A layout for Phase I (Fig. 2) has been prepared by the FAO Team Leader. It consists of 8 grow-out ponds of 1–2 ha, 3 nurseries of 4 000 to 5 000 m2, and the necessary water supply and drainage canals. It is intended to operate the nursery ponds as small grow-out ponds if required. Two main concrete gates will regulate water inflow and outflow.
Plans are to provide the ponds with one or more sluices or single gates with multiple openings, depending upon the size of the ponds and their water requirements. An arrangement for better water exchange, using an inlet and an outlet gate set on the same dike beside the supply canal is being incorporated in one pond. By adding an incomplete longitudinal dike that bisects the area, a U-shaped raceway effect is created when pond water is let out at low tide through the outlet gate and new water let in through the inlet gate during high tide.
No layout plan for the remaining area has been decided upon pending completion of the survey and plotting of the exact position of the perimeter dikes.
Dike construction is performed mainly by manual labour. All dikes are made out of oil taken from both sides. Round shovels are used for digging, wheelbarrows for transporting. Wooden boards are provided as runners over which the wheelbarrows are pushed.
A standard group consisting of 28 labourers is issued with 14 shovels and a similar number of wheelbarrows and assigned to move about 40 m3 of soil per day. The soil has to be taken evenly from an area of 160 m2 up to a depth of 25 cm. Completing this task, each member earns K.Sh. 15.001, reflected in the payroll as a day's wage.
However, when equipment deteriorates or gets damaged, and repairs or replacements are considerably delayed, the number of men to the group is reduced and the amount of work prorated accordingly, with each accounting for 1.425 m2 of soil moved per day. At this rate, cost of soil movement is K.Sh. 10.53/m3.
For concrete works (sluices) daily wage labour is used. A cement mixer was obtained from the Government when the main concrete gate was being constructed.
As of 8 September 1981, the following work had been accomplished:
Clearing - Approximately 80 percent of the Rhizophora vegetation cut close to the ground and heaped in piles. A few small strips and clumps remain at the northern and central portions.
Perimeter dikes - About 2 700 m constructed almost encircling the whole 50 ha except where sections have been deliberately left open to allow free flow of tide water. Many portions, however, need to be raised and a uniform slope maintained. Dike dimensions are as follows:
Base - 6 to 8 m
Crown - 2 to 6 m
Height - 1 to 1.8 m
Secondary dikes - Almost 880 m raised, some completely, others just a few layers from the ground line. Dimensions are:
Base - 4 to 8 m
Crown - 1.2 to 1.5 m
Height - 0.2 to 1.6 m
Common supply and drainage canals - About 538 m of main and 375 m of secondary canals dug, and the excavated soil used for some of the secondary dikes mentioned above. The width at ground level range from 4 to 5 m; at bottom, from 2 to 3 m. Depth from GL is approximately 50 to 75 cm. The main canal had not been connected to the main concrete gate.
Sluices - One concrete main gate with two openings of 1.5 m erected, still enclosed by earthen coffer dam; two secondary gates with concrete floor and limestone block walls installed at one pond. Both secondary gates are operational. Two more of the same design are in the process of construction.
Ponds - Only one (Pond 3, Fig. 2) completed. Water area is about 1.16 ha; bottom elevation is estimated at level of 3.0 m tide. This is the pond equipped with the two secondary gates above mentioned.
Buildings - One semi-permanent 5-roomed building recently completed, overlooking the farm from a low rise across the road. Two of the rooms are intended for offices, two for temporary storage of equipment and one as a bedroom for staff on night duty.
1 As of 8 September 1981, K.Sh. 1 = US$ 0.1136
