[1]The Kerala-Tamil Nadu row over the 116-year-old dam at Mullaperiyar has reached a flashpoint, with disturbing reports coming in from border villages. DC presents the arguments, both for and against the aged lime-and-surkhi structure.
Arguments by Mr M.K. Parameswaran Nair, head of Kerala Special Cell on Mullaperiyar Vs Dr K.C. Thomas, former chairman of the Central Water Commission:
Government panel: Constructed in 1895-97 when dam technology was in its infancy, dam suffers from design and construction aspects. Its hearting is lime surkhi concrete with 3.125 parts stone and 1 part mortar. It’s a composite gravity dam, which cannot be classified as a homogenous gravity dam, liable to theoretical analysis using current standards.
Thomas: The fact the dam, constructed in 1895 (infancy technology), is still (2011) standing safely is proof enough that the design technology as also the construction technique then adopted were good and sound. The strengthening done in 1980-81 has made it conform to modern standards. It’s safe against all envisaged eventualities.
Panel: Morvi dam disaster in 1979 created serious concern among engineers and people about inadequacies of spillways of dams’ in India. People are very much apprehensive about the possible occurrence of a cascading disaster like Morvi.
Thomas: Morvi was manmade. The people in charge failed to open the spillway gate as the inflow of flood kept on raising the reservoir level till it overtopped the dam and breached the earth and abutment. Mullaperiyar is not an earth dam and cannot fail abruptly to cause any downstream damage.
Panel: Continuous leaching may have washed out quantities of cementing material leaving hollows in the structure which may eventually weaken the dam. Dam has become heterogeneous.
Thomas: No cement grouting of surkhi core was done in Mullaperiyar dam and there were no hollows in the dam when CWC chairman visited the dam in 1979.
Panel: Pre-1986 dam safety analysis values were arbitrarily supplied by TN and unreliable. The inner core density could be much lower than the value of 135 lb/ cft assumed by CWC. Seepages and opened cavities must be naturally more in lower depths below 104 ft, the silt level of the tunnel. No effective curative work had been carried out as the water level in the reservoir cannot go below 104 ft.
Thomas: How much lower than 135 lb/cb ft and on what authority? Weep-holes and foundation drainage gallery were techniques introduced by US in 1940-60. No dam in India constructed prior to 1930 has a drainage gallery. Seepage if any is measured in catch-water drains downstream of the toe of the dam. Such drains did exist at the toe of Mullaperiyar dam and the seepage was being measured by V-notch gauge when the CWC chairman visited the dam in June 1979
Panel: For lowering the spillway crest level from +142 ft to + 136 ft, blasting was done near the already existing dam. Vibrations of such blasts might have adversely affected the strength of the dam.
Thomas: No massive blasting was done. Even most recent inspection by the chief engineering Kerala PWD (irrigation) has reported no cracks? The 10-m concrete backing has been made integral with old masonry dam with shear keys and concrete grouting; no separation or slippage along the contact phase has been detected. Thickened dam is stronger.
Panel: Mullaperiyar cannot be analyzed by the standard gravity dam method analysis as it is not a homogenous structure.
Thomas: No dam in the world constructed prior to 1940 had a drainage gallery. Old dams without any drainage provisions are functioning satisfactorily even today.
Panel: A study by Dr Bhaba and Prof R N Iyengar had indicated that dam is unsafe. Prof Iyengar adopted a value of 0.16 g (considering the Uttarkashi earthquake) and 0.4738 g (considering Koyna earthquake) for values of seismic acceleration considering the possibility of similar earthquakes to happen in Mullaperiyar region.
Dr D.K. Paul of earthquake engineering department IIT Roorkee identified 22 major faults in a radius of 300 km around Mullaperiyar site. Thekkady-Kodaivannalur fault line potentially the most devastating.
The fault is capable of producing an earthquake of 6.5 magnitude on Richter scale within a close distance of 16 km of the dam site.
Thomas: What is the justification for Prof Iyengar to apply such abnormal values as 0.16 g and 0.4738 g for stability analysis of the dam when it is not in an earthquake zone? CWC never made any reference to Dr Bhabha or Prof Iyengar to analyze the stability of the dam.
IIT Roorkee earthquake engineering dept does not have the equipment to determine quake resistance of any proposed cross-section of the dam.
US geological survey had conducted extensive studies to see whether they can predict in advance when an earthquake will occur of what magnitude and what advance action can be taken to mitigate the damage.
One should rely on the fact that no dam in the world has failed due to earthquake.
There has never been a previous report of 22 or any similar number of fault lines on the Mullaperiyar dam. If they do actually exist, the dam should have received many shocks in the last 116 years and produced some damage, however small or superficial.
Panel: The only permanent solution to the long pending vexing problem is construction of a New Dam to replace the old unsafe Mullaperiyar dam. Government of Kerala has already put forward this suggestion during the meetings held at New Delhi chaired by the Union Minister for water resources and the Chief Ministers of Kerala and Tamil Nadu.
Also the solution of constructing a new dam has been put forth for the first time before the Supreme Court by the Kerala Government while defending the case filed by Tamil Nadu.
Thomas: If the Kerala Government decides that the construction of a new dam is the only permanent solution to this long pending vexing problem, who is to approve this proposition and who is to execute it at whose cost etc. In fact it is a vexing problem to Kerala only. Tamil Nadu does not see any problem. They are keen to preserve the existing dam.
Panel: As early as in 1979, the team of engineers headed by the then Chairman CWC had made specific recommendation for constructing a new dam as a permanent solution to the problem.
Thomas: The Chairman CWC did not make any recommendation for constructing a new dam. In fact he refused to accommodate this demand. He said that the existing dam was safe as it was but would recommend strengthening it to modern standards to totally remove any apprehensions of its failure.
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