Beauly–Denny Overhead Line Upgrade Project

Micropile Innovation for Remote Tower Foundations

Project Background

The Beauly–Denny Overhead Line Upgrade was a major infrastructure programme designed to strengthen Scotland’s electricity network and support growing renewable energy generation. The project replaced 220km of 132kV transmission line with a new 400kV-capable route between Beauly and Denny, enabling wind, hydro and future low-carbon energy to be transmitted south.

Ahead of construction, around £60 million of enabling works delivered more than 270km of access routes, including 250 water crossings and 48 bridges. Despite this, access remained heavily constrained, with piled foundations required for over 160 of the approx 600+ new towers across steep, remote and challenging terrain. Balfour Beatty Ground Engineering (BBGE) was commissioned to deliver the piling elements - a programme that would become the largest mini-piling operation in Europe at the time.

Challenges

BBGE faced several constraints that made traditional piling methods inefficient and, in some areas, unworkable. Many tower locations were in remote areas up to 600 metres above sea level, with slopes reaching 45 degrees. Ground conditions were often too soft or steep for large piling rigs, while limited haul capacity restricted the movement of plant and materials.

The project was further challenged by harsh winter conditions, unpredictable weather and difficult access, with operatives requiring survival and 4x4 training. In some areas, communication was limited to CB radio and satellite phones.

Challenging geology, including granite, schist, psammite and quartzite, also slowed drilling progress using standard piling methods. The original foundation design specified 300mm reinforced casing, increasing installation time along with steel and concrete requirements.

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As a result, BBGE required a foundation solution that was lighter, faster to install and easier to mobilise, while still delivering the necessary structural performance.

Solution

Working closely with BBGE and Terrain Geotechnical, Ischebeck TITAN supported a full redesign of the original piling concept. Instead of large-diameter piles with reinforcement cages, the team adopted the TITAN hollow bar micropile system, enabling:

Grout encapsulation provided corrosion protection for a 120
year design life, allowing higher bar utilisation without the
need for sacrificial corrosion allowance
Reduction in pile diameter and drilling depth
Fewer piles required per tower leg
Rig access using compact, lightweight equipment
Improved positional accuracy on constrained platforms
Increased pile production - up to 50% faster installation rates
Reduced transport and material burden in inaccessible areas
An estimated 1,000 tonnes of CO2 saved

This engineering shift allowed BBGE to confidently deliver foundations for over 160 tower structures across terrain previously considered prohibitively challenging.

Testimonial

“The challenges we faced ranged from water supply and wildlife protection in the lowlands of Crieff… to drilling through granite, psammite, pelite, schist and quartzite in the Northern Highlands. Scotland is a geological paradise. I worked on the project for almost two years and I leave confident with the knowledge that wherever there is a need for a piling solution, we can get there and do it!”

Mateusz Wisniewski,

Senior Contract Engineer, Balfour Beatty Ground Engineering