Surface & Foul Water Drainage Strategies

We actively work with architects, clients and design teams to ensure SuDS are considered as early as possible flagging up modifications to masterplan layouts as necessary to improve SuDS integration. We identify problems early and, in many instances, lead development design around the drainage system meaning the developer can harness significant saving later in a project.

We always consider the technicalities of infrastructure adoption, maintenance and utility reinforcement in our early drainage strategy design work ensuring our planning designs are non- abortive and provide a strong platform to prepare subsequent detailed design upon.

Surface Water Drainage Strategies

A surface water drainage strategy must demonstrate how a development site can manage surface water runoff onsite in a way which causes no greater flood risk to itself or the receiving catchment than the undeveloped site (the “greenfield site”).

In April 2015, Lead Local Flood Authorities (LLFA’s), were set up across the country tasked with managing and providing strategic direction to flooding issues. The LLFA are responsible for consenting drainage matters for development sites of 10 or more units or typically which generate 1000 sqm or more of impermeable area. As part of providing evidence to the LLFA a development can suitably mitigate flood risk, a drainage strategy must be prepared at the planning stage.

Under current planning guidance in England, Sustainable Urban Drainage Systems (SuDS) must be used for new developments opposed to traditional drainage systems incorporating pipes and closed storage system, unless it is inappropriate to do so.

Foul Water Drainage Strategies

A foul water drainage strategy must demonstrate how foul water effluent can satisfactorily be conveyed to either a public sewer or stored and treated offline.

Under Environment Agency guidance, a connection to the public sewer should always be the priority unless it can be demonstrated it would be unreasonable on cost or technical grounds to do so.

Typically, a foul water drainage strategy will identify how much effluent a development site will create, the preferred point of connection to the public sewer, whether there is capacity for this effluent at the point of connection and how effluent can be conveyed to the point of connection (can it gravitate or would it require pumping?)