Charles City Water Treatment Plant Clearwell Tank

Challenge

Charles City, Iowa, had a trusted water treatment system, using aeration, lime softening, filtration, chlorination, pH adjustment, and corrosion control to consistently deliver safe, high-quality water to the community. The challenge arose after treatment.

With only a single 500,000-gallon ground storage tank, the facility did not have the capacity to support efficient operations. The lack of storage forced the system to cycle on and off, creating mechanical strain, inconsistent lime dosing, and reduced process control. These conditions increased maintenance demands, drove up operational costs, and introduced risks that could ultimately shorten equipment life.

For Charles City, the concern was not about producing clean water; it was about protecting the long-term reliability and sustainability of its treatment system.

Solution

To strengthen system performance and reliability, Charles City partnered with SEH to design and construct a new 1,000,000-gallon cast-in-place concrete ground storage tank at the water treatment plant. Combined with the existing tank, the plant’s on-site treated water storage increased to 1.5 million gallons, tripling its operational flexibility.

This added capacity immediately eased the burden on the system. With fewer start-stop cycles, equipment strain decreased, chemical dosing became more consistent, and lime usage was reduced. Operators gained improved process control, greater efficiency, and an extended lifespan for critical infrastructure. Before the tank went into service, it was thoroughly disinfected to protect public health and safety.

System Integration and Operational Control

Connecting the new and existing tanks required new yard piping and valves to ensure seamless operation. Isolation valves were also added, giving the City the ability to maintain or troubleshoot the system without requiring a complete shutdown. To further enhance reliability, a new level-monitoring system was introduced, providing real-time visibility into treated water storage levels. This allowed operators to respond more quickly to changes in demand and optimize lime feed control.

Site Work and Utility Relocation

Constructing the new tank required relocating existing water and sewer utilities that conflicted with the footprint. The team carefully sequenced this work to keep the plant operational and ensure uninterrupted service to the community. Once utilities were rerouted, the site was regraded, drainage systems adjusted, and the area restored, blending the new infrastructure into the existing plant layout while preserving accessibility for future operations and maintenance.

Investment in the Community

This project was made possible through strategic funding, including a $600,000 Community Development Block Grant (CDBG) and approximately $1.1 million in loan forgiveness. By addressing immediate system vulnerabilities and planning for long-term needs, Charles City invested not only in its infrastructure but also in the health, safety, and future of its residents. The community now benefits from a more resilient, efficient water treatment system that is fully prepared and designed to support continuous growth.