Case Study: A Practical Assessment of Geological and Hydrogeological Risk for Efficient Highway Underpass Design

The A57 upgrade is a project of national importance, designed to relieve congestion in the village of Mottram in Longdendale caused by traffic crossing the Pennines from Manchester. The project involves bypassing the village with a dual carriageway to reduce congestion. The largest structure in the scheme is the Mottram Underpass, a 130m long 10m deep underpass which is to be constructed in complex geotechnical and hydrogeological conditions comprising a geological fault and artesian groundwater. The underpass is adjacent to a large rock cutting. Detailed investigation has been undertaken to characterize these complicated ground conditions and a significant level of modelling has been undertaken to design this structure efficiently whilst managing the associated ground and groundwater risks.

Keywords: Carbon reduction, Project example, Geological fault, Hydrogeology.