Vadose Zone

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Definition - What does Vadose Zone mean?

The vadose zone (also known as the unsaturated zone) refers to the area from the ground surface to the water table. It includes the surface soil, unsaturated sub-surface soil including weathered and unweathered material, and the capillary fringe.

The vadose zone can be shallow or very deep depending on how far below the surface is the water table. In the petroleum industry, air sparging is done to remove contaminants from the sub-surface by installing a soil vapor extraction (SVE) system in the vadose zone.

Trenchlesspedia explains Vadose Zone

Water present in the vadose zone has less pressure than the atmospheric pressure. The capillary fringe that exists just above the water table is also saturated and is not included in the vadose zone. Water movement in the vadose zone is an important factor for the transport of contaminants.

Slotted wells are installed in the vadose zone in the location of the contaminated soil. The well is connected to a vacuum pump and sealed at the surface.

A vacuum is applied to the slotted wells creating airflow in the region. When the vapor-phase equilibrium is reached, the volatile components migrate from the liquid into the vapor phase and reach the slotted wells from where they are removed using the vacuum extraction system.

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