Maintenance covers and Hydro Ottawa’s chamber of secrets

Each day, thousands of Ottawa residents step outside to walk, bike and drive along the city streets. You need not to look far to see the hustle and bustle of activity. However, what isn’t as obvious is located just a few inches below concrete and asphalt - Ottawa’s very own chamber of secrets with a different kind of hustle and bustle.

In all likelihood, you have seen or walked across the access portals to these chambers as they’re fairly easy to spot: large, circular iron covers labelled “Hydro Ottawa,'' most often found along sidewalks or in close proximity to buildings. Hiding neatly below these circular lids called “maintenance covers” (or once commonly referred to as “manholes”) is a broad network of underground cables and infrastructure that deliver electricity to homes and businesses. 

To help unveil the mystery beneath these Hydro Ottawa maintenance covers, we want to give you insight into why they exist, how they are designed, the dangers lurking within these enclosed chambers, and the most common misconceptions.

Why underground? 

There are several benefits to housing these electrical systems underground. First, it helps keep them tucked safely away from potential damage related to human, weather, or animal interference. This increases reliability and limits safety hazards to the public as well. Placing these systems underground also replaces the need for overhead distribution lines which can be not only visually unappealing but also obstructive, particularly in high-density areas. While underground electrical infrastructure is often preferred for these reasons, it requires a great deal of forethought during City planning since excavation can be invasive and costly depending on how developed the area is. Currently, 54 per cent of Ottawa’s electrical system runs underground compared to 46 per cent running through overhead distribution lines.

A complex design network

Beneath a total of approximately 4,121 Hydro Ottawa maintenance covers are chambers that connect vast duct structures and substations to deliver electricity to customers across the city. Within these duct structures are over 3,000 kilometers of cables with different voltages and compositions. From sub-transmission to distribution and transformers, these chambers allow our teams to install new infrastructure and effectively upgrade, repair and replace cables that are damaged or at the end of their life expectancy. Maintenance holes provide access to and protection of a large portion of our electricity grid, predominantly in the downtown core of Ottawa. 

Highway to the danger zone

One of the greatest safety hazards of maintenance holes is that the air quality may be poor for human inhalation. Fumes from exhaust, gas leaks and decomposing organic material can make the chamber unsafe. For this reason, hydro crews take air samples before entering a maintenance hole and continue to monitor the air quality at all times for their health and safety. A mechanical ventilator is also used to bring fresh air from outside into the chamber. Crews are trained for these complex conditions and regularly practice rescue techniques should a fellow crew member ever become injured or unconscious while working within the chamber.

Common misconceptions

Given the mysterious nature of underground systems, it’s not surprising that there are several misconceptions related to them. One such misconception is that maintenance holes are part of the sewer system. Since water and electricity do not mix, while they both exist underground, they are in no way connected. A question that our crews are often asked is: “Are there rats down there?”. Thankfully, it is extremely rare that we ever find any rodents or wildlife within the chambers - however, our crews know that the fumes are getting to them when they start seeing the Teenage Mutant Ninja Turtles.

So the next time you take a walk around the city, try looking down! See how many Hydro Ottawa maintenance covers you can spot - especially downtown.  When you do, we hope these fun facts will help illuminate the hustle and bustle of electrical connections happening below the surface.

maintenance-hole

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