Surface Water Drainage Strategy – East Devon

In proving a Surface Water Drainage Strategy to the planning office when submitting a planning application, it makes clear how surface water drainage will be handled within the new development.

Surface water drainage will have to be carefully considered when the project involves large areas of impermeable surfaces.

In this instance an artificial sports pitch surface was to be renewed in and the opportunity was taken to check the adequacy of the surface water drainage on site.

SWEL undertook attenuation calculation in line with the relevant guidance, but were careful to estimate an appropriate attenuation value for the pitch surface.

The current pitch surface would seem to be impermeable but this would not have been the case when the pitch was first installed. By research the subject SWEL were able to determin that the pitch sand (which would be free draining) had becomh contaimanted with fine grained soils (clays etc.) that had reduced its permeability and thus increases run-off potentially.

These characteristics had no doubt developed over the life spane of the exist surface and so to specify draining based on the aged, low permeability surface would have been to over specify.

Instead an average value was used between that of a new surface and that of the surface as was observed.

Legacy Drainage Plan, were used to derive current state of drainage.

Pitch condition reports were used to derive condition of surfaces.

High Quality Legacy Plans helped to facilitate the writing of the report.

Surface Water Management Plan