Galloper Wind Farm Eastern Super Grid Transformer Project Environmental Statement – Chapter 3 Project Details February 2014 Document Reference – GWF/25/02/2014 Galloper Wind Farm Limited CONTENTS Page 3 PROJECT DETAILS 3.1 Introduction 1 3.2 Outline Project Description 2 3.3 Alternatives Considered 2 3.4 Onshore Substation 3 3.5 Items to be Constructed under the DCO 4 3.6 Cabling 7 3.7 Sealing End Compound, Gantries, and Overhead Lines 7 3.8 Changes to the Galloper Wind Farm Onshore Site 7 3.9 Project Programme 8 3.10 Pre-Construction Site Investigations 8 3.11 Onshore Construction 9 3.12 Environmental Management during Construction 9 3.13 Commissioning 10 3.14 Substation Overview 10 3.15 Decommissioning 11 3.16 Local Community Relations 11 3.17 References 11 Figures Figure 3.1 Plan and elevation of Eastern Super Grid Transformer 5 Figure 3.2 Galloper Layout showing proposed redundant elements 6 Appendices 3.1 Galloper Wind Farm Construction Code of Practice Galloper Wind Farm – Eastern Super Grid Transformer Project Environmental Statement – Chapter 3 Project Details Final February 2014 3 PROJECT DETAILS 3.1 Introduction 3.1.1 This chapter of the Environmental Statement (ES) presents the details of the Galloper Wind Farm (GWF) Eastern Super Grid Transformer (ESGT) scheme and describes the construction, operation, maintenance and decommissioning components of the project, which would primarily comprise: • Securely fenced ESGT compound containing the following plant (see Figure 3.1): o One 400/132kVsuper grid transformer including cooling bank (s) o Transformer bund o Transformer noise enclosure o 3 single phase x 132kV cable sealing ends o 3 x 132kV and 3 x 400kV surge arrestor o One three phase x 132kV and one three phase x 400kV earth switch o 3 x 400kV current transformer o One three phase x 400kV circuit breaker o One three phase x 400kV disconnector o 9 x 400kV post insulator o 3 x 400kV voltage transformer o Hard standing including a standing (service) area o Gravelled areas o 1 x oil water separator including penstock valve and sampling chamber • Three single phase 1 x 132kV underground cables (i.e. one three phase circuit) connecting the existing Leiston substation to the ESGT cable sealing ends(see figure 1.2 for this and the following elements) • Underground cable connection between the GWF substation and the existing Leiston substation • Diversion of existing underground District Network Operator (DNO) supply which passes through ESGT area • Landscaping • Permanent and temporary access roads • Service corridors, including telecommunications, water, and connection to the local electricity network 3.1.2 In addition, the western most sealing end compound, which was consented as part of the GWF Development Consent Order (DCO), will be constructed immediately to the south of the ESGT compound. A temporary construction compound and associated temporary works such as an access track from the existing site access road and from the construction compound to the ESGT will be required and will be located within an area consented under the DCO as a temporary construction area. 3.1.3 The details provided in this chapter are based on the latest knowledge and information available at the time of production of this ES. A detailed design exercise will be undertaken before construction which will result in a refinement of the design but the compound would not exceed to maximum parameters described in this chapter. In some cases, specific information relating to the ESGT is not available (for example, the exact method of construction will not be confirmed until contracts have been tendered and awarded). As such, the construction methodology provided is based on similar projects. Galloper Wind Farm – Eastern Super Grid Transformer Project Environmental Statement – Chapter 3 Project Details Final February 2014 3.1.4 The ESGT will replace the requirement for the Leiston B substation which was to be constructed within Sizewell Wents woodland (Figure 3.2. The ESGT will transform the voltage and allow the electricity generated by GWF to be fed into the 400kV transmission network. The ESGT compound, at 0.57ha (including the consented sealing end compound) will be smaller than Leiston B. The original GWF scheme would have required 1.61ha of woodland to be felled to make room for the substation, cable corridors, and access road. The ESGT compound will require approximately 0.17ha of woodland to be removed – the underground cable between the GWF compound and the Leiston A substation will be laid along the consented access road and will not require any further trees to be felled. 3.2 Outline Project Description 3.2.1 As outlined in Chapter 1, Introduction, the ESGT project comprises a development of a substation compound including a Super Grid Transformer (SGT) and associated balance of plant within the GWF onshore site to the east of two existing substations. 