Dredging consultants from a consortium of Dutch companies including Royal IHC (IHC), Deltares and NETICS have prepared a full-scale pilot project to implement a circular sediment management plan for reservoir dredging in India. Sediment removal by dredging is seen as a costly process. However, IHC’s approach shows that costs can be reduced significantly and additional revenue can be generated by reusing the dredged sediments instead of disposing of them as a waste product.

Reservoirs all over the world, mostly used for water supply or power generation, often face the problem of sedimentation, which results in dam instability and loss of storage capacity. India has more than 5,000 large dams registered and the impact of reservoir sedimentation is significant. Sediment management is therefore of crucial importance.

For the majority of dams that have been clogged up during the past decades, the active removal of sediment from these reservoirs by dredging has not yet been seen as an economic solution to regain capacity. This project aims to show local dam owners that dredging is a cost-effective and sustainable solution to improve and maintain the storage capacity and efficiency of their reservoirs.

The preparation

In recent months, IHC’s dredging consultants, together with experts from Deltares and NETICS, have developed an integrated project plan on circular sediment management in reservoirs. The preparation of the dredging works included modelling and analysis of the morphological behaviour of the particular reservoir. This involved mapping out the sedimentation process within it and identifying the most useful places to dredge and was carried out by Deltares.

NETICS gave advice on reusing dredged material, and shared environmentally-friendly sediment handling techniques, as well as innovative processes and their applications on reusing sediments. Most reservoirs contain sand that can be sold as clean construction sand. Furthermore, the dredged material can be hardened with the use of additives and utilised for building purposes.

Within this project, so-called geotextile tubes filled with dredged material will be placed at designated areas downstream to reinforce the embankment and protect it against erosion. These geotextile tubes enable quick dewatering of the material, and can also be laid in the reservoir to control the current and reduce future siltation or restore eroded banks.

The right equipment

Alongside its project management role, IHC has supplied the necessary dredging equipment – a submersible dredge unit. For this project, the IHC TT-pump will be lowered via a cable and operated from a pontoon with A-frame. Dredged material will then be transported to the desired location into the geotextile tubes. The material will be dewatered by the geotextile tubes within several weeks. After dewatering, the soil can be prepared for reuse according to local needs. Dredging itself will be executed by a local contractor.

This month, the preparation phase has been completed, and the equipment has been tested at the sub contractor’s yard in Mumbai and is now being transported to Dehradun in northern India. Now the dredging works in a reservoir of Uttarakhand Jal Vidyut Nigam Limited can finally start.

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