When the Central Carbon Municipal Authority needed to build a new waste water treatment plant, they turned to VSL to provide an innovative approach that would maximize durability while minimizing maintenance. The project required an oxidation ditch, with three tanks of 1.97 million gallons each, and an aerobic digester, with three digester tanks of 112,700 gallons each and two sludge holding tanks at 154,400 gallons each.

The VSL team was responsible for furnishing the duct, anchorages and prestressing steel for slab-on-grade post-tensioning, horizontal and vertical wall post-tensioning and elevated slab post-tensioning. In addition, VSL installed rebar in the slab-on-grade, walls, concrete trough, baffle walls,elevated slab, and beams.

The ditches’ concrete floor and the digester’s concrete floor were designed and constructed to prevent uplift from groundwater pressure. The wall and ditch footings were designed to support the total anticipated live and dead load based on maximum allowable bearing pressure of 3,500 pounds per square foot. The floors and footings were placed on a 12-inch thick layer of ¾-inch quarry processed, compacted crushed stone.

Designed as post-tensioned concrete structures, the tanks featured internal vertical and horizontal post-tensioning in VSL’s PT Plus plastic duct. A minimum compressive stress of 250 psi was obtained using completely encapsulated grouted (bonded) tendons.