Over the years, dredging has emerged as a distinct industry due to growing dredging requirements at Indian ports as well as inland waterways. With the increased dredging activity, draught levels at Indian ports too have increased. Most major ports have achieved a draught of at least 14 metres. In particular, the draught at the Visakhapatnam and Chennai outer harbour ports is 18.1 metres and 17 metres respectively. However, draughts at domestic ports still remain substantially lower than at their international counterparts.
The Indian dredging market is marked by the presence of both public and private sector contractors. The Dredging Corporation of India is the biggest public sector entity while in the private sector Adani Ports and Special Economic Zone Limited (APSEZL) and Dharti Dredging and Infrastructure Limited are the key players (in terms of fleet size).
Besides ports, dredging is also undertaken at national waterways (NWs). The Inland Waterways Authority of India undertakes not only capital dredging but also maintenance dredging for maintaining a pre-decided least assured depth at the three operational waterways – NWs 1, 2 and 3. From 2013-14 to 2016-17, a total of 3.42 million cubic metres (cum) of maintenance dredging was carried out on these NWs.
VOC port perspective
Dredging at V.O. Chidambaranar port is undertaken in the inner harbour basin and the approach channel, up to the availability of natural deep contours. The depth to be dredged is based on weather conditions and the proposed vessel design to be handled at the port.
At present, the port handles vessels of up to 14.2 metre draught with a minimum tidal advantage of 0.65 metres. The depth available in the inner harbour varies from 14.7 metres to 15 metres, and that in the approach channel is 15 metres. The port has proposed increasing its draught to 15.5 metres by 2023 to handle new Panamax vessels (366 metre length overall, 49 metre beam and 15.2 metre draught).
The V.O. Chidambaranar Port Trust (VOCPT) has appointed the National Technology Centre for Ports, Waterways and Coasts (NTCPWC) and the Indian Institute of Technology, Madras, for preparing the detailed project report for a capital dredging project at the port and for preparing the port’s master plan. The NTCPWC has proposed a depth of 16.4 metres in the inner harbour and 17.5 metres in the approach channel to handle 15.5 metre draught vessels with a capacity of 125,000 deadweight tonnage. Further, it has been proposed that dredging works be undertaken in a phased manner. In Phase I (2019-22), 2.2 million cum will be dredged followed by 6.55 million cum in Phase II (2020-23). Thereafter, 2.15 million cum will be dredged by 2023-25.
In the past three years, VOCPT has taken a number of measures to increase draught levels at the port. Prior to 2018, the port calculated the under-keel clearance (static) with reference to the chart datum at the port. At the time, the port had a draught of 14.1 metres and 14.7 metres in the dock basin and channel, respectively, which enabled the port to handle vessels of up to 12.8 metre draught level. In 2018, maintenance dredging at the port resulted in the draught level increasing to 14.5 metres and 15 metres in the dock basin and channel respectively. The key point to be noted is that the vessel draught was increased by adopting the dynamic under-keel clearance technology, instead of undertaking capital dredging, as the latter was more capital intensive.
During the five-year period 2014 to 2018, the traffic handled at APSEZL-owned non-major ports increased from 112 million tonnes (mt) in 2014 to 180 mt in 2018, a compound annual growth rate (CAGR) of 12.59 per cent. The growth was seven times the growth recorded at other non-major ports. The traffic handled at non-major ports (excluding APSEZL-owned ports) increased from 304 mt in 2014 to 314 mt, a CAGR of 0.81 per cent only.
With respect to the dredging segment, APSEZL has a fleet of 16 cutter section dredgers (CSDs) (four for inland dredging), three trailing suction hopper dredgers (TSHDs), one water injection dredger (WID), and two mech-
anical dredgers. It has executed a plethora of capital and maintenance dredging projects. Key capital projects executed were those at the ports of Mundra (77 million cum), Hazira (30 million cum), Dhamra (9 million cum) and Gangavaram (2.4 million cum), and key maintenance dredging works were executed at the ports of Dhamra (8.2 million cum); Southern Naval Command, Cochin; Jaigarh port; and the Jawaharlal Nehru Port Trust (JNPT). Further, the company has executed dredging works in the Farakka-Kahalgaon, Sultanganj-Mahendrapur and Mahendrapur-Barh stretches of NW-1.
APSEZL forayed into the inland dredging segment only in 2019. The two projects which are being executed by the company involve provision of assured least available depth of 3 metres by dredging/bandalling as well as erection and maintenance of navigational aids in the 147 km long Farakka-Kahalgaon stretch of NW-1, and maintenance dredging in the Gogha-Dahej roll-on, roll-off passenger (ro-pax) navigational channel.
Despite the company’s vast experience in the execution of dredging projects, its river dredging projects were affected by their own set of challenges. First, unlike ports, predicting siltation levels in rivers is more challenging. Second, environmental factors such as weather challenges and seasonal changes are not limited only to the local region. Third, studies and investigations have a larger number of factors to cover and are relatively more complex. Finally, safety and security of project-affected people is a major cause for concern on long river stretches.
Going forward, significant growth is expected in the dredging segment. Most of this growth is expected to be driven by the government’s plans to develop new ports and waterways, and modernise existing ports. Further, the government’s ambitious plan of developing 106 new waterways and maintaining the navigational channel of the five existing NWs bodes well for the segment. These initiatives are expected to increase the demand for dredging significantly in the years to come.
Based on presentations by Gundip S. Ahluwalia, Manager, APSEZL, and K. Ravikumar, Chief Engineer, V.O. Chidambaranar Port Trust, at a recent India Infrastructure conference