ANNEX 13

FISHPOND CONSTRUCTION: PROCEDURES AND INNOVATIONS

I. Manual labour

A. Diking using flatboat (Figures 13a, b and c)

In diking using flatboat with the following specifications, these results were obtained:

Dike height up to 1 meter
Soil in good workable state
Work man is skilled in this type of work
Working alone with one flatboat - he cuts soil, load on flatboat and unloads to dike

Distance of soil source to dike (meters)	Capacity per labourer for 8 hours day work (cubic meters)
1 – 100	6.5
101 – 200	5.5
201 – 300	5
301 – 400	4.5
401 – 500	4

II. Cut and fill levelling using flatboat (Figure 13 c)

This is usually done for levelling especially where there is a creek in the pond under construction that needs to be filled from a higher portion of same compartment. This operation consists of one man cutting soil into cubes, loading them into the flatboat and tipping and/or overturning the flatboat for automatic unloading. This is almost twice as fast as diking as the labourer saves time in unloading. There is no need to individually handle each cube to unload.

Distance of soil source to unloading point (meters)	Volume (cubic meters)
1–100	11
101 – 200	9
201 – 300	8
301 – 400	7
401 – 500	6

The above figures were taken from actual pond construction experienced in Central Philippines. It has been consistently proven - that one person working alone has higher output than his share in a gang or collective output. The disadvantage only is on the amount of equipment needed for each labourer. In most cases, a gang of 12 labourers is usually provided with 5–8 flatboats only.

III. Some innovations in diking and levelling

Some of the ways commonly used in contract work by the fishpond owner to assure sound pond construction in both diking and levelling are as follows:

It is commonly accepted or practiced to have clearing and puddle trench for main dikes. This operation is usually included in the contract but the pond owner usually has his own people (future caretaker) and not member of the contracting group, to do this particular job. This assures a well-worked puddle trench and clearing of all organic and vegetation matter on the dike path (Figure 13 d).

It is also common practice for the pond owner to provide a soil “receiver” in diking. His “receiver” is his own man of confidence and usually the future caretaker in the project. Usually he pays the “receiver” higher daily rate of wage than the contracting labour force. This is important in that, the future leakeages on the dike are minimized with the loyalty of the receiver with the pond owner. The receiver's job is to receive the soil cubes from the contractors and he forcibly throws these mud cubes into the dike and closes all voids by stamping with his feet. He assures proper soil bonding between the puddle trench and the new dike material. He also removes all small roots and organic matter that come with the diking material. It has been observed many times in contract diking where measurement is done on dikes, that in the absence of the receiver there are too many voids in the dikes and also willful putting of tree roots and trunks is sometimes practiced to increase volume and swell work accomplishment for more pay.

For levelling by “cut and fill” the receiver or supervisor in this type of job usually has a water depth gauge (Figure 13 e) to assess work accomplished. He (receiver) measures the level of the fill material that is dumped by the flatboats and directs incoming boats to areas where they should unload. From experience he knows how many percent (usually 30%) to allow for loose fill so when the soil has settled and the pond is drained for final levelling, very little labour is necessary.

The receiver or supervisor also controls the water depth in the work area especially if payment is by volume, measured at the excavation area. By controlling the water depth he can control the depth of cut and also of the “fill” quite accurately and minimize inaccuracy of measurement to a great extent.

Usually there is one receiver for every 10 flatboats. Very often when the difference between high portion and portion to be filled is less than the usual earth cube dimension of 30 to 40 cm sizes (12 × 16 inches) this “stripping” method of levelling is adopted (Figure 13 f). The above is done for convenience of the labour force. It is economical to cube soil to the usual depth and levelling the pond later than attempting to excavate only 1/3 or a portion of the usual soil cube size.

The usual allowance in financing for earthwork for contingencies to have a well constructed pond is 20 percent. This gives the supervisor flexibility and provides funds necessary for the finer refinments during the construction that he might find necessary. This insures good preventive measures for the future stability of the pond.

IV. Implements

Various implements for fishpond construction (Figures 13 g and h) have been developed in various aquaculture development centres in the different countries in the region. Follow up studies on how these implements are used and comparison of their relative efficiencies will be useful.

V. Mechanization in Pond Construction

A. Drag line

Singapore and Malaysia generally use dragline. The operations consist of bringing to site a track-mounted crane. With the crane are many 0.1 × 0.3 × 4.0 to 5.0 m planks which are self-laid by the crane for its own base. As work progresses, the planks are self-shifted by the crane so that it is resting at all times on a series of planks preventing it from bogging down in mud.

This particular equipment is particularly good for canal digging and deepening. Hence it is suited for excavating shrimp trapping ponds in order to have deeper water. However, it is not practical for large-scale within-compartment-levelling because of its being too slow and unwieldy. It is by design, an equipment for in-place working. It is good for semi-permanent location jobs. There is now in the market a crane mounted on LGP (low ground pressure) tracks. This makes the crane more maneuverable in swamp areas and cuts its non-productive plank-transferring time by half. This crane can be equipped with clamshell buckets.

B. Dozer-crawlers

This particular equipment is good for levelling provided the loading capacity of the soil is such that it can support the equipment. Later versions of these equipment have shuttle clutches which allow the operator to go forward under load then to rapidly reverse speed by a simple shift of a single lever. Formerly, this entailed declutching, gear shifting and applying the clutch. The time in shifting has been reduced to a third in this new system.

Most crawler manufacturers have now incorporated LGP tracks to their line of crawlers. On LGP, the ground pressure usually is around 0.28 kg/cm² (3.98 pounds per sq. inch) or 15 percent. The LGP crawlers come in a variety of sizes, horsepowers, etc. The smallest among them is 20 BPH to as large as 200 BPH. One has therefore a good choice to suit the area to be developed or the transport situation to the work area. In some instances, several small LGP dozers are chosen over a few large ones because the job site may require transporting of equipment by raft or on bridges which have limited load capacity.

C. Hydraulic ditchers, backhoe, shovels, cranes, loaders, etc.

These are also equipment that can be used to advantage in fishpond projects. One advantage the hydraulic equipment have over cable cranes are their fact action and flexibility to adapt to a variety of situations. These can also be adapted with clamshells and grapplers and can be used for uprooting small tree stumps.

D. Scrapers, dumptrucks, wheel-type loaders

These may also be used effectively where soil conditions permit.

E. Suggestions on mechanization

Much waste has been observed in the use of mechanized equipment. In order to be able to adopt this method with success, one must know the following:

capacity
limitations
point of maximum range
ground pressure
working conditions
amount of work to be done
type of work required

There are equipment now specially fabricated for reclamation and swamp work. These types can be used in mangroves effectively. However, one should be conversant with the different types of equipment and be able to judge critically the type of equipment needed after seeing the project area. There are some large equipment which can be taken apart into several components and reassembled at jobsite. Some cranes and hydraulic lifters are also designed to be barge-mounted leaving their tracks or wheels on the shore.

Then too, one should know the economical range of the equipment. At what distances should one start to think of a loader and a dumptruck combination over a crawler. For example, a crawler is most effective in short distance pushing. It would however be uneconomical beyond about 50 meters due to its track wear and long cycle time. Beyond 50 meters, on volume soil movement, one might want to employ combination pay loaders with several dump trucks. These should be worked out for economy. Scrapers (self-loading and crawler-assisted) are ideal for large projects. Dredges can be used effectively too. Under special situations, jetting pumps can effectively facilitate stump-of-tree excavations. All of the above require a thorough knowledge of the project site peculiarities as well as the different equipment available, their specifications, capacities and limitations. Usually expert advice in this field is necessary.