Map-pin

Our proposals

We have broken the route down into various sections, which are shown on the map and below. Each section gives more detail about the project specifics and the rationale behind the proposals.

Section AB - Bramford to Hintlesham

Our proposals

We would build a new overhead line from Bramford substation to the south of the existing 400 kV line.

We would build a new section of overhead line to the north of Ramsey Wood and divert the existing 400 kV line onto these pylons. The new reinforcement would then be able to use the existing pylons through Hintlesham Wood. This approach was favoured over other alignment options due to the effects on landscape, visual and heritage. It would also allow for the greater paralleling of new and existing line and avoid impacting Hintlesham Wood.

We would remove the existing 132 kV overhead line from Burstall Bridge running to the south west of Hintlesham.

Considerations

This area of the route includes the Grade I listed Hintlesham Hall, the ancient woodland in Hintlesham Little and Great Woods and Ramsey Wood, which are also designated as Sites of Special Scientific Interest (SSSI).

We will continue to consult with Historic England to ensure our proposals strike the right balance between delivering the critical network reinforcement, whilst being mindful of the surrounding environmental, heritage and community context.

Further information on how our proposals have evolved in this area can be found in the Project Development Options Report.

As the project develops, we will be consulting extensively with stakeholders such as Historic England to ensure our proposals strike the right balance between delivering the critical network reinforcement, whilst being mindful of the surrounding environmental, heritage and community context.

Section C - Brett Valley

Our proposals

We would build a new overhead line in this section.

The alignment would pass to the south of Kate’s Hill and follow the alignment of the existing 132 kV overhead line. The line would deviate directly to the south of Pipkin Lodge to the east of Benton Street. The pylons would be screened by trees in views from Benton Street, approaching from the Layham direction.

We would remove the existing 132 kV overhead line.

Section D - Polstead

Our Proposals

We would build a new overhead line in this section.

The alignment would run to the south of the existing 400 kV power line, roughly following the alignment of the existing 132 kV overhead line.

When approaching the Dedham Vale AONB the proposed line would deviate slightly south west and connect into a CSE compound near Dollops Wood.

We would remove the existing 132 kV overhead line.

Section E - Dedham Vale AONB

Our proposals

We would build approximately 4 km underground cables through the Dedham Vale AONB.

At each end of the underground cables section, we would need to build a CSE compound.

In this section we are proposing to build the eastern CSE compound to the south east of Sprotts Farm, east of the boundary of the AONB. This location was identified as it provided an opportunity to screen the compound next to the adjacent Dollops Wood. We would increase screening through additional planting and landscaping.

We are proposing to build the western CSE compound to the immediate west of Boxford Fruit Farm. This location was identified as it offered separation from the AONB to the east and would be next to existing tree planting along the boundary of the orchard, providing further natural screening. This location would also allow the terminal pylon required to transition the line back to overhead to be aligned more closely with the existing 400 kV overhead line.

We would remove the existing 132 kV overhead line.

Considerations

When Dollops Woold was selected as the preferred location for the eastern CSE, consideration was given to using a method called horizontal directional drilling to install underground cables under Dollops Wood.  Using directional drilling would avoid digging open trenches and tree clearance to lay the cables, thereby reducing any potential impact on the woodland. Once clear of the woodland, we would install the cables in trenches.

The feasibility of using directional drilling beneath the woodland is being investigated. It is potentially very challenging given the variation in topography.

We are therefore considering an alternative route for the underground cables this area.

The alternative underground cable route would travel northwards past Sprotts Farm and back down in a south westerly direction between Broom Hill Wood and Bushy Park Wood, as shown on the map.

Cable Sealing Ends

To transfer power from overhead lines to underground cables, a Cable Sealing End compound is needed. Two Cable Sealing End compounds are needed for this section of the route, in the east and west.

In the east we are proposing to place the Cable Sealing End compound to the south east of Sprott’s Farm, east of the boundary of the AONB. This location was identified as it provided an opportunity to screen the compound next to the adjacent Dollops Wood. Further screening would also be added through additional planting and landscape boundary treatments.

In the west, the Cable Sealing End compound is proposed to be located to the immediate west of Boxford Fruit Farm. This location has been identified as the most appropriate out of a total of four initial options, as it offers separation from the AONB to the east and could be placed next to existing tree planting along the boundary of the orchard, providing further natural screening.

This location would also allow the terminal pylon required to transition the line back to overhead to be aligned more closely with the existing 400 kV overhead line.

Section F - Leavenheath and Assington

We would build a new overhead line in this section.

The alignment would continue through Leavenheath to the south of the existing 400 kV line, south of Assington and Sudbury before crossing the B1508 and the railway.

We would remove the existing 132 kV overhead line.

Section G - Stour Valley

Our proposals

We would build a new overhead line roughly parallel to the existing 400 kV overhead line from the east of the area until just south of Sawyers Farm, where it would connect into a CSE compound.

