Three phases of construction were proposed by the local consulting firm, ARCH.CENTRE, of Riyadh, in its Design Report (Section 2.0, p. 8).
Phase I included the following specific items:
generator building and power generator system and mechanics quarters
seawater intake system and pump house
gravity flow sand filter
fibreglass raceways and tanks
seawall
and necessary site works.
In reviewing the project operations, the proposed construction, the budgets, and the schedule of the project implementation with the Chief, Management Support Unit, FAO Riyadh (Mr Salin), the Project Operations Officer, FAO Rome (Mr Ziesler), the Project Manager, FAO Jeddah (Dr Allen), and the Project Co-Manager, Ministry of Agriculture and Water, Jeddah (Mr Al-Thobaity), it was clear that Phase I could not be reviewed singly out of the context of the whole project construction. Furthermore, the preliminary discussion of some major cost savings because of practical and cheaper options or alternatives to the design which would reduce the capital costs substantially, and the fact that funds were available within the present time-frame of the project which would end in July 1986, reinforced the importance of reviewing the construction project as a whole. The author was therefore redirected to review the detailed drawings elaborated by ARCH.CENTRE for the complete construction, and to recommend necessary adjustments on the basis of his own observations. It was recognized that the author was not an engineer, and therefore would confine his review and evaluation to the proposed principles and concepts for the operation of the facility for the stated goals, and would not comment on the design engineering of the proposed systems.
The author recommended that there was first a restatement of the goals of the project, as the purpose of any facility was to assist the project staff to meet its goals - and not for the facility to direct the goals. From the ensuing discussions with the project staff, the following project objectives were defined:
The immediate objectives of the project are:
to operate a demonstration unit for the production of Tilapia spirulus with a minimum monthly output of 0.5 t-to be supplied to local markets;
to operate a production system for Tilapia fry, with a minimum monthly output of 15 000 for sale or donation to the private sector. This is in response to many previous inquiries for advice on techniques and resources to start a farm. If not requested, these fry resources will be absorbed into the many sub-projects and trials;
to begin a programme of applied research and development by broadening experience in (a) hatchery operations, (b) grow-out systems, (c) polyculture practices, but limiting its activities to valuable commercial species in the country, namely the mullet, the rabbitfish, the grouper, and the indigenous shrimp. It is not anticipated that the project staff will start to work immediatly on the reproductive physiology of these fish in captivity; they will begin with the capture and husbandry of the broodstock, general broodstock handling and egg sampling, etc. Active work in reproductive physiology and culture is not anticipated until the new facility is constructed and a hatchery/wet laboratory is available.
Discussions followed on what was required by way of facilities to meet these goals, but recognizing that the facilities would be all or part of those which had been designed into the project site drawings prepared by ARCH.CENTRE. This was not difficult to achieve, and further reinforced the ability of the proposed project to reduce its total cost by removing certain features and facilities without reducing the overall project objectives, both short-term and long-term.
A full set of Final Design Drawings and Specifications (with the exception of the Estimated Costs) was available for the consultant to review. It should be noted for future reference that any proposed changes at this stage of the process of design will necessitate costly redesign and delay the project. Such reviews should be made at the end of the Preliminary Design stage, before all the detailed drawings and specifications are made and the final costs are estimated from the bills of quantities. However, the author was given the terms of reference to review the drawings as proposed.
The author noted that there were several concepts and features to question with the project drawings as a whole, and also improvements possible for certain details. These points are dealt with one by one in the following pages.
Any reference to a design concept was missing from the supporting project documents. This is the principal document on which the entire design is based. It describes the purpose of the facility, and the parameters within which the facility is to function. These parameters not only include the requirements for the site and define all building spaces, but also establish the frame within which the facility is designed according to the requirements of the livestock to be raised.
Knowing some of the background of the project's evolution, and the fact that two previous attempts at design development (by Hechanova in 1981 and Balarin in 1983) have been prepared, the author believes that the design architects and engineers presumed that all the biocriteria had been assembled and approved previously, and that it was simply adequate for them to use the concepts of the two previous designs and encompass them into one professionally prepared design complete with specifications. The result is that the final design is a composite of the two original concepts suitably used to cover the existing available space with little real knowledge of their purpose or use.
