The Stormwater Blog 

Contech Stormwater experts discuss designing stormwater BMP’s, regulations, maintenance issues, and all things stormwater.

6 Corrugated Metal Pipe Detention Design Questions

For the majority of applications, corrugated metal pipe (CMP) is the “go to” material for subsurface infiltration. This in turn, leads to a lot of design questions. Below is a list of six questions and answers we received from a recent webinar on designing CMP detention systems.

1.  What are the design considerations for construction beneath buildings and material sorting areas?

Generally, detention systems are designed to be under some sort of flexible pavement / rigid pavement, and Contech prefers not to install them under buildings. However, if a system is to be built under a building, all live load and dead loading will have to be accounted for. This may increase the gage and backfill material of the system. Special attention must be given to the zone of influence of the foundation, and access for maintenance must also be addressed.  These projects should be evaluated on a project by project basis.   

2.  Can you use CMP detention systems in high water table environments?  How do you counter buoyancy in high water table environments?

Yes, CMP detention systems can be used in high water table environments. Tiedowns and special backfill may be recommended to counteract buoyancy issues.

 3.  Is pipe cover normally measured from bottom of asphalt section or to bottom of entire pavement section (i.e. bottom of rock subbase).

CMP pipe cover is measured from the bottom of flexible pavement (i.e.: asphalt) or the top of rigid pavement (i.e.: concrete.)

 4. What is best, a single manifold system or a double manifold system?

It depends on site conditions and what is needed. Each has their benefits, but having a single manifold is more cost effective as it reduces the amount of fabrication needed and can make installation easier, by not having the concern of having the pipe barrels to match up perfectly on both manifolds.

5.  What is the preference for the location of risers - on the edge of the storage pipe or in the center and why?

The only limitation on riser placement is that they cannot be placed on welded seams. Other than that the riser locations are up to the EOR.

6.  Can CMP detention systems be used in coastal environments?

CMP detention systems can be made with different materials and coatings to accommodate different environments and service life requirements. Galvanized steel, Aluminized Steel Type 2, aluminum, asphalt coated and polymer coated options are available for different applications.  For coastal environments we usually recommend CMP pipe made from aluminum because of the potential of salt water and/or more harsh soils. Giving the geotechnical report to your local representative can help you choose the right one for your specific project.


Author Biography

Gabe has been the Detention Product Manager for Contech Engineered Solutions since February of 2014.  Prior to Contech, he worked at Tensar North American Green where he held a multitude of positions.  He was also the Director of Engineering at Armortec, which was acquired by Contech.

Gabe holds a degree in Civil Engineering from the University of Kentucky and he also has a Master’s in Business Administration from the University of Louisville.  He has served on multiple industry committees such as ASTM.  His professional experience ranges from new product development, commercialization, marketing and sales.  Gabe can be contacted at

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# Anonymous User
Friday, January 13, 2017 10:00 AM
Another question. Are (What) special measures needed to deal with acid mine drainage?
# David Corr
Friday, January 13, 2017 11:33 AM
Thanks for the question. Contech offers various coatings and materials to meet specific needs for a project. Additional information would be needed as all projects should be evaluated on a project by project basis. You may find our CMP Design Guide helpful; you can download a copy at

Contech also offers a Steel Reinforced Polyethylene (SRPE) product called DuroMaxx which performs in a wider range of environmental conditions as compared to CMP, and which may be an option for your application. Info on DuroMaxx can be found at We also have local Stormwater Consultants that can work with you to provide specific recommendations for project applications. Just send you contact info to info@conteches and we will have someone contact you.

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