The ‘Tell-Tale’ Mystery of the Underground
Ruminations on what metal bars and chains dangling from ceilings of sewers might be used for
One thing that’s been bugging me for the past couple of years is what purpose these suspended metal poles serve. They’re always found close to the top edge of a dropshaft that’s six or more feet in height. Sometimes there are just one or two, or in the case of the sewer I was in last night, sometimes there’s a large batch of them. They’re always the same width and made with the same material. There are also eyelets at both ends of the pole: a large one at the top that fits through the fixture in the ceiling and a smaller one at the bottom. Both the old and more recently built sewer systems in Montreal have them.
I once came across some blueprints from the City which referred to these poles as “tell-tales” but that doesn’t really “tell” me anything at all. They’re fairly light and swing back and forth easily if pushed. They’re not robust enough to serve as safety features, though they do come in handy for hanging onto if ever you want to step out close to the edge. A chain or an actual railing would be much more practical if that’s what they were supposed to be used for.
They also don’t seem to be there to measure flow rates or water levels. The trash that accumulates on them gives some indication as to how high things might have been in the past, but wouldn’t provide the degree of accuracy to satisfy hydraulic engineers.
I know that tell-tales are used in sailing to help gauge wind direction and speed. I suppose that if there was a large enough air disturbance in the sewer, these poles might start start moving a little. Water falling down a dropshaft can definitely cause changes in air pressure which can often lead to problems, but I’d be surprised if the poles were hung up to indicate that. I mean, it also seems like a pretty low-rent way of doing it.
Anyone else out there have any ideas? Please don’t make me call the City’s Public Works department to get an answer for this one. You’re my only hope.
Update – As a friend of mine pointed out:
“I’m pretty sure the dangling things are warning devices similar to these. They’d indicate to anyone riding on top of a car an impending area of low clearance like an underpass. Underground, I suppose if a worker was disoriented and/or his flashlight died, a smack to the face from one these would prevent him from walking off a ledge.”
Works for me! Thanks, Rich.