Inspecting ocean outfalls or pipelines has traditionally been conducted using commercial dive teams, and although this method has been employed for several years within most utility companies, this can present some major challenges.
Several factors such as sea state or subsea visibility may lead to down-time or postponement of surveys which can be costly, and safety can certainly be compromised under certain weather conditions. It can also be difficult for divers to gain a complete picture of the outfall due to the manual nature of data collection, and data is typically presented in video format with little reference to defects or issues along the asset.
On behalf of the Water Corporation (principal supplier of water, wastewater & drainage services to over 2 million people throughout Perth & Western Australia), Blue Ocean Marine Services executed a number of outfall surveys using Autonomous Underwater Vehicles (AUV) equipped with bathymetric, side-scan sonar and visual payloads. Whilst AUV’s are commonly used in the offshore energy sector this is the first time BOMS have applied their use for nearshore outfall inspection.
The AUVs proved to be a highly efficient and safe way of conducting outfall inspection surveys, when it would take commercial divers two full days to inspect a 300m length of the outfall, the AUV was able to collect a full 3-pass data set in under three hours.
The collected data was then compiled into both 2D and 3D visualization products detailing the accurate position of the outfall, and the specific locations and characteristics of features such as debris, defects, free-spans or burials. Following the success of this project, BOMS are now working with the Water Corporation to survey additional ocean infrastructure and trial the autonomous technology in freshwater environments.
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