Research and comparison of delivery models at the Gemeinschafts Kraftwerk Inn

Abstract

Traditional project delivery models and the use of unit price or lump-sum contracts are regularly associated with cost and schedule overruns on major projects. Innovative delivery models offer an alternative. However, proving their effectiveness is difficult due to the small number of projects and lack of comparability. This article presents a study comparing an innovative delivery model with a traditional delivery model. Both models were used in the same project for the same structure: the 21.5 km long headrace tunnel of a hydroelectric power plant located at river Inn. The tunnelling was conducted using two double-shield tunnel boring machines in counter-heading mode. The construction commenced under a traditional unit price contract (UPC). This contract was cancelled by mutual agreement after a total of 3.5 km of tunnelling. To continue the drive with a new construction company using the existing site logistics, the innovative TIWAG alliance contract (AC) model was chosen for the first time in Austria. By means of probabilistic analysis and modelling of each complete drive in each model a comparative study was performed. For a complete tunnel drive in the alliance model, the modelling results indicate an expected reduction in construction time of 15 to 22 %.