Hornsby Quarry

Ron Bush, Former Development Manager, CSR Construction Materials

Hornsby Quarry was operated by CSR Construction Materials (formerly Readymix) from 1959 to 2003. The quarry commenced operation in 1905 and was operated by Hornsby Shire Council during the 1920s. It operated under the existing use rights provisions of the Environmental Planning & Assessment Act 1979.

CSR owned the two properties covering the quarry by freehold title. These are the Jones property of 28.45 ha and the Howes property of 7.689 ha. Both were part of an original land grant to Thomas Edward Higgins of 250 acres during February 1836. Both are zoned ‘Open Space A (Public Recreation— Local)’ under Hornsby Local Environmental Plan 1994. The Higgins family cemetery is located within the south-eastern corner of the Jones property, the graves dating from about 1875.

The quarry is located wholly within the Hornsby diatreme, which is a large oval-shaped structure with dimensions of about 1.5 km in the north-east — south-west direction and 500 m in the north-west— south-east direction. It exhibits distinctive bedding within the eastern face of the quarry owing to subsidence when the diatreme was formed. It is extensively jointed with well-developed faulting and shear zones within the quarry. Some wedge-shaped failures have occurred within the northern face during past quarry operations, and these have been removed and stabilised through extensive rock bolting.

Hornsby Quarry
The eastern face of the quarry which provides an outstanding cross section of a diatreme. This portion of the quarry is included on the Natural Heritage Listing. Compared the photograph with the diagram on the right showing the development of diatremes in the Sydney region.

Cross section of extinct diatreme volcano

Rock reserves remaining within the northern and western faces of the quarry were estimated in 1993 at 2.8 million tonnes, and if extraction had proceeded in accordance with the 1993 Development Plan, about 2.5 million tonnes would have been extracted over the years to 2020 at an average extraction rate of 110 000 tonnes per year.

The quarry is 120 m deep at the southern face. In 1997 it was being operated on a periodical basis for several weeks every two three months. During these production periods, material was extracted from the quarry and hauled to the plant for crushing and screening. The material was then stockpiled for sale until the next production period. The rock was  processed into road base and aggregate products for sale to local markets.

The eastern face of the quarry has exposed a vertical cross-section of the volcanic diatreme and subsidence bedding. The face is of geological and scientific interest owing to this exposure.

Although the quarry had reserves sufficient to last until 2020, the development of the Old Mans Valley Master Plan prompted CSR to consider possible end uses and restoration strategies. These included securing the site and leaving the quarried area as a void, filling the void to various levels, and rehabilitating the final level and using it for a range of community, recreational and open space uses. A filling restoration strategy was seen as a way to considerably shorten the life of operations on the site and to dedicate the restored void for community uses under the current site zoning.

Side of Hornsby Quarry

Major Council Acquisition of Quarry Site

After negotiations broke down between CSR and Hornsby Shire Council to use the quarry to receive clean fill from the Chatswood to Epping rail tunnels, the company requested Council to purchase the site as required under the zoning provisions. Ownership passed to Council in 2003 after a price of $26 million was established through the Land and Environment Court.

Council employed consultants in 2004 to investigate the site and develop a Master Plan for its future use. Constraints on future use include the heritage listing of the quarry, significant vegetation species on the site, drainage and the stability of large areas surrounding the pit