Project Overview

Construction work was completed on four 4.2 million gallon capacity post-tensioned digesters – the DuraStor™ tanks were the centerpiece of a design-build project to incorporate the Cambi thermal hydrolysis process into an existing facility. Each tank is over 98 feet in diameter, with walls that are 74 feet in height.

STRUCTURAL TECHNOLOGIES provided the structural design of the prestressed digester walls and also provided VSL post-tensioning materials and installation. Bonded post-tensioning systems were utilized in the wall design to provide compression in the tank walls under maximum tank service loads and to eliminate all structural and thermal cracking in the walls from a high operating temperature gradient.

Careful planning and selection of the construction methods and materials took place during the design and pre-construction processes for the tanks. A number of innovative practices were incorporated such as the use of a jumping form system that allowed each tank to be built in four wall pours, or lifts, filling the full circumference to eliminate all vertical construction joints. Additionally, the digesters were constructed with self-consolidating concrete (SCC) to improve the overall quality of construction and provide the desired finish.

On completion of the project, the Blue Plains Advanced Wastewater Treatment Plant became the largest plant of its kind in the world.