3.1 Preliminary design
3.2 Final design
3.3 Cost re-evaluation or value engineering
3.4 Construction documents and bid specifications
The second phase of project development is design. Design itself can be sub-divided into as many steps as necessary to resolve all design problems and to Integrate the concepts into a functional facility plan. It is generally recommended that at least two stages are used. These are:
3.1 - Preliminary design, and
3.2 - Final design.
Both stages adhere to all the concepts developed during the planning phase. The remaining elements in the design process are:
3.3 - Cost re-evaluation or value engineering, (which is optional), and
3.4 - Construction documents and bid specifications.
The conclusions, or end products, of the design phase are written reports, architectural and engineering drawings, more accurate construction costs, projected operational costs, and schedules of construction. There are also engineering specifications for materials, machinery, and equipment for each step. The reports will record the evolution of the design process and all criteria and assumptions used.
During the preliminary design stage, major emphasis is upon civil, mechanical, and architectural design. The design of all the mechanical processes (such as the water systems) will also be completed at this time to ensure that they are integrated properly into the structures. Architectural concepts (if required) are developed, and structural systems identified.
All the required site investigations, including the chemical analysis of water, soil analyses, and topography, are made before completing this step. Based upon these investigations, the criteria are developed by the engineers for soil compaction and pond berm or dike construction, and water treatment.
A sufficient number of drawings are then completed to communicate the design concepts. The number of drawings required is strictly dependent upon the size and complexity of the project.
A preliminary design report is prepared with the drawings which describes all the structural components and mechanical processes of the facility, and the ways in which they interrelate. The report should include an outline of materials and equipment specifications which are then used as a basis for revising earlier construction cost estimates. These will now be reduced from the plus or minus 25% accuracy of the Schematic Design (see section 2.5) to about 15% accuracy. Operating cost estimates and the construction schedule are also revised at this time.
Costs and scheduling revisions are again compared with the original financial objectives and constraints to ensure that the project remains financially feasible. If it is not (because, for example, the structures were to be built with reinforced concrete instead of pre-fabricated materials) then the facility design concept has to be altered as necessary.
In some cases, perhaps after substantial soil tests, it is discovered during the preliminary design phase that the project cannot be developed economically. It is then necessary to terminate the project, or to revert back to the planning phase and revise goals. However, if the planning has been thoroughly conducted the chances of significant conceptual or siting changes at this stage of development are remote.
During the final design stage the detailed architectural and engineering drawings (the blueprints) of all physical components of the project are produced. In some complex projects, such as multi-disciplinary research centres, it is necessary to prepare in addition a written final design report. This summarizes the facility as designed.
Virtually all design problems must have been resolved before the end of the final design stage. Sufficient detail must be provided by the drawings and the report to allow reasonably accurate estimates of construction and operating costs, as well as the construction scheduling. All revisions to construction materials, machinery, and equipment specifications are made. The updated schedule, cost estimates and specifications are contained in the final design report.
Once again, it is necessary to verify at the end of the final design stage that the project remains economically viable. If, by some chance it is not, then a decision must be made to revise design solutions or the original concepts, or perhaps terminate the project.
Although it is an apparent and obvious assumption, it must be pointed out that any changes at this stage are most costly. Final design is the most expensive of the planning processes. It is therefore important that complete and detailed attention is given throughout final design. If final design drawings have to be substantially changed or repeated, the costs are disproportionately high compared with the costs of the originals. Obviously if this occurs, then substantial errors have been made during the previous stages and planning phases.
One of the most frequently used ways of maintaining economic viability at this stage (as mentioned in section 2.6) is to develop and construct the project in phases and to ensure that each step of the construction programme is financially viable. However, even to do this, it is often cost effective to design and construct certain basic facilities (such as the main pump house and intake/discharge channels) during the first phase.
This is an optional element in the design process. For large projects, and those which may be having difficulties with economic financial projections, it may be useful to include a value engineering stage.
The value engineering process re-evaluates all the major cost centres in the project to determine if the most cost effective design solutions have been used. For large aquaculture facilities the most problematic cost centre is often the water delivery system to the site. A small team is assembled, representing the major engineering disciplines, architecture, and biology. It is important that these individuals are familiar with aquaculture projects, but were not participants in the design. They are supplied with all records of the project from concept through design. The objective is to verify that the project meets operational criteria, and optimizes cost efficiency both in construction and system operation.
Value engineering is not a time-consuming or costly process. It can result in considerable cost savings to the project by discovering inconsistencies between operational requirements and design solutions.
Recommendations made by the value engineering team should be incorporated into the final design as necessary.
The last stage of the design phase is the preparation of construction documents and bid specifications.
Construction documents and bid specifications are similar throughout the construction industry for any building project, and therefore no detailed description or separate discussion is necessary for aquaculture facilities.
It is important that the detail provided in the construction documents and the bid specifications reflects the standards of the contractors who are expected to bid on the project. Furthermore, it should be borne in mind that many contractors have had no experience building aquaculture facilities, and will not understand the degree of accuracy required for some components. This is most vital for the construction of the hydraulic system and compaction of the pond berms or dikes to meet the specified performance criteria. These requirements have to be conveyed through detailed drawings and specifications. Similarly, machinery, equipment, and material specifications must clearly indicate where no substitutions are permissible.