Remediation on Operational Sites: Managing Contamination Without Stopping the Project
Contaminated land remediation is comparatively straightforward when an entire site can be fenced off, excavated and handed over to a remediation contractor.
Many projects do not have that luxury.
Service stations need to continue selling fuel. Industrial facilities need to maintain production. Warehouses require truck access. Commercial properties have tenants and customers. Transport, utility and public infrastructure may provide services that cannot simply be taken offline while contaminated soil is removed.
On these sites, the remediation problem extends beyond contamination.
The project also needs to manage:
operational continuity;
access and traffic;
interaction between workers and remediation contractors;
underground and above-ground services;
contaminated soil and groundwater;
airborne contaminants;
noise, dust and odour;
temporary stockpiles;
waste movements;
plant interaction;
emergency access;
validation; and
the sequence in which areas become available for remediation.
The technically ideal remediation method may therefore be completely impractical if it requires the entire facility to stop operating.
Successful remediation of an operational site depends on developing a strategy that manages the contamination and works within the physical and operational constraints of the facility.
The objective is not to avoid disruption entirely.
It is to understand where disruption is genuinely required and design the remediation so that impacts on the wider operation are controlled and proportionate.
Operational Constraints Need to Form Part of the Conceptual Site Model
A contaminated land Conceptual Site Model is generally used to understand:
Source → Pathway → Receptor
On an operational site, however, remediation planning also needs to understand how people and activities move through the property.
A warehouse may have:
staff parking;
loading docks;
heavy-vehicle routes;
pedestrian areas;
underground services;
operational buildings;
chemical storage;
fire access; and
areas that cannot be taken offline simultaneously.
A service station may need to maintain:
customer access;
fuel dispensing;
tanker deliveries;
electrical and fuel infrastructure;
shop access; and
separation between the public and remediation works.
An industrial facility may contain process equipment, pipelines, hazardous chemicals and critical services that make unrestricted excavation impossible.
These constraints should be understood before the remediation strategy is selected.
Otherwise, a technically valid Remediation Action Plan can become difficult or impossible to implement once the contractor arrives on site.
Start by Defining What Actually Needs to Stop
There can be a tendency to approach contaminated land remediation as an all-or-nothing activity:
Either the facility operates, or remediation occurs.
In practice, the site can often be divided into operational and remediation zones.
The first question should therefore be:
Which activities actually conflict with the remediation works?
A localised excavation in one corner of an industrial property may not require the entire facility to close.
It may instead require temporary relocation of vehicles, establishment of an exclusion zone and diversion of one traffic route.
Remediation beneath a loading dock may be more disruptive because the operational function and contamination occupy the same physical area.
Understanding this difference allows the project team to focus controls on the activities that genuinely interact with the remediation.
This is particularly important on large sites where shutting down the entire operation because one area requires remediation may create significant cost with little additional environmental or safety benefit.
Staging Is Often the Most Important Remediation Control
Staged remediation can allow operational areas to remain available while contaminated areas are progressively isolated, remediated, validated and returned to service.
For example, a contaminated yard might be divided into several remediation stages.
Stage 1: establish temporary traffic arrangements and isolate the first remediation area.
Stage 2: excavate, manage and validate the affected material.
Stage 3: reinstate the area sufficiently for operational use.
Stage 4: transfer the exclusion zone to the next remediation area.
This approach can significantly reduce the operational footprint of the works.
But staging introduces its own technical considerations.
The RAP needs to consider:
whether contamination extends between stages;
how temporary boundaries will be controlled;
where excavated material will be placed;
whether validated areas could be re-contaminated by later works;
how stormwater will be managed;
how vehicles will move between contaminated and clean areas; and
how each completed stage will be documented.
Staging should therefore be part of the remediation design, rather than a contractor convenience decided after remediation has commenced.
Operational Areas and Remediation Areas Need Clear Separation
One of the most important controls on a live site is physical separation.
