Siefko was part of a team of 6 people who, on behalf of the RVO (Partners for Water), made an inventory of the problems with regard to the stability of tailing dams. The assignment consisted of two missions: a fact-finding mission where a number of mining locations were visited and giving a number of workshops to various stakeholders and the Brazilian ANM (National Mining Authority).

The reason was the large dam failure at Brumadinho in January of this year, in which many people died. Earlier, in November 2105, there was also a mine dam failure in Brazil near Mariana. Here, there were also casualties and there was also a lot of environmental damage. The tailing material has flowed into a river in the latter case and has polluted a large part of the river downstream.