- The tunnel took four years to build using power drills and chisels.
- It can carry up to 90 million gallons of water per day to the Silent Valley.
- It was built by Messrs. A.M Charmichael, Edinburgh.
- Two groups worked on the tunnel, each starting at the opposite side of the mountain.
- They met in the middle, only 5cm apart.
- At the tunnel mouth, near the head of the Valley an electric pump ran to keep the works from being flooded.
Construction of the Silent Valley, Stage 3
1949-1958 Stage 3 was to build a 4k tunnel through the Slieve Bignian Mountain to divert water from the Annalong River to the Silent Valley. Ben Crom Reservoir was going to be built futher upstream of the Silent Valley. Working on the tunnel. Slieve Bignian Tunnel