Avoid Resampling Soil Vapors: Confirm Tracer Gas in the Field Using a Leak Detector

Importance of the Topic

Vapor intrusion from contaminated soil or groundwater into buildings can lead to elevated indoor concentrations of volatile organic compounds (VOCs), posing health risks. Ensuring the integrity of soil vapor sampling systems is crucial for reliable exposure assessment and remediation decisions.

Objectives and Study Overview

This study presents an in-field screening approach using a tracer gas and portable leak detector to confirm sampling system integrity before collecting soil vapor samples. The primary objective is to reduce the need for costly laboratory reanalysis due to leaks detected after sample submission.

Methodology

Field technicians prepare sampling ports by installing probes and shrouds following established guidelines. A helium tracer is injected into the sealed area around the port, and the Restek Electronic Leak Detector is used to screen for tracer gas leakage at concentrations above 10%, the threshold requiring resealing.

Used Instrumentation

• Restek Electronic Leak Detector for real-time helium detection
• Air canisters or mini-cans compliant with EPA Method TO-15
• Standard sampling probes, shrouds, and flow controllers

Main Results and Discussion

Field trials demonstrated that the leak detector reliably identifies helium concentrations above the 10% threshold within minutes. Early detection of leaks allowed immediate resealing of sampling ports, preventing subsequent sample rejection. This approach streamlines operations compared to waiting for laboratory results, which can delay project timelines and increase costs.

Benefits and Practical Applications

• Substantial reduction in resampling events and associated laboratory expenses
• Immediate verification of sample port integrity in the field
• Improved confidence in soil vapor data quality for risk assessment
• Compatibility with existing sampling protocols (e.g., EPA Method TO-15)

Future Trends and Opportunities

Advancements in portable gas detection and digital logging promise further efficiency gains. Integration with wireless data transmission could enable real-time project oversight. Emerging tracer compounds and sensor technologies may broaden applicability to other environmental media and contaminants.

Conclusion

Implementing in-field helium tracer screening with a portable leak detector provides a simple, cost-effective strategy to ensure sampling system integrity. This proactive approach minimizes resampling, reduces project delays, and enhances overall data reliability in vapor intrusion assessments.

References

New York State Department of Health (2006) Guidance for Evaluating Soil Vapor Intrusion in the State of New York.