We continue our 50th anniversary celebrations by looking back to pictures from 1994. These photos are of the 3m dia. sewer constructed as part of our Belfast WwTW construction which was constructed through Hunter Timber property. The tunnel was a value engineered proposal to change the scheme design from a 8m deep cut and cover pipe, which had previously proved to be slow to construct due to unforeseen ground conditions on the initial part.
The tunnel was constructed through made ground/Belfast sleech with the tunnel invert in a water bearing sand layer. As the water bearing sand layer could be problematic for the open shield, WAM installed dewatering wells to this level each side of the tunnel line at the surface, this meant that the segment of sand at the tunnel invert was dry for the miners and the face was stable.
Tunnelling was completed with a 3m dia open shield with hand dig assisted by Eimco air operated shovel to load the bogies. The tunnel proposed by WAM was a great success and had been considered by the Client’s designer but ruled it out on the basis that it would need compressed air to construct which would leak to the surface due to the tunnel crown being too shallow. WAM’s solution solved the problem by using the dewatering ahead of the drive and the miners didn’t need to work under compressed air.