Project Overview

• 99-foot diameter reinforced concrete tank
• 31-foot walls
• Built in 1974

The Fairfield-Suisun Sewer District (FSSD) Wastewater Treatment Plant serves over 135,000 residents in Solano County, California, providing wastewater treatment, recycling, and stormwater management. The plant’s digester tank was originally constructed with reinforced concrete and both the core wall and dome ring band are circumferentially prestressed using high-strength steel wire wrapped around the tank in a continuous helix. The mild steel and post-tensioning reinforcement had visible spalling and corrosion, raising safety concerns.

STRUCTURAL TECHNOLOGIES conducted a structural analysis to determine the best repair strategy. Due to access limitations and a sloping interior floor, traditional shoring methods were not feasible. The team designed temporary shoring utilizing external post-tensioning tendons that were installed on the ring beam before de-tensioning the existing tendons.

PULLMAN, an exclusive licensee of STRUCTURAL TECHNOLOGIES, executed the repairs. The scope of work included removal and installation of shotcrete as well as de-tensioning and installation of post-tensioning. The successful completion of this project enhanced the safety and reliability of this critical tank.