Designing Open Channel Dimension for Imkasu Area West Papua

Abstract

Gag Nikel Ltd belongs to a Contract of Work located in Gag Island, West Waigeo Islands District, Raja Ampat Regency, West Papua Province. The open pit mining system employed at this company will enter the mining location and therefore, requires a design of open channel for diversing water coming from rainfall, run off, and ground. The rainfall intensity calculated by Mononobe formula obtained 5,994 mm / hour, whereas the catchment area got 0.59 km 2. The total discharge of run off calculated by Rational Formula gained 1867,956 m 3 / hour. Meanwhile, the design of open channel calculated by Manning Formula yielded wet section (A) = 0.668 m 2, base width (b) = 0.714 m, and depth (h) = 0.714 m, surface width (B) = 1.542 m. Box control having the volume 1 m3, length = 1 m, width = 1 m, and height 1 m must be made every 1 kilometer of open channel length. Around the area of open channel, the used tire must be given to reduce the erosion rate flowing into settling pond. All of these are necessary because the open channel is located near the natural channel and we must also consider several regulations such as Presidential Decree and IPPKH adjusted to the technical study that has been designed.