North Liberty, IA

Water Treatment Plant

  • Client City of North Liberty
  • Type Water
  • Services Process Design, Construction
  • Construction Cost $13.64 Million
  • Project Manager Steve Troyer, PE, BCEE
  • Project Engineer Matthew Hawes, PE


North Liberty’s Water Treatment Plant was originally constructed in the late 1970s and underwent its first expansion in 2001, a project that was expected to have a 10-year life. However, population growth exceeded optimistic projections and demand was quickly reaching capacity. Upgrades were made to increase well capacity and an Aquifer Storage and Recovery (ASR) well was constructed in 2009 which allowed the city to meet peak demands without increasing the capacity of the treatment facility.

However, the city’s population growth continued to exceed projections and the need to expand the treatment facility became necessary. In addition, the city had a goal of improving finished water quality and providing a higher level of softened water.

The treatment plant was in a residential neighborhood, so space for expanding was limited. As a result of their fast-growing population, the City needed a solution that would allow them to easily expand their treatment plant to meet future water demands while also minimizing the financial impact on current residents.


In 2013 FOX Engineering completed a facility plan that evaluated the condition of the existing water treatment facility and options for renovating or replacing the existing facility. After reviewing all viable alternatives, the recommendation was to abandon the existing water treatment facility and construct a new membrane filtration plant at a new site. The report also recommended constructing the new plant in phases so that excess treatment capacity was not constructed all at one time thus minimizing the financial impact on existing customers.

In 2014, an on-site pilot study was conducted to confirm that nanofiltration membranes were a viable treatment alternative; the study also determined the design requirements for a full-scale system treatment system. Shortly after, in August 2015, the design team led by FOX began working closing with city staff to design the Phase I Nanofiltration Water Treatment Plant which consisted of the new plant, chemical feed systems, high service pumping, and ground storage reservoir. The Phase I Plant capacity was based on a 10-year design to meet a peak day capacity of 3.0 MGD, or a population of approximately 28,940.

Nanofiltration membranes being prepared for installation in the membrane pressure vessels

Throughout the nearly 10-month long design process, the FOX team met regularly with city staff to review progress and solicit input to ensure the design met their expectations.  The need for easy expansion to accommodate population growth was always kept in mind. The plant was designed to include three nanofiltration skids meeting the Phase 1 design capacity with space allocated in the treatment building for two additional skids.  Additionally, the NF skids were specifically designed to be expanded in the future. Space was allocated for an additional high service pump and future chemical storage needs. This allows plant capacity to be nearly doubled without the need for expanding the physical size of the building.

The city received construction bids for the Water Treatment Plant in August 2016 with the low bid of $13.45 million being submitted by Portzen Construction. The Phase I Nanofiltration Water Treatment Plant was one portion of the $17.4 million Phase I Water System Improvements which included construction of new water supply wells and raw water mains. The low bid for raw water mains to connect the new and existing wells to the new water plant site was $1.09 million and was submitted by Ricklefs Excavating. The low bid for the new water supply wells was $2.88 million and was submitted by Gingerich Well.


The new Nanofiltration Treatment Plant is designed to allow the city to quickly and cost-effectively expand treatment capacity to meet the water demands of its quickly growing population. This allows the city to expand its treatment capacity as demands necessitate, the result being reduced financial impact on existing customers. The new treatment facility will provide the city with high quality, softened, drinking well into the future.

The new Nanofiltration Water Treatment Plant went into full operation in late May 2018.