Surface water provides unique challenges on many construction sites. When flat, impermeable materials are used in and around buildings, there is less space for natural infiltration, and excess surface water must be smartly managed to avoid flooding and pollution. With these challenges come the need for specialist engineer involvement at all stages of a project especially at the pre-planning stage.
In a large number of our own projects, we’ve been able to factor sustainable drainage systems (SuDS) into complex building sites from the very beginning of the design stage. These drainage systems ensure surface water is managed in a controlled matter and directed to where it won’t negatively impact both the client and the surrounding environment.
How it works
SuDS use a sequence of techniques that together form a management train. As surface water flows through the system, flow velocity is controlled and pollutants are removed. The management train may include the following stages: source control; pre-treatment; retention; infiltration. This sequence can also change the properties of the surface water flowing through it, such as removing its harmful pollutants, and this makes SuDS a good choice for those wishing to reuse the water for other purposes.
SuDS differ from traditional drainage methods by offering more opportunities to reuse and redirect water for the greater benefit of the environment. By mimicking the natural process of water flow, as opposed to directing water to nearby drains, SuDS go further in creating an infrastructure that harmonises with the wider environment.
If you want your project to benefit from SuDS, then it’s important to incorporate this into your plans from the very beginning. At the initial design stages of a project, we employ 3D modelling to examine the below ground drainage challenges and considerations of the development. From then on, various enquiries are made into the feasibility of installation, including capacity checks, drainage strategies and the presence of foul and surface water pumping stations.
In all of the projects we work on, we recognise the opportunities that SuDS based solutions can provide. By tailoring our designs to the unique needs of the development at hand, and effectively communicating these opportunities to clients using 3D modelling as a visual aid, we have encouraged many of our clients to opt for SuDS based solutions as this complies with the regulatory and legislative frameworks within our industry. One example of this is our work at Child’s Terrace, where installing water butts allowed residents to reuse rainwater for gardening purposes, and an attenuation tank was designed to mitigate the peak storm event plus an allowance for climate change.
Meeting sustainability goals
As suggested by the name, SuDS can go far in helping the building sector achieve its sustainability goals. One example of this approach in our work is on our project at Harris Academy Purley. On this development, our work to design an infiltration system that discharged surface water from the site to the water table contributed towards our achievement in earning an ‘Excellent’ BREEAM rating. This example demonstrates just how effective reusing, reducing and recycling can be, even in construction!
Other ways to reuse water using SuDS include channelling the flow to the wider environment. By doing so, engineers can help boost biodiversity in these areas, which can in turn lead to further environmental benefits. Clients could also opt to reuse this water in other features, such as to water in a nearby lawn, minimising the need for sprinklers and cutting down on energy use.
These growing concerns about the environment and urbanisation have meant that SuDS based solutions are becoming increasingly important and within the last 10 years this has been noticed with an industry shift towards increased regulations and legislation around the use of SuDS. In cities especially, space is a hot commodity and more recognition should be given to the works undertaken below ground to ensure water is managed safely and effectively.