Mogollon Arsenic Removal Facility | 2022 WWD Top Projects

In a proactive measure, the Arizona Water Company constructed an arsenic removal facility for the Mogollon Well No. 5, the largest single source of groundwater production in the Overgaard Water System.

The 65-year-old Arizona Water Company operates 22 water systems for more than 30 communities. Among the assets it manages are five groundwater wells servicing more than 4,500 service connections, including Overgaard. Overgaard is located at an elevation of 6,600 feet near Navajo County’s Mogollon Rim.

GHD began Initial planning for the arsenic removal facility (ARF) in 2017 with the goals of maintaining 24/7 operation to arsenic concentrations below 7 parts per billion while withstanding climate challenges. Additional goals included ease of operations, flexibility and redundancy, and meeting budget on the desired construction timeline.

“The planning, engineering, and management executed by the project team supported the ability for the project to be commissioned safety and successfully, truly providing added value to our Overgaard water system and to our customers,” said Lee Hetrick, division manager for Arizona Water Company.

The project aimed to establish 24/7 arsenic removal for the Mogollon Well No. 5 to less than 7 parts per billion.

The ARF is a 1,320 square foot building, which includes a detention basin and improvements to off-site piping. It can treat 510 gallons per minute from the existing well with an additional 50 gallons per minute from water recovered through backwash processes. Equipment includes hydraulic, process, treatment, electrical distribution, and instrumentation and control systems.

The fit-for-purpose design resulted in optimization of materials choices as well as system design. GHD ensured the chosen equipment and materials could easily installed and operated within the constrained access area, and the team also designed a custom drainage system for stormwater to maintain historical runoff and outfall behavior.

“The GHD team worked seamlessly with our staff and was proactive to ensure the quality and value of the project from planning through commissioning,” Hetrick said.

The dual-vessel configuration allows for one unit to run on stnad-by while the other is on duty.

The facility uses a dual-vessel adsorption configuration — one on standby and one on-duty — and special consideration was taken to ensure the units had enough space around them to allow operators to add arsenic removal media and to inspect them when necessary. The selected units also allow for flexibility in adsorptive media used, a benefit that proactively solved supply chain challenges imposed by the COVID-19 pandemic.

“The GHD team worked seamlessly with our staff and was proactive to ensure the quality and value of the project from planning through commissioning,” Hetrick said.

The value engineering for the project stemmed from the automation design from GHD. The design team assessed hydraulic, mechanical, and electronic options for flow and level measurement components to provide the most effective automated experience for the operators after commissioning.

An example of the automation processes included the backwash processes, which occur every two to six months. By automating only the control valves for the backwash and recovery systems, preventative maintenance, repair and replacement concerns were minimized while also controlling capital and operational costs.

Special attention was paid to the spacing around the treatment equipment to ensure ease of use and inspection.

This was possible through collaboration and coordination with stakeholders of the project, including the operations and maintenance staff that work with the equipment day-to-day. Their insight into the pressure vessel design along with other configurations made the systems easier to use once the project was completed.

In the end, more than 4,500 service connection in the Overgaard system are protected with a reliable, resilient and robust arsenic removal facility for clean drinking water.

“This award exemplifies the way we do business. We are always looking to the future to solve problems before they disrupt our ability to take of our customers,” said Fred Schneider, president and COO for Arizona Water Company. “Our engineering team worked closely with our consultants and contractors and they all did an excellent job from start to finish. They earned this award.”