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Information & Drainage Terms
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Combined sewer – A sewer designed to carry foul sewage and surface runoff in the same pipe.
Consent – Permission (usually conditional) granted by the environmental regulator; usually associated with the discharge of flow, or potentially polluting flow, to a watercourse or into the ground.

Culvert – A closed conduit carrying a watercourse beneath an obstruction such as road, railway or canal.
Design storm – A synthetic rainfall event of a specific profile, intensity and period of time for a given duration and return period; derived by statistics and recorded rainfall events for a specific location.
Discharge consent – Permission to discharge surface water or effluent, subject to conditions laid down by an environmental regulator.
Flood and Water Management Act – Legislation to clarify the framework for managing flood risk (particularly surface water management) in England and Wales (Defra, 2010).
Foul drainage – The infrastructure that drains the water and sewage that is discharged from within houses.
Greywater – Waste water from showers and baths with water softener shower head installed, sinks (kitchen sinks are excluded due to high organic content), and domestic appliances before it reaches the sewer.
Groundwater – Water that is below the surface of ground in the saturation zone.
Highway drain – A conduit draining the highway on a highway maintainable at the public expense it is vested in the highway authority.
National Standards for Sustainable Drainage – Sometimes referred to as the National Standards. A regulatory document providing standards and guidance on the design, construction and maintenance of SuDS for approval and adoption by the SuDS approval body (in accordance with Schedule 3 of the Flood and Water Management Act, Defra 2010). (Only available in draft form)
Peak flow – The maximum volume of water flowing in a watercourse or sewer over a certain period of time following a rainfall event.
Sewers for Adoption – A guide agreed between sewerage undertakers and developers (through the Home Builders Federation) specifying the standards to which private sewers need to be constructed to facilitate adoption.
Surface water – Water from precipitation which has not seeped into the ground and which is discharged to the drainage system.

Drainage Terms
Call 0207 536 2778