Pure sand extraction from Aruvikkara unviable: expert

A total separation of sand from the sand-silt-clay mixture that would soon be extracted from a one-acre site in the reservoir of the Aruvikkara dam would be prohibitively expensive and, as such, it would be advisable to sell a purified sand-silt mixture according to an expert working on a pilot project for sand extraction.Sand samples taken from a couple of spots in the reservoir have revealed a very low presence of clay. Seventy to eighty per cent of the mixture excavated would be a sand-silt combination, the special officer, Laurie Baker International School of Architecture, Nirmithi Kendra P.R. Sreemahadevan Pillai told The Hindu here on Sunday.Organic deposits are likely to be found only till a depth of about 30 cm. Once this is removed, the extraction can be done. A good portion of the clay can be washed away during the time of extraction itself, Dr. Pillai explained. The resultant mixture can then be further refined using a specially designed, hand-operated rotary sieve which would remove clay conglomerates and gravel.

“What we would then get is a sand-silt combination that can be used straightaway for construction purposes. This mixture would do neither good nor harm if used for construction. Anyway this would be much better than using quarry dust as is being done in many places,” Dr. Pillai said. The clay that is washed away during extraction would initially make the water inside the extraction site turbid. However, this water would not pose a problem for the reservoir as the site would be cordoned off by a bund.Once the clay particles settle in the water in the site, the bund can be cut open.Though during the manual extraction process the depth reached would only be about 1.5 metres, sand can be taken from the reservoir from up to 5 metres deep, Dr. Pillai pointed out. However, even large scale extraction of sand from Aruvikkara would only be able to partially meet the sand requirements in Thiruvananthapuram district. “The lasting solution for sand scarcity would be for the State to turn to non-cement, non-concrete constructions and to look at alternatives like the wood of the coconut tree,” he added.

The Hindu, November 9th , 2009