|10- Electricity and Gas Tunnels|
|TUNNEL UNDER THE HARBOUR
The only tunnel connecting the two sides of Sydney Harbour is now flooded and virtually forgotten. It was built between Long Nose Point, Balmain, and Manns Point, Greenwich, from 1913 to 1924 to carry submarine electricity cables for the electric tramway system on the north side of the Harbour. Submarine cables laid across the harbour earlier had suffered damage from ships dragging their anchors.
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 from the records. The cables in the flooded tunnel remained in use until 1969, but are no longer used because ample supplies of electricity are available on the north side of the harbour from Electricity Commission substations. The tunnel may one day be pumped out to recover the valuable copper in the cables.
When it was built, the tunnel was one of Australia's major engineering feats. Here is how a reporter from, the Sun described his journey under the harbour in 1924:
There is not much outward evidence of this great work. At the Long Nose Point there is the usual pit-head working and-the mouth of the tunnel. At the Greenwich side there are two openings. A shaft nearer the water, which descends directly down into the bowels of the earth, and further up the hill, another opening where the slope downward commences.
The atmosphere was cool and pleasant, electric light bulbs twinkled like golden glow worms, and here and there the water trickled slowly in from the roof and sides; in one or two places outlet pipes discharged a flow of percolated water into the bed of the tunnel. A little light railway ran right through, at odd spots few men worked putting the finishing touches to a job which they talk of with pride. Running the length on one side were cement racks to hold the high tension wires which will supply electric power for trams and trains on the north side of the harbour. At one end was a pool some six feet in depth, where the soakage collects, and is pumped to the surface. ...
The tunnel is perfectly straight, except at Greenwich Point, where it takes a bend to allow an outlet at a suitable spot. From outlet to outlet it measures 1,760 feet. At each shaft it descends steeply into the ground at a grade of 2 in 1, except in a section at the Greenwich end; where a steep cut had to he made to avoid trouble. Here the grade is 1 in 1.3.
On the level of the tunnel it is possible to walk upright with ease. In fact, two or three men could walk abreast, and there is ample room for any working party to repair the cables.
The construction job itself was, according to the Sun reporter, a series of "Homeric battles":
At the commencement of the work, the necessary compressor was located on the south 91to supply power for the pneumatic drills. 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. Progress was rapid for a while -about 25 yards per month at every point. But then came problems. First of all, the residents of Long Nose Point, in letters and protests very much to the point, caused the
abandonment of the Long Nose end after a considerable distance had been excavated. Work, therefore, went slowly on from the north side until about May, 1915, when a big fissure in the rock about the middle of the Parramatta River was met. 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. With great accuracy these entered the tunnel almost in the centre. Then pipes were entered through the holes, and a cement mixture was gradually pumped into the tunnel about the vicinity of the fissure.
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. It was then found that the second sealing showed signs of weakness, and it was thought advisable 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 about 15 feet of concrete, and it remains like that today.
Then a second tunnel was commenced 50 feet below the first one. The down grade was increased to 1 in 1.3. The work was still being carried out with explosives, and progress was fairly fast; but 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 about 40 feet 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. If the inflow had suddenly increased, they would have been caught like rats in a trap.
The break-in was later sealed by placing 6-inch pipes, about 15 yards long, into the crevice, and the whole of the tunnel in the immediate vicinity was packed with bags of clay, tightly rammed. In front of this was placed a steel bulkhead with a steel door, and through the bulkhead three-inch pipes were laid right into the crevice, to allow the water to get out. Through the 6-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 about three months, when the bulkhead door was opened, and sufficient of the bags of clay removed to allow the men to reach the crevice, when they found that the inflow had practically stopped. The bags of clay were completely cemented together.
A detour was cut at this point to about 6 feet, to get round the crevice, and when the men had passed it they worked back to the original line of excavation.
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 50 feet 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 2400 gallons an hour. This was not sufficient to stop the progress of the work, but pumps were installed to cope with the inflow.
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 -it was a great moment -the men broke through. Away in the distance they could see a tiny gleam of daylight. It was the opening at the Long Nose Point side. Their calculations had been made with remarkable accuracy. The centre line, when the tunnel was connected, was only an 1/8th of an inch out, while the levels were absolutely correct.
BEHIND THE GREEN DOOR
If You have ever noticed street corner pillar boxes painted Sydney County Council green,
YOU may have vaguely imagined they were some kind of large fuse boxes. But, in fact,
behind the green doors lie another part of subterranean Sydney.
Unlock the door of a pillar box and you will find a hole in the ground below street level
big enough to take a couple of men and a large power line which the SCC calls a low voltage distributor.
