Whitson 400kV Substation

Newport, South Wales

Replacement of an ageing foul drainage system and the provision of a flood defence solution to ensure the substation could continue its operations

As part of a two year framework contract with National Grid covering South Wales and the South West, Stepnell were awarded a contract at Whitson substation near Newport in South Wales.

The old foul drainage system was served by an effluent tank which needed emptying regularly. This was replaced by new drainage runs leading to a Biodigester sewage plant. The original design required the 3.5 metre deep Biodigester to be installed directly under HV overhead conductors in a sheeted excavation carried out in water bearing soft peat and made ground. Stepnell proposed redesigning the drainage runs to move the excavation away from the overhead conductors and sinking a concrete caisson to contain the Biodigester and avoid the need for temporary sheeting. This was accepted and enabled the works to be carried out without any power outages.

An area of the site containing Quad Booster Kiosks was also prone to flooding so Stepnell constructed new reinforced concrete around the existing live works to provide future protection against floods.

As part of this project new reinforced parking areas and footpaths were also constructed.

  • Client:

    National Grid plc

  • Programme:

    12 weeks

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