Groundwater Contamination: Causes, Risks and Monitoring

Groundwater supplies around 30 percent of Australia’s consumptive water use and is the primary water source for many mining operations, agricultural regions and remote communities. In Western Australia alone, Perth relies on shallow, unconfined aquifers for about 40 percent of its drinking water supply. Contaminated groundwater can develop quietly over years or decades, then suddenly trigger project delays, compliance breaches or community health concerns. This article explains how groundwater contamination occurs, what the key risks are, and how robust groundwater monitoring – including automation – reduces those risks. Monitel is a Western Australian engineering firm that designs and delivers groundwater monitoring systems for mining, civil infrastructure and environmental projects, with a focus on producing accurate, defensible data.

What Is Groundwater Contamination?

Groundwater contamination occurs when chemicals, metals, nutrients, microbes or other pollutants enter an aquifer at concentrations above natural background levels, rendering the water unsafe for its intended use or harmful to ecosystems. It is important to distinguish between naturally elevated constituents – such as iron, manganese or salinity found in many WA aquifers – and pollution introduced by human activity. The presence of acid sulfate soils, for example, can lead to groundwater acidification and heavy metal leaching without any industrial input.

Contaminants move through the ground by infiltration from the surface, leakage from infrastructure, or migration along fractures and permeable strata. Depending on geology and hydraulic gradients, pollutants can travel hundreds of metres or more from their source. Contaminants can persist in groundwater for decades after the original pollution event, which makes early identification essential. Critically, contaminated groundwater usually looks clear – contamination is almost always discovered through groundwater quality monitoring rather than visual inspection.

Common Sources of Contaminated Groundwater in Mining, Infrastructure and Industry

Most contamination pathways relevant to Australian projects fall into a handful of categories. Many plumes originate from legacy activities dating back to the 1960s through the 1990s, but new projects can still create issues if appropriate controls and ongoing monitoring are not in place. The sections below outline the most common potential sources, with later sections linking these to specific monitoring strategies.

Mining Activities and Tailings Storage Facilities

Seepage from tailings storage facilities, waste rock dumps and process water ponds can mobilise sulphate, acidity, and dissolved metals – including arsenic, lead and nickel – into underlying aquifers. Acid and metalliferous drainage from sulphide-bearing waste is a well-documented risk at gold and base metal operations across WA. Dewatering and drawdown can change groundwater flow directions, potentially pulling historic contamination toward active bores or sensitive receptors.

Regulators frequently require continuous groundwater level monitoring and periodic water quality monitoring around tailings storage facilities and mine pits as conditions of environmental approval.

Industrial Facilities, Fuel Storage and Pipelines

Industrial activities can introduce heavy metals and organic contaminants into groundwater through historical releases of hydrocarbons, solvents, PFAS and other persistent substances. Common scenarios include leaks from underground storage tanks at service stations, pipeline failures along transport corridors, and spills near loading facilities at ports or depots. Light non-aqueous phase liquids tend to float on the water table while dense non-aqueous phase liquids sink, complicating both monitoring and remediation.

Historical industrial practices have contributed to ongoing groundwater contamination challenges at many Australian sites constructed before the 1990s, which lacked modern containment and leak detection. Groundwater contamination in Perth is a significant environmental concern because pollutants can easily leach into Perth’s groundwater due to sandy, porous soils. Monitoring for PFAS is now necessary due to their confirmed presence in contaminated groundwater across Perth and at defence facilities nationally.

Landfills, Waste Facilities and Legacy Disposal Pits

Leachate from landfill sites and historical waste disposal pits can contain ammonia, chloride, metals, organic compounds and emerging contaminants including PFAS. Studies at Fishermans Bend in Melbourne found total PFAS concentrations ranging from approximately 88 to 973 ng/L within landfill boundaries, with limited attenuation over three years – illustrating how persistent these substances are. Unlined municipal tips from the 1960s through the 1980s remain a common issue across regional Australia.

Leachate generation is influenced by rain, cover quality and landfill gas, making contamination risk susceptible to climate variability. Proper landfill management prevents groundwater contamination, and long-term monitoring networks positioned upgradient and downgradient of landfill facilities are standard regulatory expectations under state EPA guidelines.

