Ghatghar Hydel project snippets

A few weeks from now, two gigantic turbines at the bottom of a tunnel carved out of a hill at Ghatghar on the Mumbai-Nashik highway will chug to life to generate 250 mw of electricity. It will mark the completion of a titanic project that tested human grit and endurance.Ghatghar dam, where the hydro project is located, is incidentally the 10th fastest constructed dam in the world and the first in the country to have used fly ash generated from thermal power projects, unlike the traditional method that uses cement. Fly ash is converted into roller compacted concrete (RCC). As of now, some 400 dams of this kind are under construction throughout the world.The RCC method involves placing the concrete on a continuous basis, in layers of 300 mm thickness. Simultaneously, the vibrating roller does the compacting. With the RCC technology, the whole dam can be constructed layer upon layer. “The whole dam was ready in flat 376 days,” said VC Shelke, who is now chief engineer at Koyna, but who was associated with the project from the start.The project is unique in every sense. It has three dams: the Upper Dam, the Lower Dam and the Saddle Dam. The magnitude of work can be judged by the fact that the Lower Dam alone consumed approximately 6.5 lakh cubic metres of concrete. “All the three dams have been interconnected through mega tunnels. This was really a humongous task as it involved piercing the hard rock of the hill. The work on these tunnels was started simultaneously at four different places and was completed with precision. All the tunnels met at a desired location, as planned. It’s quite a remarkable engineering feat,” deputy engineer VM Yevale said. So water from the upper dam will be brought down to generate power, and will then be stored in the lower dam. The saddle dam has been provided, considering the speed with which the water gushes down with gravitational force.The beauty of the project is that water will be pumped back to the Upper Dam during the day after using it for generating electricity, as against other hydel projects. At the bottom of one of the tunnels, two giant turbines will produce 125 mw each. “The turbines are reversible. They rotate to generate power. Turn them anti-clockwise and they act as a pump,” said Vivek Patil, one of the sectional engineers at the project. “The whole system can reach its peak within 60 seconds,” stated Dnyaneshwar Shur, sectional engineer. The power generator will not be run at the base load; meaning, electricity will be produced only during peak hours, typically between 7 pm and 10 pm everyday.Of the Rs 1,200-crore investment in the project, Rs 400 crore came in from the Japanese Bank of India Co-operation, another Rs 400 crore from the Power Finance Corporation, and the remaining from the Maharashtra government.