LE 08

Minimising watercourse pollution – Green roofs - KBCN1026

Rain that falls onto the surface of green roofs can contribute to this requirement. Evidence,however, still needs to demonstrate that the 5mm rainfall from all impermeable surfaces on-site is being dealt with.

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Surface water run-off – discharge to a tidal estuary or the sea - KBCN1023

The peak rate of run-off and volume run-off criteria can be deemed to be met if the site discharges rainwater directly to a tidal estuary or the sea. The site run-off must discharge directly into the tidal estuary or the sea. Typically, drainage pipes would only carry run-off from the site and would not need to cross privately owned land outside the boundary of the development before reaching the sea. A definition of tidal estuary is in the technical manual.

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Surface water run-off – Highways and impermeable areas - KBCN1035

Where new non-adoptable highways are built, all new impermeable surfaces must be included in the calculations to demonstrate compliance with the peak rate of run-off and volume of run-off criteria. Where buildings are built beside existing highways or where adoptable highways are built, the impermeable area of the highway does not need to be included in the calculations.

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