Unique landfill construction in Kokkola

At the Kemira landfill in Kokkola, a vertical cut-off wall 1.4 km long with an average depth of 10 m was built around the landfill area in 2007. The construction of a watertight wall enabled Tetra Chemicals Europe Oy and Kemira GrowHow Oyj in Kokkola to be granted a permit for the landfill operation. Sito Rakennuttajat was the project manager and site supervisor on the project.

A watertight wall was erected around the landfill area in Kokkola. First the required groove was made with a milling cutter resembling a large chainsaw.

The seal of the base structure on Kemira landfill no longer met the existing requirements. The problem was solved with a design solution by Geobotnia Oy. The solution is based on an insulation wall that encircles the entire landfill area. This also made it possible to raise the banks on the landfill and allowed the landfill operation to continue until 2020.

To cut a narrow groove in the insulation wall, a large chainsaw-like milling cutter was used. This allowed the groove to be made to exact measures. The wall was built by the Dutch company Cofra Bv as Destia's subcontractor.

 

A hundred metres a day

The insulation wall surrounds the GrowHow solid waste area, Tetra silt basins and, for practical purposes, KemFine's fire protection water reserve. The 1.4km long wall protects the surrounding areas from waste and wastewater infiltration. The structure extends to solid soil or rock throughout.
 
At its deepest, the wall extends to 12m, and the area of the immersed coating is approx. 12,000m². The wall consists of a bulkhead, HDPE-coated plastic ground support structure and a surrounding bentonite-cement composition. The groundwater level inside the area is pumped lower than the surrounding groundwater level, so the water flows from the outside in.
 
Similar structures have already been built in Finland for certain industrial projects. So far, the problem has been the slow mounting speed and the large amounts of bentonite required to keep the deep groove open. The bentonite is needed so that the actual insulation, the polyethene sheet resembling a steel bulkhead structure in shape, can be installed straight and without obstructions to reach the rock or solid soil.

 

 
Sito Group, Tietäjäntie 14, FI-02130 Espoo, FINLAND
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