Remediation activities can involve contaminated soil, moving plant, open excavations, dust, groundwater, waste trucks and potentially hazardous materials.
These activities should not unnecessarily interact with normal site operations.
Depending on the project, separation may involve:
temporary fencing;
exclusion zones;
controlled access points;
dedicated plant routes;
pedestrian diversions;
temporary barriers;
warning signage;
spotters or traffic controllers;
decontamination zones; and
clean and contaminated material-management areas.
SafeWork NSW identifies excavation work as construction work and highlights hazards including moving plant, underground services, excavation collapse and airborne contaminants. Work involving asbestos disturbance or excavation near powered mobile plant can also meet the definition of high-risk construction work, requiring appropriate planning and control.
On operational sites, these hazards exist alongside workers and activities that may have nothing to do with the remediation.
The interface between the two therefore needs to be deliberately managed.
Traffic Management Can Become Part of the Remediation Strategy
At many commercial and industrial properties, vehicle access is fundamental to operations.
A remediation excavation may sit directly within:
a truck route;
customer parking;
a loading area;
a driveway;
an emergency-access route; or
the only access to part of the facility.
That can make traffic management a project-critical remediation issue.
The remediation sequence may need to consider whether:
an alternative route can be established;
temporary pavement is required;
works need to occur outside operating hours;
excavation can be reduced through another remediation method;
one half of an access route can remain available;
stockpile and waste-truck movements can be separated from operational traffic; or
the area needs to be temporarily closed and rapidly reinstated.
This illustrates a broader principle.
The best soil remediation strategy is not selected solely from contaminant concentrations.
Constructability and operational constraints matter too.
Existing Services Can Dictate How Remediation Is Undertaken
Operational sites typically contain more active infrastructure than vacant development sites.
This might include:
electricity;
gas;
water;
sewer;
telecommunications;
fire services;
process lines;
fuel lines;
compressed air;
chemical pipelines; and
drainage infrastructure.
The consequences of damaging those services can be significantly greater on an operational facility.
Some may also represent contamination pathways themselves.
A service trench containing permeable bedding material can provide a preferential pathway for petroleum hydrocarbons or contaminated groundwater.
SafeWork NSW requires information about underground essential services to be obtained before excavation begins and provided to people carrying out the excavation.
For remediation planning, the issue goes beyond locating services.
The consultant and project team may also need to consider:
whether services can remain operational during excavation;
whether temporary bypasses are required;
whether contaminated soil extends beneath services;
whether contaminated bedding material requires removal;
whether excavation around the infrastructure is physically possible; and
whether leaving some contamination in place with appropriate controls is preferable to creating a greater operational or safety risk.
This can materially influence the remediation method.
Sometimes Containment Is More Practical Than Excavation
Operational constraints can change the balance between remediation options.
Imagine contamination beneath a heavily trafficked industrial hardstand.
Full excavation might require:
shutting down the operational area;
demolishing pavement;
relocating services;
removing large volumes of soil;
importing replacement material; and
reconstructing the pavement.
If the contamination does not present an unacceptable migration or vapour risk and direct contact can be effectively controlled, retaining the material beneath an appropriate engineered barrier may warrant consideration.
That decision must be supported by the risk assessment and remediation objectives.
It should not simply be adopted because excavation is inconvenient.
However, it demonstrates why contaminated land remediation should consider more than removal.
The appropriate solution is the one that manages the identified risk and remains workable over the life of the site.
Our article on soil remediation methods discusses excavation, treatment, stabilisation, containment and in situ management in more detail.
Remediation Beneath Operating Buildings Is a Different Problem Again
Contamination may also extend beneath buildings that need to remain occupied or operational.
Direct excavation may not be immediately possible.
Depending on the contamination, potential strategies might involve:
remediation from accessible perimeter areas;
in situ treatment;
vapour mitigation;
groundwater treatment;
staged remediation during future building works;
containment and long-term management; or
targeted access through sections of the building where feasible.
