The environmental operational guidelines in this series are presented in the belief that dynamics and change induced by development aims are not without environmental hazards and risks. It is necessary to identify such hazards and risks where they arise and take early steps, in so far as circumstances permit, to contain or reduce them. It is necessary to take early steps, because later attempts at remedial action may be illusory, more costly than preventive action taken at the outset, and, in some cases, may be so costly as to bring into question the overall economic viability of the project.