Sydney Harbour (Balmain to Greenwich) Railway Electricity Tunnel | NSW Environment & Heritage

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Sydney Harbour (Balmain to Greenwich) Railway Electricity Tunnel

Item details

Name of item: Sydney Harbour (Balmain to Greenwich) Railway Electricity Tunnel
Other name/s: Sydney Harbour tunnel, Balmain to Greenwich Electric Cable Tunnel
Type of item: Built
Group/Collection: Utilities - Electricity
Category: Other - Utilities - Electricity
Primary address: Under Sydney Harbour, Birchgrove, NSW 2041
Local govt. area: Leichhardt

Boundary:

Rail owned portion of tunnel.
All addresses
Street AddressSuburb/townLGAParishCountyType
Under Sydney HarbourBirchgroveLeichhardt  Primary Address

Statement of significance:

The tunnel is significant as a major technological and engineering achievement and was the first such venture to be undertaken in Australia without overseas assistance. It was a major link in the power supply to the railway and tramway system between Sydney and the North Shore and although flooded is an important element of the development of public transport in Sydney.
Date significance updated: 04 Dec 14
Note: The State Heritage Inventory provides information about heritage items listed by local and State government agencies. The State Heritage Inventory is continually being updated by local and State agencies as new information becomes available. Read the OEH copyright and disclaimer.

Description

Construction years: 1916-1924
Physical description: STRUCTURES
Tunnel under harbour and entrances built 1916-1924. The tunnel is lined with concrete in some areas, cast iron in some and the rock in others. At the centre of the tunnel is a large chamber where pumps were located to remove water. Running the length on one side are cement racks to hold the high tension wires to supply electric power for trams and trains on the north side of the harbour. The tunnel held twelve cables, 8 x 11,000 volt and two 50 pair communication cables. At one end was a pool some six feet in depth, to collect soakage, and be pumped to the surface.

The tunnel is perfectly straight, except at Greenwich Point, where it takes a bend to allow an outlet. 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 be made. Here the grade is 1 in 1.3.
Physical condition and/or
Archaeological potential:
Unknown. Tunnel has been flooded.
Further information: This listing is for the railway owned portion of the tunnel. Also see SHR listing for full tunnel: Railway electricity tunnel under Sydney Harbour (Listing number: 01231).
Current use: none
Former use: Railway Electricity Tunnel

History

Historical notes: This was the first tunnel to be constructed under Sydney harbour. 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.

When it was built, the tunnel was one of Australia's major engineering feats. At the commencement of the work, the necessary compressor was located on the south to 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. Progress was rapid for a while -about 25 yards per month at every point. But then residents of Long Nose Point, in letters and protests, 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.

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. 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.

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.

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 the men broke through 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.

In 1952 the Electricity Commission took over all power generation but the railways retained the tunnel and cables. The tunnel ceased use in 1969.

Recommended management:

1. Conservation principles: Conserve cultural heritage significance and minimise impacts on heritage values and fabric in accordance with the ‘Australia ICOMOS Charter for Places of Cultural Significance’. 2. Specialist advice: Seek advice from a qualified heritage specialist during all phases of a proposed project from feasibility, concept and option planning stage; detailed design; heritage approval and assessment; through to construction and finalisation. 3. Documentation: Prepare a Statement of Heritage Impact (SOHI) to assess, minimise and prevent heritage impacts as part of the assessment and approval phase of a project. Prepare a Conservation Management Plan (CMP) prior to proposing major works (such as new additions, change of use or proposed demolition) at all places of State significance and all complex sites of Local significance. 4. Maintenance and repair: Undertake annual inspections and proactive routine maintenance works to conserve heritage fabric in accordance with the ‘Minimum Standards of Maintenance & Repair’. 5. Movable heritage: Retain in situ and care for historic contents, fixtures, fittings, equipment and objects which contribute to cultural heritage significance. Return or reinstate missing features or relocated items where opportunities arise. 6. Aboriginal, archaeology and natural heritage: Consider all aspects of potential heritage significance as part of assessing and minimising potential impacts, including Aboriginal, archaeology and natural heritage. 7. Unidentified heritage items: Heritage inventory sheets do not describe or capture all contributory heritage items within an identified curtilage (such as minor buildings, structures, archaeology, landscape elements, movable heritage and significant interiors and finishes). Ensure heritage advice is sought on all proposed changes within a curtilage to conserve heritage significance. 8. Recording and register update: Record changes at heritage places through adequate project records and archival photography. Notify all changes to the Section 170 Heritage & Conservation Register administrator upon project completion.

Listings

Heritage ListingListing TitleListing NumberGazette DateGazette NumberGazette Page
Heritage Act - s.170 NSW State agency heritage registerSydney Harbour Railway Electricity Tunnel5062542   

References, internet links & images

TypeAuthorYearTitleInternet Links
WrittenBrian and Barbara Kennedy1982Subterranean Sydney (The Real Underworld of Sydney Town) - in Sydney Architecture webpage View detail

Note: internet links may be to web pages, documents or images.

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Data source

The information for this entry comes from the following source:
Name: State Government
Database number: 5062542


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