CIVIL ENGINEERING & PUBLIC WORKS
ECTOR gates are being installed at the Bustos Dam on the Angat River in Bulacan, Philippines, to create a reservoir of water for irriga- tion and flood control.
Installation of the gates will raise the water level of the dam by 2.5 metres to form a reservoir extending 5 kilometers upstream and having a capacity of 3.000.000 cubic metres. This will provide water for irrigating an additional 600 hectares of rice land.
The six sector gates to be installed are submersible and hydraulically operated. Each is 79 metres wide and has a damming height of 2.5 metres. With the control house and supporting piers, the gates will span a distance of 501.26 metres.
The raising of the Bustos Dam is the result of studies conducted by government engineers to provide storage requirement based оп an average water release of 36 cubic metres per second at the main power plant at San Lorenzo, Norzagaray.
It was determined that the approxi- mate schedule of hourly releases in the main power plant fluctuates and since the requirement for irrigation is a steady water supply, an after-bay regulator was considered suitable to store the extra water at times when the release is more than the irriga- tion requirement and vice-versa.
To take care of future variation in the schedule of releases from the main power plant, sedimentation and losses, the capacity of the reservoir at 3,000,000 cubic metres was adopted.
Two schemes for raising the crest of the existing diversion works were proposed. One called for the recons truction of the present 3 metre solid section to a 5.50 metre ogee solid section and the other, by installing steel gates 2.5 metres high over the present crest of the diversion dam.
Since the former was found to re- quire substantial modification of the existing structures and the installation of expensive flood protection works to protect the populated communities upstream of the dam. the latter scheme was adopted. During floods, when the gates are lowered, almost the entire width of the river is open. permitting maximum passage of
water.
Two Schemes
The movement of the gates is re- gulated from the control house on the south end of the dam. An intake channel is located on the upstream side of the control house and a pipe- line system governed by three-way valves lets water flow into or out of the sector chambers, controlling the position of the gates.
By means of a switch, the entire operation can be put on automatic control. Gauges installed at the con- trol house show at a glance the actual position of each gate.
A water level indicator on the up- stream side acts on the automatic control to maintain a constant water evel at Elev. 17.50.
Far East Architect & Builder January, 1966
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Gates being assembled on site
Aside from this distinct feature of maintaining a more or less uniform water surface elevation to prevent oc- casional inundation of lands up- stream, other advantages of the gates
are:
a)
b)
c)
Water flows over the gate so that for any flood elevation, all de- bris, floating logs, etc. flow over the gate with no danger of get- ting entangled.
The great widths of the gates further insure free flow of de- bris.
The hydraulic raising and lower- ing of the gates requires a mi- nimum of electric power for the operation of the small motors controlling the three-way valves, as against the big power ге-
quirements for the hoists in other gate installations. Similarly, in case of power failure, it is sim- ple to regulate the three-way valves manually. The operation can be handled manually by one man without much effort. Eisenbau Wyhlen, A. G., designed the sector gates and fabricated the backplates and bearings, ventilation, suction device, and control system.
C. & A. Construction Co., Inc., re- presentative of Eisenbau Wyhlen A. G., contracted the Atlantic, Gulf & Pacific Co.. Manila, to fabricate the skin plates, struts, bracings, em- bedded parts, fixed parts, breastwall seals, fixed parts rotating axis seals and fixed parts side seals of the sec- tor gates.
Tenders in June for Harbour Tunnel
Tenders will be invited in June by the Cross-Harbour Tunnel Co., Ltd. for the construction of the four-lane highway tunnel across Hong Kong Harbour.
As reported in this journal in July 1965, the tunnel will be of the im- mersed tube type and will extend about 5,200 ft. between portals. It will cost about $211 million and is due to be opened in 1970,
The main contract will include the construction of the tunnel, ventilation buildings, approaches and toll plaza and the provision of ventilation plant and other equipment.
Prospective tenderers, whose ap- plications were due in last month, will
be given preliminary data shortly to enable them to gather information and to prepare preliminary schemes prior to tendering. The final tender document will contain full specifica- tions and quantities for the scheme. but tenderers may also submit alterna- tive schemes of their own.
The tender document will include provision for contractors to show to what extent they would be prepared to provide facilities for financing the construction.
The consulting engineers for the project are Scott and Wilson, Kirk- patrick and Partners, Hong Kong, and Freeman, Fox and London.
Partners,
65
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