From landfill to green landscape

Our environmental construction professionals are working hard on an old landfill in Forssa, Finland. In two years, the blackish mountain of waste will be replaced by a beautiful green hill.

Heavy lorry traffic to the old Viksberg landfill in Forssa ended already in the mid-1990s. However, this winter the rumble of heavy machinery has again been heard from this 20-hectare area. The reason behind this is the cleaning and protection of the landfill site that started in November and is due for completion in late 2019.

According to Mikko Moilanen, the project's supervisor at Lemminkäinen, the massive earthmoving and land improvement project will completely transform the entire area, not only the scenery but also the soil.

"Contaminated soil moved from the fringes of the landfill is treated with fly ash delivered from incineration plants. When ready, the grass-covered hill will be approximately ten metres high," explains Moilanen.

Swampland is posing challenges

There is a lot of work to be done as, in addition to earthmoving, we will underdrain the entire landfill site and build protective embankments around it. Land masses treated with ash will be covered with a bentonite carpet, which in turn will be covered with a layer of soil for light landscaping. The purpose is to ensure that rain or drainage water will not release any harmful substances from the landfill soil into the surroundings.

"The project is further complicated by the swampy ground, which also restricts the thickness of the topmost soil layer. If there is too much weight, the whole mass may start moving. We might literally get bogged down," Moilanen says with a laugh.

We started working in Viksberg in November and the project has proceeded nicely on schedule. The low-snow winter and a couple of crisp below-zero spells have helped significantly as the soft soil froze to support the weight of the machinery better.

Solid experience is an advantage, too: Moilanen and his crew have carried out similar projects in Ämmässuo in Espoo, and also in Raseborg.

"In both of these locations, the project area was less than seven hectares so here in Forssa, the scale of the project is totally different. Even when considering earthmoving only, this is a very significant contract. The budget amounts to nearly EUR 4.0 million and we have roughly fifteen people working here," Moilanen says.

Solar panels and exercise routes?

Gases brewing up in Viksberg's soil are collected, analysed and utilised as a source of energy, for instance. Gas collection wells and pipe systems are part of our refurbishment contract.

Technical Director Antti Heinilä and Municipal Engineering Manager Tero Tiensuu, both working for the City of Forssa, have been satisfied with the progress of the project. Thanks to competent personnel, the project that had been on hold for decades is becoming another element in Forssa's long-term circular economy strategy. Its core is the centre of environmental business activities and expertise that has formed over the years in the nearby Kiimassuo area.

"The decommissioning of the landfill and the development of Kiimassuo have been the start of a new era for the entire town. At that time, it was realised that there are other uses for waste than just piling it up on a landfill. Now, recycling has become commonplace and only a fraction of waste is taken to landfills," notes Heinilä.

The future use of the area is still being planned. It's likely that it will be a sports and recreation area as the unstable ground won't support building construction.

"In Tapiola, Espoo, a golf course was built on a landfill site, but I'm not sure if there's enough interest for that here. One alternative could be a solar energy park. The hill will certainly support the weight of the panels," Heinilä speculates.

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