TECHNICAL | DRILL & BLAST - COIRE GLAS PROJECT
of Scotland, noted Joe Coxson, Tunnel Agent with Strabag. There were other complexities to the mobilisation, owing to the site’s Loch-side plot and the single track lane running to it. These problems were overcome with an initial delivery of plant using a barge via the Caledonian Canal, and then some targeted improvements and strengthening of bridges along the Kilfinnan Road. The works on site over the first winter involved
felling of the commercial woodland for the required compounds, then preparations of all the support functions required for tunnelling; offices, welfare, batching plant, water treatment plant, explosives magazine and workshops. The work compounds themselves were completely off-grid, with no access to power, water, waste disposal, or any telecoms connection - all had to be set up from scratch to supply the tunnelling, and deal with any discharge. Another early consideration was the tunnel spoil,
which wouldn’t be leaving the site, given it wasn’t viable to transport the quantities involved along the Kilfinnan Road - not to mention this material is likely to be incorporated into future works, so it isn’t really waste at all. Instead, the most suitable area was selected to hold the material for the duration of the works, and beyond, with a design for this Spoil Storage Area undertaken by Arup. Work on the Adit itself started in March 2023, with
Above: Adit portal construction
PHOTO CREDIT: JOE COXSON
Below: Underground GI core logging PHOTO CREDIT: TOM ROBINSON
was for the worst of conditions, anticipated within the Great Glen Fault Zone, and would employ H-Beams, spiles, face bolts, and a closed invert. The designs also included the construction of wider passing bays and turning niches, to facilitate construction, and the drilling gallery at the Adit’s inbye end. Strabag got access to the site in December 2022, not exactly earth works season in the Highlands
the first blast of what would eventually be slightly more than 500 advances on the project. A pre-split successfully created a clean rock face for the portal, with soil nails supporting the slope above, then rock dowels and netting below. Credit is due to RJ McLeod and Albion Drilling, whose local workforce were indispensable during this stage of the mobilisation. The tunnelling crew’s first activity was creating a
false portal at the tunnel eye, consisting of a lattice girder and a sprayed concrete arch. This allowed a full test of the tunnelling systems before excavation commenced, and valuable familiarisation with the equipment itself. The traditional blessing of our Santa Barbara was held in mid-May, thanks to Father Danny from the local parish, and tunnelling got underway. Joe continued with an overview of the Adit’s long
section, with an initially steep decline of 7%, then a shallower 4% after the first hundred metres. Passing bays were planned roughly every 250m, each with a turning niche. The majority of the Adit was on a slight right-hand curve, towards the planned underground powerhouse location. The full drill and blast cycle was explained, with
an overview of the equipment used, and engineering tools at the team’s disposal, such as Epiroc’s Underground Manager software, for creating and implementing drill plans, and Amberg Tunnel software for checking profiles and recording as-builts. An interesting feature of the Exploratory Works was
the effort devoted to face mapping. Two engineering geologists had a full hour to map, if required (which would have enraged most over-eager Pit Bosses) as,
12 | February 2026
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