After collecting all relevant site data, it is important that all the facts and information be arranged and recorded in an orderly manner. Survey notes should be used in the assessment and in plotting plans in accordance with standard procedures. Time can be used more efficiently by preparing the engineering plans to scale and in detail, as the field data is obtained. This will generally suffice for final design and preparation of plans for the project.
For many projects the use of approved, standard work sheets can (and should) be used to record all of the necessary data. This information can then be used later in the project, if problems arise.
4.3.1 Analysis of data
It is important to consider the relationship of the proposed solution to the overall use of the land, when reviewing the collected data.
• Detailed review of the data is necessary to determine: • the type or series of measures required;
• the limitations in location and size of facility imposed by the site; and
• the design procedures and criteria that apply to the proposed structures or practices.
Throughout the process of analysis, consideration needs to be given to alternative methods and construction materials. A small, additional outlay in installation cost may prove a saving in future maintenance and operation.
4.3.2 Design
Design procedures include:
Documentation 79
2 hydraulic calculations to provide information on control, capacity, and safety; 3 structure design (see Section 3);
4 location, dimensions and elevations of important parts of the dam wall and its accessories;
5 estimate of material quantities (see Section 3.5); 6 estimate of construction costs (see Section 3.6); and
7 specifications for materials and construction (see Appendix 2).
It is important that design calculations be documented in an orderly manner and checked for accuracy.
4.4 CONSTRUCTION DOCUMENTS AND DRAWINGS
The preparation of the construction plans or drawings provides a detailed record of the design and structural requirements of the dam. This allows a contractor who is unfamiliar with the project to lay out and ensure that the work is constructed as designed. Construction drawings for complex dams usually involve drafting the topo- graphic, cross-section and profile data collected in the investigation stage. Additional layout and detail drawings, as required, may be prepared as the design calculations are completed.
For many on-farm measures, the preparation of the construction drawings may be simplified by using approved standard pre-design layouts. The standard drawings require careful review to see that:
• the plan will fit the site so that the structure will function properly; and • all required dimensions, elevations and modifications are complete.
A common error in the preparation of the construction drawings is the omission of required details, sections, and dimensions. All plans should be carefully reviewed for completeness and accuracy.
4.4.1 Specifications
In addition to the detailed construction drawings, the construction plan often requires written specifications to clarify how the work will be done, the quality of workman- ship, and methods of testing (see Appendix 2). Another important component of the specifications is the required quality of the manufactured materials that will be used in the work.
For small projects, the material and construction specifications may be docu- mented in the form of notes on the drawings. For larger projects, the preparation of a separate specification document, or the use of Standards Association of Australia (SAA) or ANCOLD or State guidelines are more practical. In all cases, readability of drawings is vital to the success of the project.
80 Small Dams
4.4.2 Checklist
The amount of detail required in the construction plans will vary with the type and size of the project. However, all projects regardless of size should be adequately planned. The following list may be useful in checking the adequacy of the drawings and specifications.
1 Can the farm be located from the plans? 2 Is the project site clearly shown?
3 Can the survey lines be relocated and the job pegged for construction as designed? 4 Are all dimensions and construction details clearly shown?
5 Are material and construction specifications complete for all parts of the work? 6 Are material quantities shown?
7 Has the title block been completely filled, including the date and who designed, drafted, amended and approved the work?
8 Has the cost estimate been prepared?
9 Have licence/permit documents been lodged with the responsible authorities?
4.5 FINAL REVIEW AND APPROVAL
Before the construction plans are delivered to the contractor, the design and construc- tion plans should be reviewed by an independent designer.
When required, plans should be submitted to the appropriate responsible author- ities for approval. The construction plans should also be properly signed and dated by all parties involved in their preparation and approval.
4.5.1 Records
A complete copy of survey notes, useful basic data, soils logs, design calculations and other relevant data, including a copy of the plans and specifications, should be assembled and filed in an orderly manner.
All dams or practices, regardless of type or kind of material, will require mainte- nance. Changes or additions made during construction should be recorded in coloured pen on the office copy of the plans. These ‘as constructed’ plans are often useful when making maintenance recommendations to the contractor. They are also useful for structural design improvement and for the evaluation of hydraulic performance. Moreover, complete ‘as constructed’ records may be valuable in case of a legal dispute (see Section 10).
Section 5
Construction
Despite the apparent super-efficiency of modern equipment, a high proportion of dams built today do not seem to have the long life of those small dams constructed in the old days with a horse and scoop, followed by a driven flock of sheep to give compaction. Although bulldozers, scrapers and tractors are heavy machines, they are designed to create as little pressure as possible and are usually used when the soil is at its driest – a time when soil moisture is well below the optimum for good compaction. The modern answer for the compaction process is a wheeled tractor or sheepsfoot roller, particularly where troublesome soils are encountered, and a crawler tractor to carry out the excavation.