Design of tunnel for Upper Tamakoshi changed

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    KATHMANDU, July 23

    Upper-Tamakoshi-Access-TunnelThree and half kilometer (km) section out of the 16-km main tunnel of the Upper Tamakoshi Hydropower Limited (UTKHPL) has become useless as weak rocks were found during the digging process.

    UTKHPL is now preparing to change design of the tunnel after the Norwegian consultant Norconsult AS pointed that the power house can suffer huge loss due to this tunnel. It will raise the project cost by over Rs 1 billion. The design of 3.5-km section out of the five-km stretch between Penstock Audit to Bhainse Audit is being changed. An audit tunnel and a 260-m shaft have to be dug for that. The preliminary report of Norconsult states that the project, which is already six months behind the schedule of 2015 end due to various reasons, will be delayed by another year due to the problem. Only half of the project has been completed till date. UTKHPL, which has been prioritized as a national pride project, will lose around Rs 15 billion due to lost opportunity to sell electricity produced if it is delayed by one and half years.

    A UTKHPL official revealed that discussions are being held to reduce the estimated cost proposed by the consultant. He said discussions are on to formulate a new schedule by reducing even the proposed estimated time. Additional study has to be done after changing the design of tunnel. Spokesperson of UTKHPL Ganesh Neupane said the consultant has started homework for changing the design a month ago and is currently examining the tunnel. The design of tunnel, that was originally oblique, will now be straight. UTKHPL has also started consultancy with international experts to solve this problem.

    The main tunnel is currently being constructed with a 0.8 percent slope as per the detailed project report (DPR) of the project. The remaining tunnel will be constructed in 0.3 percent slope, according to the changed design. A 260-m vertical penstock shaft has to be constructed while reducing the slope. A 372-m penstock shaft up to the power house and 992-m audit tunnel was constructed in Gongardanda in a year for construction of the upper part of the main tunnel. Construction has been halted for a month after completing 410 meters from Penstock Audit toward the main tunnel. Preparations are underway to construct a penstock shaft at the same place.

    The tunnel cannot be constructed from the lower part as per the new design. A kilometer of audit tunnel has to be constructed again building a road 260 meters above if a tunnel is to be built. That will take another year. The 2.61 km lower section from Bhainse Audit and 2.33 km upper section from Penstock Audit have to be completed within a year, according to the schedule. Only 1.1 km from Bhainse and 410 m from Penstock has been completed till date.

    The preliminary study for the project had recommended the tunnel to be built with 0.3 percent slope. But the detailed design feasibility study had proposed constructing it with a 0.8 percent slope stating that there will not be place to construct audit tunnel and it will take longer time. Norsconsult had done the detailed design feasibility study for the project. Sino Hydro Corporation is currently doing civil construction works. Texmaco of India is doing hydromechanical, Andritz Hydro of Austria electromechanical and KEC of India the transmission line works.

    Repair works are underway after upper part of the 100-m stretch out of the 142-m power house tunnel, that was handed over by the contractor after quality check by the consultant, started to crack after three months. It will cost Rs 40 million. Repair of half of the cracked portion has been completed till now. The work of penstock shaft has been delayed by six months after the older machine for boring had to be returned and a new one brought from Germany. It was stopped after the machine, that was cleared from the customs in three months, constructed it four meters away from the determined place. A nine-inch vertical hole was made to the power house in the first stage but it has since been sealed with cement solution due to problems.

    The contractor is now preparing to bring a boring machine of new model from Germany. A 372-, penstock shaft and 440-m surge shaft have to be constructed in the project. Another 260-m shaft has now been added. The estimated cost of the project, apart from the interest during the construction period, is Rs 35.29 billion.

    Source : Karobar