The concept has been complicated further by the design engineer's own professional responsibility and knowledge without any reference to such practices in aquaculture. For example, a chlorination system was added to the intake seawater system to reduce biofouling. Although this is good engineering practice in the design of seawater intakes for power plants or desalination plants, the literature shows that such industrial systems are impractical and even dangerous for fish farms 1.
1 Nash, C. 1974 Chlorination and power plant fish farms. Prog.Fish Cult., 36 (2): 92–5
Fundamental to the successful operation of any fish farm is the delivery of high quality water. The design is based on a total site requirement of about 0.49 m3 /sec of high quality seawater. To achieve this, the proposal is for a 70 cm diameter seawater intake pipe running for over 500 m from the edge of the outer reef, opening 4 m deep below water mark to the pump house. Although the cost of this is not available, it is certainly expensive. It is probably unnecessary.
The better alternative for the intake system is to take seawater from relatively shallow wells located on the edge of the shoreline, or in the sea (sited preferably on the proposed boat ramp). Such wells, probably about 5 – 12 m deep, can supply all the seawater the site will need, and readily available submersible pumps can be used. These wells are ideal in coral beds as the coral filters the water effectively as it is drawn towards the pump. The water is also often a few degrees cooler than surface seawater. Wells are used at the Mariculture and Fisheries Laboratory of KISR in Kuwait, the Oceanic Institute in Hawaii, most marine aquariums, and most marine centres located on sites with foundations of coral. Two subterranean seawater wells are now installed at the King Aziz University, Marine Science Centre, about 20 km south of the project site.
The recommended action is for the Centre, through its parent Ministry of Agriculture and Water, to obtain government help to drill a testwell and make pump-tests in the northwest corner of the site. Failing prompt help from the government, the project should contract privately for a test well to be drilled and pump-tested, and the seawater analysed. Oxygen level and salinity are two important test criteria and should be as close to normal seawater as possible.
NOTE: Should the seawater-well exercise prove to be unsuccessful, and in view of the disproportionate cost of the original seawater line, the second alternative should be an anchored dual pipeline (each one alternating as a redundant line for cleaning by leaving filled and static) running from the pumphouse to a protected intake rose above the substrate in the centre of the lagoon where the water is about 4 m deep. Although not ideal, this system could suffice for several years until progress and expansion plans might merit a major system through to the reef.
A second point to question in the seawater system is the inclusion of the chlorination system. Although there is little in the documents which explains its functioning level, it is probable that its inclusion is based on its necessity for the design and operation at the many desalination plants in the country. Experience in using chlorination systems in seawater systems used by fish farms was developed in the UK in 1964–1970 in association with work at power plants at Carmarthen Bay (Wales) and Hunterston (Scotland). This resulted in the use of continuous chlorination systems injecting to levels of 2 ppm free chlorine at the intake and anticipating a level of 0.02 ppm free chlorine or less in the fish farm tanks. However, the close control of such a system in seawater is far from accurate, and the resultant levels in the farm are variable depending on many factors, for example, the chlorination demand of the standing biomass in the tanks. Although low level continuous injection is the only acceptable method of chlorination for the seawater system, in view of the proposed changes to the design of the system it becomes a redundant design feature. Even if wells become impractical, the dual intake line system will also make chlorination unnecessary.
A third point with regard to the seawater system is the distribution pipework system around the site. It is proposed to construct a costly concrete flume channel elevated throughout the site, locating the flume at the centre of the pond berms. In addition, the emergency seawater system from the filtered seawater reservoir is a piped system. As the seawater is obviously under pressure as it carries through the pumphouse, that advantage should be retained in a typical network of standard size pipes and valves (in PVC plastic). Although biofouling in the pipes is reality, the method of intake through subterranean wells will eliminate much of this problem in the short term, and in the long term the pipes can be cleaned by rodding if the design of the system includes inspection and rodding end-caps to each run of pipe.
With the recommendation that the distribution pipework system is replaced with standard pipe and valves, the fourth point of consequence becomes the gravity sand filter. The sand filter is an ‘open’ system and therefore breaks the pressure generated by the pumps for circulating the seawater. This system should be replaced with standard seawater pressure filters. These large units are used in almost all aquaculture facilities, and can be placed in parallel and isolated for backflushing without reducing the volume of incoming seawater required by the plant. If seawater wells are applicable then the filtration requirement is likely to be minimal. If the open seawater pipe system is used, then good filtration will be important. A second alternative option to the filtration system proposed is the construction of a dual headbox sized for the water requirements of the entire site.
