Abstract: A method for incinerating contaminated soil or other material utilizing an incinerator, such as a CBC, which is operated below atmospheric pressure and apparatus for carrying out such decontamination by delivering the soil to be processed in desired particulate size to the incineration unit, e.g., to a recirculation loop through which separated solids are being returned from a cyclone to a CBC. The system for supplying the contaminated soil is isolated from the chute leading to the incineration unit by a feeder that forms an agglomerated plug which serves as a pressure seal and prevents any gas flow therepast. Illustrated are a pair of twin counterrotating screws which include shafts that extend past the ends of the screw flights to locations where rotary cutters having multiple blades are mounted.