New solution and Germany Company comes to rescue of P- I’s troubled right bank
October 19 | The Bhutanese
By Tenzing Lamsang
The solutions however could push the completion date from 2024 to March 2025
If there is one project that has caused much national worry, then it is the 1200 MW Punatsangchu I project costing Nu 93.7 bn.
The main issue has been the stability of its so far volatile right bank that has refused to stop sliding delaying the dam construction works, and as a result, the entire project.
Given the seriousness of the situation there were even calls from some politicians and others to explore abandoning the project all together.
However, there is fresh hope and optimism for the beleaguered project based on a report submitted by the Central Water Commission (CWC) of India, based on discussion not only within CWC but also Bhutanese counterparts and some of the best companies around the world to solve the right bank problem.
The report submitted on 1st October 2019 is also different from past ones in the words of the Minister of Economic Affairs Lyonpo Loknath Sharma who said that he had insisted on a more holistic solution to the entire right bank areas and not just the slide areas.
Lyonpo said that apart from help from Indian and international companies even divine intervention had been sought in the form the Je Khenpo visiting the site and blessing it in May 2019.
On the advice of the Je Khenpo a stupa had also been built near the site.
The minister said that things seem to be going well as the movement of the right bank has noticeably decreased.
A senior PHPA- I official said that the the problem started with the July 2013 slide. It was followed by a major one in August 2016 and again despite mitigation measures the same area slid on 22nd January 2019.
After this the government in the 21st PHPA Authority meeting in January 2019 insisted to the Indian consultants to come up with a comprehensive solution and that report was submitted by CWC on 1st October 2019.
The actual drawings are being released in a stage by stage basis.
The main solution now rests in a German Company called Bauer which has proposed to drive in 26 two-meter diameter cement pylons or pillars of 100 to 110 meters’ length at the highway level to stabilize the right bank and prevent additional slides from above while excavation and strengthening works go on below.
The official said that this German Company is the only company in the world which has the capability and is confident of doing this work. A French company had worked with rectangular pylons but it was not as confident.
The idea is that the cement pillars will anchor the right bank to hard rock surface. The official said that a lot of geological studies and software analysis had been done.
Below there will be some excavation to remove the slide. Along with the cement pylons there will be 150 metric tons of cable anchoring used to strengthen the right bank and slide area. There will also be additional grid works to strengthen the area.
Apart from this strengthening works there has also been been a change in design to reduce excavation work in the right bank lower down from the dam site.
The official said that under the earlier plan the water coming out from the dam was supposed to come out from a height and then head into a concrete plunge pool which would require more excavation of the right bank. The design change now means that the water will come out at a lower level from the dam so that a deep plunge pool is not required.
The German company is expected to get the work by October and it would be six to seven months before the concrete pylons can be driven in which means April 2020.
The earlier pylons were driven in only to 65 meters.
The senior official said that now they are so confident that they have started with the concreting of the dam from the stable left bank side. The total dam width is 241 meters the the starting work area in the left side is 51 meters.
An earlier concern was that the Wangdue highway may have to be relocated but if all works out then the highway can also be saved.
One suggestion of the CWC was that the dam on the right bank side be constructed over 288 concrete pylons driven into the ground to avoid excavating 39 meters of shear zone below the right bank side.
The Bhutanese side is not very confident of that plan since there are no similar examples of works done like this elsewhere.
So the agreement is that they will see if the right bank stabilizes with all the measures and if it does then they will excavate this additional 39 meters to construct the dam.
The senior PHPA- I official who is also Bhutanese said the aim is build a national asset that will serve for at least 100 years.
The strengthening works on the right bank could cost an additional Nu 1.5 bn and all changes could mean the project is delayed to March 2025 from the current completion date of 2024 but the official said the aim will be to complete before that.
The official said that he is confident that the project will be built as an asset for the nation and there is no question of abandoning it.