Sydney's electricity comes mainly from Vales Point near Newcastle. It travels in high voltage form to reduce the amount of electricity lost in transit. When it reaches Sydney it goes to substations which break it down from 33,000 to 11,000 volts. One such substation is located at Lincoln Street, Woolloomooloo, which is also the start of the SCC's only tunnel still in use. There is one under the Harbour from Long Nose Point, Balmain, to Greenwich on the north shore, but this is flooded and is no longer used.
To inspect the Woolloomooloo tunnel one needs special permission from the SCC -and a torch. Most of the light bulbs in the tunnel are out of action. The tunnel itself is a fairly roomy cement affair built in the 1950s. For most of its length it is dry but in a couple of places water has seeped through and is beginning to create small stalactites from the cement roof. It would cost a fortune to build today and it is unlikely that more like it will be built.
An electricity cable being pulled in Kent Street, City, in the 1930s.
It carried cables armoured with steel on the outside and wrapped in lead sheath and paper insulation. You can put your hand on the outside of the cable with no ill effect. It feels slightly warm from all the energy deep inside the copper core. The cables have been there for thirty years and are in good shape.
After walking about a kilometre through the tunnel under the Cahill Expressway, one comes out through a green door into the Domain just below the Art Gallery, and stands blinking in the sunlight. From this point the cables go through concrete underground ducts to smaller substations in the city. After removing the manhole covers at the corner of Phillip Street at Martin Place, you can climb down ladders to about fifteen metres below street level. This is the SCC's biggest and deepest pit. It was built as part of the relocation of ducts during the construction of the Eastern Suburbs Railway. There are empty ducts waiting to take a large number of mains in the future. Digging under central Sydney is becoming increasingly difficult and the Eastern Suburbs Railway is probably the last big excavation that will take place there.
By lifting part of the new paving sections in Martin Place you can climb down to inspect the substation that supplies most of the central banking system of Sydney. If the power fails here, then the computers of most of Sydney's head offices stop too. So the board has not one but three transformers. Any fault in the system is reported by an automatic signalling system and shows up on the mosaic board at the SCC headquarters in Goulburn Street. When a fault is reported by a customer, the SCC will isolate the distributor and, if possible, bring supply round by an alternative route to the customer while they fix the fault. The SCC takes great pride in maintaining its service to customers, and workmen in suitably insulated clothing and shoes actually carry out the repairs to Direct Current distributors while the wires are still live. Direct Current is only used to supply a few old buildings around Chifley Square which have lifts needing this form of current. They are being gradually phased out and should soon be gone much to everybody's relief.
When working in the cramped spaces below street level while repairing low voltage distributors, workmen welcome the sight of cockroaches. Their presence shows that there is plenty of oxygen -an important consideration when you are welding wires in a confined space below ground where there could be gas. Not so welcome are the rats which persist in chewing through low voltage cables, particularly around the Opera House. This has a fatal effect on both rats and cables. Another hazard to the electric supply are con-. tractors excavating foundations for city buildings. Nobody has been killed for about ten years, but this is mainly thanks to the SCC signalling system rather than the care taken by the excavation workers. The signalling system automatically cuts off supply before it can travel through the offending machine and kill the operator. The heat from a main is SO great that it can melt a mechanical digger's shovel in a few seconds. A third hazard is water and, given Sydney's occasional downpours, not even the stoutest pump and the 'largest drainage system could hope to deal with this problem completely.
Electricity authorities have been digging up Sydney to lay cables since 1903. In that year, the Electricity Undertaking of the Municipal Council of Sydney began building the Pyrmont Power Station and excavating over forty kilometres of trenches to link the station with the Sydney Town Hall and Darlinghurst. They also dug a tunnel from the Power Station to the nearby Harbour to provide cooling water. The Power Station is now used as a museum but the tunnel is still there.
The official switching on ceremony took place at the Pyrmont Power Station on 8 July 1904.
"City Blast Scare" screamed the headline in the Sun on 19 April 1977. "Fire Rages Under City Building" shouted the Mirror from the street corner. The Sydney evening Papers are famous for never letting the facts interfere with a good story. By the next day when the whole thing had simmered down, the Sydney Morning Herald reported soberly: ''Gas Main Fire Stops City Traffic". It went on to give details of how a cigarette butt combined
Pulling electricity cables through ducts over a bridge built over the Warringah Expressway at West Street, Naremburn, in the 1970s.
with a gas leak had started a fire at a broken gas main at the corner of Elizabeth and Park Streets. In the words of the famous headline, it was a small fire and nobody was hurt.
