Inspection Of Fully-Submerged Water Intake Tunnel

By Jeff Griffin, Senior Editor | December 2013, Vol. 68 No. 12
Readying the crawler fitted with underwater laser for deployment.

“With this system,” said Wilkinson, “IPI is able to inspect more than 6,000 feet of pipe in a single run, the first time this has been done in a municipal water system anywhere in the world using a high-resolution, 525-line CCTV Camera fitted with the an underwater laser. The Inuktun crawler and camera set up includes three onboard video cameras, multiple sensor options, and is operable in pipe with internal diameters as small as 12 inches.”

Setting up at first deployment with Mobile Command posts in place.

2G Robotics describes its line of underwater laser scanners and image enhancement software as exceeding the capabilities of traditional sonar and video inspection to provide detailed examination of even the slightest variances in underwater environments. 2G Robotics ULS-200 underwater laser scanners capture detailed point cloud models of underwater assets. These point clouds are digital 3D models that can be viewed and investigated digitally. Using these digital 3D models, engineers are able to obtain precise measurements.

Because of configuration of the tunnel, it was impossible to use the full 6,000-foot capability of the Inuktun system. Inspections were made in three segments of 1,076-, 3,201- and 4,423 feet.

Wilkinson said the first run was a deployment into the intermediate access in the middle of the tunnel run in the concrete lined horseshoe shaped section of the tunnel which allowed Inspection in both the upstream and downstream directions from one set-up point. The last run was the wood stave circular tunnel section where the water is collected from the lake and runs to the gate house. The approximate diameter for both the horseshoe and the circular tunnel profiles is 6½ feet.

Divers

Divers from Leviathan Underwater Services were used in all deployment and retrieval functions.

“The divers were very professional in carrying out needed underwater support of equipment placement and extra video and communication feeds while evaluating the access shafts and underwater setup functions from topside,” Wilkinson said.

IPI employed two shifts which allowed inspections to continue 24 hours per day. Project Manager Bryce James, who has NASSCO’s PACP certification, led one shift and IPI General Manager Pat Shepp supervised the other.

For overall operations, IPI crews consisted of one operator and one technician. An applications engineer from 2G Robotics also was on site. Leviathan’s crew consisted of three certified commercial divers. All were used during deployment and retrieval and the IPI crew of two for the duration of inspection.