The rock room at Lillsjön in Håbo was established as part of the total defense in 1976.
It was filled with diesel, mainly intended for civilian traffic if some type of crisis or war disrupted the usual supply of fuel. In the 1990s, the warehouse was dismantled, which also happened with a number of other similar warehouses across the country.
But diesel remains in the rock room in Håbo. It was discovered in an inspection by SGU, which is responsible for the environmental protection of the emptied warehouses.
– The assessment is that it is between 50 and 100 tonnes, says Jakob Levén, at the department for soil and groundwater at SGU.
Special craft
There was a risk that the oil would leak from the rock room into Lake Mälaren, which is a source of groundwater. Therefore, SGU has started a clean-up. The assignment is unusual and places special demands on personnel and equipment.
– We have to find personnel who have experience of similar clean-ups. Among other things, we use a type of boat that is remotely controlled and travels on the surface to collect the oil, says Jakob Levén.
Video: The rock room was secret – so thieves or foreign powers would be prevented from accessing the oil.