WATER FROM THE ROCK - PERISHER VALLEY 1974

The geotechnical consulting engineering firm of Golder Moss Pty Ltd was retained in 1974 by Publishers Holdings Pty Ltd, the operators of the Perisher Valley Hotels and ski lifts, to investigate the feasibility of obtaining about 450,000 litres of ground water per day from waterbores in the Perisher Valley, as a possible alternative to piping water about 5km from the valley of Betts Creek located to the south-west of Perisher Valley. Warren Peck, suggested that ground water in usable quantities would be located in fractures in the granite bedrock and possibly also in the soil cover overlying the fractures. This water has soaked into the ground from snow melt and rain. It accumulates in the pores of the soil and in the natural fissures in the granite.

If a waterbore is located in linear major rock fractures called lineaments, it can often tap into significant amounts of water. Such features are more easily seen on aerial photographs, than during a ground survey. The sites of several lineaments were confirmed by seismic surveys in February 1974. Bores were drilled in March 1974 to test how much water could be obtained from the soil and fractured rock along two prominent lineaments in the Perisher Valley.

The Rock Creek Valley Lineament south-west of Perisher Village yielded about 50,000 litres per day from a group of 18 shallow bores (less than 7m deep) entirely located in the soil profile, whose permeability was found to be quite variable due to the presence of large pockets of impermeable clay. More promising results were obtained from Pretty Valley where a flow of 50,000 litres per day was obtained from pumping water from the bottom 4m of just one 12m deep bore. It had been drilled through about two metres soil thickness to encounter weathered granite underlain by the fractured fresh granite of one of the lineaments. It was inferred that the water yield from this bore could have been increased by simply drilling the bore deeper into the lineament.

The investigation concluded that the granitic soil was a poor water-producing medium but the fractured granite was likely to produce the required amount of water if pumps were installed in three or four bores, each drilled 20m to 30m into the fresh, fractured granite rock along one or two of the lineaments. The Perisher management decided to pipe the water in from Betts Creek, rather than drill the necessary waterbores into the fractured rock that underlies parts of Perisher Valley, from which supplies of drinking water could be pumped.