Bramley - Didcot 400kV Cable Replacement Scheme

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Client | Electricity Alliance West

Division | Construction

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Between January`08 and November `09 work began on a green-field site, in an area of outstanding natural beauty, near to the picturesque village of Streatley in West Berkshire.

The works were being undertaken by the Electricity Alliance West, a partnership between National Grid, Babcock, AMEC and Mott McDonald. Prysmian Cables were contracted to supply and install the new cables and Neary Construction were appointed as the civil sub-contractor.

The original 2 x 400kV oil filled circuits were being replaced by new XLPE cables as they had reached the end of their useful life span. The detailed scope required the installation of two replacement circuits between Cable Sealing End compounds over a total distance of approximately 3.5km. It also included the refurbishment and re-construction of the two CSE Compounds.

Great care had to been taken by Neary Construction to minimise any inconvenience that may have been caused by these essential works. It was an absolute requirement to ensure that all environmental needs had been recognised. This included protection of a Roman Ridgeway; ensuring that sheep crossings were undisturbed; ensuring bridleways were created and managed efficiently; construction of badger crossings; removal (and re-planting) of trees and hedgerows prior to nesting season; care for the indigenous Roe Deer; care for the many different species of wild fowl in the area, along with actively protecting the Flora and Fauna. Additionally, there was a requirement to work very closely with the RSPB regarding the maintenance of protection for a Stone Curlew (protected species) breeding plot, along with the numerous Red Kites in the area. Finally there was also the requirement to protect a Bronze Age burial site. This was achieved by directional drilling to install ducts below area. All of this was successfully achieved by detailed planning and close liaison between the Project Management team and specialist archaeologists, environmentalists, ecologists and soil & drainage consultants.

The cable works specifically involved: constructing a secure site compound; erecting a post and wire fence either side of a 30m wide easement throughout the length of the works; topsoil stripping and stockpiling adjacent to the works; construction of a 6m wide stone/ bituminous haul road centrally located in the easement to provide access to the two cable trenches; construction of drainage ditches, lagoons and soakaways; installation of wheel-washes located at access points; excavation of close board timbered trenches between joint bay locations; cables laid and surrounded in CBS between joint bays with gatemen and security employed at all access points control access and egress.

Finally, when the installation was completed, the construction site had to be fully re-instated to match the existing surroundings in both level and soil type.

Works at Sealing End compounds involved: excavation and removal of existing structures and bases; extending the compound layout with the construction of retaining walls; installation of new palisade fencing; construction of concrete bases; erection of the new CSE structures; installation of the new earth mat and communication ducts, and finally, when the construction was completed, reinstating the area with new chippings.

The project was extremely successful and was completed within the fixed scheduled electricity outage dates.

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