Groundwater Monitoring – Why Some Sites Need Ongoing Monitoring
Groundwater contamination can be a complex issue on contaminated sites. Unlike surface soil, groundwater can move through the subsurface and potentially transport contaminants beyond their original source. For some sites, a single groundwater investigation may provide enough information to understand the risk. For others, ongoing groundwater monitoring is needed to understand contaminant behaviour, identify changes over time and demonstrate that management or remediation measures are working.
At Confluence Environmental, we provide groundwater investigation and monitoring services across NSW, helping clients understand groundwater conditions and manage potential contamination risks.
Why Does Groundwater Need to Be Monitored?
Groundwater monitoring may be required where contamination has the potential to migrate through the subsurface or where groundwater represents a potential exposure or environmental pathway.
Potential sources include:
Fuel and petroleum hydrocarbon spills
Former service stations
Industrial chemical storage
Landfills and waste disposal
Contaminated fill
Historical industrial activities
Leaking underground infrastructure
Agricultural chemicals
Whether groundwater monitoring is required depends on the site's history, geology, groundwater conditions and potential receptors.
When Is Ongoing Monitoring Required?
Not every contaminated site requires long-term groundwater monitoring. Ongoing monitoring may be appropriate where:
Groundwater contamination has been identified
A contaminant plume has not been fully delineated
Contamination has the potential to migrate
Remediation has been undertaken and its effectiveness needs to be demonstrated
Natural attenuation is being relied upon as a management strategy
Sensitive receptors may be affected
Monitoring is required as part of a site management or regulatory strategy
The need for ongoing monitoring should be determined through a site-specific Conceptual Site Model, considering the source, pathways and potential receptors.
What Does Groundwater Monitoring Involve?
A groundwater monitoring program generally involves appropriately located monitoring wells. Depending on the site, monitoring may include:
Measuring groundwater levels
Determining groundwater flow direction
Collecting groundwater samples
Laboratory analysis
Tracking contaminant concentrations
Comparing results between monitoring events
Assessing potential contaminant migration
Monitoring locations should provide information about the source area, groundwater flow direction and potential receptors.
What Contaminants Are Monitored?
The analytical program depends on the site's history and known or suspected contaminants. Depending on the site, groundwater may be analysed for:
Petroleum hydrocarbons
BTEX
PAHs
Volatile organic compounds
Heavy metals
PFAS
Pesticides
Other site-specific contaminants
The monitoring program should be tailored to the contamination identified rather than applying the same testing suite to every site.
Why One Groundwater Sample Isn't Always Enough
Groundwater conditions can change over time.
A single sampling event provides a snapshot of conditions at that particular time. It may not show whether contamination is stable, increasing, decreasing or migrating. Repeated monitoring allows trends to be assessed.
For example:
Increasing concentrations may indicate an ongoing source or mobilisation of contamination.
Stable concentrations may indicate relatively consistent groundwater conditions.
Decreasing concentrations may indicate that contamination is naturally attenuating or that remediation is reducing the source.
Changes in groundwater levels can also influence groundwater flow and contaminant movement.
This is why some sites require multiple monitoring events before conclusions can be drawn about long-term conditions.
Monitoring After Remediation
Groundwater monitoring can form an important part of a remediation program. Where a contaminated source has been removed or treated, monitoring may help determine whether:
The contaminant source has been effectively addressed
Groundwater concentrations are decreasing
Residual contamination remains
Contamination is migrating
Further remediation is required
Monitoring can therefore provide evidence that a remediation strategy is achieving its intended objectives.
What Happens If Groundwater Contamination Is Found?
A groundwater exceedance does not automatically mean that a site cannot be developed.
The significance of the result depends on:
The contaminant and concentration
The extent of the contamination
Groundwater flow direction
Potential exposure pathways
Nearby receptors
Proposed land use
Whether concentrations are increasing or decreasing
Further investigation may be required to determine the extent of a contaminant plume or identify the source.
Depending on the circumstances, management may involve source removal, remediation, containment, treatment or monitored natural attenuation.
How Confluence Environmental Can Help
At Confluence Environmental, we provide practical groundwater investigation and monitoring services across NSW, including:
Groundwater monitoring well assessment
Groundwater level measurements
Groundwater sampling
Laboratory analysis
Contaminant plume assessment
Groundwater flow assessment
Long-term monitoring programs
Remediation monitoring
Natural attenuation monitoring
Data trend analysis
Environmental reporting
Need Groundwater Monitoring in NSW?
Confluence Environmental provides groundwater investigations, monitoring, contaminated land assessments, remediation support and environmental consulting across NSW.
Whether you require an initial groundwater assessment or an ongoing monitoring program, we can develop a practical approach suited to your site's contamination risks and project requirements.
Call 1300 855 447 or contact Confluence Environmental to discuss your environmental consulting requirements.