Electronic Theses and Dissertation

Penelitian ini bertujuan untuk mengidentifikasi zona permeabilitas bawah permukaan dan memperkirakan debit rembesan air tanah sebagai dasar awal perencanaan sistem dewatering pada tambang terbuka. Penelitian dilakukan karena keterbatasan informasi hidrogeologi bawah permukaan dapat menimbulkan ketidakpastian dalam menentukan lapisan akuifer dan potensi masuknya air tanah ke dalam pit. Metode yang digunakan adalah Vertical Electrical Sounding (VES) konfigurasi Schlumberger pada tiga titik pengukuran, yaitu GP 1, GP 2, dan GP 3, serta slug test pada Sumur 1. Data VES diolah melalui inversi satu dimensi untuk memperoleh nilai resistivitas, ketebalan, kedalaman, dan interpretasi litologi. Data slug test dianalisis menggunakan metode Bouwer dan Rice untuk memperoleh nilai konduktivitas hidrolik sebagai parameter validasi hasil interpretasi geofisika. Hasil penelitian menunjukkan bahwa lapisan bawah permukaan dapat dikelompokkan menjadi tiga zona, yaitu akuifer berupa batupasir, akuitar berupa lempung pasiran, dan akuiklud berupa lempung. Zona permeabilitas utama ditemukan pada lapisan batupasir dengan nilai resistivitas 71,12–83,86 Ωm. Kedalaman zona akuifer berbeda pada setiap titik, yaitu 24,56 - 44,00 m di GP 1, 48,90 - 70,00 m di GP 2, dan 64,61 - 90,00 m di GP 3. Pola tersebut menunjukkan bahwa zona akuifer mengalami pendalaman secara lateral dari GP 1 menuju GP 3. Hasil slug test pada batupasir berbutir halus menunjukkan nilai konduktivitas hidrolik sebesar 1 × 10⁻⁶ m/s, yang menandakan kemampuan meloloskan air pada kategori rendah hingga menengah. Integrasi kedua metode juga mengurangi ambiguitas dalam membedakan lapisan konduktif dan permeabel. Berdasarkan integrasi data VES dan slug test, diperoleh estimasi debit rembesan air tanah sebesar 153,77 m³/hari. Hasil ini dapat digunakan sebagai dasar awal dalam menentukan zona prioritas pengendalian air tanah dan merencanakan sistem dewatering.

This study aims to identify subsurface permeability zones and estimate groundwater seepage discharge as an initial basis for planning a dewatering system in an open-pit mine. The study was conducted because limited subsurface hydrogeological information may create uncertainty in determining aquifer layers and assessing the potential inflow of groundwater into the pit. The methods used in this study were Vertical Electrical Sounding (VES) with the Schlumberger configuration at three measurement points, namely GP 1, GP 2, and GP 3, as well as a slug test conducted at Well 1. The VES data were processed using one-dimensional inversion to obtain resistivity values, layer thicknesses, depths, and lithological interpretations. The slug test data were analyzed using the Bouwer and Rice method to determine hydraulic conductivity as a parameter for validating the geophysical interpretation. The results show that the subsurface layers can be classified into three zones: an aquifer consisting of sandstone, an aquitard consisting of sandy clay, and an aquiclude consisting of clay. The main permeability zone was identified within the sandstone layer, with resistivity values ranging from 71.12 to 83.86 Ωm. The depth of the aquifer zone varies at each measurement point, ranging from 24.56 to 44.00 m at GP 1, 48.90 to 70.00 m at GP 2, and 64.61 to 90.00 m at GP 3. This pattern indicates that the aquifer zone becomes progressively deeper laterally from GP 1 toward GP 3. The slug test conducted in fine-grained sandstone produced a hydraulic conductivity value of 1 × 10⁻⁶ m/s, indicating a low to moderate ability to transmit groundwater. The integration of both methods also reduced ambiguity in distinguishing conductive layers from permeable layers. Based on the integration of VES and slug test data, the estimated groundwater seepage discharge was 153.77 m³/day. These results can be used as an initial basis for determining priority zones for groundwater control and planning an appropriate dewatering system.