A flood prevention scheme located near the West Sussex town of Crawley is nearing completion, with Mackley currently on-site to carry out the final phase of works.
The flood prevention works at Clay’s Lake are being carried out by Mackley working as part of Team Van Oord on behalf of the Environment Agency.
A key element of the project – the removal of an existing dam and its replacement with a larger dam to increase the lake’s capacity from 10,000 cubic meters to nearly 400,000 cubic meters – was completed in September 2017, shortly before a seasonal break in on-site activities.
Dan Burden, Mackley’s Site Manager, said: “Following construction of the embankment over the last two summer seasons, we mobilized for the final time in April 2018 to complete the works. The dam embankment was overbuilt towards the end of 2017 to allow for settlement, which was monitored throughout the shutdown.”
The grasscrete spillway, currently under construction, will provide scour protection to the downstream face of the dam embankment in the event of a one in a 1,000 year flood event. However, the dam is designed and constructed to withstand a one in 10,000 year ‘Probable Maximum Flood’.
“Following completion of the grasscrete spillway, the secondary concrete works will be installed along with fish brushes to the culvert – prior to installation of trash screens and platforms within the control structures,” added Dan Burden.
“Once the grasscrete is signed off, sacrificial fill and topsoil will be placed downstream of the works and the gabion retaining walls will be completed. Finally landscaping and seeding of the embankment and demobilization will be carried out in readiness for handover to the client in September 2018,’’ concluded Dan Burden.
The Clay’s Lake project forms part of the Upper Mole Flood Alleviation Scheme which was developed by the Environment Agency after floods in the Crawley area during 2000. When complete, the scheme will reduce the risk of flood to more than 280 homes in the area, and to Gatwick Airport.