No. 4/20 - “Reichelt swamps” at a depth of 750 metres are backfilled

On 30 June 2020, the Bundesgesellschaft für Endlagerung (BGE) started to backfill the “Reichelt swamps” of the Asse II mine in Remlingen. The “Reichelt swamps” are located in the north-west of the mine on the 750-metre level. For decades, water has been collected here in the form of salt solutions – most recently around 140 litres per day. The “Reichelt swamps” are more than 350 metres away from the emplacement chambers containing radioactive waste. The solutions that collected here had no contact with the waste.

Backfilling is part of emergency planning (i.e. the best possible damage prevention in the event that the influx of solution in the mine should one day no longer be controllable). Because this “worst case” cannot be ruled out with certainty despite all measures, the BGE is implementing all emergency planning measures as early as possible. This also corresponds to the demands from the region to push ahead with emergency planning just as consistently in parallel with the retrieval of the waste. The BGE points out that the legally prescribed retrieval is not affected by the construction measures. On the contrary, the retrieval planning is based on the assumption that the “Reichelt swamps” will be backfilled.

In order to stabilise the “Reichelt swamps” in the long term, the area must be backfilled with a special concrete (sorel concrete). The volumes to be backfilled amount to around 1,150 cubic metres. The BGE has regularly provided information on this, including in the annual Mountain Monitoring Talks. The procedure was also discussed with the experts of the Asse 2 support group.

Before backfilling, “foreign material” first had to be removed from the area, old boreholes had to be backfilled, and the area had to be sealed with an 80-centimetre-thick formwork wall. The backfilling itself is done via three boreholes, each reaching the highest points of the area. The required building material is produced in the immediate vicinity by an underground building materials plant. The backfilling is expected to be completed within two weeks.

The solutions have so far come out in the open in the Reichelt swamps and are being collected. With the help of boreholes, the solutions can still be pumped out even after backfilling. In the future, the influx of solution can be observed with the help of special boreholes (monitoring boreholes). The boreholes are drilled from the 700-metre level and can therefore be used in the long term.

About the “Reichelt swamps”

The Reichelt swamps are an area on the 750-metre level to the north west of the Asse II mine near which potash salts were mined in the early 20th century. In mining language, the term “swamp” means an area that is lower than the surrounding level. Solutions can collect in this. The solutions can be collected and removed or “bailed” in mining terms. In everyday language, a swamp is usually understood to mean a bog or morass. However, such a comparison is inaccurate for the actual situation in the mine.