Landscape Susceptibility in relation to Energy Generation, Storage and Transmission - SPD

4.1.1 The types of energy-related development scenarios considered in this study are listed below. These are considered to be representative of projects that could realistically come forward within South Norfolk district within the foreseeable future and comprise solar PV (photovoltaic), AD (anaerobic digestion) plants, battery storage and electricity transmission and distribution works.

4.1.2 For each project type, different scales of development have been considered as set out below:

Solar PV

• small-scale solar PV projects, up to 5 MW
• medium-scale solar PV projects, 5 to 15 MW
• larger-scale solar PV projects, 15 to 50 MW

AD plants

• farm-scale, single or double tank system, up to 1ha
• larger installation, up to 5ha

Battery Storage

• up to 1ha in size

Overhead powerlines

• 132kV lines, utilising pylons within a nominal height of 26m
• 400kV, utilising pylons with a nominal height of 50m

Underground cable routes

• Comprising cable route and associated works

Substations

• Substations are typically required to connect generating facilities to the distribution network and so often found in association with other energy project types.

4.1.3 It is envisaged that this study will complement the South Norfolk District Wind Turbine Landscape Sensitivity Study (Land Use Consultants, 2006 – final amendments 2008). As such, wind turbines have not been considered in this study.

4.2.1 Energy-related developments can also include combustion power stations (including biomass plants, advanced conversion technologies, landfill gas projects, and natural gas-fired plants) and nuclear power stations.

4.2.2 Biomass plants are already present in the local area at Thetford, Snetterton and Eye. Thetford Biomass Power Station is run primarily on poultry litter and woodchip while Snetterton and Eye are primarily straw fired. The potential for this technology is limited by the available feedstock so it is unlikely that new plants will be required in the foreseeable future.

4.2.3 Landfill gas projects have been implemented across many landfill sites in Norfolk. The potential for this technology is clearly limited geographically to existing landfill sites, so it is not considered further in this study.

4.2.4 Advanced conversion technologies (ACT) are designed to recover energy from waste. ACT is considered the next generation of thermal heat treatment and can be applied to a variety of feedstocks. Most ACT plants produce a gaseous product known as syngas. The adoption of this technology has been slow and the amount of electricity that can be generated is limited by the available feedstock.

4.2.5 Natural gas-fired power stations are large installations. Natural gas remains part of the present energy mix but will eventually be phased out. The nature of this technology means that it is limited to a few large sites, and it is therefore unlikely that this form of energy-related development would come forward within South Norfolk.

4.2.6 Nuclear power stations are situated on the coast and would not therefore be located within South Norfolk.

4.3.1 For each of the development scenarios considered in the LSS, the following matters are considered:

• Overview of the development type
• Development scales considered in the LSS
• Parameters assumed in the LSS
• Potential landscape effects
• Cumulative effects
• Design development guidelines

4.3.2 The design development guidelines relate to landscape susceptibility only and do not address sensitivities relating to other areas of potential environmental impact, or other non-landscape considerations which might affect the feasibility of development.

4.3.3 The guidelines are generic and apply to all the LTs and LCAs.

Generic development guidelines

4.3.4 The following siting or design development guidelines are applicable to all development scenarios:

• The effects of the proposed development on landscape and visual receptors should be tested throughout the siting and design process by landscape and visual impact assessment to ensure adverse effects are minimised.
• Trees, hedges and other woody vegetation at the site should be retained wherever possible and protected during the construction works in accordance with BS5837:2012, to ensure their long-term health and viability, and contribution to the landscape.
• Disturbance of soils should be minimised. Where necessary, the existing soils at a site should be stripped prior to works commencing, separated into topsoil and subsoil, and stored in a manner that would safeguard their long-term health. On completion of the building works the soils should be used as part of the landscape scheme.
• Development (buildings and surfaces) should be located in a manner that retains the general character of the surrounding landform, where it can be accommodated without abrupt changes in levels or steep gradients or the need for prominent retaining structures or bunds. Where possible, levels should follow the wider contours and general gradient.
• Consider the landscape effects of drainage features such as SuDs, which can have a highly engineered form and suburbanising associated paraphernalia. Ensure they have sufficient space to enable shallow sides and opportunities for habitat creation, so as to create meaningful and positive additions to the landscape.
• Ensure that any earthworks, including artificial mounds that might be used to screen the development, and sensitively designed in terms of height, profile and gradient, to fit in with the surrounding landscape. Generally, such features do not provide effective growing conditions for planting.
• Boundary features such as hedges should be retained in a meaningful and continuous manner.
• Development at a site should be accompanied by a comprehensive landscape scheme with an appropriate landscape management plan to guide its implementation and ongoing maintenance and ensure its long term contribution to the landscape. The scheme should be implemented in a timely manner in the first available planting season.
• New planting should be designed using appropriate and predominantly native planting so as to reflect the character of the wider landscape, with plant species selected to minimise long term maintenance and maintenance, with a view to being resilient to future climate change.

4.4.1 Cumulative effects are effects "that result from incremental changes caused by other past, present or reasonably foreseeable actions together with the project." ^[7] Cumulative landscape and visual effects would result from additional changes to the landscape or visual amenity caused by the proposed development in conjunction with other development(s) (associated with, or separate to, it).^[8]

4.4.2 The guidelines for minimising cumulative impact are as follows:

• When assessing the potential effects of a proposed scheme, reference should be made to the relationship between the proposal and any existing, consented or proposed energy-related developments within the district, and especially within the same character area or neighbouring landscape character areas.
• The character of existing developments in relation to the landscape should be considered. If there is a distinct pattern of development in a particular type of landscape, then continuation of this pattern would have less of an impact on character than the introduction of a different size or form of development in an undisturbed location.
• The closer developments are to each other the more likely they are to be viewed in combination (or in sequence).
• Even if developments are not visible from the same viewpoint the cumulative effects on character still need to be considered as they can have an effect on the experience of moving through a landscape (sequential effects).
• In many scenarios, locating new development in proximity to existing development could be considered to minimise its impact and preserve the more undisturbed and tranquil parts of the district. The combined effects of different developments could, however, change the fundamental character of an area if the common characteristics of the developments were to become the defining characteristics of the area.
• Cumulative effects relate primarily to the amount of development within a given landscape, as well as to intervisibility, intra-visibility and sequential effects.^[9] Good design could reduce cumulative effects by avoiding intervisibility for example.
• Whilst it might be argued that only developments which are intervisible can have cumulative effects, this is not necessarily the case. Developments which are scattered across the landscape might be considered to affect a broader area, and to affect the perception of the area as a whole and/or the sequential experience of travelling through it.

