Long Distance Internal Outfall Inspection

For this long distance outfall inspection, Hibbard Inshore used one of their Navajo swimming remotely operated vehicles (ROVs) to inspect an outfall in flowing conditions. The client decided that because of the length of the outfall, the inability to shut down for lengthy periods, and because of the safety risk the 6.5mgd flow posed to a dive inspection that a swimming ROV inspection would be the best option in order to look for structural defects, sediment, and other sources of blockage.

To fight the flows, Hibbard used their Navajo ROV which has very high thrust capabilities for its small size, and it was able to fit through the standard 24” manhole access points available on shore. The vehicle for this project was equipped with dual sonar heads and video cameras. Because the effluent water had limited visibility distance for the camera systems, the sonar heads were important in looking in front of the vehicle to identify sediment level changes or possible issues while the cross-sectioning sonar was able to take dimensional cross sections along the length of the outfall. These sonar measurements were coupled with the video to give the customer an accurate depiction of the outfall.

Hibbard Inshore’s ROV pilots inspected the outfall in its entirety, entering from two different locations in order to cover the outfall’s entire length. The sonar was run continually for feature detection, and stationary sonar snapshots were taken at 100’ intervals, inspecting areas of interest further with video cameras if features of interest were detected. During the inspection, several previously unknown features of interest were noted including the presence of boards left under each manhole from previous manned entries as well as large sections of poly hose and other debris. These features were cataloged for future removal by the customer. At the end of the inspection, more than 7500’ of pipeline was inspected in flow.
Using Hibbard Inshore’s swimming ROV allowed the client to conduct a thorough inspection of their outfall without fully shutting down the operations of their plant which was critical to serving the community’s processing needs.