CIVIL ENGINEERING & PUBLIC WORKS
x 2.50 m. openings, each with a ra- dial gate of 4.00 m. x 2.80 m. with the sill elevation at + 159.05 M.S.L. The right head regulator with its sill elevation at + 160.30 M.S.L. having a capacity of 18 cms., has two 3.00 m. x 2.20 m. openings, each with ra- dial gate of 3.00 m. x 2.50 m.
The river closure dam will be a 450 metre long earthfill dam, reach- ing a maximum height of 19.00 m. above the river bed. The dam crest is at elevation + 169.00 M.S.L.. and has a freeboard of 1.8 metres.
cuts
Since the cut-off channel across the Korat-Nongkai highway. a reinforced concrete bridge will be constructed across the channel. The bridge is of five 30 metre prestressed spans and four 10 metre slab type spans. Two spans of the slab type will be built on each left and right abutment.
Distribution System
There will be two main supply canals, one on the left bank of Nam Pong river having a total length of 64.5 kilometres, in the first stage, and the other on the right bank hav- ing a total length of 34.8 kilometres The bed slope of both main canals, is 1:12,000 and the side slope is 1 (vertical) to 1 (horizontal).
In the first stage, the land to be irrigated will be 141,000 rai (56,500 acres) on the left bank and 79,300 rai (31,700 acres) on the right bank. An area of about 82,200 rai (32,850 acres) is planned to be irrigated in the future by extension of the left main canal.
Construction
The first year construction of the project is centred on the headworks which began in early January 1965. It is scheduled to be completed
Scrapers and compactors at work on earth embankment near emergency spillway
in
General view from left abutment of earth closure dam (Nam Pong)
the dry season of 1966, when the
Ubol Ratana
Dam is expected
to be brought to completion. Main canals, laterals and sublaterals are scheduled for completion by the end of 1969.
The construc-
tion cost of the
Nong Wai head-
works and its dis-
tribution system is estimated at Baht 220 million from the Govern- ment budget ap- propriation.
The completed project has a benefit-cost ratio of 7:9.
口
Construction of left head regulator (size: 2 of 4,00 x 2.25 m.)
seen from down- stream
Far East Architect & Builder September, 1965
73