Sydney Harbour railway electricity tunnel

The tunnel construction job itself was a series of "Homeric battles": The work was started from three points; Long Nose Point, Greenwich, and a shaft at the extreme end of Mann Point, which is a continuation, more or less, of Greenwich. Initially progress was rapid, however some problems were encountered. First of all, the residents of Long Nose Point, in letters and protests very much to the point, caused the abandonment of work from the Long Nose end after a considerable distance had been excavated. Work, therefore, progressed slowly on from the north side until about May 1915, when a large fissure in the rock was found in the approximate middle of the Parramatta River. The only solution was to seal up the tunnel and patch the fissure. A bulkhead was built into the tunnel to stop the progress of the sand, water and silt and a staging was built in the middle of the river and drills were bored through the riverbed. Pipes were inserted through the holes and a cement mixture was gradually pumped into the tunnel in the vicinity of the fissure.[3]

The cement pumping operation was repeated through three other pipes in line with the original ones and the tunnel was sealed twice and allowed to set. The door was then re-opened and the silt and sand removed. A second sealing showed signs of weakness so it was decided to abandon the top tunnel and go deeper into the rock. A permanent bulkhead was built into the rock and the tunnel was sealed up with approximately 5 metres (15 ft) of concrete that remains today.[3]

A second tunnel was commenced 15 metres (50 ft) below the first one. The down grade was increased to 1 in 1.3. The work was carried out with explosives and some progress was made, however; on arrival at the point immediately below the original break-in, another crevice was struck and water rushed in. On this occasion, the engineer in chief, R. L. Rankin and the resident engineer W. R. H. Melville, decided to go with the foreman and have a look at the fissure that had flooded the tunnel. Placing candles on pieces of wood, they swam approximately 12 metres (40 ft) into the centre of the tunnel. It was a risky job. The surface of the water was less than a yard from the top of the tunnel and if the inflow had suddenly increased, they would have been caught. The break-in was later sealed by placing fifteen-centimetre (six-inch) pipes, approximately 14 metres (15 yd) long, into the crevice, and the whole of the tunnel in the immediate vicinity was packed with bags of clay and tightly rammed. In front of this was placed a steel bulkhead with a steel door and through the bulkhead eight-centimetre (three-inch) pipes were laid right into the crevice, to allow the water to get out. Through the fifteen-centimetre (six-inch) pipes cement was pumped until finally it was not possible to shoot any more into the crevice under very heavy pressure. This was allowed to set for approximately three months. When the bulkhead door was opened it was found that the inflow had practically stopped. The bags of clay were completely cemented together and a detour was cut at this point to approximately 2 metres (6 ft), to get round the crevice, and when the men had passed it they worked back to the original line of excavation.[3]

The section of the tunnel that had been sealed up was cut through, the detour filled in, and the original straight line of excavation restored. After going about 15 metres (50 ft) past the crevice, they struck another small fissure, which was apparently a section of the original one, and water suddenly flowed in at the rate of about 11,000 litres (2,400 imp gal) an hour. This was not sufficient to stop the progress of the work, but pumps were installed to cope with the inflow.[3]

Soon after the men began to work on the up-grade, and here great care had to be exercised to prevent the material falling back on them. The material was cut out by channelling machines, which allowed it to be removed without difficulty. Eventually the work broke through and the opening at the Long Nose Point side was in sight. Their calculations had been made with remarkable accuracy. The centre line, when the tunnel was connected, was only 1/8th of an inch out, while the levels were absolutely correct.[3]

Despite careful lining leaks kept occurring. The tunnel was flooded about 1930, whether intentionally to avoid continual pumping or as the result of a sudden inrush of water, is not clear. In 1952 the Electricity Commission of New South Wales was formed to take over the generation of all electric power in NSW. The power stations in White Bay and Ultimo were taken over, but the tunnel and its cables remained the property of the State Rail Authority. During the construction of the Sydney Harbour Bridge the railway communication cables were re-routed via the Bridge. The electricity cables in the flooded tunnel were completed sheathed and remained in use until 1969, but are no longer used due to ample supplies of electricity now available on the north side of the harbour from electricity substations.[3]

• This Wikipedia article was originally based on Railway electricity tunnel under Sydney Harbour, entry number 01231 in the New South Wales State Heritage Register published by the State of New South Wales (Department of Planning and Environment) 2018 under CC-BY 4.0 licence, accessed on 2 June 2018.
• This Wikipedia article was originally based on Sydney Harbour (Balmain to Greenwich) Railway Electricity Tunnel, entry number 5062542 in the New South Wales Heritage Database published by the State of New South Wales and Office of Environment and Heritage 2018 under CC-BY 4.0 licence, accessed on 30 September 2018.
• This Wikipedia article was originally based on Sydney Harbour Tunnel - Greenwich to Balmain, entry number 1940571 in the New South Wales Heritage Database published by the State of New South Wales and Office of Environment and Heritage 2018 under CC-BY 4.0 licence, accessed on 30 September 2018.