Kerala: Sand from dams' turns reality

Thiruvananthapuram: Finance minister Dr T.M. Thomas Isaac's much ridiculed 'sand from dams' project has been revived. Mangalam and Chulliyar dams will be the first ones from which silt that has accumulated over the years will be removed. The desiltation of the two dams is being done on a pilot basis. "Besides increasing the storage capacity of dams, the process is also expected to yield enough sand to meet the increased demand for sand in the state," water resources minister Mathew T. Thomas said.

This time, however, the desiltation process will be conducted in a scientific manner. As per the memorandum of understanding signed with National Centre for Earth Science Studies (NCESS), the desiltation process of Chulliyar dam will be completed by March, and that of Mangalam by April. The desilted sediment can be separated into usable components like sand (which can be used for construction) and clay (which can be raw material for brick and tile industries). Before sand and clay are marketed, the quantity of sediment and their components will be first verified. Sub-bottom Profiling will be carried out to first assess the quantity of sediment under the reservoir. This is a method by which the thickness of underwater sediments can be assessed from an instrument mounted on a boat. To identify the components of the sediment deposit, bore samples will be collected and analysed at any state or central government agencies like engineering colleges, NCESS and Kerala Engineering Research Institute.

The sediments will be removed by suction, using desilting pumps. The desilted sediment in slurry form will be separated into usable components like boulder, gravel, sand, clay, silt, and organic matter by using suitable sediment separators. Further, the minister said that since water from most reservoirs was also used for drinking water purposes, steps would be taken to avoid turbidity of the water. "The entire desilting process will be carried out with minimum turbidity caused to the reservoir water and without polluting the water for drinking water supply," the minister said.