As the first phase of Carson City’s waste water treatment plant rehabilitation nears completion, the next portion is well underway.
In June, the Board of Supervisors approved a $1.22 million contract with Keller Associates Inc., to design the $9.72 million second half of the project at the Water Resource Recovery Facility on 5th Street between Butti Way and Fairview Drive.
The next phase of the project will include covering the headworks where waste water enters the plant to reduce odors.
The first progress meeting between designers and the Public Works department staff is scheduled in two weeks, said Jim Morris, project manager for the city.
In September or October, the first phase should reach substantial completion, said Morris, meaning the new construction will be fully operational with just punch list items remaining.
“We’ll shut down the old aeration ponds and two old trickling filters,” said Morris, and power on the new bioreactors, the construction of which made up the biggest chunk of the $30 million first phase. “It will be a much more stable process.”
The initial phase came in a year ahead of schedule and under budget, allowing the city also to add on replacement of the screw pumps at the plant’s headworks.
Morris attributes the savings to the city’s use of a process called construction manager at risk, or CMAR, in which the project designer and builder are hired at the same time and collaborate before ground is broken.
It’s the city’s second project using the CMAR process, the first being construction of the Multi-Athletic Center.
The next phase isn’t using CMAR, instead going to the lowest responsible bid, but Morris said a lot was already learned from the initial work that can be used during the remainder of the project.
The next phase will take a year to design, which includes approvals from the supervisors at the point when design is 60 percent and 90 percent complete. Construction is scheduled to begin in June.
Construction should take a full 14 months, said Morris, with little room for time savings because the work is done sequentially.
The first stage is the headworks, where a design decision still has to be made between two types of processes to reduce odors.
The headworks will be covered and the odors diverted to one of two filtering methods: an earthen filter or tanks for chemical treatment.
Staff prefers the earthen filter, in which blowers push the odors into a mound of landscaped dirt where bacteria eat away at it, said Randall Gray, wastewater operations manager.
Gray said the process is used successfully at facilities in Dayton, Stead and Truckee, Calif., but may be initially more costly to install.
After that, the facility’s two primary clarifiers, in service for more than 40 years, will be drained, cleaned and put back in service, hopefully using the same equipment.
“The secondary clarifiers we know are in bad shape. We’re going to have to go in and replace the mechanisms,” said Morris. “We can’t clean them, we need to replace them.”
Some pavement will be repaved and the clay-lined emergency overflow pond, which holds up to 3 million gallons of wastewater, will be relined with a rubberized liner per state law.
The motorized controls will be replaced at the north lift pump station, where wastewater from northwest Carson City is pumped to the headworks, and at the effluent pump station, where the treated water is pumped to its golf course and prison farm users in the summer and to Brunswick Canyon Reservoir in the winter.
If any money is left over, it will go to replacing more of the electrical equipment throughout the plant, said Morris, work that needs to be done over the coming years.
All of the construction will be covered by the existing water and sewer rate increases, begun in 2013, which let the city bond for the entire project.
In the end, the goal is to reduce odors, produce higher quality effluent by removing more nutrients and improve plant reliability, all while maintaining or minimizing operational costs, said Gray.
“We’re replacing some very old technologies that were wonderful for their time,” said Gray. “But in those decades we’ve learned a lot about how to treat waste water.”