Fissure structure analysis to unravel groundwater inflow problem in gold mining site of Pongkor area, West Java, Indonesia

Abstract

Hydrogeology of Pongkor area, West Java, Indonesia is characterised by fractured aquifer system. The aquifer consists of volcanic rocks of tertiary period, namely Cimapag formation. It is fractured with orientations axis of the fracture patterns are northwest - southeast and northeast - southwest. Pongkor area is drained by two main surface streams, called River Cikaniki and river Cimaja, normally flowing northward direction. In the study area, there is such a vein structure known as Vein Ciurug containing gold ore deposits. The vein is exploited by subsurface tunnelling system. During expansion of the mining activity, some ramps were needed to be constructed. When a ramp at the altitude of +484 m above sea level was expanded, before reaching the vein, the drilling penetrated a saturated zone, causing groundwater inflow with a relatively massive rate. Further, static groundwater flow flooded the opening ramp down with water level of +499 m above sea level, resulted in disruption of mining activities at the ramps under the elevation 500 m above sea level. This study is to analyse the source of groundwater inflow and set a recommendation to solve the problem.