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BPDA has just published a newly revised version of the precast concrete drainage sector’s “complete technical design guide”. Since our last issue of the guide, a number of standards, design methodologies and guidance documents were published. Moreover, feedback and enquiries we received over the last two years made us think about how to expand the content to address new areas. Here is a summary of the new sections we added to the precast drainage technical guide:


Chemical ground condition and the concrete exposure class

We added some information about the design life of precast drainage products and how a 100+ years can be achieved by using a DC-4 ‘Design Chemical’ exposure class. Our Technical Guide never used to refer to this in the past as we thought, at the time, that standards and guidance documents such as BS 8500, BRE’s Special Digest SD-1 and ‘Sewers for Adoption’ should offer sufficient guidance on this. However, as concrete drainage products with lower exposure classes exist in the UK market, we felt it is important to explain how the exposure classes and chemical ground conditions affect the intended working life of concrete products. This new information can be found in the Guide’s ‘Forward’.


Pipelines’ hydraulic design

More information was added to this section as European Standard EN 16933-2 now supersedes EN 752 on hydraulic design of drains and sewers. Terms associated with SuDS and oversizing for surface water drainage were also added.


Pipelines structural design

All pipeline design load tables have been amended to account for loadings aligned to the Eurocodes. The cover depths included in these tables have also been expanded to include covers as low as 0.6m, and as deep as 10m. The ‘light road’ loading category has also been removed.


Box Culverts design

A new section was included on the structural design of box culverts in accordance to Eurocodes, which superseded the now withdrawn BS 5400 on bridge design a few years ago. There is also a more detailed section on the hydraulic design of box culverts with examples and guidance adapted from CIRIA’s Culvert Design and Operation Guide.


Installation of precast drainage products

More information on innovative pipeline lifting and installation solutions (such as the pipe lifter) was added. A section on the installation of box culverts was added too.


Future revisions?

It is understood that BS 9295 is undergoing a major revision which will affect options associated with the structural design of concrete pipeline systems. We do not think it will invalidate the content of this new version, but additional options associated with design (e.g. limit state design), trench width and bedding factors will need to be introduced.

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