Surveyors from the DMT GmbH & Co. KG specialist unit for fire safety, at the Centre for Fire and Explosion Safety have determined, following specific gas measurements at various locations on the Graf Moltke tip in Gladbeck/Germany, that “there is no evidence of health risks in the locality”. The DMT surveyors conducted specific gas readings on the Graf Moltke spoil tip on 14th August 2019 on behalf of RAG Montan Immobilien GmbH, Essen/Germany, who are responsible for the tip (Figure 1). The project manager for DMT is a publicly-appointed sworn expert for fire safety for spoil tips, coal stores and disposal sites. DMT belongs to the TÜV NORD GROUP. The background to the readings is the smouldering fire in the tip, which has been known about and monitored for years and which has intensified in recent months, leading to increased gas emissions.
The gas readings on the tip, to which public access is prohibited, were conducted in the immediate vicinity of the warm areas of the western slope. Readings were conducted at two points whose visual appearance and odour were noticeable. The surveyors took readings directly on the ground and in a 1 m deep fissure which had developed there, as well as at heights of 0.5 and 1.5 m above the source location in the direction of the wind. Environmental readings were also taken in the south/west wind direction at two points in the commercial area.
The readings were evaluated in accordance with the legally stipulated incident assessment values, the official occupational limit values and the permitted exposure values for the emergency services. The readings assessed the accrual of gas emissions including benzene, hydrogen sulphide, sulphur dioxide, carbon monoxide, carbon dioxide, hydrogen, nitrogen, methane and oxygen. These gases are usually produced when coal is burned and, in certain concentrations, can have a harmful effect on the environment and the population.
In the case of the current readings, limit values were only exceeded for the individual gases carbon monoxide, benzene and hydrogen sulphide immediately at ground level and when measured in the ground fissure. At a height of 0.5 m, only the value for hydrogen sulphide was slightly in excess of the limit value. At a height of 1.5 m above the source location, no more critical measurement values were observed due to the mixing of all substances with the surrounding air. Due to this dilution effect, noticeable pollutant concentrations are – according to the surveyors – not to be expected in the vicinity of the tip. The readings in the commercial area were correspondingly insignificant.
However, a slight unpleasant odour was noticed, which is perceptible even at values significantly below the official limit values. This odour of rotten eggs occurs irregularly and is considerably influenced by the wind and weather conditions.
RAG Montan Immobilien has commissioned further readings in different wind conditions, in order to assess levels in the entirety of the area.
RAG Montan Immobilien would like to expressly reiterate once again that access to the Graf Moltke tip is absolutely prohibited, due to the potential danger.
The fire inside the tip has been smouldering for years. Ever since, it has been constantly checked and monitored, both by RAG Montan Immobilien and by commissioned surveying companies. The safety measures include regular temperature readings via probes, regular inspections with regard to the formation of fissures on the tip and infrared measurements from the air. Three areas of the western tip and four areas in the east and south-east are being specially monitored.
At present, RAG Montan Immobilien is devising a restructuring concept, in order to contain the smouldering fire in the area of the western slope and to enhance the stability of the spoil tip. (RAG MI/Si.)