Dredging works in the harbour of Portsmouth required the assistance of divers. At the same time one of the NINA goals was to minimize diving operations. The team came up with an idea to realize this. Gerrit Jan van den Bosch, Project Manager Boskalis Westminster Limited, UK, shares this good practice.

“In the dredge area many hundreds of obstructions have been located. We decided very early on we would need to use a diving contractor to assist us with the removal of these obstructions. As Portsmouth harbour was heavily bombed during World War II, each obstruction has to be inspected to make sure it is not a UXO ( Unexploded Ordnance ). So we knew this operation would be challenging and time-consuming. Thinking about ways to improve safety and efficiency one of our colleagues from Boskalis Hirdes suggested to use the ARIS camera, which is an underwater sonar device, for the identification. The camera can “see” what’s going on in dark and turbid water. This enables us to continue working in zero visibility conditions.”

“After making sure it was safe to use the device in the water with the diver around, we tried to see if it would work. The procedure: first we inspect an obstruction using the camera. Our UXO expert on board the crane barge assesses the obstruction from the footage. If it is suspected to be a UXO, a qualified UXO diver is deployed for further inspection. For all other non UXO obstructions there is no need to send the diver into the water. We further use the camera to guide the diver straight down to the obstruction, which otherwise would take a considerable amount of time due to the poor visibility on the sea bed.”

“One of our NINA Goals for the project was to minimize diving operations, and by using this method we have. We have also reduced the diver’s time in the water significantly, thus making the hazard and risk to the divers smaller. In addition we can investigate more targets efficiently and safely.”