West of Sawyers Farm we would build approximately 3.8 km of underground cables through the Stour Valley.

At each end of the underground cables section we would need to build a CSE compound.

We are proposing to build the eastern CSE compound to the south of Sawyers Farm. This location was identified as it benefited from existing vegetation on site, which would provide natural screening and minimise the visual impact to the surrounding landscape.

The location for the western CSE was subject to extensive consultation before our preferred site was confirmed as south west of Ansells Farm. This location would benefit from existing mature screening and would be located further away from Alphamstone Complex Local Wildlife Site.

This location also means that the underground cable would be routed further south and we would be able to remove approximately 1km of the existing 400 kV line between here and Twinstead Tee.

We would remove the existing 132 kV line overhead line up to the ‘diamond crossing’ to the south west of Sparrows Farm.

Considerations

Although recognised as a landscape of value and with links to famous artists, the Stour Valley (Section G) is not formally designated as an Area of Outstanding Natural Beauty and the review has identified this area as requiring further work to understand whether the additional cost of an underground cables (£118m) in this location is justified. We are therefore seeking views from stakeholders and consumers as to whether the previous decision to underground this section still provides value for money.

In particular, National Grid would like to understand views on:

  • The landscape and cultural value of the Stour Valley;
  • Progress on proposals to extend the Dedham Vale AONB boundary in the Stour Valley towards Sudbury;
  • The construction effects of undergrounding in the Stour Valley (on ecology, archaeology and traffic); and
  • Anything else National Grid should consider.

Cable Sealing Ends

There are two Cable Sealing End compounds identified in this section of the route to facilitate the transition of the underground cables through the Stour Valley.

Eastern Cable Sealing End Compound

The Cable Sealing End compound to the east is located to the south of Sawyers Farm due to the natural depression in the land on the edge of the Stour Valley. This location benefits from existing vegetation, providing natural screening and minimising the visual impact to the surrounding landscape.

Western Cable Sealing End Compound

The proposals for the western Cable Sealing End compound were subject to extensive consultation between 2009 and 2013. More information on how the project developed in this location can be found in the Project Background Options Report.

To summarise, the Western Cable Sealing End Compound was originally proposed in a different location, adjacent to the existing Bramford-Braintree-Rayleigh overhead line. This location was identified as it lay within a natural valley with an existing mature hedgerow and woodland, which would serve to naturally screen the compound. Despite qualities for natural screening, this location would sit closer to the Grade II listed buildings at Sparrow’s Farm and it was considered that it could impact views from the public right of way.

Following further engagement with stakeholders, a further two alternative locations 1.5 km further south were assessed. Information on these locations can be found in more detail in the Western Cable Sealing End Compound study, published in November 2012.

The study recommended the location we are presenting, south west of Ansells Farm, as it would result in fewer hedgerow and protected lane crossings and would benefit from existing mature screening. It would also be located further away from Alphamstone Complex Local Wildlife Site.

This location also means that the underground cable will be routed further south enabling a section of the existing 400 kV line to the north can be removed.

Substation

Grid supply substation

Our proposals include taking down the existing 132 kV power line operated by UK Power Networks (UKPN) between Burstall Bridge and the ‘diamond crossing’ near Twinstead. Removing the line would make way for our new 400 kV reinforcement and help reduce its visual impact in the landscape.

The existing 132 kV line is part of the local distribution network and to take it down, we would need to carry out additional work to maintain local electricity supplies.

UKPN looked at a number of options to maintain the security of local electricity supplies and we carried out additional analysis of the options. In February 2013 we confirmed that building a new grid supply substation west of Twinstead would represent the best way forward from a lifetime cost, environmental and socio-economic perspective.

The substation would contain transformers to change the level of voltage from the 400 kV network (owned and operated by National Grid) to the 132 kV needed to be distributed to the rest of UK Power Network’s local network. The substation will also enclose protection isolation, cooling fans a diesel generator, water tank and switching devices.

We identified a number of potential locations for the new substation and, following public consultation, we confirmed our preferred site as near Butler’s Wood, just off the A131 south of Sudbury. This location would offer screening and direct access from the main road network.

The Distribution System Options Report confirmed that the substation approach represented the best way forward from a lifetime cost, environmental and socio-economic perspective, following this we looked further at potential sites. The Substation Options Appraisal (2013) looked at several study areas for the new substation and concluded that a substation between Butlers Wood and Waldegrave Wood was preferred due to the amount of natural screening, the accessibility of the site for long-term maintenance and due to its size still being undetermined.

Considerations

We have undertaken further discussions with UKPN and they may now require two transformers at the substation site.

That would require a larger footprint than originally assumed. We carried our further assessment during 2020 to identify whether the larger footprint could be accommodated here. Our assessments have shown that the site could accommodate two transformers if required within the existing woodland screening. We therefore continue to consider this our preferred location for the substation.