Wells Dam Hydrographic and ROV Video Survey Columbia River, Washington

The boom is anchored to the lakebed with six 20 x 20 foot concrete anchors weighing as much as 500,000 lbs.

Before the installation of the anchors, TerraSond and Global Diving and Salvage conducted a pre-installation hydrographic survey and video inspection survey using a remotely operated vehicle (ROV).

The hydrographic survey provided a broad, high-resolution multibeam dataset of the project and the ROV video provided the visual detail at each anchor site.

TerraSond and Global Diving and Salvage were able to combine their respective areas of expertise to meet the requirements of the project.

• TerraSond conducted a pre-installation multibeam survey of the lakebed with their Reson 8101 multibeam sonar to generate a bathymetric map of the project prior the ROV video inspection.

• Global Diving and Salvage installed an acoustic USBL tracking beacon on their ROV, allowing TerraSond to track the submarine location of the ROV in real-time using Ultra-Short Baseline (USBL) acoustic tracking technology. With TerraSond providing the ROV position, Global ROV pilots were able to"fly" the ROV just off the bottom along pre-designed transect locations.

• The ROV conducted a video inspection along 100 foot long transects and at a 10 foot line spacing. The video was overlaid with position, heading and depth and recorded to DVD.

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