sydney-city-centre-review-of-environmental-factors

The proposal footprint is located above the Sydney basin-central area porous rock
aquifer unit. This is the most extensive of Sydney’s aquifer units; however its
associated groundwater quality is ‘poor-to-very-poor’ (State of the Catchment,
Groundwater the Sydney Metropolitan Region 2010, DECCW).
The proposal footprint is not located on land designated for groundwater
management or underlain by a vulnerable aquifer. It is also located outside of the
heavily contaminated Botany Bay sand beds.
The available published information on localised groundwater depth is limited to a
few bore records around Barangaroo and the periphery of the city centre. These
records confirm the presence of a water bearing zone at shallow depths of between
one and six metres. The wider literature also confirms that groundwater depths can
vary from just below the surface to approximately 10 metres 4 . Coastal inundation also
occurs east of the proposal footprint, often requiring dewatering during construction.
In conclusion, the geology and soil characteristics of the proposal footprint (refer to
section 6.8.2) are capable of bearing groundwater. They are also capable of being
hydraulically connected allowing groundwater to transfer between the geological
horizons and the upper soil layers (referred to as an unconfined groundwater). That
said, certain of the soils are characteristically impervious or semi-pervious (refer to
section 6.8.2) and would not readily support groundwater flow. They may however
support locally perched waters at or close to the surface or limited flows across their
extents. Closer to Sydney Harbour there is likely to be an interface between the
groundwater and coastal waters. As a result, the groundwater is likely to be slightly
brackish as a result of saline intrusion. The extent of saline intrusion and brackish
concentrations will depend on the localised groundwater pressure and chemistry
along with the geology of the area.
6.7.3 Potential impacts
Water quality and hydrology impacts during construction
Accidental spillage
Some of the proposed construction works detailed in section 3.3 would have a limited
risk of resulting in accidental chemical, oil and fuel spillages during construction. This
risk would exist:
At any work site as a result of general working activities
Along haulage routes through accidents or poorly maintained vehicles
At the construction compounds/laydown areas as a result of poor materials
handling, poor materials storage or poor equipment maintenance practices.
The corresponding activities within the proposal footprint that would be at greater risk
of accidental spillage include:
Removing spoil and waste from site to one of the construction compounds or
temporary laydown areas (ie haulage)
Delivering materials to site or one of the construction compounds or temporary
laydown areas (ie haulage)
Loading and unloading at the work sites and construction compounds or
laydown areas
Major ground excavation work, including drainage modifications and utility
adjustments.
4
Russell. G, Green. R, Rumpf. C, Managing Groundwater Impacts of Construction in Sydney NSW,
2010.
Sydney City Centre Capacity Improvement 368
Review of Environmental Factors