Overview of the development type

4.5.1 Solar PV developments comprise arrays of solar photovoltaic panels that are mounted on frames. The back panel height is typically up to 3m. The panels are usually positioned at a fixed angle of 20-40 degrees from the horizontal facing south and sited in parallel rows with gaps between the rows for access and to prevent shading of adjacent rows. Frames can be fixed in position through piles driven into the ground or placed on concrete shoes, avoiding the need for mass concrete foundations. The solar arrays are typically accompanied by inverters, transformers, and small buildings such as substations. The proposals typically include a 2m high post and wire fence, pole-mounted CCTV cameras, and access tracks. Some security lighting may be proposed in conjunction with the buildings.

4.5.2 Solar installations tend to be measured by their capacity in megawatts. 1 MW of installed capacity occupies, on average, 2ha of land.

4.5.3 Schemes of over 50 MW are defined as NSIPs and are determined by the Secretary of State rather than the local planning authority.

4.5.4 Solar PV developments typically have an operational life of 25 to 40 years and planning permissions are usually limited in terms of their duration. The solar farm owner and landowner are responsible for the decommissioning of solar PV developments. Planning conditions can be used to ensure that installations are removed when no longer in use, and to ensure that the land is restored to its previous (or another agreed) use.

4.5.5 Whilst solar PV can in theory be installed almost anywhere, there are technical considerations such as the capacity of the local substations.

Scenarios considered in the LSS

4.5.6 Three scales of solar PV project are considered in this study:

• small-scale solar PV projects, up to 5 MW
• medium-field solar PV projects, 5 to 15 MW
• larger-scale solar PV projects, 15 to 50 MW

Parameters assumed in the LSS

4.5.7 For the purposes of the LSS, the following parameters are assumed for solar PV developments:

• Small-scale solar PV projects, up to 5 MW – typically 5 to 10ha and contained within a single field unit.
• Medium-scale solar PV projects, 5 to 15 MW – typically 10 to 30ha and extending over a small number of fields.
• Larger-scale solar PV projects, 15 to 50 MW – typically 30 to 100ha and encompassing several fields.
• Ground mounted panels up to a maximum of 4m high.
• 2m high security fencing, comprising deer fencing with a low visual presence.
• No external lighting, save that for emergency attendance.
• Grazed or habitat enhancement ground cover.
• Timely implementation of a well-considered and maintained landscape scheme to integrate the development into the surrounding landscape framework.
• 25 year life, followed by full decommissioning and removal of all structures and a return to an agricultural land use or habitat creation typical of the LCA.

Potential landscape effects

4.5.8 Solar PV developments, although not prominent in terms of height, can occupy substantial areas of ground and may be quite visible, particularly if located on slopes. Landscape effects may include the following:

• As extensive developments, solar arrays may be particularly visible in open landscapes, on slopes, or where overlooked, especially where covering significant areas.
• On a sunny day they can appear blue while on a cloudy day they can appear a dark grey, both of which contrast with surrounding green areas.
• The presence of PV panels and associated infrastructure may increase the perceived human influence on the landscape and change land cover patterns of rural landscapes.
• Solar PV developments will change the land use and appearance of a field or fields, affecting land cover patterns.
• The regular edges of solar PV developments may be conspicuous in more irregular landscapes (particularly where they do not follow contours or where field boundaries are irregular in form).
• The height of the panels means that they may over-sail typical hedgerow field boundaries.
• Screen planting around solar PV development can change the sense of enclosure of a landscape (NB: some changes in management, such as allowing hedges to grow out, may enhance diversity and local landscape character resulting in positive change but may in turn block valued longer distance views across the wider landscape).
• Construction of the solar PV development may result in damage to landscape features such as hedgerow field boundaries and alter the landscape scale.
• Conversely, mitigation for a PV development can include large scale planting schemes which can enhance the biodiversity of a field and diversify the local habitats.
• Structures may appear out of place in particularly wild or undeveloped landscapes which are valued for their qualities of remoteness.
• Ancillary buildings and security requirements (such as fencing and/or CCTV) may introduce new and unfamiliar features into the landscape, increasing the perceived human influence on the landscape and erode the intrinsically rural character. Often, these elements can have more influence than the panels themselves.
• Solar PV schemes can take fertile agricultural land out of production for many years.
• Solar schemes might intercept or disrupt the route of existing public rights of way, or influence the experience and aspect of those using it.
• In a more open landscape, foreground mitigation planting may have the unintended effect of blocking or altering the composition of longer distance views.
• Where multiple field units are involved, consideration should be given to the sequential influence of solar PV as it is experienced by those moving through the landscape, e.g. on public rights of way.

Cumulative effects

4.5.9 There are a number of existing Solar PV developments within South Norfolk. At the time of writing, a map of consented and proposed renewable energy schemes within South Norfolk is provided on the Council's website: Renewables mapping | Broadland and South Norfolk

4.5.10 Considering the presence of several solar PV arrays in South Norfolk district, and the continued pressure for this type of development, it is important that consideration is given to their cumulative effects when they can be appreciated in close proximity to other similar developments and/or other energy-related infrastructure that they often need to connect to, such as substations.

