How to inspect sealed, toxic underground channels without putting workers at risk has been a longstanding question at the Lethbridge Wastewater Treatment Plant. The answer has come in the form of a homemade, low-cost drone.
For years, plant operators knew hydrogen sulfide gas was corroding concrete inside enclosed wastewater channels at the Alberta facility. But with no inspection ports and gas levels far exceeding safe exposure limits, sending workers inside was not an option. Shutting down operations to investigate was equally impractical, leaving staff unable to assess the extent of damage or emerging blockages.
That changed when Lee Allen, the plant’s senior system integrator, designed and built a remote-controlled boat drone capable of navigating the narrow, submerged channels.
“There was no good way to peek inside,” Allen told City of Lethbridge officials. “It’s a small, enclosed concrete channel with no inspection ports and you can’t put a person down there.”
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The custom-built device, inspired by an idea from the plant’s Maintenance Lead, Shaun Young, was developed by Allen over three months using 3D printing and off-the-shelf components. It floats along the wastewater surface, maneuvering through tight bends while transmitting live video back to operators via an Ethernet-enabled camera system. Controlled with an Xbox 360 controller, the boat-style drone uses dual jet drives to maintain stability and precise movement in confined spaces.
Allen completed the project for less than $1,000, far below the cost of comparable commercial systems, which can run into the tens of thousands.
“Having access to the on-site 3D printer is huge,” he said. “You don’t have to be a lifelong expert in each field. It’s more like assembling modules than building everything from scratch.”
Initial testing in a local stormwater pond confirmed the drone could skim, pivot and remain stable. When deployed inside the sealed channel, it delivered the first-ever visual assessment of the space.
The footage revealed the concrete structure was in better condition than expected, easing concerns about severe corrosion. However, it also uncovered a significant buildup of grease and organic material along the channel floor and walls, large enough to require staged flushing and ongoing maintenance. The boat drone was unable to pass beyond the blockage.
Hydrogen sulfide levels in the channel measured around 35 parts per million, well above Alberta’s occupational exposure limit of 10 ppm. While the gas remains contained underground, the readings underscore the risks that had previously prevented inspection. Three wastewater plant workers died in Texas last summer following a suspected hydrogen sulfide gas leak that occurred during a lift station repair at the Westwood Shores Municipal Utility District wastewater plant.
Plant Manager Adam Campbell said the Lethbridge project delivers value on multiple fronts.
“This tackles a real issue, it’s very cost-efficient and it creates a high level of team engagement,” Campbell said. “It’s great to see Lee combine his personal interests and skill set to improve operations.”
Allen, who grew up building remote-controlled machines in his father’s garage, said the goal is not to replace workers but to make hazardous tasks safer.
“Our systems take on the dirty, dangerous, boring work humans shouldn’t have to do,” he said. “Robots should make human work safer, more fun and more meaningful.”
With the success of the boat drone, Allen is already developing his next project to target sludge removal in the wastewater lagoons, continuing his hands-on approach to solving real-world infrastructure challenges.
