In the original survey plan it is noted that there is a small shallow pond at the northeast portion of the site. It is suggested that this should be a spawning pond or fry holding area and the details left to be done by the government biologists to suit their needs.
A layout plan where there are a series of small ponds (Ponds 1 to 6 are 1500 m2 each) for experimental work allowing replications is suggested. Ponds 8 to 11 are 5000 m2 each for experiments and production studies. The procedure to be followed for the construction are enumerated below.
I. Construction:
(a) Pond bottom to be set at 0.9 or 1 m in relation to the tidal cycle (0 datum at mean lower low water). Ponds to be totally dry at 0.8 or lower tides.
(b) Perimeter dike outside the fence should not be less than 4.1 m high after soil has settled. An allowance of 15 to 20 percent shrinkage should be given. This gives a freeboard of 0.5 m over the highest tide water. The higher the freeboard the better. It is noted that the eastern side used to be flooded during very high tides.
(c) Gates (Figure 15 a)
Main Gate A may be 7–10 cm lower than Gates B and C.
B and C are of the same elevation but should be 5–7 cm lower than pond bottom.
Drainage gates (D) and canals (F) need not be constructed during the first phase, however it is suggested that provisions for them be made in case the biologists may have need for them later.
Provisions for extensive water management and manipulation becomes more and more important when working with intensive production involving feeding and heavy stocking rates.
It is also recommended that at Gate A provision be made for a sizable centrifugal (high volume lowhead) pump provided with a vertical electric motor as prime mover (electricity being available at the site). If desired a pump can be designed and fabricated to drain or fill the ponds regardless of the tide condition. (Annex 5, Figure 5a).
II. Program of work
(a) Drain the pond, pump dry if necessary.
(b) Level pond, preferably with dozer. Pond bottom should be as close to 0.9 m elevation as possible.
(c) While the pond bottom is being worked on, the supply creek should be widened and deepened preferably to 0.5 m lower than the bottom of Gate A. It is observed that the supply creek Sungei Tampines is quite narrow and shallow.
(d) After the pond bottom has been leveled, an accurate survey should be made to ensure that the internal area of each of the four compartment ponds, 8 to 11 is 5000 m2. The location of the gates should at this time be marked and the transverse canals from Gates B to D (5–7 cm lower than pond bottom) can be excavated. Ponds 1 to 6 are all 1500 m2.
(e) It is suggested that permanent water level markers be made or integrated on the sides of each gate to facilitate water level and volume readings.
(f) It is suggested further that each gate be provided with 3 slots on either sides so double flashboards can be placed and packed with mud should stagnant water be desired on certain experiments. The third groove is for screening of water or for fish size grading devices. These flashboard slots (3) should be on both ends of each gate, making a total of 6 pairs of slots or grooves.
(g) Should a topographic survey reveal that the soil in the pond is not enough to reach the desired level then it is suggested that dredge spoils from the deepened and widened Sungei Tampenis be piped into the ponds to raise its bottom to the desired elevation.
(h) In this layout adjoining ponds can be joined by cutting the pond separators (levees or bunds) in two or three places. This would make possible culture experiments requiring larger areas. If the pond separators are to be made of concrete, provisions should be made during the construction to allow for such flexibility.
(l) Because of the sandy bottom of the pond it is strongly recommended that sheet piles be used in every pond separator or dike.
FIGURE 15 a
SUGGESTED LAYOUT AND CONSTRUCTION OF
EXPERIMENTAL PONDS (Golden Palace Ponds)
SINGAPORE
SCALE 1:800 M.
