Although the section from Banavie to the head of Loch Eil was easy, from there onwards the terrain was very difficult, a problem exacerbated by the remoteness and difficult access. Very hard rock was encountered and away from Loch Eil there was a considerable volume to penetrate. Steam-powered drilling equipment was difficult to bring to the locations and keep fuelled, and McAlpine used water turbines to provide compressed air power for drilling. The construction of the line actually cost £540,000 ().