Design development guidelines

4.5.11 The following guidelines are relevant to the siting and design of solar PV developments in South Norfolk:

• Locate development on lower slopes/within folds in gently undulating lowland landscapes or on flat plateau sites, rather than on slopes, especially higher slopes, crests and plateau edges.
• Site solar development in landscapes with a sense of enclosure (e.g. provided by woodland or high hedges) rather than in open and unenclosed landscapes (unless on an elevated plateau lacking intervisibility with surrounding landscapes).
• Avoid areas of greater time depth – e.g. historic landscape types such as commons, co-axial enclosures or parklands, and landscapes that form part of the setting of a conservation area, listed building, or park.
• Avoid development that adversely affects the setting of The Broads, the openness of the Norwich Southern Bypass Landscape Protection Zone, views to Norwich or the undeveloped approaches to Norwich.
• Consider views from local viewpoints, settlements (particularly Conservation Areas) and popular walking or cycling routes such as the Boudicca Way. If development will be visible ensure it does not dominate and detract from the experience of visiting these locations/ travelling along these routes, either in terms of individual field units or as the sequence of passing through multiple fields.
• Ensure the area or extent of development is in scale with the landscape in which it lies – it is likely that areas with smaller-scale fields would more easily accommodate smaller developments.
• Solar PV arrays are better suited to areas with a rectilinear field pattern. Within a field the space between panels should be consistent and logical.
• The layout should avoid effects on existing trees and hedges. Since panels are unlikely to be positioned where they would be shaded by vegetation, this is usually relatively easily achieved. Panels should be set back from boundaries to maintain the legibility of field patterns (and also to assist with hedgerow management and potentially to provide habitat). Care should be taken that the associated infrastructure does not conflict with tree root protection areas.
• Panel heights should be kept as low as possible, to minimise visual effect. Where relevant, sufficient space must, however, be provided below the panels for sheep grazing or habitat creation.
• The creation of new tracks for access to solar arrays will increase the landscape impact. Where new tracks are needed, they should as far as possible follow field boundaries. Temporary trackways should be used where possible to minimise longer-term effects.
• Ancillary buildings or structures, such as substations, transformers and inverters should be located in inconspicuous locations. The local vernacular should be considered in relation to buildings – see also comments in relation to substations.
• Dark, recessive colours in non-reflective materials should be chosen for panel frames and ancillary structures, and where appropriate, fencing.
• Minimise the use of security lighting. Use of infrared security cameras could avoid the need for new lighting altogether.
• Grid connections should be via underground cable.
• Fences should be set back from surrounding hedges, to reduce their apparent height when viewed from beyond the boundary.
• Efforts should be made to maintain land uses on the site that fit with the character of the surrounding area. The spaces between and around the solar arrays can be utilised productively for grazing or habitat creation.
• Hedgerows can be managed to provide ecological benefits as well as screening, which may include the strengthening of existing field boundaries, or introduction of new planting.
• Hedges can provide effective landscape mitigation, either by managing them at higher levels or planting new hedges. However, care should be taken that such hedges do not block long distance views or create a tunnel or corridor effect, for example where planted in association with public rights of way.
• Incorporate biodiversity net gain into any new development and consider opportunities to contribute to the delivery of the Green Infrastructure network in South Norfolk.
• As a temporary development it will be important to demonstrate that the development can be decommissioned effectively and that the landscape can be restored to at least as good a condition as it was prior to the development taking place.

Overview of the development type

4.6.1 Anaerobic digestion (AD) is a natural process where animal or plant materials (biomass) is broken down by microorganisms in the absence of air. The resultant methane-rich biogas can be used to create renewable energy.

4.6.2 AD plants can be classified into two general categories: those that process predominantly agricultural feedstock (such as manures, slurries, crops and crop residues), and those that use predominantly municipal, commercial and industrial waste streams as feedstock. The biogas produced can either be burned on site to generate heat and/or power (Combined Heat and Power – CHP) or upgraded to biomethane for injection into the national gas grid.

4.6.3 Built forms relating to AD plants generally comprise fermentation tanks, which can be inflatable, and associated buildings/ancillary structures including gas to grid processing units, Combined Heat and Power (CHP) units, control buildings and feedstock storage including silage clamps. The largest (and most distinctive) elements tend to be the circular storage tanks (which can vary in size from 2.75 to 30.5m in diameter and 1.5m to 33.5m in height) and the flare stack (typically 3 to 5m in height). The feedstock storage areas can be quite extensive and the total site area varies from around 2ha up to 9ha. AD Plants are assumed to be permanent.

Scenarios considered in the LSS

4.6.4 Two scenarios for AD plants are considered in this study:

• farm-scale, single or double tank system, up to 1ha
• larger installation, up to 5ha

Parameters assumed in the LSS

4.6.5 For the purposes of the LSS, the following parameters are assumed for AD plants:

• 16m high tanks
• Security fencing
• Lightning conductor rods
• Timely implementation of a well-considered and maintained landscape scheme to integrate the development into the surrounding landscape framework.

Potential landscape effects

4.6.6 Landscape effects from AD plants may include the following:

• Direct loss of landscape features within the area developed.
• The tanks and/or the flare stack can be a prominent feature in the landscape.
• The bulky industrial style structures can increase the sense of human influence and introduce an industrial character in what might otherwise be a relatively rural landscape.
• Vehicle movements, ancillary activities/storage, security and flood lighting associated with these developments can also increase human influence in more naturalistic or rural landscapes.
• Engineered drainage features such as SuDS features and earthworks, including artificial mounds that might be used to screen the development, can have an intrusive effect in the landscape.