Agriculture, Irrigation and Nutrient Loading

Intensive agriculture can lead to nitrate, phosphate, pesticide and salinity contamination through infiltration from irrigated fields, feedlots and chemical storage areas. Nutrient infiltration from fertilizers contributes to groundwater contamination in many shallow alluvial aquifers beneath horticulture districts. Over-applied fertilizers can lead to high concentrations of nitrogen and phosphorus in groundwater, and in unsewered areas, septic systems can introduce pathogens and nutrients into the aquifer.

Nutrient-rich groundwater can affect nearby creeks, wetlands or groundwater dependent ecosystems, even where groundwater is not used directly for irrigation or drinking. Sustainable land use practices minimise negative impacts on groundwater, and periodic water quality monitoring in farm bores or regional networks helps track trends and guide better groundwater management.

Accidental Spills and Short-Term Incidents

Single events – a chemical truck rollover, an acid spill at a processing plant, or a failure of a bunded storage area containing hazardous materials – can cause acute groundwater contamination if not contained. Urbanisation and land development also increase runoff and the risk of contamination reaching shallow aquifers. Rapid groundwater monitoring using temporary wells, field meters and automated sensors can help define the extent and direction of a spill-related plume. Many project approvals now require incident response plans that include groundwater monitoring and reporting obligations. Early mobilisation of monitoring instrumentation consistently reduces long-term remediation costs by informing targeted clean-up.

Key Risks of Undetected Groundwater Contamination

Undetected or poorly monitored contamination creates environmental, operational, financial and regulatory risks across the life of a project. For many WA mining and infrastructure operations, groundwater is a critical approval condition, so data gaps can halt work.

Environmental and Health Impacts

Groundwater contamination poses risks to local communities and ecosystems. Groundwater pollution affects distinct ecosystems such as wetlands and coastal areas, and groundwater-dependent ecosystems are particularly vulnerable to contamination and climate-related stresses. Where contaminated groundwater discharges into surface water systems, it can affect freshwater aquatic habitats and cultural values even when the aquifer itself is not directly used.

Drinking contaminated groundwater can cause diarrhoea and vomiting. Long-term exposure to contaminated water may increase cancer risk, and contaminated groundwater can lead to kidney or liver disease. Diseases like hepatitis may arise from septic tank waste contamination. Exposure pathways include ingestion, dermal contact and inhalation of vapours – particularly near volatile contaminants in confined spaces. These health effects underscore the need to protect human health through reliable monitoring of water resources.

Perth faces challenges in managing groundwater resources due to pollution and climate change, making the sustainable use of these resources a priority for communities that depend on them for drinking water supply.

Operational, Structural and Geotechnical Risks

Groundwater contamination can also signal geochemical or hydrogeological changes that affect infrastructure performance. Aggressive water with high sulphate or low pH can cause concrete corrosion, scaling or fouling of pumps. Unrecognised contamination can complicate dewatering, tunnel construction or deep excavations – for example, a cut-and-cover tunnel in contaminated fill or a pipeline trench dewatering into a hydrocarbon plume. Groundwater contamination can raise the costs of treatment and public expenditure significantly. Early detection through groundwater monitoring helps geotechnical and structural engineers adjust designs, materials and construction sequences to manage these risks before they escalate.

Regulatory, Legal and Reputation Risks

The Environment Protection Act 1986 mandates duties for contaminated land management, and groundwater contamination must be cleaned up or managed under regulations. In South Australia, activities impacting groundwater require an environmental authorisation. The Priority Sites Register (Victoria) identifies contaminated sites needing remediation, and enhanced regulation is essential for mitigating groundwater contamination across all jurisdictions.

Consequences of inadequate monitoring include non-compliance with licence conditions, improvement or clean-up notices, delays in approvals, and potential prosecution. Once a plume is formally identified, it may trigger restrictions such as groundwater prohibition areas or conditions on future land use. Regulating activities near water supply catchments is crucial for protecting groundwater quality, and public communication about groundwater safety and treatment is key to maintaining community trust. Defensible, audit-ready groundwater quality data is essential in any regulatory or legal scrutiny – poor data can be as problematic as no data.

Groundwater Monitoring Parameters for Detecting Contamination

Effective groundwater monitoring combines level measurements, quality monitoring and targeted laboratory analysis. Parameter selection depends on potential contaminants identified during conceptual site model development. Groundwater quality monitoring is essential for regulated activities to prevent pollution, and monitoring assesses impacts from regulated activities on water quality. Groundwater quality monitoring is also influenced by land-use activities and urbanisation.

