Soil Extraction Measurements

Soil extraction is applied to clean soils from Diesel, oil or VOC (volatile organic componds) spillage. A standard method to identify the influence of the extraction system are local underground pressure measurements. However, the information about soil structure and flow paths in the soil is very limited. Vacuum data could provide a rough airflow pattern picture if the soil is homogeneous. Most often this isn't the case. There are layers with lower and higher permeability which have a big influence on the flow pattern. This can not be achieved with pressure tests.

Tracer gas tests allow a simple way to quantitatively measure the airflow field in the soil.

  1. Do short-circuit pathways for the air exist?
  2. Are there significant stagnant zones?
  3. Is the zone of contamination being effectively flushed?
  4. Are current operating conditions optimizing vapor flow rates through the zone of contamination?
  5. Is soil vapor extraction delivering oxygen for biodegradation?

The answers of tracer gas test are besides to above questions :

  • an estimate of the breakthrough time (time from tracer injection start until 50% of the tracer pulse has arrived)
  • calculation of effective air-filled porosity
  • calculation of the velocity at the injection point.