The appropriate response depends heavily on the contaminant.
A relatively immobile metal contaminant beneath an intact industrial slab presents a very different problem to volatile petroleum hydrocarbons beneath an occupied building.
The Conceptual Site Model needs to account for the building rather than simply treating it as an obstacle to excavation.
In some circumstances the building itself interrupts an exposure pathway.
In others, it may create a vapour-intrusion pathway that increases the importance of the contamination.
Petroleum Sites Require Particular Care
Operational service stations, fuel depots and industrial facilities can be especially challenging because the infrastructure that caused the contamination may still be in use.
A site might contain:
operating underground storage tanks;
former tanks;
fuel dispensers;
product lines;
contaminated soil;
LNAPL;
a dissolved groundwater plume; and
active customer or operational areas.
Excavating around live fuel infrastructure introduces obvious constraints.
In these circumstances, remediation may need to combine targeted source removal with groundwater remediation, product recovery, monitoring or other treatment methods.
The source, soil, groundwater and vapour system needs to be considered as a whole.
This is explored further in Integrating Soil and Groundwater Remediation on Petroleum-Impacted Sites.
SafeWork NSW also identifies tanks, pipework, fuel-dispensing infrastructure and contaminated ground or groundwater as potential considerations where demolition involves chemical installations.
Worker Exposure Needs to Be Considered Beyond the Remediation Crew
On a closed remediation site, access can generally be restricted to workers directly involved in the remediation.
On an operational site, other people may be working only metres away.
This creates additional exposure considerations.
Potential hazards can include:
contaminated dust;
asbestos fibres;
volatile organic compounds;
contaminated water;
odours;
contaminated soil tracking;
noise;
mobile plant; and
vehicle movements.
Controls therefore need to protect not only remediation workers but also other site workers, contractors, customers and visitors.
Depending on the contamination and remediation method, this could involve:
dust suppression;
air monitoring;
vapour monitoring;
temporary enclosures;
controlled excavation methods;
covering stockpiles;
decontamination;
dedicated haul routes;
work scheduling; and
temporary relocation of nearby activities.
Where asbestos-contaminated soil is involved, work-zone separation and decontamination become particularly important. SafeWork NSW requires decontamination facilities for asbestos work areas and for people or equipment involved in the work.
This is one area where integrating contaminated-land, asbestos and occupational-hygiene capability can materially simplify project delivery.
Dust and Odour Can Become Operational Problems Before They Become Environmental Problems
Even where monitoring demonstrates that airborne concentrations remain below relevant criteria, visible dust or strong odour can cause significant concern on an operational site.
Workers may not know what material is being excavated.
Customers may see personnel in protective equipment.
Nearby tenants may smell hydrocarbons.
Complaints can quickly escalate if communication has not been planned.
For remediation on active sites, dust and odour management should therefore consider both actual exposure risk and the practical impact on surrounding operations.
Controls may include:
staged excavation;
wet methods;
covered loads;
minimising drop heights;
temporary enclosure;
rapid removal of odorous material;
vapour suppression;
appropriate air monitoring; and
communication with affected stakeholders.
A technically compliant remediation program can still cause unnecessary disruption if these practical issues are ignored.
Stockpile Locations Need More Thought on a Live Site
Excavated soil usually needs somewhere to go before it is reused, treated or removed from site.
On operational sites, available space may be limited.
Poorly located stockpiles can obstruct:
loading areas;
traffic routes;
emergency access;
drainage;
parking;
operational equipment; or
future remediation stages.
The RAP and remediation methodology should therefore consider stockpile areas before excavation begins.
The selected area also needs to be suitable from an environmental perspective.
Considerations can include:
underlying surface;
runoff;
dust;
proximity to sensitive receptors;
separation between different material types;
accessibility for sampling;
truck access; and
whether the material could interfere with future stages.