The first chamber (with overflow) acts as a settling and filtration unit, and the second as the header reservoir for the water only demanded by the systems on site. This system, of course, breaks the water pressure and the subsequent distribution is by gravity flow. Although this is also a valid approach to gross filtration, the recommendation is for the inclusion of sufficient sealed pressure filter units (e.g., Baker filters).
The fifth point of concern with the saltwater system is the proposed filtered seawater reservoir This large reinforced concrete structure containing over 200 m3 of emergency water and complete with its own pumphouse and pipework distribution system, is costly and has little real value to the project. With an adequate intake system, spare pumps, a spare generator, filtration unit, and well-designed distribution system, (together with the need for good engineering maintenance, and an alarm system which will bring automatic and human response), the emergency filtered seawater storage and distribution system are redundant.
It is recommended that the filtered seawater reservoir and its emergency system are excluded totally from the design, and that the site uses more conventional means for meeting emergencies, namely an alarm system with back-up generator and pumps.
The sixth and last point of concern for the seawater system is the proposed oxidation pond and discharge canal. While it is important to consider the environment which receives the wastewater from the centre, the refinement of a large oxidation pond is unnecessary at this stage in the site's evolution and use. Few, if any, of the world's major aquaculture centres have such facilities. Most simply discharge their wastewater back into the sea in open drainage channels or through subterranean dispersion wells. It is recommended that the oxidation pond with its discharge canal is excluded from the design, and replaced with a simple discharge canal emptying into the sea across the beach at a point which will minimize algal growth and subsequent unsightliness.
NOTE: Reference to the capacity of the seawater system is deferred until discussions of the Production Units (see 2.5).
There are four types of production units included in the design of the project. These are:
It is proposed that no change is made to the number and location of the fibreglass raceways and tanks. These tanks and raceways are already purchased, and it is intended to set up this unit on a temporary basis so that it can be used during the construction of the project. The tanks will be located temporarily near to the existing siteworks and will not interfere with the contractor during construction.
After construction, they will be relocated on the ground prepared by the contractor, and connected into the new seawater and drainage systems. As the fibreglass raceways and tanks are to be used to demonstrate the production of Tilapia species, there is little purpose in completing the Baobab fish culture unit as designed. The circular tanks and raceways which make up the unit are, however, useful facilities for raising a number of marine species of fish, or for specific purposes, such as holding broodstock, etc. It is recommended that this area maintains some flexibility and all the available space is not committed to the proposed sizes of tanks. It is recommended that only the six small tanks (20 m3) are considered as fixtures in the design, and that the rest of the space is left with the flexibility to consider other units. This space will be supplied with drainage channels only, and the seawater lines and aeration lines be capped off and remain ready for the subsequent use.
The design proposes eight fry ponds and nine grow-out ponds, constructed with raised berms and lined with butyl (or other) liners. As no report is available, the original purpose of these ponds is not known to the author. However, the progress of the project with the culture of marine fish in cages, and the present advances of aquaculture technology in this direction, strongly support the concern that these types of facilities for marine fish species are a poor choice. Although there is the good possibility that marine shrimp could be cultured in lined ponds in the country, there is little scope for such ponds for marine species of commercial interest. It is true that such ponds might have some specific usefulness, such as trials with marine shrimps at a later date, or the holding of broodstock, or the raising of small invertebrates to use as live food organisms in the hatchery. Therefore, it is intended that a few are retained. It is recommended that the number of fry production ponds and grow-out ponds are reduced to four of each type. This will permit replicated trials should the need arise. The volume of the grow-out ponds should be reduced to twice that of the fry production ponds to create an experimental module.
In association with the fish ponds is a larger pond which acts as the raw seawater reservoir. In view of the changes being made to the seawater system as a whole, and the alternate options for emergency situations, it is recommended that the raw seawater reservoir is eliminated altogether. This will allow the remaining fry production ponds and grow-out ponds to be located close to the hatchery and the other facilities.
It is recommended that the raceways are also eliminated. The concrete design proposed for the raceways is costly, and the facility has little flexibility. Furthermore, the majority of aquaculture work in raceways is more suited to freshwater fish, where there is little alternative option but to pump the water required. Sea cages are taking the place of raceways in marine aquaculture - as the cost of moving the large volumes of water required is free. In view of the proposed project plans to continue and expand its sea-cage work, the use of the raceways diminishes significantly. Furthermore, the raceways as proposed would utillize about 40% of the site's water budget (0.22 m3/sec out of 0.49 m3/sec), and therefore would be a continuous burden on the operational costs of the site without much practical return in technical advancement. The need for raceways in the future could be fulfilled by fibreglass units assembled on the work-pad adjacent to the fish culture unit.
