Innovation Showcase | Stormtech does SuDS differently

StormTech arch-shaped SuDS attenuation chambers from Advanced Drainage Systems have been used on over 50,000 projects worldwide. New Eurocode modelling demonstrates they pass muster for projects in the UK and Europe too.

The StormTech underground SuDS attenuation system, that exploits the structural properties of the arch, is now being installed on construction projects in the UK. Recent installations include one at Barrhead Retail Park in Scotland, and one at the Panattoni logistics park in Derbyshire.

The heart of the system is its corrugated thermoplastic chambers which have an elliptical arch-shaped cross section.

This shapes the embedment around  the chambers into stone arches and  structural columns, transferring loads away from the chamber into the stiffer material surrounding the chambers so that they can be installed with both shallow and deep cover.

Designed for flexibility of layout, ease of installation and transportation, the StormTech system can also incorporate an integral means of removing surface runoff pollutants at no extra cost. This is easy to maintain and can remove the need for costly pre-treatment systems.

StormTech chambers are designed to codes and standards published by the American Association of State Highway & Transportation Officials and standards body ASTM International. To ease their acceptance in the UK and other European countries, ADS commissioned a study to model their performance under the
Eurocode design methodology.

ADS UK manager Stuart Crisp explains: “The US design philosophy is different to the Eurocode one. This study translates the US approach and shows with total certainty that the StormTech system performs under the Eurocode design models, when installed using our standard details.”

Testing scenarios

The seven different sizes of StormTech chamber were evaluated using a finite element analysis (FEA) model, which looked at limit state modes of failure as set out EN 1991-2 – Eurocode 1 – Actions on Structures - Part 2.

Some may be familiar with Ciria C737, which covers the design of thermoplastic crates for underground water attenuation, which also suggests Eurocode modelling as a means of demonstrating structural adequacy.

As per ISO/DIS 4982 which covers arch-shaped chambers, the FEA model was used to test the various chambers in the most demanding loading scenarios. At shallow depths, live traffic loads at the surface are most likely to cause failure. For maximum cover, the long-term loading of the backfill material must be considered.

Load models for four different stress and fatigue cases were applied, according to
EN 1991-2 with cover in accordance with the ADS StormTech Construction Guide. 

• Load case 1: minimum cover and Load Model 1 (subclause 7.2)
• Load case 2: maximum cover and Load Model 1 (subclause 7.3)
• Load case 3: minimum cover and Fatigue Load Model 3 (subclause 7.4)
• Load case 4: minimum cover and Load Model 1 with braking forces (subclause 7.5)

The modelling considers the shape of the arches and material properties.  The sections are injection moulded from a thermoplastic, which means that the long term performance of the material under loading must be taken into consideration.

Performance proven

The FEA modelling proved that all the StormTech chambers are structurally adequate for each of the load cases detailed above. For minimum cover situations, there is significant additional structural capacity. For maximum cover, more of the chambers’ capacity was used but they were still comfortably within their capacity.

Crisp hopes that these calculations will help engineers and contractors to make the case for using StormTech.

• Published in association with StormTech

Like what you've read? To receive New Civil Engineer's daily and weekly newsletters click here.