SuDS in London - a guide
sustainable-urban-drainage-november-2016
sustainable-urban-drainage-november-2016
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5.15 Firs Farm Wetlands<br />
Location<br />
W<strong>in</strong>chmore Hill<br />
<strong>London</strong> Borough of Enfield<br />
Extent<br />
0.48ha<br />
Cost<br />
£900,000 (total scheme)<br />
Date<br />
2016<br />
Credits<br />
Enfield Council<br />
Environment Agency<br />
Thames Water<br />
TfL<br />
Sustrans<br />
GLA<br />
Thames 21<br />
Friends of Firs Farm<br />
<strong>SuDS</strong> components<br />
Ponds and wetlands<br />
Summary<br />
Open space transformation with wetland<br />
habitats to improve water quality outflow.<br />
Project description<br />
The ma<strong>in</strong> driver for the wetland creation<br />
was Enfield Council’s desire to improve<br />
water quality <strong>in</strong> Pymmes Park Lake, where<br />
Moore Brook outfalls before enter<strong>in</strong>g<br />
Pymmes Brook. Moore Brook is a lost<br />
watercourse with<strong>in</strong> a surface water sewer.<br />
Firs Farm was identified as a space suitable<br />
for the creation of a wetland scheme. The<br />
watercourse was de-culverted and diverted<br />
to a series of open watercourses, wetlands<br />
and ponds to improve water quality.<br />
Objectives<br />
• Improve water quality alongside flood<br />
alleviation, habitat enhancement,<br />
community space provision<br />
and creat<strong>in</strong>g cycleway l<strong>in</strong>ks<br />
• Provide <strong>in</strong>tensive monitor<strong>in</strong>g programme<br />
to be carried out by Thames21/Enfield<br />
Council over next two to three years<br />
to determ<strong>in</strong>e the impact of wetlands<br />
on reduc<strong>in</strong>g diffuse urban pollution.<br />
This data will be used to optimise<br />
future management of the two sites<br />
Actions and results<br />
• Northern and southern branches of Moore<br />
Brook are diverted from their culverted<br />
courses to three comb<strong>in</strong>ed wetland cells<br />
• Cells channel the water for<br />
treatment through flow paths<br />
• A watercourse downstream connects<br />
to a fourth cell which is built as a pond,<br />
before cont<strong>in</strong>u<strong>in</strong>g downstream <strong>in</strong> an<br />
open channel to the orig<strong>in</strong>al culvert<br />
• Surface water is treated at the surface<br />
before re-enter<strong>in</strong>g the culvert downstream,<br />
improv<strong>in</strong>g the quality of the water<br />
which outfalls at Pymmes Park Lake<br />
• A further diversion to four more wetland<br />
cells at Pymmes Park upstream of<br />
the lake provides further treatment<br />
Benefits<br />
• Water quality improvements<br />
before discharge to river further<br />
down the catchment<br />
• A surface system allows for issues to be<br />
identified and easily dealt with due to the<br />
size and location of the <strong>SuDS</strong> elements<br />
105 5 Case studies
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