Ohau A power project: Pukaki canal, geology of section 200m-1500m

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Read, S.A.L. 1974 Ohau A power project: Pukaki canal, geology of section 200m-1500m. Lower Hutt: New Zealand Geological Survey. New Zealand Geological Survey report EG 186 11 p.

Abstract: Work has commenced on the excavation of material from the Pukaki canal line between the canal inlet and the S.H.8 overbridge at meterage 1900 approximately (fig. 1). This report outlines the geology of the first 1300 meters of the canal and makes brief mention of the materials present in relation to M.W.D. specification H.D.998 for constructing the canal. Data for the report is obtained from the geological logging of exposures in two principal areas, 1) The canal inlet structure area, 2) Cuts and excavations downstream from meterage 1100 approximately. Geological logs of the two main exposures are included in the report (fig. 2). Although little or no geological information is available from the are between the two logged areas, the information from the logged areas gives a good indication of what will lie between them. One calweld shaft, one dozer cut, and two percussion boreholes (locations in fig. 3) were put in by M.W.D. but none of these have been logged by N.Z.G.S. A geological cross-section delineating the boundaries between the major geological units is given as part of the report (fig. 3) The canal for most of the length covered by this report cuts through moranic topography created by the deposition of till during the advance of the Mt John ice. Although most of the excavation will be in the Mt John Till a large portion of the canal batters will be in the Mt John Outwash Gravel which underlies the Till Member. Fluvioglacial material forms thin deposits over the Mt John Till and Mt John Outwash Gravel. (auth)