KATHMANDU, AUG 08 –
Citing the weak geology, Norconsult—the consultant for the country’s largest hydropower project which is under construction—had recommended that the remaining portion of the tunnel be redesigned.
Despite the redesigning, Nepal Electricity Authority (NEA) that also holds the controlling stake at the Upper Tamakoshi Hydropower Limited (UTHL)—the developer of the 456 MW run of the river (RoR) project—has claimed it would be delayed by only two months than the previous schedule.
SINTEF, a Norwegian company during its rock stress measurement two months ago had concluded that the tunnel must be realigned in order to prevent hydraulic fracturing and uncontrollable loss of water.
“As the alignment of the tunnel had to be changed to avoid the hydraulic fracturing as a result of high pressure, additional 650-meter steel penstock pipe has to be fitted at the end of the 8-km long headrace tunnel,” says the preliminary report that Norconsult submitted to NEA a month ago.
As per the preliminary estimates, additional penstock pipes will cost about Rs 1 billion and rerouting of the tunnel will cost Rs 500 million more, shooting up the total project cost by Rs 1.50 billion.
Bigyan Prasad Shrestha, officiating project director of the Tamakoshi project, said as recommended by the consultant the remaining 3.5km portion of the tunnel would be constructed in 0.3 percent slope design. Of the total 8km length of the tunnel, the project has dug 5km tunnel with 8.33 percent slope.
“We had adopted the consultant’s previous design for the tunnel which will now be changed into the horizontal one,” Shrestha said, insisting that the cost overrun will be nominal despite the redesigning of the tunnel.
He claimed that the tunnel redesigning would cost an additional Rs 1.50 billion, while the project has already saved around Rs 1.26 billion by adopting the inclined design for the tunnel construction.
Bimal Gurung, chief of the project’s planning and monitoring department, said the tunnel dug so far will be kept intact and the remaining portion will only be developed under the new design.
“To cut cost from the very beginning, we had chosen the inclined design for the project. Therefore, the change in design will not cost much, both in terms of overall project cost and project completion date,” Gurung said.
He also said as per the project’s revised schedule, the first unit will start commercial operation by December 2015—around seven months behind schedule. The remaining five units will be delayed by two months. “Previously, we had targeted to keep two-month gap for bringing each unit into operation. That will now be revised to one month,” added Gurung, “So the project will only be delayed by two months.”
Shrestha said technical problems like the one occurred in the tunnel works were common in big projects. According to him, a team of experts from the consultancy firm has already been deployed at the project site to further investigate into the matter.
“It’s been recommended to change the preliminary design. Once the detailed study is done, it might as well suggest retaining the same design,” Shrestha added.
The officials at the project site in Lamabar said though construction of the remaining portion of the tunnel has begun as per the new design to accelerate the work, it can easily be modified into the previous one without any cost overrun.
Forty-eight percent of the civil works and 41 percent of the total construction works have so far been completed. Sino Hydro, the project’s civil works contractor, has deployed around 400 Chinese and 1,200 Nepali workers to accelerate the project construction.
Source : The Kathmandu Post