As part of a multi-million pound ‘Phase III’ development and extension of Prologis RFI Daventry International Rail Freight Terminal (DIRFT), 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 meant ensuring that the site complies 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.
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 were of particular importance.
The project site was broken down into two plots.
The first of involved the installation of 500m3 of GEOlight® storage tanks, together with two SDS Aqua-Swirl™ AS-4 hydro dynamic vortex separators with the ability to cleanse the water at a rate of 91 litres p/s.
A second set of tanks, with a combined storage capacity of 1,000m3, was installed a few days later, including 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 p/s respectively.
The SDS Aqua-Swirl™ separators are designed to remove more than 80% of the total pollutants in the surface water runoff volume. Models AS-2, AS-3 and AS-4 each possess oil/debris and sediment storage capacities of 140 litres and 0.28m3, 416 litres and 0.57m3, and 719 litres and 0.91m3 respectively.
The SDS GEOlight® geo-cellular attenuation tanks on this site have the combined capacity to store up to 1,500m3 of water that has already been treated.
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 and to 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 has to date only included mitigation indices for vegetative SuDS; no figures exist for engineered systems hence the work undertaken for this project sets a landmark for this much needed development.
Wayne Llewellyn, Principal Engineering Co-ordinator, RPS Planning & Development: “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.”