Bureau under the direction of the type water turbines of 97,100 h.p. at Commission.
a designed head of 97.6 metres will be coupled to two 50,000 kW generators. A switchyard in the open and a 28 km, 154.4 kV, single-circuit transmission line will be constructed to connect the power plant with Taipower's Hsinying substation.
A contract was signed in January 1967 with Koei Company of Japan for the detailed engineering design of the dam, diversion tunnels, power plant and spillway. Work on the diver- sion tunnels began in October 1967 and is scheduled to be finished by October 1969 when the dam will be started. The whole project should be completed by October 1973.
Reservoir
Tsengwen reservoir will be 20 kilo- metres long and will cover 20 sq. kilo- metres. The gross storage capacity will be 892,000,000 cu. metres, including an active capacity of 767,000,000
cu.
metres and a dead storage of 125,000,000 cu. metres.
The dam will be an earth embank- ment 136.5 metres high above river bed, 440 metres long at the crest and 11,400,000 cu. metres in volume. It will have an impervious core and will be surfaced with shells composed of cobble gravels in concrete.
Plans for the spillway on the right abutment show a concrete chute-type structure. Gates will be installed to regulate the flood and will be capable of discharging 9,700 c.m.s. through the spillway at a possible peak flood of 11,100 c.m.s. entering the reservoir.
The power plant, an underground structure, is located in the left abut- ment of the main dam, between the two diversion tunnels. Two Francis-
The weir is situated on the Tseng- wen River, about 6 kilometres down stream from the main dam and 400 metres downstream from the existing Tungkow intake. It consists of a con- crete ogee section, 17.5 metres high and 200 metres in total length, with a 100-metre overflow crest and two 10 x 8-metre top-sealed radial gates at the right abutment.
The weir will create an afterbay for regulation of the water released from peak power generation to be supplied to Wushantou reservoir for irrigation uses. Regulating capacity of the afterbay is 1,780,000 cu. metres. Preparatory works
Before construction of the dam commences, two diversion tunnels, one 1,250 metres and the other 1,083 metres long, are being dug through the hills to divert the river water from the dam site. Each tunnel has a finish- ed diameter of 12 metres. The total designed discharge rate is 7,980 c.m.s.
sufficient to pass the maximum flood in 75 years. The tunnels will be sealed and abandoned after completion of the dam.
Since the formation of the En-
gineering Bureau the following pre- paratory works have been carried out or are in progress:
Access roads. A new road, 11.66 kilometres long and 11.5 metres wide, from Nanhsi to the damsite has been constructed. It includes four pre- stressed bridges totalling 650 metres in length and 67 conduits. It winds along difficult terrain, following the terrace by Tsengwen River.
A branch road, about 2 kilometres in length with two bridges, leads to the intakes of the diversion tunnels, and an elevated road of 1,5 kilometres with seven conduits is now under construction to link with the spillway site.
Parts of the existing highway be- tween Hsinshih and Nanhsi had to be widened, straightened and reinforced for hauling the heavy construction machinery, and this work is now near completion.
Housing. A site near the Tungkou intake was chosen for the development of a new village. Two two-storey con- crete buildings for office use, several dormitories and a guest house, as well as warehouses and repair workshops have been built
Power supply and communications. Some 7,500 kW of power needed by the construction work is supplied from Taipower's Paho substation through 66 kV transmission lines to the damsite substation where it is converted to 3,3 kV for various field uses.
For communication, five telephone
Temporary cofferdam and diversion tunnel intakes
Far East BUILDER, May 1969
37