The tunnel's construction proved difficult on account of multiple factors technical, geological, and financial. The copious supply of water, which was necessary in order to power any heavy equipment at the time, was unreliable; the Tremola spring was one source, but would greatly change in capacity seasonally, leading to water being extracted from the more distant river Ticino instead. At the suggestion of the Geneva-based engineer M. Colladon, it was decided to use compressed air as a means of conveying energy around the worksite and along the bores. Air was compressed by water-driven pumps and stored in cooled reservoirs prior to use; as the air pipes traversed greater and greater distances, the diameter of the pipes used was increased in order to maintain pressure. To reduce the heat of the rock during drilling, water jets were routinely used to cool the rockface.