3.2.2 Details of the project components considered for assessment are provided throughout this chapter, along with descriptive information on the methods associated with the construction, operation and decommissioning of these components. This information has been used to inform the technical chapters contained within this ES and is considered to represent the Project’s ‘development envelope’. 3.2.3 The other onshore infrastructure such as the Galloper substation will be constructed as planned and consented through the GWF DCO, with a number of exceptions which are outlined in Section 3.7. The location of the ESGT compound is described in Chapter 2, Site Description and Land Use. 3.3 Alternatives Considered 3.3.1 The ESGT is proposed as an alternative to the proposed Leiston B substation which was consented under the GWF DCO. Leiston B substation was to be constructed within the Sizewell Wents woodland and would have led to the loss of a total of 1.61ha of semi- mature woodland. Included in this figure, a cable corridor would have been required, running from the northern edge of Leiston B around the two existing substations and into the two sealing end compounds. The location of Leiston B and the associated cable corridor is shown in Figure 3.2. 3.3.2 The ESGT will only necessitate a small area of woodland to be felled (approximately 0.17ha), primarily consisting of immature trees. The compound will include the western most sealing end compound and therefore will only require a short cable corridor to connect into the Leiston substation. This will not require the removal of any woodland habitat. The proposed location of the ESGT compound is shown in Figure 1.1. 3.3.3 Underground cabling will be installed through Sizewell Wents woodland to connect the GWF substation with the Leiston A substation. The cabling will run along the consented permanent access road through the woodland and will not necessitate any further tree felling. Galloper Wind Farm – Eastern Super Grid Transformer Project Environmental Statement – Chapter 3 Project Details Final February 2014 3.4 Onshore Substation 3.4.1 The proposed location of the ESGT compound is within an area of semi-natural grassland predominately used for grazing, located to the east of the two existing GGOWF and Leiston substations. 3.4.2 The ESGT will contain one super grid transformer (SGT) and one 400kV breaker whereas Leiston B would have contained two SGTs. Two 400kV breakers, 132 kV switchboard and associated buildings and auxiliary plant. 3.4.3 The SGT will be the largest single piece of plant within the ESGT compound. It will be connected to the 400kV overhead line system via a series of plant shown in Figure 3.1. The equipment to be provided in the ESGT along with the approximate heights are listed in Table 3.1 below. The equipment is listed in the order in which it will be installed in the ESGT compound, from north to south. Each item is shown in plan and elevation on Figure 3.1 .It should be noted that the layout is preliminary and will be subject to detailed design and micrositing before construction commences. Table 3.1 Plant to be provided in the ESGT compound Description Number required Approximate height 132kV cable sealing end 3 4.3m 132kV earth switch 3 4m 132kV surge arrestor 3 4m 400/132kV super grid transformer 1 6.2m including cooling bank 400kV surge arrestor 3 6.8 400kV earth switch 3 7.3m 400kV current transformer 3 7.3m 400kV circuit breaker 3 7.3m 400kV disconnector 3 7.3m 400kV post insulator 3 7.3m 400kV voltage transformer 3 7.3m Gantry (within consented sealing end 1 12m compound) Note: an additional 6 post insulators will be included in the sealing end compound and were consented under the GWF DCO. 3.4.4 All of the equipment in the ESGT compound will be air insulated which means that it will be built outside and not housed in a building. The super grid transformer itself will be contained in a noise enclosure. 3.4.5 The 400/132kV super grid transformer will be protected by a bund wall which will offer containment for 110% of the volume of oil held in the transformer, compliant with The Control of Pollution (Oil Storage) (England) Regulations 2001. 3.4.6 The ESGT compound will be surrounded by an electrified fence which will be 3.6m high. The fence will be of steel palisade type with an electric pulse system mounted on top. A section drawing of the proposed fencing is included on Figure 3.1. Galloper Wind Farm – Eastern Super Grid Transformer Project Environmental Statement – Chapter 3 Project Details Final February 2014 3.4.7 The ESGT will be accessed via the existing site access road which services the Leiston and GGOWF substation compounds.