The changes proposed in Sections 2.3 and 2.4 have a significant effect on the logistics of the site operations in terms of water use. In summary (and using the data provided for the project design), the water budget is now as follows:
| Fibreglass raceways and tanks | - 0.0518 m3/sec (no change) |
| Fish culture unit | - 0.0635 m3/sec (no change) |
| Ponds (fry production) - 4 only | - 0.0150 m3/sec |
| Ponds (grow-out) - 4 only | - 0.0730 m3/sec (old size only) |
| Ponds (raw seawater) | - 0 |
| Raceways | - 0 |
| Total minimal water budget (without hatchery) | - 0.2033 m3/sec. |
This water requirement, with a small addition for the hatchery (0.03 m3 /sec) and a margin of safety, significantly influences the sizing of all the seawater lines, the pumps and the generators, etc. It is recommended that the entire seawater system is redesigned from calculations derived for site seawater requirements of 0.250 m3 /sec maximum, evenly distributed. It will be noted that the revised siteworks are now confined to the northern half of the project site, leaving the southern half for expansion. It is not recommended that the revised seawater system includes hypothetical demands for future expansion. It is very probable that the water demands of any future expanded site will be met by another seawater well and separate distribution system.
The distribution network for both seawater and freshwater will be in standard PVC plastic pipe, regulated with standard PVC valves. The main pipework can be buried in shallow ditches and covered, if advised, but protected from the danger of all vehicles moving about the site. No pipes should be buried in concrete. There must be many inspection entries and capped ends for rodding. All pipework above ground must be firmly fixed to eliminate any chances of breakage from vibration or physical damage. All outlet valves to experimental units will be the standard ball valves, and of common dimensions to minimize cost; for example, there can be more than one standard inflow check valve per unit.
Project drawings detail elaborate concrete formwork for the location of the fibreglass raceways and tanks, and the fish culture unit. This is not necessary. The site is flat and the ground is firm. Tanks of these dimensions (20 m3 or less) can be securely set on graded ground covered with fill (sand), and crushed coral for walkways. However, all the tanks have bottom outlets which must feed into open drainage channels. Although the drainage channels must be carefully constructed and sloped, there is no need for an expensive concrete working platform. The design engineers should recommend the best cost option through their design.
The design of the wet laboratory/hatchery is good in that the main space is open and flexible with overhead life-support services, and floor drains. Culture units can be readily moved or replaced as techniques improve. One criticism of the hatchery is the integral reservoirs for seawater and freshwater within the building. It is preferable if these are external units. In order to minimize the need for major changes to the design drawings (as the support for the reservoirs requires considerable strength and reinforcement based on the calculations of loading), it is recommended that the areas below the two reservoirs are not utilized as storage and aquarium space, but are open to the exterior only. To compensate for the ‘lost’ space below the two reservoirs, it is recommended that the area of the hatchery is increased accordingly.
In view of the proposed changes to the facilities, the simple discharge canal recommended, and the available existing beachfront for the revised number of ponds, it is recommended that the sea wall is eliminated.
The proposed changes to the operations of the project will require some new facilities. The new additions are minor, but are brought about by the trend towards increasing the activities in the cages offshore. The boat ramp and hoist become more significant as there will be increased movement into the sea with cages, nets, and feed. The proposed boat ramp and hoist areas should be re-evaluated with this work in mind. Furthermore, a large graded area adjacent to the boat ramp should be planned for the servicing of cages and cleaning and drying of nets, with road access. Other services which will be required around the site are (1) pressure hose outlets (seawater) for the cleaning of facilities and nets; (2) some freshwater hose outlets for cleaning points and washing equipment; (3) some electrical outlet points, for pumps, etc., located in the base of the site lighting fixtures; (4) a place for the location of a portable generator and hoses for emergency use.
A diagrammatic revised site plan is attached (Figure 1). It should be noted that it illustrates the concepts of the revised plan, and is not intended to illustrate the exact locations of distribution lines, valves, drains, etc. The consulting engineers will locate these according to the principles and requirements of professional design, and their experience.