Where excavated material will leave the site, waste classification should be planned early enough that laboratory turnaround does not leave large volumes of soil occupying critical operational space.
The Remediation Program Should Identify Hold Points
On operational sites, mistakes can be expensive.
Once contaminated soil has been excavated and mixed, a service has been exposed, or a traffic route has been closed, reversing the decision may be difficult.
Defined hold points can prevent the works from progressing beyond critical stages without the required environmental or technical confirmation.
Typical remediation hold points might include:
confirmation of service locations before excavation;
consultant inspection after removal of the initial source;
classification before material leaves the site;
validation of excavation walls and base;
confirmation before backfilling;
inspection of capping layers;
survey of final remediation levels; or
approval before an area is returned to operational use.
SafeWork NSW likewise recommends consultation with competent professionals at critical excavation stages and the use of predetermined hold points where relevant to safe excavation.
For remediation, hold points provide the same practical benefit:
make the decision while the evidence is still visible and before the next activity removes the opportunity to check it.
Validation Needs to Follow the Staging Strategy
Validation becomes particularly important where remediated areas are progressively returned to operational use.
If an excavation is backfilled and reopened to traffic before appropriate validation evidence has been collected, gaining access again can be expensive and disruptive.
The remediation and validation strategy should therefore mirror the construction stages.
For each stage, the consultant should understand:
what has been remediated;
which remediation criteria apply;
what needs to be sampled or inspected;
which records need to be collected;
whether unexpected conditions were encountered;
whether any residual contamination remains;
whether the area can be reinstated; and
whether any ongoing controls are required.
The NSW EPA's contaminated-land reporting framework requires RAPs to define the remediation strategy, implementation requirements and validation approach, and to document restrictions or long-term management where residual contamination remains.
Validation should therefore be treated as part of the remediation sequence, not as a reporting exercise undertaken after the entire project has finished.
Unexpected Finds Are More Disruptive on Operational Sites
Remediation investigations are based on discrete investigation points.
Earthworks expose significantly more of the subsurface.
Unexpected contamination can therefore still occur.
Examples might include:
buried drums;
additional underground tanks;
asbestos-containing material;
hydrocarbon staining;
odorous material;
ash or industrial waste;
undocumented pipelines;
contaminated groundwater; or
fill extending deeper than anticipated.
On a vacant remediation site, the affected excavation may simply be expanded.
On an operational site, doing so may extend into a road, building, service corridor or critical operating area.
The RAP should therefore provide a clear unexpected-finds and contingency framework.
The response should address:
What has been found?
Does it change the Conceptual Site Model?
Can it be managed within the approved remediation strategy?
Does the work area need to expand?
What additional investigation is required?
Will operations be affected?
What decisions need to be made before works continue?
This allows the project team to respond systematically rather than making ad hoc decisions while plant and contractors are standing by.
Groundwater Remediation May Be Easier to Integrate Than Large Excavations
Where contamination extends into groundwater, active operations may restrict the ability to undertake widespread excavation.
In some settings, groundwater remediation infrastructure can be installed and operated within relatively small controlled areas while the broader facility remains operational.
This might include:
monitoring wells;
recovery wells;
extraction systems;
treatment compounds;
product-recovery systems; or
in situ treatment infrastructure.
That does not make groundwater remediation simple.
Infrastructure still needs to coexist with traffic, services and site operations.
But it illustrates how the remediation method can be selected partly around the site's operational constraints.
For petroleum-impacted sites in particular, a combination of source removal and targeted groundwater management may sometimes provide a more practical strategy than attempting unrestricted excavation across the entire affected area.
Night and Weekend Works Are Not Automatically the Answer
One obvious solution to operational conflict is to perform remediation outside normal operating hours.
That can be useful.
But it should not be assumed to solve every problem.
Out-of-hours work can introduce:
noise restrictions;
reduced access to operational staff;
fatigue;
lighting requirements;
security issues;
laboratory and waste-facility availability;
supervision constraints; and
limits on truck movements.
