Fossil water in Konrad
The Konrad iron ore deposit formed about 150 million years ago; it developed from a primeval ocean. When the geological layers deposited, parts of this sea water were trapped. As the rock of the future Konrad repository is capable of taking up small volumes of water, part of this fossil water (formation water) is correspondingly enclosed in fine pores and clefts in the rock.
Emergence and volume
During the operation of the deposit, e.g. when cavities are driven underground, the rock is "injured" and releases the trapped solution. The "dewatering" of the rock occurs at swallow holes and wet places underground. Such places have only a limited contingency of formation water and therefore run dry entirely after some time.
In 2009 the inflow of brine amounted to altogether around 6,000 cubic metres. That corresponds to an amount of approx. 16 cubic metres per day. Half of it originated from the inflow to the mine. The remaining 3,000 cubic metres originated from a geological layer near the surface, the Hils sandstone about 400 metres deep, which is crossed by the shaft piping 2 located to the south of the mine area.
The water is continuously monitored and collected underground in water tanks and so-called pump swamps (collecting points the water is pumped from). The miners use part of the water to fight the dust and to maintain the roads underground. The rest is taken above ground.
No connection to the groundwater
In the area of the Konrad repository there are no direct natural connections between aquifers and the deeper lying geological layers where one intends to store low-level and intermediate-level radioactive waste in future. Man-made connections resulting from earlier test drillings have been densely backfilled in the meantime. The two shaft pipes of the repository mine will be sealed as well after the operational time.
Significant difference compared with Asse
The area at the Konrad repository where low-level and intermediate-level radioactive waste will be stored in future does thus have no contact with surface water. This is the key difference to the Asse mine, where water flows into the salt dome from the adjoining rock. This damages the salt formation continuously, causing the mine to collapse at some point in time unless it will be remediated. The 160 to 400-m-thick surface layer of clay seals large areas of the Konrad repository and prevents near-surface water from flowing into the mine. As the geological barrier is intact and there are no water routes, the inflow of near-surface groundwater can be ruled out.
State of 2017.03.30