Cigar Lake mine in northern Saskatchewan was first identified as a major source of high grade uranium nearly 20 years ago and was due to start production in 2007 after undergoing construction costing in excess of $600 million.
In April 2006, a shaft intended to provide ventilation to the main mine had reached a depth of approximately 1300ft when the miners hit a high-volume groundwater layer and a valve on a two inch grout line leading to this water zone failed, resulting in the flooding of the mine shaft.
The plugging operation was in progress with both Cameco and SeaView Systems’ personnel on location in October 2006 when the main mine suffered a roof cave-in, resulting in the mine flooding at a rate of approximately 15,000 to 20,000 gal/min. Given the estimated $1 billion value of the mine, no time was spared by Cameco in starting on a recovery program. They decided upon a two-pronged approach towards rehabilitation.
SeaView Systems, Inc. was contracted for phase two of the operation to provide their Seaeye Falcon DR ROV. A ‘white paper’ development approach was undertaken with the only restriction being the state-of-the-art of applicable underwater technology. As visibility was expected to be near zero, the need for accurate navigation and the best available real-time remote imaging equipment was a critical requirement for the successful completion of the project.
Having had experience deploying guided inertial navigation systems on the ROV, SeaView recommended the ROV be positioned using a CDL Mini-positioning guided inertial navigation system (INS). Other identified equipment was a DIDSON imaging multi-beam sonar, RDI Doppler velocity log, CDL Minipulse profiling sonar, Imagenex 881a imaging sonar, two Outland Technology P&T cameras and two 150 W DSPL halogen lamps to be deployed in addition to the standard low light Seaeye camera.
Once testing was completed, all equipment was shipped to the Cigar Lake mine where the equipment was mobilized into the main access shaft. Deployment was performed using SeaView’s aluminum deployment cage integrated into the mine’s existing elevator hoist system.
The mission was to dive the ROV in its deployment cage to 1600 feet, fly straight out 100 feet, turn right and travel a further 250 feet while recording profiling sonar data. Accomplishing this required the ROV negotiate past a Bobcat skid steer tractor, a number of cables, pipelines and other infrastructure hanging from the tunnel’s roof, and finally maneuver past a scoop loader (low profile tractor used in mines) that had been used to try to pull the bulkhead door shut immediately prior to evacuation from the flooding mine and was feared to be blocking immediate access to the bulkhead door. Finally, the ROV was to take a video survey of the bulkhead door which, due to the poor visibility, required that the camera be positioned very close to the door and associated slings.
The most important achievement of this project was the demonstration that a small vehicle fitted with a very dense suite of survey equipment and operated by a suitably qualified operational crew was capable of reaching the bulkhead door, and once there was able to perform work. The act of demonstrating the ability to work in the environment opened up a range of remediation options to Cameco, the mine operator.