Underground Storage for Detention

[mes11]

Have a project where we will have a small amount of underground storage serving as part of our detention system. It will be 5 runs of 18" diameter pipe (double wall w/ corrugated exterior and smooth interior) and each run is 200 feet long. Looking at the how the manifolds were constructed, they used heated fusion to create the tees and have straps that overlap the pipe and fittings. My question is how well do these fittings and fused seams hold up under pavement.

 

[Twinkie]

What kind of cover are you looking at? But I've never had any problems with these type of manifolds. We band pieces of plastic pipe together in the field all the time as well.

 

[beej67]

Fittings and seams hold up fine wherever they're at, in my experience, as long as you meet a minimum cover. However, the operational service life of CMP is probably not much over 20 years if you're storing water in it like that. Something to think about with your client. Also, 18 inch pipe isn't the best pipe to store in, because you can't get inside it to clean it. If you have the available freeboard, consider going with a larger pipe. It will save you money too, when you price the volume comparison.

If you're stuck with 18", I'd say take a hard look at HDPE instead, for corrosion reasons.

Hydrology, Drainage Analysis, Flood Studies, and Complex Stormwater Litigation for Atlanta and the South East -

http://www.campbellcivil.com

 

[jgailla]

+1 to everything beej67 said. I would consider concrete vaults or the proprietary storage systems (usually HDPE).

 

[beej67]

If you can get at least 48" or larger pipe, then aluminized or bituminous coated CMP might work fine for a 20 year span, but write the client up an ops and maintenance plan that makes it clear that it needs to be inspected yearly, and will probably need to be slip lined or similar in two decades before the invert rots out.

I've finally got a few projects where we're speccing the Stormtech system from ADS. It's slick, just not always cost effective. Probably beats a manifold made only of 18 inch pipe though.

Hydrology, Drainage Analysis, Flood Studies, and Complex Stormwater Litigation for Atlanta and the South East -

http://www.campbellcivil.com

 

[mes11]

I've got a pretty limited depth for this system. 12" of cover and then my pavement section. We are using HDPE for the material.

 

[kckcei]

Try ExFilt found at

http://www.kceso.com

...

 

[jgailla]

If there is only 12" of cover, you should seriously consider using concrete instead of HDPE.

 

[brandonbw]

beej67: What size pipe are you using from Stormtech?

B+W Engineering and Design
Los Angeles Civil Engineer and Structural Engineer

http://bwengr.com

 

[beej67]

By "pipe" do you mean "chamber?"

Biggest one I can fit given the cover constraints and fall, if it's primary objective is storage, because the biggest ones are the most cost efficient. If the primary objective is infiltration, then I back-figure the required planimetric area of infiltration bed to match the required first flush drawdown time, which is a function of site soil permeability, and I do some cost optimization about how best to cover that area with chambers. For systems that provide both functions, I do a bit of both.

I don't use the system exclusively. There's at least a dozen similar products out there.

Hydrology, Drainage Analysis, Flood Studies, and Complex Stormwater Litigation for Atlanta and the South East -

http://www.campbellcivil.com

 

[brandonbw]

I was thinking of the wrong thing. I thought it was Stormtech who we recently got a bid from. It seems like every competing company has a variation of water and tech in their name.

B+W Engineering and Design
Los Angeles Civil Engineer and Structural Engineer

http://bwengr.com