Three of Eskom's 400 kV power lines (Duhva-Kendal I, Duhva-Apollo I and Duhva-Minerva I) traverse the old, disused Landau coalmine area near Witbank in Mpumalanga Province. Eight pylon groups support the three parallel lines over the 2, 5 km distance of undermined ground. Coal mining in the Landau area took place from about 1898 to 1950, after which the mine was abandoned. The bord and pillar method of mining was used, comprising the extraction of near-horizontal coal seams at various depths and leaving coal pillars in place to support the roof. In the mid-nineties it became apparent that spontaneous combustion of the coal pillars and areas where the coal had been exposed had set in over the years and had resulted in increased deterioration of the stability of the area. The result was that several depressions or sinkholes had developed in the vicinity of the lines in the recent past. Eskom Transmission realised the danger of further sinkholes forming underneath the pylons and the consequent likelihood that structural failure of the towers could occur. This could result in the loss of one or even more of the lines simultaneously. The initial expectation was that the lines had to be relocated to a more stable area at a cost of about R30 million.
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