Rancangan Teknis dan Biaya Sistem Penyaliran Tambang Terbuka di PIT C PT XYZ Kabupaten Tanah Laut, Kalimantan Selatan

Abstract

The open-pit dewatering system at Pit C of PT XYZ, Tanah Laut Regency, South Kalimantan, faces problems such as an inadequately sized sump, suboptimal open channels, and an inefficient pumping and piping system, resulting in water accumulation in the mining front area. This study aims to determine the total inflow of water into the pit, design the sump and open channels, plan the pumping and piping systems, and estimate operational costs. The study utilized secondary data, including maximum rainfall for the 2015–2024 period, groundwater discharge, topographic maps, pump and pipe specifications, and the prices of diesel and pipes. The research methods included determining the frequency distribution of rainfall based on statistical parameters, calculating design rainfall using the Gumbel method with a 10-year return period, and calculating runoff discharge using the Rational method. The dimensions of the sump were designed in accordance with ESDM Ministerial Decree No. 1827 K/30/MEM/2018. Open channels were calculated using the Manning method, and the pumping system was analyzed through calculations of total head loss, pump requirements, and water balance. The results of the study show that the design rainfall with a 10-year return period of 138.67 mm produces a total inflow of 5.49 m³/s, consisting of a runoff discharge of 5.10 m³/s and groundwater flow of 0.39 m³/s. The sump is designed in the form of a trapezoidal prism with a volume of 299,110.58 m³ in accordance with applicable standards, while the open channel with a trapezoidal cross-section is designed with a flow capacity of 6.31 m³/s, thereby exceeding the total inflow of runoff. The piping system uses 10-inch-diameter HDPE pipes with a length of 1,117.90 m with a total head loss of 81.3 m, while the pumping system requires 4 DND 200-5HX pumps operating 20 hours per day. Estimated operational costs for pumping amount to Rp215,392,958.04 per day, and the cost of pipe procurement is Rp811,529,777.88. The designed dewatering system is expected to effectively control mine water, thereby minimizing flooding in the mining front area.