Cumulative effects

4.6.7 AD plants are not particularly common, and cumulative effects are therefore unlikely. At the time of writing, a map of consented and proposed renewable energy schemes within South Norfolk is provided on the Council's website: Renewables mapping | Broadland and South Norfolk

Design development guidelines

4.6.8 The following guidelines are relevant to the siting and design of AD plants in South Norfolk:

• Aim to locate new structures close to existing built form (e.g. existing electricity substation infrastructure) or in areas which are already well screened by existing vegetation.
• Ensure the scale of development is appropriate for its context.
• The materiality and colours of the proposed structures will be important in terms of their effects on the landscape. Consultation with the LPA will be required to develop the most appropriate design.
• Protect the existing network of hedgerows, woodlands, and semi-natural habitats and aim to extend these as part of any landscape scheme associated with development.
• Enhance existing screening through planting that integrates with features such as woodland and hedgerows within the wider landscape, to reinforce local character and biodiversity.
• Protect undeveloped skylines and backdrops from encroachment – set any new built development back from valley crests and avoid highly visible slopes.
• Ensure that existing landmark features remain prominent in the landscape and new development does not detract from these features.
• Plants should be carefully sited to take advantage of existing screening. Avoid exposed locations.
• Avoid areas with greater time depth such as pre-18th century fields and common land, or areas of higher landcover interest such as unimproved grassland.
• Avoid development which adversely affects the setting of The Broads, the openness of the Norwich Southern Bypass Landscape Protection Zone, views to Norwich or the undeveloped approaches to Norwich.
• Schemes should be limited to small scale plants that can be easily contained within an existing farmyard setting and operate without the need to import material from other farms.
• Consider the landscape effects of drainage features such as SuDS, which can have a highly engineered form and introduce ancillary infrastructure. Ensure they have sufficient space to enable shallow sides and opportunities for habitat creation, so as to create meaningful and positive additions to the landscape.
• Ensure that any earthworks, including artificial mounds that might be used to screen the development, are sensitively designed in terms of height, profile and gradient, to fit in with the surrounding landscape. Generally, such features do not provide effective growing conditions for planting.
• Consider views from local viewpoints, settlements (particularly Conservation Areas) and popular routes (e.g. walking or cycling route). If development will be visible, ensure it does not dominate and detract from the experience of visiting these locations/ travelling along these routes.
• Consider use of green roofs.
• The local vernacular should be considered in relation to buildings.
• Ensure planting around the buildings reflects the underlying landscape character by using locally-appropriate species and linking to the existing green infrastructure network.
• Minimise the use of security lighting. Use full cut-off light fittings to avoid any direct upward light and ensure that lighting is designed to minimise light spill into the surrounding landscape. Consider use of infrared cameras to avoid the need for lighting.
• Consider providing enhanced management of landscape features, habitats and historic assets as part of any development.
• Incorporate biodiversity net gain into any new development and consider opportunities to contribute to the delivery of the Green Infrastructure network in South Norfolk.

Overview of the development type

4.7.1 Battery storage facilities enable energy from renewable sources to be stored and later transferred back to the grid. They are sometimes referred to as battery energy storage systems (BESS).

4.7.2 Battery storage facilities comprise individual battery units (which normally consist of free-standing units) and associated inverters (which convert DC battery power to AC grid power), transformers (transferring power between the grid and the batteries) and switchgear/control room building/cabin all within a fenced compound which may require ground levelling.

4.7.3 The scale of commercial battery storage schemes is highly variable, depending on the required storage capacity. There are technical constraints on where battery storage can be located as they have to be situated close to existing transmission lines. battery storage facilities are increasingly being co-located with solar arrays to allow excess power to be stored and later transferred back to the grid, to improve the economic viability of solar farms.

4.7.4 A typical site area for a 50MW capacity battery storage is likely to be around 1ha in size, depending on the battery technology used. The relatively small size of the battery storage allows some flexibility in terms of their exact siting.

4.7.5 Although batteries and other components have a design life, planning permissions are not typically limited in duration, and battery storage installations are therefore assumed to be permanent. As such, it is not assumed that sites would be returned to the previous use at the end of the operation phase.

Scenarios considered in the LSS

4.7.6 A single scale of battery storage is considered in this study.

Parameters assumed in the LSS

4.7.7 For the purposes of the LSS, the following parameters are assumed for battery storage:

• Battery storage cabinets up to 3m high
• Security fencing – steel palisade or mesh, up to 2.75m high
• Transformers inverters
• Switchgear/control room building/cabin
• Cable connection to grid
• No external lighting, save that for emergency attendance
• Timely implementation of a well-considered and maintained landscape scheme to integrate the development into the surrounding landscape framework.

Potential landscape effects

4.7.8 The following landscape effects may arise from Battery Storage:

• Direct loss of landscape features within the area developed.
• The bulky industrial style structures can increase the sense of human influence and introduce an industrial character in what might otherwise be a relatively rural landscape.
• Vehicle movements, ancillary activities/storage, security and flood lighting associated with these developments can also increase human influence in more naturalistic or rural landscapes.
• Engineered drainage features such as SuDS features and earthworks, including artificial mounds that might be used to screen the development, can have an intrusive effect in the landscape.

Cumulative effects

4.7.9 There are a number of approved battery storage schemes within South Norfolk including the Hornsea 3 Energy Balancing Infrastructure. At the time of writing, a map of consented and proposed renewable energy schemes within South Norfolk is provided on the Council's website: Renewables mapping | Broadland and South Norfolk

4.7.10 There is likely to be increased pressure in the future for battery storage in the South Norfolk district. Consideration should be given to the cumulative effectives on landscape features that might arise from any new battery storage (including associated substations) when they can be appreciated in close proximity to existing facilities and/or other energy infrastructure.

