The Spiral Stairwell is 7 to 8 ft in diameter and sold in 10ft increments. it can also be used as a horizontal or sloping tunnel for underground structures that are far apart. The WASP Waist structure does not fail catastrophically and a triples axis seismic joint in molded into the structure. the stairwell has a standard rise and tread with a platform every 10ft of depth. The dome at ground level hydraulically raises and lowers and the tunnel transitions tothe standard elliptical tunnel at the bottom. The SS78 can be placed on a concrete pad or made with a dome base.