Underground Construction - Hydrogeology: Objectives, Methods, Applications - page 284

This example highlights the importance of exploratory drilling as the
tunnel advances, in order to preventively locate contingent water-bearing
zones ahead of the tunnel path and to enable a preliminary emptying of
the reservoir in order to subsequently continue excavation.
The drying of the Ingram well is a reminder of the absolute necessity of
preemptively examining potential effects of the project on the surrounding
water catchments. In this case, the geometry of the paleo-valley could have
been determined through the creation of an isohypsal map of the roof of
the substratum based on an appropriate grid of survey points (geophysics
and boreholes).