Design development guidelines

4.7.11 The following guidelines are relevant to the siting and design of Battery Storage developments in South Norfolk.

• Aim to locate new structures close to existing built form (e.g. existing electricity substation infrastructure) or in areas which are already well screened by existing vegetation.
• Ensure the scale of development is appropriate for its context.
• The materiality and colours of the proposed structures will be important in terms of their effects on the landscape. Consultation with the LPA will be required to develop the most appropriate design.
• Protect the existing network of hedgerows, woodlands, and semi-natural habitats and aim to extend these as part of any landscape scheme associated with development.
• Enhance existing screening through planting that integrates with features such as woodland and hedgerows within the wider landscape, to reinforce local character and biodiversity.
• Protect undeveloped skylines and backdrops from encroachment – set any new built development back from valley crests and avoid highly visible slopes.
• Ensure that existing landmark features remain prominent in the landscape and new development does not detract from these features.
• Avoid areas with greater time depth such as pre-18th century fields and common land.
• Avoid locating in open, undeveloped landscapes or areas with historical significance e.g. parklands. Avoid loss of areas of greater landcover interest, such as unimproved grassland or deciduous woodland.
• Avoid development which adversely affects the setting of The Broads, the openness of the Norwich Southern Bypass Landscape Protection Zone, views to Norwich or the undeveloped approaches to Norwich.
• Consider the landscape effects of drainage features such as SuDS, which can have a highly engineered form and introduce ancillary infrastructure. Ensure they have sufficient space to enable shallow sides and opportunities for habitat creation, so as to create meaningful and positive additions to the landscape.
• Ensure that any earthworks, including artificial mounds that might be used to screen the development, are sensitively designed in terms of height, profile and gradient, to fit in with the surrounding landscape. Generally, such features do not provide effective growing conditions for planting.
• Consider views from local viewpoints, settlements (particularly Conservation Areas) and popular routes (e.g. walking or cycling route). If development will be visible, ensure it does not dominate and detract from the experience of visiting these locations/ travelling along these routes.
• Consider use of green roofs.
• The local vernacular should be considered in relation to buildings.
• Ensure planting around the buildings reflects the underlying landscape character by using locally-appropriate species and linking to the existing green infrastructure network.
• Minimise the use of security lighting. Use full cut-off light fittings to avoid any direct upward light and ensure that lighting is designed to minimise light spill into the surrounding landscape. Consider use of infrared cameras to avoid the need for lighting.
• Consider providing enhanced management of landscape features, habitats and historic assets as part of any development.
• Incorporate biodiversity net gain into any new development and consider opportunities to contribute to the delivery of the Green Infrastructure network in South Norfolk.

Overview of the development type

4.8.1 Overhead powerlines consist of overhead wires suspended on wooden poles or steel pylons. The National Grid infrastructure in England is largely made up of 400 kV and 132 kV lines. Besides this there is also infrastructure that belongs to the distribution network operator (DNO) i.e. UK Power Networks.

4.8.2 Electricity pylons were first introduced in 1928 when the National Grid was created, and the basic design of the pylon has remained largely the same since then. The National Grid initially consisted of 132 kV lines, but higher voltage lines requiring larger pylons were introduced in the 1960s.

4.8.3 Overhead powerlines are suspended on steel lattice towers (commonly known as pylons). There are three basic types of towers, straight line towers, angle towers, and terminal towers. Most lines are double circuit and feature towers with three symmetrical cross arms. Angle towers are bulkier than straight line towers. They have tensions insulators rather than suspension insulators and can be asymmetrical. 132 kV lines typically use towers of around 26m in height^[10] while 400 kV lines typically use towers of around 50m in height.^[11] This standard height can, however, be varied. The largest lines use two or four wire bundles separated by spacers.

4.8.4 132 kV and 400 kV overhead lines of over 2km length are defined as NSIPs and are determined by the Secretary of State rather than the local planning authority.

Scenarios considered in the LSS

4.8.5 Two scenarios for above ground energy transmission are considered in this study:

• 400kV lines that utilise the largest pylons. These are typically owned by National Grid and transmit electricity from where its generated (e.g. power stations) to substations.
• 132kV lines that utilise smaller pylons. These are operated by DNOs and distribute electricity from the substations to homes, businesses, etc.

Parameters assumed in the LSS

4.8.6 For the purposes of the LSS, the following parameters are assumed for overhead transmission lines:

• 400kV lines – pylons with a nominal height of 50m
• 132kV lines – pylons with a nominal height of 26m

Potential landscape effects

4.8.7 Overhead power lines may affect the landscape in the following ways:

• Introduction of tall (frequently the tallest) features into the landscape. As a comparison, commercial warehouses are typically have a ridge height 14m, housing a ridge height of 9m to 12m, and a mature oak 20m to 25m.
• Pylons are inevitably seen as new, and frequently dominant, features in the landscape that introduce a strong sense of modernity.
• The size of the structures and the frequency of the pylon repeat patterns is often in stark contrast with and out of scale to smaller scale, finer grain landscape patterns and features.
• Cables that contrast, in terms of colour, against the prevalent landscape colour, e.g. sky or woodland. Colouring cables green can often make them look more prominent since the green appears artificial against more muted natural tones.
• Pylon construction (and replacement) can involve considerable disruption. Pylons are frequently located in rural or remote locations and temporary access roads are often required.
• Need for ongoing vegetation clearance can affect the landscape underneath transmission lines. Vegetation management can have consequential effects on the character of the landscape below the transmission line.
• Addition of lights on lines (as ecological mitigation measure) would have consequential effects on the landscape, particularly in terms of night-time effects.

4.8.8 Consideration should be given to consequential additions to the landscape that would inevitably arise with overhead lines and pylons, such as extensions to existing or new substations.

4.8.9 Overhead power lines can in theory be decommissioned, i.e. removed when no longer needed, or replaced with underground cables. The DNO (UK Power Networks) has for example taken down power lines between Earlham and Bowthorpe and replaced them with underground cabling.

Cumulative effects

4.8.10 Cumulative effects on landscape and visual receptors might arise from any new overhead power lines when they can be appreciated in close proximity to existing lines and associated infrastructure such as pylons and substations and/or other energy facilities such as battery storage systems.

4.8.11 Existing overhead transmission infrastructure in South Norfolk includes the 400 kV Norwich Main-Bramford power line, the 400 kV Norwich Main-Walpole power line, the 132 kV Norwich Main-Earlham Grid, the 132 kV Norwich Main-Trowse Grid, the 132 kV line between Trowse and Lowestoft, and the 132 kV line between Bramford and Lowestoft.

4.8.12 National Grid Electricity Transmission (National Grid) are proposing to build c.184km of new electricity transmission in order to reinforce the high voltage power network in East Anglia between existing substations at Norwich Main in Norfolk, Bramford in Suffolk, and Tilbury in Essex, as well as to connect new offshore wind generation. The project is known as Norwich to Tilbury. Norwich to Tilbury meets the current criteria of an NSIP.As such, an application for Development Consent will be submitted to the Planning Inspectorate. If consent for the project is awarded, this would be granted in the form of a Development Consent Order (DCO) from the Secretary for State for Business, Energy and Industrial Strategy following a public examination of the application.

