Dredging as an activity has grown in importance in the recent past due to the expansion of existing ports as well as the creation of new ones. Over the years, the industry has witnessed several developments, driven by various factors such environmental concerns, increasing ship sizes, the large scale of port development projects, among others. Dredging primarily involves two types of techniques, namely, mechanical dredging and hydraulic dredging. More recently, the industry has moved towards hydraulic dredging, making use of dredgers such as plain suction dredgers, cutter suction dredgers (CSDs) and dust-pan hydraulic dredgers.
History and background
The history of primitive harbour dredging dates back to 4000 BC, when the Pyramids were built. However, dredging picked up after 1500 BC due to increasing European sea trade. Mud mills were deployed around 1857, and were used for digging activities at ports. These mud mills were later replaced by the steam-driven bucket dredger. The first suction dredger, the General Moultrie, was designed in 1857 in the US, with a hopper capacity of 118 cubic metres (cum). The dredger was equipped with a single 47 cm diameter suction pipe and a deck-mounted centrifugal pump.
Later, major dredging projects across the world stimulated the development and construction of new dredging equipment. One of the most crucial events during this development was the construction of the Suez Canal between 1859 and 1869, where suction dredgers were deployed. Towards the end of the nineteenth century, CSDs started being deployed for undertaking dredging works. By the beginning of the twentieth century, primarily mechanical equipment, such as grab dredgers and bucket ladder dredgers, began to be deployed for port construction projects. After the Second World War (1939-45), hydraulic dredgers gradually took over the role of manual equipment.
A key growth driver in the dredging industry has been the increasing global population. Several developments have taken place in the dredging industry to meet the changing demand of this expanding population. Some examples are the increase in dredging requirements in the Persian Gulf due to the oil and gas boom in the 1970s, development of new land masses in the Far East region of Hong Kong and Singapore, and the development of new offshore islands in the Middle East, among others.
Besides, developments in dredging techniques have been driven by the need for project optimisation. In the case of dredging, optimisation plays a crucial role due to the capital-intensive nature of the industry. Optimisation not only helps the project developer in reducing costs but also in ensuring timely delivery. At present, a number of international dredging companies, in collaboration with builders and researchers, have set up research and development (R&D) facilities aimed at increasing efficiency of equipment. More recently, R&D has also been driven by the need to meet the environmental requirements and optimise fuel costs.
Over time, there has been a shift away from mechanical dredging towards hydraulic dredging. More advanced hydraulic dredgers such as CSDs and trailing suction hopper dredgers are being deployed for undertaking dredging works at ports and inland waterways. Going forward, Indian dredging companies, while learning from their international counterparts, should collaborate with contractors and other stakeholders to ensure deployment of more advanced dredging techniques and equipment and undertake R&D activities.
Based on a presentation by Captain Rajesh Malhotra, Consultant, Dredging Solutions, at a recent India Infrastructure conference