What are these pointy, yellow street utility poles?

January 9, 2012 8:44 AM

What is the purpose of these yellow, columnar, pointy-topped utility structures found frequently on the streets of St Louis: [ex. 01 ^[gmap] || ex. 02 ^[gmap] || detail]?

There are several dozen of these that I've seen all over St. Louis. What are they/what do they do/how do they work?

The structures look quite a bit older than the solar panel/antenna that's mounted to them; I suspect that these power/transmit status information that was once gathered by hand.

I thought I smelled a faint odor of natural gas from these two that I photographed close-up; though this might be my imagination. Many thanks for your help.

posted by jjjjjjjijjjjjjj to technology (14 answers total)

They look like vents; the cap prevents rain from going down the open pipe.

Locals with a better sense of St Louis infrastructure could probably give a better idea of what they're venting...
posted by Admiral Haddock at 8:48 AM on January 9, 2012

I'm gonna guess tornado warning sirens.
posted by ghharr at 8:51 AM on January 9, 2012

Twenty-five seconds on Google tell me they are tornado sirens.
posted by TinWhistle at 8:51 AM on January 9, 2012

Twenty-five seconds on Google (and a basic knowledge of acoustics) tell me that they are not tornado sirens.
posted by jjjjjjjijjjjjjj at 8:59 AM on January 9, 2012 [9 favorites]

This is my old neighborhood. Most of the blocks around Tower Grove Park and many elsewhere on the south side have signals that chirp to let the visually impaired know when it's safe to cross the street.

The Missouri School for the Blind is just across the park to the north (of your first link). The tornado sirens tend to be located on top of larger, often public buildings (schools, libraries) and are centrally located in neighborhoods, not placed at every major intersection.
posted by Emperor SnooKloze at 9:01 AM on January 9, 2012

I'm familiar with the chirping walk/don't walk signals near the school for the blind (3 blocks away from me, now). This isn't that. I've seen these structures throughout the city (and they'd be a bit over-engineered for the job of chirping at pedestrians).
posted by jjjjjjjijjjjjjj at 9:06 AM on January 9, 2012

I hate to give speculative answers, but maybe this will help to find the difinitive one:

We had similar things in Detroit when I was growing up. Ours were green and a slightly different shape. As a child in the cold war era, I always thought they were missles, ready to launch at Russia. When I was old enough to be curious enough to actually ask, my mom and big brother told me they were something to do with "gas." I also have a memory of a gas smell near them, and sometimes a low hissing sound, but memories from 40 years ago can be unreliable.

So, I thought they were natural gas vents, but this is proving to be something difficult to find information about online.

(And, yeah, TinWhistle's link is just one person saying that's what they were because they were standing next to one when a tornado siren blew.)
posted by The Deej at 9:10 AM on January 9, 2012 [1 favorite]

There are similar structures in Queens, NY that are identified as natural gas regulator vents. Also, gas pipes are commonly painted yellow.
posted by zsazsa at 9:16 AM on January 9, 2012 [1 favorite]

Yellow is the Uniform Color Code for gas utilities.

Red is electricity, orange is telephone, green is sewer and blue is drinking water.
posted by JackFlash at 9:23 AM on January 9, 2012 [3 favorites]

zsazsa's link seems to hold an answer. "Natural Gas Regulator Vent" is seeming like the most probable function for these poles.

(Any info on what it is that a natural gas regulator vent does would be welcomed. Also: very pleased to have learned about the "Uniform Color Code". Many thanks for all your answers. )
posted by jjjjjjjijjjjjjj at 9:37 AM on January 9, 2012

If I had to guess, I'd say they were natural gas vents for pressure relief. The one on Kingshighway is adjacent to a roadway box (you can see it in the picture; I know it's there because before they re-paved that used to eat my suspension) for some utility. The one on Oak Hill has gas utilities (the yellow marks) very close to it and I'd bet if you looked out in the street you'd see another roadway box. It might even say what utility it's for.
posted by notsnot at 9:38 AM on January 9, 2012

(I wrote that before I saw your followup.)

A regulator vent would be for if the pipe pressure became elevated beyond safety margins. Better to vent to atmosphere than blow up, yes?

Pressure spikes could happen near large-demand locations: schools, factories, etc. Just like water hammer and flush-valve toilets, only with gas as the working fluid instead of water.
posted by notsnot at 9:44 AM on January 9, 2012

Yeah, a friend of mine lives near Humphrey and Oak Hill and one of these caught my eye when I parked by his house recently. He told me it's a natural gas pressure relief thing.
posted by evisceratordeath at 10:26 AM on January 9, 2012

Any info on what it is that a natural gas regulator vent does would be welcomed.

Uh.... prevent this?

How does the natural gas delivery system work?
The gas utility's central control center continuously monitors flow rates and pressures at various points in its system. The operators must ensure that the gas reaches each customer with sufficient flow rate and pressure to fuel equipment and appliances. They also ensure that the pressures stay below the maximum pressure for each segment of the system. Distribution lines typically operate at less than one-fifth of their design pressure.

As gas flows through the system, regulators control the flow from higher to lower pressures. If a regulator senses that the pressure has dropped below a set point it will open accordingly to allow more gas to flow. Conversely, when pressure rises above a set point, the regulator will close to adjust. As an added safety feature, relief valves are installed on pipelines to vent gas harmlessly, if a line becomes overpressured and the regulators malfunction.

I am surprised they don't have an obvious utility tag of some type.
posted by dhartung at 3:50 PM on January 9, 2012