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28Jul 2017
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The role of proprietary products in delivering treatment of surface water runoff as part of SuDS

 

When considering the treatment of surface water runoff as part of a SuDS design, the designer should always start by looking at the use of vegetative SuDS due to their multiple benefits. However, proprietary products are a useful extension to the SuDS “toolkit” and in many circumstances they can assist in delivering an appropriate design for mitigating pollution risks from the site.

 

The SuDS Manual accepts that proprietary products can play their part in delivering water quality design standards ‘where design performance is demonstrated’.   There are a number of standard testing codes of practice used by manufacturers – the New Jersey NJDEP (June 2017), the German DiBT , and (as from December 2016) a new British Water Code of Practice for Proprietary Product Testing.  The aim of the new British Water code is to give regulators, designers, specifiers and local authorities consistent information on product performance.  Naturally, scheme designers and manufacturers are now questioning how proprietary product test results should be interpreted alongside the pollution mitigation indices suggested by the SuDS Manual’s Simple Index Approach (SIA) for non-proprietary SuDS components.

 

The SIA approach, based on SuDS performance evidence, was not developed to specifically align with proprietary product test method results.  Therefore, although any data that demonstrates removal efficiencies for specified loads and flow rates will be very valuable in supporting claims of product performance and in providing reassurance to designers that the receiving environment will not be put at risk, there is no direct relationship that can be recommended at this time.

 

Keep an eye out for a longer briefing note on this issues coming soon.

 

If you are interested in discussing this further, please get in touch with Richard Kellagher or Bridget Woods Ballard at HR Wallingford.

  • Glyn Hyett

    Fascinating and most welcome. Designers are asking this question. I dont know why this is a HRW led issue and wonder what EA position is on this too,

    In our main EU market country of Germany, scientists in pollution control organisations continues to wrestle with the problem of how to compare the more easily proven performance of devices, which are testable and maintainable, with some vegetative systems where long term fate of key contaminants cannot be easily investigated in the field. With a device it is often very easy to go collect a sample.

    Is the methodology/framework/dataset used in UK by HRW/CIRIA for the green infrastructure SIAs externally available?
    Would this assessment framework give device manufacturers a starting point for discussions with designers?
    In Germany and elsewhere, monitoring long term performance of green SUDS has proven to be very time consuming and expensive, with much debate and opinion as to validity of such monitoring designs.
    The “road salt effect”, included as a test option in the BW Code and mandatory in Germany DiBT is it seems not usually assessed for swales and wetlands. Research has shown episodic releases of retained contamination on entry of sodium to constructed wetland systems for example (see Tromp et al, 2012).
    I am not sure designers always consider the fate of natural soils receiving significant (?) heavy metal loadings. Road side soils can develop very high metal loadings. I remember being told by SEPA that was fine, and such soils would need to be excavated and landfilled. It depends where we want our copper and zinc to end up I guess.
    In writing, i also have seen little evidence in UK of EA or others setting out requirements for on-going maintenance of devices. This is an issue that needs to be lanced and CIRIA might be well placed to form some type agreements, I may have missed that already having been done? .

    Finally, may I ask please
    1. if the “no direct relationship can be recommended at this time” a HRW comment, HRW policy or a CIRIA Suds Manual output?
    and
    2. Who is going to approve any new SIAs?

  • Gilles Rivard
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