Sometimes short-duration night or weekend works can significantly reduce disruption.
For longer remediation programs, properly staged daytime works may be safer, cheaper and easier to control.
The appropriate arrangement should follow the actual project constraints rather than a blanket assumption that remediation must occur when nobody else is present.
Communication Is a Technical Control
On operational remediation projects, communication can directly affect whether controls work.
The site operator needs to understand:
where remediation will occur;
when exclusion zones will change;
which routes will be unavailable;
which activities cannot occur near the remediation area;
what to do if unexpected conditions are observed; and
when remediated areas can safely return to service.
The remediation contractor needs to understand the facility's operational constraints.
The environmental consultant needs to understand both.
This interface is particularly important when decisions are changing rapidly.
A technically strong RAP does not eliminate the need for coordination during the works.
It provides the framework within which those decisions can be made.
Example: Operational Industrial Yard
Consider an industrial facility where historical fill containing metals and asbestos is identified beneath part of an operational yard.
The yard provides vehicle access to a warehouse and cannot be closed completely for several weeks.
One approach would be to shut the entire yard, excavate all affected fill and reinstate it as a single project.
That may provide a simple remediation footprint but a poor project outcome.
An alternative might involve:
dividing the affected area into manageable remediation cells;
maintaining a temporary traffic route around each cell;
establishing controlled excavation and decontamination zones;
excavating and removing affected material;
undertaking validation before backfilling;
reinstating each completed area; and
progressively transferring operations and remediation into the next stage.
The environmental endpoint may be identical.
The difference lies in how the remediation is delivered.
Example: Live Commercial Fuel Facility
Now consider an operational fuel facility with a historical release associated with former underground infrastructure.
The contamination may include shallow petroleum-impacted soil, residual hydrocarbons near groundwater and a dissolved groundwater plume.
Excavating the entire source and plume footprint may conflict with operating infrastructure.
A staged strategy could instead combine:
removal of accessible source material;
targeted excavation during scheduled infrastructure shutdowns;
groundwater monitoring;
recovery of mobile product where present;
active treatment of higher-concentration areas; and
monitoring of the residual plume.
The remediation methodology would be driven not only by hydrocarbon concentrations but by the relationship between the source, groundwater, operating infrastructure and receptors.
That is the essence of risk-based remediation on operational sites.
Remediation Planning Should Ask How the Site Needs to Operate Tomorrow
Contaminated land remediation often focuses heavily on historical activities:
What happened here?
What leaked?
Where was fill placed?
Those questions are essential.
On operational sites, another question is equally important:
What does this site need to keep doing while we remediate it?
That question can influence:
remediation method;
staging;
access;
stockpiling;
air monitoring;
worker controls;
waste movements;
validation;
timing; and
long-term management.
The objective is not to compromise the remediation outcome in order to maintain operations.
It is to design a remediation program that achieves the required environmental outcome without creating disruption that provides no corresponding reduction in risk.
Soil and Groundwater Remediation on Operational Sites
Confluence Environmental provides soil and groundwater remediation and validation services for commercial, industrial, infrastructure and operational sites across NSW.
Our team can support projects from investigation and remediation planning through to on-site implementation, contaminated soil management, groundwater remediation, environmental monitoring and final validation.
Services can include:
review of existing investigations and RAPs;
Detailed Site Investigation;
remediation planning;
staged remediation design;
contaminated soil removal;
groundwater remediation and monitoring;
asbestos in soil management;
remediation supervision;
air and environmental monitoring;
waste classification;
unexpected-find assessment;
validation sampling; and
Site Validation Reports.
For operational sites, our focus is on developing remediation strategies that are technically defensible and capable of being implemented within the practical constraints of the facility.
Where possible, remediation, validation and operational requirements are considered together so that the site can continue functioning while identified contamination risks are progressively addressed.