Improved Remote Underwater Inspection

New developments in underwater technology make it possible to improve Dam Safety through remote underwater inspection of Dam intake structures and conduits. Areas once thought to be in-accessible by diving techniques are now accessible by new Remotely Operated Vehicles (ROV). Even in 100% turbidity log rack structures have been located and entrance made into the intake conduits to perform routine as well as urgent inspections for structural integrity. With special video cameras small features such as 1/8" separations or joints can be located and visually inspected. Rock traps have been inspected for fill level after 1000 ft penetrations into the intake conduit or penstock structure. Access points such as surge tanks and emergency gate slots as well as the standard penetrations through log rack structures have been successfully used to gain entry into the waterborne areas of a dam.
New developments currently underway to support increased accessibility for security and inspection reasons have led to new ROV systems. Some of these systems are currently used for remote underwater nuclear reactor vessel inspections. These systems are being designed to change their orientation remotely from horizontal to vertical to gain increased access in piping and conduit systems. These newer developments with smaller ROV systems would offer the opportunity to perform inspection activities with minimum shutdown in dam operations. A demonstration of some of this capability was performed at the Warm Springs Dam for the U.S. Army Corps. of Engineers. Within 30 minutes following a simulated seismic event an ROV team demonstrated capability to locate and enter the intake conduit. The log rack entrance was at a depth of 220 ft in 100% turbidity. Conduit entry was achieved and confirmation of features as small as flat head screws in the articulated joint were confirmed intact. The technologies used then and the new developments in ROV systems can be combined to meet the increased demands on Dam inspections, security and safety. 10 pp.