September_1966 — Page 65

Menglang Tunnel

To supply water from the Jor re- servoir to the Woh power station, a 16 ft. to 16% ft. dia. low pressure tunnel. 9 miles long, is now under construction. It will be an unlined tunnel with concrete or gunite lining only where bad rock conditions are encountered and will have a 4 in. thick (min.) concrete invert along its whole length.

Sidestream intakes, named the Lengkok, Bot, Chenes, Tidong and Woh intakes, along the route of the tunnel are being constructed to dis- charge additional water into the tun- nel by means of concrete lined drop- shafts, which vary from 6 ft. diameter to 10 ft. diameter and up to 330 ft. deep.

To control the supply water from the Jor reservoir into Menglang tun- nel, a reinforced concrete intake struc- ture, 130 ft. high, is being built. This will have a system of intake screens complete with rakes for moving ac- cumulated debris such as branches and leaves, an 11 ft. x 17 ft. high bulkhead gate and an 11 ft. x 17 ft. high main gate, both electrically operated, and a 100 ft. long precast prestressed concrete access bridge spanning between the intake structure and an access road.

Upper Surge Shaft

Located at the southern end of the Menglang Tunnel is a concrete lined surge shaft, 40 ft. diameter and 450 ft. high, which will dampen surges which may occur when sudden ac-

Jor saddle dam. View from left bank showing cut-off trench in foreground and, on the right bank, the concrete spearhead.

ceptance or rejection of load occurs on the water turbines in the Woh power station.

In the invert of the Menglang tun- nel, a rock trap will be constructed to intercept any pieces of rock and de- travel bris which might otherwise along the tunnel and find their way into the turbines.

Two high pressure steel lined pres- sure shafts, each 1,680 ft. long and ranging from 71⁄2 ft. to 7 ft. diameter slope down, at an angle of 47 degrees

Turfing has begun at the downstream toe

to the horizontal, from the upper surge shaft to the Woh power station. Each shaft has been designed to sup- ply two turbines. Valve chambers are located at each end of the pres- sure shafts, to isolate either shaft for inspection.

Woh Power Station

The power station consists of three underground caverns: the lower valve chamber, the machine hall and the

Jor reservoir spillway stilling basin. Left wall is nearly complete and first of the T-shaped baffle blocks has been built

Far East Architect & Builder September, 1966

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