Local communities have recently been consulted on Sea Link, a proposed predominantly offshore 145km cable connection between Kent and Suffolk, including onshore infrastructure cables, converter stations and substations.

The project is part of The Great Grid Upgrade, an extensive programme of upgrades to the UK’s electricity transmission network being undertaken by National Grid.

Sea Link will carry renewable and low-carbon power from offshore wind, interconnectors and nuclear power to where it’s needed in East Anglia and across the country.

The final round of consultation has now closed, and National Grid will be assessing all the feedback to continue to shape plans. However, survey work continues to progress the project through the planning stages and deliver the government’s ambition of connecting 50GW of offshore wind by 2030.

Phil Payne, marine survey manager at National Grid, is overseeing the survey work.

Prior to joining National Grid in April 2023, Phil spent 25 years in the Royal Navy, specialising as a hydrographic surveyor, before working at the UK Hydrographic Office for almost 10 years.

“I’ve been all over the world surveying both deep ocean and shallow coastal waters,” he said. “My last ship in the Navy was HMS Protector, surveying off Antarctica to help ensure the safety of the increasing number of vessels that operate in the region.”

He is part of the marine team at National Grid, who are collecting data that will help them plan where the proposed cable will be laid for Sea Link.

“We’re assessing a number of different things and have different bits of survey equipment on board to collect highly accurate data,” said Phil.

“We’re determining the general depth – that’s obviously very important and lays the foundation for all the other work,” he explained. “We’re also measuring underneath the seabed with a sub-bottom profiler to see what the sub-seabed is like for cable laying. This is important to inform the final engineering process as, ideally, the cable will be buried for protection.”

The survey team also has a magnetometer, which is used to detect metal objects and ensure the cable-laying process can go as smoothly as possible.

Braintree and Witham Times: One of the marine survey vessels used by National GridOne of the marine survey vessels used by National Grid (Image: National Grid)
“Existing infrastructure such as pipelines and other cables we should know about from our initial planning, and the magnetometer will pick up exactly where those are, but occasionally there’ll be things we don’t know about,” said Phil.

“For example, ships that have sunk in the past – there are tens of thousands of them around the UK, some of which to this day have not been recorded but may be of historical importance.

“It’s important to make sure we’re not trying to lay cables over, through or close to those sorts of objects.”

The vessel is set up for hydrographic work with the various pieces of equipment that collect the data. This includes a multibeam echosounder that uses sonar to map the seabed.

“That in itself is a very complicated piece of equipment that can collect data in swathes of about 120 degrees below the boat – collecting terabytes of data by the end of the survey,” said Phil.

“Connected to that, there’s a lot of other ancillary equipment,” he added. “There’s satellite positioning systems and an IMU, an inertial measurement unit, which position the data extremely accurately – and there is a lot of computer work going on in the background making sure that the data from all the different sensors matches up correctly.

“The survey is contracted with Shore Monitoring & Research through another company called Next Geosolutions – who we’ve worked with on previous projects – bringing in considerable expertise to ensure that the data is of the highest quality.”

Protecting marine wildlife is another important part of the survey work, Phil explained.

“We have a marine mammal observer on board who checks prior to us turning on any of our equipment that it isn’t going to harm anything.

“He’ll be using binoculars to check that there aren’t any mammals visible in the area. The vessel also has an acoustic monitoring system which drops into the water and listens out for the noises that marine mammals make to further assist in ensuring we are safe to start work.

“Most of the equipment we use has very low noise levels,” Phil added. “However, we won’t start the equipment until it is safe to do so.

“It’s vital that The Great Grid Upgrade minimises any harm to the environment, so it’s important that we leave as small a footprint as possible.”

For more information about Sea Link, please visit nationalgrid.com/electricity-transmission/network-and-infrastructure/infrastructure-projects/sealink

Braintree and Witham Times:

This article is part of LOCALiQ's Clean & Green campaign, which aims to promote our region as the biggest in the UK and Europe for all forms of renewable energy.