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Background
In Sydney's Northern Beaches region there are numerous
sporting fields in need of alternative water supply sources
for irrigation, and Warringah Council sought an assessment
of the groundwater resources at five of these sites. Some
sites contain fill material, including potentially hazardous
waste material. The dune aquifers are prone to seawater
encroachment.
C. M. Jewell & Associates Pty Ltd was commissioned
to assess suitable borehole locations, and to assess groundwater
quality issues.
Hydrogeological Environment
The five sites lie within the Sydney Basin, with two main
aquifer types: Quaternary sediment aquifers and deeper,
Triassic sedimentary rock aquifers. The Quaternary sedimentation
pattern is strongly influenced by sea-level changes, and
occurs in three depositional environments: marine tidal
deltas, mud basins, and channels. In the Northern Beaches
area, Quaternary aquifers form in unconsolidated sediments
in the Narrabeen Lagoon and along crescent-shaped beaches.
They provide numerous sources of water supplies, with yields
generally of the order of 1 litre per second (L/s).
Objectives and Scope
The assessment considered the following aspects:
- the most suitable locations for groundwater boreholes,
having regard potentially higher yielding aquifer zones
and surrounding groundwater users;
- potential contamination sources;
- other potential impacts such as seawater encroachment
and acid sulphate soil risks; and
- recommendations for further work, including monitoring
programs and aquifer testing.
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Projects
