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Dense asphaltic concrete for Biffa landfill site

Hydraulic asphalt specialist Walo has marked its 10th anniversary of working on Westmill Landfill site for Biffa Waste Services by constructing the 10th cell at the site using dense asphaltic concrete (DAC).

According to Walo, use of DAC has been key to reuse of the sand and gravel quarry near Ware, Hertfordshire due to the site located on the chalk acquifer.

Walo has said that the DAC creates a robust landfill barrier lining system, which is impermeable to leachate and methane.

The lining system on the most recently constructed cell covers an area totalling 14,500m2 and is formed from a 300mm mineral attenuation layer, a 200mm sub-base material layer and a 60mm asphaltic binder layer, which is topped with an 80mm DAC layer and a mastic seal coat to the base, side slopes and bund areas.

The work involved hand placing of asphalt on 450m of intercell bund and the placing of asphalt by paver and winch on a 30m slope. Following completing of the lining works, a leachate collection and removal system was installed.

According to Walo, as well as protecting the groundwater, the DAC lining also allows sites with steep side walls to be used for landfill that would otherwise be dismissed at the feasibility stage.

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