ANALISIS POTENSI ALIRAN AIRTANAH BERDASARKAN NILAI PERMEABILITAS SEKUNDER, PADA TAMBANG DALAM, CIURUG CENTRAL L. 500, UNIT BISNIS DAN PERTAMBANGAN EMAS, PT ANEKA TAMBANG TBK, PONGKOR, KABUPATEN BOGOR JAWA BARAT

Abstract

PT Aneka Tambang, Tbk Unit Bisnis Pertambangan Emas Pongkor is Ministry of State Owned Enterprisesmining, which is involved in ore mining and located on Desa Bantar Karet, Kabupaten Bogor, Jawa Barat. Mining method of this Pongkor site is closed mining which is construction an underground tunnel to mine. Inside this tunnel is constructed a access like way called by ramp down and ramp up. Manufactured of ore did by the blasting methode of tunnel wall. This blasting method causing problem like the groundwater which suddenly appears with certain debit. The accumalation from the groundwater will create a flooded area, specially water with big debit and draw many problems heavy machine trffic and envirotmental disruption like flood. Incase to solve about groundwater problem, hidrogeology’s knowledge is necessary needed to deted the groundwater flow direction. The research did by determine the groundwater flow potential which is analyzed by secondary permeability valve. The valve got by the scanline methode, which expand the string the fracture tunnel wall with certain lenght, next, cut fracture is measured by the stike and dip and then observed the characteristic of fracture, such as aperture, spacing, lenght, filling material, shape, and rought. Scanline method is used at wet tunnel wall which dripped and flowed the water. At the ramp down elevation 450 (RY – 01), the result of average secondary permeability is 3.6 x 10-4. The fowed wall has the biggest value is 2.6 x 10-3. For the ramp up elevation acces 500 (RY – 02), the value average secondary permeability is 1.3 x 10-5. The highest groundwater flow potential is located at RY – 01 which consist of STA 3 and STA 6. At both of this observation station, found the groundwater flow with small debit, and for STA 6 is a point of groundwater flow accumulation is contour map MAT. Due to the secondary permeability value of fracture characteristic of both location, RY – 01 has bigger potenrial to flow the water than RY – 02. Keyword : groundwater, scanline, secondary permeability, aperture, space of fracture, lenght, shape, rought