Local Sewer History Finds
Keeping an eye out for local sewer history finds
Most major cities had their first sewer infrastructure constructed centuries ago. While much of the original networks are either long gone or buried deep underground, if you do a little research and keep your eyes open you’ll likely find some interesting structures that formed part of the original systems. In some cases, these will be decommissioned, others are still in services hundreds of years after they were built.
Finding a piece of Sydney’s sewer history
Out on a recent morning jog in Annandale, I came across a sewer aqueduct that was partially enveloped by the canopy of a large fig tree. Reading the faded plaque on one of the concrete arch supports and reading up on its history, it was interesting to learn about the important role this structure played in the early Sydney sewer network.
The Johnstone's Creek Aqueduct
Designed by Prussian engineer William Baltzer and constructed by Carter, Gummow and Forest in 1896, the aqueduct contains 8 primary arches and has a total length of 281m. It was the first use of reinforced concrete for a large structure in Australia. This very new construction technique of the time was under patent and known as the Monier system. The historical significance of the Johnstone’s Creek aqueduct has led to it being listed on the NSW State Heritage Register.
Transporting sewage to Bondi
The separation of the Sydney’s combined stormwater and sewer pipework began in 1887, and by 1889 the Sydney sewer network had reached 140km of pipe and was servicing close to 25,000 properties across the inner city. With this flow discharging into the harbour, construction of more sustainable options had been underway for some time. Construction of the Bondi Ocean Outfall and Botany Sewage Farm was completed in 1889 and allowed for further expansion of Sydney’s sewer network.
This included the Northern Main Sewer which would service the growing population in Annandale and Balmain and transport flow to a main line junction at the corner of Parramatta Rd and City Rd, then all the way through to Bondi. This extension required crossing both Johnstone’s Creek and White’s Creek with the construction of aqueducts the most suitable design option of the time.
Could reinforced concrete be trusted?
In the late 19th century, the idea of using concrete for such a large structure was not without detractors. The original Public Works Department design called for a brick arch construction and the submission for this new design and material had initially been rejected due to its experimental nature and unproven history. However, support from Robert Hickson (Under-Secretary for Public Works) was interested in trialling the use of reinforced concrete and what was an innovative idea at the time. The Monier design delivered spans that could be 50% larger than brick, and the total cost of the project was quoted as 20% cheaper – it received the go-ahead for construction after test arches were loaded to failure at Burwood with positive results.
The rest is history
It didn’t take long before the advantages of reinforced concrete led to a rapid increase in use for a wide range of structures. The first reinforced concrete water reservoir was built in Kiama just a few years later in 1899. The Annandale Aqueduct has certainly stood the test of time, it required only minor maintenance in its first 90 years of service – far exceeding the 3-year guarantee period. The flume was eventually plastic lined in the 1980s and the arches underwent repair and protection works in 1996.
Still interested in more of the aqueduct’s history?
Well, there was some controversy!
Like any good historical story, the construction was not without controversy. A Royal Commission was held in 1896 and ran for over a year. It was based around accusations of favouritism, contract violations, and defective work. This was not assisted by the fact that at the time William Baltzer suggested the alternate design he was working as a draughtsman in Sewerage Construction Branch of the Public Works Department while also on retainer as an engineer for Carter, Gummow and Forest who were awarded the contract. Despite the large furore and public investigation, the final report fully exonerated Hickson, Baltzer and others involved. It even went as far as finding that some of the allegations appeared frivolous and not founded in truth. As difficult as this must have been for the engineers and others involved in the commission so soon after construction, it is the detailed record of the commission that has provided such informative history and detail about the project from inspection to completion. It was the commission proceedings themselves that meant this significant construction achievement become one of the best documented contracts of the era.
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