Following on from the project concept as defined, and the production programming specified in the previous section, the detailed design can be developed. The project characteristics will be described in several major categories: hatchery, .ongrowing units, service buildings, and other services, and are described in turn. Overall site layout (see earlier) is shown in more detail in the Appendix in which the hatchery, service buildings and fingerling raceways are placed on the higher ground east of the inlet area, and ongrowing raceways grouped in modules in the wider open area to the east of this. The following descriptions are based on an annual 50 t production, of which the 5 t project described in the appraisal report forms the preliminary stage. Budgetary aspects are dealt with later.
A modular hatchery of an annual 50 t ongrowing capacity is proposed;- in its basic form it is designed to accommodate the production of approx. 250 000 weaned fry with generous margins providing the potential for a longer term activity capable of supporting 100 t ongrowing capacity. Fig. 8 shows the standard layout which can be replicated on the adjacent area. Specific design details are provided in Appendix 2.
The hatchery building requires a good quality semi-permanent structure - ideally a prefabricated or panelled agricultural or industrial workshop type building, with an open span construction, screeded concrete floors and washable interiors. A good quality green-house may be considered if cost becomes critical, though durability will not be so good. As shown, the building is subdivided into sections for laboratory, feed culture, services, and main stock rooms. Broodstock tanks are located adjacent to main raceways.
Fingerling rearing is provided in banks of 1.5 × 15 × 1 m deep raceways of block or reinforced concrete construction, from which stock is transferred to the main groups of raceways, of 3 m × 40 m × 1.2 m deep of similar construction. These raceways are described as continuous and are not terraced, though if site gradients cannot be moderated, a single division, forming two 20 m sections may be acceptable. Two expanded metal walkways run across each module; one at the upper, supply channel end, the other approximately half way down. Both walkways have bracket attachments for feeders.
The first phase development of the site would use only the upper half of the main quarry floor area, the lower half forming a semi-intensive pond fed from the waste from the raceway system. In the second phase, this area will be utilized for further raceways and the additional water supplies and drainage provided accordingly. Third phase development would involve the use of the area to the west of the main intake.
The service building comprises the main office/service block, which contains office, washroom and canteen, workshop and stores, a feed store capable of holding up to 75 t of feed (6 months supply for Phase I), and a generator housing. A guard/reception building is sited at the upper entrance. Fig. 9 shows details of the main building.
The seawater supply system comprises the main pumping station and supply pipe to the site, the distribution channel to the fingerling and. ongrowing raceways, and the internal supply system to the hatchery facilities. This-latter also includes a higher quality supply, where raw seawater is filtered and sterilized, and a recycle system in which heated seawater is treated and re-used within the hatchery. Fig-. 10 shows the main water supply system; Table 4 summarizes the main flow requirements, critical dimensions and specifications of main water supply and drainage elements. Fig. 11 shows the details of the high quality water supply.
The seawater pumping system is based on continuously rated electrically driven centrifugal pumps, either of submersible or surface mounted design, depending on availability. These are supplied by mains power with generator back-up. The final layout of the pumping station will depend on the comparative . cost of construction; Fig. 12 illustrates a simple wet well System which will offer a high level of protection from onshore exposure. In this system either type of pump may be installed. Generally submersible pumps would be preferred as they are robust, need no protective housing and do not require a suction pipe to operate.
The main pumping duties and the suggested pump sizes and power consumption based on a working head of 15 m are summarized in Table 5. This arrangement provides for reasonably flexible operation over the whole seasonal cycle, with adequate standby capacity.
The main design characteristics of the hatchery recycle system are summarized in Fig. 13 and Table 6; Table 7 summarizes main tankage required and Table 8 summarizes the main heat inputs required during the production cycle. Heating is simply supplied via industrial or agricultural space heaters and/or electrical immersion elements, with good temperature control in main reservoirs. For greater security, space heaters would be preferred.
Details of the proposed air supply system are summarized in Table 9. Standard electrically powered centrifugal blowers are used, with adequate backup capacity. Fig. 14 shows the aeration system.
Total power requirements and power supply details are summarized in Table 10; Fig. 15 outlines the distribution system. Mains power is normally used, with back up from diesel generators, automatically switched in the event of mains failure.
Summaries of other services and equipments required for the project are given in Table 11 and in further detail in Appendix 2, which also identifies those components required for immediate use. Appendix 5 provides a list of equipment required for the support project (Project LIB/86/008) associated with the aquaculture.
