They’re putting in a new (average) Wal-Mart at a failing strip mall near me. Watching the construction each day as I drive past, I noticed these sections of HUGE piping, maybe 6-ft in diameter. The pipe is corrogated, and mostlikely made of aluminum, I WAG.
What the heck could this be for? Sewer pipes are usually the largest, correct? Or, is this some kind of reinforcement for the underground to avoid sink holes (using the strength of an arch)?
What do you think’s the deal here?
Sounds like the last piece of the storm drain, i.e., a bunch of small drains go into larger drains until you get to the big ones. They don’t have to be beefy to support anthing, maybe a foot or two of fill, they just make a hole in the ground for the water to go through.
I agree, it’s almost certainly storm drain pipe, and FTR it’s almost certainly made of galvanized steel, not aluminium.
You obviously haven’t worked for the cheap f*ckers I’ve worked for. :rolleyes:
Steel is less expensive.
Oh, okay. I let my impulse to speak badly about former employers take precedent over the importance of facts. I hang my head in shame!!!
It’s referred to as CMP (corrugated metal pipe), and is routinely used for storm drains and culverts. I’ve never seen it constructed of anything but galvanized steel.
Ah, not a thread about Scottish bagpipe music, then? OK, I’ll find my own way out. 
[Side note]I once read a discussion in a civil engineering publication on the mechanics of thin, corrugated pipe for culverts. If I recall the soil around it has to be well and pretty uniformly compacted all around. This provides uniform support all around the circle so that the thin piping doesn’t collapse.[/side note]
This is correct, I was referring to support things like buildings, vehicles, etc.
Since you state that this is a new, but only typically sized Wal-Mart I can make a pretty good assumption. A typically sized Wal-Mart does not need 6’ diameter storm drainage piping to carry away rainwater. That size of pipe can handle a whole subdivision.
What Wal-mart is likely doing with those pipes is creating an underground detention area for rainwater. Most larger urban areas are now subject to stormwater management regulations designed to decrease flooding, erosion, and waterway pollution. Traditional stormwater management was a simple civil engineering problem, “How can we get the water off site and into the river the fastest?” This greatly increased peak flows in the river bed, provided good transport for silt, sand, and garbage to float down storm sewers into the river, and decreased the amount of water that found it’s way back into the groundwater table.
The regulations require anyone building on a site to ensure that the peak runoff of stormwater after developement is no more than the peak prior to developement. Rainwater runs off roofs and parking lots much faster than through vegetation. Many new residential subdivisions handle this by putting in a pond to catch all rainwater and let it out slowly through a small pipe. Wal-Marts don’t have room for a pond, so they build an underwater holding area for the water. This is done with huge plastic, concrete, or corrugated metal pipes that immediately collect all surface runoff. The pipes then let out water through a smaller pipe at a more controlled rate.