Inside the Collection

Beneath the Streets: the Tank Stream

Part of the Tank Stream sewer
Photography by Sotha Bourn © Powerhouse Museum, all rights reserved

The object above is actually part of the Tank Stream sewer, and surprisingly one of the most significant objects in our collection.

The Tank Stream started as an actual naturally occurring water source and was one of Governor Philip’s formative reasons for choosing the site for the Colony’s first settlement in 1788. It rose in marshy wetland on the western side of the area now occupied by Hyde Park, formed a channel between present-day Market and King Streets, and flowed down to Sydney Cove, entering the Cove at about the middle of what is now Bridge Street. However, it soon became evident that it was not a reliable source of water and during a drought in 1789-90 reservoirs or ‘tanks’ for storing water were cut into the sandstone in its side.

Rural painting by J Skinner Prout
Painting by J Skinner Prout

The stream was used as the colony’s primary source of water for 40 years, but by the 1820s it was so polluted that it was judged unfit for consumption.

It was superseded as a source of domestic water by Lachlan Swamp located on the present site of Centennial Park. In the 1820s a tunnel was commenced to bring water from Lachlan Swamp. Named ‘Busby’s Bore’, the tunnel was completed in the 1830s.

Rural drawing by C H Woolcott
Attributed to C H Woolcott held in the Mitchell Library, State Library of New South Wales

As Sydney continued to develop the Tank Stream became an open drain and sections of it were variously diverted, channelled, enclosed in pipes, or incorporated into an oviform sewer. In the 1930s a new sewerage system was constructed and the Tank Stream reverted to carrying stormwater only.

Section of storm water drain
Collection: Powerhouse Museum

Writers, especially those of the mid-20th century have romanticised the Tank Stream. Said one in the 1940s,

“the Tank Stream, that ‘purling rivulet’ which … was the ‘life blood’ of the early settlement, and the cradle of the Australian nation, has been transformed into a stormwater channel that flows unseen beneath the city streets”*. Nor could the little rivulet be dismissed lightly, wrote another in the 1950s: “What building great or small, in the line of its course, has not bowed to its dictates? The AMP building is built partly on piles driven into the muddy depths. Many an owner has been committed to installing pumps to deal with seepages in basements. The throb, throb, shows that the stream is still alive”**.

Another of those great buildings affected by ‘the little rivulet’ was the Sydney GPO. It was during the erection of this city landmark and the formation of Martin Place in the 1860-1870s that the Tank Stream, by then an open oviform sewer, was covered in at that site.

Little more than 100 years later, the Sydney of the 1990s had become a city of ‘adaptive redevelopment’ and the GPO was subject to an adaptive conversion, transformed from a post office to a luxury hotel, with fashionable ‘uber-chic’ retail outlets, bars and restaurants.

During this redevelopment the Tank Stream conduit was removed where it crossed the building’s courtyard and replaced with a stainless steel pipe that now runs through the ceiling of the hotel’s underground ballroom. Most of the old conduit was a 1940s concrete drain but a small section was a brick oviform sewer. Apparently as a condition of the redevelopment of the site this section was salvaged and part of it incorporated into an interpretive display adjacent to the ‘food and lifestyle experience’ on the lower ground floor of the GPO, where in situ conduit has also been exposed to view.

The archeological remains of the Tank Stream from King Street to Circular Quay are listed on the NSW State Heritage Register and are on the Interim Register of the National Estate. Such listings apparently do not prevent removal and replacement of these remains during redevelopment projects, not even sections that were built in the mid-1800s. However, awareness of the heritage significance of such relics has at least resulted in the oviform section beneath the GPO being saved from destruction. The oviform sewer is about 1.5 metres high and 1.2 metres wide and made of brick. Removing it from the ground intact and transporting it away was a complex and expensive operation that involved bracing two separate lengths of it in situ with expanding foam, then encasing them in a framework of steel girders.

Tank Stream dark underground tunnel with lights along its walls
Image courtesy of Sydney Water

A metre-long slice was treated by a traditional stonemason so that it could be used in the display at the GPO. The two remaining salvaged parts, each around two metres long, were preserved by the development project contractors, Grocon Pty Ltd. With the assistance of heritage architect, Ian Stapleton, these were subsequently donated to the Powerhouse Museum. They are impressive artefacts, intimately associated with Sydney’s development as a city.

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