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

6.7 Water quality and hydrology
This section assesses the proposal’s potential impact on surface and groundwater,
drainage and flooding.
6.7.1 Method
Study area
The water quality and hydrology study area considered the Sydney Harbour
Catchment and underlying Botany Bay Sands aquifer.
Method and assessment criteria
The water quality and hydrology assessment referred to the following guidance and
policy:
Code of Practice for Water Management: Roads and Development
Management (Roads and Maritime, 1999)
Guidelines for Construction Water Quality Monitoring (Roads and Maritime,
undated)
Water Policy (Roads and Maritime, undated).
The assessment:
Identified and described the surface and ground water characteristics of the
study area
Confirmed the current drainage arrangements and discharge pathways across
the city centre road network focussing on the proposal footprint
Confirmed the flood risk potential across the proposal footprint
Identified key activities that could potentially affect surface or groundwater
values
Identified those adverse impacts that would need safeguarding or managing
under the proposal.
The impact assessment considered the ability for various construction activities to
impact on water quality and hydrological values either directly or indirectly though
migration pathways. Consequently, the assessment considered the value that the
surface and groundwater provides, and any change to these values as a
consequence of the proposal including the potential flood risk. Exposure,
contamination, migration, flood risk and change in function/quality were aspects
referred to in undertaking the assessment.
6.7.2 Existing environment
Catchment values
The proposal footprint is located within the Sydney Harbour Catchment. The
catchment is formed of an urban environment, 90 per cent of which is impervious
(eg roads, pavements, roofs, hardstand areas). Generally stormwater runoff is
captured by Sydney Water’s trunk drainage system and is discharged to Sydney
Harbour unattenuated. This includes the existing road drainage from within the
proposal footprint. The only pollution prevention controls in place are gross pollutant
traps. As a consequence, Sydney Harbour’s water quality is graded ‘poor’ as the
result of ongoing gross pollutant (litter), sediment, suspended solid, nutrient, organic
material, heavy metal and hydrocarbons discharges (Sydney Harbour Catchment
Water Quality Improvement Plan, Sydney Metropolitan Catchment Management
Authority, 2010).
Sydney City Centre Capacity Improvement 365
Review of Environmental Factors