HDPE Detention Pond Riser

[406Eng]

Hey all,

The company that I presently work for (myself included) has designed a considerable number of moderate to large sized detention ponds. Since I started working for the company, it has been common practice for us to utilize CMP fabricated riser structures like the one shown in the photo below. During a recent project, a coworker and myself started discussing ways that we could revise our "standard" design & improve on the life/functionality of these systems. He proposed using HDPE pipe as an alternative to CMP, which makes sense as it will significantly extend the life of the riser. However, I have some concerns related to the functionality of using HDPE such as its sensitivity to UV radiation, and how one would assemble such a unit which can handle forces such as a cantilevered pipe extension or buoyant forces from the pond filling. These are issues that are not a concern when you weld CMP together.

Has anyone had experience with using HDPE in similar applications or have any insight on how this could be done?

Thanks in advance for any responses.

 

[LittleInch]

No photo attached....

You can get black HDPE or PE 100 which is UV resistant.

The issue with PE though is that it creeps over time when subjected to a reasonable level of stress, hence cantilevering anything is a risk.

And yes, it is slightly buoyant so you have that issue to look forward to.

CMP is Corrugated Metal Pipe?

The photo would help to know what we're looking at.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[406Eng]

Sorry, forgot to include the photo. The original post has been updated with the referenced photo.

 

[LittleInch]

Looks ideal for PE to me.

Just clamp your horizontal pipe down on that massive concrete block if you're worried about flotation.

Can't quite work out where the water is going, but should be easy to do for any decent PE fab shop.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[ACtrafficengr]

Around here, the whole thing would be precast, with an orifice at the elevation of the horizontal pipe, and a grate on top. Granted, that would not be cheaper, but would PVC, SICPP, etc., resist winter conditions?

My glass has a v/c ratio of 0.5

Maybe the tyranny of Murphy is the penalty for hubris. -

http://xkcd.com/319/

 

[406Eng]

Sorry, that photo does not do a ton of justice, below is a couple images that give a better perspective. My concern is not the pipe stub (the larger corrugated horizontal pipe), that corrugated pipe gets tied into and gets buried. The pipe that I am concerned w/ is the smaller smooth pipe...this would also be replaced w/ an HDPE pipe & it remains suspended.

 

[406Eng]

ACtrafficengr - We do utilize both cast-in-place & pre-cast structures for our extremely large ponds. However, for intermediate size ponds we have found that concrete is almost always cost prohibitive. Exposure to extreme cold is one of my concerns with using HDPE (we get exceptionally cold weather up here), however, I have consulted several manufacturers and they have indicated to me that the PE products we would likely use are okay to -40F.

 

[LittleInch]

At that length PE will be fine. I thought you meant 5m+...

Most on google do seem to be steel but a few are PE.

Some random people that make PE drain pipes etc -

https://www.varitech.com/high-density-polyethylene-manholes.html

At least one PE riser

http://civilenginphotos.blogspot.com/2011/05/65-detention-pond-riser.html

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[EdStainless]

The PE may handle -40, but how will it like freezing water?
If you go PE plan on making all of it a lot heavier.
And some form of reinforcement of gusseting may be called for.

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P.E. Metallurgy, consulting work welcomed

 

[bimr]

The problem with PE is that it will not be straight and bend over. The finished product won't look proper.

 

[cvg]

HDPE would not be allowed at the surface around here. in addition to creep during summer heat, it tends to burn. cmp is a better alternative and concrete is preferred