It is not the sort of publicity the gas authority seeks out. But it does serve as a reminder of the huge network of gas pipes beneath our city streets and the patient and normally unpublicised work of the engineers and company staff who put them there.
Although gas pipes are normally laid in trenches rather than large tunnels, the Australian Gas Light Company can fairly claim to have some of the oldest networks of subterranean Sydney. In fact, the gas company has been digging up Sydney streets for well over a hundred years.
The company was given a Royal Charter in 1837 and charged with the responsibility of lighting Sydney's gloomy streets. It turned on the lights on 24 May 1841 to celebrate the birthday of Queen Victoria. The sites for its first gas holder tanks had to be hewn out of solid sandstone at Darling Harbour. By 1925,fthe company could proudly claim to be the seventh largest gas undertaking in the British Empire.
Its Mortlake Works supplied gas consumed over an area of 600 square kilometres and piped gas up to 25 kilometres away. Altogether, it had dug trenches for 6400 kilometres of mains and service pipes. In 1875, the Gas Act made it possible to set up a gas service on
the North Shore. James Walter Fell imported all the necessary equipment and set up the first North Shore Gas works at Neutral Bay. By February 1877, the pipes were laid and the first customers were connected. Unfortunately the start of the service was delayed by a severe drought. Gas tanks -geometers as most people still call them -are like huge inverted cups full of gas sitting on water which keeps the gas in. The trouble was that, in February 1877, the North Shore had no water! Finally the rain came and the North Shore gas service was able to start.
The North Shore Gas Company is now merged with its much larger sister company, the Australian Gas Light Company and together they supply the-whole of metropolitan Sydney.
An electricity cable pit in Campbell Street, City.
Like most utilities that dig trenches and tunnels under Sydney streets, the gas company occasionally digs up forgotten bits and pieces of Sydney's past. One such piece was an old wooden tunnel which came to light while replacing pipes at Chatswood. Nobody in the gas company knew it was there. It was made of red gum and filled with sand to stabilise the pipes it carried inside.
In common with other utilities the gas company has' experienced problems in getting its services across Sydney Harbour. However, the gas company has special difficulties because it produces a product that will cause its pipes to float just below the surface of the water where it would be a danger to shipping. So the board has encased its pipes in concrete at Roseville Bridge and the Spit where it crosses Middle Harbour and has done the same for its pipe under the Parramatta River.
This new pipeline for natural gas was laid at the Australian Gaslight Company plant at Mortlake in the late 1970s.
The gas company's supplies are normally carried in pipes buried in trenches. The building of the Warringah Expressway has provided the board with its only real tunnel to add to the network of walkable tunnels around Sydney. The tunnel in question begins at Mount Street, North Sydney, where it goes down for about 10 metres and then continues under the expressway. The total distance is over 100 metres. As it measures nearly three by three metres, it is quite big enough to walk through and it provides access for the Water Board and electricity suppliers who share the tunnel.
The biggest problem faced is one it shares with all other utilities. There are so many services competing for the limited space under Sydney streets. Subterranean Sydney, in fact, is already seriously overcrowded and the situation in central Sydney is getting worse. When digging trenches for the new pipes needed to supply natural gas in the late 1970s the gas company found great difficulty in finding vacant space. At the corner of Sussex and Market Streets, for example, the gas company had to dig through three streets -the existing one, plus two older ones -before they could find a place to put their pipes.
Despite what most members of the public think, the utilities do co-operate with each other. Every time one of them wants a "street opening" they all meet for discussions and take advantage of the opportunity to carry out maintenance and repairs to their own pipes. It makes good economic sense. Up to a third of the cost of a job can be for restoration of the road surface and the gas company, if not the other utilities, is a private company with shareholders to think about.
The gas company tests its pipes with air before covering over the road. But Murphy's Law, which dictates that what can go wrong will go wrong, operates in the gas industry as well as it does in any other human undertaking. In the case of the gas company, a small leak found after the road surface has been restored means that the men have to start digging up the road once more.
Sometimes the problem of digging up the road is complicated by the difficulty of finding the streets under which the pipes were originally laid. Around North Sydney, for example. whole streets were obliterated to make way for North Sydney Station and later, the
Travelodge Motel. The gas mains are still under there somewhere, but the old gas company records give their location only by the names of streets which no longer exist. SO before they can start on repairs and maintenance, the engineers have to spend time consulting old council street maps to find where the streets used to be.
|This section is based on the excellent book by Brian and Barbara Kennedy. (Subterranean Sydney (The Real Underworld of Sydney Town), Reed, Sydney, 1982. ISBN 0 589 50312 X). Copyright Brian and Barbara Kennedy and Reed Publishing.|