Viridor Waste Management’s Beddington Landfill Site in Croydon, South London, is crossed by a “Main Effluent Carrier” (MEC) a 4m wide concrete channel carrying treated sewage effluent to the nearby River Wandle. In storm conditions this channel overflows to holding lakes within Viridor’s site via an Overflow Channel. It was necessary to replace the existing 1987 channel by 2012 with one realigned to the north, in order to release space for landfill cell development.

For economy and aesthetic reasons, Peter Baxter Associates selected a lining system that comprised a plastic web pinned to the subsoil and lined with screened gravel from on site deposits, as a watertight channel was not required. Dry lean concrete was used to line the web in zones where high erosion was predicted. A road crossing was constructed from precast culverts. During the site investigation, a large diameter gas main was discovered metres from its recorded position, requiring a partial redesign of the alignment. This channel will remain in legacy use as part of a landscaped park and is expected to provide a low maintenance and attractive facility for many years.

Peter Baxter Associates prepared the tender documents to NEC Option B, acted as Project Manager and CDM Coordinator, and supervised and tested the works. The project was completed in February 2012 after 10 weeks construction and has coped well with the exceptionally wet conditions since.

Channel excavation through in situ gravel

Recently ompleted channel and road crossing