Inflow of water risen at main collecting point

At the main collecting point on the 658-m level, the inflow of uncontaminated salt water has slightly risen. The Asse-GmbH informed the Federal Office for Radiation Protection (BfS) and the Landesamt für Bergbau, Energie und Geologie (LBEG) on 27 May 2013 that the reporting threshold of 11,100 litres per day averaged over a period of one week, was exceeded. The threshold was specified by the Landesamt für Bergbau, Energie und Geologie. According to present knowledge, there are no immediate effects on the current operation or the mine's safety. The long-term average at this point has been 10,500 litres per day.

Short-time fluctuations of the daily influent volumes occur frequently and are a well-known effect in salt mines. The BfS has commissioned the Asse-GmbH to carry on observing intently the inflow of groundwater and, if necessary, to report possibly occurring further changes.

Supplement of 8 July 2013

After having increased, the inflow at the main collecting point stabilised in the last days to an altogether increased level. It is currently about 11,500 to 11,600 litres per day. Current measurements have shown that also the density of the water flowing into the mine at this point has slightly changed. It is now 2 grams per litre lower than it used to be. This is a relatively slight change which does not immediately affect the current operation or the mine's safety. The density has not changed at the other places of inflow in the mine.

If the density decrease continuously or seriously, this would indicate changes in the flow path or in the source of the influent waters. Especially in the case of a serious decrease in density of the influent waters attention must be paid, since waters that are not saturated with rock salt could dissolve the salt rock and thus increase the permeability of the flow path.

The development of the influent waters' density is therefore continuously monitored and analysed; the same applies to its amount and composition. For sale mines, it basically not possible to prognosticate the development of the inflow.

At the same time as the change in density was observed, comprehensive works were carried out at the main collecting point. The collecting tank used so far was removed and a new container was set up a little further away in a neighbouring mine opening. The water collected in a depth of 658 metres is diverted into the new collecting tank via newly routed hoses. Since the density is measures before the waters get into the collecting tank, it is improbable that these occurrences are connected. However, this is still being investigated.

Supplement of 18 September 2013

Since mid-2012, influent waters are collected at a second point on the 658-m level, about 20 metres by the main collecting point. This inflow occurs alongside the old drilling 119 which leads into stope 3 on the 637-m level which is no longer accessible. The main collecting point of the influent waters was located in stope 3/637 until the end of the 1990s.

After a plastic tube (KG tube) located inside drilling 119 was cleansed, the inflow of solution on the 658-m level has changed since 12 September 2013. Through the cleansing, the salt crystals that had formed inside the tube were removed. If the salt crystals remained inside the tube, they might break off uncontrollably and injure workers for example when taking samples of the brine.

Since the tube has been cleansed, the volume of influent solution at drilling 119 increased from about 500 litres/day to 3,000 litres per day. Parallel to the increase in influent solution at this second collecting point at drilling 119, the volume of solution at the main collecting point has decreased from about 11,000 litres per day to about 8,400 litres per day. The differences show that the two points of inflow communicate with each other.