A VARIETY of geosynthetics have been used to seal a landfill site used for the disposal of animals slaughtered in the UK's recent outbreak of foot and mouth disease.
The Hespin Wood Landfill near Rockcliffe, Cumbria, operated by Cumbria Waste Management, was used heavily during the crisis, first for disposal of carcasses and more recently as a repository for pyre ash. At the height of the epidemic Hespin Wood took up to 1,500t of carcasses a day.
A number of problems are associated with such disposal, including large settlement and bloated carcasses floating to the surface. To overcome these problems Cumbria Waste Management developed a capping system using two layers of compacted waste reinforced with a layer of Tensar SS20 geogrid between them. This was placed over the carcasses and finished with a 1m thick layer of compacted clay.
Hespin Wood is a land raise site and the disposal operation unsettled the hydraulic balance within the waste, leading to leachate breakouts on the side slopes of the landfill. GSE Lining Technology was brought in to come up with a design and build solution.
As the side slopes at Hespin Wood are steep, a product with good friction characteristics was needed. GSE chose a Terram drain to contain the landfill as the egg box structure provided a higher strength core than other similar products.
This system also provided a good flow paths for the upward migration of landfill gas into a sealed gas trench and for leachate running down into the leachate drainage system.
The adjoining edges of the 4m wide Terram drain sheets were joined with 1. 25m wide geosynthetic clay liners in rolls 4m long, provided by Cetco, GSE's partner in Europe for geosynthetic clay liner supply. The high friction surface of the Terram drain also helped with the placement of 0. 5m compacted clay, which provided the final layer to the system. Capping was completed in August.