Using Constructed Wetlands to Mitigate the Impact of ... · Using Constructed Wetlands to Mitigate...

Using Constructed Wetlands to Mitigate the

Impact of Diffuse Urban Pollution in the Salmons

Brook and Moore Brook Catchments

Wednesday 18th July 2018

ian.russell@enfield.gov.uk

rosie.nelson@thames21.org.uk

Moore Brook catchment

•Area ~ 350 hectares

•8,000 residential properties

•300 misconnected properties

rectified since 2012

Pymmes Park Lake – major pollution events in November 2012 and March 2013

Pymmes Park Wetlands

•Total area ~ 5,000m2

•Wetland area ~ 2,000m2

•Volunteer planting in May 2015 organised by

Thames21

•600m2 of pre-planted coir mats installed in 2

days

May 2015

August 2015

Pymmes Park Wetlands

•Spoil used to create one new 11-aside football pitch and significantly improve a second existing pitch

•Area of 10,0000m2 raised by 0.7m

Pre-scheme During works

Firs Farm Playing Fields 21 hectares, 12 football pitches and 1 rugby pitch

Firs Farm Wetlands 30,000m3 flood storage, 2.4ha habitat enhancements including 4,000m2 wetlands, 600m long cycleway

Firs Farm Wetlands

•Wetland area ~ 4,000m2

•Volunteer planting in September 2015 organised by Thames21

•720m2 of pre-planted coir mats installed in 2 days

•Trees and shrubs planted in Autumn 2015

During construction (July 2015)

Following completion (June 2016)

Constructed Wetlands Slow the Flow

1. Glenbrook SuDS – 2014

2. Grovelands Park SuDS – 2014

3. Pymmes Park Wetlands – 2015

4. Firs Farm Wetlands – 2015

5. Bury Lodge Wetlands – 2016

6. Prince of Wales Wetlands – 2017

7. Broomfield Park Wetlands – 2018

8. Enfield Town Wetlands – 2018

1

6

7

52

3

4

Glenbrook SuDS

Bury Lodge Wetlands

Grovelands Park SuDS

8

Community Modelling

‘A way for local people to access the tools used by

scientists and authorities to manage environmental

problems’ Oxford University

Catchment

INCA – model

• Land use (Spatial)

• Weather – rainfall, temperature

• River Map/Network

Calibration

• Water quality readings – EA, Thames21

• Implementing constructed wetlands using observed field data

• Misconnections are assumed as effluent discharge

Constructed wetlands

Firs Farm – Ammonium DO%

Community Engagement

Potential Sites

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

Period Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

mg/l

Ammonium

Simulated Scenario Good

28% reduction of ammonium if 16 wetlands across the catchment were created.

Water Quality Improvements – Catchment

Scale, Pymmes Brook