New South Wales Roads and Maritime Services (RMS) has released its environmental impact statement (EIS) for the Hornsby Quarry Road Construction Spoil Management project, which involves transporting excavated material from Sydney’s 9km NorthConnex motorway tunnelling project to the inactive Hornsby Quarry, located west of the Hornsby town centre.
RMS identified five other sites that might be a suitable destination for the spoil, including Gosford Quarry, a former CSR-owned quarry and the Great Southern Rock Quarry. However, Hornsby Quarry was identified as a preferred option given it was the closest location to the NorthConnex project site and would minimise the overall distances required for spoil transportation by around 3.7 million kilometres.
While earlier government communication indicated that about one million cubic metres (m3) of spoil would be used, RMS has now proposed in the EIS to transport up to 1.5 million m3. In total, the NorthConnex project is expected to generate around 2.6 million m3 of spoil.
The EIS also confirmed the spoil would be delivered to the quarry pit via a combination of truck transportation via the existing road network and an above-ground conveyor system, which would take spoil from a stockpile site in Old Mans Valley and deposit it directly into the quarry void.
Other transport options that were considered included trucking the spoil directly to the quarry void floor and delivery via an underground tunnel and conveyor system.
Filling the void
Hornsby Quarry was operated as a breccia hard rock quarry by private businesses from the early 1900s. Quarrying ceased in the late 1990s and in 2002, the site was acquired by Hornsby Shire Council from its final quarry operator, CSR.
The abandoned quarry’s more than 100m deep void is now flooded with about 11m of water. Subject to approval, Hornsby Shire Council would be required to dewater the quarry to a suitable level from December this year, with spoil haulage and stockpiling scheduled to begin in April 2016 for a period of approximately 28 months. The entire spoil management project is expected to reach completion by September 2018.
The material excavated from NorthConnex would be used to partially fill the quarry and raise its floor to a level that would allow for rehabilitation work to commence. Current plans for the quarry’s rehabilitation involve its redevelopment as recreational parklands, which could be open to the community by 2021.
The public consultation period for the spoil management project closes on 4 September, 2015.
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