Speciality Solutions

Borehole | VaporTecTM | Landfill | Vapor Intrusion/Indoor Air

Direct Push sampling and on-site analysis form the core of Integrated, Expedited Site Assessment. Significant further enhancements can be achieved by integrating a number of other tools and services, all of which are available from ESN.

Borehole Geophysics

Borehole geophysical methods generate accurate and inexpensive geological data that are essential for the full characterization of a site and the design of remedial systems. Borehole Geophysical logs provide high resolution, continuous information that can be accurately and readily interpreted to determine lithology, electrical resistivity/conductivity, bulk density, porosity, moisture content, and other information critical to both modeling of contaminant plumes and designing remedial systems.

Recent advances in both design of logging tools and Direct Push technologies allows a near full marrying of borehole geophysics to Direct Push sampling. ESN offers a full line of borehole logging services to enhance the understanding of the subsurface environment and improve the design and operation of remedial systems. Among the tools and applications ESN employs are:

Logging Tool
Natural Gamma
Gamma-Gamma
Neutron
Conductivity/Resistivity
Sonic (including tomography)
Application
Lithology/Stratigraphic Correlation
Bulk Density/Porosity
Moisture Content/Water Level
Lithology/Stratigraphic Correlation
Porosity (infer permeability)

Each tool has optimum application and utility. Combined with the descriptive logs associated with soil sampling, an objective and powerful set of data can be developed for use in plume characterization, modeling, and design of remedial systems. All of these tools can be used in association with ESN’s Direct Push rigs, and ESN has significant experience in the application and interpretation of geophysical data.
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VaporTecTM Passive Soil Gas

Passive soil gas is a specialty soil vapor tool, ideally designed for early stage projects (where quantitation is less important), and where either logistical or environmental conditions make active soil gas difficult. The types of conditions include: impermeable lithologies, deep ground water, target compounds including semi-volatile organics, logistics that prevent use of Direct Push probe rigs.

ESN’s VaporTecTM Passive soil gas samplers consist of hydrophobic sorbents (tailored to the project objectives), transported in sealed containers, which are opened and exposed to naturally migrating vapors for an extended period of time to concentrate the vapors for analysis. Many geometries have been developed, but all rely on the occurrence of vapors from sources (in and on ground water and in the vadose zone) to migrate to the sampler and trap (by preferred Koc) onto the activated, non-polar sorbent. When the exposure time (1 day to 30 days) is complete, the samplers are returned to a fixed base lab for analysis.

Extended exposure times allow for the continuous collection and therefore concentration of the vapors on a trap. This improves the sensitivity of the sampling several orders of magnitude better than that available from conventional active soil gas sampling and analysis. It also allows detection of many semi-volatile compounds, normally undetectable by soil gas surveys.
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Landfill Testing

Several types of landfill testing are conducted by ESN. The most common is EPA’s Tier II testing, involving the use of Method 25C to test for the total loading of Non-Methane Organic Compounds (NMOCs). The method stipulates the use of Stainless Steel probes and a specialized sample inlet system to acquire a soil gas sample from within the waste material (monitoring onsite for O2, CO2, and methane, and H2S when appropriate) to assure a quality sample. The method also requires Summa Canister collection of the samples for TO-14 and other analyses in a fixed base lab. ESN has conducted hundreds of Tier II landfill tests across the country and is a preferred contractor.

In addition, landfills are often suspected of being sources of contamination of ground water by downward vapor migration or of endangering surface building occupants via later and upward vapor migration. ESN has the most experience of any contractor in sampling, analysis, and assessment of the risks associated with these conditions of any contractor in the United States.
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Vapor Intrusion/Indoor Air Testing

Indoor air testing, usually associated with vapor plumes from subsurface contamination, is an increasingly frequent issue under RBCA guidelines. Contamination can be from the subject site or from adjacent or upgradient sites. Vapor movement in the vadose zone is very fast, and can therefore be potentially risky if the vapor concentrations near the source are high.

Because modeling creates huge uncertainty, and because conventional soil gas sampling and analysis is fully inadequate, ESN has developed protocols (in accord with EPA and State guidelines) for sampling and analysis of soil gas near and beneath structures. Actual, very low detection limit, data and in vertical profile, allows a full understanding of the dynamic behavior of vapors in the vadose zone and allows a much more accurate prediction of indoor air concentrations.

When predictions of indoor air concentrations approach or exceed PRGs, then it is essential to start actual indoor air sampling. This is conducted using Summa canisters over 24+ hour sampling periods, and analysis by TO-14, TO-15, or TO-17, all of which are conducted by ESN.
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