Assessment and management of groundwater
Groundwater is a vital resource. Its importance continues to increase,
as available surface water resources become fully utilised, and environmental
pressures restrain the development of large surface impoundments. In many
arid areas groundwater is, and will remain, the only viable source of
Groundwater is also a fragile resource. Water currently stored in aquifers
may have been recharged hundreds or even thousands of years ago, and
flow rates through the subsurface may be very slow. Damage caused by
poorly planned exploitation or by chemical pollution may be difficult
or impossible to remedy.
Hydrogeology is the science of water movement through soils and rocks.
Practical application of hydrogeology requires a thorough understanding
of the natural processes of groundwater recharge, flow, and chemical
evolution, and it also requires a good knowledge of the technologies
available for groundwater evaluation, exploitation and protection.
C. M. Jewell & Associates Pty Ltd (CMJA) draws on 30 years of international
and Australian experience solving groundwater-related problems. Our
expertise spans the full range of services required to locate, evaluate,
monitor, develop and protect groundwater. The services we can provide
include the following.
Location of groundwater supplies using geomorphological, geological,
photo-geological and geophysical techniques
Groundwater resource evaluation using well and aquifer
testing, and hydrogeochemical techniques
Groundwater development using boreholes, spearpoints,
dug wells and infiltration galleries
Groundwater quality monitoring
Groundwater contamination assessment and remediation
Mine water management
Investigation and management of dryland salinity problems
Design and management of the groundwater aspects of
solid and liquid waste disposal, including landfill, wastewater disposal
by irrigation or infiltration, and wastewater reinjection.
Hydrogeology is a specialised field with applicability to a wide range
of engineering, environmental and agricultural problems. Several interesting
examples of CMJA's experience in hydrogeological investigations are
Examples of CMJA's expertise
Solid waste-management facilities such as landfills can affect
the quality of underlying groundwater resources. It is therefore
vital to get the best possible advice.
Our hydrogeologists have considerable depth of expertise and project
experience. We can assess the suitability of a site for a proposed
new landfill development, and predict potential impacts. We can
also manage installation, monitoring and investigation for contaminants
at existing landfill operations. Described below is a hydrogeological
investigation - conducted by CMJA - for the Whylandra Landfill
in Dubbo, Central West NSW.
The Whylandra Landfill has been in operation since 1977. We evaluated
existing information on the hydrogeology of the surrounding area;
this indicated that Mesozoic-age sandstone lithologies underlie
the entire landfill area, and constitute the only zone available
for groundwater movement. A number of deep piezometers were drilled
through deeply weathered sedimentary rocks, and the zone of saturation
(water table) located at over 40 metres depth.
Our overall assessment of climate, hydrogeology and waste containment
practices indicated that there was little risk of significant
groundwater contamination resulting from leachate movement. We
completed our investigations with landfill gas testing, which
again showed little cause for concern.
Effluent irrigation of land
Increasingly, water authorities are recognising the benefits of
properly managed effluent irrigation systems, and so hydrogeologists
are often called upon to help mitigate the effects of effluent
discharge on groundwater resources.
CMJA's hydrogeologists have a strong background and field experience
in hydrogeological investigations of this type. Our work has covered
a wide variety of industries including feedlots, sewage discharges,
milk processing facilities, dewatering re-injection and landfill
The innovative free-stall dairy operated by Moxey Farms at Gooloogong,
NSW, is one example of a project assisted by an effluent irrigation
investigation carried out by CMJA. An outline is provided below.
Proposals to expand dairy effluent irrigation at Moxey Farms
were assessed in relation to their potential impact on groundwater.
The farm is underlain by an alluvial sequence that hosts a multi-layer
aquifer system. The groundwater quality of this aquifer system
was potentially vulnerable, following the use of dairy effluent
to irrigate areas used for pasture and fodder production.
Investigative work comprised extensive electromagnetic surveys
to locate higher permeability sand lenses, DC resistivity soundings
to enhance depth resolution, backhoe test pit examination, soil
permeability testing, drilling of boreholes into the unconfined
aquifers and delineation of pre-irrigation groundwater quality.
