Wastewater valve replacement proves tricky

There is a tricky project currently taking place at the City of Yuma’s wastewater treatment plant, east of town.

Concrete Specialties is replacing a valve deep beside one of the two aeration basins. The valve was installed in 2005 when the treatment plant was built. It eventually stopped working recently, remaining open all the time.
Wastewater Supervisor Eric Metcalfe said that in itself is not so unusual.
However, what has made it a delicate project is the valve’s location. Metcalfe said it is 21 feet below ground, and is in a tight location between the aeration basin and what is called a “Return Activated Sludge” vault. The valve is part of an eight-inch transfer line for moving activated sludge.
The aeration basin had to be shut down, then Concrete Specialties excavated down to the valve, and built a safe working space to replace the valve.
“There are a lot of safety precautions,” Metcalfe said.
The new valve has been installed, and now the work crew is building a manhole to the valve, so it will be a lot safer if maintenance is required again sometime in the future.
The wastewater treatment plant has been able to serve the community as usual during the project, despite having one aeration basin temporarily out of commission. Metcalfe said the facility runs at 40-percent of its maximum volume, so the facility can get by on one basin in times like this. He said it is purposely designed that way just case one of the basins has to be shut down for maintenance.
The final project cost is estimated between $45,000 to $60,000.