One of the factors influencing the achievement of production targets in mining companies, especially in open pit mining, is weather. When using the open-open method, the weather or rain is one of the factors that will serve as a hindrance to the work, which causes a slippery recovery process. However, some measures are usually carried out to avoid slippery conditions after rainfall when the conveyance re-enters the mine road, as well as to avoid accidents and keep production running according to plan. Based on data from late August 2022, it was found that the slippery ratio in Pit 9 was above the company’s set plan, which should have been 40% of the rainy hour budget. According to data on rainfall in August 2022, the total number raining hours per day was approximately 23 hours with rainfall reaching 260 mm/day. The slippery ratio, which was more than expected, even reached 86%, affecting production with an overall loss of 47,220 Bcm in August 2022. Therefore, improvements were made to reduce the slippery ratio by layering the hauling road with a layer of base coarse material (gravel). Furthermore, from the results of the analysis and calculations, it was discovered that one segment of the hauling road OB (Fast Track) with a length of 919 m, required a base course of 6,891 m3, while the coal hauling road in the 3.5 km segment, which had a length of 865 m needed a base coarse of 5,188 m3. It was also confirmed that the coal hauling road in the mars road segment, with a length of 970 m, required a base coarse of 5,819 m3. To meet these layering needs, base coarse material was taken from 2 different sources. The materials used as the base coarse were ultramafic igneous rocks, namely Serpentine and Peridotite. In addition, it was observed that after coating each predetermined segment with the igneous rocks, the slippery ratio improved to 38% or an average of 1.13 hours in September after spreading the base coarse. This is in accordance with the standard parameters specified by the company, which is 40%.

Keywords : Slippery, Base Coarse, Ultramafic Rock.