Method and apparatus for in situ decontamination of a site contaminated with a volatile material

A method of removing an organic contaminant from a contaminated region of the earth containing water comprising:

• applying a spatially uniform continuous alternating current conduction frequency electric current to an electrically conductive matrix in electrical contact with a treatment region of the contaminated region of the earth for alternating current electrical conduction heating without arcing using an electrode having a portion buried in the earth and in electrical contact with the conductive matrix to evaporate a portion of the water at a temperature below the normal boiling point of water and to evaporate at least a portion of said contaminant;
• blocking a portion of a surface of the earth above the treatment region to prevent air from flowing nonuniformly into the treatment region;
• and
• applying subatmospheric pressure to a nether collection region via an auxiliary well disposed away from the electrode to draw in ambient air through the treatment region from the surface of the earth without so drying the earth in proximity to the electrode as would substantially interrupt the electrical conduction heating and to collect the water vapor and at the same time the contaminant vapor in the nether collection region.

Apparatus for removing a contaminant from a contaminated region of the earth containing water, comprising:

• an electrically conducting matrix in electrical contact with a treatment region of the contaminated region;
• electrical heating means coupled to the electrically conducting matrix, for heating a treatment region of the contaminated region of the earth by electrical conduction heating produced from a substantially uniform and continuous alternating current conduction frequency electric field without arcing to increase the vapor pressure of the contaminant so that at least a portion of the contaminant becomes vapor at a temperature below the normal boiling point of water;
• an air impermeable sheet resting on the earth above the treatment region for blocking a portion of a surface of the earth above the treatment region to prevent air from flowing nonuniformly into the treatment region;
• and
• vacuum means comprising an auxiliary well, for establishing a region of subatmospheric pressure within or below the treatment region for drawing in ambient air and moving it from the surface of the earth over a controlled flow path through the treatment region so as to transport the contaminant to the collection region in an air-vapor mixture having a high ratio of vapor to air.

Apparatus for removing a contaminant from a contaminated region of the earth, comprising:

• electrical heating means for heating the contaminated region of the earth by electrical displacement current heating produced from a substantially spatially uniform and continuous alternating current conduction frequency electric field without arcing above the boiling point of water to increase the vapor pressure of the contaminant so that at least a portion of the contaminant becomes vapor at a temperature above the boiling point of water;
• an air impermeable sheet resting on the earth above the treatment region for blocking a portion of a surface of the earth above the treatment region to prevent air from flowing nonuniformly into the treatment region;
• and
• vacuum means comprising an auxiliary well, for establishing a region of subatmospheric pressure within or below the contaminated region for drawing in ambient air and moving it at a substantially constant speed from the surface of the earth over a controlled flow path through the contaminated region so as to transport the contaminant to the auxiliary well of the collection region in an air-vapor mixture having a high ratio of vapor to air.