An example of a DDCV is one used by Exxon Oil in the Gulf of Mexico and includes a cylindrical hull, buoyed with air-filled compartments in the upper portion of the hull and ballasted with seawater and fixed ballasts in the bottom compartments. On top of the steel hull, the DDCV production facilities are designed to handle 100,000 barrels per day of crude, 325 million ft³/day of gas and produce up to 60,000 barrels/day of water. A three-level deck will house separation, dehydration and treatment facilities, as well as a drilling rig. Surface trees on the DDCV are similar to trees found on traditional platforms. All valves and flowlines are at the surface, located in the wellbay area of the DDCV. In this particular application, the trees have tensioned risers that connect the surface trees to the well at the seafloor. Surface trees allow for wellbore intervention, using conventional workover technology. The deep draft caisson vessel is moored via 12 anchor lines, which extend in a radial pattern from the hull. The mooring lines will be 7,100ft long and will connect to piles driven into the sea floor, approximately 6,900ft from the DDCV (at a lateral distance of about 5,100ft). The mooring lines are taut, but will have some flexibility and form a catenary between the hull and ocean floor. Each mooring line consists of chain (in the top and bottom sections) and spiral-strand wire rope (in the middle section)