STUDY OF EFFECT OF DREDGING ACTIVITY ON THE CONCENTRATION OF TOTAL SUSPENDED SOLID (TSS) AT PATIMBAN PORT AND TANJUNG JATI-B PLANT POWER JEPARA WATERS

• Main Author: Abror Hediarto, Mohamad
• Format: Theses
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/67310
• Institution: Institut Teknologi Bandung

The construction of the Patimban Port, West Java, and the development of the Tanjung Jati-B Steam Power Plant (PLTU) Jepara, Central Java, could not be separated from dredging activities. The dredging volume produced from the construction of phases 1 and 2 in the pool, channel and reclamation area of the Patimban Port reached > 10 million m3, while the development of Tanjung Jati-B PLTU activity produce > 800 thousand m3 dredging volume. TSS produced by dredging activities can affect the condition of water quality and coastal ecosystems. Therefore, it can reduce coastal productivity and will have an impact on coastal socio-economics. Monitoring TSS that produce in dredging activities at Patimban Port and PLTU Tanjung Jati-B, in this study, hydrodynamic modelling using Delft3D software was carried out based on current data analysis and detection of TSS distribution using Sentinel-2 images temporally by comparing water conditions before and during dredging activities. The results of the calculation of the error value carried out show that Liu's algorithm is the best in estimating the TSS concentration value in the two study areas where the algorithm has Mean Absolute Error (MAE) 3,732 and Root Mean Squared Error (RMSE) 3,987 and coefficient of determination with R2 0.975 for Patimban Port and PLTU Tanjung Jati-B has MAE 10,544 and RMSE 11,404 and coefficient of determination with R2 of 0.853. From the results of monthly TSS model, there is an increase in TSS concentration > 200 mg/L at Patimban Port and an increase in TSS > 100 mg/L at PLTU Tanjung Jati-B due to dredging activities. Sea currents in the Patimban Port area, especially near dredging activities, tend to have a small average current velocity ranging from 0.014 m/s – 0.033 m/s compared to other areas, such as near the coast the average is 0.015 m/s – 0.052 m/s, and offshore average ranges from 0.025 m/s – 0.086 m/s. This is because the dredging area is right in the middle of the bay, so that the current moving towards the bay is well spread in various directions. The pattern of current direction tends to change based on changes in the annual seasons that occur every month. Meanwhile, currents in the PLTU Tanjung Jati-B area, especially near dredging activities, tend to have a large average current velocity ranging from 0.362 m/s – 0.408 m/s compared to other areas, such as near the coast the average is around 0.124 m/s – 0.141. m/s, and the jetty dredging area averaged around 0.282 m/s – 0.321 m/s. Current direction patterns tend not to change every month throughout the year, changes in direction occur due to the influence of monthly tides (spring and neap). Based on the results of variations in the average TSS concentration and current velocity monthly, there is an inverse relationship between the increase in TSS concentration and current velocity both in conditions before and during dredging activities in the two study areas. This is because TSS can be detected well by satellite imagery when the water conditions are calm due to minimum of sediment transport processes by currents so that TSS is well suspended on the surface of the water. Meanwhile, from the results of variations in the average TSS concentration on an annual basis, the concentrations were relatively constant both before and during dredging, 38.3 mg/L and 36.2 mg/L for the Patimban Port area, 30.2 mg/L and 27.4 mg/L for the PLTU Tanjung Jati-B. This proves that the effect of dredging activities in the Patimban Port and PLTU Tanjung Jati-B tends to be small towards changes in the average annual TSS concentration because the TSS generated from dredging activities is not continuous every time but on a scheduled basis.