Located in the northern United States, a 50-year-old prill tower stands 268 feet tall with an inside shell  diameter of 52 feet and a 10 inch thick shell wall of reinforced concrete. There is also a spray head floor at an elevation of approximately 168 feet from grade. Due to the age of the structure and the naturally wet environment of a prill tower, repairs were needed to extend the service life of the tower and to protect the safety of their employees.

A condition assessment concluded freeze thaw conditions exposed aggregates and reduced the concrete coverage over the reinforcing steel on large  portions of the structure’s shell. The assessment also concluded that several steel components on the exterior   required removal and replacement.

PULLMAN was selected to perform the repairs due to the team’s expertise in specialty rigging and experience  working with heights. The scope included the removal and replacement of the exterior pond deck and  interior spray head floor, as well as concrete repairs throughout the shell.

After the concrete repairs were completed the liner panels and module frames were replaced, the spray head floor and pond deck were erected, and all service piping and electrical components were installed.

The project was completed over 7 months to return the tower to service. Because of working at heights on suspended access equipment that was engineered specifically for this  work, strict safety protocols were put in place. Some included engineered tie off points for personnel during   the movement of the suspended work deck, which was required for several phases of the work scope. Tools  were secured and tethered. Additionally, debris accumulation on the suspended work deck was maintained periodically on every working shift to control the loading to the work deck.