A LARGE gas distribution company recently found it necessary to extend the length of a tunnel which housed one of its 30-inch cast iron mains. The tunnel had been built under a river near the turn of the century and was constructed of masonry. During the course of years following construction of the tunnel, the roof of the drift was damaged by an anchored vessel and severe water leakage into the tunnel resulted. In order to overcome the leakage, the drift was closed with concrete, which in turn cut off the accessibility of the main to inspection and maintenance.
Because the old main was inaccessible, it was concluded that during reconstruction a welded steel main should be installed inside the 30-inch cast iron pipe through the drift.
At the beginning of the reconstruction work, the cast iron main was taken out of, service and an internal survey of the main’s...
