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9.7 Water quality
Rainfall picks up pollution from development Open water features should not receive flows
surfaces. As runoff moves slowly through directly from development without sufficient
SuDS components most pollution is removed treatment.
through sedimentation, filtration and ■ Hydrocarbons remain in pond sediments Detailed Design
bioremediation. Naturally occurring
for extended periods.
processes in many SuDS components break
down organic pollution, meaning that there is ■ Silts which carry heavy metals impact on
no build up or need for removal of this the aquatic environment and add to
pollution over time. maintenance problems due to the build-
up of toxic sediments.
The NPPF sets an obligation on proposed
development to have no negative impact on The amenity and biodiversity value of ponds
the environment and encourages provisioning and wetlands should be protected with
opportunities for biodiversity and habitat pollutants removed at source and along the
creation, not just in the wider landscape, but management train.
within development.
Using source control and the management
train, SuDS delivers the requirements of NPPF Paragraphs 109, 117 and 118
NPPF by providing a controlled flow of clean
water through the development.
102
9.7.1 The objectives of designing for water quality
■ Treat runoff to prevent negative impacts ■ Manage surface water runoff at or close
to the development’s landscape and to source and at or near the surface
biodiversity as well as receiving where possible to begin treatment quickly
watercourses and water bodies within the and maximise treatment through the
wider landscape. system.
■ Design for interception losses to occur for Where water quantity design adopts a SuDS
most small rainfall events so that the most management train approach, as outlined in
polluted part of runoff is more effectively this document, water quality objectives are
held and treated on site. normally achieved by default, due to the
number of components already limited in
series.
London Borough of Bexley SuDS D & E Guide © 2018 McCloy Consulting & Robert Bray Associates
