Australia's First CAT 100 Remediation Injection
Project Overview
Legion Drilling successfully delivered Australia's first CAT 100 remediation injection program, treating chlorinated hydrocarbon contamination beneath an active Sydney roadway without excavation, road closures, or disruption to traffic.
Working alongside Senversa and AST Environmental, the project demonstrated how advanced in-situ remediation technologies can achieve significant contaminant reduction beneath critical infrastructure while avoiding many of the costs, risks, and operational impacts associated with traditional excavation-based approaches.
Nearly 12 months after implementation, monitoring results recorded contaminant concentrations decreasing by several orders of magnitude, providing strong evidence of the effectiveness of the treatment strategy.
The Challenge
The contamination plume was located beneath an active Sydney carriageway, including a busy bus lane and multiple traffic lanes.
Traditional remediation methods would likely have required excavation, extensive traffic management, spoil disposal, and major disruption to road users and surrounding businesses.
The project team needed to:
Treat chlorinated hydrocarbon contamination in situ
Maintain normal traffic operations
Avoid excavation and contaminated spoil handling
Prevent surface breakout during injection
Deliver treatment precisely within the targeted subsurface interval
Generate comprehensive compliance and quality assurance records
This was not simply a drilling project. Success depended on accurately delivering the remediation amendment into the target zone and ensuring effective distribution throughout the contaminated area.
The Solution
Legion Drilling utilised a Geoprobe direct push drilling system combined with specialised remediation injection equipment designed and built in-house.
The CAT 100 amendment combines three remediation mechanisms in a single treatment solution:
Granular Activated Carbon (GAC)
Activated carbon immobilises contaminants and reduces their movement through groundwater.
Zero-Valent Iron (ZVI)
Embedded iron particles chemically break down chlorinated hydrocarbons through reductive dechlorination.
Microbial Consortium
Specialised microorganisms biologically degrade contaminants into non-toxic end products.
Together, these treatment pathways provide both immediate contaminant control and long-term destruction of the contaminant mass.
Legion Drilling's Role
Legion Drilling was responsible for field delivery of the injection program, including:
Direct-push drilling operations
Injection equipment deployment
Preparation and management of amendment slurry
Real-time pressure and flow monitoring
Treatment placement verification
Quality assurance documentation
The works were completed using a Geoprobe direct-push rig supported by specialist high-pressure injection equipment developed by Legion Drilling.
Unlike conventional environmental drilling programs focused on sampling or monitoring well installation, this project required precise subsurface placement of treatment material. Injection pressures, flow rates, treatment volumes, and injection depths were continuously monitored and recorded to ensure treatment objectives were achieved.
Technical Challenges
One of the critical challenges was delivering treatment beneath a live roadway while preventing surface breakout or unintended migration of injected material.
Carbon-based remediation amendments are delivered as a slurry and require careful preparation prior to injection. The product must be correctly mixed and sheared to maintain flowability and achieve uniform distribution throughout the target treatment zone.
Accurate pressure management and experienced operators were essential to ensure treatment material was placed within the designated intervals without compromising surrounding infrastructure.
The project highlighted the importance of specialist injection equipment and trained remediation crews, demonstrating that successful remediation delivery requires expertise that extends beyond traditional drilling activities.
Results
Post-treatment monitoring has provided strong evidence that the remediation program is achieving its objectives.
Key outcomes include:
Significant Reduction in Contaminant Concentrations
Monitoring results show chlorinated hydrocarbon concentrations have decreased by several orders of magnitude compared with pre-treatment conditions.
Some monitoring locations recorded concentrations exceeding 60 mg/L prior to treatment, which reduced to approximately 1-2 mg/L during subsequent monitoring rounds.
Reduction in Plume Size
Monitoring indicates that the contaminant plume has contracted following treatment, demonstrating reduced contaminant mobility and migration.
Enhanced Biological Activity
Groundwater chemistry and microbiological testing have confirmed increased populations of degradative microorganisms capable of breaking down chlorinated hydrocarbons through reductive dechlorination pathways.
The treatment process is successfully converting contaminants into benign end products, including ethene.
Industry Significance
This project represents an important milestone for environmental remediation in Australia as the first application of CAT 100 technology within the country.
The successful delivery demonstrates the viability of advanced in-situ remediation techniques for treating contamination beneath infrastructure that cannot be excavated, including:
Roads and highways
Industrial facilities
Commercial developments
Defence sites
Aviation infrastructure
Operating plants and utilities
As regulators and site owners increasingly seek sustainable alternatives to excavation and disposal, in-situ remediation technologies provide an effective solution that minimises disruption while delivering measurable environmental outcomes.
Client Benefits
The project demonstrated several advantages of advanced in-situ remediation:
No excavation required
No contaminated spoil removal
No road closures
Minimal disruption to surrounding stakeholders
Reduced environmental footprint
Faster project delivery
Lower infrastructure impacts
Proven remediation performance
Why This Matters
Many contaminated sites across Australia exist beneath roads, industrial facilities, airports, service stations, manufacturing sites, and operating commercial infrastructure where excavation is costly, disruptive, or impractical.
This project demonstrates that complex contamination can be effectively treated in place while maintaining site operations and protecting critical infrastructure.
For environmental consultants, site owners, regulators, and contractors, it provides a proven Australian example of how advanced injection technologies can deliver measurable remediation outcomes while reducing project risk and disruption.
Outcome
Australia's first CAT 100 injection project established a new benchmark for environmental remediation delivery.
By combining innovative treatment technology, specialist injection systems, and highly controlled execution, Legion Drilling successfully treated contamination beneath critical infrastructure without excavation or operational disruption.
The project's success positions Legion Drilling as a trusted partner for complex environmental remediation projects and demonstrates the company's capability to deliver advanced in-situ remediation solutions in challenging operating environments.