Risk management and preservation of ancient mining relics

- 17 september 2009 -

Risk management and preservation of ancient mining relics - cooperation between the forestry office Reichelsheim and the Arbeitsgemeinschaft Altbergbau Odenwald

Jochen Babist

In August 2009, the Arbeitsgemeinschaft Altbergbau Odenwald (AG) was asked to check up and map historical cave-ins within the former mining claim of the manganese ore mine „Fortuna“ near Reichelsheim-Erzbach. At the last days of September, a harvester will be used to cut down a spruce forest above the mining area. This machine is weighing over 20 tons and brings punctual (potentially critical) pressure upon the overburden of old mining cavities.

Mine „Fortuna“

At the end of the 19th century, the mine „Fortuna“ produced manganese concentrates for refining steel. The winning of the seam-like, near-surface deposit involved large cavities in an area of several hundred square metres. Due to lacking mine plots, field observations within the known boundaries of the mining claim give the only source of information, which parts of the deposits have really been mined and where still parts of the surface may cave in.

For the AG, three different interests and views were to consider during field work:

1. the economic interests of the forestry office to use the harvester,
2. risk reduction during usage of the harvester,
3. conflicts between economic interests and preservation of mining heritage.

Multi-layer mapping system

The AG prepared a multi-layer mapping system using a vector drawing programme (Corel Draw 10), because a real GIS systeme was not yet fundable. The base layer involved the actual forestry maps including traces of property lines with Gauß-Krüger coordinates given from the forestry office. The second layer was composed of the scanned original mining claim map, given from the Regierungpräsidium Darmstadt, Abteilung für Arbeitsschutz und Umwelt.It was brought to the same scale as the base map, and the boundaries of the mining claim were digitised.

In the next step the AG’s first order field working area was defined by the intersection area of the historical mining claim and the clear-cutting area planned by the forestry office. This area of modern mining involves largest risk of cave-in events. Of course, pre-dating iron ore mining relics within areas outside the 19th century mining claim were prospected additionally. The field work was done by systematical mapping using GPS and an accessory printed map.

In contrast to the mining area Weschnitz (see also Eder & Babist 2009), the working area does not show important, small-scale mining relics of the first two periods of medieval to early modern iron ore mining. Only two large charcoal pile places could be mapped.

The AG found several sink-holes at random distribution parallel to the outcropping ore deposit. Nearly the complete area designed for the harvester usage was affected, even in direct neighbourhood to the important street connection Wegscheide – Reichelsheim. However, most sink-holes were obviously inactive except for two large cave-ins near the heaps of the mine. There the AG recognized actual subsidences and exposed roots of trees – indication for forthcoming large movements. Acting upon the advice of the AG, the forestry office decided to avoid the harvester usage in this area.

This example shows again, how important networking research in abandoned mining areas is. Taking into account interests of preservation of mining heritage and risk management, it is conspicious that only sustainable preservation and documentation could provide a broad data base, especially in areas without sufficient mine plots.

Download, Gelandeaufnahme Grube Fortuna.