Position statement on CIRIA C737

In the last position statement of June 2018, the BPF Pipes Group provided an update to the previous position statement on CIRIA C737. This update gives information on the real progress that has been made since.  

European Standards

We continue to be actively involved in the development of the European Standards. Substantial progress has been made. 

 A European Standard1 for installation practices was published in January 2018. Standards for short-term testingand long-term testing3, together with the product specification4 are now available.

A supporting standard covering attestation is under development by the CEN Working Group. 

These new standards support C737 by providing the standard test methodology which was not explicitly detailed in that document.  In addition the use of these standards means that all European product will be tested in the same way. This is a very clear move towards greater consistency of approach across Europe.

CIRIA C737

C737 provides a risk based method, based on Eurocodes, for calculating the geotechnical loads acting on a geocellular system in a particular situation. These vertical and lateral loads are then compared against the long term compressive strength (in both directions) of the geocellular system, determined according to the new standards. This then determines the suitability, or otherwise, for a particular geocellular system to be used in that situation. Additional ground improvements may be needed to make the system work in the more extreme installations.

It is worth noting that the geocellular system itself is not C737 compliant. It is the structural calculations that are carried out in accordance with C737.

Certification

We have worked closely with the British Board of Agrément (BBA) to determine a certification process in accordance with the requirements of C737. This process has been completed and a consistent approach is now available for manufacturers to work to. Manufacturers are currently working to complete the testing required to be able to apply for certification. This may take some time as the creep rupture testing covered by the European Standard requires a test period of at least 4,380 hours (6 months) – experience is that the full test programme will take significantly longer.

BBA Certification will demonstrate that the manufacturer has a robust quality plan, will verify that all testing has been carried out to the European Standards and confirm the short and long term compressive strength values to be compared with the loads from structural calculations, C737 or other engineering methodology. It will also provide sample calculations for an installation envelope within which the system can be used without needing further detailed calculations.

The BBA has confirmed that current certificates to the former CIRIA publication C680 will remain valid to their expiry date.

Practical guidance

To support the transition to C737, we have developed practical guidance targeted at designers and specifiers

 Footnotes:

CEN / TR 17179: 2018 “Thermoplastics piping and ducting systems - rainwater infiltration and storage/attenuation systems - Practices for underground installation” 

EN 17150:2019 “Plastics piping systems for non-pressure underground conveyance and storage of non-potable water - Test method for determination of short term compression strength of boxes” 

EN 17151:2019 “Plastics piping systems for non-pressure underground conveyance and storage of non-potable water - Test method for determination of long term compression strength of boxes” 

4 EN 17152-1:2019 “Plastics piping systems for non-pressure underground conveyance and storage of non-potable water — Boxes used for infiltration, attenuation and storage systems — Part 1: specifications for storm water boxes made of PP and PVC”

Guide to designing geocellular drainage systems to CIRIA report C737.