Read, S.A.L. 1974 Tekapo B power project, Tekapo canal: Maryburn crossing, report no. 4. Lower Hutt: New Zealand Geological Survey. New Zealand Geological Survey report EG 205 5 p.
Abstract: Three previous geological reports have been written on the Maryburn crossing (Mansergh, 1972 a, 1972 b, and 1973) and a resistivity survey conducted (Mac Donald, 1972). Mansergh was not able to establish a reliable model of the geology under the valley containing the present Maryburn. The difficulties stemmed from the interrupted existence of an alluvium in percussion borehole BH178 upstream of the canal crossing (location of fig. 1). Despite extensive drilling, no trace of this alluvium was found under the canal centre-line where it crosses the Maryburn Valley. During the stripping of the Maryburn Valley prior to placing of the fill further investigations have revealed a more reliable model of the geology. These included an additional dozer cut (DC95) and a groundwater interceptor trench (locations on Fig. 1). This report outlines the present modelof the geology and discusses the engineering significance of some of the findings of the further investigations. The valley postulated from BH 178 did exist but it is interpreted to have been ''backfilled'' by a large ''fossil'' lakeside. Subvertical cracking generated by the landslide movement is visible in part of the canal foundations. Three figures are attached to this report:- a topographic map showing the layout of investigations (Fig. 1); a geological cross-section (Fig. 2) and geological logs of the dozer cut and interceptor trench (Fig. 3). (auth)
