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As part of a multi-million pound ‘Phase III’ development and extension of the Prologis RFI DIRFT road and rail freight distribution terminal, SDS was required to effect the fast and efficient removal of surface water from the site and to ensure its safe dispersal to natural water receptors.

This challenging project demonstrated adhering to new best practice guidelines for surface water quality treatment whilst offsetting the attributed pollution.


SDS had to ensure that the site complied with all current and anticipated future environmental regulations, through the prevention of surface water and groundwater pollution in accordance with the objectives of the Site Plan and the National Planning Policy Framework.

Of particular importance to this project was the ability to satisfy new best practice guidelines for surface water quality treatment and to offset the pollution indices that were attributed to Phase III’s development.


The project site was broken down into two plots, the first of which involved the installation of 500m³ of GEOlight® storage tanks, together with two SDS Aqua-Swirl™ AS-4 Hydrodynamic Vortex Separators, with the ability to cleanse the water at a rate of 91 litres per second.

A second set of tanks, with a combined storage capacity of 1,000m³, was installed a few days later and included a catch-pit manhole with a sump and connected to a Flow Control Device. This second plot also included both an SDS Aqua-Swirl™ AS-2 and SDS Aqua-Swirl™ AS-3 Separator, with water cleansing capacities of 31 and 51 litres per second respectively.

The SDS Aqua-Swirl™ separators are designed to remove more than 80% of the total pollutants in the surface water runoff volume.

The SDS GEOlight® geocellular attenuation tanks on this site have the combined capacity to store up to 1,500m³ of water that has already been treated.


The latest SuDS guidance requires planners to incorporate the management of the SuDS water quality devices into their designs. This can be facilitated by specifying manufactured devices upstream of vegetative devices so that proactive scheduled maintenance can be carried out quickly and easily.

SDS Aqua-Swirl™ has the capacity to limit the amount of silts and attached pollutants from building up in the upper layers of a wider SuDS system. It can also mitigate against the ability of pollutant bioaccumulations to remobilise in the event of a surge of water, such as after a torrential downpour.

SDS worked closely with the project’s appointed Civil and Structural Engineering Design and Environmental Consultancy, RPS Group, in order to assign representative pollution mitigation indices to the Aqua-Swirl™ products. National (CIRIA) SuDS guidance had previously only included mitigation indices for vegetative SuDS; no figures existed for engineered systems, hence the work undertaken for this project set a landmark for this much needed development.


million square feet Phase III development


sizes of SDS Aqua-Swirl™ separators


million litres' stormwater storage capacity of SDS Geolight® tanks

The ability to meet new best practice guidelines on the quality of surface water runoff was a primary objective of this project. We worked closely with SDS to understand how their stormwater treatment products can deliver suitable water quality improvements; this allowed us to illustrate that the ‘pollution hazard’ associated with the site was adequately mitigated by the specified treatment devices.

Wayne Llewellyn, Principal Engineering Co-ordinator, RPS Planning & Development

Download the full case study here

SDS Aqua-Swirl Vortex Separator

SDS Aqua-Swirl™

SDS Aqua-Swirl™ is a custom engineered, flow through water quality device that utilises hydrodynamic separation technology to maximise the removal of sediment, debris and free floating oil within surface water run off.

The treatment flow rate of the SDS Aqua-Swirl™ system is engineered to meet or exceed the local water quality treatment criteria and form and intrinsic part of the SuDS solution train.

When connected to a SDS SYMBiotIC™ system, SDS Aqua-Swirl™ provides real time data on a broad range of key operating factors such as pollutant loads and silt capture level.


Discover how the SDS portfolio can benefit your development and get in touch now.