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Surplus excavation material changes from a problem into an opportunity

Based on the excavation material development plan completed last year, Helsinki can save up to hundreds of millions of euros by reducing the amount of surplus spoil and reusing it sensibly.

“Surplus spoil has been a problem ever since the first farmer stuck his hoe in the soil and wondered what to do with all that peat,” smiles Anton Palolahti, Director of Sito’s Construction Business Sector.

If the problem of surplus spoil has been pondered in Finland ever since the early days of farming, Sito has also been involved with the topic for quite a while. This is naturally due to Helsinki’s unique seaside location, sandwiched between the neighboring municipalities.

Sito made the first excavation material report for the City of Helsinki back in 2004. This was followed by the implementation of an online excavation material exchange service in 2004–2008.

“Surplus land material has long been a blessing for Helsinki, enabling it to expand out to sea. Not everything can be dumped into the sea, however, especially not clay soil. The neighbouring towns of Espoo and Vantaa have their own earth landfills, but Helsinki does not,” explains Palolahti.

Long-term solutions

The problem has recently come to a head, as Helsinki can no longer use the landfill in Vantaa for placing its spoil. Disposal sites for surplus spoil have sometimes had to be sought from very distant locations. It has been clear that the problem requires a holistic approach and that a completely new, farsighted, and very long-term solution should be found.

Sito has been able to provide support for this. The current state of Helsinki’s excavation material was reviewed in 2008–2014, and the excavation material development program 2014–2017 is currently underway. An action plan is currently being prepared on the basis of the development program, to be completed by the end of this year.

The City’s Mass Coordinator Mikko Suominen has achieved a great deal in just a few years. Whereas in 2010, half a million cubic meters of spoil was transported from Helsinki to Vantaa’s landfill, no excavation material had to be dumped at any landfill last year.

As mass coordinator, Mikko Suominen organizes the reuse of excavated spoil if at all possible, preferably as close as possible to the excavation area. “It is to everyone’s advantage if traffic can be reduced and resources saved,” he emphasizes.

Savings and sensible use of resources

The summary of the excavation material development program 2014–2017 emphasizes that soil maintenance is a basic precondition for cost-effective and eco-efficient construction. By reducing the amount of surplus spoil and reusing it sensibly, the City of Helsinki can save EUR 5–10 million of the construction costs of public areas annually.

Non-renewable soil material should be used sparingly and efficiently. Finland uses the second largest amount of soil per capita in Europe, a total of approximately 120 million tons per year.

Every year, construction work in Helsinki generates more than 800,000 tons of uncontaminated spoil that has not been reused within the city. With current transport costs and acceptance prices, this results in annual costs of EUR 25 million.

“There are three ways to use surplus spoil. They can be used for earth fills, landfills can be set up, or the material can be recycled. In practice, all of these naturally need to be applied as needed,” Palolahti points out.

The measures proposed in the excavation material development program aim to halve the City’s earthwork costs and soil transport distances during 2014–2017 in comparison to the 2010 level. The goal is to reuse the excavation material on location as much as possible, for example. Soil that can be used in other construction as such or in a processed form may not be delivered to landfills. One of the goals of the town planning and implementation phase must be the minimization of surplus spoil and the maximization of material good for reuse. Eco-efficient soil mass management can help achieve a cost-benefit ratio of 2–4 times that of an unplanned situation.

In some areas, pre-compression fills can be used in place of expensive ground improvements and mass changes, for example, if the reusable soil can be stored on site for 2–5 years before construction. The soil can be used for the construction of recreation areas, parks, and noise barriers to increase the residents’ quality of life. Disposal in landscape construction makes possible the construction of areas for recreation or outdoor activities that could not be implemented without the availability of surplus spoil.

A new kind of cooperation

Palolahti says that the project has been a shining example of what can be achieved when a major problem is addressed in collaboration. “Previously, city agencies were well aware of the implications of excavation materials for them, but now that the bigger picture was revealed, the issue was seen from a much wider perspective and a new kind of dialog was born. We have organized seminars and initiated new forms of collaboration between the different players, neighboring cities, and contractors. These include energy company Helsingin Energia and Helsinki Region Environmental Services HSY, which have a great many excavation projects and generate a large amount of spoil,” says Palolahti.

“The increased discussion and introduction of new ideas has been a positive bonus in the project,” adds Suominen.