A study on the toxic nature of the sediments in the Cooum river is being conducted by the Chennai River Restoration Trust.

The study is to take preventive measures on any possible impact on human health during dredging. The Trust has collected samples from various points across the stretch of the river for conducting the study and the results are expected shortly.

The dredging is an important component of the river restoration as a chunk of the pollutants is trapped in around 90 lakh cubic metre of its sediments. The study is likely to throw light on the heavy metals and disease-causing microorganisms in the sediments, according to officials with the project.

The CRRT is not likely to opt for burying the sediments in deep seabed as it would be expensive.

Under the Singapore River cleaning model, on which the Cooum river restoration project is based, the sediments were, however, buried in deep seabed.

CRRT is planning to find a cheaper alternative for removing the polluted sediments without harming the environment.

The clearing of the mouth of the Cooum is under way and is expected to remove 900 cubic metres of marine sediments every day caused because of littoral drift. This is expected to restore the tidal influence up to Chetpet and would be a stepping stone for restoration of various species of fishes in the river ecosystem.

The removal of 2.6 lakh cubic metre of sand accumulated in the river mouth would be done in two years. However, the restoration would be sustainable only after polluted sediments inside the river are removed at least to a depth of three feet, according to officials.

Leaving the sediments in the Chennai Corporation's dumping grounds in Perungudi or Kodungaiyur is not possible as the sediments are not classified as solid waste. The dredging work would begin after the CRRT chalks out a strategy for dumping the polluted sediments safely.

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Aloysius Xavier LopezJune 28, 2012