ACKNOWLEDGMENTS

Investigation of projects of the magnitude of the Snowy Mountains scheme requires the co-operation of many workers and skills. The investigation of the specialized problems associated with T. 1 power station described in this paper was carried out mainly by the Engineering Laboratories of the Snowy Mountains Hydro-Electric Authority under the general direction of T. D. J. Leech.

The author gratefully acknowledges helpful discussion and active assistance from Mr. K. R. Sharp, who carried out much of the geological field work and was resident geologist during most of the construction period, from Mr. D. Svenson, resident geologist during the later part of construction, from Dr. Lafeber, who made the petrographic analyses and some of the rock-bolt model studies, and from Mr. A. Molnar who made the drawings; Mr. A. D Hosking carried out other rock-bolt experiments, Mr. D. C. Herbert the determination of strength and elastic properties, Mr L. G. Alexander the flat-jack tests, and Mr. G. Worotnicki the photoelastic analyses. The triaxial tests were kindly made by Prof. J. C. Jaeger, Australian National University. The author also acknowledges stimulating discussions with Mr Roger Rhodes and Prof. E. A. Rudd during their many visits to the site as consulting geologists. Particular acknowledgment is made of the continuing active encouragement and direct interest in these investigations by Mr. T. A. Lang, Associate Commissioner of the Authority.

The power station is being constructed by the joint venture contractors: Campagnie Industrielle de Travaux, Enterprise Fougerolle pour Travsix Publics, Societe Nationale de Travaux Publics, Etudes et Entreprises, L’Entrepriscs. The willing co-operation of the contractors facilitated the investigation during construction.

This paper is presented by kind permission of the Snowy Mountains Hydro-Electric Authority. The views expressed herein are those of the author and not necessarily of the Authority.

TOPOGRAPHY AND GEOLOGY OF THE REGION

The Snowy Mountains consists of several considerably dissected plateaus that lie at various elevations mainly between 4000 and 7000 feet above sea level and are bounded by fault or warp escarpments with a northerly or northeasterly trend. The rivers have their sources in broad open valleys, but downstream they soon pass into deep steep-walled youthful gorges.

The mountains are composed predominantly of granitic rock and slightly metamorphosed sedimentary rocks, ranging in age from Ordovician to Devonian. In the upper Tumut region there are several outliers on the plateau consisting of unconsolidated lacustrine and fluviatile sand, clay and lignite of Late Eocene or Early Olignocene and overlaying by basalts of similar age. The granitic rocks on the plateau and forming the valley walls are intensely but irregularly weathered, in many places to depths of 100-200 feet below the surface. Along the valley floors where usually the streams are actively downcutting, the rock is fresh or only slightly weathered in many places.

The topography of the Snowy Mountains is considered to have resulted from the uneven uparching of an Eocene or older penoplain at intervals during Tertiary time, accompanied by crustal warping and faulting and physiographic rejuvenation.

The Tumut River in the region of the power station occupies a steep V-shaped valley, 2500-2000 feet deep, entrenched in the western margin of the Kiandra Tableland, a dissected plateau whose surface lies at elevations of 5200-4200 feet above sea level.