In the practice of designing mining enterprises often have to compare options with different intensity of construction and development of the design capacity of the open pit for ore. These variants may differ from each other in terms of construction time, duration of the period of development of the design capacity, the amount and time of investment, as well as the amount of commercial ore extracted in the period up to the design year. When comparing variants with different volumes of marketable products, projects usually do not comply with the requirement of identity of effect, i.e. comparability of variants in terms of volume and quality of ore. Approved in 1969 Model Methodology for determining the effectiveness of capital investment proceeds from compliance with this requirement, but does not indicate ways and means of its satisfaction.

The use of mechanical shovels for preparation of new horizons in weak watered rocks (sands, loams) with reduced bearing capacity is associated with great difficulties and requires good preliminary drainage of rocks. Practice of designing and construction of quarries has shown expediency and efficiency of application of advance drainage trenches. Digging is carried out by draglines in loose covering rocks, filtration properties of which provide drainage of rocks in trench sides on the width of excavator's run for the period of excavator's working out of its block. Thanks to this method at the open pits of Sokolovsko-Sarbaisky combine it was possible to reduce the construction time, as the stripping and dewatering works were carried out simultaneously.