Preload tank wall panels are precast on site, outside and around the circumference of the tank, and are shaped to the proper curvature of the tank radius. Where tight site conditions require it, the wall panels are precast on top of the finished floor or floor subgrade. By precasting on site, an unequaled level of quality control in the wall panel fabrication is obtained.

The panels are constructed in casting beds and are stack cast in an efficient assembly line type process. In fabricating each panel, the steel diaphragm is used as the bottom form. Side forms are positioned, vertical reinforcing and lifting inserts are placed, and the concrete is poured and finished to form the inside face.

The steel diaphragm is vertically ribbed with reentrant channels providing a mechanical keyway anchorage to the concrete. The individual sheets of the diaphragm are mechanically lock-seamed, producing an impervious watertight membrane throughout the entire wall area.

The combination of vertical reinforcement and the diaphragm help to counteract stresses due to differential temperature gradients and vertical bending moments. Inserts may be embedded to support internal tank accessories. Permanent manholes and through-the-wall piping, if selected, are accommodated by wall sleeve
penetrations made watertight by sealing them to the steel diaphragm.