The Central Water Supply Scheme project funded by World Bank was taken up by M/s Nima construction co Pvt. Ltd and M/s Fine INC from Korea for construction of intake, transmission main from Dodena to Taba and distribution mains with CWR at different locations including Care takers quarters and M/s East west construction and Fine INC constructed the 10 MLD Water treatment Plant at Taba.
During the initial stage of testing and commissioning, there were few pipe joints breaking or falling apart from high water pressure. Contractors said that breaking or falling apart of pipe joints from high pressure is obvious during the initial stage of testing but once tested, the joints are not likely to fall apart again.
One reason for the pipes coming apart is due to the inadequate number of thrust blocks of cement structures that hold the pipe joints in place so far. Thromde officials say there is an adequate quantity of thrust blocks in the bills of quantities to secure the pipe joints with estimated quantity of around 3126 cum so far more than 1800 cum have been constructed at the site and the contractor will continue to construct Thrust Blocks based on the site conditions and as per technical requirements at the site.
M/s East West Construction said that they cannot detect the leakage unless they test the pressure. “It is only while we test the water pressure that we come to know that there is certain leakage. Wherever there is leakage, we are repairing it by constructing thrust block,” said the company.
Nima Construction Private Limited said, “The major pipe burst which affected the house was not in our line. A separate line was put by another contractor near Blue Poppy Tour office at Langjophakha, which is a new pipeline diverted from our line at Langjophakha to BCCI office tank”.
Sonam Dorji, the Managing Director of Nima Construction company said, “This was not in the initial plan nor were we informed before when they started doing the works. During charging of this new line, their pipe bursted and a house was affected. This was done under the supervision of the thromde and our project is not even remotely connected to this”.
He said, “There has been no pipe burst in Samarzingkha, the pipe was damaged by some other contractor who built a road there. There were small holes made which was hidden by filling soil over them. There was very less leakage of water and no household was damaged”.
He also said, “There were three locations in Langjophakha Samarzingkha line where pipe burst or leakage was there but it was due to the work done by other contractors during road works”.
“From November 2018 to 24th April 2019, there were series of damages done to completed pipelines between Langjophakha and Changjiji done by other contractors or locals. On November 2018, 200 mm DI pipe above National assembly building was damaged from road widening by another contractor. The pipeline was damaged by machine and it had to be repaired using a mechanical joint. Again, on 12th April 2019, a leakage was found during the charging of water towards YHS reservoir tank.
This stretch was previously pressure tested. After the widening of the road, the damage seems to have occurred which was repaired by wielding”, he said.
“200 mm DI pipe between Dechen Zam and CDCL Bridge was damaged on 8th April and another 200 mm DI pipe was damaged 200 meters above CDCL Bridge. During the charging of water towards Changjiji tank, leakages were found in two places.
The damage has occurred during the construction of road by the locals and sacks were inserted into the hole and buried with mud to hide the damage. Both of them were damaged by it ”, he added.
He said, “Just before the newly constructed bridge by CDCL, the pipelines were damaged at two places on 24th April when the excavator was constructing a bypass road towards the river bed. A new pipeline has been cut and connected with the mechanical joint”.
According to the Project Manager, there are more than 30 kms of pipe line with diameters ranging from 150 mm to 400 mm and each pipe is 6 m in length and the joints provided are push on joints commonly used due to its cost effectiveness. Use of flange joints and welded joints are costly and expensive.
He said that this push on joints are easy and fast to join and every joint can be bend till 5 degree without additional bends which is very much necessary for the hilly terrain area. The pipe can be rotated on its axis even after jointing.
He said, “As it is flexible this push on joints need to be anchored or fixed to prevent it from moving when the pressure load is applied.
If it is not perfectly straight, this joint cannot resist tensile stress so we should not let it to move to generate tensile stress either by burying it underground or making thrust block over it. If it is on perfectly straight line this issue will not arise”.
Currently the contractor is still testing and commissioning process and such joint failing is occurred due to burying all the pipes or joints below the ground level due to the rugged terrain.
The joint that has been already tackled during the testing and charging will have no problems later once rectified according to officials.