Abstract: An undercutter apparatus for scooping out contaminated gravel from beneath railroad tracks is designed for use off of the rail road tracks. It can be used when the grade of the ground adjacent to the railroad tracks is quite different from the grade of the railroad tracks. The apparatus includes a control head mounted on an excavator with the control head carrying hydraulically operated means for pivoting the undercutter bar 180° about a vertical axis; for pivoting the distal end of the undercutter bar up and down relative to the proximal end of the undercutter bar approximately 60° above or below in normal horizontal position; and for driving a continuous loop undercutter chain around the undercutter frame for dragging out the contaminated gravel. The undercover apparatus can be a locked into any selected position within these ranges of motion controlled by the control head, or additional positions controlled by operation of the excavator boom and used in that position.