14.6.1. Reconnaissance (or Preliminary) Investigations The main purpose of such investigations is to screen out the poorer alternatives and to decide the types and amounts of more expensive and time-consuming data (such as stream flow records, topographic mapping, and so on) which need to be collected for making feasibility investigations of the remaining selectable alternatives. A reconnaissance survey will identify the scope of a project plan with respect to its geographical location, project functions, approximate size of its various components, likely problem areas, and time and cost of conducting feasibility investigations.
A complete reconnaissance investigation is, in fact, a preliminary version of a feasibility investigation carried out in a rather short time with less accuracy. It considers all the physical, engineering, economic, environmental, and social aspects related to the project. It is usually conducted with the available data. Collection of some new data, if considered necessary for reconnaissance, is made by preliminary surveys. These may include a simple cross-section (instead of detailed topography) of a stream at dam site, surface investigations of geological conditions at dam site, subsurface explorations for foundation quality at dam site, quality and quantity of available construction materials, and so forth. Preliminary designs are made by using short-cut mehods (using curves, tables, and previous experiences). Cost and benefits of the project are also estimated.
Based on the results of preliminary investigations of alternative project plans, a selection of feasible project plans is made for subsequent feasibility investigations.