CMJA's investigations identified those pasture areas with greater
sensitivity to contamination from effluent irrigation. We also
designed and implemented a programme to monitor shallow groundwater
CMJA has conducted a wide range of investigations for the mining
industry. These include locating suitable groundwater resources
to support mining operations, conducting impact assessments of
mining/quarrying operations on neighbouring groundwater resources,
and designing and installing groundwater monitoring programs.
When it is proposed to mine below the water table, assessments
must take into account all impacts resulting from dewatering and
aquifer depressurisation. Similarly, the potential impacts of
open-cut or underground mines on natural surface water and groundwater
flow systems must be assessed.
Risk-based assessments regarding the potential for aquifer contamination,
or the identification of contaminant migration pathways, may also
be requested. Regulatory authorities will often require such work
before considering an application to develop and/or expand a mining
CMJA has conducted numerous mining impact assessments. Our clients
have included Peak Hill Gold (Peak Hill Gold Mine), Tailings Treatment
(Tomingley), Enhance Place Pty Ltd (Enhance Place Colliery near
Lithgow, NSW), David Mitchell Pty Ltd (Sulcor Limestone Mine and
Attunga Limestone Quarry, both near Tamworth), Concrite Quarries
Pty Ltd (Exeter Basalt Extraction Area, Southern Tablelands, NSW),
ACI Industrial Minerals (silica sand mining at Tanilba Northern
Dune, Port Stephens, NSW), Rocla Quarry Products (Calga, Central
Coast) and Kelian Equatorial Mining (East Kalimantan, Indonesia).
Groundwater modelling of flow and solute transport
Groundwater professionals are frequently challenged to make predictive
quantifications of groundwater behaviour. They may need to assess
how much groundwater is present, by using flow modelling; or they
may be required to predict the concentration of solutes contained
within flowing groundwater, by using contaminant transport modelling.
Depending upon the objectives, models can vary from a simple
analytical equation embedded in a spreadsheet program through
to a highly complex time-variant numerical model designed to simulate
subtle changes in groundwater movement within a complicated geological
environment over a period of several decades.
We use several of the industry standard modelling codes and integrated
modelling software programs, including Visual MODFLOW, INTERSAT/INTERTRANS,
SEEP/W and SEEP 3D. Also available to us are supporting software
packages such as Visual Groundwater, Mapinfo and Surfer.
More important than the modelling packages are the users, however.
CMJA's hydrogeologists have the experience and insight to make
the critical choices in designing the model approach most appropriate
to the application.
One CMJA groundwater modelling project was that undertaken for
the Eastern Distributor Motorway, Sydney, NSW. The motorway link
from Woolloomooloo to Sydney Airport involves a tunnel through
sandstone and a 'parkway' excavated below the water table in the
Botany Sands aquifer. On behalf of the main contractor, Leighton,
CMJA carried out a suite of modelling studies, using analytical
and numerical finite element and finite difference techniques.
These were used to assess the regional and local impacts of both
the construction dewatering and the permanent structure, and to
optimise a dewatering system design and the implementation of
a re-injection system.
Other groundwater modelling assignments include the Parkes borefield
(water supply), Thredbo Landslide Inquiry (expert witness), and
Beemery cotton farm (irrigation).
Specialist equipment and methods
CMJA is fully equipped to undertake all hydrogeological investigations
and can employ a range of innovative investigative tools to help with
assessments. Our equipment includes:
Grundfos MP1 variable-speed, electro-submersible sampling
pump, suitable for use in purging standard 50-millimetre diameter
Hydrolab H20G down-hole hydrochemical probe;
soil vapour probes;
electrical conductivity, pH, DO and redox meters;
specialist sampling pumps and bailers; and
hydraulic conductivity (slug-testing) equipment.
In addition, where applicable, CMJA uses the following groundwater
electromagnetic (TEM) soundings;
electromagnetic (FEM) ground conductivity surveys;
DC resistivity soundings and traversing;
down-hole geophysics (gamma, neutron, caliper, EM
CMJA has the capability to deal with all facets of hydrogeology. Whether
you require us to locate suitable groundwater supplies to support a
mining or irrigation operation, to assess the impacts of proposed or
existing operations on underlying groundwater resources, or to design
and implement a groundwater monitoring program, we have the experience,
knowledge and technology to help you.
We tailor each project to your specific requirements and your project
goals, and also take into consideration 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.