4.8.13 Within South Norfolk, the overhead line and associated pylons would extend from the Norwich Main Substation south south-westwards through the district parallel with, and to the west of, the A140, before crossing the Waveney Valley to the west of Diss.

Holford Rules

4.8.14 Guidelines on the routeing of overhead lines were first formulated in 1959 by Sir William (later Lord) Holford and became known as the Holford Rules. It is acknowledged that present day environmental assessment has a wider remit than the visual amenity that the Holford Rules concentrate on. Nonetheless, National Grid has reviewed the guidelines and concluded that they remain relevant.

4.8.15 Rule 1:

Avoid altogether, if possible, the major areas of highest amenity value, by so planning the general route of the first line in the first place, even if the total mileage is somewhat increased in consequence.

4.8.16 A sub note to Rule 1 requires that designers should "Investigate the possibility of alternative routes, avoiding if possible the areas of the highest amenity value" and, importantly, that "The consideration of alternative routes must be an integral feature of environmental statements."

4.8.17 Rule 2:

Avoid smaller areas of high amenity value, or scientific interests by deviation; provided that this can be done without using too many angle towers, ie the more massive structures which are used when lines change direction.

4.8.18 The sub note to Rule 2 notes that "Where possible choose routes which minimise the effects on the setting of areas of architectural, historic and archaeological interest including Conservation Areas, Listed Buildings, Listed Parks and Gardens and Ancient Monuments."

4.8.19 Rule 3:

Other things being equal, choose the most direct line, with no sharp changes of direction and thus with fewer angle towers.

4.8.20 Sub note of Rule 3: "Where possible choose inconspicuous locations for angle towers, terminal towers and sealing end compounds."

4.8.21 Rule 4:

Choose tree and hill backgrounds in preference to sky backgrounds wherever possible; and when the line has to cross a ridge, secure this opaque background as long as possible and cross obliquely when a dip in the ridge provides an opportunity. Where it does not, cross directly, preferably between belts of trees.

4.8.22 Rule 5:

Prefer moderately open valleys with woods where the apparent height of towers will be reduced, and views of the line will be broken by trees.

4.8.23 Sub note on Rules 4 and 5: "Utilise background and foreground features to reduce the apparent height and domination of towers from pan viewpoints", "Minimise the exposure of numbers of towers on prominent ridges and skylines", "Where possible avoiding cutting extensive swathes through woodland blocks and consider opportunities for skirting edges of copses and woods", "Protecting existing vegetation, including woodland and hedgerows, and safeguard visual and ecological links with the surrounding landscape".

4.8.24 Rule 6:

In country which is flat and sparsely planted, keep the high voltage lines as far as possible independent of smaller lines, converging routes, distribution poles and other masts, wires and cables, so as to avoid a concentration or 'wirescape'.

4.8.25 Sub note 6 continues the commentary on cumulative effects:

In all locations minimise confusing appearance. Arrange wherever practicable that parallel or closely related routes are planned with tower types, spans and conductors forming a coherent appearance; where routes need to diverge, allow where practicable sufficient separation to limit the effects on properties and features between the lines.

4.8.26 Rule 7:

Approach urban area through industrial zones, where they exist; and when pleasant residential and recreational land intervenes between the approach line and the substation, go carefully into the comparative costs of the undergrounding, for lines other than those of the highest voltage.

4.8.27 Sub note for Rule 7 includes:

… Alignments should be chosen after consideration of effects on the amenity of existing development and on proposals for new development. When siting substations take account of the effects of the terminal towers and line connections that will need to be made and take advantage of screening features such as ground form and vegetation.

4.8.28 Supplementary notes include:

Avoid routeing close to residential areas as far as possible on grounds of general amenity.

Where possible choose routes which minimise the effect on Special Landscape Areas, areas of Great Landscape Value and other similar designations of County, District or Local value

4.8.29 Other design development guidelinesThe following guidelines should be considered when designing overhead powerlines:

• Overhead powerlines are tall structures, with a standardised design. The mitigation of effects is therefore difficult as it is rarely possible to screen pylons with planting, nor is it possible for the structures to reflect local identity. The main aspect of good design then relates to the choice of alignment and the siting of individual pylons within the landscape.
• Power lines follow straight paths and are better suited to large-scale landscapes with rectilinear field patterns.
• Simple plateau landscapes are more able to accept overhead powerlines than areas with intricate landform.
• Whilst valleys are sometimes preferred for overhead cable routes this would be inappropriate for South Norfolk as the pylons would overwhelm the shallow valleys.
• Consider following the route of existing powerlines to minimise the area which is affected by overhead powerlines and to preserve the remaining areas of undisturbed countryside. [Conversely, in such scenario, consideration must also be given to cumulative effects].
• Angle towers are bulkier than suspension towers and include tension insulators rather than suspension insulators. Sharp changes of direction require unattractive asymmetrical towers and should be avoided. The number of angle towers should be as few as possible and angle towers should also be placed in inconspicuous locations where possible.
• Termination towers are squat and are particularly unattractive, while cable sealing ends add further infrastructure to the landscape. The number of these features should therefore be as few as possible.
• Ancillary features such as cable sealing ends and substations should as far as possible be sited in conjunction with existing infrastructure to minimise harm. These features should also be sited in inconspicuous locations.
• Consider whether use of T-pylons might reduce the potential landscape effects.
• Consult with public on different designs of pylon and other options such as following existing overhead transmission routes.

4.8.30 There is a presumption that underground cable routes are more appropriate than overhead powerlines within protected or more sensitive landscapes. The effect of overhead powerlines within the setting of the National Park will also have to carefully considered to avoid effects on the designated landscape.

Overview of the development type

4.9.1 Underground cable routes refer to underground electricity transmission infrastructure. Cables are employed to connect energy generating infrastructure (e.g. offshore windfarms) with the National Grid via a substation. The National Grid uses underground cable routes within particularly sensitive landscapes for example National Parks and National Landscapes, and lower voltage underground cables are also used to distribute power at the district level.

