1.0 Brief Summary of the Project

The Mullaperiyar is situated in of State. The construction of dam was completed in 1895 and now the age of dam is 123 years. The structure has already outlived its safe-life, and now it has become unsafe to retain it further. To overcome a panic situation, the State of Kerala decided to construct a new dam just 366 m below the old dam, after carrying out the necessary surveys and investigations, across the Mullaperiyar River. The old dam is now having a water spread area of 3475.78 Hectares. By constructing the new dam the additional area downstream of old dam going to be submerged is only 22.23 Hectares. The total area required for the entire construction purposes, toe protection zone, etc. including this new water spread area is only 50 Hectares (0.5 sq km).

The State of Kerala is now submitting the Form-1, Brief summary of the report, PFR and Proposed Terms of Reference for prior Environment Clearance of the new dam at Mullaperiyar. The relevant facts regarding the old Mullaperiyar dam and the proposed new dam area are depicted below.

History of the Old dam:-

The Old Mullaperiyar dam is a composite gravity structure having a height of 47.24m above the river bed level and a length of 366m. The front and rear faces of the dam are built with uncoursed rubble masonry in lime- surkhi combination mortar. The core which accounts for more than 60% of the volume of the dam is constructed of lime surkhi concrete. The dam was built at a time when dam engineering was at its infancy and many of the major technical and construction requirements applicable to modern gravity were not followed in its design and construction. Effect of uplift and seismic forces were not considered in the design. No drainage gallery and scour sluices were provided. The dam was constructed as one long continuous monolith without any construction joints. No contraction joints were also provided. No instruments were embedded in the body of the dam to monitor its behavior and performance over the years. Seepage of water started appearing right from the first filling of the dam. Measures like guniting the upstream face of the dam and grouting the body of the dam were resorted, to check the seepage, during 1935 and 1961. Subsequent to large scale leakages from the dam in late seventies, approached Government of and apprised them of the grave situation. In 1979, a team headed by the chairman CWC visited the dam and suggested various strengthening measures. During 1980 strengthening measures like cable anchoring, providing reinforced concrete capping, plain cement concrete backing, etc were carried out. The spillway capacity was increased to negotiate the floods and FRL was reduced to + 136 feet to reduce the load on the dam. As a long term measure, the committee also suggested to construct a new dam as a permanent measure. The team after inspection also approved an alignment 1300 feet downstream of the existing dam.

Necessity of the New dam:-

In spite of the above strengthening measures the dam has not gained adequate strength to function further, because of the limitations of the process and materials adopted at that period of time. More over a dam cannot be perpetually made fit to withstand the forces for which it is originally designed through a process of periodical strengthening. Aging is a non retrievable process especially for a dam which is in continuous contact with water and leads to the easily soluble lime to be leached out. The century old Mullaperiyar dam has already outlived its useful life and consequences of any failure of this dam could be catastrophic and its outcome beyond all human imagination. Moreover Mullaperiyar region is an area where significant tectonics activity has taken place in the past. Evidence of recent tectonics is also noticed in the region. The recent earthquakes in Kerala and other parts of the country indicate an increase in the level of crustal disturbances in the form of earth tremors. In this background State of Kerala decided to ascertain the safety of the old dam as per modern standards. IIT Delhi was entrusted with the task of evaluating the hydrological safety and IIT Roorkee was entrusted with task of evaluating the structural safety to probable earthquakes. Both the studies have brought out the fact that the old dam is hydrologically and structurally unsafe to withstand the impact of Probable Maximum Flood and Probable earthquake. Idukki Hydro electric project is existing downstream of the Mullaperiyar dam. The collapse of the old dam will trigger a cascading failure of the Idukki group of dam (viz Idukki, Cheruthoni and Kulamavu) resulting a unimaginable degree of devastation in the thickly populated districts of Idukki and Ernakulam and also in parts of Kottayam, Trissur, Pathanamthitta and Alappuzha districts. Studies have brought out the fact that Idukki reservoir cannot accommodate the water retained by the Mullaperiyar dam. In view of the definite conclusions of the scientific studies conducted by National Institutions of repute and the persistent threat which the dam poses, it is imperative that the present old Mullaperiyar dam needs urgent decommissioning for discharging the responsibility of the State to protect the lives and properties of its citizens. From 1895 onwards, State of is utilizing the waters of Mullaperiyar dam for irrigation and drinking water requirements. State of Kerala does not desire to deprive Tamil Nadu of the Mullaperiyar waters on which their needy farmers are greatly dependent. State of Kerala has taken a decision to build a new dam downstream of the present Mullaperiyar dam only to achieve the twin goals of protecting the lives and properties of its people and for ensuring continued supply of water to Tamil Nadu.

The centre line of the proposed alignment is oriented at about 5°E of N. The structure is proposed to be constructed with main dam and saddle dam on the left flank. The right bank end of main dam lies at latitude 9°31’48’’N & longitude 77° 08’33’’E. The salient features of the new dam are enclosed. The concept of dam safety has changed over the years due to perceived danger from natural hazards like earthquakes. Advances in technology and analytical methods together with improved seismic data base have enabled scientists and engineers to make better assessment of the dam safety. All over the world, safety of dams are being reviewed as per modern standards and hundreds of dams have already been dismantled considering the safety aspects of human life and property.

In developed countries like USA, UK, Canada and Australia it has become common practice to replace old unsafe dams by new dams designed and constructed as per modern standards. Rebuilding of a new dam upstream side of the old Victoria Dam in Australia in 1991 is one such example.

Present status:

Since the New Mullaperiyar Dam site area lies inside Tiger Reserve area, survey and investigations were carried out after obtaining permission from the Standing Committee of National Board for Wildlife. The permission for the same was obtained in the 31st meeting of the Standing Committee held on 12 &13-08-2014.

Based on the surveys and investigations carried out, the design of the dam and DPR preparations were carried out. For obtaining land for the construction of the project, Forest Clearance and Environmental Clearance are required. As part of obtaining Environmental Clearance, it was essential to carry out Environmental Impact Assessment study. For the study, firms having accreditation with Quality Council of India were contacted and M/s Pragathi Labs and Consultants Pvt. Ltd. of Hyderabad came forward to take up the work. Government of Kerala accorded sanction for the work entrusting the work to M/s Pragathi Labs. Since the firm requires NOC from Forest Department for starting the study, the proposals for the same were prepared and forwarded to MOEF&CC through Forest Department and Government.

Kind attention is also invited to the Honourable judgment dated May 07, 2014 regarding Mullaperiyar case. In the rulings of the Apex court it has been granted liberty to the State of Tamil Nadu and Kerala to apply to the Court , if they arrive at some amicable solution on either of the two alternatives suggested by the Empowered committee i.e. construction of new dam or digging a new tunnel.

Based on all the above recommendations, Government of Kerala decided to go ahead with the study and as the firm i.e. Pragathi Labs & Consultants Private Limited was willing to take up the study at the already agreed terms and conditions the proposal for approval of TOR has been prepared and the same are enclosed.