Ohau A power project, geological report on canal lining from the Ram Paddock hill area, vol. I

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Read, S.A.L. 1974 Ohau A power project, geological report on canal lining from the Ram Paddock hill area, vol. I. Lower Hutt: New Zealand Geological Survey. New Zealand Geological Survey report EG 173 94 p.

Abstract: A trial section of the Pukaki Canal constructed close to Ram Paddock Hill in 1972 exposed a potential canal lining material called The Pre-Balmoral Outwash Gravel. This report describes the geology of the Ram Paddock Hill area and delineates the limits of the Pre-Balmoral Outwash Gravel. The Pre-Balmoral Outwash Gravel lies on the upthrows (western) side of the Ruataniwha Fault in the Ostler Fault Zone. Bedding in the Outwash dips at 20-26 degrees to the west and strikes subparallel to the fault trace. Ram Paddock Hill and nearby Boat Hill are inliers of Pre-Balmoral Outwash Gravel generally lying below a covering of Alluvial Gravel, the youngest geological unit present. Two aquifers are presented in the Ram Paddock Hill area. The upper one is within the Alluvial Gravel, and the lower one is within the Pre-Balmoral Outwash Gravel or younger geological units. Quantities at present indicate that a maximum of approximately 3.2 x 10 /sup6/ m/sup3/ of Pre-Balmoral Outwash Gravel are present. 1.8 x 10/sup6/ m/sup3/ of younger geological units must be removed to expose the Pre-Balmoral Outwash Gravel. However it is possible that there are undetected alluvial valleys cutting through the Pre-Balmoral Outwash Gravel. Further investigations must be done to confirm or deny the existence of these valleys as their presence would decrease the volume of Pre-Balmoral Outwash Gravel and increase the volume of Lower Alluvial Gravel overburden. More accurate soil mechanics testing must be done on the geological units younger than Pre-Balmoral Outwash Gravel before decisions on their constructional use is made. The Upper Alluvial Gravel can be processed to form filter/armour for the canals. (auth)