Scenarios considered in the LSS

4.9.2 The study considers a single scale of cable route.

Parameters assumed in the LSS

4.9.3 For the purposes of the LSS, the following parameters are assumed for underground cable routes:

• Up to six separate trenches, works corridor up to 100m wide.
• Use of trenchless crossings to avoid effects on sensitive features and habitats.
• Removal of all temporary haul routes, compounds and bellmouths at the end of the implementation phase.
• Timely implementation of a well-considered and maintained landscape scheme to reinstate landscape features and make good any damage to the landscape.

Potential landscape effects

4.9.4 For underground cabling, the most pronounced effects are generally during the implementation phases of the project.

4.9.5 Underground cable corridors can be installed via either open cut trenching or horizontal directional drilling (HDD) for shorter distances, which does not require a trench. HDD is typically used for only the most sensitive areas, such as woodland and watercourses.

4.9.6 Some larger offshore windfarms may require multiple trenches. Construction works typically include fencing, vegetation clearance and topsoil stripping and storage, temporary haul routes, the excavation of a trench, the installation of cable ducts, backfilling, cable pulling and reinstatement works. The width of land which is typically required for a cable corridor falls within the range of 30-100m. Typical buried depths are 1.2 to 2m and trenches may be up to 5m wide at the surface.

4.9.7 Following completion of trenching and laying of cable routes permanent residual effects on the landscape include inspection chambers for cable jointing bays and marker posts indicating the location of the cable routes. Cable sealing ends add physical structures that link above and below ground sections of the route. In terms of decommissioning it is understood that cables are normally left buried in the ground at the end of the operation phase.

4.9.8 Cable trenches may affect the landscape in the following ways:

• Laying of the cable can result in direct loss of landscape features along the route (such as trees and sections of hedgerows) and disturbance to ground over long distances. Whilst hedges are typically replanted, trees are not generally replaced.
• Cables are generally laid in straight lines and the temporary trench can be visible over long distances, particularly if it is located in an elevated position or on steep slopes.
• The construction activities can affect characteristics of stillness, remoteness and solitude – although this is temporary.
• Post-construction, the recovering vegetation can produce scarring of the landscape. The time taken for vegetation to recover will depend on the type of landcover and standards of post-construction maintenance. Soil compaction on clay soils can result in long term drainage issues potentially affecting productivity.

Cumulative effects

4.9.9 It is unlikely onshore cable routes would result in notable cumulative effects beyond the implementation phases.

4.9.10 Consented cable routes within South Norfolk include:

• Sheringham Shoal Extension Project and Dudgeon Extension Project (Development Consent Order: E010109).
• Hornsea Three onshore cable corridor (PINs reference: EN010080).

Design development guidelines

4.9.11 The following guidelines should be considered when designing the route for underground cables:

• Minimise the width of the required corridor.
• Ensure successful ground re-instatement/restoration can be achieved.
• Use horizontal directional drilling (HDD) in sensitive locations to conserve above-ground features such as important or irreplaceable trees, hedgerows or nature reserves.
• Avoid steep slopes wherever possible and aim to route through less visible areas.
• Aim to avoid landscape features such as mature trees and woodland, historic sites such as Registered Parks and Gardens, and irreplaceable habitats such as Ancient Woodland.
• Consider views from local viewpoints, settlements (particularly Conservation Areas) and popular walking or cycling routes including the Boudicca Way. If development will be visible ensure it does not dominate and detract from the experience of visiting these locations/ travelling along these routes.
• Minimise disruption to field boundaries as far as possible – routeing through areas of historic small-scale fields will result in a greater impact than routeing through large-scale arable fields.

Overview of the development type

4.10.1 Substations transform electricity to a higher voltage to allow it to be transmitted over long distances and also transform it to a lower voltage to allow it to be distributed locally. Substations are typically required to connect generating facilities to the distribution network. The category also includes converter stations which transform one type of current to another.

4.10.2 The typical components of an electrical substation include a secure outdoor compound containing switch gear, control room buildings, and outdoor electrical equipment. There is no standard design of substations. They can be extensive in dimensions, for example, the proposed onshore substation associated with the Sheringham Shoal Extension Project includes an operational compound of up to 6ha, a building height up to 15m, and lightning masts up to 30m. Substations are assumed to be permanent development.

Potential landscape effects

4.10.3 The landscape effects of substations may include the following:

• Direct loss of landscape features in areas to be developed.
• The bulky industrial style structures can increase human influence and industrial character which may be particularly at odds in naturalistic or more remote landscapes.
• Vehicle movements, ancillary activities/storage, and flood lighting associated with these developments can also increase human influence in naturalistic or rural landscapes.
• Engineered drainage features such as SuDs features and earthworks including artificial mounds that might be used to screen the development can have an intrusive effect in the landscape.

Cumulative effects

4.10.4 Substations are typically required to connect generating facilities to the distribution network and so often found in association with other energy project types.

4.10.5 Consideration should be given to the cumulative effectives on landscape features that might arise from any new substations when they can be appreciated in close proximity to existing facilities and/or other energy infrastructure such as battery energy storage systems and pylons.

4.10.6 Existing substations in South Norfolk include Norwich Main Substation (located in Stoke Holy Cross Parish), Trowse Grid and Earlham Grid.

4.10.7 The Hornsea Three offshore windfarm project includes a new onshore substation/converter station which will connect to the Norwich Main substation. The new substation will be located to the south of the A47 and east of the B1113 and will occupy a considerable area.

4.10.8 It is proposed that a new onshore substation would be installed to the south of the existing Norwich Main substation as part of the Sheringham Shoal offshore windfarm project. The proposed substation will be up to 6ha in size. The substation will include a control building, transformers, switchgear, access roads, a lightning rod, landscape screening and drainage. The largest structure will be the control building with an approximate height of 15m. The main electrical equipment will not exceed a height of 15m.

4.10.9 The proposed Norwich to Tilbury project also includes an extension to the Norwich Main substation which would be located to the west of the existing facility.

