In response to a verbal request by Mr R Good, Designing Engineer, Engineering and Water Supply Department, geological investigations were carried out to locate and determine the strike and dip of a possibly permeable metasandstone layer, which was exposed during excavation for the core trench at the base of the right abutment (Figure 1). This layer occurred beneath the valley floor alluvium and was not uncovered during site investigations. On the 8th October 1971 an inspection of the site was made and the walls of a pit excavated in the core trench were logged.