Repurposing Dredged Canal Sediment for Topsoil at Bowling, Scotland

Abstract

The aim of the SURICATES (Sediment Uses as Resources in Circular And Territorial EconomieS) Project is to increase sediment reuse for erosion and flood protection. To investigate potential opportunities to reuse dredged sediments as topsoil following phyto-conditioning, a pilot scale operation was undertaken at Bowling, Scotland. As part of normal maintenance, 550 m3 of wet sediment was removed from the Forth and Clyde Canal at Old Kilpatrick by Scottish Canals using a hydraulic excavator during September 2020, transported by barge, then transferred to a dewatering cell constructed in an old canal basin by lining with a geotextile break-layer and installing engineered drainage. Following initial dewatering, the sediment was sown with three varieties of grass, which each germinated and survived the winter. By March 2021 composite soil samples already met the BS 3882:2015 criteria for topsoil, other than for Zn levels, which reflected the locally elevated baseline values. This allowed the conditioned sediment to be used immediately as topsoil as part of the nearby construction of a long-distance cycle track following an old railway embankment. Following reuse, replicated validations of six grass or wildflower seed mixtures were sown in April 2021 and monitored to verify longer-term suitability as a landscaping soil.