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Cumnock SWS power line upgrade haul road installation

Cumnock SWS Power Line Upgrade

  • South West Scotland Connections

  • Cumnock, Ayrshire

  • 475,000m2 MultiTrack

  • 440,000m2 SX Grid

The Scottish Government has set a major target to generate Scotland’s electricity from renewable energy. As the existing network does not have sufficient capacity to cope with the level of demand, a new transmission network was required.

The South West Scotland Connections Project will enable new sources of renewable energy to connect into the transmission systems and will play a key role in helping Scotland meet its renewable energy goals.

AMEC had secured the contract to build over 47km of 132kV new double circuit overhead power lines including around 250 pylons. Having worked together previously, they contacted Wrekin to assist with designing the temporary stone access roads required to enable the power lines to be constructed.

Prior to choosing a solution, Wrekin supplied AMEC with products to construct a short stretch of trial road using a woven geotextile at the base with integral geogrids further up the construction.

Cumnock haul road installation
Cumnock haul road installation using MultiTrack and SX Grid

However, the trial didn’t perform as hoped with the woven geotextile not developing the interlock that would be achieved by a geogrid.

It was therefore decided to use a MultiTrack NW9 non-woven geotextile as a separator/filter on the sub-grade with layers of ‘punched and drawn’ SX Grid 3030 geogrid above to provide the reinforcement and stabilisation for the road.

Following training, AMEC’s temporary works design team became competent in using Wrekin’s ‘Sub Save’ calculation software to calculate the required road cross sections. The software calculated the stone depth and number of layers of geogrid required and also the saving in stone that the geogrid provided – typically between 35-45% against an unreinforced solution. The road cross sections varied due to the varying ground conditions across the challenging and remote terrain, but also the varying volume and type of construction traffic that would be using each section of road.

With a required road width of 4m, and taking the roads shoulders into consideration, standard width rolls required 2 roll widths of each product to achieve full coverage at sub-grade level. This would result in a much slower construction rate and potentially a large amount of product waste. Wrekin removed this potential for waste, and delivered further savings in cost and time to AMEC by supplying the geotextile and geogrid as wide rolls in excess of 5m width.

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