• building approximately 18 km of new 400 kV overhead line
• building approximately 11 km of new 400 kV underground cable
• removing around 27 km of existing 132 kV and 400kV overhead line between Burstall Bridge and Twinstead Tee
• ancillary works to support construction of the project, such as temporary construction compounds, site offices and haul roads
• works to deliver a minimum of 10% biodiversity net gain, including planting and other environmental enhancements.

We are also building a new grid supply point (GSP) substation at Twinstead Green (between Butler's Wood and Walegrave Wood). The GSP substation is where National Grid's high voltage transmission network connects into the low voltage network run by UK Power Networks, who are the distribution network operator in this area. We applied to build the GSP substation through a separate planning application to Braintree District Council.

You can view the detailed plans included in our application for development consent by visiting the Planning Inspectorate's website here.

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Current works

Construction is now underway at the main construction compound in Leavenheath/Assington. This will mean that there will be an increased number of deliveries to the site, including the delivery of stone and welfare units. Traffic management measures will be in place over the coming weeks in order for construction to take place safely.

The main construction compound will be used throughout the construction phase for site offices and the delivery and storage of materials. Once construction of the project is complete, the compound will be removed and the site restored to a condition suitable for return to its original use.

Current works, which are being carried out by Balfour Beatty on behalf of National Grid, include:

• creation of a bellmouth (road junction) to allow safe access to and from the site, along with associated signage
• removal of topsoil and delivery of stone, which will form the surface of the compound
• delivery and fit-out of modular site office and worker facilities, including drainage and ducting.

At the peak of works, we expect up to 60 vehicle movements per day to and from the compound site. Our approved working hours are 7am-7pm (Mon-Fri) and 8am-5pm (Sat, Sun and bank holidays), but we do not expect this phase of work to take place at the weekend or on bank holidays. 

We will look to minimise disruption wherever possible and are sorry for any inconvenience caused whilst the works are carried out. Should any work be delayed or take longer than planned due to factors outside our control such as adverse weather, updates will be shared here on our website. Thank you for your patience while the works take place.

Grid supply point substation

In the coming months, work at the GSP substation site will continue with the following activities:

• commissioning of the LVAC site supplies
• continued construction of the Control Rooms and associated buildings
• ongoing civil and mechanical & electrical works, including the installation of cable ducts, draw pits, and both above- and below-ground earthing systems.

Surveys

If a survey cannot take place on the scheduled date (due to factors such as poor weather conditions), we will endeavour to reschedule the survey in a timely manner.

Access to land plots is agreed before any surveys take place. If you are a landowner and have questions about surveys on your land, please get in touch via your usual point of contact or the details at the bottom of the page.

Upcoming works

We expect to start construction work on the rest of the project later in 2025. This is likely to include:

• creating temporary construction roads and accesses to reduce construction traffic on the local road network
• delivery of a second supergrid transformer to the grid supply point substation site
• the start of a temporary outage on the existing 132 kV overhead line
• continuation of pre-construction environmental and archaeological surveys. 

Completed works

GSP substation

Over the past few months, significant progress has been made at the GSP substation site, including:

• a new 132 kV pylon has been constructed for UK Power Networks, with the circuit successfully transferred under outage conditions and the original tower removed
• a temporary 400 kV pylon has been installed, and the associated circuit has also been transferred under outage conditions
• civil works within the main GSP compound have advanced, including the installation of cable troughs
• steel structures and associated equipment, such as switchgear, have been installed
• the permanent perimeter fence is now 90% complete
• low voltage auxiliary control site supplies have been installed.