STORAG ETZEL GmbH plans and manages the construction of underground caverns for the storage of gas and oil reserves in the North German town of Etzel. Constructing a cavern is a complex and time-consuming process which generally takes 3-4 years. After construction has been planned, a drilling site is erected from where several locations can be drilled into. By flushing the salt stored in the salt domes with salt water from the North Sea (solution mining), a cavern is formed which, upon completion, can be used to store natural gas and oil. When the cavern has been created, the technical equipment is then installed so that the gas first- fill can be performed.