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A Sustainable Approach To Surface Water Management


Description of Works
Thames Water advocated an approach to sustainable drainage systems (SuDS) that limits, as far as possible, the volume of and rate at which surface water enters the public sewer system.  By doing this, SuDS have the potential to play an important role in ensuring that the sewerage network has the capacity to cater for population growth and the effects of climate change.  

Working on behalf of a partnership between Thames Water, the London Borough of Hammersmith and Fulham and the Royal Borough of Kensington and Chelsea, FM Conway supported an innovative trial to retrofit SuDS in three streets in West London, providing the opportunity to measure the volume and flow of surface water through flow monitors that were installed at each street.

Services used on this project Civil Engineering
Delivering Innovation

In close partnership with Atkins and SEL Environmental, FM Conway trialled different systems over three streets in the two boroughs.  The first scheme at Mendora Road, Fulham saw FM Conway install a total of 3,600 Permavoid cells, developed by Polypipe, within a channel along one side of the road to create nearly 136 cbm of stormwater storage beneath the surface.  In a channel under the other side of the road, there was a layer of aggregate within the geotextile membrane that sits beneath the top surface of permeable paving blocks.

Larry Kyan, Senior Contracts Manager at FM Conway, explains: 
“The loss of green and soft landscaping along the edges of the road increased run off into the road gutters.  This in turn accelerated water flow in the case of heavy rain, to the point of overloading the combined sewers and road gullies.

“Polypipe’s Permavoid product essentially replicates the effects of the soft landscaping which has been lost.  It sits beneath permeable paving which we have installed under the side of the road and acts to slow down the rate at which water flows into the main sewer system.”

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FM Conway has risen to the challenge, especially when problems have needed to be addressed.

Ian Hawthorn - Head of Highways Maintenance and Projects for both the London Borough of Hammersmith and Fulham & the Royal Borough of Kensington and Chelsea

A similar approach was taken at Melina Road, Shepherd’s Bush, further north within the borough.  However, here the system was used in conjunction with soft landscaping.  2,345 Permavoid cells were used beneath rain gardens - areas of soft landscaping built into the edge of the road and pavement.  

Larry described the difference in the approach:
“At Melina Road the same system allows the new water ‘tanks’ to support plant growth above ground, bringing environmental benefits to residents and enhances the streetscape, as well as reintroducing areas of soft landscaping to reduce surface run-off.”

FM Conway completed the construction and installation of the SuDS at Arundel Gardens, Kensington.  Here, the SuDS was comprised of a shallow layer of attenuation crates within a geotextile membrane across the entire width of the road, under a final layer of porous asphalt.

The use of three different SuDS and the variety in their methods of construction and installation enables scientists on the project team to measure the effectiveness of each technique.

 

Outcomes

Dominic Kelly, Works Performance Manager - Transport and Highways at the London Borough of Hammersmith and Fulham, added:
 “We’ve been extremely pleased by the close partnership that has developed between our team and our partners, including Thames Water, Atkins, SEL Environmental and FM Conway.  The trial has required both technical expertise as well as recognition of the needs of residents, and in both cases the professionalism of the team has been exemplary.” 

Ian Hawthorn, Head of Highways Maintenance and Projects for both the London Borough of Hammersmith and Fulham and the Royal Borough of Kensington and Chelsea, commented: 
“This has been not just an incredible learning experience for everybody, but a way forward for future developments. We have tried various SUD measures across each of the three projects, testing what will work. It has increased all of our experience and we have certainly learned a lot of lessons. FM Conway has risen to the challenge, especially when problems have needed to be addressed.”