A quantitative evaluation of the sustainability or unsustainability of three tunnelling projects

• Evaluates sustainability of three tunnelling projects.
• Applies mathematical model to EIA of projects in construction and operation phases.
• All projects were evaluated as conducive with strong sustainability or better.
• Tunnelling offers significant benefits as a means of achieving sustainability.
• Underground space, in general, may be critical in combating environmental change.

There is a perception that tunnelling is sustainable. This is because it occurs underground, and consequently does not significantly interfere with surface or atmospheric processes unlike other anthropogenic activities. However, the tools and assessments used in tunnelling projects to evaluate sustainability in the construction and operational phases are primarily concerned with the reduction of carbon footprint and environmental performance. This does not provide a suitable approach to determining the sustainability of a tunnelling project directly. Environmental Impact Assessment (EIA) on the other hand does have this potential. However, it requires two things: (1) a suitable quantitative-based method of EIA; and most critically and (2) a means to evaluate sustainability from the EIA results. Based upon the recent work of Namin et al. (2014) concerning a new EIA methodology for tunnelling projects, this paper applies an established mathematical model of sustainability to the results of the EIA to determine the sustainability or unsustainability of tunnelling projects. The model’s application, in the form of an algorithm, evaluates three case studies assessed by Namin et al. (2014). The results are analysed and discussed in respect to the three projects’ construction and operation phases. The broader context of the results is then discussed in respect to the use of underground space as a means to achieve sustainability.