Operations disrupted after tunnel boring machine breaks down

A group of mechanical engineers, specially brought from Italy, have successfully repaired the Tunnel Boring Machine (TBM) purchased from a US firm - Robins for Rs.120 crore for the gigantic Veligonda, a project taken up to benefit the vast fluoride- affected areas in Prakasam, Kadapa and Nellore districts.

It’s like acquiring a new asset worth that much. The gargantuan machine on rails that resembles a long goods wagon and moves inch by inch, boring holes sideways, is most sought-after device in the whole world for excavating tunnels of massive diameter, substituting the time-consuming and hazard-prone manual blasting method.

The TBM was damaged when a portion of the roof of the tunnel it was drilling, collapsed on it. By then, it had completed eight km of one of the twin tunnels, planned for Veligonda each with 18-km length to draw 53 tmcft of water from Srisailam reservoir lying 40 km away during the flood season (July-October). This tunnel is of seven metre diameter. The 40-km stretch will be covered by a gravitation canal partially linked to the tunnels. The government had lost every hope of restoring the machine as repeated attempts earlier by site engineers to rectify it turned futile. After overhauling, the TBM is being pressed into service in two days, says V. Veeraju, Chief Engineer, Irrigation, Prakasam. A second 9.2- metre diameter tunnel is similarly completed for 7.5 km using a bigger TBM (cost Rs.150 crore). Conceived by K. Sriramakrishnaiah, Irrigation adviser to NTR and named after Poola Subbaiah, a communist leader who fought for such a project as a permanent solution to fluoride-affected areas, was finally taken up under Jalayagnam.

Planned at a cost of Rs.5,150 crore to irrigate 4.5 lakh acres in the three districts and provide drinking water to 15.25 lakh population in 30 affected mandals, Veligonda is expected to change crop pattern in the area. Interestingly, a 40-sq km area surrounded by hills at Veligonda will be converted into the project’s reservoir filled with Srisailam water. Three imposing dams have been built as part of the project at Sunkesula, Gottipadia and Kakarla to fill the gaps between hills. Sixty per cent of Veligonda into which a sum of Rs.3,148 crore has been pumped so far, is completed.