Steve Roue l

39 40 Appendix C - PROJECT DIARY

Date Progress Pre-2000 Consents and Licences were approved. Lease negotiations took place with the Crown Estates. Contract discussions were held and the foundation design and integration studies were performed. Feb 2000 The Joint Venture Agreement was completed between Powergen Renewables, Shell, Nuon and AMEC Border Wind. Press and media releases were made detailing the project and its partners. Mar/May2000 The main contracts were placed with Vestas, AMEC, Seacore and Global Marine Systems. At the same time the project office was set up at South Harbour, Blyth. Jun 2000 AMEC’s jack-up barge Wijslift-6 was fitted with the Seacore drilling rig and other modifications that had to be made. 19 Jul 2000 The Vestas turbines were delivered to the AMEC storage yard at Howdon on the River Tyne. 25 Jul 2000 The steel monopile foundations were fitted with the J-tubes, access ladders and fenders to protect the ladders. The final details were also being put to the access platforms. 8 Aug 2000 Cable trench on the beach (from shore to east pier) was completed. 9 Aug 2000 The monopile foundations were loaded on to the AMEC Atlas barge ready for transportation to site. 14 Aug 00 The Wijslift-6 was in place at the offshore site and had begun jacking up to height for the initial drilling operations. 16 Aug 00 AMEC and Seacore completed installation and testing of the multi-stage drill bit. 17 Aug 00 Drilling of the first borehole (northern turbine) commenced. 23 Aug 00 The first monopile was installed and grouted. 25 Aug 00 Directional drilling down through the pier has been completed and the ducting installed. 8 Sep 00 Installation of the second monopile foundation was completed. Preparations were underway to enable the first wind turbine lifts to commence. 13 Sep 00 The first access platform was lifted into place and secured. Tower lifts will start when the weather conditions are appropriate. 17 Sep 00 The southern turbine tower has now been installed. This was a two stage process, lower tower section first and the upper tower section. 19 Sep 00 The southern nacelle was installed today. 25 Sep 00 Preparations were started for loading and transportation of the first rotor. This is totally dependant on weather and swell conditions. 26 Sep 00 Work was completed by the divers removing silt from the river bed at the quayside to assist with the installation of the

41 cable ducts. 27 Sep 00 Ducting installed at the quayside. 30 Sep 00 The first rotor was installed on the southern turbine . 3 Oct 00 The Wijslift moved station to the north turbine location and is jacking up to the required level for platform and tower installation. 5 Oct 00 The switchgear, access platform and lower tower section have been installed at the north turbine location. The Wijslift then had to jack up to the higher level required for upper tower and nacelle installation. 6 Oct 00 The upper tower section and the nacelle were installed today. 9 Oct 00 The second rotor has been installed. The activities that remain to complete the wind farm are the installation of the cable to shore, onshore electrical works and turbine commissioning. 9 Oct 00 The cable was laid from the southern turbine to the pier. 12 Oct 00 The cable was pulled up through the directionally drilled hole in the pier to the draw pit (manhole) on top of the pier. 19 Oct 00 Dredging commenced across the River Blyth. Yellow markers have been used on both sides of the river to indicate the position of the cable ducts. 25 Oct 00 Dredging operations finished across the river and the profile of the trench was approved by Blyth Harbour. 28 Oct 00 Ducting installed across the river. 29 Oct 00 The cable was installed from the pier to the quayside. 1 Nov 00 Cable termination work was started in the north turbine. 2 Nov 00 The cable trench across the river was back filled. 3 Nov 00 Work started on cable installation from the quayside to the onshore switchroom. 4 Nov 00 Trench across river backfilled and completely finished. 5 Nov 00 Cable termination work complete offshore. 6 Nov 00 Cable installed into sub station. 6 Nov 00 Cable termination completed onshore. 8 Nov 00 Onshore cable trench backfilled and tarmac complete. 10 Nov 00 Grid Connection 11 Nov 00 Wind farm energised, circuit breaker settings checked. 17 Nov 00 G59 Protection relay tests complete. 20 Nov 00 Fibre optic terminations commenced. 23 Nov 00 Fibre optic terminations complete. 4 Dec 00 Turbine commissioning complete.

42 Appendix D - WIJSLIFT 6 & SEACORE DRILLING RIG

W S'11U. MHWS---- WAVE i:l USL —' VLWS—" LAT —' hfirv S' ILL ■ y S.'.AlJL I?----

JRILL SQCKIi 0 CORRECT l> I'il- FOR VEivO ”ll l 1 Sm FOR 62 AND 13m FOR §l

Drawing reproduced by kind permission of Seacore.

43 44 Appendix E - LIFTING OF THE MONOPILE

ccn lurroR amoved , s.ior orii i rio TO i:XTTNTS 0- '[. HOE I IORN' IN|3C-A-tU 10 LEAVE SPACE LOWER HO -Ilf INTO SOCKET. L.ll T MONCRII T OVER CENTER Of SOCKET .OCANON.

Drawing reproduced by kind permission of Seacore.

45 46 Appendix F - CROSS SECTION OF CABLE

Conductor

Conductor Conductor

Fibre Optic Cores

47 48 Appendix G - 2.0MW BLYTH OFFSHORE WIND TURBINE

BLADE TOP

NACELLE 95m

ACCESS PLATFORM

HIGHEST EVER RECORDED TIDE

LOWEST ASTRONOMICAL TIDE

NORTH SEA SEABED (MUDLINE) 6------mm—mm----- mm------LORRY DRAWN TO SAME SCALE AS TURBINE ROCK BOTTOM OF PILE