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Highlights
- Major Municipal Solid Waste (MSW) Landfill
- Initial review of EIS and existing data
- Full hydrogeological study
- Representation at Planning Inquiry
Background
The Lucas Heights Regional Waste Depot is a major MSW
landfill which receives waste from much of the Sydney metropolitan
area. It was originally developed by the NSW Waste Management
Authority (WMA) in 1987; no hydrogeological investigation
was carried out at that time. In 1991 the WMA submitted
an Environmental Impact Statement for a proposal to expand
the depot both laterally and vertically (by overtopping).
C. M. Jewell was asked by the NSW Department of Planning
to review the EIS and prepare a report on the hydrogeological
aspects of the proposal; this report highlighted the lack
of hydrogeological data concerning the site and identified
a number of potential problems; it was submitted as evidence
to the inquiry. Subsequently the Waste Recycling and Processing
Service (WRAPS), the successor to the WMA, commissioned
Coffey Partners and D. J. Douglas and Partners to carry
out a hydrogeological investigation of the site. Coffey
appointed C. M. Jewell initially as project manager, and
subsequently as an external consultant on the project.
Hydrogeological Environment
The site is underlain by Hawkesbury Sandstone, which in
this area forms the Woronora Plateau, which slopes gently
to the north and is deeply dissected by a series of watercourses.
These watercourses drain recreational and residential areas
to the Georges River, a tidal estuary containing valuable
shellfish beds. The Hawkesbury Sandstone has very low intergranular
permeability, so that groundwater transmission occurs almost
entirely by means of fractures, which may be associated
with low-angle bedding planes or predominantly high-angle
joints, and may be localised in discrete zones associated
with geomorphological features, and controlled by the area's
tectonic history.
Objectives and Scope
The investigation included geological mapping, an extensive
drilling program, hydraulic testing, seismic refraction
and surface-to-downhole seismic surveys, and a program of
hydrochemical sampling and analysis. It was concluded from
the results of this work that part of the site was underlain
by a moderately transmissive and laterally extensive fracture
system. Consequently it was recommended that engineering
controls be implemented to limit migration of contaminants
from the site. A review of available engineering options
was carried out, and preliminary designs prepared for a
leachate collection system and clay-based lining system.
A joint report setting out the conclusions of the investigation,
and the recommended engineering approach, was prepared.
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Projects
