The sides of the landfill were also raised and the landfill may operate until 2020. Sito Rakennuttajat functioned as the construction consult and project manager.
The narrow excavation was done with a machine that resembles a chainsaw. With it, the excavation can be done precisely. The wall was constructed by Destia’s subcontractor Cofra Bv from Holland.
A 100 Meters per Day
The insulation wall surrounds the GrowHow’s solid waste area , Tetra’s recharge basin, and KemFine’s fire water retaining basin. The 1.4 km long wall protects the surrounding areas from waste and spillage, because it reaches tight soil layers or impermeable rock.
At it’s deepest the wall is 12 meters long and the insulation sheet is 12,000 m2. The insulation is constructed from a HDPE laminated tongue-and-groove wall which is cased in Bentonite. Inside the landfill area, the groundwater level is kept lower than levels outside the landfill, so the water flows from the outside in.
Similar structures have been constructed at a few industrial locations in Finland. The problem so far, has been the slow construction rate and the large amount of concrete needed to keep the deep excavation open. Bentonite is needed so that the actual insulation, which is a tongue-and-groove polyethylene sheet, can be mounted straight on to the rock or tight soil.
Thanks to the machine used for the first time in Finland, 100 meters of the wall was installed every day. “It speeded up the project tremendously,” says branch manager Anton Palolahti.