ABSTRACT
A feasibility study has recently been completed for the Chaglla underground hydroelectric project located in rugged Cordilleran terrain in central Peru. This chapter presents a case history of the feasibility level design process for the underground excavations and proposed support which was carried out under extremely difficult conditions. The regional and site geological interpretations were evolving during most of the feasibility study, so the rock mechanics work was effectively being carried out in parallel with the geological review. The different interpretations for alternative tunnel alignments were advanced simultaneously, and new surface mapping data and drillhole data were incorporated when available. Parametric sensitivity analyses allowed the design team to evaluate which components of the data collection program were most sensitive, and therefore which areas of data collection required most careful review. The Chaglla underground hydoelectric project was found to be technically and economically feasible.
