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Video paper: SeaBat sonars supported by Teledyne PDS for High-resolution Tunnel Surveys

The La Higuera project is co-owned by Pacific Hydro and SN Power and located approximately 150 km south of Santiago, Chile. The headrace tunnel known as the Tinguiririca Tunnel is 18 km in length and was constructed using drill and blast techniques.

In August of 2010, a 20-metre section of the 18 km long tunnel collapsed, forcing a 20-month long closure of the tunnel and power station while repairs were undertaken. The collapsed area was sealed off and a 260 metre bypass was constructed to reinstate water flow. During the repair of the main collapse, other sections of the tunnel were reinforced and instrumented so that real-time monitoring could be done under operating conditions. To supplement the on-line sensors, the owners required regular inspections of the tunnel to check for small rock falls, swelling of the rock mass and condition of the rock traps, preferring to do this without de-watering the tunnel. ASI Group of St. Catharines, ON, Canada, was awarded the contract to inspect the tunnel, using a remotely operated vehicle, or ROV, equipped with a unique array of Reson and BlueView sonar systems and a 10km tether to traverse the entire length of the tunnel. The data that the system needed to acquire had to match as close as possible, the level of data that the owner collected with a lidar survey of the tunnel just after the repairs were finished.

This presentation discusses the performance criteria specified by the owner and how these were met through the integration of multiple sonar systems, six of which are provided from the Teledyne group of companies, and a high-level inertial navigation system onto a modified ROV that operates with a 10 km long tether. Representative samples of collected data are also provided from recent inspections.

About Bob Clarke
Over 25 years of experience in the marine industry that includes commercial diving, Atmospheric Diving Suits (ADS) and Remotely Operated Vehicles (ROV) operations. Mr. Clarke is the Senior Operations Manager of Underwater Inspection Services at ASI Group Ltd. His responsibilities include project review; operations planning and supervision; report preparation; and proprietary equipment and database design. He has supervised design/build modifications and retrofits of ASI’s ROV fleet to enhance their operational capabilities and to accommodate new or unexpected conditions on site.