Corrugated Metal Pipe (CMP) is the construction material of choice for underground stormwater detention and infiltration projects. With its low cost, a wide variety of pipe diameters up to 144”, layout configurations and pipe coatings, CMP offers engineers the flexibility to develop solutions that can be sized and shaped to meet site-specific needs. 

Even with all these advantages, there are still a few instances where alternate pipe materials, such as DuroMaxx Steel Reinforced Polyethylene (SRPE) may be a better solution.  DuroMaxx SRPE combines steel and polyethylene (PE) to make an exceptionally strong and durable pipe with diameters up to 120”. The two most common scenarios where DuroMaxx SRPE should be used is on sites where watertight storage is needed and sites with corrosive soils.

Watertight applications

There are several joint configurations available with DuroMaxx SRPE, including soil tight, high-performance bell and spigot, and a watertight joint using a welded coupler. Examples of underground detention systems that may need a watertight joint are below.

High Groundwater - Sites with high groundwater may need a watertight system to ensure groundwater does not infiltrate and displace the design storage volume. 

Rainwater Harvesting – If the collected runoff is to be used for rainwater harvesting, a watertight system is needed to ensure reliable long term storage. This case study from Allianz Field in Minnesota is an example of how SRPE was used to create rainwater harvesting cisterns providing 850,000 gallons of storage. 

Combined Sewer Overflow (CSO) – Many communities have combined sewers, making them susceptible to overflow during high-intensity rain events. Given the pathogens that can be present in CSO any leaks could contaminate groundwater, so the storage solution needs to be watertight, such as this example from the 10th St. Apartments in Chattanooga, Tennessee. 

Sites with corrosive soils

How would you describe corrosive soils, sometimes referred to as “hot soils? Corrosive soils have two main parameters:

Low or high pH range – outside the range of galvanized steel pH 6-10 and aluminized steel pH 5-9

Low resistivity - below galvanized steel range of 2,000 ohm-cm or aluminized steel res. below 1,500 ohm-cm 

Corrosive soils secondary parameters:

High sulfate concentrations

Other potential corrosive elements such as sanitary effluent, mine runoff, or toxic chemicals in the soils

The site's geotechnical report should contain information on subsurface soil conditions and identify if any of the above conditions are present.