McMahon has played a key role in advancing critical water infrastructure improvements for the City of Marengo, Illinois. Delivering comprehensive planning and design services in support of the City’s grant-funded initiatives.

Located in McHenry County, the City of Marengo provides water supply, storage, and distribution services to more than 7,500 residential, institutional, and commercial users. In 2022, the City was awarded grant funding from the Illinois Department of Commerce and Economic Opportunity (DCEO) to support significant water and sewer infrastructure improvements. This was an unprecedented initiative for both the City and the DCEO due to its scale and accelerated timeline. 

To begin this effort, the City partnered with McMahon to evaluate its existing water supply, storage, and treatment systems. This evaluation identified the most cost-effective and efficient solutions. These proposed solutions would enhance service reliability, improve water quality, and accommodate future growth. 

Treatment and Project Process

One of the most visible outcomes of this initiative was the transformation of the City’s existing water booster pump station into a modern, centralized water treatment facility. Construction began in 2024 on the recommended improvements. This included a new deep sandstone well (Well No. 9) and water transmission main upgrades.

The newly converted treatment facility features two multi-cell horizontal pressure filters designed to remove iron, manganese, and radium from the water supply, significantly enhancing overall water quality for the community. These filters operate in conjunction with Hydrous Manganese Oxide (HMO) and sodium hypochlorite chemical feed systems. This treats water from multiple wells before it enters the filtration process. 

Within the treatment plant, water from Wells No. 6, 7, 8, and 9 combines upstream of the filters, where treatment chemicals can be applied prior to filtration. Each filter contains specialized Greensand Plus media that removes contaminants before the treated water is discharged into a one-million-gallon storage reservoir. Final chemical additions including sodium hypochlorite, polyphosphate, and fluoride, ensure water quality and stability throughout the distribution system. 

To maintain operational efficiency, the treatment system includes an automated backwash process that cleans each filter cell individually, allowing continuous operation without service interruption. Backwash water is collected and safely discharged to the sanitary sewer system. 

Together, these improvements represent a significant investment in the City of Marengo’s future. The upgraded system provides enhanced water quality, increased redundancy, and added capacity to support continued community growth. For more information on this water improvement project for the City of Marengo, click here.