PNEUMATIC PUMPING TEST FOR SOIL VACUUM EXTRACTION

In-situ pneumatic pumping tests were performed to estimate the pneumatic permeability at a site containing soils contaminated with aviation gasoline. Determination of pneumatic permeability was necessary to evaluate soil-air discharge or pore volume exchange rates. Pressure propagation was measured in clustered vapor probes during the application of vacuum and positive pressure. An analytical solution for soil-air pressure distribution with a non-linear data fitting algorithm was adopted to obtain the pneumatic permeability from soil-air pressure distribution. Pneumatic pumping tests indicated substantially higher air discharge rates in the immediate vicinity of wells. The air discharge rate dissipated rapidly as distance from the wells increased. Application of increased vacuum or injection pressure resulted in substantially increased airflow in the immediate vicinity with small changes at a distance. This fact indicates that effective design should be based on air flow fields near wells, and the site specific design criteria should be determined with carefully conducted tests.