An excavation apparatus having a mast, a sled slidably mounted thereon, a sled driving system for downcrowding and upcrowding the sled along the mast, and non-rotatable but extendable kelly sections that prevent slippage of the sled on the mast. An outer kelly section is attached to the sled, and an inner kelly section is extendable therefrom and retractable therein. A bushing maintains slidable alignment of the kelly sections on the mast. The inner kelly section is automatically powered into and out of the outer kelly section a distance proportional to the distance that the sled is downcrowded or upcrowded along the mast while preventing slippage. A rotary motor, attached to the sled, rotates a telescopic shaft housed within the kelly sections. A transmission secured to the lower end of the inner kelly section increases downhole torque. A boom connector downcrowds and upcrowds the mast for additional drilling depth capability.