The 720 MW Mangdechhu Hydropower Project is expected to kick-off any time beginning 2009. It will take approximately seven years to complete. The project is expected to bring in a lot of economic boon to the local people in Trongsa. As per the Department of Energy (DoE) during construction, there will be hundreds of labourers and expatriates which will be a huge market for the local house owners and business people. It will also bring in employment to petty contractors as most of the minor works will be sub-contracted. "New roads, bridges, schools, medical facilities, fuel stations and automobile workshops et al. will be established for the project staff during construction phase and post construction. This will benefit the local communities as well," officials from DoE said. The mega project is tentatively proposed to be funded by the Government of India on similar financing model as that of Tala/Punatsangchu projects. The project, by virtue of being a run-of-the-river scheme with minimum reservoir volume and located in a remote, uninhibited valley of the scarcely populated Trongsa Dzongkhag, will have minimum impact on the environment and human settlement. As per the preliminary assessment, no human settlements are likely to be affected by the main project components as most of the hydropower structure are located underground and the dam site is located in the deep gorge. Reports coming in so far suggest that this project has minimal environmental impacts. However, around 28.47 hectares of private land will be acquired by the project for various uses like road construction, labour camps, site offices, colony and administrative blocks, et al. The detailed environmental impact assessment and socioeconomic study of the project is under preparation and will be submitted soon, the DoE said. NHPC, which was assigned the Detail Project Report (DPR) works have submitted the draft DPR on May 2008, six months ahead of scheduled November date. The final DPR is expected to be submitted by September which was scheduled for April 2009. NHPC officials said that they could complete the work before schedule because of intense coordination and monitoring works by DoE and the hard work they put in. A large number of labourers were deployed to complete the work. The post DPR work constitutes completion of exploratory drift at underground powerhouse site. The project is being carried out by the University of North Bengal, West Bengal, India, in close association with the NEC. In February 2005 an MoU was signed between Bhutan and India for technical assistance for preparation of DPR and subsequently, NHPC was appointed as the consultant. Pre-feasibility for the project was carried in 1993 and later feasibility studies were conducted in July 1999 by Norconsult. The feasibility study of the Mangdechhu Project under the NORAD/ Norwegian Government funding has found that a hydro power project of 360 MW capacity across the Mangdechhu was feasible. Subsequently, the installed capacity of 360 MW in feasibility report was upgraded to 670 MW (6 x 111.5 MW) in the feasibility report-2004 based on revised hydrological data. However the location of the dam, powerhouse and outlet differs from that of the prefeasibility study in the report submitted by the NHPC. The dam has been proposed across Mangdechhu, about 800m downstream. The Main Access Tunnel of Power House is on the Gelephu-Trongsa highway and is about 44 km from Trongsa. The dam site and intake is located at about 14 km downstream of Trongsa town, across the Mangdechhu. The underground powerhouse is located inside the mountain below the Yurmu village. The head race tunnel of the project traverses a length of 13.544 km. The surge shaft and the pressure shaft are located in the area of Samchholing. A four km road will be constructed as approach road to the dam site from the Trongsa- Gelephu highway. During the course of investigations, there were broad changes over the feasibility design which has been proposed in the DPR. Most notable has been the relocation of the dam axis to 550 m. The basic reason for the shifting of the dam site has been the uncertain depth of the overburden in the river bed at the location chosen in the feasibility report. As per the report, an underground powerhouse with four generating units of 180 MW each is envisaged. The estimated annual energy generation from this 720 MW power plant is 2923.70 MU. Most of the energy generated will be exported to India after meeting its internal consumption. Harnessing the hydropower is said to be technoeconomically cost effective and environment friendly. Of the total of 30,000 MW of hydro power potential, so far 23,760 MW has been identified and assessed to be technically feasible. Only 1.6% of the potential is harnessed so far.
By Rabi C. Dahal