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CLIENT: IC Pipes
INDUSTRY: Utilities
TYPE OF PROJECT: Sewer Cleaning
WHEN: April, 2020

Brief

In April 2020, IC Pipes were engaged by Sydney Water to undertake inspections of the Randwick Sewer Submain in Coogee, NSW. Traditionally IC Pipes would rely on their CCTV inspection technology to undertake this scope of work. In this scenario, however, the sewer assets were Oviform shaped, with large diameters (approx. 1100-1300mm) and due to more people being at home through the COVID-19 pandemic sewerage flows were higher through the day.

Instead, IC Pipes used new sonar technology known as a Rapid Assessment Condition Evaluation Robot (RACERTM) for the sewer inspection. The RACERTM not only records video to assess damage but can detect the depth of underwater debris within the pipe.

Examining the inside of a sewer with RACER technology.
Examining the inside of a sewer with RACER technology.

From the inspections, IC Pipes operators were able to accurately identify up to 400mm of silt across this 3km asset (approximately 1300 cubic meters). The buildup of silt was a concern. Sewers that become blocked cause a backup of waste that can overflow in residential properties, public spaces and other areas. This would then become a major environmental and public health emergency.

Graph showing the level of debris beneath the water line detected with RACER.
The green line shows the level of debris within the pipe.

From this discovery, IC Pipes engaged Pipe Management Australia (PMA) to remove this silt and debris with our fleet of state-of-the-art drain cleaning equipment.

Challenges

As with any sewer project, there are numerous challenges with respects to environment, safety and community.

PMA had to come up with an innovative approach to the project. Some manholes were over 30 meters deep (below ground level). Additionally, sections of the sewer were made with Glass Reinforced Pipe (GRP). Access to each manhole had its own set of community impacts and traffic control concerns.

Considering the volume of debris, the geographical location of the project was also an issue. The waste removed from the asset would need to be disposed of at a licensed facility. This would dramatically reduce the speed of the project due to the distance needed for vehicles to travel to dispose of their load.

Solution

PMA came up with an innovative solution to remove silt from the sewer in the Randwick Submain in Coogee. To address public safety, the PMA team set up an exclusion zone around the project site. This meant that the street was blocked off and traffic management was implemented during the active hours of the project.

Sewer Cleaning with Vac Trucks

To remove the silt, PMA used a vacuum truck with a pressure hose. The pressure hose is inserted into the sewer. It is fitted a special nozzle, which sprays water back in the direction of the hose. This propels the hose forward through the pipe. It then enables the PMA operator to pull the hose back towards the entry point, flushing the waste back toward the vacuum hose. The waste is then vacuumed into the truck.

PMA's combination vacuum truck and crew cleaning the sewer in Coogee
PMA’s combination vacuum truck and crew cleaning the sewer in Coogee

For this project PMA used a new, heavier design of the torpedo nozzle. This was called the O.M.G. which enabled the delivery of high-water volume at a lower pressure to reduce impact and wear on the GRP sewer pipes.

PMA recognized that the sewer was Oviform (oval in shape) which meant it should self-clean. Instead of having to clean the entire 3km length, PMA started the project downstream (Dolphin Street). They then focussed work on the first 300 metres of pipe. This encouraged the remaining silt (3km worth) to progress down the pipe into the clean zone to then be removed.

Reducing Travel & Improving Productivity

A regular vacuum truck working on a sewer project will fill up with waste relatively quickly as it removes both water and silt from the pipes. PMA used their vacuum trucks with recycling capabilities. These trucks extract and recycle the water that is sucked into the waste tank. This allowed PMA to reduce the amount of waste generated by the project. As a result, there were fewer trips to drop off waste. This increase in productivity allowed trucks to remain on site for longer, while saving water.

A PMA Vac Truck preparing to decant into a silt bucket.
A PMA Vac Truck preparing to decant into a silt bucket.

Often, vacuum trucks will need to travel long distances to a waste facility to empty their load. This can mean that once the waste tank is full, the vehicle won’t return to site until the next day. Due to the vast volume of debris being removed from this project, PMA needed to develop a solution to make the disposal process more efficient. PMA and IC Pipes were able to arrange a dedicated area at a local Sydney Water facility to house multiple sealed waste bins for disposal of debris. This allowed for all vehicles to safely dispose of all captured debris in a controlled environment. By doing so, PMA were able to gain over two hours per day of additional productivity time on site which aided the completion of this project in a timely manner.

Outcome

PMA was able to complete the project and remove 140,000 Kilograms of silt from the sewer in Coogee within four weeks (that is equivalent to the weight of four adult humpback whales). At the end of the project, IC Pipes completed another video and sonar assessment of the sewer. The silt buildup within the pipe decreased to less than 5%. The flow within the pipe had sped up and the risk of any sewer back up or overflow was drastically reduced.

Graph of the level of silt within the pipe after PMA completed the sewer cleaning.
The green line shows the level of silt within the pipe after sewer cleaning was completed.

Completing this project in a timely manner prevented any issues of waste back up or overflow, protecting the environment and ensuring the health of the local community (and whales).

If you would like to speak to PMA about your next project, please contact us for a free consultation on how we can assist you.

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