Solid-waste management facilities such as landfills can affect the
quality of underlying groundwater and surface water. Modern engineering
standards for landfills have reduced this potential in recent years,
but there are many solid-waste facilities still in operation that were
designed to less stringent standards.
Assessment of the extent and nature of landfill impact on groundwater
quality is a specialised field of environmental practice. C. M. Jewell
& Associates Pty Ltd (CMJA) has a strong background in this field.
Our experience with landfills has ranged in scale from desktop analysis
through to geophysical surveys, drilling investigations with hydraulic
testing, hydrochemical/contaminant characterisation of groundwater,
long-term monitoring design, containment system design and remediation
Some of our more interesting projects in this field are described below.
Contamination assessment, Homebush Bay / Newington, Sydney,
This major investigation of the Sydney Olympic site was commissioned
by the Department of Defence and NSW Property Services Group.
It required us to assess the progress of stabilisation in a number
of former landfills, and to finalise the risk assessment and remediation
strategy. CMJA provided specialist hydrogeological input and project
management services as a member of a multi-disciplinary consortium
including CH2M HILL ICF/Axis, GHD and Douglas Partners.
We also modelled the inflow to a leachate collection drain, which
was to be constructed as part of remediation work on the former
landfills at Homebush Bay. This work was completed for Thiess
Groundwater contamination risk assessment, Yarrowlumla Landfill,
This preliminary investigation was restricted to a desktop assessment,
involving hydrogeological assessment, identification of groundwater
users, identification of potential off-site movement of contaminants,
and preparation of a program for follow-up investigations. We
assessed the fate of contaminants from the landfill leachate,
estimated the potential risk to surrounding groundwater users,
and examined the compliance of on-site operations with the management
guidelines applicable to landfills.
Hydrogeological investigation, Ophir Road Landfill, Orange,
central west NSW
The objectives of this investigation, commissioned by Terra Sciences,
were to compile a detailed characterisation of site hydrogeology
and to identify any off-site movement of leachate-affected groundwater.
Mapping of localised hydrogeological features was complemented
by the drilling and construction of five monitoring bores. We
could then define the profile of the water table within fractured
basement rocks, and estimate permeability. Groundwater sampling
and analysis demonstrated that down-gradient groundwater on the
landfill margins had elevated concentrations of nutrients and
hydrocarbon contaminants, and high salinity. It was assessed that
groundwater beneath the landfill ultimately discharged to the
nearby creek. These hydrogeological findings were used in the
development of engineering design recommendations for the existing
and proposed landfill extension areas.
Hydrogeological investigation for proposed landfill extension,
The investigation, commissioned by Terra Sciences, involved the
drilling and completion of three monitoring bores across the proposed
landfill extension area. In addition, hydraulic conductivity was
measured using slug-test methods, and groundwater sampling and
analysis were undertaken. We could then define of the geological
profile, depth to groundwater, hydraulic gradient, hydraulic conductivity
of aquifer materials and groundwater chemistry and quality. CMJA
concluded that the risk of contamination of usable groundwater
arising from construction of the proposed landfill would be very
low. These findings were used to support an Environmental Impact
Statement, which accompanied a development application for the
proposed landfill extension.
Hydrogeological investigation for proposed new landfill, Coonamble,
This investigation, commissioned by the Coonamble Shire Council,
involved the review of existing regional geological and hydrogeological
data, in addition to site-specific information gathered during
the drilling and completion of three monitoring wells, testing
of soil engineering characteristics, assessment of aquifer hydraulic
conductivity and gradient, and groundwater sampling and analysis.
The assessment concluded that the risk of contamination of usable
groundwater arising from construction of the proposed landfill
would be very low. These findings were used to support an Environmental
Impact Statement to accompany a development application for the
proposed new landfill.
Landfill Gas Investigation, Dubbo, NSW
To address Dubbo City Council's concerns regarding the potential
risk of off-site migration of landfill gas into adjacent lands,
CMJA installed a soil gas collection system at six locations.
After a stabilisation period, soil gas was extracted from each
of the system's monitoring points and passed through a landfill
gas analyser to record concentrations of carbon dioxide, methane
and oxygen. The study concluded that the toxicity hazard and potential
for explosion due to the low methane concentrations detected would
be very low.
Unanderra Landfill, south coast, NSW
CMJA has also provided expert opinion (as a court-appointed expert)
for Supreme Court proceedings relating to the Unanderra Landfill.
This involved an assessment of geological and hydrogeological
conditions across the site, based on information collected by
other consulting firms, including borehole and well completion
logs, geophysical data, groundwater analysis results and other
relevant hydrogeological data.
Specialist Equipment And Methods
CMJA is fully equipped for the field assessment of landfill hydrogeology.
Our equipment includes:
Grundfos MP1 variable-speed, electro-submersible sampling
pump, suitable for use in purging standard 50-millimetre diameter
Hydrolab H2OG down-hole hydrochemical probe.
Soil vapour probes.
Electrical conductivity, pH, DO and redox meters.
Specialist sampling pumps and bailers.
Hydraulic conductivity (slug-testing) equipment.
In addition, where applicable, CMJA uses the following groundwater
Electromagnetic (TEM) sounding.
Electromagnetic (FEM) ground conductivity surveys.
DC resistivity soundings and traversing.
Down-hole geophysics (gamma, neutron, caliper, EM
CMJA can also offer groundwater flow and contaminant transport modelling,
How CMJA can help you
We have considerable depth of expertise and capability to deal with
all facets of hydrogeology related to landfill investigations. Whether
it be assessing the risks of leachate migration, assessing the suitability
of a site earmarked for a proposed new landfill facility, or installing
groundwater monitoring systems for existing landfill operations, CMJA
has the experience, knowledge and technology to help you.
Each project is tailored specifically to the requirements and goals
of the client, and also takes into account the need to provide supporting
information to regulatory authorities or operational planners.
CMJA also offers a full-service consultancy in hydrogeology, which
extends from water sampling to expert testimony.