Abstract: A system for drilling and simultaneously installing a relatively large production casing along an invert underground arcuate path beneath an obstacle is disclosed. A plurality of production casing segments, each having preformed curvature corresponding to the radius of the curvature of the arcuate path, are joined end to end and advanced along the desired path. A drill head is located in front of the leading end of the casing. The drill head is mounted to the casing so that the angular orientation of the drill head relative to the axis of the leading end of the casing is at least partially adjustable. A drill bit is located in front of the drill head and a motor is located within the drill head to drive the drill bit. The drill bit excavates a passageway along the arcuate path in advance of the casing.

Abstract: A system and method for emplacing a relatively large casing under and spanning an obstacle such as a river is disclosed. The casing is emplaced along the arcuate path of a previously bored and placed existing pilot string running beneath the obstacle between positions near ground level on opposite sides of the obstacle. A seal is provided between the outer surface of the leading portion of the casing and the reamed pilot hole so that the drilling mud containing the entrained cuttings flows into the leading end of the advancing casing. In one preferred embodiment a washover pipe circumscribing the pilot string serves the dual function of rotating a case-leading reamer and driving a positive displacement pump-typically of the moineau variety-to evacuate drilling fluid and entrained cuttings. This evacuation can occur through the drill string.