Abstract: An underground work chamber assembly including a chamber, elevator shaft, air path, utility path, and slotted grout pipes which is assembled as lowered into a drilled hole on dry land or underwater, the slotted grout pipes facilitating a controlled grouting of the space surrounding the underground work chamber assembly when in place.

Abstract: A caisson and connecting conductor pipe sections are lowered to a predetermined position on the ocean underwater floor. A drill stem having a combined drilling and reaming tool is positioned within the conductor pipe and caisson. Drilling mud is reversed-circulated through the annular space between the conductor pipe and caisson and the drill stem, the drilling mud returning through the drill stem. The tool mounted on the drill stem is utilized to drill to a predetermined depth whereupon one or more reaming arms open outward from the tool and are rotated, thereby cutting out a volume of the ocean floor within which the caisson may be positioned.