Scenarios considered in the LSS

4.10.10 Although one scale of substation is considered in this study, it should be noted that (as set out above) the scale of substations can vary widely depending on their use or purpose.

Parameters assumed in the LSS

4.10.11 For the purposes of the LSS, the following parameters are assumed for substations:

• Built structures up to 15m tall.
• Security fencing (steel palisade up to 2.75m tall)
• No external lighting, save that for emergency attendance
• Timely implementation of a well-considered and maintained landscape scheme to integrate the development into the surrounding landscape framework.

Horlock Rules

4.10.12 National Grid's Horlock Rules provide guidance regarding the siting of substations, etc.

4.10.13 Overall System Options and Site Selection

1. In the development of system options including new substations, consideration must be given to environmental issues from the earliest stage to balance the technical benefits and capital cost requirements for new developments against the consequential environmental effects in order to keep adverse effects to a reasonably practicable minimum.

4.10.14 Amenity, Cultural or Scientific Value of Sites

2. The siting of new NGC substations, sealing end compounds and line entries should as far as reasonably practicable seek to avoid altogether internationally and nationally designated areas of the highest amenity, cultural or scientific value by the overall planning of the system connections.
3. Areas of local amenity value, important existing habitats and landscape features including ancient woodland, historic hedgerows, surface and ground water sources and nature conservation areas should be protected as far as reasonably practicable.
4. Local Context, Land Use and Site Planning 4 The siting of substations, extensions and associated proposals should take advantage of the screening provided by land form and existing features and the potential use of site layout and levels to keep intrusion into surrounding areas to a reasonably practicable minimum.
5. The proposals should keep the visual, noise and other environmental effects to a reasonably practicable minimum.
6. The land use effects of the proposal should be considered when planning the siting of substations or extensions.

4.10.15 Design

7. In the design of new substations or line entries, early consideration should be given to the options available for terminal towers, equipment, buildings and ancillary development appropriate to individual locations, seeking to keep effects to a reasonably practicable minimum.
8. Space should be used effectively to limit the area required for development consistent with appropriate mitigation measures and to minimise the adverse effects on existing land use and rights of way, whilst also having regard to future extension of the substation.
9. The design of access roads, perimeter fencing, earthshaping, planting and ancillary development should form an integral part of the site layout and design to fit in with the surroundings.

4.10.16 Line Entries

10. In open landscape especially, high voltage line entries should be kept, as far as possible, visually separate from low voltage lines and other overhead lines so as to avoid a confusing appearance.
11. The inter-relationship between towers and substation structures and background and foreground features should be studied to reduce the prominence of structures from main viewpoints. Where practicable the exposure of terminal towers on prominent ridges should be minimised by siting towers against a background of trees rather than open skylines.

Other design development guidelines

4.10.17 The following guidelines are relevant to the design of Substations in South Norfolk:

• Aim to locate new structures close to existing built form (e.g. existing electricity substation infrastructure) or in areas which are already well screened by existing vegetation.
• Ensure the scale of development is appropriate for its context.
• The materiality and colours of the proposed structures will be important in terms of their effects on the landscape. Consultation with the LPA will be required to develop the most appropriate design.
• Protect the existing network of hedgerows, woodlands, and semi-natural habitats and aim to extend these as part of any landscape scheme associated with development.
• Enhance existing screening through planting that integrates with features such as woodland and hedgerows within the wider landscape, to reinforce local character and biodiversity.
• Protect undeveloped skylines and backdrops from encroachment – set any new built development back from valley crests and avoid highly visible slopes.
• Ensure that existing landmark features remain prominent in the landscape and new development does not detract from these features.
• Avoid areas with greater time depth such as pre-18th century fields and common land.
• Avoid locating in open, undeveloped landscapes or areas with historical significance e.g. parklands. Avoid loss of areas of greater landcover interest, such as unimproved grassland or deciduous woodland.
• Avoid development which adversely affects the setting of The Broads, the openness of the Norwich Southern Bypass Landscape Protection Zone, views to Norwich or the undeveloped approaches to Norwich.
• Consider the landscape effects of drainage features such as SuDS, which can have a highly engineered form and introduce ancillary infrastructure. Ensure they have sufficient space to enable shallow sides and opportunities for habitat creation, so as to create meaningful and positive additions to the landscape.
• Ensure that any earthworks, including artificial mounds that might be used to screen the development, are sensitively designed in terms of height, profile and gradient, to fit in with the surrounding landscape. Generally, such features do not provide effective growing conditions for planting.
• Consider views from local viewpoints, settlements (particularly Conservation Areas) and popular routes (e.g. walking or cycling route). If development will be visible, ensure it does not dominate and detract from the experience of visiting these locations/ travelling along these routes.
• Consider use of green roofs.
• The local vernacular should be considered in relation to buildings.
• Ensure planting around the buildings reflects the underlying landscape character by using locally-appropriate species and linking to the existing green infrastructure network.
• Minimise the use of security lighting. Use full cut-off light fittings to avoid any direct upward light and ensure that lighting is designed to minimise light spill into the surrounding landscape. Consider use of infrared cameras to avoid the need for lighting.
• Consider providing enhanced management of landscape features, habitats and historic assets as part of any development.
• Incorporate biodiversity net gain into any new development and consider opportunities to contribute to the delivery of the Green Infrastructure network in South Norfolk.

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^[7] Guidelines for the Assessment of Indirect and Cumulative Impacts as well as Impact Interactions, European Commission, 1999 

^[8] Guidelines for Landscape and Visual Impact Assessment, Second Edition, Landscape Institute and IEMA, 2002

^[9] Intervisibility is the visibility between two points. Two points on the ground or two features are described as 'intervisible' when they are visible from each other. Intra-visibility is when two points can be seen/experienced from a third point (in many cases, this is more important that pure intervisibility); e.g. a listed building might be experienced in the same view as a new industrial building by a sensitive visual receptor.

^[10] The standard height of a straight line L4 tower is 26.1m

^[11] The standard height of a straight line L6 tower is 50.6m