Exposed Storm Drain Pipe Material

[CivilEngineerLady]

Hello All,

I am working on a project where we will be installing area drains below a "floating" wood deck. The team has suggested that we avoid burying the storm drain line, which would avoid the need for excavation on a steep hillside with many existing, large diameter trees and retaining walls.

If the drain pipe is to be fully exposed, what material would be required and would additional anchoring/protection be needed?

The site is located in the bay area of California.

Thanks!

 

[CivilEngineerLady]

Anything?!

 

[CarlB]

I'd suggested HDPE, with fused joints. It should be sufficiently durable, and UV-resistant.
Yes anchoring is required, since on a steep hill, and to resist external & internal loads.
This chapter from design manual may be helpful:

https://plasticpipe.org/common/Uplo...8 - Above-Ground Applications for PE Pipe.pdf

 

[CivilEngineerLady]

Thanks for your feedback. My boss had mentioned that Caltrans uses CMP (corrugated metal) potentially for exposed storm drain pipe. Could that be used? I couldn’t find a reference for exposed storm drain pipes in the Caltrans standard specs.

 

[FacEngrPE]

Either CMP or HDPE should have a service life longer than the wood deck.
CarlB indicates fused HDPE is a good choice. I have some experience with HDPE as pressure pipe that is not buried. In that application it is highly damage resistant, which I would not expect from CMP.

 

[CivilEngineerLady]

My boss thinks corrugated CMP is the way to go. Why would CMP not be durable?

 

[CarlB]

Suitability of pipe material depends on the specifics. You haven't mentioned pipe size, length, hill steepness, flow, etc. How will pipe be anchored? At steep pipe slope, could be high water velocities. CMP may be fin, if well anchored. Is CMP aluminum, galvanized, or aluminized?
You mentioned obstacles. Advantage of HDPE is it can be more easily routed in a meandering fashion. And no concern for joints separating, as for CMP. If pipe tends to shift due to thermal dimensional change, etc, coating on CMP can be abraded.