Dredging activities have a significant impact on the environment along the coasts and rivers. It includes changes in the coastal and river morphology, changes in currents and wave climate, changes in coastal defence, erosion along the coastline and impact on water quality and marine fauna. It is therefore essential to undertake appropriate management of dredged material in order to prevent harsh environmental outcomes, thereby improving sustainability.
Handling of dredged materials in India
One of the key highlights of the Dredging Guidelines for Major Ports, 2021, is the adoption of the environmental code of practice for dredging and reuse/recycling of dredged material. Its ultimate aim is to shift to sustainable dredging activities. As per the guidelines, environment-friendly dredging is expected to be a permanent element in dredging projects. To this end, the identification of dredging projects with the most appropriate disposal option for dredged material is critical for a duration of up to 10 years (2020-30).
The Ministry of Ports Shipping and Waterways is working towards achieving the goals laid under the “Waste-to-Wealth” initiative. The aim is to use the dredged material as a resource rather than as waste to be disposed offshore. The dredged material should be taken up for recycling and reuse based on scientific studies. This will enable a sustainable dredging disposal mechanism and promote waste-to-wealth.
In a notable development, on September 15, 2021, Dredging Corporation of India Limited established a modern “soil lab” to help assess the quality of dredged material at project sites. It is a step in the right direction and in line with the Maritime India Vision 2030. It aims to turn waste into wealth by recycling dredged material for reuse, which is being dumped in the sea. In October 2021, the Water Resources Department, Government of Andhra Pradesh, commenced dredging works along the upstream section of the Krishna river at Vijayawada in southern India. The dredged material will be utilised by the state government for construction and other engineering purposes.
A few major ports have made efforts to reuse dredged material. In this regard, at Visakhapatnam port, more than 60 per cent of the dredged material from the outer harbour is used for beach nourishment while the rest is disposed of in the open sea. Further, the Jawaharlal Nehru Port Trust has been using part of the dredged material for beach nourishment. The initiative of the Cochin Port Trust is a good example where the authorities have been able to earn revenue through the auction of dredged material. Meanwhile, Paradip port has been utilising 1 million cubic metres of dredged material for the reclamation of land for Numaligarh Refinery Limited. In Ennore port, capital dredged material has been used to mitigate rift erosion. the Kolkata Port Trust is also planning on collaborating with dredging partners to identify and build a port-wise strategy and roadmap for the recycling and reuse of dredged material.
The road ahead
Dredged material has many potential environment-friendly applications. These include land reclamation, creation, and improvement; expansion of beach size; protection and nourishment of beaches, dykes and dams; capping of contaminated dredged material; aquaculture; and use as replacement fills, construction material and topsoil.
There is still a long way to go for Indian ports to ensure that dredged material is optimally handled and utilised. The Dredging Guidelines for Major Ports, 2021, state that the detailed project report (DPR) should include a provision for recycling/reuse/disposal of dredged material. It should include an assessment of the physical and chemical characteristics of the soil, toxic contaminants present, possible re-use/recycling options, technical analysis of alternative uses, identification of the use/disposal site, applicable model studies to assess the impact of disposal or reuse of the dredged material, benefits of the reuse of dredged material, techno-economic evaluation of reuse options and dredging equipment options. In case the dredged material is proposed to be disposed of in the sea due to non-suitability of the material, a detailed justification specifying reasons for not utilising the dredged material comprising options considered and cost-benefit analysis including the environmental cost will be required in the DPR.
Going forward, the efficient management of dredged material lies in the development of a dredged material management strategy, which includes a long-term management plan. There should also be an appropriate classification of the dredged material based on its characteristics and expected environmental impact. The financial aspect of material handling solutions also needs to be studied to ensure that the provisions are sustainable in the long run.