The offices of the Drainage and Irrigation Department, the Fisheries Department and some private contractors were consulted on unit cost per work activity, cost of materials and labour.
The estimates in the text table are rough estimates; the amounts stipulated will vary according to detailed plans and specifications in the final report.
Running costs of the pilot project are explained in the following paragraphs:
Quantity estimates on earthwork are rough estimates as no topographic data are available. Pre-construction activities which include topographic and location surveys, water analysis, soil analysis, etc., are not included in the estimate of cost as these activities are under administrative expenses.
Clearing, destumping and disposal of debris using mechanical equipment is estimated at M$700 00 per acre (M$1 732 67 per ha). Estimated duration of this activity is 5 days per acre (12.35 days per ha) per day of eight hours.
Earthwork activities include stripping, backfilling, cutting and levelling. Cutting and filling is estimated at M$2.50/cu yd3 (M$3.27/cu m)3 and at a rate of work activity of 80 cu yds (61.22m3) per eight-hour day by dragline. Cut-off trenching by backhoe is estimated at M$2.00 per lineal foot (M$6.56 per lineal m). This includes backfilling and compaction.
Pond levelling and the construction of the tertiary dike is M$1.80/cu yd (M$2.35/cu m) at an activity or duration rate of 140 cu yd (107.38 m3) per day of dragline.
Table III gives the approximate construction cost of each work activity during the construction phase, including the approximate estimates of the civil works.
9.1 Annual recurrent operating and maintenance costs of pumping for water exchange and for filling the ponds during high water neaps.
It is assumed that pumping for water exchange is done during day high water neaps when the tide level is below the normal pond water level. If 1/4 of the pond water volume is the amount of water to be discharged into the pond by pumping (the same amount to be removed during low tide periods) in a period of 3 day high water neaps, (15 hours), the pump discharge rate would be
Maximum pumping head is 1.9 m = 6.23 ft
Horsepower of 2 pumps required:
= 29
Horsepower of one pump = 15
Power required with 2 pumps working, allowing 15% excess,
= 0.746 × 29 × 1.15
= 24.87 kwh. (say 25)
Cost of power consumed at 0.12/unit (kwh.) per month, 15 hrs /week,
= 25 × 15 × 4 × 012
= M$180
Cost of power consumption per year,
= M$180 × 12
= M$2 160 00
The above estimate is the minimum and basic requirement for pumping for water exchange; this serves as the basis for computations for increased/ decreased cost should water exchange be done at a more/less frequent rate.
Pumping cost of filling the ponds is based on the assumption that although the ponds are to be filled by tidal flow, this situation is not at all times obtainable at mean high water neaps of 1.8 m, the ponds are filled to a depth of 1.00 m, 0.60 m of additional depth of water would be obtained by pumping and this quantity of water required is,
For (11 × 2) nursery ponds of 65 m × 85 m × 0.60,
= 13 × 2 × 65 × 85 × 0.60
= 86, 190 m3
For (11) nursery ponds of 13 m × 85 m × 0.60 m,
= 13 × 85 × 0.60 × 11
= 7 293 m3
Total additional volume of water required to fill the ponds by pumping,
= 86 190 + 7 293
= 93 483 m3
= 20 566 260 gallons
The time required to fill the ponds at pump discharge rate of 28.93 cu ft/sec (28.93 × 6.22 × 60 = 10 796 gpm)
= 1904 minutes
= 31 hours
Cost of power consumption (for filling once),
= 31 × 24.87 × 0.12
= M$92.52
Cost of power consumption (for filling ponds twice),
= 92.52 x 2
= M$185 00/yr
Annual recurrent operating and maintenance expenses:
| Pump attendant | ( ) |
| Water exchange | M$2 160 00 |
| Filling.the ponds | 185 00 |
| Repairs & renewals of pumpsets at 2% of capital cost | M$ 400 00 |
| Annual recurrent operating maintenance expenses | M$ 2 745 00 |
| (say M$3 000 00) |
