Underground cables between Nailsea and Portishead

Work between Nailsea and Portishead

In January 2020, we started work on the construction of underground cables between the west end of Nailsea and Portishead substation.

The construction of the underground cables involves several different types of engineering activity and includes building temporary entrances and access roads, excavating trenches for cable ducts and joint bays, and installation and connection of the cables. We’ve appointed J. Murphy & Sons Limited, as the contractor for this stage of the project and we expect it to be completed by autumn 2021.

Once the cables are in place and operational, we’ll take down two lines of pylons owned by Western Power Distribution (WPD) that run close to and over homes in Nailsea. We are removing these existing pylons as a direct result of community feedback.

From May 2020, we’re building a new overhead line between Bridgwater and Seabank substations – mainly using T-pylons. We will start south of the Mendips first, and start work on the route between the west of Nailsea and Portishead later in the programme.

To view the map showing the work between Nailsea and Portishead, please click here.

Programme of work between Nailsea and Portishead 

The outline programme for the work between Nailsea and Portishead substation is below.

On the 7 January 2020, we started work on Engine Lane and Hanham Way towards Watery Lane in the west end of Nailsea to build temporary entrances to our construction areas. In early February 2020, we started to construct temporary entrances in other areas along the route.

We are working with our contractors to develop the detailed timings for installing the underground cables and will publish more information when it is available.

We recognise that our construction activity impacts local communities. We are working hard to limit that as much as possible. Details of all current construction activity can be found here.

Access and traffic management

We agreed a construction traffic management plan with the local authorities which sets out the roads our vehicles can use for construction work. We’re building temporary traffic access points and haul roads along the route of the cable that will allow us to move traffic off main roads directly into the construction areas.

To view the map showing the temporary accesses and haul roads, please click here.

When installing the accesses, haul roads and underground cables, we’ll need to manage traffic by temporarily closing some roads and controlling access at different times along parts of the cable route.

We will agree and coordinate all road closures and traffic management with the local highway authority. These will include:

  • Temporary traffic lights
  • Short term road closures (with diversions)
  • Restricted parking/suspensions.

Our contractors will put up advance notice signs to let local road users know of any traffic restrictions and road closures. Updates can be found here.

Construction compounds

We will need to build temporary construction compounds along the underground cable route. They will include offices with parking and welfare facilities as well as areas for receiving and storing equipment and materials during construction.

We will monitor the compounds using on-site security.

To view the map showing the construction compounds, please click here.

We will remove the temporary compounds off Engine Lane and Church Lane and reinstate the land when the underground cables are installed and operational.

Other temporary compounds will be used when we take down the existing pylons and build the T-pylons. We will remove them when all our work in this area is complete.

Underground cable construction

In spring 2020, we started constructing and installing the cables through the streets in the west end of Nailsea.

The underground cables will be installed on land adjacent to Engine Lane before emerging on to Engine Lane where it connects with Blackfriars Road, progressing along Blackfrairs Road, turning down to Hannah More Road and on to Queens Road to cross the four-way junction between Queens Road/North Road and Hanham Way, down along Hanham Way, where the cable route will then cross to Watery Lane and continue behind Causeway View in the direction towards Tickenham.

To view the map showing the underground cable route, please click here.

We are installing six underground cables typically in two trenches – three cables per trench.

The trenches will be dug in short sections using excavators and specialist equipment. These trenches are approximately 1–3m wide and 1.5m deep.

Our engineers have modified the design so we can lay the cables in a single trench through the streets of the west end of Nailsea, approximately 2m wide.

We will install ducts which will enable us to close each section of the trench promptly. This will help to limit local disruption on the highways and is safer than leaving trenches open for long periods of time. This technique also helps to protect the soil structure of the land, minimise impacts on wildlife and the environment.

When the ducts are in place along the length of the cable route, we will start to install the high voltage cables in sections of approximately 900m. We will join the sections together in joint bays. There will be 11 joint bays along the route.

After the cables are installed and jointed together, we will test them and make them operational.

Public footpaths

Where the cable route and the haul road cross public footpaths, we need to keep the area safe for the public and for our staff while we are working.

There will be temporary footpath closures with diversions for pedestrians at different times throughout the construction programme. Updates can be found here.

Enhancing habitats

Working with Natural England and the local landowner, we’ve designed and installed a tilting weir near the Causeway, between Nailsea and Tickenham.

It acts as a tilting gate for retaining and raising water levels in this area of marshy wetlands – creating a more reliable feeding and breeding ground, encouraging wading birds and new species of wildlife with a long-term environment for them to stay.

Working hours

Our agreed standard working hours are between 7am and 7pm Monday to Friday and 8am to 5pm on weekends.

Most work will be carried out on weekdays, although there may be occasions when we’ll need to work at weekends or outside the standard hours. These may include when we are working on a continuous process such as cable jointing, or if adverse weather or ground conditions cause delays, or to avoid traffic delays during the week, but there are restrictions to this.

What’s next

We are working with our contractors to develop the detailed timings for installing the underground cables along the route and will publish more information soon.

We recognise the impact of construction on the community and welcome opportunities to talk with residents and businesses about the project before construction begins in each area. Details of public events can be found here.

We value and welcome your interest in the project, please contact us.

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