Study on the Economic Feasibility of an Underwater-Sill (UWS) Development for Sediment Countermeasure at Patimban Port’s Navigation Channel

Abstract A new international seaport is under construction at Patimban area of Subang Regency, West Java, Indonesia. This Port’s navigation channel runs from the position of –6m LWS to –17m LWS of the existing depth with total length of 3,762 m. The original design considers that the existing sedimentation rate is low along the channel. The Cipunagara River which shows continuous delta expansion of about 1.00m to 1.25m toward navigation channel. In reference to the successful application of Underwater-sill (UWS) structure in controlling the siltation rate into the navigation channel of Kumamoto Port in Japan and Tuban Port in East Java Indonesia, the possible application this type of structure was carried out. The calculation has resulted that installation of UWS with height of 1.0 m, 1.5m, 2.0 m, and 4.0 m respectively decrease the sedimentation rate to be 0.09 m per year, 0.06 m per year, 0.022 m per year and 0.022 m per year. The present economic feasibility study concluded that 2m height UWS which is designed for minimum service life of 30 years with development interest rate at 10 percent per year and an annual inflation rate at 10% gives the most economic investment.