Siloam Springs Design-Build Water Treatment Plant

Project Summary

With an integrated, direct-hire approach, the City of Siloam Springs, Arkansas, undertook a major water system upgrade with confidence that it would be completed within the city’s fixed $31 million budget. The existing facility was last upgraded three decades ago and had a capacity of 9 million gallons per day (MGD). The city's population has more than doubled since that time and continues to rise by more than 1% each year.

The treatment plant’s pumps, clarifiers and other major equipment were reaching the end of their useful lives, and the reliability of the water supply was threatened by reliance on a single, 65-year-old raw waterline. The city set out to replace or rehabilitate its water treatment facility with the goal of meeting projected water demand for 2040.

Previous engineering assessments had assumed that any improvement project would include an expansion of the city’s treatment capacity and the likely construction of costly new treatment basins. We conducted a comprehensive analysis of those assumptions and found that increased demand created by population growth had been offset by more efficient water use and the loss of some industrial customers.

The plant’s existing capacity of 9 million gallons per day (MGD) would be adequate because while many plant assets would require retrofits or replacement, the concrete structures at the existing plant were generously sized and in good physical condition. New treatment basins would not be necessary, saving the city significant capital costs.

This allowed the city to recalibrate its expectations for the project’s size and scope. It also revealed an opportunity to build flexibility into the design so that the plant’s capacity could one day be expanded to 12 MGD without major changes to infrastructure.

The project was completed using a progressive design-build approach, the first time in city history. The construction schedule was set to maintain continuous operation of the plant, replacing key equipment during periods of lower demand.


  • Installed a 2.3-mile pipeline to back up the aging raw waterline.
  • Upgraded the disinfection system from chlorine gas to a safer and more effective hypochlorite alternative.
  • Replaced clarifiers, filters and pumps.
  • Implemented new modern instrumentation and control systems.


  • Planning
  • Design-build project delivery
  • Value engineering
  • Permitting assistance

City of Siloam Springs


Siloam Springs, Arkansas

Related Services

Design-Build for Water & Wastewater Infrastructure