ANALYSIS OF THE DRAINAGE SYSTEM IN THE AREA OF ??VOID PIT ON2 TIMUR SITE LATI MINE OPERATION PT BERAU COAL, EAST KALIMANTAN

• Main Author: Salam Aditya Afridol, Muhammad
• Format: Final Project
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/69425
• Institution: Institut Teknologi Bandung

The characteristics of mining activities, especially coal mining, are changes in land that have the potential to form ex-mining holes called voids. Void is one of the post-mining areas that has the ability to store water. The ON2 pit is located at the Lati site which is a post-mining area and contains the East ON2 Void. The drainage system in the East Void ON2 area needs to be designed to manage the quantity of surface runoff water in accordance with the purpose of post-mining activities. The design begins by analyzing rainfall data at Pit ON2 Site Lati in the period year 2012- 2022 using the Gumbell distribution so as to get the designed rainfall intensity of short duration with a certain return period. The catchment area is analyzed from topographic data based on the direction of surface water flow. Peak discharge in the catchment area was determined using the SCS (Soil Conservation Service) hydrograph method. From the results of data processing, a drainage facility will be designed in the catchment area of the void and the outlet of the East Void ON2. From rainfall analysis and intensity is 11.41 mm/hour and catchment area of 2.6 km2, the East Void ON2 inlet discharge is 1.6 m3/s. To overcome the inlet discharge of that size, a drainage inlet perimeter is designed with a dimension range of bottom width x height: open channel category 1 (0.3 x 0.5) m ; open channel category 2 (1 x 1.2) m ; open channel category 3 (1.2 x 1.5) m. In order to control peak of discharge of outlet to be less than 0.5 m3/s, a retention capacity of 144,840 m3 is required. Considering the void conditions at an elevation between 36 masl to 39 masl, the discharge option at an elevation of 36 masl and a 2.24 m water level rise in the void is expected in order to fulfil the retention capacity. As a completeness of the discharge drainage facility, a controlled open channel with a base width of 0.3 m and a canal base width of 1 m is required.