Even as five of the six components of the Middle Vaitarna Dam built on the Vaitarna river in Thanes Kochle village are behind schedule,the dam component of the much-delayed project has achieved an unlikely feat. Among the 550 roller-compacted concrete (RCC) dams built across the world till date,the Middle Vaitarna dam is the ninth quickest to be built globally and the fourth in Asia,in addition to being Maharashtras tallest dam at 102.4 metres. It is also the fastest in the country in this list. The dam will be the seventh source of water supply to Mumbai,which has a daily requirement of 4,250 million litres as against its current supply of 3,450 million litres. Middle Vaitarna is also the first large dam in India to be built with RCC technology wherein almost half the usage of cement is replaced with fly ash,a byproduct of thermal power-generating plants. For Middle Vaitarna,a total of 12 lakh cubic metres of RCC was used,of which 40 per cent was made up of fly ash from the Eklahare thermal power station in Nashik. The construction was taken up in March 2010 and finished on May 5 this year. Additional Municipal Commissioner Rajiv Jalota said the dam was completed in a record time of 15.5 months of the total project duration of 42 months. We used the RCC technology for the first time and fortunately it was successful and enabled us to complete it much before the expected date, he said. Having managed to finish the construction before monsoon,the BMC will be able to store rainwater after which 455 million litres of extra water will be supplied to Mumbai September 2012 onwards. The Jawaharlal Nehru National Urban Renewal Mission-funded project has cost Rs 2,285 crore,of which Rs 797 crore was spent on the dam alone. When the project was first proposed with a deadline of 2002,the cost was Rs 1,500 crore. RCC technology is fast gaining popularity for dam building across the world since it requires much lesser time in building and is also an environment-friendly technology. Fly ash across thermal power stations in India is being let out in rivers,leading to pollution. But in this method of construction,large portions of fly ash can be used constructively, said a BMC engineer in charge of the dam project. One of the main reasons behind the feat was the success of the test section of the dam. Before any dam is constructed,a small portion is built with the proposed technology on an experimental basis to see if the project will be successful. In many cases,the proposed technology fails,leading to redrawing of plans and indefinite delays. Our test section,carried out on a stretch of 50 m by 12 m was completed in just three months. This gave us tremendous confidence and work was carried out in full swing. As opposed to a conventional cement dam,the RCC laying can be done in layers consecutively without waiting for each layer to dry, said the engineer. However,the other components of the project,such as the water treatment plant in Bhandup and laying of pipelines from the dam to the city,are lagging behind schedule.
