Boliden: Restoration of the mining area in Stekenjokk
After the closure of the mine in Stekenjokk, it proved difficult to restore nature around the mine site. Together with Ecogain, Boliden has developed methods to recreate natural vegetation on the site.
During the summer, Vildmarksvägen and Stekenjokk have been a popular destination for vacation. Something that not everyone knows is that one of Boliden's old mining areas is actually located there, in the middle of the bare mountain.
The mine was active during the 1970s and 80s, after which the mine area was rehabilitated according to a rehabilitation plan approved at the time. The traces of the mine are not so visible anymore. But the barren climate in Stekenjokk has made it difficult to restore natural vegetation in the area, something that has been important for Vilhelmina södra Sameby, among others. One of the goals of the attempts to bring back nature has therefore been to recreate good reindeer grazing.
In 2020, Boliden and Ecogain have planned the remediation of a five-hectare area within the old mine site. Lessons learned from previous small-scale method trials were used to develop methods that work for large-scale remediation in this type of environment.
Based on the previous pilot experiments, it has been shown that the method that has yielded the best results is to add a nutrient medium to the soil, loosen the soil surface to create germination opportunities for seeds and sow naturally occurring species .
To achieve this on a large scale, remediation was carried out as follows:
Distribution of nutrition. The nutrient medium used consisted of sewage sludge mixed with wood chips. In order to get a moderately large ration with nutrition, a common manure spreader from agriculture was used, a thin layer (about 2cm) was spread out over the area. The reason why the sludge was mixed with wood chips was to get a more even nutrient supply for several years, because an excessive nutrient giver can cause great growth in the first years and then almost no growth at all. The use of the sludge mixture is approved by the County Administrative Board of Västerbotten and sampling has been done on the sludge used.
Loosening the ground surface with excavator. Loosening the soil surface has several advantages. It made it possible to mix the added nutrients with moraine from the site, which further dilutes the nutrients. In addition, it created suitable places for seeds to germinate, with a more favorable microclimate. Stekenjokk is a very wind-exposed area and it is generally difficult for seeds to germinate.
Manual sowing of horsetail seed. Horsetail was highlighted by the Sami community as very grazing-friendly for the reindeer. Seeding was done manually, which was very time consuming. There was also an idea to collect seeds from plants on the site, which unfortunately failed as the seeds matured very late due to a cold summer.
Rolling was then done to improve the contact of the sown seeds with the soil material. This also partially secured the seeds from being blown away.
Dwarf birch seedlings of locally collected seed have been raised at Skogforsk, these were planted at the end.
Overall, the methods worked well. The machines which were used were fit for the purpose even though its usual use is not on bare mountains. On the other hand, there is continued development potential for both the collection of wild seeds, both in terms of timing and method. But also the manual seeding of seeds needs to be developed as it was very time consuming.
