Hibbard Inshore provides specialty underwater construction and inspection services using Remotely Operated Vehicles and Sensors. In structures like water filled shafts or in front of operating intakes, dredging, demolition and concrete installation become challenging. The typical challenges are the working time of divers, overcoming low or no visibility water, productivity, and safety. The following case studies show how alternative methods make difficult projects possible or at least more cost effective. The sensors and tool capabilities of ROV’s have extended the operating envelope of underwater operations.
A water filled shaft 400 feet deep required a concrete bulkhead to be poured at the bottom. First, the debris and sediment in the bottom of the shaft had to be removed. A ROV used sonar to locate large debris and remove it with its hydraulic arm. Then, the dredge system was lowered into the shaft to begin removing the sediment. The ROV monitored the dredge progress and maneuvered the suction hose to clean all of the sediment. Next, the dredge system was replaced by the concrete delivery system. This was configured to make the concrete controllable during the pour so that just the correct amount was delivered as well as to eliminate washout for a quality bulkhead. The ROV offset significant cost from standard diving methods. The depth would have required saturation diving and the shaft diameter was too small for a standard dive bell. The type of ROV used had the power and sensors to work quickly in low visibility and provide measurements in real time for the concrete and dredging to increase productivity.
An aqueduct
pumping plant required a unit to be put back into service. The head gate between the intake and the
unit was partially covered by sediment. Before opening the gate and commissioning the new unit, the sediment
had to be removed. However, due to
demand, only two adjacent of the many units could be shut down and only for
short times. An unmanned dredging
system was devised including an ROV and a separate sonar system. The
flow in the intake area was far too high for a diver unless most of the
pumping station was shut down. The
traditional diving dredge method required about two weeks. The sonar was used monitor the dredging
process in front of the intake. Inside
the intake, the ROV helped maneuver the dredge to get into tight spaces. The ROV was also able to perform video and
sonar inside the intake to verify that no sediment remained. The unmanned process took just under three
days to do the dredging and final inspection. The pumping plant was able to continue operating at the required
demand using this method offsetting significant safety factors of a diver in
high flow and cost of shutting the plant down.
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