Effect of fog and rainfall on production at Tonkolili Iron Ore Mine, Sierra Leone.

Abstract

Tonkolili Iron Ore Mine (TIOM) produces iron ore in Sierra Leone. Management of the mine is concerned about the low production due to fog and rainfall which translate into loss in revenue. This research sought to identify the effect of fog and rainfall on production operations, determine the production and revenue loss and also identify strategies to mitigate it. To achieve this, data on fog, rainfall and production from 2012 to 2017 were collected from the Marampon Pit 4 and Simbilli Pit 4 during the rainy and foggy seasons and statistically analysed. From the analysis, it was established that there is an average yearly production loss of 690 204 BCM which is 9.6% and that translates to an amount of $ 862 755 in revenue loss. Difficulties encountered during foggy and rainy seasons results in: re-drilling, difficulty in loading, flooding of the pit, poor visibility and strained vehicular movement on haul roads. It is recommended that very high light-emitting diode (LED) light should be deployed by the excavators while loading to avoid accident and also maximise production during foggy periods. Loaded trucks have to be escorted by light vehicles from the pit to the ROM pad rather than stopping operations entirely. Application of Anti-Fog Agents (chemical) on the windscreen of trucks to prevent condensation of water droplets on the surface of the windscreen. Good aggregates materials from the quarry should be employed in construction of haul roads especially during the rainy season. Mine lower benches of the pit in the dry season and reserve the upper benches for the wet season to take care of dewatering as it is used as sump during rainy season to avoid the impact of flooding on production. Mine more material during the dry and non-fog period for the loss in production during the rainy and fog period and create more stockpile to accommodate extra material to be mined. Stockpiled ore ready for plant intake must be covered with tarpaulin on the top to deter water ingress. Production operations should be scheduled such that, after the rainy season, the production loss is shared on the months during the dry season.