Trialled on a cutting stabilisation project on the Jubilee line near Kingsbury, north West London some 99 per cent of the waste was diverted from landfill to be re-used or recycled.
At the site a cutting degradation was slowly leading to a threat of landslips onto the track. Tube Lines needed to reprofile the slope and fill a trench behind gabions with Class 6C fill to improve drainage and protect the site.
Such stabilisation work is nothing new, but Tube Lines made it different by working with the National Industrial Symbiosis Programme (NISP), a scheme to help companies maximise use of resources, divert waste from landfill and improve efficiency.
Because of the reprofiling of the cutting large quantities of material needed to be removed from the site – a total of 4,150 tonnes. NISP helped Tube Lines find alternatives to landfill. 380 tonnes of vegetation was sent for chipping. 1,900 tonnes of soil and clay was re-used as capping material elsewhere. 100 tonnes of concrete and rubble was crushed for re-use as aggregate.
Tube Lines obtained a waste management licence exemption from the Environment Agency to enable it to send a further 1,800 tonnes of fill material to another Tube Lines project for re-use. In the future Tube Lines is looking into introducing an excess materials listing which would effectively offer NISP’s matchmaking services around the company.
The team also cleared the trackside area of rubbish and sorted it for recycling and the site was finished with reprocessed topsoil and logs, which were retained to preserve a natural wildlife habitat.
Tube Lines is incorporating the zero waste to landfill methodology on other projects including one at Hounslow, where material excavated from a cutting regrading will be used in gabions and it is now sharing its improved process with suppliers, with Dean and Dyball trying it out at two sites.
The environmental benefits of finding alternatives to landfill are clear, with NISP calculating a carbon saving of at least 47 tonnes. There are also financial benefits – roughly £24,000 at Kingsbury. With landfill tax at £24/ tonne and rising, such savings can only increase. Using recycled materials led to further green bonuses and more cost-saving results as well as supporting the durability of the market in recycled materials.