Enlight2786 (002)

Local Sewer History Finds

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.

Sewer aqueduct spanning Johnstone's Creek (Annandale, Sydney)

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.

 

Early example of reinforced concrete in Australia

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.

Looking west from Glebe to Annandale showing construction of Johnstons Creek Sewer Aqueduct. (City of Sydney Archives)

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.

Extract from the Public Works Inquiry Commission

VAPAR.Solutions is designed to process and score video footage from a wide variety of camera systems, providing a single cloud-hosted location for all your inspection videos, images, reports and decisions.

About the Author Mark Lee
IN-R Drone

Sewer Camera – An explanation of the different types of camera hardware

Sewer Camera – An explanation of the different types of camera hardware

The inspection of sewer and stormwater networks is commonly completed using a camera that records video footage from the inside of underground pipes also called the sewer camera. The photos and videos collected during a pipe inspection can be used to assign a condition grade to pipes through the identification of structural and service defects. Councils, municipalities, and water authorities use these condition grades to prioritise pipe maintenance (e.g., clearing roots and debris) and repair (e.g., patches and lining). 

Access to pipes is usually obtained through maintenance holes or pits which can be located within roads, kerbs, public space, and private property.

A variety of different camera equipment is available to record video footage for defect analysis and scoring. Common sewer camera types include:

Crawler Cameras

Crawler cameras are robust remotely controlled inspection robots that traverse through a pipe on wheels. They typically have a strong light source to illuminate the inside of the pipe and are connected via a cable to a vehicle on the surface that supplies power and transmits the video back to a vehicle computer for recording. The robot is controlled by an operator on the surface who directs the crawler’s progress through live vision fed back to their computer monitor. They can adjust for speed and direction, and often have the ability to pan, tilt and zoom the camera lens; leading to the term PTZ camera (they are also called tractor cameras in some regions). Crawler cameras are the most common type used for pipe network inspections throughout the world.

Fixed Zoom Cameras

Fixed zoom, or pole cameras, do not need to travel along the pipe to collect video footage. They consist of a fixed high-definition camera head attached to a pole that is lowered from the surface to the base of the pipe at surface entry locations. Using a combination of strong zoom, focus adjustment, and lighting; a video is recorded as the camera zooms in and the field of vision extends through the pipe from chainage zero to the end of pipe or bend. With a combination of optical (20-40x) and digital zoom (10-15x) they provide a fast and robust way to collect a condition overview of a network.

Image of pole camera for sewers

Push Rod Cameras

House connection branches or sewer laterals present unique challenges when collecting condition footage or diagnosing a problem. Their small diameter and frequent bends mean the larger camera hardware is unable to enter and travel through these smaller lines (typically < 150mm diameter). Push rod cameras are designed for tough and tight conditions. Appearing as a coiled cable on a real with a slim camera head, they can be inserted and controlled manually with imagery fed back to a control unit. The use of skids is sometimes employed to keep the camera head and vision steady and centred.

Pushrod camera for sewers

Inspection Rafts

For large pipes that cover long distances, an inspection raft may be the only choice to collect imagery from within a pipe. These are often used for outfall tunnels where they can be sent downstream and caught with a hook or net at location that could be many kilometres further down the pipe. They are usually designed to stay upright and balanced.

Image of push raft camera for sewers

Drone Cameras

With rapid advancement in UAV technology, the industry has seen an increase in the use of drones for pipe inspection over the last few years. Drones have some distinct advantages in certain situations, including; large pipes with high flow where a crawler may not be able to enter and raft would traverse along the pipe too quickly, and longer pipe inspections where equipment weight or cable length is prohibitive. It will be interesting to see how this technology develops and if it becomes a more mainstream option for pipe networks.

IN-R Drone

Manhole / Maintenance Hole Cameras

There are now a variety of dedicated cameras available for collecting photos, videos, and 3D scans of the vertical shaft that leads down to the benching and pipe channel. In the past this has been completed by visual surface or confined space entry inspection, using a regular camera, or with a crawler as it is lowered down to complete the main pipe inspection. Newer camera technology has been specifically designed to collect more detailed information with much higher resolution than ever before.

Manhole maintenance camera

Jetter Nozzle Cameras

Jetters can be used by operators to clear sediment, obstructions, fats, oils, grease, and roots from pipes. Some hydro jetters on the market include a nozzle camera that can be used to help guide the camera through the pipe, locate specific issues and even steer into lateral pipes. The camera is also able to collect video footage following its cleaning run through the pipe to collect information on the effectiveness of the clean and provide an indication of the condition of the cleaned pipe.

Image of Jetter nozzle camera for sewers

VAPAR.Solutions is designed to process and score video footage from a wide variety of camera systems, providing a single cloud-hosted location for all your inspection videos, images, reports and decisions.

About the Author Mark Lee