Champions of the Manhole Gauntlet

By Jared Carey, Innovation Specialist

One of TREKK’s infrastructure assessment teams recently faced a mission to inspect a challenging sanitary sewer manhole, with the primary hopes of acquiring pipe diameter verifications. Granted, this story would be a little boring under normal circumstances, but given it was a high-flow interceptor line, roughly 30-feet below grade, well, once you see the photos you will quickly understand why this was a story-worthy endeavor.

Let’s set the stage with the following visuals. Keep in mind, this manhole happens to be above grade by an additional 3.5 feet (just at the edge of OSHA fall protection requirements), thus layering additional concerns as we brainstorm ways to derive said measurements at the bottom, safely.

Now realize, this wasn’t just any typical run-of-the-mill structure (“Never judge a manhole by its cover,” right?). No, this structure happened to be riddled with a gauntlet of obstacles inside that would pose challenging to even a well-trained confined space entry team. With two random crossbeams bridging the walls and a 24-inch inner drop pipe obscuring most of the manhole chamber, our crew couldn’t get a clear visual of what was down there.

Worse, because it was connected to a large diameter sewer interceptor, this particular structure also suffered an aggressive amount of deterioration due to the presence of hydrogen sulfide gas.

Based on these facts, it was obvious this was going to be too dangerous to dive into get those desired measurements.

If we weren’t going to send a human down there, then the next logical step is to turn to robotics or 3D scanning to get the job done. However, with the given obstacles, not just any system could safely maneuver around this massive pipe barring the way (below left), or around these beams, quite so easily (below middle). And worse, if you made it that far, would you personally want to risk expensive camera/scanning gear around a pipe with this much flow coming out of it (below right)?

Don’t forget, the camera has to be maneuvered through a fall protection guard, too. (In this case, it was a safety protocol. And safety protocols must be upheld!) An interesting problem, no?

At TREKK, we have tested various manhole scanning technologies off and on for quite some time now. With our most recent breakthrough of acquiring 3D scans using our TREKK360 camera system, we decided our camera might be nimble enough to make the journey. Granted, we knew it might be a tough ride to the bottom for our gear, but none of us thought the results would be so clear and comprehensive as what you’re about to see below. (Keep in mind that this is an inside-out view of the manhole, with the inner walls projected to the outside of the 3D model, for faster visual comprehension of what’s going on inside.)

As you can see, we were indeed able to extract what our TREKK360 captured into a really nice, scaled 3D model. And, lo’ and behold! Ultimately, we were able to get those pipe measurements from what it could see! With limitations, of course. Not all of the interceptor pipe could be seen due to the large drop pipe in the way, but the interceptor diameter was spot on with what the GIS identified as 120 inches across. So, mission accomplished, right?

The plot thickens further still. Look at the infiltration and pipe corrosion we caught as a bonus result:

That large interceptor is corroded beyond even the rebar, and the amount of groundwater infiltrating at the top of the pipe is likely making a sizeable impact on a treatment plant downstream. This structure and the adjacent pipes need urgent repair to prevent further damage to a system many citizens use. And this is just one example of many we were able to discover, all from our light and nimble TREKK360 scanning system. (Check out our interactive 360 photo viewer for the manhole above.)

Every inspection counts, and it only takes one out of a few hundred inspections to reveal a substantial defect like the above. So, if manholes across your system haven’t been looked at in a while, or you have infrastructure that needs investigating, but it’s too unsafe to explore, reach out and let’s tackle this together! Here at TREKK, our teams look at a challenge like this as if it’s just another engineering problem. With our innovative resource pool, we can help you reach solutions that are practical with an approach that fits your budget, and safety will always be the top priority. After all, the more we can avoid risking lives, the more we can keep improving them. And we’re excited to find ways to help you do the same.