Water Corporation is entering the depths of the ocean with Autonomous Underwater Vehicles to monitor the condition of its marine outfall assets.
Inspecting ocean outfall pipelines – water assets that release treated wastewater into the ocean where it is diluted with seawater through various physical and chemical processes – has traditionally been conducted by commercial divers.
Although this method has been employed for a number of years, having professional divers inspect the outfall pipelines presents some major challenges.
In less-than-ideal weather conditions (for example, if there are high ocean swells or cloudy conditions), drivers may need to call off the inspection.
“Human inspection will result in down time, so it can be very costly,” says Venkat Coimbatore, Senior Materials and Corrosion Specialist at Water Corporation.“It’s unsafe for diving to occur if the weather isn’t right for the operation.”
It can also be difficult for divers to gain a complete picture of the outfall pipeline. This is because divers will manually obtain the data, which can run the risk of being imprecise. Some spots along the pipeline may also be overlooked.
“When data is collected from divers, it will come in the form of a long video file. This often contains little reference to problems along the pipeline so it can be hard to identify where the issues lie,” says Coimbatore.
These difficulties have led the Water Corporation to collaborate with specialists in remote technologies, leading to the first trial of Autonomous Underwater Vehicles (AUVs) on Water Corporation’s ocean outfall pipelines which began in October 2021.
While AUVs are commonly used in the oil and gas industry, this is the first time Water Corporation has used AUVs for ocean outfalls.
In partnership with local company Blue Ocean Marine Services, a joint venture between Vertech Group and Blue Ocean Monitoring, Water Corporation is now trialing AUV technology to inspect the condition of its ocean outfall assets and dams in Western Australia.
AUVs in action
Water Corporation manages ocean outfalls in WA in areas including Alkimos, Bunbury, Ocean Reef, Point Peron and Swanbourne. It also has two ocean outfall pipelines from desalination plants at Kwinana, Rockingham and Binningup, Southwest Region that are operated and managed by Water Corporation’s alliance partners.
Annual monitoring of the ocean outfalls is required to ensure compliance with water quality and quantity requirements stipulated by the Department of Water, Environment and Regulation.
AUVs are a highly efficient way of conducting monitoring.
It took divers two days to inspect a 320m stretch of the Cape Peron outfall pipeline, whereas an AUV was able to complete the survey in three hours. This inspection included mobilisation of the AUV, executing the survey of the ocean outfall and demobilising the technology.
AUVs make it possible to obtain a clear view of ocean outfall assets.
“You can create an accurate map showing the location of any defects, burial or free spans, annotated with latitude and longitude,” says Coimbatore.
“AUVs use an inertial navigation system and periodically resurface to realign their position with a GPS so it can pinpoint the location of issues.”
An added benefit is that AUVs can accurately locate the position of the ocean pipe.
“This is important because the position of where the pipe was laid decades ago and where it is now can change. Confirming the pipe’s location is really handy,” says Coimbatore.
“Most importantly, AUVs are very safe to operate.”
Contact Venkat at [email protected]
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