Tunnel boring work is due to begin shortly on the largest scheme of its kind in Wales – the Snowdonia VIP (Visual Impact Provision) project – featuring construction aggregates from Welsh Slate and parent company Breedon.
The massive TBM (Tunnel Boring Machine), affectionately nicknamed Buddug, will bore the 3k-long tunnel through Eryri National Park and under the Dwyryd Estuary from Minffordd to Llandecwyn to take the electricity supply underground in a bid to negate its visual impact.
Aggregates from Welsh Slate’s Ffestiniog Quarry and Breedon’s Minffordd Quarry, both in North Wales, are being used by Jennings Building and Civil Engineering who have completed groundworks on three separate sites over the past two years.
The sites are Garth at Minffordd (the main compound and offices for principal contractor Hochtief UK, and the entrance of the tunnel), Cilfor at Llandecwyn (the tunnel exit which required a floating road for access) and Blaen Cefn at Minffordd (a new-build workers accommodation site of 100 bunk cabins).
At the Garth site, Jennings imported 90,000+ tonnes of 6F5 capping aggregate and 5,000+ tonnes of MOT Type 1 sub-base to build up a site foundation that was above the estuary water level.
Jennings’ buyer Jason Hubball said: “Breedon’s Minffordd and Ffestiniog quarries are ideally located to service this project and this was beneficial for both our and Hochtief UK’s company targets of achieving low-carbon emissions through transport.
“Breedon consistently delivered daily large volumes of aggregate without any issues, and we collected with ease when using our own transport. In addition to the large volume of aggregate required for this site, we sub-contracted Breedon’s surfacing business for the asphalt surfacing requirements for the compound road and car parks. Breedon completed this work on time and to a very high standard, and our client was very happy with the result.”
The Cilfor site required the construction of a floating road as an access to the tunnel exit location and for this Jennings imported 16,000+ tonnes of 6C aggregate from Welsh Slate’s Ffestiniog quarry and 12,000+ tonnes of MOT Type 1 from Minffordd.
Jason said: “The 6C aggregate is a well graded aggregate ideal for large free-flowing drainage applications. The combination of this stone with a high-strength textile made up the floating road construction, enabling water to pass through.”
In addition to the road construction, Jennings installed 145 gabion baskets around the perimeter of the working platform and used Breedon’s 6G aggregate (100/200mm grading) as the stone infill.
“The service from Breedon from both quarries for this site was superb and this project was completed without any issues,” said Jason.
Jennings’ project at Blaen Cefn was a groundworks package to enable the placement of 100 temporary accommodation pods for staff working on the SVIP project. As well as the general site groundworks, this involved building a cell-pave road to access the site.
All aggregate was procured from the nearby Minffordd quarry – 1,500+ tonnes of 6F5 capping, 5,000+ tonnes of MOT Type 1 sub-base for the foundations, and 1,000+ tonnes of single-sized 6.3/14mm hardstone for the cell-pave infill.
Jason said: “Jennings have always had a good historic relationship with Breedon who are one of our biggest suppliers of aggregate, ready-mix concrete and asphalt materials for our sites across North Wales and north-west England. Breedon always supply high-quality material from their quarries and batching plants, ensuring that our groundwork foundations are of the high standard that we adhere to.
“Breedon’s territory sales manager, John Roberts, has provided an excellent level of customer service. His close liaison with Jennings ensures that all of our aggregate requirements are met with no disruption to programme. Because of their material quality and exceptional service, Breedon is a highly regarded aggregate supplier of Jennings.”
The TBM has been delivered from Germany in 27 packages and once fully assembled, measures 166m in length and weighs 436 tonnes. It is expected to reach Llandecwyn by mid-2026. The subsequent removal of pylons and 400kV overhead lines is scheduled to occur by 2029.
The Eryri project forms part of a broader initiative by National Grid to reduce the visual impact of electricity infrastructure in protected landscapes across the UK. Additional projects are underway in England’s Cotswolds and the North Wessex Downs.
