PURPOSE: To treat contaminated soil by an auger method at a jobsite.

CONSTITUTION: The mounting drill includes an elongated hollow drive shaft supported vertically and rotated. The upper end of the drive shaft is connected to a jet flow, the lower end attaches a drill bit 30, and a drill includes the drive shaft and a coaxially extending hollow sleeve 50. A pair of drill blades 62 cantilevered from the sleeve 50 and extended positively reverse directional outward is provided with a plurality of drill teeth 66 directed to the tangential direction of the sleeve 50 along a front edge respectively, in addition, one hollow pipe 70 is extended along a rear edge, and fluid is jetted into soil during drill rotation. A plurality of nozzle orifices 74 are provided. A sensor responds to the drive shaft and the speed of the drill, and fluid jetting is performed by electronic control.