Loss of the internal density of a dam structure should be predominantly seen as a factor for deciding the deterioration in its total strength, argues M. Sasidharan, retired chief engineer and an expert on dam safety.

Presenting a paper on `Mullaperiyar dam: Anxieties and solutions,'' organised by the Idukki District Library Council here on Sunday, Mr. Sasidharan said that the Mullaperiyar dam's present condition involves two factors - construction using lime surki and rocks, when the technology of dam construction was at an infant stage - and later strengthened by concrete material at the advanced stage of technology. Though there are specific criteria to decide on the present condition of a dam, this was not possible due to the combination of two basic materials used for concreting a single structure.

According to him, the lime-effect that provided the concreting effect for the dam has considerably lost in the form of seepages of various intensity. While the strong rocks could not be in effect deteriorating its strength, the material used for this, the lime surki has lost its concreting effect.

Mr. Sasidharan said that it was not true in the case of concrete as there was basicaly zero-losing of its deterioration in the strength. While there is the technology of deciding loss of strength in major construction over the passage of time using the cement structure, ``nowhere in the world, there is any measure to judge the loss of strength constructed by a lime surki material.

He said that in the United State alone, of the 75,000 dams of various sizes and nature, about 300 dams of small and medium sizes were either dismantled or de-commissioned. This was done as dams throughout its life retain great pressure and simply every engineer knows that ``water has one job and that is to get past anything its way.''

More than the issue of water disputes between two States, the technology and the age of a dam makes it an aspect for whether keeping a man-made dam or de-commissioning it, he said and added that the completion of a new dam needs seven to eight years.

Experts on Mullaperiyar dam, political leaders and the Chairman of Mullaperiyar Samara Samithy spoke at the seminar.