What in the world is that? Unanswered questions about things seen while riding

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Eric
Member
#

Wanted to start a new thread for things you see around Pittsburgh while riding that makes you wonder, “What the heck was that for?”

I have a few to start.

1) The tall steel vents coming out of the Ohio River between the stadiums. They’re vents of some sort, but what are they venting? I never see anything coming out of the vent, and birds stand on the top, so I’m assuming this is a passive venting system (ie., if anything is coming out it isn’t at a high velocity). Is this for sewer pipes that run under the river? Is this a fresh air intake for the T tunnel that runs under the river?

2) On the GAP trail between the Waterfront and McKeesport there are many square concrete posts along the hill side of the trail, most with rebar sticking out of them. They are in sets of 2s and 4s. They obviously were supporting something, but what?

3) Also on the same stretch of trail there are quite a few steel bench looking things, but they’re obviously not benches. They’re made out of steel pipe, are maybe about 10 feet long, with the “Bench top” made up by 3 parallel rows of pipe. They are about 1-2 feet off the ground. Someone has helpfully put driveway reflectors on them. I have no idea what they are for. I was thinking that maybe they were for cooling whatever is running through them. Usually when you see pipe in parallel like that they’re trying to increase surface area and thus increase cooling. But what is running in there? The pipes are unmarked, and I’m assuming if it was something dangerous it would be not right next to the trail without a barrier and would have warning signs all over them.


Steven
Participant
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Some guesses:

(1) Are you talking about these posts? They’re at both sides of that area that slopes into the water, so I’d guess they’re for tying up some kind of water craft. The aerial view in Google Maps shows some boats that appear adjacent to those posts, perhaps tied to them.

(2) The Whitaker Flyover Bridge on that section of trail “crosses the rail yard so the trail could travel along what was previously a pipeline that delivered coke oven gas to the Steel Valley mills from the Clairton Coke Works.” (Steel Valley Trail website) I’d guess those are supports for that former pipeline.

(3) Underground gas lines typically come up to the surface periodically for maintenance purposes, so they can insert inspection equipment into the pipe and stuff like that. Maybe that’s what those are, though I can’t explain the lack of warning signs.


Eric
Member
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1. Those posts.
2. You nailed it. I’m sure that’s what they are.
3. They don’t have openings so I don’t think it is a natural gas pipeline


Eric
Member
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About #1 — they aren’t for tying up water craft.   There are watercraft tie-ups all over the north shore riverwalk where boats tie up.  I’m on the trail about 4-5x a week and I’ve never seen a boat tied up to them.

Interestingly, though, the other set is on the other side of the Ft. Duq bridge and they also occur in a pair where the riverwalk slopes into the water… So maybe it has to do with marking the edges of the concrete slope into the water?  maybe they’re not vents.

 

The streetview of the trail is cool.  It’s old pictures! It looks like it was before they paved the trail surface.  Also there are still those diamonds in the concrete outside of PNC park on the trail. Those are long gone. they’re also on the other sidewalks of PNC park, and they’re horrible — they’re raised and askew and a tripping hazard.  So they weren’t a good idea to begin with… But neat seeing them on the trail.

 

also the dangerous river ave tracks were in much better shape then. And there was a broken old trailer on the trail back then too at the same place.  So neat.


paulheckbert
Moderator
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#3: there’s a buried natural gas pipeline parallel to the trail, near Kennywood. It’s typically 1 or 2 feet down, I think. In places, the pipeline comes closer to the surface (I think it’s called a gas pipeline expansion loop — google that) and the more-exposed pipe is guarded by those visible pipes. It would be bad if a rockfall punctured the gas pipeline and an inferno erupted, for example.

Note that the buried natural gas pipeline is separate from the former above-ground coke gas pipeline.


Eric
Member
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thank you paul!

 

So I think we got all 3 answered.

#1 – they appear to be guards so that you know where the concrete slope ends so you don’t accidentally beach your boat while boating overthere.

#2 – old pipeline supports

#3 – expansion loops for the natural gas pipeline.

https://engineering.stackexchange.com/questions/569/what-is-the-purpose-of-these-diversions-in-a-natural-gas-line

Hopefully this thread can continue with other questions.


Ornoth
Member
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#1: Not sure if this is the case here or not, but having lived by the ocean for 50 years, those posts immediately scream “tidal dock” to me. A floating dock is attached to a static piling via a big D-ring, so that the dock is always floating at water level, irrespective of the height of the tide.

Same thing can be seen here where the South Side Marina docks float on the Mon, and they can rise or lower to accommodate the changing water level. It’s less common on rivers than in ocean harbors and tidal estuaries, but the idea’s the same.

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