September_1965 — Page 35

CIVIL ENGINEERING AND PUBLIC WORKS

Thailand's Nam Pong irrigation project

First stage will

benefit more

than 88,000 acres

**

A

LARGE-SCALE

water

storage

and irrigation project began in the north-east region of Thailand early this year. Known as the Nam Pong project, it is being carried out in two phases: (1) the Ubol Ratana storage dam; and (2) the Nong Wai diversion dam and distri- bution system.

The Nong Wai diversion dam and distribution system are for the ir- rigation of land on both banks of Nam Pong (Pong River) in the vic- inity of Khon Kaen. The dam is located about 35 kilometres down- stream of the Ubol Ratana dam. This irrigation project is designed and constructed by the Royal Irriga- tion Department, Ministry of Nation- al Development, Bangkok.

The work calls for the develop- ment of the area below the Nong Wai Dam along the left and right

banks of the Nam Pong river, with future provision for development on its left bank.

Headworks

Nong Wai headworks consist of a diversion dam, left head regulator and sand sluice, right head regulator and sand sluice, a river closure dam, an emergency spillway, and a high- way bridge.

The diversion dam is of ogee shape, constructed in a cut-off chan- nel on the river bend at Ban Nam

Concrete ogee weir under construction

Temporary timber trestle erected parallel to the centre line of the bridge to support 30m. prestressed concrete beam during concrete placement and first stage prestressing before beam is moved to its final position

Pong. It is 125 meters long, serving as a service spillway and having a crest elevation at + 162.5 M.S.L.. It is designed to pass a maximum dis- charge of 1,500 cu. metres per second (cms.).

The emergency spillway, 240 metres in length, is an earthfill em- bankment which will be constructed on the right side of the diversion dam. It has a crest elevation at + 166.00 M.S.L. and is designed to pass the flood of about 1,000 cms.. after the earth embankment is washed out to the expected elevation + 163.50 M.S.L. The combined discharge capacity for the diversion dam and the emergency spillway is, therefore, 2,500 cms.

At the extreme left end of the di- version dam, a left sand sluice and a left head regulator are construct- ed at right angles to each other. The left sand sluice consists of three 4.00 m. x 2.50 m. openings, each with a radial gate of 4.00 m. x 2.80 m., with its sill elevation at + 159.05 M.S.L.

The left head regulator, having a capacity of 35.5 cms., has two 4.00 m. x 2.25 m. openings, each with a radial gate of 4.00 m. x 2.55 m., with the sill elevation at + 160.25 M.S.L.

Likewise, at the extreme right end of the diversion dam, a right sand sluice and a right head regulator, being set at right angles to each other, are constructed. The right sand sluice consists of two 4.00 m.

Far East Architect & Builder September, 1965

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