Photogrammetric modelling of the Grand Falls Generating Station intake tunnel
University of New Brunswick
The Grand Falls Generating Station is located in Grand Falls New Brunswick on the Saint John River. The generating station is typically shut down once every four years for only a few days to perform visual inspections and maintenance of the intake tunnel. Estimates of the size and location of erosion-induced cavities are documented in reports and spreadsheets, which are then used to plan and prioritize maintenance. Interpreting inspections in preparation for maintenance is challenging given the size of the intake tunnel, the subjectivity and selectiveness of the inspections, and the difficulty in linking the spatial evolution of erosion between subsequent inspections. A photogrammetric inspection system was developed to document the visual and spatial condition of the Grand Falls intake tunnel in a 3D model. A robotic data acquisition system incorporating microcontrollers, wireless technology, and photography equipment including lighting was designed, fabricated, tested, and refined to facilitate data capture. Approximately 5,000 images were taken of the 822 m concrete-lined section of the Grand Falls intake tunnel during a two-week scheduled shutdown for maintenance and repairs. The images were processed and combined with traditional surveying to generate an accurate and high-resolution 3D model. A custom interface was designed to visualize and interact with the model and incorporates an inspection-specific tool set. The Grand Falls intake tunnel model will enable more informed decisions on how to manage the intake tunnel and could lead to reduced lifecycle spending, reduced risk of failure, and extended service life. NB Power senior management are enthusiastic about the results of the research and see significant value in using the photogrammetric inspection system at a variety of NB Power facilities. An additional pilot study was completed in Unit #5 at the Mactaquac Generating Station.