Annual altitude measurement
Even before the first caverns of the Etzel cavern facility were excavated in 1974, monitoring of the surface for changes in elevation began at the Etzel site in order to record the effects of cavern construction and operation on the surface.
In addition to the magnitude of the changes in elevation, the extent of the area of influence, which is limited by the zero subsidence line above which no change in elevation can be detected, is also of interest. For this purpose, a so-called precision leveling is carried out annually by an independent expert in a close-meshed fixed point network, which is coupled to the official measurement network of the national survey.
In 2015, STORAG ETZEL and the local citizens' initiative "Quality of Life" had jointly agreed, as a confidence-building monitoring measure, to record a total of 36 buildings in the vicinity of the cavern facility with a building monitoring system and to check them regularly with regard to possible subsidence damage and possible misalignment.
36 buildings monitored since 2018
Up to 2018, 18 buildings and observation objects (e.g. extensions to buildings, stables) were included in the monitoring by the citizens' initiative and STORAG ETZEL after consultation with the respective house owners. At the beginning, the houses are initially measured on the basis of height bolts and assessed by a recognized building expert in their actual condition.
In the following years, the buildings concerned will be surveyed every 2 years in connection with the height observation of the cavern field (annual leveling) with regard to inclination. Every 5 years, the buildings are also surveyed by an expert in order to be able to detect any subsidence effects at an early stage. The monitoring procedure complies with the standards and practices of surveying technology and mining damage assessment recognized in Germany.
Further objects have been included in the monitoring process as of 2021
The approval of the new framework operating plan of STORAG ETZEL provides for successive inclusion of further monitoring objects in the existing monitoring program for buildings. The specification of the objects was made in the approval procedure for the general operating plan by the responsible mining authority. At the end of 2021, these additional objects were surveyed in consultation with the respective owners and then a zero measurement was carried out.
The survey overview of the building monitoring program can be viewed here: