EN 
DE RAG Aktiengesellschaft is planning to rehabilitate and finalise the western slope of spoil tip 1 of the former Graf Moltke 3/4 mine and coking plant in Gladbeck.
There are various fire pockets and hot areas within the western flank of the stockpile body, so that special fire protection requirements must be placed on the securing and final design of the stockpile, which is under mining supervision. The approximately 50 metre high rising body of the heap is made up of washed rock material, whereby the heap was previously simply filled in without any special compaction measures. On the western side, the slopes of the heap have steep inclinations of up to approx. 1 : 1.6 (slope angle of approx. 32°). In the course of stability analyses carried out, it was determined that the existing slopes are not sufficiently stable.
The primary objective of the remediation measures is to fight the fire in the area of the current hot zones of the waste rock pile on the western flank as quickly as possible. Firefighting requires the prevention of oxygen ingress into the body of the waste rock pile, which is to be achieved by building a mineral sealing layer on the slope flanks of the waste rock pile body in accordance with the specifications of the fire protection expert. The required backfill on the existing stockpile body (sealing layers, protective layers, vegetation layers) is to be designed in such a way that the localised structural stability deficits of the stockpile embankment are also remedied in the course of the fire protection-related remediation.
The Wittringer Mühlenbach runs parallel to the western foot of the stockpile as an open channel. Due to the small distance between the foot of the stockpile and the stream channel, the planned redevelopment of the stockpile requires the stream to be backfilled over a length of around 180 metres and the corresponding section to be temporarily piped (DN 1600 pipeline). In future, the Wittringer Mühlenbach is to be re-routed as an open channel along the new foot of the spoil tip.
Remediation work began in November 2022; the first implementation phase (temporary pipework and backfilling of the open channel of the Wittringer Mühlenbach stream, construction of the seal and backfilling of the stockpile up to a height of around 6 metres) has been completed. The actual slagheap fire remediation will take place in a second implementation phase, which is expected to start in November 2023.
Since 2020, TABERG Ingenieure GmbH has been working in collaboration with RAG AG and other specialist planners on the planning and implementation of the measure to remediate the spoil tip. The scope of work includes the geotechnical investigations and consulting services (including field investigations, stability investigations of the existing slopes), the planning of the earthwork remediation of the spoil tip including the preparation of the contract documents as well as the monitoring of the measure in the function of construction supervision, expert supervision and external supervision.
