Effect of Geotechnical Risks on Project Investment Evaluation
Hiroyasu OHTSU, Yutaka SAKAI and Yoshiki ONOI
Abstract:At the construction site of underground facilities, such as tunnel andcavern, geological investigations using borings and elastic waves are conducted to grasp geological conditions. It is practically impossible, however, to clarify uncertainties in geological conditions (hereinafter referred as geotechnical risks) of the whole construction site in the phase of feasibility study, F/S. Therefore, the construction cost, which is estimated based on geological data obtained in the phase of F/S, will overrun if the actual condition is worse than expected. This cost variation risk is interested by sponsors and lenders of the construction project, for it is closely connected with cash flow, which represents the project profitability. From such a viewpoint, this study aims to propose a project investment evaluation method considering variations of construction cost caused by geotechnical risks. In details, a geostatistical approach, such as indicator kriging, is utilized to calculate the variations of construction cost. The cost variation risk is represented by the risk curve, which is widely used theory in the field of financial engineering. Moreover, project financial analysis is carried out by using investment evaluation indices, such as Project IRR, Equity IRR, and DSCR, which are useful for sponsors and lenders. These values are calculated in the model of dynamic cash flow with construction cost variations caused by geotechnical risks. Key Words:Construction cost, Indicator kriging, Risk curve, Cash flow model, Investment evaluation