North Tank Rehabilitation Project Completed

Civiltec completed the design for the rehabilitation of the North Tank for Azusa Light and Water back in September 2020. Construction of the project will be completed in February 2023. Terry Kerger, PE is very familiar with Sterl Tank recoating projects and has been managing the design and construction since July 2019. Our design team prepared a technical memorandum including rehabilitation options, life span evaluations, the feasibility of construction, and cost estimates of alternatives. Ultimately this technical memorandum was used by Azusa Light and Water to evaluate feasible options to rehabilitate the tank to extend its lifespan and continue to provide reliable storage for the water system.

The  North Tank is a 3.0-million-gallon steel tank 140 feet in diameter with a 30-foot high shell designed and constructed in the mid-1970s. Tanks built in this era typically have coal tar enamel interior coating systems and lead-based exterior coating systems. These tanks were not typically designed with flexible pipe connections(flex-tends). The maximum water depth to the overflow is 29 feet. American Water Works Association (AWWA) D-100 steel tank design guidelines and Occupational Safety and Health Administration (OSHA) requirements have been revised since1970. These new design standards require providing for sloshing wave containment, two access manways through the shell, a hatch over the overflow weir, safety railing systems on the roof, and climb and fall protection. The tank rehabilitation design included an upgraded exterior stair handrail that provides access to the roof. The project specifications included materials specifications and methods for removing the existing interior coating, applying new interior coatings, removing the existing exterior coatings, and applying a completely new exterior coating system. The design included retrofitting the piping connections to the tank with flexible pipe connections to mitigate damage to the tank during severe ground-shaking events.

The construction schedule was severely impacted due to coating material shortages, coating material manufacturing, and supply chain interruptions due to the COVID pandemic. These issues and some minor weather delays extended the project completion schedule by almost 6 months. The north tank rehabilitation was completed with a minimum of additional expense to ALW and now provides reliable dependable service to the residents of the City of Azusa.