Call for a substitute to river sand in construction 1st January 2002�Seminar organised by the Geology Old Students' Association, University of Kerala (GOSAN), highlighted the need for alternative materials in the construction industry to substitute river sand.

Presiding over the seminar, the Vice-Chancellor, B. Ekbal, called for the development of appropriate housing technology using environment-friendly materials. He underlined the need for a radical change in the housing culture by avoiding wasteful spending on costly and scarce resources. He said it was necessary to educate the people on the feasibility of alternative construction materials.

The District Collector, K.R. Jyothilal, who inaugurated the seminar said the administration was finding it difficult to enforce the High Court restrictions on extraction of river sand due to the pressure exerted by powerful lobbies. He said unauthorised sand mining was rampant along the Vamanapuram and Karamana rivers.

Mr. Jyothilal suggested that river management committees work in close coordination with gram panchayats for regulated extraction of sand from specific locations. He said crushed rock was a viable alternative to river sand. ``Development of substitute materials should be part of the strategy to minimise the requirement of river sand for the construction industry. This can be achieved only by improving the interface between industry and research institutions,'' he said.

The chairman of the Science, Technology and Environment Committee, M.R. Das, and the GOSAN president, K.P. Thrivikramji, also addressed the inaugural function.

In a paper presented at the technical session, M.B. Raju and E. Shaji of the Central Ground Water Board, said that indiscriminate sand mining was responsible for the water crisis in many parts of the State during summer months. They said the removal of sand from river beds had increased the base flow of ground water to the rivers.

The paper pointed out that sand mining from river beds was also responsible for sea water intrusion through backwaters and river mouths. Due to unscientific mining, sufficient quantity of sand does not reach the river mouth or estuaries to make natural barriers along the coast. Due to this, sea water and sea sand enter the backwaters and rivers.

Citing case studies, the paper observed that the Paravur lake was filling up with sea sand while wells in the proximity were subject to saline intrusion. Sand mining from the Periyar river had led to sea water ingress. The paper suggested desiltation of all irrigation ponds and percolation tanks which would contribute a considerable amount of sand.

In his presentation, P.T. Chacko of the Department of Geology called for setting up a dynamic sand inventory with a regional machinery for planning and monitoring of exploitation. He suggested that the inventory with a digital, geo-coded or GIS system could be set up with a part of the fund raised by sale of sand. Mr. Chacko advocated a river basin approach to sustainable exploitation of river sand.

A.S.K. Nair of the Centre for Earth Science Studies proposed a process-response model which includes assessment and availability of sand on a micro watershed basis with people's committees and NGOs to enforce regulated mining. He said it was important to examine sand mining on an integrated approach examining the scientific, socio-economic and political aspects of the problem.

Many of the speakers said crushed rock was emerging as an acceptable alternative to river sand in the construction industry.

When Pemagatsel became a separate dzongkhag, development activities began to pick up momentum. The construction of roads and other infrastructure meant increased demand for natural resources like stone,

gravel and sand, among others. With no major river in nearby, river-bed sand has never been readily availability or reasonably affordable, thus escalating the cost of construction.

At minor constructions like roadside drains and retaining walls, transporting river-bed sand all the way from Samdrup Jongkhar has proven too difficult. This has forced government agencies, contractors and even project DANTAK to seek an alternative to sand.

In Pemagatshel, there is an alternative, one that is commonly called Monglin Aggregate. This fine powdery gravel, in its natural form, has been in use right from the time of the introduction of development activities in the dzongkhag. The quarry is located in Monglin, about eight kms away from the Pemagatshel proper.

“People were mining this fine gravel as far as I can remember,” said Samten Chhofel, a contractor residing in a nearby village. Today, this gravel is also known as “Chhofel Aggregate” because of the fact that he has been supplying it since the late 1990’s.

“If sieved properly, it can be used even for the superstructure although its long term durability is not known,” said Samten Chhofel, pointing to a section of his house with walls built using the fine stone aggregate.

He even claims that the local aggregate requires less cement to sand ratio. Further down the road, a workshop owner, Wangchuk, also maintains that the concrete works best when used with less cement. He went a step further by saying that the concrete mix also sets faster compared to the ones using river-bed sand.

Gurung, a DOR engineer, said that while the fine local stone aggregate can be used for the construction of drains, retaining walls and PCC works, it is not recommended for other structural works. “The field testing lab of the department has approved the use of it for works other than structural ones.” He however disagreed with the ratio of the mix. “Contrary to what the people claim, more cement needs to be used if it is used as ersatz sand,” he said.

A visit to the source reveals the extent of its use over the years. It looks like a mini mine minus man and machineries. It comes to life only when there is demand from contractors. While the forestry division issues need-based permits, many prefer buying from Samten Chhofel who keeps ready labour.

Today, this fine aggregate which can be extracted without much effort, is a boon for local contractors. The entire roadside drain along the dzongkhag highway has been built using the local sand. It has, in fact, been so widely used in construction works that many attribute the cut-throat competition among contractors to the locally available cheap alternative to sand and aggregate.

A truck load of river-bed sand from Samdrup Jongkhar costs more than Nu 5,000, including transportation up to Pemagatsel. The local fine stone aggregate or powder is available for anywhere between Nu 1,500-2,000 within the locality, including transportation.

Graded aggregates, however, cost more because of the extra work involved. It is still much cheaper than what is available at Samdrup Jongkhar. A cubic foot of graded aggregate which costs more than Nu 20 in the border town is far cheaper in Pemagatshel. With the new township at Denchi likely to come up soon, the demand for Monglin/ Chhofel aggregate is likely to skyrocket. The eminent demand has made Samten Chhofel initiate plans to go into fulltime mining of the stone aggregates. His name is already a brand.

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