Mangdechhu – I Hydroelectric Project

The Mangdechhu hydroelectric project is a 720 MW run-of-river power plant being built on the Mangdechhu River in Trongsa Dzongkhag District of central Bhutan. The project comprises of a 101.5 m high concrete gravity dam from the deepest foundation level, two intake tunnels of 196 m and 150 m in length, and a 13.54 km long headrace tunnel capable of discharging 118 m³ of water per second. The 152 m high surge shaft has a diameter of 13.5 m. Water is fed to the underground powerhouse through two steel-lined pressure shafts (1,853 m long and 3.5 m in diameter). The main cavern of the underground powerhouse is 53 m high and 231 m long.

Encardio Rite was awarded the contract for monitoring of dam, powerhouse, intake, desilting chamber, surge shaft, pressure shafts, and adits. Turnkey services included:

• Supply of geotechnical instrumentation for the dam and powerhouse
• Installation services
• Online monitoring of critical parameters and areas
• Manual monitoring

Instruments used:

• Piezometers: To monitor uplift pressure below the dam & pore pressure of water in the dam body
• Strain meter group: To monitor concrete stress and strains
• Perimetric and uniaxial joint meters: To monitor linear movement between the block joints
• Temperature meter and tele-thermometer
• Borehole extensometers: Multi-point and single-point installed to monitor deformations
• Normal and inverted plumb lines: To monitor the tilt of the dam
• Load cells: Anchor bolt load cells installed to monitor load on anchors
• V-notches: To measure seepage water flow collected in drainage channels 
• Survey markers and settlement points
• Automatic data acquisition system: Commissioned for logging data from the above sensors
• Strong motion accelerometer: To monitor accelerations in the earth due to reservoir seismicity