Details of the site, its Layout, and topographical details are shown in Fig. 2, and in more detail in the Appendix accompanying site drawings. This particular location was chosen within the quarry complex because of:
- ease of road access to the site
- access to the shore through quarry cuttings
- a relatively flat, easily developed floor
- relative freedom from quarry spoil and rubbish
- relative ease of forming water supply and drainage
Background environmental and other factors are given in the evaluation report. Table 1 summarizes the most critical data. There will be certain microclimate-modifications to these within the quarry area, but these will not be expected to be significant for the intensive form of aquaculture proposed. The effects of climate on hatchery operation-and-on overall production planning will be examined later.
The overall layout of facilities on the site is affected by a number of considerations:
- relative levels: generally, the site slopes downwards from west to east, and from south (land side) to north (shore side) - this suggests supply from the west, with drainage from the east of the site - this coincides with the general shore current drift in the area (though this will have to be confirmed for the specific location). The slope of the Land also lends itself to raceway systems, possibly of terraced form, taking advantage of a downhill movement of water;
- structure/shape: there are two main cuttings between the quarry floor and the sea, one approximately half-way along the quarry, the other at the eastern end. The area between these (approx. 1.3 ha) is the most immediately suitable for use, and can conveniently be aligned with west-east supply and drainage. The main disadvantage to the structural features of the site is the presence of three residual stone pillars carrying the overhead power cables, which will be too difficult and costly to remove, and will therefore create an obstacle to full use of the site area;
- stability of walls: much of the perimeter of the site is bounded by vertically cut walls, up to 10 – 20 m in height, above which lies loose fill, broken blocks, and dumped material. As all of this material is potentially unstable, and would be difficult to clear completely. Sensitive areas, such as roads, buildings, access ways,, and open tanks, should not be placed too close to the walls;
- quality of footings: a considerable amount of site work has been done since the earlier mission, creating a change in the specific site levels, and in the proportion of the site covered by compacted fill. In some areas, fill is up to 1 m in depth. While such areas might conveniently be used for cutting drains, etc., their use together with the rock pan floor may cause problems of differential settlement if high ground loadings are imposed.
In view of the altered site levels, of the need to ensure effective modular development of facilities, and of the additional need to rehabilitate the site effectively from the outset, a layout is proposed (Fig. 3) and Appendix, in which water is pumped from the western cutting up on to the higher land to the east, where office, store, Laboratory, hatchery, and fingerling rearing units would be: established., and from there to the-Larger area (originally proposed for pond use? to the east, which would progressively be developed for ongrowing raceways. By establishing the initial phase along the southern edge of this area, the lower-Lying area to the north may be used as a. semi-intensive pond until it is required for use as raceway space. The waste channel for the complete site would run along the northern (shore) edge, discharging via the eastern cutting, through a settling pond. Although this arrangement involves relatively high pumping heads, it will be otherwise impossible to make efficient use of the cleared site area. If local current conditions suggest an alternative supply/discharge alignment, a similar layout could be used but with the pumping station to the east, draining to the west.
This layout is capable of providing approximately 6 500 – 7 000 m of usable water area for ongrowing, representing a theoretical maximum output of 100 – 120 t under standard operating conditions; up to 200 t under optimal conditions. Efficiency of site use is hampered to some extent by the rock pillars present in the southern part of the site; there would also be a margin near most of the steep wall faces.
The system proposed is based on raceway modules of nominal capacity 10 – 12 t (up to 16 – 18 t in optimal conditions), which can be grouped together to provide larger units of production, while the hatchery and finger-Ling facilities are based on units of 50 t production. Hatchery units can be expanded at the Later stages, or may be optimized towards an output Level sufficient for up to 100 t production. More details of the specific design of these components are given later.
The site can thus be developed relatively easily in stages, of which the present pilot stage may be considered the first. It will be a matter of choice whether the project is developed continuously towards its final size, or whether several separate phases will be carried out. If the aim is to achieve rapid expansion, the first would be preferred, limited only by the availability of staff, stock, feeds, and other resources. Full details of implementation schedules are discussed later; for the purpose of identifying the scope of the present project, the pilot stage can be defined as comprising:
- basic office/servicing unit
- single hatchery unit
- single fry raceway unit
- ongrowing raceway modules utilizing the southern side of the site (from 5 t initially, to approximately 50 t production)
- water supply and drainage for all of these facilities
- other services for these facilities.
It is assumed that general Landscaping work, provision of infrastructure for subsequent phases, etc., which may be carried out at the same time as the construction of the pilot phase, will be considered separately for budgetary purposes.
In the Longer term, the present site may be developed further by using the adjacent workings to the west, though drain water should ideally be discharged through the eastern cutting and would thus have to be pumped across into the present site, as the extension site lies at a lower level. However, this disadvantage is partially offset by the lower-pumping head required to supply water to the site. When the quarry is fully developed, a target production of 200 – 250 t may be realized, though further expansion westwards should be assessed to determine whether other quarries, or other sites nearby, might prove more suitable.
The hatchery facilities, if fully déveloped, would be capable of supplying up to 200 t production. This could easily be increased further in the longer term by using the adjacent sites to the west. There could be specific advantages in concentrating hatchery production around existing infrastructure, as additional production could be gained less expensively and more reliably than by using sites elsewhere. The present project could therefore provide the basis for a regional fry supply centre in the Longer term.
