• 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
• additional works to support construction, including temporary construction compounds, site offices, haul roads and new road junctions (bellmouths)
• works to deliver a minimum of 10% biodiversity net gain, including planting and other environmental enhancements.

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

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

Current and upcoming works

In 2026 we will start to take down the existing 132 kV pylons and begin to build the new 400 kV pylons and underground cable. Before we can do this, we need to build a temporary haul road to reduce the impact of construction traffic on the existing road network. 

To prepare for building the haul road, our team has been carrying out vegetation clearance and building new bellmouths (road junctions) where the haul road will cross the existing road network. This work will continue at various locations through the first few months of 2026.

When working near the public highway, we may need to implement short-term traffic management measures to ensure that the work can take place safely. You can find details of current and upcoming traffic management in the table below. This programme is subject to change.

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.

Completed works

In 2025, we carried out work to build our main construction compound off the A134, between Leavenheath and Asssington. The main construction compound is being used for site offices and for the delivery and storage of materials. The compound will be removed and the site will be restored to a condition suitable for return to its original use once construction is complete. 

At the site of our new substation, we have built a new 132 kV pylon for UK Power Networks and a temporary 400 kV pylon so that further construction activity can take place. We have also started to install electrical equipment.