Hydraulic asphalt engineering firm Walo UK has started lining the 11th cell at Westmill landfill site in Hertfordshire using dense asphaltic concrete (DAC).
As the site is located on a chalk aquifer, it is a particularly challenging site. Once complete, the site operated by Biffa Waste Services will have an overall storage capacity of around 2.5 million cu m.
The area to be lined will use more than 13,000 tonnes of asphalt. The lining system was formulated in Walo’s Zurich laboratory to a design mix specific to this project.
It has a 300mm mineral attenuation layer, a 200mm sub-base material layer, a 60mm asphaltic binder layer, a 80mm DAC layer and a mastic seal coat to the base, side slopes and bund areas.
The asphalt is being placed by hand on the intercell bunds and by paver and winch on the base and slopes. Once the lining works are completed, a leachate collection and removal system will be installed.