Exploring Alternatives to Reinforced Box Culverts for Large Storm Sewer Systems

When it comes to designing extensive storm sewer conveyance systems, engineers and agencies are constantly seeking innovative alternatives to traditional reinforced box culverts. Contech, a leading player in drainage and stormwater, has been at the forefront of exploring efficient and effective solutions for moving stormwater across the country. While concrete has been the default choice for larger systems, there's a compelling alternative worth considering – Smooth Cor™.

Smooth Cor™ double wall is a game-changer in the realm of stormwater management. It's a corrugated metal pipe (CMP) product that boasts hydraulic efficiency (with a Manning's "n" value of 0.012) while combining the strength of a corrugated outer shell, a smooth steel liner, and the durability of a polymer coating. This unique combination not only ensures robustness but also offers a cost-effective and installation-friendly substitute to concrete box culverts, spanning sizes from 3’ x 3’ to 7’ x 7’ or larger.

One of the standout advantages of Smooth Cor™ is its superior strength-to-weight ratio. Compared to concrete, steel allows for longer lengths (up to 25’) at significantly lower weights. For instance, while a small 3’ x 3’ concrete box can weigh up to 1,120 lbs/ft, a 42” Smooth Cor™ weighs merely 60 lbs/ft. This translates to quicker and more economical installations, with longer lay lengths and reduced weight contributing to cost savings.

A real-world example from Alabama underscores the benefits of opting for Smooth Cor™. In a project aimed at connecting two properties over an existing gorge, initial plans centered around a 7’ x 4’ reinforced concrete box (RCB). However, after careful evaluation, a 72” Smooth Cor™ double wall was chosen due to its faster delivery, shorter project timeline, equivalent hydraulic capacity, extended durability, and ease of installation, among other factors. Notably, the CMP solution outperformed concrete despite being designed to withstand railroad loading.

Furthermore, CMP storm sewer systems offer significant advantages over concrete alternatives when it comes to inline fittings. A project at an air force base in Georgia required over 8,000 LF of pipe with numerous inline fittings. Unlike the challenges posed by concrete, CMP allows for inline fittings to be seamlessly incorporated into the pipe, simplifying installation, and saving both time and money without compromising hydraulic capacity or durability.

In conclusion, the realm of large storm sewer systems offers a range of choices, and not all products are created equal. Understanding the available options empowers decision-makers to select the most suitable solution for their needs. Contech stands ready to assist in navigating these options, ensuring that stormwater management projects are executed efficiently and effectively.