Hancox, G.T. 1973 Report on preliminary geological investigations for the proposed Rangipo underground powerhouse. Turangi: New Zealand Geological Survey. New Zealand Geological Survey report EG 168 33 p.
Abstract: This report outlines the results of preliminary geological investigations at the site of the proposed Rangipo underground powerhouse. The topographic and geological setting of the site is described. Site investigations to date have included detailed surface mapping, an extensive diamond drilling programme and an exploratory drive. Results of these investigations are presented and the geological structure and rock defects revealed during preliminary investigations are discussed with reference to the suitability of the location and orientation od the powerhouse complex. Investigations completed so far seem to indicate that the rocks at the proposed site are the best kept in the immediate area. However, additional investigations are necessary, firstly, to confirm that an excavation of the size required can be safely and economically constructed in these rocks and secondly, to determine the orientation of the main excavation that is most likely to reduce problems from local failures along defects. Further investigations must provide detailed additional information on the extent of the main greywacke sandstone band that is considered suitable for the machine hall, and the location, nature and extent of the major zones of weakness (zone 1 and 2). These can best be determined from an exploratory shaft, drives,, diamond drill holes and a rock mechanics testing programme. (auth)