EPA/600/R-98/095

The GORE-SORBER module is a passive soil gas sampler that consists of several separate sorbent collection units called sorbers. Each sorber contains sorbent materials selected for there broad range of volatile organic compounds and semivolatile organic compounds and for their hydrophobic characteristics. The sorbers are sheathed in a vapor permeable insertion and retrieval cord constructed of inert, hydrophobic material that allows vapors to move freely across the membrane and onto the sorbent material and that protects the granular adsorbents from physical contact with soil particulates and water. The GORE-SORBER module was demonstrated in May and June 1997 at two sites: the Small Business Administration (SBA) site in Albert City, Iowa, and the Chemical Sales Company (CSC) site in Denver, Colorado. These sites were chosen because each has a wide range of volatile organic compound (VOC) concentrations and because each has a distinct soil type. The GORE-SORBER Screening Survey was compared to a reference method, active soil gas sampling, in terms of the following parameters:

1. VOC detection and quantitation,
2. sample retrieval time,
3. cost.

The demonstration data indicated the following performance characteristics:

1. The GORE-SORBER Screening Survey detected the same compounds as the reference method, as well as several VOCs that the reference method did not detect.
2. At high contamination levels, the ratio between the mass of contaminant in soil gas detected using the GORE-SORBER module and the concentration of contaminant in soil gas detected using the reference method decreases.
3. The GORE-SORBER modules sample retrieval times were quicker than the reference soil gas sampling method in clay soils at the SBA site and slower in the sandy soils at the CSC site.
4. In this demonstration, the GORE-SORBER modules were left in place for ten days at each site and required an average of sixteen days per site for analysis.
5. The GORE-SORBER Screening Survey cost $125 to $225 per sample plus equipment costs plus mobilization/demobilization costs. Operating costs ranged from $810 to $1540 at both the clay soil site and the sandy site. A site-specific cost and performance analysis is recommended before selecting a subsurface soil sampling method since with any technology selection, the user must determine what is appropriate for the application and project data quality.