Following the publication of PPS 25 in May 2006, surface water disposal on all sites is becoming a key issue with Planning Departments. The Environment Agency are stipulating ever tighter controls on rainwater runoff and are enforcing their requirements through the planning system.
If seen as a strategic site for flood risk reduction some urban and previously developed area may now even require that the rainwater runoff is reduced to the equivalent of greenfield rates. This can have a dramatic effect on the site layout with space required for sustainable urban drainage systems (SUDS).
We can offer early advice and expertise for planning to maximise a sites potential utilizing an often complex combination of systems including storage ponds, infiltration devices, swales, green roofs, permeable paving to achieve the reduced flow rates.
If SUDS are not necessary we will discuss the proposals with the local drainage utility provider to obtain advice on likely connection points and restrictions on the capacity of existing systems.
We then use either the sophisticated Microdrainage software or a more simple spreadsheet analysis (depending on the site) to design and to optimize the on site infrastructure and to model surcharge conditions under various storm conditions and outfall flow rates.
We are able to arrange for infiltration tests to design soakaway systems and where appropriate rainwater harvesting of the roof runoff can be incorporated into the building services design.