of each leg 14 at the level of the deck 24 is a cabin like welding habitat 26 best shown in fig3 of larger diameter than the leg a vertical working tower 28 extends upwardly from the center of each welding habitat 26 in essence the structure 10 includes four composite towers 29 that extend from the ocean floor and reach more than 100 feet above the water surface each of these composite towers being formed by a leg 14 a welding habitat 26 and a working tower 28 all four towers 29 are joined just above the water level by the deck 24 each tubular section 30 of the pile 15 is typically about eighty feet long and six feet or more in diameter it is made of steel and has a wall thickness of about one to two and one half inches the piles 15 thus have the required flexibility to permit horizontal movement at their top ends the working towers 28 are cylindrical like the legs 14 and have a sufficient internal diameter to accommodate the pile sections 30 a vertical portion along one side of each working tower 28 forms a loading door 32 of a height at least equal to the length of one pile section 30 in its vertical or closed position the door 32 is secured to.