ANALYSIS OF DRAINAGE FACILITIES AND PEAK DISCHARGE LOAD IN THE RECLAMATION AREA OF PT XYZ

• Main Author: Agrianingrum, Anita
• Format: Final Project
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/86387
• Institution: Institut Teknologi Bandung

PT XYZ is a copper and gold mining company that utilizes open-pit mining methods. PT XYZ is currently conducting reclamation in the TGL area, which is no longer active for mining. The reclamation area of PT XYZ features a tiered topography with varying peak discharge rates for each tier. When it rains, water flows towards the downstream/outlet of the tiers, resulting in the accumulation of peak discharge loads. Since this peak discharge load poses a risk of flooding in the downstream areas, it is necessary to implement drainage facility planning and management to reduce the peak discharge. The design of the drainage facilities began with an analysis of rainfall data from the RF-10 rain gauge station for the period from 2007 to 2022. The rainfall data was analyzed using the partial duration series and Log Pearson Type III distribution to determine the design rainfall intensity. Based on topographic data, the reclamation area has several sub-tiers separated by road junctions. The peak discharge for each sub-tier was calculated using the synthetic unit hydrograph method from the Soil Conservation Service (SCS) to identify junctions with high peak discharge loads. Subsequently, culverts were used as water flow connectors, serving as a peak discharge control mechanism to reduce the peak discharge load at the tier outlets. The rainfall intensity for a 2-hour duration was determined to be 49,95 mm/hour with a return period of 50 years. The highest peak discharge loads were found at the outlets of tier 2 with 4,76 m³/s; tier 5 with 6,62 m³/s; tier 6 with 6,87 m³/s; and tier 7 with 6,59 m³/s. To reduce these peak discharge rates, culverts with diameters of 0,4–0,5 meters were installed at the road junctions, with a flow capacity lower than the peak discharge entering the culverts. The peak discharge at the tier outlets was reduced to 3,65 m³/s for tier 2; 4,11 m³/s for tier 5; 4,81 m³/s for tier 6; and 4,59 m³/s for tier 7. Other recommended drainage facilities include open trapezoidal channels with bottom width x top width x height dimensions of 1 m x 2 m x 1 m and drop structures to reduce flow velocities from 14,60–30,39 m/s to 3,13–4,43 m/s, with the requirement of around 35–100 drop structures