Smart CSO/SSO Storage Solutions: Your Top Questions from our recent National Webinar

The audience engagement at our recent Contech webinar titled “Smart CSO/SSO Storage Solutions: Designing Resilient Systems for Today’s Infrastructure” was fantastic, proving that as municipalities deal with increased contaminated runoff, stricter regulations, and aging infrastructure, the hunt for reliable wastewater storage is heating up. Our presentation included several key design considerations for Contech’s DuroMaxx® SRPE tanks, which lead to various insightful questions. Many of the questions reflected similar themes, so I thought it might be beneficial to share a few – and the answers behind them to help designers better understand how the DuroMaxx® steel reinforced PE technology performs.

Question: Have you ever provided DuroMaxx products for a vertical orientation, such as an alternate to precast concrete sewage pump wet wells? With or without ground surface traffic loading capacity?

Answer: Yes, vertical wetwells have been provided from DuroMaxx® SRPE pipe in many different diameters. Depending on size and depth, various backfill types may be used, including coarse sand, crushed stone, and stabilized material / CLSM. These structures typically include a reinforced HDPE bottom plate along with small diameter welded stubs located on the sides of the wetwell as needed. If the wetwell structure will experience direct traffic loads, we can assist with providing example details for a reinforced concrete top pad with a cover or hatch for access. Another option (non-traffic rated) includes using an oversized removable HDPE cap that slides over and around the top of the wetwell.

Question: Can your product be utilized as a substitute for RCP Class IV pipe? And at what diameter ranges are available?

Answer: DuroMaxx® SRPE pipe is available in diameters ranging from 30” up to 120” in size. Because the 80ksi high-yield galvanized steel ribs encapsulated in the wall of the pipe provide the structural integrity, the structural design methodology follows corrugated steel pipe design per AASHTO Section 12 LRFD (not thermoplastic design).  The maximum height-of-cover limits for DuroMaxx® pipe will meet or exceed the allowable cover of Class IV reinforced concrete pipe.  Also, it is important to note that the HOC values provided in the DuroMaxx® brochure are conservative – if you have an application, please reach out and we are happy to take a closer look.

Question: What type of foundation is needed for your system? 

Answer: The pipe bedding is typically 4” to 6” of loosely placed material shaped to fit the bottom of the pipe as shown in ASTM D-2321 (No.57 stone or similar is a common bedding material). Under the pipe bedding, it is important for any subsurface storage system to have a competent foundation – the subgrade should be well consolidated and stable to provide adequate uniform bearing capacity.  During excavation, any questionable subgrade should be evaluated by the EOR or project Geotech to ensure competent foundation with the goal of eliminating differential settlement over time.  

Question: What is the design life of these systems?

Answer: The design life of DuroMaxx® SRPE pipe in wastewater or storm sewer applications is expected to be 100 years or more. This is due to the high quality virgin stress-rated HDPE resin (cell class 345464C per ASTM D-3350), which has been proven for decades in other critical sanitary applications. 

Question: Does the pipe qualify for LEED credits?

Answer: DuroMaxx® SRPE has the potential to contribute to a variety of the U.S. Green Building Council’s LEED® (Leadership in Energy and Environmental Design) Green Building Rating System™ credits in the categories for sustainable sites, water efficiency, and materials and resources. The plastic portion of the pipe must meet ASTM specifications and may not utilize recycled content; however, DuroMaxx® pipe uses 35% less polyethylene resin than M294 or F2648 pipe, resulting in significantly less consumption of non-renewable gas and oil. The steel content of DuroMaxx® pipe (about 2/3 by weight) is 55% post-consumer recycled content.

Question: Have you seen these underground storage systems used at airports? Either commercial or general aviation airports?

Answer: Yes, DuroMaxx® SRPE has been successfully utilized at international and regional airports across the U.S. and abroad.  Subsurface storage applications include containment storage of glycol runoff for de-icing facilities and AFFF fire-fighting foam chemical runoff containment at aircraft hangars. Large diameter drainage conveyance and trenchless structural reline of deficient storm sewer infrastructure are also common uses at airports.

Question: Will a copy of the webinar be available for future viewing?

Answer: Webinar attendees received an email with a link to the on-demand webinar as well as a link to their PDH Certificate.  Additionally, Contech shares a library of various past webinars on the website here: www.conteches.com/knowledge-center/webinars