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The Representativeness of Subslab Soil Gas Collection as Effected by Probe Construction and Sampling Methods
John H Zimmerman1, Alan Williams2, Brian Schumacher3
1US EPA/ORD/CEMM/WECD, 109 T.W. Alexander Drive, Durham, NC 27709.
Ground Water Monitoring & Remediation
|January 1, 2025
Summary
This study compared subslab soil gas sampling methods for evaluating vapor intrusion. No systematic differences were found between conventional, Vapor Pin, and California-style ports for short-term site management decisions.
Area of Science:
- Environmental Science
- Geotechnical Engineering
- Analytical Chemistry
Background:
- Vapor intrusion (VI) is a significant environmental concern.
- Current U.S. EPA guidance lacks detailed subslab soil gas (SSSG) sampling protocols.
- Standardized SSSG sampling is crucial for accurate VI risk assessment.
Purpose of the Study:
- To compare the effectiveness of different subslab sampling port types and methods.
- To provide data for improving future U.S. EPA vapor intrusion guidance.
- To evaluate short-range temporal differences in SSSG sampling.
Main Methods:
- Three subslab port styles (Conventional, Vapor Pin, California) were installed in duplicate.
- Active sampling utilized modified U.S. EPA Methods TO-15 and TO-17 with canisters and sorbent tubes.
- Passive sampling used sorbent tubes following modified EPA TO-17.
Main Results:
- No systematic differences in sample results were observed between the three port styles.
- Active and passive sampling methods yielded comparable data for durations under two weeks.
- Onsite gas chromatography-electron capture detection (GC-ECD) was used for analysis.
Conclusions:
- Site management decisions are unlikely to differ based on port style or sampling method for short-term assessments.
- The study provides valuable data for refining SSSG sampling recommendations in VI guidance.
- Further research may explore longer-term sampling efficacy and different site conditions.
