]> 2026-04-12T15:40:40+00:00 Case study:River Wandle: Silt & SuDs 500 en CRF009 Project Briefing Note - Wandle River Restoration.pdf CRF Project briefing note - Wandle Approved Reduce diffuse pollution Wandle Trust Environment Agency London Borough of Sutton Queen Mary University of London Thames Water Defra Great Britain Defra Catchment Restoration Fund Yes No Yes false No Challenges: *Identify spaces for DDs underground amongst utilities. *Each defender had to be custom made to match the angle of the various outfall pipes allowing them to integrate with the established system. *Getting commitment from parties to empty the DDs. 51.370685577392,-0.15960922837257 Bella Wandle Trust Davies Reduce diffuse pollution,,, ,,Community involvement, TH002 monitoring framework table.docx RRC Monitoring table - Wandle For wider project benefits as part of the larger "River Wandle Restoration Scheme" please see the parent project. Monitoring was completed for Mycofilters, Siltex, Smart Sponges and Downstream Defenders. Downstream Defenders: A Downstream Defender (DD) was monitored using upstream and downstream flow meters and water samples were taken using autosamplers during heavy rainfall events. Samples were sent to a UKAS accredited lab to be analysed, and contaminant load was calculated. The surface water pipe along which the DD was positioned had unexpectedly high flows (up to 50 l/s). When flows were within the operating range of the DD it was effective at removing around 47% of Total Suspended Solids (TSS), however, over the a whole data period it removed 9%. These numbers are within the range found by Dr Thomas Curwell, who investigated multiple rainfall events in DDs and found that they were effective in removing 9-49% TSS. Despite the low removal inefficiencies, the units remain the most effective measure if only a few square meters are available to SERT's knowledge, and are likely to have a cumulatively positive effect. The Trust are currently working on a sediment trap-wetland treatment train in an area where there is more space as an alternative method, following promising results from the scientific literature. Mycofilters: Upstream and downstream water samples were taken for Mycofilter sites and control sites (using straw bags with no oyster mushroom). Smart Sponges: The concentration of hydrocarbons collected in the gully pots with and without the sponges is being monitored. Siltex: Silt and water are being monitored. 12824 Environment Agency, London Borough of Sutton, Queen Mary University of London, Thames Water, Defra, Volunteers adding Siltex to Carshalton Ponds in November 2014. Please seek permission from the Wandle Trust to reuse this photograph. 2015-03-31Z 2457112.5 Siltex + Logo.png 2012-07-01Z 2456109.5 Complete This Project is part of a larger scheme with the overall aim of establishing a population of brown trout in the Carshalton arm of the River Wandle for the first time in over 80 years. For more background on this larger scheme, please refer to the parent project "River Wandle Restoration Project". The overall aim of this Project was to trial and evaluate innovative control measures for mitigation of urban diffuse pollution in an urban environment. The River Wandle turned black with road runoff every time it rained and whilst Environment Agency data did not detect a problem (due to spot sampling rather than continuous monitoring methods), the Trust suspected river sediments were contaminated and the first flush after rain caused fluctuating water quality, likely limiting the successful recruitment of trout. The Trust worked with an MSc student from Queen Mary University and confirmed that copper and 15 types of PAH were at a level that would have a severe effect on aquatic biota. To reduce urban diffuse pollution, five innovative measures were installed and trialled to determine their effectiveness for mitigation of urban diffuse pollution, particularly road runoff: To reduce urban diffuse pollution, five innovative measures were installed and trialled to determine their effectiveness for mitigation of urban diffuse pollution, particularly road runoff: 1. Rain Gardens installed to intercept surface water and aesthetically enhance an area in Hackbridge. 2. Downstream Defenders (DD) intercept surface water drains and remove sediment by centrifugal force. 3. Mycofilters are bags full of a substrate as a feedstock for the native oyster mushroom which accumulate toxins such as heavy metals from the passing water. A total of 180 mycofilters were made and grown by a team of volunteers, installed in 4 locations on the lower Wandle. 4. Siltex is a natural chalk-like substance which helps to increase the speed of silt breakdown by stimulating natural processes. Working with local volunteers, Siltex was added to Carshalton Ponds in November 2014 and samples taken for the proceeding months to determine the effectiveness. 5. Smart Sponges are a commercial product specially designed to absorb oils mixed in water. When placed in gully pots, Smart Sponges can permanently remove oils from the drainage system before they enter the rivers. A total of 23 Smart Sponges were installed in gully pots along the catchment of one surface water drain linking to a DD. River Wandle: Silt & SuDs river wandle: silt & suds No London Thames Wandle (Carshalton Branch at Carshalton) wandle (carshalton branch at carshalton) Community involvement 10 - 100 km² 160 100 - 200 m Wandle (Carshalton Branch at Carshalton) GB106039017640 Flood risk management Hydromorphology Social benefits Water quality Urban GB106039017640 Wandle (Carshalton Branch at Carshalton) 2014-04-17T14:38:03Z 2456765.1097569 2017-09-19T12:13:01Z 2458016.0090394 River Wandle: Silt & SuDs 500 1 plainlist 5 [[Category:Case study]] [[Project title::!River Wandle: Silt & SuDs]] [[Subcatchment title::Wandle (Carshalton Branch at Carshalton)]] River Wandle: Silt & SuDs# QUERY4c216fe8a86ce74116f09c3a24faed9a Case study:Wandle River Restoration Project 500 en Wandle River Restoration Project REDI 102 en REDI