To say it was a snowy start to the year in northern Sweden would be an understatement. There were daily reports of traffic chaos caused by snow, with new snowstorms arriving one after another.

“In all the years we have operated in Västernorrland, I’ve never seen as much snow as this year. In some places it reached a metre deep, just while we were working,” says Mats Lindberg, Project Manager for Lake Lime at SMA Mineral.

Vital for diversity

In other words, a lot of snow, which then all has to melt. And with a thaw comes the risk of so-called spring acid shock, which causes a dramatic reduction in the pH value of lakes and watercourses. The acidic fallout is stored in the snow and when the snow melts, everything is released at the same time. And that’s where the lime comes in.

“The lime neutralises and counteracts acidification damage. Achieving a good pH balance is a prerequisite for maintaining biodiversity, enabling species to survive and continue to regenerate,” explains Mats Lindberg, who continues:

“With natural powdered lime, you never have to worry about too high a pH because the lime actually stops dissolving at neutral pH.”

Transport by rail

A total of 173 lakes throughout the county of Västernorrland have been limed. The powdered lime, which is produced at Gåsgruvan outside Filipstad, was transported by rail up to Långsele and Anundsjö.

“We always transport products by rail wherever possible. The three trains, from Gåsgruvan to Långsele and Anundsjö, carry the equivalent of almost 80 truckloads, so there is an additional environmental benefit,” says Mats Lindberg.

1 tonne in just a few minutes

The sacks of lime were then moved by truck to predetermined loading points. When the helicopter crew arrived on site to carry out spreading, the right amount of lime was there ready. A ground crew filled the baskets used to spread the lime while the helicopter hovered just above the ground. Changing over the baskets takes about ten seconds, and actually spreading the lime, 1 tonne at a time, takes the helicopter just a few minutes. Then it’s time to pick up a new full basket again.

Lake liming – 5 quick questions

Why lake liming?

Lake liming prevents acidification of lakes and watercourses, something that is a potential threat to biodiversity.

How often is liming needed?

To maintain a consistent pH value, regular liming is recommended, but it’s the body of water’s turnover time that determines the actual frequency. In Västernorrland, the lakes are limed once a year.

What happens?

Lake liming is carried out by boat, helicopter or lime dosers that dispense the right amount of lime into running water in streams or rivers.

What type of lime is used?

Finely ground powdered lime is usually used for lake and dose liming. When liming wetlands, a slightly coarser powdered lime is used, which is moistened to prevent dust affecting the surrounding vegetation. The products consist solely of natural limestone that has been crushed and ground to suitable fractions for these specific purposes.

How do you know the lime is helping?

To ensure the benefits and effects of liming operations, the pH of the water is checked several times during the year. Biological monitoring is also carried out through sample fishing and benthic fauna surveys.

The heavy snowfall posed a challenge. “We had to clear a lot of roads to get through with the trucks and unload the sacks of lime,” explains Project Manager Mats Lindberg.