Case Study: Accelerating Residential Land Remediation for Story Homes

When developing residential housing, contaminated soil and groundwater pose significant regulatory and scheduling hurdles. In-situ remediation requires precision, adaptiveness, and technical expertise to clear environmental compliance checks without stalling construction timelines.

Recently, Cowens Ltd completed a complex land remediation project for Story Homes, utilizing advanced Dual-Phase High Vacuum Extraction (DPE) to clear a residential development site efficiently, safely, and ahead of schedule.

The Challenge: Free Product & High Water Tables

During the initial site investigation, environmental assessments revealed residual contaminants across free-phase, dissolved-phase, and vapour-phase components.

The site conditions presented two major technical challenges:

• Free-phase product contamination present alongside dissolved compounds.
• A high water table, which rendered traditional in-situ bioremediation methods ineffective due to poor oxygenation and saturation dynamics.

To keep the development moving forward without costly mass soil excavation and off-site disposal, Cowens engineered an in-situ extraction strategy tailored specifically to the hydrogeological conditions.

The Solution: Precision Dual-Phase High Vacuum Extraction (DPE)

Cowens deployed a specialized Dual-Phase High Vacuum Extraction system designed to simultaneously recover liquid contaminants and volatile organic compounds (VOCs) from the subsurface.

Key technical highlights of our delivery included:

• Optimized Zone of Influence: Well spacing and extraction rates were systematically calibrated to maximize contaminant drawdown across complex ground conditions.
• Real-Time Monitoring: Utilizing inline Flame Ionization Detector (FID) VOC analysis, our engineers continuously tracked vapour concentrations to gauge extraction efficiency.
• Automated Telemetry: Integrated telemetry systems provided round-the-clock remote monitoring and automatic condition alerts, ensuring peak operational uptime.
• Asymptotic Recovery Principles: Extraction was targeted dynamically, applying the asymptotic mass recovery curve to determine the exact point of diminishing returns and verify completion.

The Outcome: Cost Efficiency & Accelerated Civil Works

By combining real-time data tracking with flexible site management, Cowens delivered maximum environmental remediation with minimum site disruption.

Key Success Metrics:

• Fully Compliant: Achieved total sign-off from both the local environmental regulators and the client.
• On Budget & Schedule: Delivered best-value engineering without cost overruns.
• Overlapping Timelines: Because our extraction footprint was tightly controlled and monitored remotely, Story Homes was able to commence civil engineering works while remediation was still active on site.

By enabling civil works to start early, Cowens significantly reduced the overall project schedule, allowing Story Homes to move forward with house building faster and more cost-effectively.