Groundwater Level and Pressure

Continuous groundwater level monitoring defines flow directions, gradient changes and drawdown from pumping or dewatering. Typical instrumentation includes vibrating wire piezometers, submersible level transmitters and pressure transducers connected to data loggers. Stable, long-term level records help interpret contaminant plume movement and distinguish between seasonal variability and project-driven changes. Monitel designs automated groundwater level monitoring networks with barometric compensation and density corrections, recording data referenced to depth to water, metres above Australian Height Datum and well-documented monitoring well reference points.

Electrical Conductivity, Salinity and Temperature

Electrical conductivity is a useful screening parameter for dissolved salts and many types of contaminated groundwater, particularly near tailings facilities, landfill sites and coastal infrastructure. Continuous EC and temperature monitoring in bores can provide early warning of changes in groundwater quality before laboratory results are available. Step changes in EC may indicate the arrival of a plume, mixing of aquifers, or saline intrusion due to over-pumping. Monitel integrates EC and temperature sensors into automated systems for high-resolution datasets.

Core Water Quality Indicators (pH, DO, Turbidity and Redox)

Groundwater monitoring includes testing for pH, conductivity, and dissolved oxygen – along with oxidation-reduction potential and turbidity – to characterise the geochemical conditions that control contaminant mobility. Acidic groundwater may indicate acid and metalliferous drainage, while low dissolved oxygen and reducing conditions can favour mobilisation of iron, manganese or arsenic. Calibration, maintenance and correct field protocols are critical, as poor procedure easily distorts these indicators. Monitel prioritises data integrity by matching instrumentation to site chemistry and providing guidance on suitable deployment methods.

Contaminant-Specific Parameters (Metals, Nutrients, Hydrocarbons and Organics)

Many key contaminants – dissolved metals, PFAS, chlorinated solvents, petroleum hydrocarbons and pesticides – require periodic sampling and accredited laboratory analysis. Automated sensors and continuous logging provide context for these results by capturing short-term events and seasonal patterns that periodic sampling alone would miss. When potential contaminants and potential sources are well defined, targeted analyte lists reduce monitoring cost while still satisfying regulatory requirements. For example, a landfill might require quarterly sampling for metals and nutrients combined with continuous level and EC monitoring, while a site with a known hydrocarbon plume might need more frequent sampling after a spill event.

Designing a Groundwater Monitoring Program for Contamination Control

An effective monitoring program is an engineered system: network design, instrumentation, sampling protocol, data acquisition and reporting. It starts from a conceptual site model and regulatory obligations, then works backwards to select bore locations, depths, monitoring frequency and suitable methods. Monitel typically works alongside hydrogeologists and environmental consultants, supplying and integrating the monitoring instrumentation and automation components.

Site Characterisation and Baseline Groundwater Quality

Establishing baseline groundwater quality and levels before major construction or mining works is fundamental – ideally collecting at least 12 to 24 months of data where feasible. Baseline groundwater quality data sets are essential for pollution identification, allowing teams to distinguish project impacts from natural variability, legacy contamination or regional trends such as drought-related changes. Regulators in several Australian jurisdictions now explicitly require baseline datasets for new or expanded regulated activities. Typical tasks include drilling monitoring wells, logging geology, installing screened intervals in relevant aquifers and performing initial sampling to assess the range of background conditions. High-quality groundwater monitoring data is essential for effective environmental management from this point forward.

Monitoring Well Networks, Screens and Bore Construction

Network design follows established principles: upgradient and downgradient bores, nested wells at different depths, consideration of hydraulic gradients, and separation of shallow perched systems from deeper regional aquifers. Screen length, screen position and backfill materials matter because poorly designed completions can mix zones, short-circuit flow or introduce cross-contamination. Monitel often instruments existing monitoring wells or bores installed by drilling contractors, focusing on accurate measurement rather than bore construction. Maintaining thorough bore construction records – top of casing, casing type, screen intervals, well depth – is crucial for interpreting monitoring data over the long term and for any subsequent assessment of contamination.

Sampling Frequency, Event-Based Monitoring and Trigger Levels

Sampling frequency is determined by risk, groundwater travel times, regulatory requirements and operational decisions. Event-based monitoring during critical periods – commissioning of tailings facilities, major dewatering campaigns, spill responses – augments routine schedules. Trigger levels based on baseline data and guideline values prompt investigation or management action when exceeded. These measures support the implementation of responsive risk management rather than reactive clean-up. Regular groundwater quality monitoring validates pollution prevention measures and confirms the effectiveness of controls already in place. Automated telemetry and near-real-time dashboards make it straightforward to check conditions against trigger levels without waiting for manual readings, which is particularly valuable at remote sites where monitoring is undertaken less frequently.

