A tailrace tunnel that hadn’t been inspected in over 70 years, a sharp bend, flowing water, restricted access, and a 300KV transmission line at the entrance - capturing a scan sounds like a mission impossible, but not for robotics consultancy, Candrone.
Candrone was able to make the inspection process simple, safe, and economical for the tailrace tunnel owners while extracting the requisite data to develop a preemptive maintenance schedule when they were subcontracted to inspect the tailrace tunnel by engineering and geomatics firm McElhanney. It was the first time an inspection had been attempted since construction of the plant due to the complexity, cost, and risk associated with the exercise.
The hydroelectric generating station is situated south of Kitimat, British Columbia, a planned city built by the Aluminium Company of Canada (Alcan) in the 1950s. Constructed inside the base of Mt Dubose, it is the fifth largest electric plant in the province and supplies power to Alcan’s Kitimat smelter.
Hydroelectric power schemes typically comprise a series of underground tunnels that draw water from nearby waterways through a generating station and out to the ocean.
It’s important this infrastructure is monitored and maintained but until recently, doing so was expensive, hazardous, and disruptive. Typically, an operator would need to shut down the generation plant and drain the tunnels so inspectors could photograph and examine their interiors.
The 8-meter-diameter tailrace tunnel extends 500 meters inside the mountain and has a sharp bend 150 meters from its outlet. Access is restricted at both ends, and, at the time of scanning, the tunnel was half full of rapidly flowing water. Low hanging trees impeded visibility of the tunnel entrance from the only accessible viewpoint, around 200 meters downstream.
Using a Hovermap enabled drone, Candrone was able to circumvent these obstacles and scan the entire tunnel in around 20 minutes while the generation station remained operational.
Candrones made use of Hovermap’s smart battery Return-to-Home feature to maximize flight time and return the drone to base via the shortest and safest route.
To prevent electromagnetic interference from a 300KV transmission line situated in proximity to the tunnel entrance, the drone’s GPS system was disabled, and Hovermap’s SLAM-based mapping and localization capability was used to navigate the flight.
The result? High quality data captured in the most challenging of conditions – few environments require operators to contend with water hazards, aerosols, confined spaces, AND high voltage power lines! – and a very happy customer. In the words of McElhanney Business Leader Marcell Iseli: “This project could not have been executed safely and successfully without Candrone. Our client was thrilled with the results, and we look forward to further collaboration with your team in GPS-denied environments!!