Assessment of quartz in Sydney’s rock formations associated with recent engineering infrastructure projects; implications for workplace health and safety

Och, David J.1&2 and Cole, Kate3

1Adj. Assoc. Professor, University of New South Wales, Kensington,, 2Senior Principal Engineering Geoscientist, WSP Australia Pty Ltd, Sydney, NSW., 3A/Director Health & Occupational Hygiene, Sydney Metro, Sydney NSW 2000.

Sydney Metro is Australia’s largest public transport project. This new standalone railway will deliver 31 metro stations and more than 66 kilometres of new metro rail, revolutionising the way Australia’s biggest city travels. As part of the development of Sydney Metro, both historical and current ground data is being collected and compiled to better understand the proportion of quartz that will be encountered along the proposed tunnel alignments.

Tunnelling and excavation work being undertaken in quartz-containing rock creates a dust comprising of a very fine shard particulate due to the impact and grinding reduction of the tunnelling and excavation equipment (i.e. road header, rock breaker and Tunnel Boring Machine (TBM)). As the dominant hard-mineral component is quartz, at the point of excavation, fine particulates of respirable crystalline silica dust can be released which can be suspended into the atmosphere. These fine particulates can be suspended in the air column and may create an occupational health risk resulting in illness and disease such as silicosis and lung cancer.

Geotechnical investigations across Sydney Metro have targeted the Triassic Wianamatta Group, Mittagong Formation and Hawkesbury Sandstone of the Sydney Basin. Quartz was found to make up to 90% (avg. 72%) of the grains in Hawkesbury Sandstone with the other components being siderite and clays. The hard-mineral component in Hawkesbury Sandstone is dominantly quartz detritus with other mineral components being moderate to weak in strength and less susceptible to micro-fracturing due to the mineral’s crystal framework.

This paper will provide an overview of the predicted proportion of quartz along the Triassic Wianamatta Group, Mittagong Formation and Hawkesbury Sandstone formations in the Sydney Basin.


Assoc. Prof David Och is a Fellow of the Geological Society of Australia and a 2019 Winston Churchill Fellow working as a Senior Principal Engineering Geoscientist with WSP Australia.  David’s expertise is demonstrated by performing key roles on large infrastructure projects including Sydney Metro City & Southwest, Sydney Metro West.

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