Soil Vapor Surveys in Real Estate Transactions

Dec 15, 2018

Environmental Enlightenment #304

Toxic, volatile substances in soils present a specter of intrusion into inhabited spaces and impact on the health of the occupants. The volatile chemicals can originate on the property or invade from spills in the neighborhood.

Here’s a case of subsurface vapors (yellow cloud) invading an apartment complex (right) from the source in a commercial plaza on the left.

And, here’s a case where an industrial operation (Source) has inflicted the neighbors with subterranean vapors that required abatement at a neighboring, commercial operation.

In real estate transactions, the contaminants of concern in the soil vapor are:

  • Gasoline compounds in service stations
  • Dry-cleaning solvents at cleaners
  • Chlorinated solvents in commercial and industrial operations

We employ Phase II Environmental Site Assessment and seek fast, low-cost answers as to whether toxic, volatile substances reside in the subsurface.

Here is how it’s done:

We collect soil-vapor samples through hollow probes driven into the ground.
We drive these probes into the ground using hydraulic-push power or rotating hammer drills.
We suck out representative samples into syringes and immediately inject the sampled vapor into analytical equipment in an onsite mobile laboratory.

Soil gas data, when analyzed in the field, is realtime data and the scope of the survey can be adjusted to pinpoint “hot spots” and collect additional data in one mobilization.

The results can be plotted on a diagram and lines of equal concentrations are drawn, enabling us to spot the source location.

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