Automated Groundwater Monitoring vs Manual Measurements

Manual groundwater level measurements and periodic sampling remain essential, but automation significantly improves data density and responsiveness. The optimal approach is usually a combination: continuous sensor data for levels and basic quality indicators, supplemented by scheduled and targeted sampling for full chemistry.

Benefits of Automated Groundwater Monitoring Systems

Automated monitoring can improve groundwater data collection and compliance tracking across all project phases. Practical benefits include reduced site visits – particularly important at remote or hazardous locations – higher monitoring frequency, improved safety, fewer missed events and faster detection of changes. Automated data loggers, telemetry and cloud reporting platforms provide near-real-time access to groundwater level and water quality data. Automated alarms via SMS or email alert teams when level, EC, pH or other parameters exceed predefined thresholds, enabling rapid response. These continuous, defensible records withstand regulatory and audit scrutiny far more reliably than periodic manual snapshots. Monitel’s systems are technology-agnostic, focused on data integrity, calibration traceability and robust operation in the Australian environment.

Where Manual Groundwater Monitoring Still Matters

Manual measurements remain critical for calibration checks, QA/QC, and contaminants that cannot yet be reliably measured in situ – including complex organics, some metals and PFAS. Best-practice manual methods include low-flow sampling, standing water level checks and cross-checks between field meters and laboratory results. Manual inspections also identify physical issues such as damaged casings, blocked screens or surface spills that sensors alone will not detect. Monitel designs monitoring systems to align with clients’ existing manual water quality monitoring programs, avoiding duplication and maintaining consistency. Manual monitoring is complementary to automated systems, not a competing approach.

Data Quality, Interpretation and Reporting

Groundwater monitoring is only as useful as the reliability of the data collected and the clarity of its interpretation. High-integrity datasets require correct sensor selection, installation, calibration, data management and QA/QC processes – all areas where managing the details determines whether data is defensible or not.

Ensuring Data Integrity and Traceability

Key aspects of data quality include sensor accuracy, regular calibration, barometric and temperature corrections, density corrections for salinity, and drift checks. Metadata – bore construction details, sensor serial numbers, installation depths, calibration records and field notes – must be maintained and easy to document. Automated systems should maintain audit trails of configuration changes, alarms and data edits, supporting transparent reporting to regulators. Poor-quality or incomplete data can lead to conservative assumptions in risk assessments, potentially increasing remediation obligations or delaying approvals. Establishing robust data protocols from the outset avoids these problems.

Turning Groundwater Monitoring Data into Action

Trend analysis, contouring, time-series plots and hydrogeological models turn raw data into actionable insights for engineers and environmental managers. For example, identifying an emerging salinity increase around a tailings facility, detecting drawdown impacts near a community bore, or confirming that a remediation system is capturing a plume. Regular reporting – monthly dashboards, quarterly or annual compliance reports – is typically required under environmental approvals. Monitel’s systems integrate with clients’ reporting workflows, making it straightforward to export data for consultants and regulators. Clear, timely reporting is central to demonstrating responsible groundwater management and contamination control, and to protecting the long term effects on water resources and surrounding land from going unaddressed.

Monitel’s Role in Proactive Groundwater Contamination Monitoring

Monitel supports clients in preventing, detecting and managing contaminated groundwater across the lifecycle of a project – from baseline assessment through operations and closure. As an engineering-led groundwater monitoring partner with direct experience in Western Australian mining and infrastructure conditions, Monitel focuses on producing accurate, defensible data rather than simply supplying hardware.

Typical services include instrumentation selection (piezometers, level transmitters, multi-parameter probes), system design, installation, telemetry integration, data acquisition, cloud dashboards and long-term support. Where remediation is already underway – whether through pump-and-treat systems or other methods – Monitel’s monitoring systems help assess and verify the effectiveness of treatment. For projects looking to maintain groundwater levels and dilute contaminants, technologies like Managed Aquifer Recharge can also be supported with reliable monitoring data.

Monitel’s groundwater monitoring instrumentation page provides further detail on sensors and systems, and the wells and bores monitoring services page covers bore-based monitoring solutions for a range of site conditions.

Contact Monitel to discuss a groundwater monitoring approach that identifies contamination risks early and provides reliable data for regulatory compliance and project decision-making.